Search

There have been no reports of the simultaneous application of natural fillers, such as magnetite and natural zeolites, to increase the strength of composites containing silica (SiO2) fillers as reinforcing fillers in natural rubber. This study has investigated the effect of magnetically modified natural zeolite on nanosilica-reinforced natural rubber composites that include a mechanical characteristic like human tissue. We use technical specifications rubber (TSR) SIR 20 with nanosilica reinforced fillers and Titanate coupling agent (TCA) as fillers and elastomer binders. The results showed that the nanosilica-zeolite-magnetite (Fe3O4) mixture had an influence on strength and stiffness and could be a substitute filler. The precursors made with some variations include the optimization of filler and the optimization volume fraction of nanosilica. Mechanical characteristics of different human body part tissue were compared to the control samples and have similar mechanical characteristics with internal human tissue characteristic. Based on these results, nanosilica fillers combine with magnetically modified zeolites and titanate coupling agents, potentially as an alternative filler to replace carbon black, and are applicable for synthetic muscle replacement cadavers with a customized formula.

Copyright of Railway Investigation & Surveying is the property of Railway Investigation & Surveying Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To ensure the safety of coal mining, lots of coal pillars were reserved in the coal mine. The stability of coal pillar and roof composite structures determines the safety of stope. Under the action of cyclic loading and unloading such as mining face, chamber blasting, and roadway excavation, the coal pillar, and roof composite structure will gradually instability, which will affect the safety production of the coal mine. Therefore, this paper takes the dynamic disaster of coal pillar and roof composite structure as the research background, carries on the cyclic loading and unloading test of the coal-rock composite structure with different coal-rock height ratios, and studies the influence of coal-rock height ratio on the progressive instability characteristics, mechanical properties and damage variables of the coal-rock composite structure. The crack initiation stress, crack propagation time and failure pattern of coal-rock composite structure are analyzed. The improved load-unload response ratio considering the damage variable is established, and the stability of the coal-rock composite structure under cyclic loading and unloading is quantitatively analyzed. It is concluded that the larger the coal-rock height ratio is, the greater the load-unload response ratio of the composite structure is, and the more unstable the composite structure is. This conclusion is consistent with the crack initiation stress and fracture propagation time, and can quantitatively reflect the progressive instability process of coal-rock composite structure, and provide a basis for revealing the dynamic disaster of coal pillar and roof composite structure. [ABSTRACT FROM AUTHOR]

Abstract Due to the fact that ballastless tracks in high-speed railways are not only subjected to repeated train–track dynamic interaction loads, but also suffer from complex environmental loads, the fundamental understanding of mechanical performance of ballastless tracks under sophisticated service conditions is an increasingly demanding and challenging issue in high-speed railway networks. This work aims to reveal the effect of train–track interaction and environment loads on the mechanical characteristic variation of ballastless tracks in high-speed railways, particularly focusing on the typical interface damage evolution between track layers. To this end, a finite element model of a double-block ballastless track involving the cohesive zone model for the track interface is first established to analyze the mechanical properties of the track interface under the loading–unloading processes of the negative temperature gradient load (TGL) followed by the same cycle of the positive TGL. Subsequently, the effect of wheel–rail longitudinal interactions on the nonlinear dynamic characteristics of the track interface is investigated by using a vehicle-slab track vertical-longitudinal coupled dynamics model. Finally, the influence of dynamic water pressure induced by vehicle dynamic load on the mechanical characteristics and damage evolution of the track interface is elucidated using a fluid–solid coupling method. Results show that the loading history of the positive and negative TGLs has a great impact on the nonlinear development and distribution of the track interface stress and damage; the interface damage could be induced by the wheel–rail longitudinal vibrations at a high vehicle running speed owing to the dynamic amplification effect caused by short wave irregularities; the vehicle dynamic load could produce considerable water pressure that presents nonlinear spatial–temporal characteristics at the track interface, which would lead to the interface failure under a certain condition due to the coupled dynamic effect of vehicle load and water pressure.

The dissimilar self-piercing riveted (SPR) joints between aluminium-lithium alloy (AL1420) and titanium (TA1) sheets were investigated. The effects of the overlap form and rivet hardness on the forming structures, quasi-static and fatigue characteristics of the considered dissimilar joints were analysed systematically. A new curve-fitting method was adopted to fit the fatigue data of SPR joints. The results show that the potential weak areas in the forming structures could be changed using different overlap forms or rivet hardness. The overlap form for the dissimilar joints plays a more important role on the joint strength compared to the rivet hardness, but has little influence on the energy absorption. The fatigue property of the dissimilar joints is improved with the rivet hardness increased and the joints taken TA1 as the locked sheet possess a better fatigue life. The rivet hardness presents an obvious influence on the fatigue fracture path. The forming structures of the dissimilar joints are significantly affected by the overlap forms, which finally results in the fatigue fracture originated in different initiation sites.

A well-known disadvantage of pneumatic tires is the cessation of the ability to work with mechanical damage through and determines the need to search for fundamentally new design solutions for automobile wheels to increase the safety of automobiles and the survivability of wheeled vehicles. One such solution is the use of airless tires made of elastic polymeric materials. The Department of Mechanical Engineering and Transport of the Bratsk State University has developed full-scale models of wheels with airless tires made of elastic polyurethanes of Russian production for a car. The theoretical evaluation of the resilientible properties, load capacity and force heterogeneity of the experimental models was carried out by the finite element method. Electronic solid-state geometric models of airless tires have been created. Attributes of electronic models correspond to the nominal parameters of the physical models of automobile wheels. Nonlinear elastic isotropic models of polyurethane elastomers were adopted for nonlinear static analysis. The characteristics of the normal suppleness of airless tires and the graphs of oscillations of normal force with constant normal deflection in different positions of the wheels relative to their central transverse planes are the results of finite element modeling and calculation. Theoretical research results may be claimed by manufacturers of wheeled vehicles and tractors, construction and road vehicles, special motor vehicles and wheeled planetary rovers.

