Decrease In Shear Strength Research Articles

Study on Interface Mechanical Properties of Graphene/Copper Matrix Composites

Graphene/copper matrix composites have a wide range of application prospects, but the mechanical properties of the interface have been one of the key problems restricting their wide application. In this paper, the mechanical behaviors at the interface of graphene/copper matrix composites, such as pulling up, pulling out, and cohesion, and the effects of temperature and graphene content on them were studied by the molecular dynamics method. The results show that the pull-up force and cohesiveness show two stages in the whole process. The pulling force increases rapidly and then decreases to 0 slowly. The pull-out force shows three stages: it rises rapidly at first, then fluctuates continuously, and finally drops to 0. The mechanical properties of the interface deteriorated with the increase in temperature. When the temperature increased from 0 K to 1100 K, the interface normal strength, shear strength, and cohesion strength of the interface decreased by 26.3%, 32.9%, and 24.8%, respectively. In addition, with the increase in graphene content, the normal strength of the interface increases, the shear strength decreases, and the cohesion strength almost stays the same. When the graphene content increases from 6.71 at% to 11.75 at%, the normal strength increases by 6.8%, while the shear strength decreases by 37.4%. The influence mechanism of temperature and content is explained from the aspects of the influence of atomic thermal motion and the hindering effect of graphene on the dislocation motion of the copper matrix. The relevant results have certain reference values for the engineering application and theoretical research of graphene/copper composites.

Effectiveness of Surface Treatment on Bonding Performance of Starch-Based Aqueous Polymer Isocyanate Wood Adhesive.

The surface of a bonding material plays a key role in the bonding performance of an adhesive. Herein, we evaluated the effect of substrate surface treatment methods (sandpaper polished, chemical oxidation, and coupling agent) on the adhesive properties of starch-based aqueous polymer isocyanate (API) wood adhesive during hygrothermal aging. The birch substrate was processed with three different surface treatments, and the change of surface was analyzed by X-ray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared spectroscopy (FT-IR), and Energy Dispersive Spectroscopy (EDS) methods. The results showed that the surface treatment had a great influence on the change of the shear strength of glued wood under hygrothermal conditions, and the silane coupling agent treatment could effectively reduce the decrease in the compressive shear strength of the adhesive. An XPS analysis indicated that the chemical oxidation modified wood surface polarity, and the coupling agent treatment in the wood surface formed a transition layer. After hygrothermal aging treatment, due to the different surface treatment of adhesive joint surface binding energy, the internal water absorption rate of starch-based API adhesives exhibited different failure modes of the adhesive joint. These findings indicate that the surface treatment effectively improved the durability of the adhesive joints.

Physical Modelling of Rainfall-Induced Sandy and Clay-Like Slope Failures

Small-scale slope modelling was performed to evaluate the failure process of a landslide triggered by artificial rainfall. The model platform 2.3 m long, 1.0 m wide, and 0.5 m deep was used to build small-scale slope models with the same geometric conditions but different soil types/materials, including sand and two sand-kaolin mixtures with the same slope angle. The hydraulic response of the slope models under simulated rainfall conditions was monitored using volumetric water content, pore water pressure, and matric suction sensors installed at different depths and along different profiles. Slope surface deformation and failure development was also monitored. This paper discusses the factors affecting landslide initiation and propagation, and their relationship to the slope material, infiltration process, and overall soil resistance in a slope related to soil strength, effective stress, and matric suction contribution in the unsaturated part of the slope. Rainfall infiltration caused increase of volumetric water content, dissipation of suction in initially partially saturated materials of the small-scale slope models, resulting in a decrease in effective stresses and shear strength, which in turn led to the occurrence of movements and initiation of slope failures. The main observations arising from the results of the conducted tests relate to initiation and development of the observed instabilities of sandy and clay-like slopes. The test results have shown that within the slopes built from clean sand failure occurs due to groundwater level rising at the slope foot and further retrogressive failure towards the top of the slope, while in the slopes built from sand-kaolin mixtures, instabilities occur in the form of cracks in unsaturated conditions and are the result of matric suction dissipation due to rainfall infiltration.

