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Abstract With soft-touch, lightweight, excellent temperature resistance and insulating performance, aramid mica paper is widely used in special motors 'transformers and other electrical equipments. In this paper, aramid mica paper was prepared by using white mica, meta-aramid chopped fiber and meta-aramid fibrid as skeleton and bonding components respectively. The effects of aramid fibers ratio, dispersant dosage, mica content and mica particle size on mechanical properties, insulating properties, micro-structure and temperature resistance of paper were studied. The results showed that the optimal process parameters were as follows: the mass ratio of fibrid to chopped fiber was 7:3 the amount of PEO was 0.5wt%, the mass fraction of mica was 50 wt%, and the size of mica was 120~150μm. [ABSTRACT FROM AUTHOR]

Natural cellulose paper is hygroscopic and has weak mechanical properties,which limit its potential applications in paper-based electronics.In order to solve these problems,we successfully develop a new kind of paper-based composites for paper-based strain sensors fabrication by infiltrating polyester vitrimer into porous cellulose paper via physical coating.Experimental results show that the resultant paper composite not only has excellent mechanical properties(tensile strength is up to 72 MPa) but also show excellent water resistance.In addition,the paper-based strain sensor made from the resultant composite has high sensitivity(GF=43),fast response time(0.19 s),good durability(3 000 cycles of stretching),showing promising applications in wearable devices for human motion monitoring. [ABSTRACT FROM AUTHOR]

The electro-acoustic (frequency response) characteristics of the loudspeaker usually be affected by the mechanical properties of the paper diaphragm. The mechanical properties of the diaphragm were improved by modifying the natural fiber. In this work, the structure of Manila hemp fiber and the mechanical properties, electro-acoustic performance of paper diaphragm were discussed on the effects of alkali concentration and treatment time. The surface morphology, crystal structure and chemical composition of Manila hemp fiber treated before and after were characterized by SEM, XRD, FT-IR, TGA. The results showed that the fiber surface roughness increased, and the crystallinity of the fiber increased and then decreased as the alkali concentration or the treatment time increased. The lignin and hemicellulose on the fiber surface were decreased. The thermo-stability of cellulose improved the same time lignin’s decreased. When the alkali concentration was too large or the treatment time was too long, the cellulose will be degraded, the mechanical strength of the diaphragm was affected. The fiber diaphragm has the best mechanical properties and electro-acoustic performance with 5 wt% of the alkali concentration, 3 h of the treatment time. [ABSTRACT FROM AUTHOR]

Carbon fiber and its composites are widely used as structural materials due to their excellent mechanical properties. However, the chemical inertness of carbon fibers restricts their further application. In this paper, we implemented that the modification of carbon fiber via coating aramid nanofibers based on pre-treatment of carbon fiber surface by dopamine. At the same time, the effects of modified fibers on the properties of paper-based materials were investigated. It was found that pre-treatment of carbon fiber contributed to the cationization of the surface of carbon fiber, and further assisted the coating of aramid nanofiber by electrostatic adsorption. The surface morphology, chemical composition, hydrophilic property and mechanical properties of carbon fiber paper-based material were characterized by scanning electron microscopy(SEM), fourier transform infrared spectroscopy(FTIR), contact angle tester and tension tester. The results showed that the best coating effect on carbon fiber was achieved when the concentration of aramid nanofiber is 0.2% the best deposition effect when the 0.2% concentration of nano aramid fiber. The carbon fiber paper-based material modified by aramid nanofiber has good hydrophobic properties(CA=112.4°C) and mechanical properties(6.74 MPa). [ABSTRACT FROM AUTHOR]

Due to the layer characteristics and anisotropic mechanical properties of 3D printed concrete, there is still lacking effective numerical simulation method for force analysis of 3D printed concrete. In this paper, the linear elastic constitutive parameters of 3D printed concrete anisotropic equivalent elements are deduced, based on the deformation conditions and mechanical equilibrium conditions, and based on the shear stress reciprocity theorem, the layer stress calculation method of 3D printed concrete is given. A 100 mm×100 mm×100 mm 3D printed concrete cubic block is taken as an example. The ANSYS finite element software is carried out to simulate the force performance of 3D printed concrete. The results show that the number of elements obtained by the equivalent element method is reduced by 64 times, the overall error of the displacement results can be controlled within 1%, and the calculation efficiency is increased by more than 430 times. Through the research in this paper, the finite element simulation analysis of anisotropic 3D printed concrete with layer characteristics is realized, which can greatly improve the calculation efficiency under the premise of ensuring the calculation accuracy. [ABSTRACT FROM AUTHOR]

As a preparation material for important components such as conductive springs and interconnect connectors, the large scale industrial preparation method and heat treatment process of Cu Ti alloy are still the key areas that urgently need to be developed and promoted in the current copper alloy field. In the present paper, Cu Ti alloys with Ti content of 1%, 4. 5 % and 10% were prepared by aluminothermic reaction, which has the advantages of simple process, environmental protection, energy saving and low cost, and the comprehensive properties of the alloys were further regulated by solid solution and aging treatment. The results show that the Ti elements in the aged Cu l%Ti and Cu 4.5%Ti alloys are mainly in the state of solid solution with only a small amount of smaller precipitates, while there are a large amount of precipitates in the aged Cu 10% Ti alloys. With the increase of Ti content, the electrical conductivity of the alloys shows a significant decrease trend, while the hardness and strength show the opposite trend. For the alloys with the same composition, compared to the solid solution state, the conductivity first slightly decreases and then increases with aging time. After aging at 450 °C for 4 h, the conductivity of all three component alloys is higher than that of the solid solution state alloys* After aging at 450 °C for 2 h, the hardness, strength and elongation of Cu l%Ti and Cu 4. 5%Ti alloys obtain the maximum values, and the hardness and elongation of Cu 10 % Ti alloys also obtain the maximum values, while the yield and the tensile strength of Cu 10%Ti alloys show slightly decreasing trend with aging time. [ABSTRACT FROM AUTHOR]

Silk fibroin shows biocompatibility, biodegradability, and a lack of immunogenicity and allergenicity, possessing great potential in biomedical applications. In various forms of silk fibroin biomaterials, silk fibroin films are attracting increasing attention due to their easy processing. Among the physic-chemical properties of silk fibroin films, mechanical properties have great impact on their subsequent applications in vitro and in vivo. First, this paper briefly discussed the relationship between the hierarchical structures and mechanical properties of silk fibroin. Then, it summarized the influence of preparation parameters on mechanical properties, and the influence of different treatments on microstructure of silk films and the resulting changes in mechanical properties. Moreover, it discussed the relationship between structural changes and mechanical properties of silk fibroin films. Finally, it looked to the future to provide reference for the development of silk fibroin films to meet a variety of needs.The mechanical properties of silk fibroin materials are structure dependent. Silk fibroin materials have five levels of hierarchical structures, in which the content of β-sheet in the secondary structure, the size and content of β-crystallites in the tertiary structure, and the density and orientation of β-crystallites in the quaternary structure are all critical parameters to the mechanical properties. The multi-level structure of silk fibroin can progressively influence the macroscopic mechanical properties step by step. In the aggregated state, it is generally accepted that the strength and stiffness of the silk fibroin material are determined by Silk II while ductility and flexibility are controlled by Silk I.The rational design and reconstruction of silk fibroin structure can be implemented by controlling the preparation process. Pure silk fibroin films can be prepared in three steps: solution fabrication, film formation and post-treatment. Solution fabrication consists of degumming and silk fibroin dissolution, which will reduce the molecular weight of silk fibroin and therefore weaken the mechanical properties. As for film formation, solution casting or spin coating is often used to produce dense, porous, and lamellar films. The mechanical property of silk fibroin films fabricated via solution casting is controlled by controlling the drying rate, while films fabricated via spin-on method are limited by thickness. The pore size, pore density and pore distribution are important to mechanical properties for porous films, while the mechanical properties of lamellar films are related to the interlayer bond compactness. Post-treatments, such as organic solution immersion, water vapor annealing, external forces, and relative humidity in storage, can improve mechanical properties by changing crystallinity and orientation.Additive modification is an effective way to improve the mechanical properties of silk fibroin films. Blending, plasticizing, and crosslinking are common additive modification methods. Mechanical properties are changed by forming specific intermolecular interactions between silk fibroin and additives. The interactions between blends and silk fibroin can be roughly divided into phase separation, strong interaction, and network formation. Among them, network formation needs an appropriate mixing ratio to form an excellent balance interaction. Crosslinkers form covalent links between molecules and increase the molecular weight. In this way, physical crosslinking and chemical crosslinking need to be balanced. Plasticizing can improve the flexibility and ductility of silk fibroin films. The commonly used plasticizers are glycerin, water, and Ca2+, and the combination of other additives gives silk fibroin films excellent comprehensive mechanical properties. All in all, the hierarchical structures and the mechanic-structure dependence of silk fibroin materials make silk fibroin films adaptive to meet the applications requiring different mechanical properties. In the future, it is necessary to continue to expand the preparation methods of silk fibroin, and have an in-depth knowledge of the relationship between the structure and properties of silk fibroin, so as to accurately regulate the mechanical properties of silk fibroin films and further study the relationship between mechanical properties and other relevant properties. Mechanical property modification, functionalization and biocompatibility need to be considered together in the application studies of silk fibroin materials, so as to further expand the application range of silk fibroin materials. [ABSTRACT FROM AUTHOR]