Internal solitary waves represent a common physical phenomenon in water bodies such as oceans,coasts,and estuaries.They are induced by external disturbances on a pycnocline in a stably stratified water body,and the shear flow excited during their propagation is accompanied by huge energy,which poses a serious threat to the safety and stability of underwater engineering structures.Therefore,it is of great significance to explore the laws of interaction between internal solitary waves and engineering structures.On the basis of summarizing the research progress of many scholars both at home and abroad,the common methods for studies on the action characteristics of internal solitary waves on structures are introduced from the aspects of physical experiments and numerical simulations.In addition,this study gives a summary of the research results in the characteristics and laws of the horizontal force,vertical force,and moment on vertical cylinders under internal solitary waves and the sensitivity factors of the horizontal force.Finally,the issues that require further attention in follow-up research on mechanical characteristics of vertical columns umder internal solitary waves are raised.

Layered rocks pose the challenge of wellbore stability in drilling engineering because of the anisotropic mechanical properties caused by the distinct weak planes. To understand the significant anisotropy of layered rocks in real formation condition, true triaxial compression tests are conducted by numerical simulation in this study. It is revealed that the mechanical responses of layered rocks are either controlled by the rock matrix or dominated by the weak plane and exhibit three different types associated with the orientations of the weak plane (including the dip direction α and dip angle β). When the orientations of the weak plane are α = 0°–90° and β = 0°, 60°–90°, the failure and strength properties of layered rocks depend entirely on the rock matrix, classified to the first type. Whereas the layered rocks with angle α ≤ 45° and β = 15°–45° fail by slipping failure along the weak plane, the relationship curves of rock strength versus the intermediate principal stress (σ2) are downward convex parabolas. In the last type, the mechanical behaviors of layered rocks with α > 45° and β = 15°–45°, involved in the changes of failure mode and the strength curve, are complex. Besides, the limitation of the simulation is discussed, and further studies on layered rocks are essential. [ABSTRACT FROM AUTHOR]

Although the current ecological engineering technology can reinforce shallow landslides, it cannot reinforce deep landslides. A new type of ecological engineering technology-living tree stump slope protection was developed, aiming at the deficiency of current ecological engineering technology. For living stumps with different tap root lengths, the mechanical properties of the living stump slope and root system were analyzed. The model was based on the finite element method, using the Mohr-Coulomb failure criterion to consider the mechanical plasticity of the soil. The three-dimensional (3D) models of living stumps with different tap root lengths were simulated by embedded beam elements. Changes in stress and strain of soil and root system were simulated. The strength reduction method was used here to calculate the safety factor of the slope. The results showed that long taproots moved the soil shear stress area to deeper soil layers, increasing the stability of the slope. The root system in the middle and lower part of the slope mainly exerted its tensile strength and played a positive role in the stability of the slope. The longer the taproots, the more stable the slope. Slope stability may be affected by root length, spatial root morphology, and the spatial layout of the root system on the slope. Planting living stumps in the middle and lower part of the slope densely was recommended in ecological engineering.

Rock mass deformation failure and its mechanical characteristics in actual environment were basic research subjects in the current research field of rocks in cold regions. Mechanical characteristics of mode-I sandstone were investigated and analyzed under freeze thawing cycle, failure properties, and modes of the rock-like cracked mortar sample were measured and analyzed. Meanwhile, the finite element analysis of stress field of cracked sample was analyzed and calculated by means of the finite element program ANSYS. The experimental results showed that deterioration damage of mechanical parameters grew gradually worse as increasing of freeze thawing cycle. Compared with sound sandstone, fracture toughness KIC, tensile strength, and compressive strength for sandstone sample after 100 freeze thawing cycle increased by 44.55%, 42.61%, and 40.41%, respectively. And peak strength and elastic modulus of the cracked mortar sample decreased initially and then increased as increasing of crack angle of inclinations. A certain difference occurred in deterioration damage of mechanical parameters of cracked mortar sample with crack angle of inclination. Deterioration damage of mechanical parameters of cracked mortar sample with the 45° crack angle of inclination had the lowest value, and highest values of the cracked mortar sample with the 90° or 0° crack angle of inclinations. In addition, original damage inside rocks had obvious influence on theirs damage deterioration. Failure mode of cracked mortar sample at the different crack angle of inclinations was different, but the effect of freeze thawing cycle on failure modes of cracked sample was not obvious. [ABSTRACT FROM AUTHOR]

Gabion mixed media is an important ecological protection method for preventing riverbank scouring. It is favored by engineers for its use of local materials, low carbon footprint, and environmental friendliness. However, the mechanical characteristics of gabion mixed media are closely related to the shape of the gabion mesh, the diameter of the gabion wire, and the type of internal media. Thus, its macroscopic properties are difficult to analyze. Therefore, this study adopts a discrete element method, Particle Flow Code 3D (PFC3D), to establish a numerical calculation model of gabion structures. This method analyzes the mechanical characteristics of gabion structures filled with spherical and oblate stones by considering porosity, mesh shape, filler size, and mesh size. Key results demonstrate that the bearing capacity and stability of a gabion structure filled with oblate stones is stronger than that of a gabion structure filled with spherical stones, with an increase of about 25 % in bearing capacity. Porosity and mesh shape have a considerable effect on the compressive strength of the gabion structure. Compared with high-porosity gabion structures, low-porosity gabion structures have a 50 %−65 % increase in compressive strength. Additionally, hexagonal mesh gabion structures exhibit better stability than quadrilateral mesh gabion structures and under axial loads, the hexagonal mesh is less prone to breakage. Increasing mesh size may cause smaller fillers to overflow, reducing the porosity of gabion structures and resulting in decreased compressive strength. The results of this study can provide a basis for estimating integrated parameters of gabion mixed media and determining slope stability. • Random reconstruction of stone fillers and correction of gabion wire parameters improve the experimental results' reliability. • Gabion structures filled with oblate stones exhibit stronger bearing capacity compared to those filled with spherical stones. • Gabion structures with low porosity and hexagonal mesh display greater compressive strength and better stability. • Larger mesh sizes can lead to filler overflow, reducing porosity and compressive strength. [ABSTRACT FROM AUTHOR]