Heat treatment effects on microstructure and properties of CVI SiC/SiC composites with Sylramic™-iBN SiC fibers

Chemical-vapor-infiltrated (CVI) SiC/SiC composites with Sylramic™-iBN SiC fibers and CVI carbon, BN, and a combination of BN/C interface coating were heat treated in 0.1-MPa argon or 6.9-MPa N2 at temperatures to 1800 °C for exposure times up to 100 hr. The effects of thermal treatment on constituent microstructures, in-plane tensile properties, in-plane and through-the-thickness thermal conductivities, and creep behavior of the composites were investigated. Results indicate that heat treatment affected stoichiometry of the CVI SiC matrix and interface coating microstructure, depending on the interface coating composition and heat treatment conditions. Heat treatment of the composites with CVI BN interface in argon caused some degradation of in-plane properties due to the decrease in interface shear strength, but it improved creep resistance significantly. In-plane tensile property loss in the composites can be avoided by modifying the interface composition and heat treatment conditions.

Cause Analysis and Preventive Measures of Guizhou D2809 Train Derailment Accident in Guizhou, China on 4 June 2022.

This paper summarizes the cause of the debris flow impact train accident by investigating the local geological condition, meteorological data and field investigation that happened in Guizhou, China on 4 June 2022. The result showed that the major reason is the continuous heavy rain in the surrounding area, which led to a small landslide at the upper right of the tunnel entrance. Besides, the construction of the Jianrong Expressway in the upper reaches increased the catchment area, which makes the water content of the upper soil increase while the shear strength decreases. Such large-scale catastrophic accidents significantly threaten the local environment and public safety. Therefore, it is urgent to pay special attention to the changes in geological conditions along the line, especially the adverse effects of construction, to improve the early risk warning and post-accident treatment ability.

Experimental analysis of shear strength and strain rate on H2/CH4 pinch-off flames

An experiment was conducted under acoustic excitation conditions for the physical understanding of the pinch-off phenomenon in non-premixed flames. For fuel conditions, H2/CH4 has a volume ratio of 75/25 %, and for acoustic excitation conditions, experiments were performed at a forcing frequency of 80 Hz and velocity perturbation intensity of 50 %. In addition, experiments were performed in the range of 1.0–4.5 m/s of air and fuel velocity. OH* chemiluminescence analysis using a high-speed camera was performed for flame structure analysis, while particle image velocimetry was performed for flow-field analysis. Simultaneous measurement of OH* chemiluminescence and particle image velocimetry allowed observing the flame separation. Strain rate and shear strength were introduced for pinch-off and non-pinch-off analysis, and the correlation between the two factors was analyzed. Pinch-off mapping analysis at various velocities confirms the presence of a physical boundary. The direction of vortex roll-up reverses depending on the fuel and air velocities, indicating the formation of different flame structures. When acoustic excitation dominates, the strain rate increases and flame pinch-off occurs. In contrast, when the shear effect dominates, a non-pinch-off flame is obtained and the shear strength decreases. Accordingly, the strain rate and shear strength are correlated, and the approximate pinch-off threshold can be determined at various experimental points. These findings suggest that the shear strength and the strain rate can be used as parameters to distinguish pinch-off.

Effect of low-density polyethylene, polyvinyl chloride, and high-density polyethylene micro-plastic contamination on the index and engineering properties of clayey soil- an experimental study