Pearlite is a very important microstructure. Therefore, a model of the ferrite - cementite phase inter- face is constructed in this paper, and the process of nano - intrusion is simulated by molecular dynamics simulation method. By analyzing the mechanical properties and microstructure of the simulation results, the ferrite - ce- mentite phase interface effect was explored. It is found that the indenter load increases with the increase of the distance between the indenter and the grain boundary at different distances (positions of indentation) from the ferrite cementite grain boundary. When the indentation depth reaches a certain depth, the load decreases with the increasing distance. Young's modulus and maximum shear modulus are directly affected by the atomic structure below the indenter tip, and hardness is affected by both the structural integrity and type. The cementite phase interface affects the nucleation, proliferation and expansion of dislocations during the nano indentation process, and the macroscopic performance is the difference of the indenter load at different indentation positions under the same indentation depth. [ABSTRACT FROM AUTHOR]

V-5Cr-5Ti alloy is one of the main candidate structural materials for the first cladding of nuclear fusion reactor, but the theoretical research is relatively few on its mechanical properties. In this paper, the elastic constants, bulk modulus, shear modulus, Young's modulus, Poisson's ratio and Cauchy pressure of V-5Cr –5Ti alloy are calculated by using the random solid solution model and the first -principle method, and com- pared with the calculated correlation values of pure vanadium. The results show that V-5Cr-5Ti alloy has good plasticity and strength, but its plasticity is slightly lower than that of pure vanadium. The results show that the plasticity and strength of V-5Cr-5Ti alloy are reduced in varying degrees due to the addition of oxygen atom. Finally, the theoretical strengths of V –5Cr-5Ti alloy and pure vanadium are calculated, and the stress -strain diagrams of them are drawn. The above conclusion is verified again by comparison. [ABSTRACT FROM AUTHOR]

The research and development of high-strength and high-toughness metal coordination hydrogels (MC-HG) for flexible electronic sensing has become an international frontier in the field of advanced functional polymer materials, which has wide application significance and important scientific value. However, the traditional soaking method is difficult to control the permeation and combination of metal ions, resulting in weak mechanical properties. In this paper, a screening strategy based on sodium acetate (SA) was proposed to promote the metal complex permeation first and then combination with functional ligands, thus obtaining a homogeneous metal coordination hydrogel (Fe-HGSA), whose breaking strength and toughness (1. 546 MPa/2. 139 MJ/m³) were much higher than those of traditional soaking method (0. 832 MPa/0. 919 MJ/m³) and common aqueous solution rearrangement method (1. 126 MPa/1. 352 MJ/m³). Due to its excellent mechanical properties and good electrical conductivity, Fe-HGSA has potential applications in the field of flexible force sensors. [ABSTRACT FROM AUTHOR]

Molten metal die forging (MMDF) processes is an advanced process for high-performance forming of aluminum alloy parts, MMDF technology is applied to the forming of closed subframes, fo- cusing on the performance uniformity of MMDF process scheme and MMDF subframe in this paper. Simulation studies show that single-runner MMDF has fewer confluence positions, higher surface quality and higher process yield than MMDF solutions with auxiliary runners. Trial production proves that the single runner liquid forging of A356. 2 aluminum alloy subframe can be obtained by using the HVSC2500T horizontal MMDF machine designed and manufactured by Guangzhou Hede, and the sampling tensile strength of the body can reach 320 MPa while the elongation is 11. 12%. However, slag inclusion defects are prevalent in locations away from the sprue and where there is a confluence, and the strength and plasticity are low. [ABSTRACT FROM AUTHOR]

As a natural protein fiber with good biocompatibility, silk has a lot of wastes in production, processing, weaving and after-use. Based on the principle of sustainable development, silk fibroin protein can be recycled by chemical method. After recycling, silk fibroin solution can be obtained and recycled silk fibroin materials can beprepared for reuse. Wet spinning is the first to be developed and applied in industrial production because of its uniqueness. As the process has been optimized in industrial production for a long time, wet spinning has become a relatively mature spinning method in all aspects. The choice of coagulating bath plays a key role in the solidification of spinning fluid in the coagulating basin, especially in the mechanical properties of RSF fibers. Sodium dodecyl sulfate (SDS) is a typical anionic surfactant with good emulsification performance, low skin irritation, high safety, and can interact with protein. Based on this, the study intends to establish a wet spinning process using SDS as the solidifying agent. In the paper, SDS was used as the coagulation bath to improve the ductility of regenerated silk fibroin fibers. First of all, the silk was degummed through degumming and other pretreatment, and then the degummed silk obtained after drying was dried for later use. After that, the degummed silk was dissolved with the formic acid-calcium chloride solution to obtain the spinning stock solution. In this way, deionized water, 75% ethanol solution and 50g/LSDS solution were selected as the coagulation bath for wet spinning, and three kinds of RSF fibers were obtained. In the end, the mechanical properties and aggregation structure of three RSF fibers were analyzed. Subsequently, the mechanism of SDS promoting fibrogenesis was verified by the fluorescence probe method. The morphology of the three kinds of RSF fibers was characterized by scanning electron microscope. Deionized water was used as the coagulation bath to obtain the most surface folds and the largest diameter of recycled silk. The recycled silk with ethanol as the coagulation bath has a roughly round cross section, smooth surface and the smallest diameter. When SDS is used as the coagulation bath, the cross section of fiber is approximately elliptic, with a few furrows on the surface and moderate thickness. Tensile tests were conducted to the three kinds of RSF fiber samples. The results show that when SDS is used as the coagulation bath, RSF shows the characteristics of elastic materials, and its fracture strain is 126%, which is much higher than that of the two kinds of regenerated fibers using deionized water (20%) and 75% ethanol solution (26%) as the coagulation bath. In order to explore the effect of the coagulation bath on the aggregation state of recycled silk, Fourier transform infrared spectroscopy (FTIR) was first used to analyze the secondary structure. The contents of three RSF secondary structures were obtained by the peak separation of amide Ⅰ region, and specifically, the recycled silk with SDS as the coagulation bath had the highest β-folding content. The content of β-folding of recycled silk in the coagulating bath with 75% ethanol was the lowest. In order to further explain the relationship between the mechanical properties and protein structure, X-ray diffraction was used to characterize the crystallization of the three kinds of RSF fibers, and it can be seen that the crystallinity degrees of the regenerated fibers are all low. In order to further explain the relationship between β-folding and the crystallization region, differential scanning calorimetry analysis was carried out for the three kinds of RSF, which confirmed the presence of β-folding in large quantities in RSF(SDS) fiber samples. The effect of SDS on silk fibroin protein was characterized by fluorescence probe. The results show that the surface of silk fibroin protein can produce more β-folds at the same time in the presence of SDS. In this study, SDS was used as the coagulating bath for wet spinning, anionic surfactant was innovatively introduced as the composition of coagulating bath, and a recycled silk material with high extensibility was obtained, providing a new research idea for silk fibroin protein wet spinning. In this paper, only the influence of the coagulation bath on the properties of recycled silk has been investigated, and the influence of post-treatment on the properties of recycled silk has not been involved. RSF(SDS) fibers, with excellent fracture elongation, can be treated to further improve the properties of recycled silk fibers. [ABSTRACT FROM AUTHOR]

【Objective】The present paper aimed to clarify the effects of different degradation films on the growth of pumpkin and the characteristics of the changes in the degradation performance and mechanical properties of the films.【Method】We investigated the trends of mechanical indexes such as film elongation and breaking force values of black PE film (CK), white degradable film (T1), black degradable film (T2) and black carbon dioxide-based degradable film (T3) and their effects on the growth of pumpkin plants during the reproductive period of pumpkin through the field mulching test.【Result】With the increase of coating time, it was found that the mechanical properties of different membranes showed a decreasing trend through the mechanical properties testing and degradation degree analysis during the important fertility period, and the values of the mechanical indexes of the three degradable membranes showed the most obvious decreasing magnitude. Among them, the initial values of all mechanical indexes of T1 treated membranes were higher than those of T2 and T3, and the degradation degree was weaker than that of T2 and T3 during the reproductive period of pumpkin; the values of all mechanical characteristics of T2 and T3 were relatively similar, and the degradation degree of the membranes was of the same grade. Through correlation analysis, it was concluded that the mechanical characteristics of the degraded film were negatively correlated with the degree of degradation, and the degree of degradation increased with the decrease of the mechanical characteristic values; the SPAD value, chlorophyll a and b contents of the leaves of CK mulching treated plants were higher than those of the three degraded films, and they had stronger photosynthetic capacity, so the growth and development in the number of leaves, area and length of the vine showed better performance. Black degradation film (T2) and black carbon dioxide-based degradation film (T3) treated pumpkins had increased soluble solids and Vc contents, which had an enhancement effect on the overall quality of pumpkin, and the pumpkin yields of the two converged and were not significantly different from those of CK. 【Conclusion】 Degradation of the mechanical properties of the degradable film will accelerate the rate of degradation and affect the performance of film-assisted production, covering the black degradable film and black carbon dioxide-based degradable film can be made to improve the quality of pumpkin quality, and pumpkin yield is not significantly different from the covering of black PE film. In view of the environmentally friendly nature of degradable films in agricultural production, it is feasible to replace ordinary PE films in crop and vegetable production. [ABSTRACT FROM AUTHOR]