Despite the many advantages of pneumatic systems, one disadvantage is the noise accompanying the expansion of the exhaust air. In pneumatic exhaust systems, the pulse jet generates the impulse noise. The A-weighted sound pressure levels of exhaust system impulse noise can reach 96 to 108 dBA, or even up to 130 dBA. On the other hand, attempts to reduce pneumatic noise involve loss of performance by reducing the torque and speed of the pneumatic tool. Commonly used mufflers do not reduce the noise level below 85 dB. Our research introduces a novel air collection system, details its technical implementation, and conducts thorough experimental analysis comparing its noise reduction effectiveness and mechanical efficiency impact with traditional mufflers. In the study we conducted experimental tests on the noise level and mechanical properties of a pneumatic screwdriver in an anechoic chamber, and presenting the operational characteristics and sensitivity analysis of the air collection system geometry. Next the industrial implementation shows that a standard screwdriver produces levels of 90.7 dBA, while a screwdriver with a collection system produces levels of 82.8 dBA. Our findings indicate that the selection of the design parameters of an air collection system allows for the removal of acoustic energy from the area affecting the worker's exposure to noise, without compromising the efficiency of the production process. By eliminating this component of the noise associated with the air exhaust, the noise generated by the mechanical components of the screwdriver is exposed and becomes audible. [Display omitted] • Air collection system does not degrade the pneumatic screwdriver's torque. • Developed innovative solution mitigates pneumatic noise from exposure area. • Noise reduction of pneumatic screwdriver in laboratory test was 28 dBA. • The industrial test shows the noise reduction by 7.9 dBA. [ABSTRACT FROM AUTHOR]

Tao Li,1,* Lilan Fu,2,* Jian Wang,1 Zhanjun Shi11Department of Orthopedics, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, People’s Republic of China; 2Nanfang PET Center, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, People’s Republic of China*These authors contributed equally to this workPurpose: Low doses of vancomycin and gentamicin were commonly incorporated into acrylic bone cement (antibiotic-impregnated bone cement, AIBC) during revision arthroplasty. Previous studies showed that only a very small amount of antibiotics could be eluted from AIBC. Given the fact that a high dose of antibiotic would elute high concentration of antibiotic, this study investigated the influence of a high dose of dual-antibiotic loading on the properties of cement.Methods: A total of 8 groups of AIBC containing either gentamicin or vancomycin or both with different amounts of antibiotics (1 g, 2 g and 4 g) were tested on material properties, elution profiles, antibacterial activity and cytological toxicity.Results: A high dose of gentamicin and vancomycin AIBC (with 2 g gentamicin and 2 g vancomycin loaded) regiment showed acceptable compressive strength of 74.25±0.72 MPa. No cytotoxicity or antibacterial activity reduction was observed in any group tested in this study. The elution profiles indicated that incorporating 2 g vancomycin resulted in 4.77% (1049.57±3.74 μg) released after 28 days. However, after 2 g gentamicin was added, the vancomycin released was significantly reduced to 2.42% (532.24±1.77 μg) (p

Nowadays the field of application of products made from polymer materials is constantly increasing. These products find their wide application in the most high-tech industries such as automotive, aerospace and medical industry. Modern trends in the development of the automotive industry predicts that 75 % of the total car mass will be replaced with polymer materials by 2020 and other industries demonstrate similar trends. Regarding to this information, engineering companies that design parts of the automotive industry should have polymer material characteristics over an entire range of deformations up to destruction for their performance prediction. However, strength characteristics of products from polymers are different and depend not only on a polymer grade but also on technology used for part production. Existing literature review on this problematic area is rather rare. The purpose of this paper is to determine and analyze mechanical characteristics of widely used PPH030GP polymer obtained by extrusion and ABS, PLA polymers applied while manufacturing samples using an additive method (3D-printing) depending on the rate of high-elastic deformation. All the samples have been made according to the requirements of GOST 11262–80 and subjected to uniaxial stretching on a tensile machine UIT STM 050/300 at different speeds of clamp expansion. According to experimental results, stretching diagrams in conditional coordinates s–e have been obtained up to the point of failure for different rates of clamp expansion. It has been shown that while using the additive method, a direction of layers and adhesion between them, which depends on 3D-print parameters, have a significant effect on the part strength. Printing settings are indicated in accordance with the selected mode and a 3D-printer model. As a result of data processing, strength characteristics of PPH030GP polymer and ABS and PLA polymers have been determined to a sufficient extent, depending on the direction of printing layers and rate of high-elastic deformation. These data can be used to calculate strength of products by numerical methods and a finite element method in various software products.