Soil health is one of the prominent features of the Sustainable Development Goals (SDGs). The SDGs seek to achieve the target of 75% healthy soils by 2030. On the contrary, the growing accumulation of microplastic contamination in soil environments is an issue of worldwide concern. The effect of a variety of microplastic accumulation on soil index and engineering properties is still unclear. Clayey soil is very important in geotechnical engineering because of its complex behaviour. This study investigates the effects of a variety of microplastics such as Low-Density Polyethylene (LDPE), Polyvinyl Chloride (PVC), and High-Density Polyethylene (HDPE) in environmental relevant concentrations (2%,4%,6% w/w) on index and engineering properties of clayey soil with respect to a number of observation days. In the present study, the non-contaminated soil treated as a control. The detailed experimentation revealed a significant change in the liquid limit, plastic limit, and shear strength values of clayey soil with an increasing percentage of microplastic contamination, whereas minute changes are recorded with respect to the number of observation days, this may be due to inert nature of microplastic. The shear strength is one of the critical engineering properties of soil that determines the strength and stability of the soil. The shear strength value of 0.94 kg/cm2 for control decreased to 0.76 kg/cm2 and 0.73 kg/cm2 and 0.85 kg/cm2 for the addition of 2%, 4%, and 6% respectively of LDPE microplastic contamination, similarly, for PVC microplastic contamination of 2%, 4% the shear strength decreases to 0.77 kg/cm2, 0.85 kg/cm2 respectively, the HDPE microplastic contamination of 2%, 4%, and 6% results in shear strength decrease to 0.52 kg/cm2, 0.53 kg/cm2 and 0.65 kg/cm2.The altered values of shear strength along with other index and engineering properties of soil due to microplastic contamination may lead to instability in structures or may increase the chances of harmful natural threats such as landslides. The present study provides evidence of significant changes in the index and engineering properties and therefore the stability of the soil which is the major contribution of the study.

Microstructure and mechanical properties of electroplated Ni-Sn TLP bonded joints with different bonding and aging times

Much attention has been drawn to the Ni Sn transient liquid phase (TLP) bonded joints for high-temperature electronic packaging applications since their inception. A comparative study of Ni Sn TLP bonded joints with different interlayers was conducted. The evolution of microstructure and mechanical properties of joints with different bonding times was also investigated. In addition, the high-temperature (300 °C) thermal reliability of the Ni Sn TLP bonding joints was explored with aging times from 0 h to 100 h. The results show that the electroplated Ni Sn TLP bonding joint exhibited a slightly higher average shear strength than when using a Sn foil and Sn 96.5 Ag 3.5 paste. Also, the average shear strength of the electroplated Ni Sn TLP bonded joints was greatly improved as the bonding time increased from 0.5 h to 5 h, while there was a continuous decrease in the average shear strength with the aging time from 4 h to 100 h. During the aging, the Ni/Ni 3 Sn 2 interface was the preferential site for the nucleation of the newly formed Ni 3 Sn 2 intermetallic compounds (IMCs). Furthermore, the cross-sectional microstructure of the shear fractured joints after aging from 4 h to 100 h indicates that the shear fractures propagated through both the Ni 3 Sn 4 IMCs and the Ni 3 Sn 2 /Ni 3 Sn 4 interface. • Joints using electroplated Sn were stronger than that using Sn foil or solder paste. • The average shear strength of joints increased with bonding time from 0.5 h to 5 h. • Prolonged aging time (from 4 h to 100 h) deteriorated the shear strength of joints. • Ni/Ni 3 Sn 2 interface was the preferential site for nucleation of Ni 3 Sn 2 during aging. • Aged joints shear fractured through both Ni 3 Sn 4 IMCs and Ni 3 Sn 2 /Ni 3 Sn 4 interface.

The effect of hygrothermal aging on the adhesion performance of nanomaterial reinforced aluminium adhesive joints