In order to improve the stability of the cemented filling body in Songxian Shanjin, this paper conducted compressive strength tests on cemented filling bodies under different types and contents of glass fiber, basalt fiber, and polypropylene fiber, and compared the influence of fibers on the compressive strength and failure morphology of the cemented filling body. The experimental results show that polypropylene fiber has the most significant improvement effect on the macroscopic strength of the cemented filling body, followed by basalt fiber and glass fiber, under different fiber content conditions, the compressive strength of the cemented filling body shows a trend of increase at first and then decrease. When the fiber volume content is 0.2 %, the compressive strength of the cemented filling body is the highest. In addition, the addition of fibers has a more significant improvement in the compressive strength of cemented filling body with lower ash-sand ratios. The influence of fiber content on the cemented filling body at different curing ages is greater than that of fiber types. In the compressive strength test, the cemented filling body without added fibers experienced spalling and crack penetration during failure, while the cemented filling body with added fibers experienced coarse and long cracks during failure, with more fine cracks generated. [ABSTRACT FROM AUTHOR]

Relining and modilying A356 alloy is one ol the important ways to improve its mechanical properties. In this paper, A356 alloy melt was treated with a new Al-Ti-La refiner and Al-10Sr modifier, and the ellect ol holding time on the microstructure and mechanical properties ol as-cast A356 alloy was studied. The results show that when the holding time is 15 min and the A356 alloy is treated with Al-Ti-La reliner and Al-lOSr modifier, the secondary dendrite arm spacing ol a-Al in the as-cast A356 alloy is reduced from 31. 10 pm to 15. 56 pm, which is reduced by 49. 96%, and the eutectic Si morphology is changed Irom coarse needle Hake to line short rod and granular. With the improvement ol cr Al and eutectic Si phase morphology, the tensile strength ol as-cast A356 alloy increased Irom 169. 67 MPa to 216. 33 MPa, increased by 27. 50%, the elongation increased Irom 4. 47 % to 10. 53 %, increased by 135. 57%, and the Vickers hardness ol the alloy also increased Irom 56. 37 HV to 62. 03 HV, increased by 10. 04%. The fracture mode changes from trans granular fracture to intergranular fracture, and the plasticity and toughness ol the alloy are obviously improved. [ABSTRACT FROM AUTHOR]

8011 aluminum alloy is a widely used cast rolling aluminum alloy. The solid liquid ratio and Al-Ti-B addition amount in the melting process are key factors affecting its properties. In this paper, the effects of solid liquid ratio(25%,30%,35%,40%) and Al-Ti-B master alloy addition(0. 18%,0. 20%,0. 22%) on the microstructure and mechanical properties of 8011 aluminum alloy were studied via optical microscope (OM), transmission electron microscope(TKM) and mechanical property tests. The results show that the higher the addition of Al-Ti-B master alloy, the finer and more uniform the grain size distribution of 8011 aluminum alloy at the same solid-liquid ratio; At the same addition amount of Al-Ti-B master alloy, the higher the solid-liquid ratio is, the smaller the grain size of 8011 aluminum alloy is, but it is easy to lead to grain agglomeration; When the solid-liquid ratio is 40% and the addition amount of Al-Ti-B master alloy is 0. 22%,8011 aluminum alloy has the best grain refinement effect and mechanical properties. Its tensile strength can reach 107 MPa, elongation can reach 12. 4%,and hardness is 36. 73 HV. [ABSTRACT FROM AUTHOR]

Aerogel materials have broad application prospects in the market of building thermal insulation materials because of their high porosity, strong compression resistance and low thermal conductivity. In this paper, Al2O3-SiO2 aerogel composite thermal insulation materials with different SiO2 content were prepared by sol-gel method using tetraethyl orthosilicate and sec butanol aluminum as raw materials. The effects of SiO2 doping amount on the crystal structure, micro morphology, mechanical properties and thermal conductivity of composite aerogels were studied. The results showed that Al2O3-SiO2 aerogel was mainly composed of polycrystalline boehmite. SiO2 doping inhibited the formation of γ-Al2O3 phase and hindered the occurrence of hydroxyl condensation reaction. H in AlO—H group was replaced by Si, forming a more stable Al—O—Si bond. Al2O3-SiO2 aerogel showed an open porous structure, and the doping of SiO2 improved the pore orientation of the aerogel, reducing the pore size and distributing evenly. With the increase of SiO2 doping, the compressive strength and specific surface area of Al2O3-SiO2 aerogel first increased and then slightly decreased, and the thermal conductivity first decreased and then increased. When the doping amount of SiO2 was 9 mol %, the maximum compressive strength of the aerogel was 40.92 MPa, which was 58.97% higher than that of the undoped aerogel. The maximum specific surface area was 257.33 m²/g, the lowest thermal conductivity was 0.022 W/（m·K）, and the thermal insulation performance was the best. In summary, the optimal doping amount of SiO2 was 9 mol%. [ABSTRACT FROM AUTHOR]

Void is a common defect in the preparation of FeCrNiCoCu high - entropy alloy. Thus, this paper employs molecular dynamic simulation to build FeCrNiCoCu models with void for uniaxial tension simulation, and explores the effect of the voids location, void radius and deformation temperature on the mechanical properties. It is found that the void in the crystal with the Z -axis orientation of [111] and at the grain-boundary(GB) will seriously reduce the yield strain and yield stress, but have little effect on the Young's modulus of the model. With the increase of the void radius at the grain boundary, in the elastic stage, the increase of the void radius increases the area of stress concentration, which is conducive to dislocation nucleation, and the mechanical proper- ties of the model decrease accordingly. In the plastic deformation stage, with the increase of the void radius, the initial dislocations tend to expand to the crystal with the Z axis orientation of [001]. The model maintains good mechanical properties at medium and low temperatures; at high temperature, the mechanical properties decrease significantly. In the high temperature plastic deformation stage, the total length of dislocation in the model is low, and the average flow stress is also low. [ABSTRACT FROM AUTHOR]

Aiming at the problems of insufficient flexural strength and low durability of cement concrete, this paper prepared concrete with different content of epoxy resin（0%, 3 wt%, 6 wt%, 9 wt%） by using epoxy resin as doping phase, and analyzed the influence of epoxy resin on the mechanical properties, micro appearance and durability of cement concrete. The results show that the doping of epoxy resin accelerates the hydration reaction, reduces the number of cracks and pores, and improves the density of concrete. The compressive strength and flexural strength both increased first and then decreased with the increase of resin doping. The compressive strength and flexural strength of the concrete with 6 wt% epoxy resin doping reached the maximum values of 43.8 and 7.9 Mpa respectively when cured for 28 d, which increased by 18.70% and 29.51% respectively compared with the concrete without resin doping. The chloride ion diffusion coefficient of concrete decreases first and then increases with the increase of resin doping amount. The chloride ion diffusion coefficient of concrete with 6 wt% epoxy resin doping content for 28 d is the lowest of 7.7×10-8 cm/s, and the chloride ion corrosion resistance is the best. When the number of freeze-thaw cycles reaches 80, the concrete with 6 wt% epoxy resin doping has the lowest mass loss rate of-0.13%, the highest relative dynamic elastic modulus of 94.86%, the lowest wear amount of 0.66 kg/m², and the wear amount reduction rate of 46.77%. It has excellent durability. [ABSTRACT FROM AUTHOR]