Improving the mechanical and physical properties of bio-composite materials involves the incorporation of plant fibers such as Jute, Hemp, Kenaf, Ramie, Sisal, Linen, etc. The existence of Diss grass (Ampelodesmos mauritanicus) in abundance in the east of Algeria especially in Khenchela region and taking into account their mechanical resistance and their low density, which justifies their choice of use in composite materials. Tensile and hardness tests for different volume fractions (from 05% to 20%) of short fibers of Diss are performed. The increase in fiber content and their treatment improves the mechanical characteristics of the composite materials. These concentration levels are added to a Polyester resin matrix. Our work relates to the study of a composite material reinforced by a vegetable fiber of which different volume ratio of short Diss fiber are considered. The results collected are purely experimental. [ABSTRACT FROM AUTHOR]

Copyright of Tobacco Science & Technology is the property of Tobacco Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To further investigate differences of fracture behaviors and acoustic emission characteristics of rock under different strain rates, unconfined uniaxial compressive tests of thirty cylindrical specimens with 50 mm in the diameter and 100 mm in the height were performed within quasi-static strain rates of 10–5–10–2 s−1 by rock material testing system and multi-channel acoustic emission (AE) monitoring system. The uniaxial compressive strength, peak strain and elasticity modulus, failure mode, fractal dimension and equivalent average size of the rock fragments, and the three-dimensional spatial distribution of acoustic emission events were obtained and analyzed. The experimental results verify that the uniaxial compressive strength, elasticity modulus and peak strain are strain rate-dependent significantly. Particularly, with increasing strain rates, macroscopic failure modes present three types of single shear failure, multiple shear failure, and shear and tensile mixed failure, and the rock fragments show a smaller equivalent size and a larger fractal dimension, which resulted in a higher fragmentation degree. Besides, it is noted that the evolution process of acoustic emission ring-down count and spatial distribution of events under different strain rates are closely related to macroscopic failure modes. Furthermore, characteristic stresses based on the evolution process of acoustic emission ring-down count, such as the elastic stress, initiation stress and yield stress, were analyzed deeply at different strain rates. A simplified rock model consisting of discrete fracture network and equivalent elementary volume was proposed to discuss the effect of strain rate on energy accumulation and dissipation. Finally, to better reveal the micro mechanism of the effect of strain rates on rock mechanical behaviors, the microscopic fracture morphology was observed and characterized by means of scanning electron microscopy. The experimental results should be taken into account in underground mining, tunnel excavation and other rock engineering activities. [ABSTRACT FROM AUTHOR]

There is a big challenge to achieve a balance between mechanical characteristics and biological properties in biphasic calcium phosphate (BCP) ceramics. The present study investigated the effects of calcium oxide (CaO) addition on the sintering behaviors and biological performances of BCP ceramics. The characterizations of surface structure, phase composition and crystal structure demonstrated that the addition of CaO could stabilize calcium‐deficient hydroxyapatite (CDHA) phase and reduce grain size in BCP ceramics, so as to better mimic chemical composition and crystal structure of the natural bony minerals. Mechanical tests indicated that the addition of CaO could increase the compressive strength, flexural strength and fracture toughness of BCP ceramics, because of the enhanced crack deflection associated with a transgranular to intergranular cracking. Due to high content of CDHA phase, small grain size and slightly alkali environment, BCP ceramics with appropriate amount of CaO addition (2%) could promote the spreading and osteogenic differentiation of BMSCs. The strong bone‐like apatite formation ability predicted a good osteoinductive potential of BCP ceramics with CaO addition. In summary, these findings suggest that the addition of CaO offers a promising strategy for design and fabrication of BCP ceramics with superior mechanical and biological properties. [ABSTRACT FROM AUTHOR]

A series of tests were performed to investigate the macroscopic properties and the stabilization mechanism of calcium lignosulphonate modified expansive soil. Compared with natural soil, soil modified by 4% calcium lignosulphonate showed 56.5% increased 28 days unconfined compressive strength and 23.8% decreased free expansion rate. The X-ray diffraction analysis results indicate the existence of cation exchange and the reduction of montmorillonite interplanar spacing. The X-computed tomography results demonstrate that calcium lignosulphonate decreased the porosity and optimized the pore distribution. The calcium lignosulphonate also increased the stability of the suspension system according to the Zeta potential results. Moreover, the results of rheological tests show that the moderate amount of calcium lignosulphonate enhanced the yield stress and the plastic viscosity, proving the formation of a strong connection between soil particles. [ABSTRACT FROM AUTHOR]

The prospect of design of the nanostructured glass–ceramic materials from the standpoint of self-organization of dissipative structures is analysed. The feasibility of developing lithium-aluminium-silicate glass–ceramics in the fabrication of highly effective elements of protective structures is established. The importance of regulating the material nanostructure at the nucleation stage when high-strength glass–ceramic materials are created is determined. The criteria for the development of glass matrices are selected; the choice of composition and crystallization catalysts in the fabrication of glass–ceramic materials to protect special equipment is justified. Model glasses and materials based on them are synthesized, and the optimal compositions for the fabrication of glass–ceramic materials with a definite level of light transmission and the type of crystallization using glass and ceramic technologies are selected. The phase-formation features of the obtained glasses after melting and during the heat treatment are revealed. They consist in the formation of fluctuations and incipient of lithium metasilicate crystals with the subsequent formation of finely dispersed mass devitrification materials’ structures during heat treatment. The features of the nanostructure formation for developed lithium-aluminium-silicate glasses at the initial stages of nucleation are investigated. The mechanism of structure formation of lithium-aluminium-silicate glasses during heat treatment is established. It consists in the following sequential processes: the formation of sibotaxic groups in the glass melt, followed by the formation of nanoscale grain crystallization due to phase separation; the behaviour of self-organization of the structure with the formation of both lithium disilicate crystals with a size of 0.4 μm in an amount of 50 vol.% and β-spodumene with a size < 1 μm in an amount of 85 vol.% that is the key to their high strength and light transmission. For the developed glass–ceramic materials based on lithium-aluminium-silicate glasses, the formation of a dissipative metal structure using the phase-separation mechanism under conditions of low-temperature heat treatment allows their high performance properties (H = 8.9–9.0 GPa, HV = 8.74–8.9 GPa, K1C = 3.10–3.40 MPa.m1/2) to be ensured. This allows us to consider them promising when creating structures for the protection of special equipment. [ABSTRACT FROM AUTHOR]

