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In additive manufacturing, also called 3-D printing, one of widely used materials is polylactide thermoplastic polymer (PLA) by means of the fused deposition modeling. For weight reduction purposes, infill density is an often used feature in slicing for 3-D printing. We aim at investigating the effect of infill density on the mechanical properties of structures. Therefore, we demonstrate how to prepare tensile specimens and test them by a universal testing machine. Results are collected by a so-called digital image correlation method. As infill density increases, from 10% to 100%, the nominal strain at break decreases from about 2.1% to 1.2%, respectively. In other words, the material becomes more ductile by decreasing the infill density of PLA material, which is possible to justify with an effect of the microstructure created by the infill density. Furthermore, we discuss a possible material model fitting all the presented results and report that a hyperelastic material model is needed for the PLA. We utilize Neo-Hookean, Mooney–Rivlin, and Yeoh models, all for different infill densities. All three models show a fairly good agreement to the experimental data. Neo-Hookean model has an advantage of only one parameter, which increases monotonously with infill density.

Biocompostable poly (glycolic acid) (PGA) crystallizes slowly under fast cooling condition, leading to poor mechanical performance of the final products. In this work, a self-nucleation (SN) route was carried out to promote the crystallization of PGA by regulating only the thermal procedure without any extra nucleating agents. When self-nucleation temperature (Ts) decreased from 250 oC to 227 oC, the nuclei density was increased, and the non-isothermal crystallization temperature (Tc) of PGA was increased from 156 oC to 197 oC and the half-life time (t0.5) of isothermal crystallization at 207 oC was decreased by 89%. Consequently, the tensile strength and the elongation at break of the PGA were increased by 12% and 189%, respectively. According to the change of Tc as a function of Ts, a three-stage temperature domain map (Domain I, II and III) was protracted and the viscoelastic behavior of the self-nucleation melt and the homogeneous melt was studied. The results indicated that interaction among PGA chains was remained in Domain IIb, which can act as pre-ordered structure to accelerate the overall crystallization rate. This work utilizes a simple and effective SN method to regulate the crystallization behavior and the mechanical properties of PGA, which may broaden the application range of resulting materials.

BACKGROUND: A class of additive manufacturing technologies called Laser powder bed fusion (LPBF), which allows fabricating metallic components with complex geometries in near-net-shape, can be employed for fabricating patient-customized orthopaedic implants. Selection and optimization of the LPBF process parameters are critical to achieving the required biomechanical properties and fabricability of such implants. METHODS: The process parameters of direct metal laser sintering, the most widely used LPBF process, were optimized for fabricating Ti6Al4V ELI orthopaedic implants, based on ASTM and ASM standards. The parameters included Laser power, Laser velocity and hatch distance, which were varied using Taguchi approach. A multi-criteria decision-making technique (TOPSIS) was employed to optimize the process parameters considering yield and ultimate tensile strength, percentage elongation, part density, volumetric energy density and printing time. In-vitro cytotoxicity and in-vivo muscle implantation were performed on the optimized samples for determining the suitability of the parameters for biomedical applications. RESULTS: A combination of medium laser power, higher laser velocity, and lower hatch distance with values 200 W, 2200 mm/s and 0.08 mm, respectively, was found to be suitable for producing implants. Based on the type of LPBF technology in use, an implant manufacturer can select the initial set of parameters using a similar approach and improve them further based on experimental results. CONCLUSION: The optimized parameters were found to be suitable for developing orthopaedic implants, in terms of physical, mechanical and biological criteria. The methods and results presented in work are expected to assist the implant manufacturers in meeting the expected user requirements and quality standards. GRAPHICAL ABSTRACT: [Image: see text]

Biodegradable polymer plays a major role in Additive Manufacturing (AM) technologies due to its novel characteristics that include its complete degradability and eco-friendly nature. The present research work aims to obtain smooth and stable Poly Lactic Acid (PLA)/Eggshell particles (E) composite filaments with enhanced mechanical and thermal properties for additive manufacturing applications. Composite filaments were developed by varying the ratio of E/PLA to 4-6-8-10-12 weight percentages (wt.%) using a single screw extruder. A study of physical, chemical, mechanical, and thermal properties for the manufactured filaments was made. The extruded filaments were subjected to thermal analysis using Melt Flow Index (MFI) to obtain the optimum value for AM applications. XRD analysis made on 4 wt.% eggshell revealed a higher crystallinity than neat PLA. The thermal results of neat PLA and various weight compositions of E revealed there is a decrease in thermal stability and thermal decomposition due to an increase in filler content. 4 wt.% of E shows the good tensile strength of 49.29 MPa with smooth and stable E/PLA composite filaments during extrusion. The SEM images of the composites revealed the interaction between the filler and the matrix. Based on the experimental work, it is observed that the addition of eggshell powder into the PLA increases the mechanical properties with an optimum content of 4 wt.% of E.

Nitrogen is an alloying element that can significantly improve the yield strength of steel by means of interstitial solid solution strengthening. The effects of quenching temperature on the evolution of second phase and grain size were investigated, as well as tensile properties, impact energy and hardness of a new nitrogen-alloyed Fe-Cr-Mo-V-N steel. The results show that with the increase of quenching temperature, the number and size of the second phase decrease as the high temperature promotes the dissolution and refinement of the second phase. For instance, the number of second phase M23C6 particles decreases gradually with temperature increasing. When the quenching temperature reaches 1050 °C, the grain is refined. Under the same tempering treatment, with the increase of quenching temperature, the tensile properties, impact energy and hardness increase first and then decrease. When the quenching temperature is 1050 °C and the tempering temperature is 180 °C, the obtained mechanical properties are the best. Under this condition, the tensile strength at room temperature is 2110 MPa, the yield strength is 1620 MPa, and the impact energy is 29.1 J, respectively.

Laser technology has many advantages in welding for the manufacture of EV battery packs. Aluminum (Al) and copper (Cu) are welded using a dual laser beam, suggesting the optimum power distribution for the core and ring beams. Due to the very high reflectance of Cu and Al exposed to near-infrared lasers, the material absorbs a very small amount of energy. Compared to single beam laser welding, dual beam welding has significantly improved surface quality by controlling surface solidification. The study focused on the quality of weld surface beads, weld properties and tensile strength by varying the output ratio of the core beam to the ring beam. Optimal conditions of Al6061 were a 700 W core beam, a 500 W ring beam and 200 mm/s of weld speed. For the C1020P, the optimum conditions were a center beam of 2500 W, a ring beam of 3000 W and a welding speed of 200 mm/s. In laser lap welding of Al-Al and Al-Cu, the bead width and the interfacial bead width of the joint increased as the output increased. The penetration depth did not change significantly, but small pores were formed at the interface of the junction. Tensile tests were performed to demonstrate the reliability of the weld zone, and computer simulations provided analysis of the heat distribution for optimal heat input conditions.