In order to study the road performance of rubber-asphalt mixture with different rubber powder content, in this paper, by adding different quality rubber powder to 70#A grade base asphalt, the asphalt PG grade and the adhesion characteristics between asphalt binder and aggregate were analyzed by asphalt laser rebound test and asphalt contact angle test, determine the optimal rubber powder content of the upper, middle and lower layers of the rubber asphalt pavement structure (30% SMA-13 for the upper layer; 40% for the middle layer AC-20 and 50% for the lower layer AC-25); Through the research on the mechanical properties of the rubber-asphalt mixture with different rubber powder contents, such as the Hamburg rutting test, the low-temperature bending crack resistance test and the direct shear test, the following results are obtained: The addition of rubber powder can enhance the cohesion between the asphalt binder and aggregate, make the plastic deformation ability of the asphalt mixture stronger, effectively improve the water stability and high temperature rutting resistance of different structural layers of rubber-asphalt mixture, improve the crack resistance and fatigue resistance of rubber-asphalt mixture. Combined with engineering examples, borrowing the three-dimensional radar detection system, the internal conditions of the road, such as the integrity of the paving of the rubber mixture asphalt pavement structure layer and the uniformity of the material thickness, were evaluated; Through the on-site road coring and CT scanning, the three-dimensional spatial distribution of aggregates and pores of the on-site pavement structure was obtained, the addition of rubber powder can promote the molecular movement between asphalt binder and aggregate, effectively improve the pore distribution of asphalt mixture, make the material inside the pavement more evenly distributed, give full play to the excellent road performance of rubber asphalt pavement. [ABSTRACT FROM AUTHOR]

In this paper, modified cementitious powders with different doping amounts of calcium carbide slag (0,0.5 wt%,1.0 wt% and 1.5 wt%) were prepared with 32.5 grade ordinary portland cement, II grade fly ash and mirabilite as raw materials and industrial waste calcium carbide slag as additive materials. The effects of calcium carbide slag doping on the crystal structure, micro morphology, mechanical properties, setting time and combined water content of modified cementitious powder were analyzed.The results show that the doping of carbide slag doesn’t produce new products, but accelerates the consumption of C2S and C3S and improves the rate of hydration reaction.When the doping amount of carbide slag is 1.0 wt%, the hydration products are most closely combined.With the increase of calcium carbide slag doping, the setting time of the modified cementitious powder gradually decreases, and the compressive strength and chemical binding water content at 28 d first increase and then decrease.When the doping amount of carbide slag is 1.0 wt%, the compressive strength and chemical binding water content at 28 d reach the maximum, which are 2.98 MPa and 6.8% respectively.This is because the addition of appropriate amount of calcium carbide slag accelerates the hydration reaction of cementitious powder, increases its structural compactness, and improves the mechanical properties of cementitious powder.It can be seen that the optimum doping amount of carbide slag is 1.0 wt%. [ABSTRACT FROM AUTHOR]

In order to improve the bonding effect between carbon fiber and aluminum matrix, the effect of ZrO2 coating thickness on the mechanical properties of continuous carbon fiber reinforced aluminum matrix composites was investigated in this paper. ZrO2 coatings with different thickness were prepared on the surface of carbon fibers by sol-gel method. Continuous carbon fiber reinforced aluminum matrix composite strips were prepared by a twin-roll casting process. The microstructure of carbon fibers with different coating thickness and the interface and fracture characteristics of the composites were studied, and The tensile mechanical properties of the composite plates were tested. The experimental results show that the uniform ZrO2 coating can be obtained on the surface of carbon fiber immersed in the prepared sol for 20 min; When the rolling speed is 2.6 m/min, the roll spacing is 2 mm and the pouring temperature of molten aluminum is 950 K, the properties of the composites are the best, and the tensile strength is increased by 72.5%. [ABSTRACT FROM AUTHOR]

Al-based particle-reinforced composites have become the focus research around the world due to their unique quality, economic and performance advantages. Powder metallurgy method has the advantages of flexible selection of reinforced particles, accurate and controllable content, and strong designability, which is one of the commonly used methods for preparing particle reinforced Al matrix composites and is favored by many scholars. The present paper firstly gives a brief introduction to the development of Al matrix composites. Secondly, the densification molding technology and sintering process in powder metallurgy process are summarized. Subsequently, the composition design, such as reinforcement type, content, particle size, distribution, etc., interface wettability and its control, the relationship between microstructure characteristics and mechanical properties, and the strengthening mechanism were mainly discussed. Finally, it analyses the problems and challenges faced by powder metallurgical particle-reinforced Al matrix composites and looks forward to their development. [ABSTRACT FROM AUTHOR]

So as to investigate the influence of intercritical annealing time on microstructure and mechanical properties of medium Mn steels based on the results of SEM, XRD and tensile properties, a Fe-0.21C-0.20Si-6.1Mn-0.97Al alloy was treated at different annealing times（10min,1hand 12h）in this papers. The results showed that the increase in annealing times from 10min to 1hled to the increase in mechanical properties of warm rolled medium Mn steels,as the annealing time further increased to 12h, the mechanical properties of the experimental steel decreased; the increase in annealing time led to the increase in average grain size and the equiaxed microstructure ratio; with the increase of annealing time from 10min to 12h, the retained austenite fraction and stability increased firstly, and then decreased. Based on the above results, it can be inferred that the microstructure and mechanical properties of medium Mn steel could be controlled by controlling the annealing time. [ABSTRACT FROM AUTHOR]

As the Ecological Protection and High-Quality Development of the Yellow River Basin has become a national strategy, the resources attributes and value of the Yellow River sediment have become increasingly prominent. This paper discussed the feasibility of using the Yellow River silt in Kaifeng section as concrete fine aggregate. Through experiments, 12 sets of concrete mixing ratios were designed, and the mixing ratio of the Yellow River silt and machine-made sand was studied, and the fly ash cement replacement rate affected the performance of concrete and the influence of mechanical properties. The compatibility of the Yellow River sediment and fly ash was analyzed under the selected maximum replacement ratio of the Yellow River sediment. The test results show that the compressive strength of the 28 days concrete test block is 5% higher than that of ordinary concrete when the ratio of the Yellow River sediment to the machine-made sand is 10%; the optimal replacement re-do of the Yellow River sediment is 20%, the concrete strength can reach 41.3 MPa, the slump is 190 mm, and the expansion degree is 480 mm. Compared with ordinary concrete, the performance is basically the same; under the working condition that the maximum replacement ratio of the Yellow River sediment is 30%, the compatibility of the Yellow River sediment and pulverized coal ash in concrete is good. [ABSTRACT FROM AUTHOR]

In order to improve the deformation energy dissipation and self centering capacity of concrete frame joint an improved design method of beam column joint with super elastic SMA bar and steel end plate was proposed to improve the capacities. A finite element numerical model of concrete beam column joints with super elastic SMA bars and steel end plates was established based on Open Sees finite element analysis platform, and the hysteretic and skeleton curves of the joints obtained from experiments and numerical simulation under low cycle reciprocating loading were compared to verify the effectiveness of the numerical model, while the effects of SMA bar diameter, yield strength and other parameters on the hysteretic energy consumption, stiffness degradation, residual deformation and other mechanical properties of the designed joints in this paper were further analyzed. The results show that the parameters such as the diameter and yield strength of SMA bars have great influence on the carrying capacity and self centering energy consumption of the new joint. On the premise of suitable reinforcement, the larger diameter of SMA reinforcement we design, the higher bearing capacity and self centering performance of the joint will have. Within a certain range, the increase of the yield strength of SMA bars has little effect on the overall stiffness of the joint, but has a greater effect on the residual deformation. [ABSTRACT FROM AUTHOR]

In view of the current research status that the experimental methods to study the effect of solute rare earth on the mechanical properties of steel has not achieved satisfactory results, in this paper, a system research was carried out by means of simulation calculation, and first-principles calculation method based on density functional theory was used to reveal the solid solution mechanism of Ce atoms in α-Fe by solvation energy, geometric structure, electronic structure, and Bader charge. And the mechanical properties of Fe-Ce doped system were calculated in detail. The calculation results of the solvation energy show that Ce can occupy the α-Fe matrix by replacing Fe atoms. In Fe-Ce doped system, Ce atoms lose electrons, resulting in a reduction in the radius of Ce atoms and a polarization effect, which is conducive to the solid solution of Ce in Fe. The calculation results of the mechanical properties of pure Fe and Fe-Ce doped system show that Ce doping reduces the incompressibility, shear strain resistance, rigidity, and Vickers hardness of the system, but improves the toughness and workability of the system. Ce doping leads to a decrease in the strength of the metallic bond of the system, which is the main reason for the decrease in the incompressibility, rigidity and hardness of Fe-Ce doped system. On the other hand, the doping of Ce increases the density of the electron cloud in the system, which is conducive to the improvement of the toughness of the doped system. [ABSTRACT FROM AUTHOR]

Graphene (G)/graphene oxide (GO) has shown promising applications in improving the mechanics and functionality of cement materials with its excellent mechanical, electrical, and thermal conductivity properties. However, these nanomate rials are difficult to disperse in cement-based materials, which limits their practical application in cement-based composites. Tn recent years, researchers have begun to mix fibers with these nanomaterials into cement-based materials, and its dispersion performance has been greatly improved. Tn this paper, the influence of graphene, GO and other fiber mixture on cement-based composite materials is systematically described from five aspects of material dispersion in cement, cement hydration process, mechanical properties, functionality and durability, which has a guiding role in improving the performance of cement-based composite materials in the future. [ABSTRACT FROM AUTHOR]