Nowadays, every farmer is faced with the task of providing their livestock with high-quality food that will contribute to their rapid growth and health. It is also common knowledge that large farms have more opportunities to implement their projects and put new technologies and gadgets into operation. The presented device makes it possible to obtain a product of processing soy grain into soy milk, soy cheese "tofu", soy protein base for preparing feed for farm animals and poultry in small farms. This article explains the experimental method for finding the optimal values of the speed of rotation of the movable disk, the temperature of the extractant, the gap between the movable and stationary disks of the shredder, and the ratio of the hydromodule. Optimal values are those that contribute to the maximum protein yield. Experimental factors: ambient temperature from 17°C to 22 °C, barometric pressure from 93325 PA to 96658 PA, relative humidity from 65% to 85%. Protein extraction in an emulsion is based on the physical and chemical properties of the diffusion of dissolved organic compounds, with water as the extractant. As a result, methods have been found for the effective production of protein from soy grains, which can increase the yield of the suspension to 24-28 Gr. This is the most productive way to produce protein for feed modification using this device. [ABSTRACT FROM AUTHOR]

Copyright of Tobacco Science & Technology is the property of Tobacco Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The durability of soft soil stabilized by Portland cement-soda residue (PC-SR) subjected to dry-wet cycles remains relatively unclear now despite previous studies have extensively examined the engineering attributes of soft soil stabilized by PC-SR. Therefore, this study delineates the impacts of dry-wet cycles on the macro and micro features of soft soil stabilized by PC-SR. Based on the orthogonal test design, the unconfined compressive tests, X-ray diffraction test, scanning electron microscopy, and mercury intrusion porosimetry tests were conducted to analyze the impact of dry-wet cycles on the strength, mineral components and microstructural characteristics of stabilized soil cured for 28 days. The experimental findings revealed that the strength of soil stabilized by PC-SR initially ascends and subsequently declines after dry-wet cycles. At the microscale, the tests showed that the dry-wet cycles transform the microstructure of stabilized soil by damaging the cementation among soil particles, expanding the pore diameter, and forming macropores and fissures. Combined with macro and micro results, it is shown that in the initial stage of the dry-wet cycle, the continuous hydration reaction promotes the increase of the microstructure density of solidified soil. However, under the continuous influence of the dry-wet cycle, the dissolution and expansion of mineral components lead to the degradation of the microstructure, which leads to the decline of the macro strength of the stabilized soil, further revealing the mechanism of the macro strength of the stabilized soil rising first and then decreasing. This study showed that Portland cement-soda residue treatment was efficient to prevent the deterioration from the dry-wet cycles. • Investigated the durability of soft soil stabilized by Portland cement-soda residue (PC-SR) under the influence of dry-wet cycles. • Utilized advanced microscopy techniques to analyze the changes in mineral components and microstructural characteristics during dry-wet cycles. • The findings hold significant implications for engineering practices involving soft soil stabilization, providing valuable information for optimizing durability and strength under cyclic environmental conditions. [ABSTRACT FROM AUTHOR]

The objectives of this study were to characterize the compaction and mechanical characteristics and frost resistance of vibration-compacted cement–fly ash slurry (CFAS) and cement–fly ash-treated macadam (CFATM) mixtures and recommend the optimal ratio and dosage of cement–fly ash (CFA) based on laboratory compaction experiments, unconfined compressive testing, indirect tensile testing, and frost resistance testing. The effects of the CFA ratio and dosage, curing age, and gradation type on the mechanical strength and frost resistance were analyzed, and strength prediction equations were presented. Then, the optimal CFA ratio and dosage are recommended. The results show that the mechanical strength of CFAS and CFATM mixtures increased nonlinearly with increasing curing age. Gradation type, CFA ratio, and CFA dosage affected the conventional, initial, and ultimate mechanical strengths of these mixtures. A CFATM mixture cured for a longer duration with self-developed skeleton-dense gradation and the addition of less fly ash exhibited better frost resistance. To maximize the mechanical strength of CFAS and CFATM mixtures, the CFA ratio should not exceed 1:1 and 1:1–1:1.5, respectively. In addition, 3.5%–4.0% cement and 4.0%–7.0% fly ash should be used in the CFATM base or subbase to obtain optimal results. This paper provides a new option for the design of CFAS and CFATM mixes. • Engineering characteristics of VVCM-compacted CFAS and CFATM were studied. • Strength growth equations for VVCM-compacted CFAS and CFATM were established. • Various factors affecting initial and ultimate mechanical strengths were studied. • Optimal cement–fly ash ratio and dosage were recommended for CFAS and CFATM. [ABSTRACT FROM AUTHOR]

Studies of catalog data and parameters of substitution schemes for asynchronous motors of the air series with a short-circuited rotor have been performed in order to obtain general laws and analytical expressions depending on the engine power. In the Mathcad computer-aided design system, 32 engines were studied, and machines with a synchronous speed of 1500 rpm were taken as the main ones. Catalog data in the reference literature, according to manufacturers and other sources, differ significantly from each other, and so analytical expressions that reflect their average values are needed. General regularities and analytical expressions for determining the necessary parameters are obtained. An approximate method for calculating mechanical characteristics is proposed that takes into account the skin effect and current displacement in the rotor winding, which allows obtaining mechanical characteristics with an increased starting torque. [ABSTRACT FROM AUTHOR]