Microstructure and mechanical properties of welded joints of X80 pipeline steel were investigated to determine the best welding process. Then, numerical simulation and indentation tests were conducted to study the reasonable circumferential distance between two joint junctions of straight weld and girth weld. Results indicate that under 7-layer welding process, the microstructure in weld metal is the finest, the largest content of granular bainite and ferrite was in coarse-grained region and the smallest polygonal ferrite was in fine-grained region, which leads to the desirable tensile strength and impact toughness. For pipe connections, too close circumferential distance between two joint junctions is not conducive to maintaining the performance of pipeline, and the distance of 100 mm is recommended. In addition, ultrasonic impact treatment was applied on weld toes to improve the fatigue properties of welded joints, and surface strengthening mechanism and fatigue fracture mechanism were studied.

A series of TA15 specimens with different process parameters were built by electron beam melting in this paper to systematically investigate the relationship of material-process-microstructure-mechanical properties. A quantitative mathematical model of yield strength and Vickers hardness with respect to α lath thickness was established. Microstructure analysis results showed that the microstructure of TA15 titanium alloy were basketweave microstructure, lamellar microstructure and bimodal microstructure depending on process. In general, the yield strength, Vickers hardness and α plate thickness are correlated with the Hall-Petch equation, but the mathematical model established in this paper has a better fitting effect. Process parameters affect the mechanical properties of the TA15 titanium alloy by affecting α lath thickness, and speed factor has the greatest influence on α lath thickness. The tensile properties of TA15 titanium alloy are as well as, if not better than, that of TA15 titanium alloys with tri-modal microstructure.

In this study, microstructure and mechanical properties of thin wall austempered and intercritically austempered ductile iron with a chemical composition of 3.37%C, 2.7%Si, 0.30%Mn, 0.01%S, 0.01%P, 0.47%Cu, and 0.0371%Mg were investigated. Thin ductile iron samples with different thicknesses of 5, 10, and 15 mm were cast and then heat treated with two different austempering techniques. The first sample was austenitizing below upper critical temperature at 810 °C for an hour and then rapidly quenched in a salt bath at 375 °C and held for 1 h (IADI). The second treatment was carried out at austenitizing temperature of 900 °C, which was above upper critical temperature, for an hour and then rapidly quenched in a salt bath at 375 °C for 1 h (ADI). The mechanical properties of the austempered and intercritically austempered thin wall samples were evaluated and compared to the as-cast samples. The fatigue properties of all samples were simulated using ANSYS software, and the best condition was experimentally tested using plane bending fatigue testing machine. Maximum ultimate strength (1056) MPa and hardness (396 HV) were obtained for 5 mm ADI sample. Maximum impact toughness (43 J) was achieved for 15 mm IADI sample due to existing proeutectoid ferrite in matrix. Maximum simulated fatigue strength (435 MPa) was reported for 5-mm ADI sample and minimum simulated fatigue strength (160 MPa) was registered for as-cast DI sample. For both ADI and IADI castings, fatigue strength decreased with increasing sample thickness. For 10-mm ADI sample, the simulated fatigue strength was (407 MPa) which was close to the experimental result (417 MPa).

Waterborne polyurethane (WPU) is widely applied in many fields; however, it is limited by its drawback of low mechanical strength and short lifespan. Polymer nanocomposites have been developed for many years to enhance the mechanical behavior of materials. Nevertheless, obtaining nanofillers with even dispersion to obtain improved mechanical performance is difficult. To solve the above problems, silica nanoparticles modified by furfuryl (furan@SiO2) were synthesized according to the sol–gel process. By introducing furan@SiO2 into a maleimide-terminated waterborne polyurethane matrix, a self-healing system was constructed through a DA/retro-DA process among furan groups and maleimide-terminated waterborne polyurethane, and a series of WPU films with different furan@SiO2 (WMPUS-x) contents were prepared. The structure of furan@SiO2 was clearly corroborated by TEM, SEM, FTIR, etc. Moreover, confirmed by tensile tests, the mechanical properties of all WPU samples were significantly improved due to the addition of rigid furan@SiO2, and their first self-healing efficiencies were all higher than 88%. In this article, a series of thermo-driven self-healable organic/inorganic nanohybrid polyurethane (WMPUS-x) films were prepared with different addition amount of furfuryl modified silica nanoparticles (furan@SiO2). The self-healable system was constructed via a DA/retro-DA process among furan@SiO2 and maleimide-terminated waterborne polyurethane. The results exhibited the addition of furan@SiO2 enhanced the mechanical behavior of all WPU samples.

Graphene oxide nanosheets reinforced Cu matrix composites were prepared using ball milling process and spark plasma sintering (SPS). Effects of ball milling times on morphology of composites powders were studied. Furthermore, microstructure evolution and properties of sintered composites were investigated. Results show that the size and shape of the composites gradually transformed from regular sphericity to flake with the increase in ball milling times. Correspondingly, the average flake diameter of Cu alloy powders increased gradually from 7.2 ± 0.5 to 25.0 ± 1.0 μm. Compared with the matrix alloy, the tensile strength of the composites increases significantly and the elongation decreases gradually. For 20 h of ball milling, the yield strength of composites increased by 35% from 126 to 170 MPa, and elongation decreases from 44 to 31%. However, for 60 h of ball milling, the tensile strength and yield strength increased to 290 and 211 MPa, respectively, while the elongation significantly descends. Besides, during the ball milling, the conductivity of composite gets a slight decrease owing to the increasing degree of powder defects.

This study aims to compare the microstructure of 17–4 PH stainless steel (SS) manufactured via laser powder bed fusion (L-PBF) and laser powder directed energy deposition (LP-DED) in non-heat treated (NHT) and heat treated conditions. In addition, the room-temperature tensile behavior of heat-treated L-PBF and LP-DED 17–4 PH SS has been investigated and compared with that of the wrought counterpart with the same heat treatment conditions. The results show that the L-PBF specimens have a finer microstructure (ferrite + lath martensite) than the LP-DED ones (massive ferrite + Widmanstatten ferrite) in NHT condition. Electron backscatter diffraction analysis shows that the L-PBF and LP-DED specimens have twin-based substructure lath martensite after heat treatment. Despite the lower tensile strength of the LP-DED specimens compared with the L-PBF ones, the ductility of peak-aged LP-DED specimens was reduced due to the presence of the δ-ferrite phase having a significant plastic deformation incompatibility with the martensite.