In order to solve the issue of poor mechanical properties of the recycled mixture, this paper analyzed and studied the influence of RAP material aging degree to the performance of the mixture through aging test and unconfined compressive strength and splitting strength test of the mixture under different aging degrees. Primary emulsified asphalt dosages were selected by specific surface area of aggregate and effective asphalt film thickness. Then, by analyzing the relationship between the dosages of emulsified asphalt and the compressive strength, splitting strength and resilient modulus of the mixture, the best dosage of emulsified asphalt was calculated. The results show that RAP aging is an important reason for poor mechanical properties of the recycled mixture, and reasonable emulsified asphalt content can effectively improve the mechanical properties of the recycled mixture. [ABSTRACT FROM AUTHOR]

In order to clarify the rheological mechanical properties of millet grain group during mechanical harvesting and processing, this paper studied the effects of different varieties and different moisture contents on the creep characteristics of millet grain group. In this experiment, different varieties (Jingu 21, Zhangza 10), and different moisture contents (12.10%, 16.05%, 20.00%) of millet grain group were selected as creep experimental factors. The creep characteristics (instantaneous elastic modulus, delayed elastic modulus, relaxation time and viscosity coefficient) of millet seed group were used as experimental indicators, and one-way analysis of variance and multi-factor analysis of variance were performed. Based on the original contents of millet seed group, the target moisture contents of the millet grain group were formulated to be 12.10%, 16.05%, 20.00%. The experiment was conducted on the CMT-6104 universal testing machine, and the special fixture for testing the creep characteristics of millet grain group was designed. Combining the Burgers model, nonlinear programming method was used to optimize search regression parameters, and creep parameters of millet grain group were obtained. The creep curve of millet grain group of different varieties showed that, as time going on, the amount of deformation caused by creep tended to be constant, which reaching the strain saturation. There were differences in the millet grain group creep characteristic curves of the different varieties. The significance test standard was 0.05, and the variance analysis was performed. The results showed that the creep characteristics of millet grain group could be described by the four-element Burgers model, and the creep parameters of millet grain group with different moisture content and different varieties were different. The variety had a significant effect on the delayed elastic modulus of the millet grain group. The delayed elastic modulus of the Jingu 21 millet grain group was higher than that of Zhangza 10. The moisture content had significant effects on the instantaneous elastic modulus, delayed elastic modulus and viscosity coefficient of the millet grain group, which was decreasing while the moisture increasing. The instantaneous elastic modulus of the millet grain group with the water content of 12.10% was significantly higher than the water content of 16.05% and 20.00%. The delayed elastic modulus of the millet grain group with the moisture content of 12.10% was significantly higher than the water content of 20.00%. The instantaneous elastic modulus and the delayed elastic modulus represented elasticity and hardness of the millet grain group, respectively. With the increasing of the moisture content of the millet grain group, the instantaneous elastic modulus and the delayed elastic modulus of millet grain group decreased, resulting in a high increasing of the creep curve. The strain in the screw conveyor of combine harvester was correspondingly larger. In this paper, the creep properties of millet grain group with different varieties and different moisture contents were studied experimentally, which provided theoretical support for low-loss harvesting, processing and storage and parameter optimization of millet. There are many factors affecting the mechanical properties of the material, in addition to the influence of moisture contents and varieties, it is also related to many factors such as temperature, internal molecular structure and chemical composition of the material, et al. The rheological properties of agricultural materials need to be further studied in conjunction with the principles of life sciences. [ABSTRACT FROM AUTHOR]

The silo has the advantages of small area, good sealing conditions, low circulation costs, low cost and etc. It is currently the leading warehouse type of grain storage in China. Most silos still use gravity-based discharging methods, however, arches often form during silo discharging, it causes the pressure that should have been taken from the bottom of the warehouse to the wall of the warehouse. As a result, cracks may form in the silo walls causing serious damage. In addition, when there are workers above the grain surface or when the arch is manually broken, the collapse of the arch will not only result in personal injury or death of the grain surface staff, but also may damage the warehouse structure and facilities in the warehouse. In recent years, with the development of building technology, the silo volume has been continuously increasing, the diameter and height of the silo have also become larger and larger, and the related accidents caused by unloading and arching silos have also become more frequent Silo arch accidents in Daqing 2013, Lanxi 2015, in Heilongjiang province, and in Jing County in 2016 in Anhui province, for example, have resulted in the destruction of some silo facilities and casualties. Existing studies have shown that silo unloading and arching are closely related to the internal and external friction of grain. However, in those studies, a single circular particle is used in the current discrete element simulation. The real contact area of simulated grain is much smaller. As such, the simulation cannot objectively reflect the grain of the unloading process. The frictional situation is also more difficult to restore the mesoscopic dynamic process of unloading grain arching. In this paper, based on the existing PFC3D discrete element program, the micro particle simulation dust with larger viscosity coefficient was added to create an improved particle for the defect that the internal friction force of the circular particle in the discrete element simulation was smaller than that in the real grain. We used geometric methods in the structural mechanics model to determine the contact between the circular particles and derives the force-displacement relationship between the basic units. Based on typical accident cases and laboratory test results, the established particle structure mechanics model was used to simulate the force-displacement relationship between circular large particles and between small round particles and walls in the dynamic process of unloading grain and arching. The displacement map of shear stress and its stress characteristic curve were basically consistent with the experimental results. By using this model, the dynamic meso-mechanism of unloading and arching silos can be objectively reflected. The improved particle structure mechanics model proposed in this paper can not only be used to simulate the unloading and arching mechanism simulation, but also has certain reference value for the simulation of the characteristics of loose particles flow and the mechanism of the interaction between the bulk and the silo wall. [ABSTRACT FROM AUTHOR]

In this paper, molecular dynamics (MD) method was used to simulate the binding energy, cohesive energy density, radial distribution function and mechanical properties of the polymer bonded explosives (PBXs) systems constructed by polyurethane (Estane 5703), Ethylene - Propylene - DieneMonomer (EPDM), fluoropolymer (F2311) and 2, 6 - dipicrylamino - 3, 5 - dinitropyridine (PYX) (011 ) crystal face. The results showed that the interaction between Estane 5703 and PYX (011) is the strongest. The order of cohesive energy density between different binders and crystals is PYX/F2311 > PYX/Estane 5703 > PYX/EPDM. The radial distribution function analysis showed that the interaction between PYX (011 ) crystal face and polymer molecules is mainly electrostatic interaction. After adding three kinds of binders, the tensile strength and breaking strength of the PBX system are improved. In addition to F2311, the addition of two other binders improves the shear strain resistance of PBX system. [ABSTRACT FROM AUTHOR]

AgSnO2 cont act material has become one ol the electrical contact materials to replace AgCdO because ol its excellent performance. However, since the poor electrical conductivity and high hardness ol SnO2, the material will become brittle and easy to form cracks, which reduces service lile ol AgSnO2 contacts. In this paper, the first-principles method based on density lunctional theory is adopted to study the electrical conductivity and mechanical properties of the rare earth elements Ce and C single-do ped and co-do ped SnO2 ・ Through the energy calculation alter the supercell structure is optimized, the lattice constant, doping lormation energy, band structure, density of state, elastic constant and Debye temperature ol the supercell are obtained. The results show that the band gap value ol doped tin dioxide is reduced and the hybrid orbit increased, the conductivity ol Sn02 and the brittleness and toughness ol SnCh can be improved, thereby improving the forming and service lile ol AgSnCh contacts. Compared with Ce and C single doping, the eflective electronic mass of Ce-C co-do ping is reduced, and the band gap width is narrowed. Ce-C co-doped SnC)2 has better conductivity and greater improvement in hardness. [ABSTRACT FROM AUTHOR]

As a near-net forming technology, additive manufacturing has a wide application prospect in aerospace, military and other important fields. In this paper, the research progress on the shape and property control of the gas metal arc welding additive manufacturing technology at home and abroad is reviewed. The surface forming accuracy, internal defects, residual stress and deformation, microstructure and proper ties of the components a re mainly described. The principles, characteristics and development prospects of different shape and property control technologies are summarized. [ABSTRACT FROM AUTHOR]