Adhesive joints are subjected to various environmental factors such as humidity and temperature, depending on their use in industrial applications. It is important to examine and improve the performance of adhesive joints formed with polymeric adhesives, which are known to be sensitive to humidity and temperature parameters, under these conditions. For this reason, in this study, FPL-etched AA7075-T6 aluminium adherends bonded with nonreinforced and BNNP (boron nitride nanopowder), ANP (alumina nanopowder) and MWCNT (multiwalled carbon nanotubes) reinforced epoxy adhesive as a single lap adhesive joint. Thereafter, performance of the adhesive joints that exposed hygrothermal aging conditions of 1, 2, 4 and 6 weeks at 100% relative humidity (RH) and 60 °C were investigated. Glass transition temperature (Tg) values of nonreinforced and reinforced epoxy adhesives before and after hygrothermal aging were determined by DSC (Differential Scanning Calorimeter) analyses. Depending on the nanomaterial types, the tendency of the adhesive joints to water uptake was determined and compared with nonreinforced adhesive joints. When the shear strength findings were investigated, it was defined that the adhesive joints reached almost saturation after 2 weeks of hygrothermal aging. In addition, the most effective nanomaterial type against hygrothermal aging was determined as MWCNT. After 2 weeks hygrothermal aged, the shear strength decreases of MWCNT reinforced adhesive joints were 21.77% and 16.97% less than BNNP and ANP reinforced adhesive joints, respectively. Although the adhesive deteriorates chemically after hygrothermal aging, its adhesion performance improved with the physical benefits of nanomaterials. However, ANP, which is cheaper in terms of price/shear strength performance in long-term aging times, showed similar results with MWCNT. In addition, fracture mechanisms were examined in more detail with SEM (Scanning Electron Microscope) analyses before and after aging, and the effects of hygrothermal aging on the adhesive joints were determined.

Mechanical properties and microstructure evolution of Cf/SiC–Nb joints using Ti-base laminated foil

Abstract A self-designed Ti–Zr–Cu composite foil was used as an interlayer and vacuum brazed to achieve a heterogeneous joint between the Cf/SiC composite and Nb, resulting in a well-bonded, defect-free joint with a typical interfacial microstructure of Cf/SiC/(Ti, Zr)C/(Ti, Zr)2Cu + Zr2Cu/Ti2Cu + (Ti, Nb)ss/Nb. The effects of different experimental temperatures on the microstructural evolution of the joints and the mechanical properties of the joints were investigated, and the formation mechanism of the joint interface was analyzed. The results show that the microscopic morphology and mechanical properties of the joint interface change significantly with increasing experimental temperature. As the temperature increased to 1080 °C, the shear strength increased by 150.6% compared to 1060 °C (78.09 MPa) and reached a maximum value of 195.72 MPa, but further warming to 1100 °C (144.25 MPa) resulted in a 26.3% decrease in shear strength, with the best joint achieved at 1080 °C.

Experimental Study on the Effects of Matric Suction on Shear Properties of Polypropylene Fiber Reinforced Unsaturated Clay.

Matric suction has an important effect on the behavior of unsaturated soils, and polypropylene fibers are often used to improve soil. In order to probe into the mechanism of matric suction and fiber reinforcement, triaxial shear tests are carried out with changing matric suction and net confining pressure. Unsaturated clay in the Shaoxing section of East Zhejiang Grand Canal is selected with polypropylene fiber as a reinforcement material in the tests. The results show that the total cohesion intercept and effective internal friction angle of soil increase with the increase in matric suction, while the adsorption internal friction angle decreases gradually. Similarly, the contribution of matric suction to shear strength decreases. The total cohesion intercept is more sensitive to matric suction. As the length of fiber is 12 mm, the shear strength parameters of soil will be improved accordingly, which makes the fiber reinforcement achieve the best. The stress-strain relationship is approximately hyperbolic and strain hardening. The characteristics of strain hardening are more obvious with the increase in matric suction, and the soil specimens present plastic failure. The volumetric strain of specimen is more sensitive to the changing net confining pressure. It increases with the increase in net confining pressure, and increases linearly as the matric suction is zero. The failure modes of triaxial tests are divided into tensile failure and friction failure.