The limited applicability of very high dielectric permittivity ceramic materials such as copper calcium titanium oxide, commonly known as CCTO (er = 100,000 at room temperature and nearly independent of frequency from 1 Hz to 1 MHz), could be improved through the fabrication of polymer matrix composites. Ceramic is brittle while polymers are materials that are ductile and have excellent flexibility but low er. Another contrast between the two materials is the fabrication process where ceramic, specifically, requires pressing and a high sintering temperature. Hence, the right combination of ceramic and polymeric materials should theoretically produce a composite with excellent mechanical and electrical properties. Therefore, a study on CCTO ceramic powder blended with 25 mol% of epoxidised natural rubber (ENR-25) was carried out. The CCTO powder was initially synthesised through solid-state reaction followed by compounding with ENR-25 formulations with different CCTO loadings (0, 20, 40, 60, 80, 100, and 120 phr) in an internal mixer. Small blocks of the composite were cast into ~ 2 mm of mould thickness and then hot compressed into square shapes. Samples were characterised by curing, mechanical, electrical, and microstructural properties. As a result, the addition of CCTO was found to have lowered the curing time, i.e. tc90 at 20 phr, compared to composites without CCTO loading. Then, the curing time gradually increased with filler loading from 2.05 to 2.48 at 20 to 120 phr loading, respectively. Mechanical testing of the composites showed an increase in tensile strength from 5.91 to 16.46 MPa. However, with content higher than 40 phr content, the tensile strength's magnitude gradually decreased with increasing filler loading from 13.63 to 6.49 MPa. In comparison, hardness properties increased with an increase of filler loading from 30.5 to 44.7 Shore A. Meanwhile, LCR meter showed that increased CCTO content could improve er value from 6.134 to 12.114 at 75 kHz and decrease the dielectric loss (tan δ) from 0.179 to 0.150 at 2 MHz. The composite's microstructure also shows CCTO crystals embedded in the ENR-25 with excellent surface contact. The surface morphology showed that samples with filler content of 60 phr onwards had a lot of CCTO particle pore agglomeration, which reduced its mechanical strength from 16.46 to 6.49 MPa.

Ti2AlNb alloy has great potential for application as a structural material in aircraft manufacturing due to its excellent mechanical properties. In this study, the Portevin-Le Chatelier effects of Ti2AlNb alloy were at first studied by tensile tests, and the enrichments of Mo, Nb, Zr, and Ti atoms around dislocations were observed by transmission electron microscopy. Subsequently, the material was processed by compression and aging treatments and applied to investigate the effects of elemental clusters on the nucleation and growth of the O phase and α2 phase. Experimental results demonstrated that Al and Ti atoms are enriched around grain boundary and promote the α2 phase precipitation. Meanwhile, the clustering and segregation of Al and Ti atoms inhibit the growth of the O phase. The content of α2 and O phase precipitation is closely related to segregated atoms induced by plastic deformation and aging treatment. Under the thermo- mechanical processing conditions, the following Burger’s orientation relationships can be obtained: {001}O//{011}B and O// B, α2// B, and {0001}α2//{011}B. The tensile properties of the material processed by plastic deformation and aging treatment were mainly influenced by α2 phase precipitation around the grain boundary. This study deepens the understanding of phase precipitation and renders assistance to control phase precipitation of Ti2AlNb alloy.

Cellulose-derived films have received increased attention for replacing petrochemical substrates in various high-tech applications. However, many cellulose composite films are usually limited in practical application due to the strong hydrophilic character. Herein, we fabricated multifunctional waterproof cellulose films via a combination of protonation and dip-coating modifications. This novel cellulose film with 30 wt% poly(methyl methacrylate) (PMMA) possessed excellent superhydrophobicity (static contact angle about 158°), optical transmittance (84%), and haze (91%). Besides, the film simultaneously exhibited remarkable dimensional stability, such as low water swelling (21.79%), water uptake (25.12%), and improved wet tensile strength (~ 50 MPa). After the corrosion test of acidic and basic solutions, moisture resistance at 90% relative humidity for 120 h, and 120 cycles of bending tests, the composite films still showed superior superhydrophobicity, suggesting excellent durability for the composite films. Such multifunctional cellulose films may have potential applications for solar cell panels, antifogging goggles, food packaging, and other waterproof electronic devices.

Wasted tyres are commonly used in civil engineering applications for a variety of purposes, including as concrete ingredients. Wasted tires that are mechanically sheared into shreds ranging in size from 25 to 300 mm and intended for use in concrete are called " Waste Shreded Tyre Aggregate" to make a contribution to sustainable waste management. Currently, at this point, the basic philosophy of this study is to investigate the effects of Waste Tire Aggregate (WTA) on the mechanical and durability properties of Self Compacting Concrete (SCC) to provide a contribution to reusing waste tires in the construction industry. WTAs with 5, 10, and 15% volume ratios are substituted for fine aggregate in SCC production. In addition, 15% mixtures with a binder quantity of 550 kg/m3, including 20 and 30% fly ash (FA) were substituted and prepared to be compared with the control concrete. To measure the rheological properties of SCCs, slump flow, V-funnel and L-box tests were performed. Then, the produced concrete samples of different sizes were cured under laboratory conditions for 28 days and then subjected to hardened concrete tests on the 28th, 56th and 90th days. The hardened concrete tests were composed of axial compressive strength, flexural strength, splitting tensile, diagonal tensile, abrasion resistance, modulus of elasticity. Finally, a durability test was performed as chlorine penetration depth. The test results show that WTA positively affects the properties of fresh and hardened SCC. Only, the increase in the substitution rate of WTA in concrete mixtures decreased the hardened state strength of the SCC. However, the addition of WTA to up to 15% of the total fine aggregate volume indicates that it is possible to apply recycled WTA to SCC and successfully satisfy both fresh and hardened SCC specifications.

In order to study the effect of gas atmosphere on forming performance of laser powder bed fusion (LPBF), AlSi10Mg alloy was prepared by direct forming and in situ laser remelting under the shielding gas of argon and nitrogen in this study, and its microstructure and properties were characterized and tested, respectively. The results show that the forming performance of AlSi10Mg under nitrogen atmosphere is better than that of argon. Moreover, in situ laser remelting method can effectively enhance the relative density and mechanical properties of AlSi10Mg, in which the densification is increased to 99.5%. In terms of mechanical properties, after in situ remelting, ultimate tensile strength under argon protection increased from 444.85 ± 8.73 to 489.45 ± 3.20 MPa, and that under nitrogen protection increased from 459.21 ± 13.77 to 500.14 ± 5.15 MPa. In addition, the elongation is nearly doubled and the micro-Vickers hardness is increased by 20%. The research results provide a new regulation control method for the customization of AlSi10Mg properties fabricated by LPBF.