The silo has the advantages of small area, good sealing conditions, low circulation costs, low cost and etc. It is currently the leading warehouse type of grain storage in China. Most silos still use gravity-based discharging methods, however, arches often form during silo discharging, it causes the pressure that should have been taken from the bottom of the warehouse to the wall of the warehouse. As a result, cracks may form in the silo walls causing serious damage. In addition, when there are workers above the grain surface or when the arch is manually broken, the collapse of the arch will not only result in personal injury or death of the grain surface staff, but also may damage the warehouse structure and facilities in the warehouse. In recent years, with the development of building technology, the silo volume has been continuously increasing, the diameter and height of the silo have also become larger and larger, and the related accidents caused by unloading and arching silos have also become more frequent Silo arch accidents in Daqing 2013, Lanxi 2015, in Heilongjiang province, and in Jing County in 2016 in Anhui province, for example, have resulted in the destruction of some silo facilities and casualties. Existing studies have shown that silo unloading and arching are closely related to the internal and external friction of grain. However, in those studies, a single circular particle is used in the current discrete element simulation. The real contact area of simulated grain is much smaller. As such, the simulation cannot objectively reflect the grain of the unloading process. The frictional situation is also more difficult to restore the mesoscopic dynamic process of unloading grain arching. In this paper, based on the existing PFC3D discrete element program, the micro particle simulation dust with larger viscosity coefficient was added to create an improved particle for the defect that the internal friction force of the circular particle in the discrete element simulation was smaller than that in the real grain. We used geometric methods in the structural mechanics model to determine the contact between the circular particles and derives the force-displacement relationship between the basic units. Based on typical accident cases and laboratory test results, the established particle structure mechanics model was used to simulate the force-displacement relationship between circular large particles and between small round particles and walls in the dynamic process of unloading grain and arching. The displacement map of shear stress and its stress characteristic curve were basically consistent with the experimental results. By using this model, the dynamic meso-mechanism of unloading and arching silos can be objectively reflected. The improved particle structure mechanics model proposed in this paper can not only be used to simulate the unloading and arching mechanism simulation, but also has certain reference value for the simulation of the characteristics of loose particles flow and the mechanism of the interaction between the bulk and the silo wall. [ABSTRACT FROM AUTHOR]

The silo has the advantages of small area, good sealing conditions, low circulation costs, low cost and etc. It is currently the leading warehouse type of grain storage in China. Most silos still use gravity-based discharging methods, however, arches often form during silo discharging, it causes the pressure that should have been taken from the bottom of the warehouse to the wall of the warehouse. As a result, cracks may form in the silo walls causing serious damage. In addition, when there are workers above the grain surface or when the arch is manually broken, the collapse of the arch will not only result in personal injury or death of the grain surface staff, but also may damage the warehouse structure and facilities in the warehouse. In recent years, with the development of building technology, the silo volume has been continuously increasing, the diameter and height of the silo have also become larger and larger, and the related accidents caused by unloading and arching silos have also become more frequent Silo arch accidents in Daqing 2013, Lanxi 2015, in Heilongjiang province, and in Jing County in 2016 in Anhui province, for example, have resulted in the destruction of some silo facilities and casualties. Existing studies have shown that silo unloading and arching are closely related to the internal and external friction of grain. However, in those studies, a single circular particle is used in the current discrete element simulation. The real contact area of simulated grain is much smaller. As such, the simulation cannot objectively reflect the grain of the unloading process. The frictional situation is also more difficult to restore the mesoscopic dynamic process of unloading grain arching. In this paper, based on the existing PFC3D discrete element program, the micro particle simulation dust with larger viscosity coefficient was added to create an improved particle for the defect that the internal friction force of the circular particle in the discrete element simulation was smaller than that in the real grain. We used geometric methods in the structural mechanics model to determine the contact between the circular particles and derives the force-displacement relationship between the basic units. Based on typical accident cases and laboratory test results, the established particle structure mechanics model was used to simulate the force-displacement relationship between circular large particles and between small round particles and walls in the dynamic process of unloading grain and arching. The displacement map of shear stress and its stress characteristic curve were basically consistent with the experimental results. By using this model, the dynamic meso-mechanism of unloading and arching silos can be objectively reflected. The improved particle structure mechanics model proposed in this paper can not only be used to simulate the unloading and arching mechanism simulation, but also has certain reference value for the simulation of the characteristics of loose particles flow and the mechanism of the interaction between the bulk and the silo wall. [ABSTRACT FROM AUTHOR]

The silo has the advantages of small area, good sealing conditions, low circulation costs, low cost and etc. It is currently the leading warehouse type of grain storage in China. Most silos still use gravity-based discharging methods, however, arches often form during silo discharging, it causes the pressure that should have been taken from the bottom of the warehouse to the wall of the warehouse. As a result, cracks may form in the silo walls causing serious damage. In addition, when there are workers above the grain surface or when the arch is manually broken, the collapse of the arch will not only result in personal injury or death of the grain surface staff, but also may damage the warehouse structure and facilities in the warehouse. In recent years, with the development of building technology, the silo volume has been continuously increasing, the diameter and height of the silo have also become larger and larger, and the related accidents caused by unloading and arching silos have also become more frequent Silo arch accidents in Daqing 2013, Lanxi 2015, in Heilongjiang province, and in Jing County in 2016 in Anhui province, for example, have resulted in the destruction of some silo facilities and casualties. Existing studies have shown that silo unloading and arching are closely related to the internal and external friction of grain. However, in those studies, a single circular particle is used in the current discrete element simulation. The real contact area of simulated grain is much smaller. As such, the simulation cannot objectively reflect the grain of the unloading process. The frictional situation is also more difficult to restore the mesoscopic dynamic process of unloading grain arching. In this paper, based on the existing PFC3D discrete element program, the micro particle simulation dust with larger viscosity coefficient was added to create an improved particle for the defect that the internal friction force of the circular particle in the discrete element simulation was smaller than that in the real grain. We used geometric methods in the structural mechanics model to determine the contact between the circular particles and derives the force-displacement relationship between the basic units. Based on typical accident cases and laboratory test results, the established particle structure mechanics model was used to simulate the force-displacement relationship between circular large particles and between small round particles and walls in the dynamic process of unloading grain and arching. The displacement map of shear stress and its stress characteristic curve were basically consistent with the experimental results. By using this model, the dynamic meso-mechanism of unloading and arching silos can be objectively reflected. The improved particle structure mechanics model proposed in this paper can not only be used to simulate the unloading and arching mechanism simulation, but also has certain reference value for the simulation of the characteristics of loose particles flow and the mechanism of the interaction between the bulk and the silo wall. [ABSTRACT FROM AUTHOR]

The silo has the advantages of small area, good sealing conditions, low circulation costs, low cost and etc. It is currently the leading warehouse type of grain storage in China. Most silos still use gravity-based discharging methods, however, arches often form during silo discharging, it causes the pressure that should have been taken from the bottom of the warehouse to the wall of the warehouse. As a result, cracks may form in the silo walls causing serious damage. In addition, when there are workers above the grain surface or when the arch is manually broken, the collapse of the arch will not only result in personal injury or death of the grain surface staff, but also may damage the warehouse structure and facilities in the warehouse. In recent years, with the development of building technology, the silo volume has been continuously increasing, the diameter and height of the silo have also become larger and larger, and the related accidents caused by unloading and arching silos have also become more frequent Silo arch accidents in Daqing 2013, Lanxi 2015, in Heilongjiang province, and in Jing County in 2016 in Anhui province, for example, have resulted in the destruction of some silo facilities and casualties. Existing studies have shown that silo unloading and arching are closely related to the internal and external friction of grain. However, in those studies, a single circular particle is used in the current discrete element simulation. The real contact area of simulated grain is much smaller. As such, the simulation cannot objectively reflect the grain of the unloading process. The frictional situation is also more difficult to restore the mesoscopic dynamic process of unloading grain arching. In this paper, based on the existing PFC3D discrete element program, the micro particle simulation dust with larger viscosity coefficient was added to create an improved particle for the defect that the internal friction force of the circular particle in the discrete element simulation was smaller than that in the real grain. We used geometric methods in the structural mechanics model to determine the contact between the circular particles and derives the force-displacement relationship between the basic units. Based on typical accident cases and laboratory test results, the established particle structure mechanics model was used to simulate the force-displacement relationship between circular large particles and between small round particles and walls in the dynamic process of unloading grain and arching. The displacement map of shear stress and its stress characteristic curve were basically consistent with the experimental results. By using this model, the dynamic meso-mechanism of unloading and arching silos can be objectively reflected. The improved particle structure mechanics model proposed in this paper can not only be used to simulate the unloading and arching mechanism simulation, but also has certain reference value for the simulation of the characteristics of loose particles flow and the mechanism of the interaction between the bulk and the silo wall. [ABSTRACT FROM AUTHOR]

Based on virtual crystal potential function (VCA) approximation, this paper uses the first principle pseudopotential plane wave method of density functional theory to comparatively analyze impacts of different Cr microalloying concentrations x= Q 1.0%，atomic percentage, the same below) on B2 NiAl Cauchy pressure parameter，and crystal elastic constant C44，shear modulus G and G/Bo ratio, elastic modulus E. The results of micro electron energy density analysis indicate that the shear modulus G and elastic modulus E of pure NiAl crystal material can be significantly improved by Cr atom replacing Ni atom or A1 atom，but it's not conducive to improve its ductility. It is found that the synergistic effect of Cr atoms and the point defect structure in the crystal can improve the ductility of the crystal, and the A1 site in the Ni inversion structure is replaced by Cr atoms, and the alloying concentration x = Q、9%，the effect is particularly obvious. [ABSTRACT FROM AUTHOR]