• An energy harvesting type piezoelectric ultrasonic actuator (H-PUA) is proposed. • It can harvest the stator vibration energy and covert it into electric energy. • Numerical and experimental research on its mechanical and energetic characteristics. • The mechanical characteristics such as the no-load speed and stalling torque reach 112 rpm and 0.78 Nm, respectively. • The harvesting output power of a sector area reaches 54 mW, which can power some low-power electric devices. Piezoelectric ultrasonic actuators (PUA) are fascinating and precision-controlled actuators in some mechatronics systems. This study proposed an energy harvesting type piezoelectric ultrasonic actuator (H-PUA) and investigated its mechanical and energetic characteristics. The proposed H-PUA has a sandwich-type stator composed of a metal body, an exciting piezoelectric (PZT) ring and a harvesting PZT ring. The exciting PZT ring bonded on the bottom surface of the stator was used to produce a traveling wave, and the harvesting PZT ring bonded on the top surface of the stator was used to harvest the vibration-induced energy of the stator and convert it into electric energy. Sensitivity analysis method was used to optimize the stator structure. Finite element analysis using ANSYS software was performed for both the mechanical and energetic characteristics of the new actuator. A prototype H-PUA was fabricated and subsequently used to test the mechanical and energetic characteristics. When the rotor torque is zero and the pre-pressure is 100 N, the prototype H-PUA has mechanical output characteristics of no-load speed 112 rpm and stalling torque 0.78 Nm when the exciting voltage amplitude is 152 V 0−p with frequency 36.0 kHz. The maximum harvesting output power of a sector area of the harvesting PZT ring reaches 54 mW when it is connected to an optimized load resistance 11 kΩ. Experiments have shown that the harvesting output energy can fully meet with the power supply demands of some low-power (i.e., mW/μW level) mechatronics systems, such as LED. [ABSTRACT FROM AUTHOR]

In order to understand the rupture mechanism of rock and coal samples with holes, the acoustic emission (AE) tests of rock and coal samples with holes under uniaxial compression are done. Through the AE tests, the basic mechanical and AE variation rule of two samples in the total rupture process are obtained, the dynamic rupture process was observed and finally the spatial evolution and multi-fractal characteristic of AE are analyzed. The results show that the variation rule of AE events of two samples are coincident with the variation rule of stress. The uniaxial compressive strength of a rock sample with a hole is about five times than that of a coal sample with a hole, and the maximum AE pulsing counts (AEPC) of a rock sample with a hole is much larger than that of a coal sample with a hole. Due to the variation of lithology, the dynamic rupture process and the spatial evolution rule of AE events of rock and coal samples with holes are obviously different. But the distributions of the three-dimensional locations of the two samples are coincident with the macroscopic rupture morphology. Both of them have multi-fractal characteristic in the process of rupture, the multi-fractal spectrum width Δ f (α) at the time of rupture is smaller than that before rupture and the Δ f (α) before rupture is smaller than that after rupture. This indicates that the energy (E) before and after rupture is smaller than that at the time of rupture, the E after rupture is smaller than that before rupture and the E of a coal sample with a hole in each stage is less than that of the corresponding stages of a rock sample with a hole. [ABSTRACT FROM AUTHOR]

Based on linear elastic theory, the concrete cracking problem of link slab on simply supported beam bridge was explored and theoretical analysis of bridge link slabs were carried out. Meanwhile, the formulas for calculating the stress of link slab were deduced and the cause for continuous damage of bridge deck was quantitatively analyzed. On the base of analysis of its failure mechanism, a new type of steel-concrete composite flat link slab was proposed. The results of full-scale model tests and finite element (FE) analysis indicated that it can alter the transfer path of internal forced inside the link slab and then concrete cracking can be prevented effectively. It was found that the main factors to link slab failure were influentially descending from girder end upturning, longitudinal tensile action and girder end rotation. Furthermore, the unbonded region between girder and link slab can effectively decrease the continuous stress and then alleviate the damage to bridge deck. All those results in this paper can be used as a reference and guidance for further research and development of new type of bridge link slab and jointless bridge. [ABSTRACT FROM AUTHOR]

The authors present a methodology for the calculation and optimisation of regulation laws that apply to electronically commutated synchronous motors with predefined characteristics. It is shown that the synchronous electronically commutated motors can provide predefined characteristics with the maintenance of high energy performance by simultaneously regulating supply voltage, excitation current and load angle. [ABSTRACT FROM AUTHOR]

The clamping force is the most important parameter of Press Pack IGBTs (PP IGBTs) as it not only affects the electrical, thermal, and mechanical characteristic, but also the long lifetime reliability. Too little clamping force increases the contact resistance and junction temperature. Too much clamping force makes the silicon chips mechanical damage. However, it is quite complex and time-consuming to obtain the influence of the clamping force on the long-time reliability through the power cycling test because that many tests are needed to execute under a large range of clamping forces. Here, a single IGBT chip sub-module is proposed to simulate the long lifetime reliability through the finite element method under various clamping forces. Both the thermal contact resistance within different contact interfaces that affects the junction temperature of silicon chips a lot and the elastic-plastic model that affects the lifetime of specific material layers are considered in this finite element model to make it more accurate. The combination of Coffin–Mason and Basquin model is proposed to obtain the power cycling lifetime of the sub-module based on simulation results. A clamping force range is obtained and this also gives a guideline for the power cycling test. [ABSTRACT FROM AUTHOR]

Honeycomb sandwich panels (HSP) have exhibited significant advantages in light weight and energy absorption, and they have been widely applied in the automotive, aerospace, transportation and defense industries. Rather than restating details of the existing standard regular hexagon HSP (R0-HSP), this paper introduces single-rib reinforced regular hexagon HSP (R1-HSP) and double-rib reinforced regular hexagon HSP (R2-HSP). The mechanical characteristics of these three structures are first investigated by series full-scale elaborator models through LS-DYNA. It is found that the R1-HSP has the best crashworthiness performance under axial impact regarding specific energy absorption per unit (SEAm and SEAv) when the peak crashing stress (σpeak) is less important. Secondly, the thickness matching effect between stiffener and cell wall is analyzed with equivalent apparent density index to evaluate the contribution of the change of deformation model to the general mechanical properties. Consequently, stiffener thickness of 2.0 times and 1.5 times that of cell wall are found to be the most optimal options for R1-HSP and R2-HSP, respectively. To optimize the crashworthiness of the R1-HSP, optimal Latin hypercube design method is used for selection of sampling design points in the design space. And in the meantime, an accurate surrogate modeling method, or more specifically named as response surface method, is adopted to formulate the SEAm, SEAv and σpeak functions. The results yielded from the optimization indicate that the R1-HSP is superior to R0-HSP both in SEAm and SEAv under the same limitation of σpeak. This research is significant in providing technical support in the extended applications of different HSPs used as crashworthiness structures, and it has essential reference value in low volume and low mass energy absorber design.