Friction stir welding is one of the solid-state welding to join the dissimilar alloys with elevated mechanical strength. In this experimental approach, the impact of process parameters on the mechanical characteristics of different metals or alloys formed by friction stir welding between AA5383 and AA7075 is determined, to optimize these parameters and to determine which ones are important using the Taguchi optimization procedure. The friction stir welding joints are generated experimentally at various factors of joining parameters, and that are rotational speed, feed and tilt angle of tool. The Taguchi approach has confirmed that the rotational speed is the most significant parameter than feed and tilt angle. The ANOVA shows that the selected parameters show individual and combined influence over mechanical properties. The prediction equation is proposed for predicting mechanical characteristics by using general linear model, and contour graph examination is employed for checking the effect of input parameters. The optimized joining parameters are determined for maximizing tensile and impact strength and minimizing the hardness of the welded specimens. The general linear analysis-based ANOVA approach has confirmed that the selected process parameters show combined and individual influence on impact strength. The optimized process parameters for maximizing tensile strength and hardness of the welded specimens are 1200 rpm of rotational speed, feed of 20 mm/min and tilt angle of 1.5°. The 1200 rpm of rotational speed, 60 mm/min of feed and 1.5° of tilt angle are the optimized process parameters for maximizing impact strength.

In order to study the mechanical mechanism of the new tension–compression composite anchor, the finite element software is used to establish the numerical calculation model of the new composite anchor, and the numerical drawing test is carried out. Through numerical experiments, the optimal position range of the bolt bearing plate is obtained, and the axial load and shear stress distribution of the bolt were analyzed. The results show that the ultimate pullout force of the new tension–compression composite bolt increases first and then decreases with the movement of the bearing plate position, and the optimal position is at the position where the length ratio of the tension–compression anchorage section is 3:4. At the same time, the study shows that the optimal position of the bearing plate has an optimal position interval. The ultimate uplift capacity of the new tension–compression composite anchor is 118.6% and 94% higher than that of the traditional tension anchor and pressure anchor, respectively. The shear stress distribution of the new tension–compression composite anchor is more uniform. The peak shear stress first appears at the bearing plate and begins to transfer to both sides of the bearing plate with the increase in the drawing force, which increases first and then decreases. Since the new tension–compression composite anchorage section is in an unbonded state, the axial load of the bolt is always equal to the drawing force. The axial force distribution of the tensile anchorage section is similar to that of the traditional tensile bolt and decreases exponentially along the axial direction of the bolt. Under the action of ultimate drawing force, the plastic zone distribution of the new tension–compression composite anchor is different from that of the traditional tension anchor and the traditional pressure anchor. The plastic zone first appears in the position of the bearing plate and begins to transfer to both sides of the bearing plate with the increase in the drawing force. When the plastic strain exceeds the allowable strain of the interface, the bolt pulls out from the anchor hole and the bolt support structure fails.

This paper provides a mechanistic understanding of hydrogen-microstructure-strain interactions in a finely-grained 25Cr-7Ni super duplex stainless steel subjected to dynamic tensile loading. Miniature-sized tensile specimens were hydrogen-charged for up to nine days, and the microstructure was imaged, in-situ, during mechanical tensile testing. Digital image correlation analysis of the recorded images revealed that the austenite phase underwent softening while the ferrite phase hardened due to uptaken hydrogen. Severe strain localization occurred due to dissolved hydrogen in the microstructure resulting in hydrogen-induced cracks. Mobile hydrogen atoms caused softening of the microstructure while trapped hydrogen reasoned hardening. The austenite's hydrogen absorption capacity is decisive for the susceptibility to hydrogen embrittlement.

Exploration of the effect of crosslinking point structures on elastomer properties is significant in the formulation design and performance optimization of elastomers. In the work, we used an equal molar random copolyether of hydroxyl terminated 3,3-bis(azidomethyl)oxetane and tetrahydrofuran (PBT) as a prepolymer, and two PBT elastomers with different crosslinking point structures were prepared by reacting PBT with polyfunctional isocyanate compound N100 and TMP/HDI. FTIR spectrum analysis and swelling tests indicated that N100 crosslinked elastomer S0 and TMP/HDI crosslinked elastomer S4 had an identical chemical crosslinking network. For elastomer S0, hydrogen-bonded urea carbonyl and hydrogen-bonded carbamate carbonyl existed simultaneously, whereas only hydrogen-bonded carbamate carbonyl existed for elastomer S4. Low-field nuclear magnetic resonance measurements analysis indicated that hydrogen-bonding association was among elastomer crosslinking points. Dynamic mechanical analysis showed that the stronger urea carbonyl hydrogen bonding among crosslinks provided elastomer S0 with a lower glass transition temperature (− 37 °C) and a lower modulus loss factor. Elastomer S4 with weaker carbamate carbonyl hydrogen bonding among crosslinking points yielded a higher glass transition temperature (− 30 °C) and higher modulus loss factors. Elastomer S0 presented a higher tensile modulus, and elastomer S4 presented a higher tensile strength and elongation-at-break. These findings provided an experimental and theoretical basis for adjusting mechanical properties of end-crosslinked elastomer by constructing different crosslinking point structure.

Rock strength parameters are substantially impacted by porosity. This paper proposes a new model for presenting the relationship between porosity and the ratio of the unconfined compressive strength to the tensile strength of rock. The correlation between porosity and the constant mi of the Hoek–Brown (H–B) criterion is studied. To consider the effect of porosity on the rock strength ratio, the H–B criterion is modified by incorporating porosity instead of the H–B constants mi and s. A series of uniaxial, triaxial and Brazilian tests are conducted on various types of rocks (sedimentary, metamorphic and magmatic rocks) to study the effect of porosity on rock strength characteristics. The modified H–B criterion provides a good representation of the effect of porosity on the failure envelopes of rock. The modified criterion can be used to estimate the porosity and strength parameters of rock.

To take advantage of the excellent mechanical properties of ultra-high-strength steels, welding processes must be properly controlled to maintain the mechanical properties in welded structures. Electron beam welding (EBW) provides high energy density and thus a relatively low heat input compared to arc welding. However, the narrow fusion zone (FZ) and the heat-affected zone (HAZ) can have insufficient toughness values due to the rapid cooling of the joint. In the present study, S1100MC welded by EBW without filler material was investigated with respect of microstructure, toughness properties, strength of the joint, hardness, and residual stresses close to the top surface. The microstructure of the FZ generally consisted of martensite and tempered martensite with inhomogeneous prior austenite grain (PAG) size between root and face FZ. The martensite phase with smaller PAG sizes caused a strong increase in hardness value in fine-grained HAZ. Tensile tests fractured only in the base material since welds show higher strength than the base material. Evaluated impact toughness levels are moderate, and fracture path deviations only occurred for a particular notch type. The residual stresses in the transverse and longitudinal direction reached up to 79% of the yield strength.