Parametric study of the earth dam's behaviour subjected to earthquake

Abstract Static stability of an earth dam can be established by estimating the static safety factor equal to the ratio of the shear strength to the shear stress along a critical sliding area. In contrast, it is more complicated to evaluate the dynamic stability during an earthquake. The water filling the interstices of the earth dams cannot drain during the short duration of an earthquake. An excess pore water pressure ΔU develops, and its role is predominant in the destabilisation of the dam. The pore water increase causes a decrease in the soil shear strength. It is, therefore, crucial to evaluate and take into consideration ΔU in the dam dynamic stability analysis. This research is a contribution to reach this objective. A parametric study was conducted by varying the physical and mechanical soil characteristics constituting the dam, as well as its geometrical values, in order to evaluate their effects on the dynamic safety factor. The dynamic safety factor is calculated using the pseudo-static method, taking into account the excess pore water pressure that develops during cyclic loading into the granular soil of the earth dam upstream face. The results of the parametrical analytical study were also compared to the results of numerical simulations of the dam seismic stability trough pseudo-static method. The numerical simulations were done with three different software: PLAXIS and ABAQUS (based on the finite element method) and GEOSTAB (deals with the problem at the limit equilibrium using the simplified Bishop method). At the end, on one hand, we were able to describe how and at what level of the dam upstream face the sliding occurs, and on the other hand, we were able to underline the adequate combination between the dam geometric parameters and the mechanical soil characteristics which may ensure seismic stability.

Mechanical properties of multi-recycled aggregate concrete under combined compression-shear loading

The mechanical properties and strength failure criteria of multi-recycled aggregate concrete (multi-RAC) under combined compression and shear loading states are investigated in this paper. The peak shear strength, peak shear displacement, and failure patterns are compared under different regeneration cycles and normal compressive stress ratios. The results reveal that both the peak shear strength and peak shear displacement increase with the increased normal stress ratio. The shear failure pattern with higher severity corresponds to more spalling powder and debris deposited on the shear fracture surface. When the regeneration cycles of coarse aggregate increase, the peak shear strength decreases and the descending trend become more evident with the higher vertical compressive stress ratio. Under the normal compressive stress, contact friction strength is the dominant component of peak shear strength among the cohesive strength, contact friction strength, and shear dilation strength. Based on different stress expressions, three compression-shear failure criterion models considering the regeneration cycles of coarse aggregate under planar stress state were established for RAC. The stress invariance failure criterion model and octahedral stress failure criterion model in quadratic parabolic functional form can provide high prediction accuracies.

The Effect of Glass Fiber Storage Time on the Mechanical Response of Polymer Composite.

The growing demand for polymer composites and their widespread use is inevitably accompanied by the need to know their degradation behavior over a sufficiently long period of time. This study focuses on commercial glass fiber rovings, which were stored in the indoor environment for up to 11 years. Fibers with different storage times, from fresh up to the oldest, were used to produce unidirectional fiber-reinforced polyester composites that were characterized to determine their shear and flexural properties dependent on fiber storage time. A significant decrease in shear strength was observed throughout the aging of the fibers, down to a decrease of 33% for the oldest fibers. An important finding, however, was that the significant decrease in shear strength was only partially reflected in the flexural strength, which corresponded to a decrease of 18% for the oldest fibers at consistent flexural modulus.

Effect of hydrogen accumulation on θ' precipitates on the shear strength of Al-Cu alloys

We investigate the effect of accumulation of H atoms on θ' strengthening precipitates in Al-Cu alloy. A relationship is established between the H accumulation and decrease in shear strength of alloy depending on the H content in precipitates of second phase. We use the previously proposed multiscale approach combining molecular dynamics (MD), continuum modeling and discrete dislocation dynamics (DDD). H atoms are located inside precipitate and at interphase boundaries. Energetically preferable places of H accumulation near and inside θ' phase in Al-Cu alloy are revealed. It is shown that the H accumulation on θ' leads to a decrease in precipitate shear resistance and causes the change in the dislocation-precipitate interaction mechanism from the Orowan loop formation to the cutting of the inclusion. The H accumulation on precipitates causes an increase in the threshold stress for the dislocation nucleation on the inclusion. The mechanism of softening of inclusions associated with a change from looping to cutting is transferred to the DDD level. The DDD results demonstrate that H charging of Al-Cu alloy can substantially decrease its shear strength. For high strength alloys with small precipitate size and/or inter-precipitate distance and with the yield stress above about 460 MPa, the reduction of strength can reach 10–25%.