Aim. Development of a method for calculating mechanical characteristics of three-phase induction motors with single-phase power supply. Methods. The developed algorithm is based on the high-adequacy mathematical model of motor and projection method for solving the boundary problem for equations of electrical circuits balance presented in the three-phase coordinate system. As a result of asymmetry of power supply to the stator windings, in steady state, flux-linkage and current change according to the periodic law. They are determined by solving the boundary problem. Results. The developed mathematical model allows determining periodic dependence of coordinates as a function of slip and, based on them, mechanical characteristics of motors. Academic novelty. The developed method relies on a completely new mathematical approach to calculation of stationary modes of nonlinear electromagnetic circuits, which allows obtaining periodic solution in a timeless domain. Practical value. Using the developed calculation algorithm, one can select capacitance required to start an induction motor with single-phase power supply and calculate static mechanical characteristics at a given capacitance.

With the increased application of ultrasonic motors, it is necessary to put forward higher demand for the adaptability to environment. Impact, as a type of extreme environment, is widespread in weapon systems, machinery and aerospace. However, there are few reports about the influence of impact on an ultrasonic motor. This article aimed to study the reasons for the performance degradation and failure mechanism of an ultrasonic motor in a shock environment. First, a finite element model is established to observe the dynamic response of ultrasonic motor in a shock environment. Meanwhile, the reasons of the performance degradation in the motor are discussed. An impact experiment is carried out to test the influence of impact on an ultrasonic motor, including the influence on the mechanical characteristic of an ultrasonic motor and the vibration characteristic of a stator. In addition, the protection effect of rubber on an ultrasonic motor in a shock environment is verified via an experimental method. This article reveals the failure mechanism of ultrasonic motors in a shock environment and provides a basis for the improvement of the anti-impact property of ultrasonic motors.

The clamping force is the most important parameter of Press Pack IGBTs (PP IGBTs) as it not only affects the electrical, thermal, and mechanical characteristic, but also the long lifetime reliability. Too little clamping force increases the contact resistance and junction temperature. Too much clamping force makes the silicon chips mechanical damage. However, it is quite complex and time-consuming to obtain the influence of the clamping force on the long-time reliability through the power cycling test because that many tests are needed to execute under a large range of clamping forces. Here, a single IGBT chip sub-module is proposed to simulate the long lifetime reliability through the finite element method under various clamping forces. Both the thermal contact resistance within different contact interfaces that affects the junction temperature of silicon chips a lot and the elastic-plastic model that affects the lifetime of specific material layers are considered in this finite element model to make it more accurate. The combination of Coffin–Mason and Basquin model is proposed to obtain the power cycling lifetime of the sub-module based on simulation results. A clamping force range is obtained and this also gives a guideline for the power cycling test.

This paper investigates of a kind of five-phase dual-rotor permanent-magnet synchronous motor (DRPMSM), which contains dual rotors and a single stator. This kind of motor has the potential advantages of high power density, high reliability and high efficiency, which make it more appropriate for using in electric vehicles (EVs). In order to evaluate the most suitable power level for this kind of structure, the electromagnetic, the thermal and the mechanical characteristics are investigated in this paper. The length to diameter ratio of motors is researched to obtain the highest power density and then the optimum ratio is obtained. Based on the optimum ratio, the thermal characteristics are researched under natural condition and forced-air cooling condition with different wind speeds. In addition, the mechanical characteristics are analyzed under no-load and different loads conditions, respectively. All of the results are analyzed by two-dimension (2-D) and three-dimension (3-D) finite element method (FEM) simulation, which provide a good reference to select suitable power level for this kind of motor structure. Finally, a DRPMSM prototype is manufactured and tested. The experimental results effectively verify the FEM results.

One of the most important issues for treatment of paper works is use of long-lasting (endurable) materials. In this study, Mechanical properties of Bacterial cellulose Nanofibers (BCN) for preservation of paper works are investigated. For this purpose, Suspension of BCN in Klucel-G polymeric matrix with doses of 0.5, 1, and 2 Wt% of dry matter were prepared and were coated on the pure cellulose paper (filter paper) by hydro-soluble casting method, and then tensile strength (TS) and folding endurance (FE) mechanical tests were performed. Also, in order to evaluate durability properties (long-lasting) of the cellulose fiber bionanocomposite, accelerated aging test was conducted in moist heat conditions. After performing mechanical test, obtained results were investigated and it was observed that the presence of this nanofibers in Klucel-G matrix, although lowers the initial mechanical properties (before aging), but increases durability of bio-nanocomposite compared to pure Klucel-G polymer matrix, and hence, as protective coatings, results in prevention of early aging. As a result, this prepared nanocomposite would have applications as a new reinforcing and endurable polymeric coating for preservation of paper works and prevention from further loss of their strength, and also there would be less need for retreatment. [ABSTRACT FROM AUTHOR]