In this study, extensive large-scale model pavement experiments consisting of a total of twenty-one pavement sections overlying different subgrade conditions (poor to firm) were conducted to determine the traffic benefit ratio (TBR). TBR is quantified as the ratio of a cumulative number of load cycles to reach a defined deformation/failure state in the reinforced section to that of the unreinforced section with the same pavement geometry and material constitutions. Biaxial geogrids made up of polyester and polypropylene of varying tensile strengths were considered. The controlled experimentation was carried out in a large-sized test chamber of dimensions equal to 1.5 m in length, 1.5 m in width, and 1.0 m in depth. To simulate the wheel loading on the pavement in a real field condition, repetitive loading was applied in the form of haversine loading using a linear actuator system of 100 kN capacity. Based on the studies, geogrid placed at one-third thickness of the base layer was found to be the optimal depth of reinforcement. TBRs of the reinforced pavement were found to range from 1 to 52. The study, however, recommends the use of TBR ranging from 1.5 to 4 for a conservative design. Finally, the TBR-based design of pavements was illustrated through a worked-out example for given input parameters. The thickness of aggregate layers was found to reduce by 7.5–29% for the range of California bearing ratios and TBRs considered in this study.

Recently, natural filler reinforced polymer composites are important materials for various engineering applications. Hence, this present work focuses on utilization of Cocos nucifera shell powder (CNSP) as a filler in vinyl ester (VE) resin to produce particulate composite specimens. The particulate composite plates with various weights or filler contents from 5 to 30 wt% were fabricated, using compression molding technique. The fabricated composites were subjected to tensile, flexural, impact, hardness, heat deflection and swelling behavior tests to obtain their corresponding material properties. Energy dispersive X-ray analysis was carried out on the C. nucifera shell powder/vinyl ester (CNSP/VE) composite specimens to investigate into the presence of their elements, in addition to the aforementioned tests. From the experimental results obtained, it was observed that the optimum mechanical properties of CNSP/VE composites were obtained at 15 wt% of filler content, having tensile, flexural and impact strengths of 38.70, 105.13 MPa and 33.04 kJ/m2, respectively. Also, the heat deflection temperature results varied from 158 (0 wt%, neat VE resin) to 171 °C along various percentages of filler contents. Lastly, the morphological study/analysis of the fractured CNSP/VE composite specimens was conducted by using a scanning electron microscope (SEM) to confirm the experimental data/results obtained. It was evident that CNSP/VE composite structures could be potential substitutes for some synthetic composites. Also, they are suitable for various engineering applications in aerospace, electrical/electronics and automobile industries, based on their properties.

Two ingots weighing 400 g and 5 kg with nominal compositions of Fe–8Mn–4Al–2Si–0.5C–0.07V–0.05Sn were produced to investigate the effect of processing variables on microstructure development. The larger casting has a cooling rate more representative of commercial production and provides an understanding of the potential challenges arising from casting-related segregation during efforts to scale up medium Mn steels, while the smaller casting has a high cooling rate and different segregation pattern. Sections from both ingots were homogenized at 1250 $$^{\circ} $$ ∘ C for various times to study the degree of chemical homogeneity and $$\delta $$ δ -ferrite dissolution. Within 2 hours, the Mn segregation range (max–min) decreased from 8.0 to 1.7 wt pct in the 400 g ingot and from 6.2 to 1.5 wt pct in the 5 kg ingot. Some $$\delta $$ δ -ferrite also remained untransformed after 2 hours in both ingots but with the 5 kg ingot showing nearly three times more than the 400 g ingot. Micress modeling was carried out, and good agreement was seen between predicted and measured segregation levels and distribution. After thermomechanical processing, it was found that the coarse untransformed $$\delta $$ δ -ferrite in the 5 kg ingot turned into coarse $$\delta $$ δ -ferrite stringers in the finished product, resulting in a slight decrease in yield strength. Nevertheless, rolled strips from both ingots showed $$>900$$ > 900 MPa yield strength, $$>1100$$ > 1100 MPa tensile strength, and $$>40$$ > 40 pct elongation with $$ < 10 pct difference in strength and no change in ductility when compared to a fully homogenized sample.

The changes of mechanical properties and carbides coarsening behavior of marine atmospheric corrosion resistant steel at different tempering processes were studied. The results of tensile and impact tests showed that the best mechanical properties obtained when the steel was quenched at 940 °C and tempered at 520 °C. The impact toughness at −20 °C increased firstly and then decreased with the tempering temperature increasing. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations showed that with the increase in tempering temperature, cementite particles gradually grow up and the size of cementite particles at grain boundaries was larger than that of cementite particles in grains. The coarsening of cementite may be related to the lack of Cr element during high temperature tempering, resulting in the decrease in impact toughness.

Inspired by mussels, a new cellulose-based (CTP) adhesive was fabricated by simply blending via cellulose nanofibrils (CNFs), tannic acid (TA), and polyethyleneimine (PEI), where the preparation method was green, facile, and simple. The structure and properties were examined by FT-IR, TGA, XRD, SEM, lap shear tensile, and water absorption tests. The results showed that chemical bonds, hydrogen bonds, and chain entanglement were formed among CNFs, TA, and PEI. Compared with the CNF adhesive, the dry shear strength of the CTP adhesive increased 103% to 392.2 ± 32.2 kPa. And the wet shear strength of CTP adhesive increased from 0 kPa to 144.7 ± 20.1 kPa, indicating that the CTP adhesive can be used in humid or even water environments. Meanwhile, the water absorption of CTP adhesive decreased from 37.9 ± 14.1% to 12.8 ± 5.9%. It was the introduction of catechol groups and physical–chemical interactions of three components that endow the CTP adhesive with improved dry and wet adhesion strength and water resistance. Moreover, the proposed CTP adhesive could be used on the surface of various materials, including rubber, plastic, paper, wood, metal, and glass. Overall, this work shows that the CTP adhesive has a wide range of application prospects.

2XXX series aluminium alloys are widely used in propellant tanks of space launch vehicles. In this work, friction stir welding (FSW) was performed to produce dissimilar joints between 2195 and 2219 alloys. The effect of temperature (ambient, 77K and 20K) on the tensile properties of 2195–2219 joints was investigated. Results showed that a decrease in temperature increased the tensile properties significantly without a reduction in ductility. Due to contribution from 2195 alloy, the properties of the dissimilar joint were marginally higher than the 2219 similar joint. The failure location in the thermo-mechanically affected zone (TMAZ) of the 2219 side was substantiated with the hardness survey across the weld. The effect of material position at advancing side (AS) and retreating side (RS) on tensile properties of dissimilar joints was investigated. Results depicted that regardless of the material position, the failure was consistently observed at TMAZ of 2219. However, placing 2219 at the AS showed better properties than at RS. This study brought out the tensile behaviour at cryogenic temperatures and suitable material position to achieve optimum strength, which are key inputs for designing launch vehicle structures.