In order to control the strain caused by large temperature drop in mass concrete construction, which leads to the generation and development of micro cracks, concrete anti - cracking agent has been tested and applied in mass concrete construction with its excellent performance of compensating shrinkage. In this paper, the construction workability, heat dissipation and mechanical properties of impermeable concrete with different concentrations of HME - V anti - cracking agent (0, 4%, 8%, 12%, 16%) are studied by using the shri~e compensating concrete technology. Meanwhile, it is compared with the impenneable concrete with 0. 4% polypropylene fiber. ABAQUS finite element software is used to numerically simulate the temperature field and plastic damage during the construction of the roof and side walls of the twmel. The test results show that the impermeable concrete prepared with anti - cracking agent has better workability, better mechanical properties than the original concrete, and has good performance in plastic damage and mass heat dissipation. [ABSTRACT FROM AUTHOR]

Geopolymer is a new green cementitious material, which has many excellent properties in mechanical properties and durability, but also has some shortcomings. It is feasible way to overcome the disadvantages of geopolymer by using the advantages of nano materials. In this paper, the influence of nano materials blending geopolymer on the workability, mechanical properties and durability of the mixture was systematically de scribed. The influence mechanism was summarized and the existing problems of nano modified geopolymer were discussed. The future modification research may include revealing the influence mechanism, focusing on the comp<1tibility and synergy between nano materials and other components, accunnely designing and developing nano core-shell particles suitable for geopolymer reaction system, and quantificationally evaluating the disper sion of nanoparticles in aqueous solution and colloidal environment. Improving the modification effi ciency of nano particles provided a reference for the future research on nano modified geopolymer. [ABSTRACT FROM AUTHOR]

In this paper, the effect of service conditions at different temperatures ( 77K ~ 77:3 K) on the mechanical properties of entropy alloy in VCoNi was studied. Grain size of VCoNi alloy was adjusted by large deforma tion rolling and short time annealing. The change rule of material mechanical properties was st udied by quasi static tensile test and the internal mechanism was explained by microscopic observation. at 77 K, a large number of twins and twisted dislocations in the material made the alloy have excellent comp rehensive properties. With the increase of experimental temperature from 29:3 K tO 57:3 K, the elongation and mechanic;d properties of the materials remained stable. When the experimental tempen1ture reached :37:3 K, the serneted flow appeared on the stress-strain curve. [ABSTRACT FROM AUTHOR]

In this paper, an innovative compression technology is developed to study and analyze the mechanical properties of lotus seed kernel with regard to elastic modulus, compression strength and ultimate load when the whole lotus seed kernel is under the pressure. The objectives of this paper are to study the damage and crushing characteristics of lotus seed kernel under the condition of squeezing the load and reducing the crushing rate in the processing and transportation. Firstly, the universal testing machine is utilized to implement tests of elastic modulus and compression strength for lotus seed kernel samples. A series of the mechanical properties are measured for the lotus seed kernel with varied moisture content (5.52%, 7.78%, 10.29%, 12.47%, and 15.06%) in terms of vertical elastic modulus, horizontal elastic modulus, longitudinal compression strength and transverse compression strength. The corresponding transverse stress-strain curve and longitudinal stress-strain curve are figured out. The measurement results indicate the vertical and horizontal elastic modulus and compression strength of lotus seed kernel decrease with the increase of moisture content. The longitudinal values are higher than transverse values as to samples with same level of moisture content. Therefore, lotus seed kernel belongs to a kind of anisotropic material. It is much easier to cause lotus seed kernel broken when it suffers horizontal compression. When the moisture content is relatively low (5.52%, 7.78%, 10.29%), there is a linear relationship between stress and strain. Lotus seed kernel shows brittleness. If the moisture content is much higher (12.47%, 15.06%), strain becomes larger, which means lotus seed kernel has great toughness. The regression equation is established for the sake of carrying out regression analysis based on test results of elastic modulus and compression strength. It is obtained that the minimum compression strength and minimum elastic modulus of qualified lotus seed kernel with moisture content smaller than 11% are 5.12 and 37.12 MPa respectively. Furthermore, the crack caused by compression is also discussed on the basis of varied moisture contents and different compression methods. It is measured that the ultimate loads under the flat pressure for 5 experimental samples are 103.92, 89.87, 72.21, 59.60 and 51.73 N, respectively. Similarly, the ultimate loads under the side pressure are 88.19, 72.78, 57.80, 45.58 and 39.16 N, respectively. From the measurement data, the moisture content and compression method of lotus seed kernel have great influence on ultimate loads. The ultimate loads increase with the decrease of moisture content, no matter it suffers side pressure or flat pressure. Furthermore, the ultimate load of side pressure is less than that of flat pressure in terms of same level of moisture content. Therefore, side pressure is much easier to make the lotus seed kernel broken. The first crack positions are the load position, parting surface and area around the drilled hole in flat pressure test. As to the side pressure test, the first crack positions are on the both sides of parting surface. Based on the test results of ultimate loads of lotus seed kernels, a regression model of ultimate loads and moisture content is established. It is calculated that the maximum compression load of the qualified lotus seed kernel (moisture content is less than 11%) should be less than 53.60 N. In practical cases, the compression load should be less than this limit value. Lastly, a dynamic model of lotus seed kernel compression is developed with the finite element method. The stress distribution of pressure states of lotus seed kernel is figured out. The analysis results demonstrate the stress at load position, parting surface and area around the drilled hole is larger in flat and side pressure tests. The parting surface is the weak part of lotus seed kernel. It expresses that the simulation results well fit the crack position and direction in the compression test, which identifies the correctness of measurement parameters. The study results provide a reliable evidence for determining process parameters of processing and conveying equipment in the lotus seed kernel production. [ABSTRACT FROM AUTHOR]

Millet contains protein, vitamin B1 and other mineral elements needed for human health, which has functions of enhancing blood circulation, brain tonic, and sleep quality. In recent years, the market demand for millet is rising. However, the mechanization level of millet harvesting is low. Manual harvesting is very common, which requires high labor intensity, has low efficiency and results in insufficient supply of millet. In this paper, we systematically investigated effects of moisture content and varieties of millet on its physical parameters, effects of millet varieties and compression azimuth on the compression mechanical properties (including yield load, deformation, failure energy and apparent elastic modulus) of millet, and effects of compression azimuth on crack formation of millet. The study results are expected to provide the basis for the design and optimization of millet harvester and related processing machinery. In this paper, the 1000-grain weight was measured by an electronic balance, the triaxial sizes by a vernier caliper, and the moisture content by fast grain moisture analyzer for four millet varieties: Zhangza-10, Dungu, Jingu-21, Changgu. The sphericity of the millet, the arithmetic mean diameter and the geometric diameter were calculated using the triaxial sizes. The compression tests were carried out along X, Y, Z axis using a texture analyzer and the data were analyzed by SAS statistics software. The yield load, deformation, and failure energy were obtained from the force-distance curve measured by a texture analyzer. At the same time, the apparent elastic modulus was calculated according to the Hertz formula. The experimental results were summarized as follows in six categories. 1) For the physical parameters of the millet, with a moisture content between 15.2% and 25.1%，the length, width, height, 1 000-grain weight, average diameter and geometric mean diameter of millet grain decreased as the moisture content decreased. The millet length, width and thickness range from 2.028 to 2.112 mm, 1.818 to 1.931 mm, 1.413 to 1.513 mm, respectively. The sphericity of millet was more than 84%; the arithmetic mean diameter varied from 1.750 mm to 1.852 mm; and the geometric mean diameter 1.732 mm to 1.834 mm. Therefore, the shape of millet can be regarded as ellipsoid. There were significant differences (P<0.001) in the triaxial sizes, 1000-grain weight, sphericity, arithmetic mean diameter and geometric mean diameter among different varieties. When the moisture content of millet was about 25%, the 1000-grain weight of Jingu-21 was 3.473 g, which was the heaviest millet, while Zhangza-10 was 3.264 g, which was the lightest millet. The moisture content has a negligible effect on the sphericity. The effect of varieties on sphericity was significant (P<0.001). 2) For factors on the compression mechanical properties, the influence of moisture content, compression azimuth, and variety on the compression mechanical properties were significant (P<0.01). The significant factors affecting the compression mechanical properties were compression azimuth, moisture content, and variety in a sequence from the most significant to the least significant. 3) For the effects of the moisture content, for the same kind of millet, the yield load and apparent elastic modulus decreased as the moisture content increased during compression in X, Y, Z axis. The yield load decreased slowly when moisture content ranged from 20.9% to 25.1%. The deformation and failure energy first decreased and then increased as the moisture content increased. For the same azimuth compression, the better the quality of the millet, the more compact the internal structure, and the smaller the deformation. 4) For crack formation of the millet: on the X axial, a crack started from the crest of the grain along the junction of embryo and endosperm, and then extended throughout the X axis. On the Y axis, a crack started from the connection point of grain and probe and the connection point of grain and base throughout the Y axis because of stress concentration. On the Z axis, a crack started from the junction of embryo and endosperm on the back to the ventral hilum along the weakest part of endosperm resistance extending throughout half of the grain. 5) For the effects of compression azimuth, the yield load increased in turn on the X, Y, and Z axis and the deformation and failure energy decreased on the X, Z, and Y axis in turn. The apparent elastic modulus of the millet increased in turn on the X, Y, and Z axis. This result indicated that millet was not uniform and it was an anisotropic body. 6) For the effects of millet varieties, with the same moisture content, the compression mechanical properties of Jingu-21, Dungu, Changgu and Zhangza-10 varied from large to small. This indicated that Jingu-21 had a relatively good compression resistance and quality. [ABSTRACT FROM AUTHOR]