Investigations on the macro-meso cumulative damage mechanism of the discontinuities in soft-hard interbedded rock mass under pre-peak cyclic shear loading

To investigate the macro-meso cumulative damage mechanism of the discontinuities in soft-hard interbedded rock mass, laboratory pre-peak cyclic shear tests and PFC 2D meso numerical calculations under constant normal load (CNL) were carried out, considering the effects of moisture content, normal stress, shear rate, shear amplitude, first-order asperity angle and number of cyclic shear. The curve of the shear stress with shear displacement can be divided into six stages, i.e., initial nonlinear compression-shear deformation, compression-shear deformation of approximate linear elasticity , cyclic shear cumulative damage deformation , compression-shear deformation with slowly rising stress, compression-shear deformation with sharply rising stress and compression-shear deformation of brittle stress drop. The peak (residual) shear strength and cumulative shear (normal) displacement decrease and increase, respectively, with number of cyclic shear increasing under the same moisture content, normal stress, shear rate, shear amplitude or first-order asperity angle; under the same number of cyclic shear, these increase and decrease, respectively, with normal stress or first-order asperity angle increasing, while these decrease and increase, respectively, with moisture content, shear rate or shear amplitude increasing. The curve of the meso cumulative damage crack number (energy) with shear displacement shows the characteristics of a slight increase-steep increase, a slow increase and a steep increase-slow increase-steep increase (crack number) or steep increase-slow increase-steep decrease (energy) in the early, middle and later stages, respectively, while the curve of that with number of cyclic shear shows the characteristics of a steep increase and slow increase in the early and later stages, respectively. The macro experimental observations and meso numerical results are in good agreement, and the typical failure modes of the rock discontinuities were summarized as compaction – crack initiation failure, cyclic dislocation – penetration failure and separation – gnawing failure; meanwhile, the macro-meso cumulative damage cracks are approximately an “inverted U-shaped” and densely distributed near the rock discontinuities.

Experimental investigation on the properties of the interface between RCC layers subjected to early-age frost damage

This research presents the macroscopic and microscopic performance of the early-age frost roller compacted concrete (RCC) interface to investigate the influence of pre-curing time and interval time on the performance of the RCC interface subjected to early-age frost damage. Therefore, several RCC specimens were developed under different pre-curing times (12 h, 24 h, 48 h, 72 h and 7 d) and different interval times (4, 12 and 24 h). The shear failure modes, shear strength, pore structure, interfacial transition zone crack width (Wc) and hydration products of the RCC interface were evaluated. Results reveal that the shear strength of early-age frost RCC interface increases with the increase in pre-curing time and decreases with the increase in interval time. In particular, the decrease in shear strength of the early-age frost RCC interface is the most critical after the final setting. The decrease in shear strength between the initial setting and the final setting follows. Moreover, the decrease in shear strength before the initial setting is minimal. The relationship between the macroscopic and microscopic performances of the RCC interface that suffered early-age frost damage was established: the shear strength increases with the decrease in porosity and Wc. Hydrostatic pressure increases are the leading cause of damage in the early-age frost RCC interface. Moreover, the early-age frost RCC interface exhibits higher porosity and Wc and fewer hydration products than the unfrozen RCC interface. Finally, a shear strength of early-age frost RCC was proposed based on the experimental results.