Strength of diffusion bonded AA1100/AA7075 alloys subjected to the lap shear and ram tensile load were performed and Artificial Neural Network (ANN) models was established to inaugurate connection amid input variables. Progress in strength was observed for improved interfacial thickness; however, beyond 6 μm thickness and 375 °C, a decline in strength was noticed. Similar trend was noticed for hardness value at 375 °C, whereas interface hardness is same as that of its hardest base alloy to provide optimum bond strength. In addition, failure nature of developed AA1100/AA7075 alloys is examined using electron microscope and intermetallic at the interface is found using X-ray diffraction pattern. Finally, the optimum values for diffusion bonded joints with their responses are affirmed by experimental results.

Grain refinement of Al–Si alloys is one of the effective methods for improving the elongation (El) and ultimate tensile strength (UTS). The influences of alone adding Ni (0.5, 1.0, 1.5, and 2.0%) and complex adding Ni (0.5, 1.0, 1.5, and 2.0%) plus 0.4%Y on the evolution of α-Al, eutectic Si, as well as mechanical performance of Al–7Si alloy, were investigated. All specimens were characterized by electron probe microanalysis, transmission electron microscopy, optical microscope, and scanning electron microscope. The results indicated that the secondary dendrite arm spacing (SDAS) of primary α-Al was markedly decreased with increasing Ni content in Al–7Si alloy. When the Ni addition concentration increased to 1.5%, the developed dendritic α-Al were effectively refined into fine equiaxed dendrites. Rare earth Y (0.4%) plus Ni were together added to Al–7Si alloys. The results showed that complex addition of Ni plus Y had a more outstanding refinement effect of α-Al and eutectic Si than that of Ni alone addition in Al–7Si alloy. The coarse and needlelike eutectic Si was modified into fine fibrous shape, and the SDAS of α-Al was significantly reduced when 1.5%Ni plus 0.4%Y was simultaneously added to Al–7Si alloy. Meanwhile, the mechanical performance test illustrated that the El and UTS were improved to 10.8% and 217.8 MPa, respectively.

Chalk breaks easily when subjected to human action such as mechanical handling, earthworks operations or pile installation. These actions break the cemented structure of chalk, which turns into a degraded material known as putty, with lower strength and stiffness than the intact chalk. The addition of Portland cement can improve the behaviour of chalk putties. Yet, there are no studies determining the tensile strength of chalk putty–cement blends, the initial stiffness evolution during the curing time and other design parameters such as friction angle and cohesion of this material. This paper addresses this knowledge gap and provides an interpretation of new experimental results based on the dimensionless index expressed as the ratio between porosity and volumetric content of cement (η/Civ) or its exponential modification (η/Civa). This index aids the selection of the amount of cement and density for key design parameters of compacted chalk putty–cement blends required in geotechnical engineering projects such as road foundations and pavements, embankments, and also bored concrete pile foundations.

In this study, the effect of the stress state of a welded joint during application of high-frequency mechanical impact (HFMI) treatment on the resulting fatigue strength was investigated through fatigue tests and finite element analysis. A high-frequency impact treatment tool was used as the HFMI device. Longitudinal attachment welded joints were treated under a state in which a static load was applied and subsequently tested under a constant stress amplitude with stress ratios of 0 or 0.5. In addition, residual stress measurements and finite element analysis simulating welding and treatment processes were performed. The results indicate that the HFMI treatment is beneficial even when applied under a static tensile load, as the resulting compressive residual stresses are similar regardless of the stress state in the joint during treatment, meaning that the HFMI is applicable to existing structures.

The blend (wax M) of crude by-product polyolefin wax (wax K) and a fractionated commercial paraffin wax (wax J) was suggested to replace the wax J as a coating agent for wax-coated papers. The rheological properties of waxes J, K, and M were examined and compared. The correlation between viscosity and shear rate applied on these waxes maintained at 90 oC and 130 oC was identified. In particular, this paper, for the first time, presented non-Newtonian shear thinning behavior of not only wax K but also its blend of wax M in terms of their viscosity affected by shear rate at an operating temperature below their melting temperature of higher-melting-temperature DSC endothermic peaks (HMTEPs). They showed non-Newtonian behavior, so-called shear thinning behavior, at 90 oC in the light of characteristics of both suspension systems and polymer systems. In addition, the profiles of viscosity at 130 oC of all the waxes versus the shear rate exhibited Newtonian fluid behavior. Wax J also showed the behavior of a dilatant fluid. Then, the physical properties including water vapor transmission rates (WVTR), surface roughness, and coated weights, of thin papers coated with waxes J (WJP), K (WKP), and M (WMP) were evaluated, characterized, and compared. As a result, WMP had an equivalent value to that of WJP or the lowest value among wax-coated papers in terms of WVTR. The surface roughness and the barrier property of WVTR were minimized and enhanced, respectively, by blending waxes J and K. The additional physical properties, including dynamic contact angles, surface tension, wet and dry tensile strength, optical examination of the wax-coated fiber structure, and antimicrobial properties of the wax-coated papers, were evaluated. The excellent antimicrobial properties of clinoptilolite added to wax J or wax M appeared.

This study concerns the behaviors of stresses distributed on a sandwich metal panel using high-strength steel (HSS) as faces and magnesium alloy (AZ31B) as core materials via simulation analysis. The combination of the sandwich metal panel offered good potential to reduce the vehicle weight, reduce the excessive fractures, and improve the energy absorption better than monotonic material. In this comparison analysis, there were two main types of materials used which is sandwich metal panel material and solid material. The tensile experiment was set in the tensile specimen by follow ASTM E8 standard test methods, while for simulation, the three-dimensional and meshing process between tensile and compact tension (CT) models was developed in the simulation analysis software. The mesh element size and tolerance values were 1.0 mm and 0.05 mm, respectively. It was subjected to evaluate the ultimate tensile strength and yield strength of the solid material, HSS and AZ31B between experiment and simulation. The stress behavior on both CT specimens only evaluates the energy absorption using simulation with the 90% of yield strength HSS value from tensile simulation. This tensile test was convinced by comparing the result of experimental and simulation with the coefficient value of determination (R2) of more than 0.85. Consequently, the results obtained by simulation analysis show that sandwich metal panel is most practicable with the increment about more than 70% for future improvements in new material development, especially in light armored vehicle applications.