The mechanical properties of Satsuma mandarin are an important basis for the design and control of the automatic peeling device. In this paper, Satsuma mandarin was taken as the research object, and TMS-PRO texture analyzer was adopted. Special scissors cut along the fruit radial (fruit maximum equatorial diameter direction) and axially peeled out and pulled out different peeling widths. Citrus fruit top and pedicle were fixed in the 2 clamping edges of the fixed clamping mechanism or the longitudinal axis perpendicular to the clamping edges, and the radial part was fixed in the 2 clamping edges of the fixed clamping mechanism. Gripper clamped the peeled part of the peel. The moving probe of the texture instrument drove the gripping mechanism to move to overcome the adhesive force between peel and pulp. As the texture instrument continued to pull peel, the peel was peeled off from citrus surface. The maximum tensile force and the displacement in the separation of peel were obtained, which were as the experimental indices. The smaller the maximum separation tension, the more easily separated the skin of the citrus fruit; the separation of the larger displacement indicated that the longer the peeled peel length, the better the effect of peeling. The paper studied the peeling law of Satsuma mandarin in different pulling direction, pulling width and pulling speed by carrying out the mechanical properties test of peeling citrus. The main results were as follows: Firstly, there were 3 types of rupture during citrus peel separation (peel symmetrical tear, peel oblique tear and jagged cracks), in which the citrus peel length with symmetric cracks was the largest and the displacement was the best. Asymmetrical and jagged cracks forms of peel separation lead to shorter separation of peel, which is not conducive to achieving higher peel rate. Secondly, the stripping direction had the most significant effect on the maximum tension value of citrus fruits (P=0.006). The stripping direction also had a significant effect on the displacement (P=0.016). Results showed that the peeling strength of Satsuma mandarin had obvious anisotropy. Compared with radial direction of peeling, peeling width of the axial skin peeling is conducive to peel citrus, which can get longer peel. Thirdly, the peeling width had a significant effect on the maximal pulling force (P=0.034) and the displacement (P=0.795) in citrus fruit. When the peeling width was 25 mm, the maximum tension value was lower, 2.31 N. When the peeling width was 35 mm, the maximum tension value was larger, 2.55 N. When the peeling width was in the range of 25-35 mm, the displacement value was 47.32-48.33 mm and the fluctuation was small. Peel separation force increased as the width of the skin increased. For the existing citrus peeling machine with random cutting approach was not conducive to peeling, the ring cutting peeling should be used for the existing roller way to provide the possibility of axial peeling. At last, the maximum pulling force (P=0.043) and the separation displacement (P=0.105) were not significant. Peeling separation force increased with the increasing of pulling speed. For most of roller citrus peeling equipment, the maximum clamping force of the roller was generally much larger than the stripping force, so the citrus in the rolling process chose larger peeling width (the ring cut peel) and peeling speed, and peel separation process was more stable and efficient. In conclusion, this study provides an important basis for the design of wide-peel citrus peeling machine. [ABSTRACT FROM AUTHOR]

Structure characteristic is a typical feature of the unsaturated undisturbed loess, which is an important key factor to affect its strength, deformation properties, and son on, and to distinguish the loess from other special soils. To understand the structure of loess, the key is to find the right way to study the structure. Computerized tomography (CT) technology can detect nondestructively the internal meso-structure in real time, so it is used to be a powerful means for loess structure research. However, it is few reports about the influence of structure on yielding features and the structural evolution characteristics of unsaturated loess during isotropic loading process. In this paper, we took the multifunctional geotechnical triaxial apparatus and the CT technology to research loess structure, and the hydrostatic triaxial compressure tests were carried out by using of 4 undisturbed loess samples whose control matric suction was a constant. When the value of volumetric deformation and water displacement of loess samples reached the expected criteria during loading process, we scanned nondestructively the 4 loess samples with the help of CT technology and got some CT scanning data and images. The structural evolution law of the undisturbed loess during isotropic loading procedure was described by means of the relationship between the macro-scopic mechanical index and the meso-scopic scanning data. In these studies, we found that the structure of undisturbed loess could resist the external load to a certain extent, but the influence of loess structure on yielding characteristic was closely related to matric suction. The CT number increased slowly before sample yielding, however, after sample yielding, the structural effect was reduced obviously and the CT number had a linear growth trend, which indicated that the loess sample entered into the plastic hardening stage. When the suction increased, the structure of undisturbed loess had little effect on the mechanical deformation. When the suction decreased, the water film lubrication between soil particles was obvious, so the effect of the structure fighting against the external load was enhanced obviously. After the net mean stress was applied, the voids and pores of loess samples would decrease, but they would not be closed completely, which was related to the formation of new structures that resisted external loads. According to the CT scanning data, the structural parameters and the structural damage variable were defined during isotropic loading tests, respectively, and then the evolution characteristics of the meso-structure of the undisturbed loess were clarified. In addition, we described accurately the relationships between the structural damage variables and the volumetric strain, and the change of the water phase of loess samples, respectively, and established the damage evolution equation of undisturbed loess structure during isotropic loading procedure. This new damage equation had the characteristics of one parameter and simple form, and could well reflect the influence of the change of solid and liquid phase on the structural damage. The validity of new equation was verified preliminarily by comparison of computation results and test data, which indicated very good agreement between each other. The research results in this paper will provide the reference for establishing the structural constitutive model of undisturbed loess and give a gateway to reasonably analyze loess structure. [ABSTRACT FROM AUTHOR]

In this paper, high purity Ta-Ru alloy was prepared by powder metallurgy hot press sintering. Tantalum ruthenium powder with high purity was mixed in different composition ratio on planetary ball mill, and hot pressed for 3 h at 1 700 ℃ and 20 MPa in vacuum hot pressing sintering furnace. The effect of different Ru contents on the phase composition, microstructure and mechanical properties of Ta-Ru alloys were investigated by XRD, SEM, EDS, tensile strength test and other analytical methods. The results show that, with increasing Ru content, several intermetallic compounds such as TaRu, Ta3Ru, and TaRu4 were successively formed in the alloy. The density and tensile strength of the alloy increased gradually, and the microhardness increased first and then decreased. The fracture mode changed from cleavage fracture to intergranular fracture and ductile fracture. [ABSTRACT FROM AUTHOR]

To investigate the mechanical properties of composite paperboard at different strain rates，quasistatic and dynamic tensile tests were carried out by universal material testing machine and high-speed testing machine. Meanwhile，the tensile failure process and strain field were recorded by using high-speed camera and digital image correlation（DIC） method. The test results reveal that the mechanical properties and failure mechanism of paperboard show significant strain rate dependence. With the increase of strain rate，the tensile strength of the studied material increases significantly，and the fracture strain also shows obvious strain rate dependence at intermediate strain rate. By comparing the test results with the fitting results of the three models of strain rate dependence ratio，the characterization model based on Cowper-Symonds equation can well describe the strain rate dependence of composite paperboard at low and intermediate strain rates. The proposed model can be used not only for the simulation and theoretical research on the energy absorption performance of thin-walled paper tube，but also for the design of impact protection structure [ABSTRACT FROM AUTHOR]

In this paper, two series of quick-setting 3D printing cement-based materials were prepared with fast hard sulphoaluminate cement and ordinary Portland cement as basic cementing materials, supplemented by water reducing agent, coagulant and volume stabilizer, etc., in order to achieve rapid printing. The experimental results show that the prepared quick-setting 3D printing cement-based material could control the setting time within 5-20 min. The printed specimen had good construction performance with the over all deformation less than 5% and the lowest deformation less than10%. The printed specimen had early and late strength, and the simulated print sample strength loss rate did not exceed 15%, meeting the requirements of architectural 3D printing materials for work performance and mechanical properties. [ABSTRACT FROM AUTHOR]

From the perspective of materials research, in this article, the latest developments in equipment and technology of selective electron beam meting process (SEBM), and the published data on the mechanical properties of orthopedic medical materials were reviewed. The technical barriers of current orthopedic medical materials fabricated by SEBM technology alloys were mainly analyzed in detail. Suggestions for further development on biomaterials 3D printing industry were also given at the end of the paper. [ABSTRACT FROM AUTHOR]