Failure Analysis and Treatments of Tunnel Entrance Collapse Due to Sustained Rainfall: A Case Study

Rainfall is a crucial issue affecting the entrance slope stability of mountain tunnels, as it decreases the shearing strength of soil and reduces the stability of tunnel entrance. This paper presents a case history of the collapse failure of a tunnel entrance in Yunnan Province under rainfall conditions, in which the failure mechanism and potential factors and treatment measures were discussed by field investigation, theoretical analysis, and in-situ monitoring. The analysis results show that the decrease of soil shear strength was mainly attributed to the decline of matric suction value of soil caused by the increase of soil water content. The decrease of the soil shear strength reduced the sliding resistance of the entrance slope and then triggered the collapse. Based on the results, three treatment measures to prevent a secondary tunnel entrance collapse due to rainfall are adopted, including anti-slide pile, grouting, and slope reinforcement. Combined with the field monitoring data, the effects of treatment measures were investigated. Lessons in this case study facilitate prevention and treatment of tunnel entrance constructions under rainfall conditions.

Durability of epoxy and polyurethane bonded timber-hybrid FRP joints under hygrothermal and weathering conditions

This paper investigates the bond between laminated veneer lumber (LVL) and flax-glass hybrid fibre reinforced polymer (HFRP) with different fabric stacking sequences in the LVL-HFRP joints exposed to (1) room condition at the temperature of 20 °C and relative humidity (RH) of 57% (as reference condition), (2) hygrothermal condition (50 °C and 95% RH), and (3) weathering environment (a dry-wet-ultraviolet radiation cyclic condition). Epoxy (EP) and polyurethane (PUR) adhesives were used to manufacture the HFRP composites and bond them to the LVL as LVL-HFRP joints. The joints were tested under block shear tests to evaluate the bond behaviour. The LVL block shear specimens were also tested as the reference for the shear strength change of the LVL in the joints. Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) tests were conducted to study the influence of the hygrothermal and weathering conditions on the functional groups and the glass transition temperature (Tg) of the LVL-HFRP joints. After the hygrothermal and weathering exposures, the results showed that the Tg of the EP-based and PUR-based HFRP in the LVL-HFRP joints increased due to the post-curing and the arrangement of the disordered urea groups. The average shear strength values of the LVL-HFRP joints bonded with the EP adhesive decreased by 4.6–35.2% and the reduction of the shear strength of the LVL part in the joints accounted for the decreased shear strength at the joint level. The average shear strength values of the LVL-HFRP joints bonded with the PUR adhesive decreased by 27.9–57.0% and the reduction of the shear strength at the joint level was controlled by the glass fibre layer of the PUR-based HFRP, regardless of the fabric stacking sequence in the PUR-based HFRP.

Comparison of the effect of ECAP and SSE on microstructure, texture, and mechanical properties of magnesium

Microstructure, crystallographic texture, and mechanical properties of pure Mg, as a model hcp metal, were compared after processing by the two severe plastic deformation (SPD) techniques of equal channel angular pressing (ECAP) and simple shear extrusion (SSE). Both processes were performed on extruded bars at 250 °C for up to four passes, where the minimum grain sizes of 13.7 and 9.8 µm were achieved in the ECAP and SSE processes, respectively. The fraction of dynamically recrystallized (DRX) grains, high angle grain boundaries (HAGBs), and the evolution of dislocation density with equivalent strain experienced the same trend in both processes with higher values after ECAP. The textural evolutions were completely different during ECAP and SSE despite their similar deformation modes. A conventional shear texture was developed after ECAP, while after SSE basal planes were aligned parallel to the processing direction. In the ECAP-processed material, texture softening and lower dislocation density counterbalanced the strengthening effect of grain refinement, resulting in a decrease in shear yield stress (SYS) and ultimate shear strength (USS), while in SSE the shear strength increased constantly with increasing number of passes. It can be deduced from the experimental results that SSE was more effective in achieving a fine-grained homogenous microstructure with high shear strengths as compared to ECAP. • Compare microstructure, and strengths after simple shear extrusion (SSE) and equal channel angular pressing (ECAP) of Mg. • SSE was found more efficient in grain refinement compared to ECAP. • Higher fractions of DRX and high angle grain boundaries (HAGBs) were achieved in ECAP than in SSE. • Develop different shear texture components after ECAP and SSE despite having similar deformation modes. • In contrast to ECAP, the shear strengths after SSE increases by increasing the number of passes.