While the findings show the benefits of Be to reduce the deleterious effects of Fe-phases, this work does not promote its use. As noted, care must be taken due to the toxic nature of Be to ensure proper ventilation and environmental controls as well as personnel protection are in place. The present work was carried out on a series of heat-treatable aluminum-based aeronautical alloys containing various amounts of magnesium (Mg), iron (Fe), strontium (Sr) and beryllium (Be). The results show that Be (~300–400 ppm) causes partial modification of the eutectic silicon (Si) particles similar to that reported for Mg addition. Addition of 0.8 wt% Mg reduced the eutectic temperature by ~ 10 °C. During solidification of alloys containing high levels of Fe and Mg, without Sr, a peak corresponding to the formation of a Be–Fe phase (Al8Fe2BeSi) was detected at 611 °C, which is close to the formation temperature of α-Al. The Al–Be–Fe phase precipitates in a script-like morphology. Beryllium addition is beneficial in the case of high Fe contents as it lowers the harmful effects of Fe-phases in Al–Si alloys. In the case of high Fe contents, it seems that the addition of 500 ppm of Be is not sufficient for all interactions with other alloying elements. During the melting process, the formation of Be–Sr phase (probably SrBe3O4 compound) decreases the free Be content and hence the alloy mechanical properties. The role of Be in preventing the oxidation of Mg and in changing the chemistry and morphology of the Fe-intermetallics is observed through improved mechanical properties of Be-containing alloys. The partial modification effect of both Mg and Be appears to improve the alloy tensile properties.

FeAl-based composites with 0, 0.2, 0.5, 0.8 and 1.1 wt.% CNTs were prepared by high-energy ball milling and hot-pressing sintering. The microstructure, mechanical properties and oxidation resistance of CNTs/FeAl composites were tested and analyzed. The results show that the main phases of CNTs/FeAl bulk composites are FeAl phase with B2 structure, α-Al2O3 and AlFe3C0.5. The microstructure distribution is relatively uniform. With the increase of CNTs content, the hardness and tensile strength of CNTs/FeAl composites first increase and then decrease. When the CNTs content is 0.8 wt.%, the two parameters reach the maximum, 53.2% and 25.8% higher than FeAl, respectively. After adding CNTs, the oxidation resistance of CNTs/FeAl composites is improved, and the oxidation weight gain of CNTs/FeAl composites is one order of magnitude lower than that of FeAl alloy. This is due to the presence of thin and dense oxidation film mainly composed of α-Al2O3 and α-Fe2O3 on the material surface.

In order to use numerical simulation to reveal the formability of magnesium–lithium alloys and other light alloys under high strain rate, it is crucial to construct a constitutive model and a forming limit diagram (FLD) of LA103Z alloy that was formed by laser shock at high strain rate. In this study, three different uniaxial tensile experiments on the ultralight alloy material LA103Z magnesium alloy were conducted, the mechanical behavior of the material with sensitivity to high strain rate was studied, and a Johnson–Cook (JC) constitutive model sensitive to high strain rates and suitable for laser shock forming was proposed. At the same time, the constitutive parameters and failure parameters of the modified JC model of LA103Z magnesium alloy were obtained through three different uniaxial tensile experiments. On the basis of the relationship between tensile loading and stress–strain of LA103Z magnesium alloy, the experiments demonstrated the precision of the modified JC constitutive model. A modified constitutive model was then developed by using the user material subroutine VUMAT, and then it was applied to ABAQUS. Finally, the formability of the material was simulated, and the FLD of LA103Z magnesium alloy material in laser shock forming was predicted. This study provides guidance on the actual production and application of LA103Z magnesium alloys.

In this study, poly(vinyl alcohol) (PVA) was crosslinked via catalyst-free solid-state esterification at 120 °C with 2,5-furandicarboxylic acid (FDCA) at concentrations ranging from 1 to 10%. The structural characterization of the obtained products was carried out by attenuated total reflection Fourier transform infrared spectroscopy. The effects of ester crosslinks on the water absorption properties of the modified products were investigated through swelling degree analysis. The improvement in thermal properties of the obtained products was confirmed by thermal gravimetric analysis/differential thermal analysis, which showed that thermal stability was optimal for low concentrations of FDCA, i.e., 1 and 5%, where degradation maximums occurred at 354 and 371 °C, respectively, compared to 267 °C for unmodified PVA. The mechanical properties of the products were also studied via tensile testing, where the tensile strength of the crosslinked PVA using 5% FDCA (48.2 ± 2.6 MPa), doubled when compared to untreated PVA (25.5 ± 1.2 MPa). Poly(vinyl alcohol) (PVA) was crosslinked via catalyst-free solid-state esterification at 120 °C with 2,5-furandicarboxylic acid (FDCA) at concentrations ranging from 1 to 10%. The thermal stability of PVA was improved significantly, especially at low FDCA concentrations of 1 and 5%, where degradation maximums occurred at 354 and 371 °C, respectively, compared to 267 °C for unmodified PVA. A twofold increase in tensile strength for the biodegradable PVA was achieved by crosslinking with 5% FDCA. A twofold increase in tensile strength for the biodegradable PVA was achieved by crosslinking with 5% FDCA.

A simple method for measuring the Young's modulus of thermoplastic polymers at the nanoscale is proposed. Nanoindentation tests have been carried out on three polymers (ABS, PET and PP) using the Berkovich indenter tip. The elasticity moduli obtained from the reduced moduli thanks to the slope of the initial part of the discharge curve were greater than the real moduli of these polymers. For this, a simple method is proposed to minimize the error made on the determination of the modulus which is based on the calculation of several stiffnesses between 10 and 98% of the maximum load on the experimental unloading curve. The results show that the calculated moduli at a load less than 50% of the maximum load were close to the macroscopic moduli and the effect of viscosity was minimized. In the end, the elastic Young's modulus obtained by our approach is in very good agreement with the result of the tensile tests.

This study aimed to evaluate the synergistic effect of nano-ZnO (ZnO-N) and Mentha piperita essential oil (MEO) on the functional and antibacterial properties of bovine gelatin bionanocomposite film. A mixture of ZnO-N (1%, 3%, and 5%) and MEO (1%, 2%, and 3%) was incorporated into gelatin films. The physicochemical, mechanical, antimicrobial, and barrier properties of the films were explored. Results demonstrated that adding combined ZnO-N and MEO to films lead to decreased moisture content, solubility, water-absorption capacity, water vapor and oxygen permeability, and elongation. However, the thickness, tensile strength, Young’s modulus increased. Incorporating the combination of ZnO-N and MEO into films also reduced the monolayer and free-water content in the equilibrium-adsorption isotherm and shifted the isotherm to lower moisture content. These bionanocomposites showed good antibacterial activity against Escherichia coli O157:H7. In summary, a synergistic effect was observed by incorporating ZnO-N and MEO in active gelatin films.