Non-pneumatic tires overcome the hidden dangers of puncturing, deflating and bursting of conventional pneumatic tires, and improve the driving safety and mobility of vehicles. However, due to stress concentration, variable load and impact, the critical components of non-pneumatic tires may still fail. In this paper, the influence of local damage on the static and dynamic characteristics of the honeycomb non-pneumatic tire was studied by using the finite element method. Firstly, according to the working principle and structural characteristics of the honeycomb tire, the finite element model of the tire was established, and its static characteristics in good condition state were analyzed. Then, the failure mode and danger area of the honeycomb tire were discussed, and the vulnerable parts of the honeycomb tire were determined. Finally, the static and dynamic characteristics of the honeycomb non-pneumatic tire in local damage conditions were simulated. The tire stiffness, grounding pressure, and vibration characteristics with different damage degrees were analyzed qualitatively. The results show that the spoke damage has different effects on the static and dynamic characteristics of non-pneumatic tires, including vertical stiffness, ground pressure and natural frequency. The research results provide a basis for structural design and optimization, health monitoring, and fault diagnosis of the non-pneumatic tire. • The effect of damage degrees on the tire stiffness, grounding pressure, and vibration characteristics are analyzed qualitatively. • With the aggravation of the damage degree, the contact pressure of honeycomb tire first decreased slightly and then increased significantly. • With the increase of tire damage, the natural frequency of honeycomb tire shows an obvious downward trend. • Structural damage of spokes will significantly reduce the radial stiffness of the honeycomb tire, and increase the shear layer stress. [ABSTRACT FROM AUTHOR]

Tensile tests were performed on bismuth single crystals in the [0001] ( c-axis), [2 $$\bar{1}\bar{1} $$ 0] ( a -axis), [10 $$\bar{1} $$ 0] and [1 $$ \bar{1} $$ 00] directions of bismuth single crystals to investigate the influence of temperature on plastic deformation behavior. The plastic deformation at 298 K was caused by slip on the secondary slip system in the [0001] direction, or by twinning and slip deformation in twins subsequent to the twining deformation in the [2 $$\bar{1}\bar{1} $$ 0] direction. Those mechanisms resulted in ductile characteristics in tension. Only deformation twinning, however, was observed along the [10 $$\bar{1}$$ 0] and [1 $$\bar{1} $$ 00] directions, which lead to brittle fracture. At elevated temperature (423 K), deformation twinning was not found to occur along any of the examined directions. Crystallographic slip was the predominant deformation mechanism along the [2 $$\bar{1}\bar{1} $$ 0], [10 $$\bar{1} $$ 0] and [1 $$\bar{1} $$ 00] directions at 423 K. This is attributed to the activation of the {1 $$\bar{1} $$ 02}<11 $$\bar{2} $$ 0> or {1 $$\bar{1} $$ 02}<1 $$\bar{1} $$ 0 $$\bar{1} $$ > slip system which are inactive at 298 K. Along the [0001] direction at 423 K, the {0 $$\bar{1} $$ 11}<10 $$\bar{1} $$ 1> was active and its critical resolved shear stress ( τ ) does not coincide with that corresponding to the {1 $$\bar{1} $$ 02}<11 $$\bar{2} $$ 0> and {1 $$\bar{1} $$ 02}<1 $$\bar{1} $$ 0 $$\bar{1} $$ > systems. Therefore, it can be concluded that difference in τ between slip systems causes anisotropy in mechanical behavior at 423 K. [ABSTRACT FROM AUTHOR]

The paper proposes an explicite formula for determining the critical slip value of an induction squirel cage motor based upon five parameters. Three of these parameters - rated slip, rated and breakdown torque are known by catalogue data. Two missing parameters are the arbitrary slip between the rated and critical slip value and the corresponding torque value. These two parameters are to be experimentaly obtained. The breakdown torque value given by catalogue data is usually less accurate than the rated torque value. The proposed formula gives the possibility of analysing the error distribution of the critical slip value obtained from catalogue and measured data in comparison with the values obtained from the mechanical characteristic based on the physical parameters of an induction motor.

The key to the prevention and control of coal and gas dynamic disaster is the mastery of its mechanism. However, plenty of factors induce coal and gas dynamic disasters, and the mechanism is complex, especially the dilatancy of coal and rock by mining. The main control factors of dynamic disasters change, thereby making such disasters difficult to manage. The mechanism of dilatancy caused by coal crack was analyzed based on the physical mechanical characteristics of gassy coal to explore the mechanism of coal and gas dynamic disaster induced by coal dilatancy in the working face. The energy evolution characteristics of the coal face during dilatancy stage were studied, and the safety evaluation index of disaster caused by the dilatancy was presented. Results show that the coal dilatancy in the working face depends on the force environment and the physical mechanical properties of coal. With the increase in initial gas pressure, elastic modulus, compressive strength, and critical stress value of the dilatancy are reduced, resistance to deformation and destruction of the coal containing gas is weakened, and the mechanical phenomenon of dilatancy easily occurs. The change gradient of gas pressure and gas expansion energy can increase with the increase in initial gas pressure in the dilatancy moment. The safety evaluation index increases from 0.09 to 1.29 when the initial gas pressure reaches 3 MPa. This finding shows that the safety evaluation index of disaster caused by the dilatancy has a nonlinear positive correlation with gas pressure. The dynamic disaster can only be caused by the effect of the mining action at a gas pressure of 3 MPa. This study provides a theoretical reference for the prevention and control of coal and gas dynamic disasters. [ABSTRACT FROM AUTHOR]

In this investigation, several quasi-static mechanical tests on cylindrical Lithium-ion battery cells are performed to reveal the essential mechanical properties of the jellyroll. Utilizing the plastic flow rule, it was found that the homogenized mechanical properties of the jellyroll are similar to the clay (clay-like). According to the mechanical characteristics of clay, a linear equation was proposed to describe the nonlinear constitutive behavior of the jellyroll. An explicit finite element model for the jellyroll that could accurately predict its mechanical response during deformation using crushable foam constitutive behavior was established in HyperWorks/LS-DYNA to validate the proposed approach. The simulation results of various loading cases are in good agreement with the corresponding experimental results. By proposing a micro stress area, the stress-strain relations for components of the jellyroll were calculated individually. A finite element model was developed to compare the mechanical properties of the jellyroll by changing the thickness of different components, including the metal foils and the active particles. The simulation results indicate that the change of the thickness of the coating active particles will influence the mechanical properties of the jellyroll. [ABSTRACT FROM AUTHOR]