This study aims to improve the tensile properties of the polyethylene film deposited with a multilayer graphene membrane, in order to establish the understanding of the influence of the methane to hydrogen ratio on the tensile properties of the multilayer graphene membrane. Multilayer graphene membranes were prepared using the chemical vapor deposition method. Four types of multilayer graphene membranes were prepared with different ratios of methane to hydrogen before depositing a membrane on the polyethylene film. Experiments showed that the tensile strength of the polyethylene films with multilayer graphene deposition increased 7 times and the Young’s modulus 5 times more than that of pure polyethylene films, when the ratio of methane to hydrogen was set to 35/100 sccm. A compromise between hydrogen and methane mixture is required to achieve uniform growth of graphene. Insufficient hydrogen cannot activate the surface bound carbon that is necessary for continuous growth. Continuous and well-defined multilayer graphene was synthesized when the ratio of methane to hydrogen reached up a proper value.

A dense Cu-10Sn alloy bulk specimen was obtained by optimizing the laser powder bed fusion (L-PBF) processing, and the relative density of the specimen reached 99.7%. The grain morphology was mainly the columnar dendrite and inter-dendritic phases generated along the solidification direction. Tensile testing and detailed microstructural characterization were carried out on specimens in the as-built and heat-treated condition. Under the quasi-static tensile condition, the yield strength (σ0.2), ultimate tensile strength (UTS), and the elongation of the as-built Cu-10Sn specimen were 392 MPa, 749 MPa and 29%, respectively. After the solution treatment at 800 °C for 4 h, and aging treatment at 400 °C for 2 hours, the microstructure of the specimen transformed from the columnar grain to equiaxed grain, the dislocation density decrease, and numerous annealing twins were observed in the heat-treated state. Therefore, the quasi-static tensile yield strength (σ0.2) of the specimen was reduced to 245 MPa. However, the UTS and the elongation were increased to 840 MPa and 56%, respectively, due to the interaction between annealing twins and equiaxed grain.

The present work discusses very good resistance to hydrogen embrittlement as well as wear resistance of NiP coated API (American Petroleum Institute) X70 steel as compared to the bare steel and electrolytic crystalline Ni coated steel. The NiP coatings with three compositions (hypo, hyper and near-eutectic compositions), prepared by an electroless technique, were predominantly amorphous. The relative wear behavior of the coatings was studied using ball-on disc tests in air. The hydrogen embrittlement susceptibility (HES) was assessed using slow strain rate tensile (SSRT) tests after cathodic hydrogen charging of the coated as well as bare steel. The superior wear resistance of the NiP coated steels showed abrasive wear, whereas the Ni-coated steel showed adhesive wear. Hyper and hypo-eutectic NiP coated steels showed a comparatively lower H-induced embrittlement than the uncoated and Ni-electroplated steels and these could be attributed to the excellent hydrogen barrier property of the NiP coatings.

The effect of grain refiner on microstructural features, casting defects, formation of precipitates and eutectic Si particles, which influence the hardness and tensile properties of Al-Si alloys, is investigated in this study. The A-7Si alloy was prepared through melting and casting route with varying wt.% of Ti up to 0.2%. XRD, SEM and HRTEM analyses characterize the phases and aluminide (TiAl3 and Ti7Al5Si12) precipitates. The thermodynamic analysis, carried out by using FactSage software, confirms the presence of aluminides particle in the microstructure, which is formed at the liquid stage. The microstructure of as-cast Al-7Si alloy contains primary α-Al phase with dendritic morphology and eutectic phase having plate-like eutectic Si particle which is distributed at interdendritic regions. The morphology of primary α-Al grains is altered from dendrite network to fine equiaxed rosette type structure. Secondary dendrite arm spacing (SDAS) is reduced after adding grain refiner (Al-5Ti-1B) to the Al-7Si alloy. The eutectic Si is also refined to fine fibrous type particles. The shrinkage porosity and microcracks are also reduced after the addition of a grain refiner. The yield strength, ultimate tensile strength and elongation to fracture increase from 84, 117 MPa and 16% to 112 MPa, 148 MPa and 22%, respectively, after the addition of 0.1% Ti due to significant reduction in SDAS. Elongation decreases when the percentage of Ti increases more than 0.1%. The fracture mechanism of grain-refined alloy is changed from brittle to ductile fracture.

An assembled rectangular tunnel has the advantages of high space utilization rate and strong urban applicability. This solution has been widely used in urban underground traffic construction. During their construction and operation, the joints are the weakest parts of the structure. The mechanical behavior of joints is closely related to the safety of the tunnel; thus, it is important to use a joint with good mechanical behavior. This study presents a new type of joints for shallow buried assembled rectangular tunnels. To evaluate the effect of design parameters (tenon depth and tenon angle) on the behavior of joints, the finite element method was used. At the same time, the mechanical behavior of rectangular tunnel joint was analyzed and compared with that of a traditional straight joint under the same loading conditions, showing better results. The performance-based engineering (PBE) concept was implemented to evaluate the robustness of rectangular tunnel joints. The results show that if the bolt is placed on the tensile side of the structure, it provides a strong restraining effect on the deformation of the joint. When the tenon depth and angle are 0.8 m and 3.6°, respectively, the overall behavior of the rectangular tunnel joint was improved. The new type of assembled rectangular tunnel joint designed in this study has a good application prospect in a shallow stratum and provides new ideas for the design and construction of such tunnels.

Changing parameters such as: concentration, type and molecular weight of stabilizer, has made possible the control of size and nanoparticles distribution, and thus impacting the final application properties. Ammonium peroxydisulfate is currently used as a conventional oxidizing agent in aniline polymerization is always; however, it results an insoluble, infusible polymer, which is not easily to handle. Hence, rise the approach of using steric stabilizers to overcome of processability and manipulation problems, by a formation of a colloidal dispersion. In this work, the fabrication of polyester/PANI conductive composites was synthesized using in situ polymerization in the organic solution of Para-toluene sulfonic acid-Sodium dodecyl sulfate (TSA-SDS) with ammonium peroxydisulfate as oxidant, in the presence of different type of stabilizer (solid and liquid). These polyester/PANI composites are developed to achieve protection against electromagnetic rays. Polyanilines were characterized using attenuated total reflectance-Fourier transform infrared (ATR-FTIR), RAMAN spectroscopy, and a standard electrical resistance four-probe method, and the composites were characterized using mechanical properties (tensile strength test), electrical (Surface resistivity) and electromagnetic (shielding effectiveness) measurements and scanning electron microscopy observations. The addition of stabilizer increased the conductivity of polyaniline and the polyester/PANI composite. In addition, the tensile strength of conductive polyester/PANI fibers increased. EMI shielding studies of the conducting polyaniline-coated polyester fabrics showed a shielding effectiveness value between 26.69 and 39.12 dB and were obtained in the frequency range 9.45 GHz.