Search

Context: The electronic properties and optical properties of Cr-doped monolayer WS2 under uniaxial compressive deformation have been investigated based on density functional theory. In terms of electronic structure properties, both intrinsic and doped system bandgaps decrease with the increase of compression deformation, and the values of the bandgap under the same compression deformation after Cr doping are reduced compared with the corresponding intrinsic states. When the compressive deformation reaches 10%, both the intrinsic and doped system band gaps are close to zero. New electronic states and impurity energy levels appear in the WS2 system when doped with Cr atoms. For the optical properties, the calculation and analysis of the dielectric function under each deformation regime of monolayer WS2 show that the compression deformation affects the dielectric function, and when the compression deformation is 10%, the un-doped and Cr-doped regimes show a decrease in ε1(ω) compared to the compression deformation of 8%. For each deformation system, the peak reflections occur in the ultraviolet region. Near the position where the second peak of the absorption spectrum appears, it can be seen that the ability of each system to absorb light gradually decreases with the increase of the amount of deformation and appears to be red-shifted to varying degrees. Methods: This study follows the initial principles of the density functional theory framework and is based on the CASTEP module of Materials-Studio software GGA and PBE generalizations are used to perform computations such as geometry optimization of the model. We have calculated the energy band structure of monolayer WS2 with intrinsic and compressive deformations of 2% and 4% using PBE and HSE06, respectively. The band gap values calculated using PBE are 1.802 eV, 1.663 eV, and 1.353 eV, respectively, and the band gap values calculated with HSE06 are 2.267 eV, 2.034 eV, 1.751 eV. The results show that the bandgap values calculated by HSE06 are significantly higher than those calculated by PBE, but the bandgap variations calculated by the two methods have the same trend, and the shape characteristics of the energy band structure are also the same. However, it is worth noting that the computation time required for the HSE06 calculation is much longer than that of the PBE, which is far beyond the capability of our computer hardware, and the purpose of this paper is to investigate the change rule of the effect of deformation on the bandgap value, so to save the computational resources, the next calculations are all calculated using the PBE. The Monkhorst–Pack special K-point sampling method is used in the calculations. The cutoff energy for the plane wave expansion is 400 eV, and the K-point grid is assumed to be 5 × 5 × 1. Following geometric optimization, the iterative precision converges to a value of less than 0.03 eV/Å for all atomic forces and at least 1 × 10−5 eV/atom for the total energy of each atom. The vacuum layer's thickness was selected at 20 Å to mitigate the impact of the interlayer contact force. [ABSTRACT FROM AUTHOR]

Context: The electronic properties and optical properties of Cr-doped monolayer WS2 under uniaxial compressive deformation have been investigated based on density functional theory. In terms of electronic structure properties, both intrinsic and doped system bandgaps decrease with the increase of compression deformation, and the values of the bandgap under the same compression deformation after Cr doping are reduced compared with the corresponding intrinsic states. When the compressive deformation reaches 10%, both the intrinsic and doped system band gaps are close to zero. New electronic states and impurity energy levels appear in the WS2 system when doped with Cr atoms. For the optical properties, the calculation and analysis of the dielectric function under each deformation regime of monolayer WS2 show that the compression deformation affects the dielectric function, and when the compression deformation is 10%, the un-doped and Cr-doped regimes show a decrease in ε1(ω) compared to the compression deformation of 8%. For each deformation system, the peak reflections occur in the ultraviolet region. Near the position where the second peak of the absorption spectrum appears, it can be seen that the ability of each system to absorb light gradually decreases with the increase of the amount of deformation and appears to be red-shifted to varying degrees. Methods: This study follows the initial principles of the density functional theory framework and is based on the CASTEP module of Materials-Studio software GGA and PBE generalizations are used to perform computations such as geometry optimization of the model. We have calculated the energy band structure of monolayer WS2 with intrinsic and compressive deformations of 2% and 4% using PBE and HSE06, respectively. The band gap values calculated using PBE are 1.802 eV, 1.663 eV, and 1.353 eV, respectively, and the band gap values calculated with HSE06 are 2.267 eV, 2.034 eV, 1.751 eV. The results show that the bandgap values calculated by HSE06 are significantly higher than those calculated by PBE, but the bandgap variations calculated by the two methods have the same trend, and the shape characteristics of the energy band structure are also the same. However, it is worth noting that the computation time required for the HSE06 calculation is much longer than that of the PBE, which is far beyond the capability of our computer hardware, and the purpose of this paper is to investigate the change rule of the effect of deformation on the bandgap value, so to save the computational resources, the next calculations are all calculated using the PBE. The Monkhorst–Pack special K-point sampling method is used in the calculations. The cutoff energy for the plane wave expansion is 400 eV, and the K-point grid is assumed to be 5 × 5 × 1. Following geometric optimization, the iterative precision converges to a value of less than 0.03 eV/Å for all atomic forces and at least 1 × 10−5 eV/atom for the total energy of each atom. The vacuum layer's thickness was selected at 20 Å to mitigate the impact of the interlayer contact force. [ABSTRACT FROM AUTHOR]

In order to investigate the effect of different water filling times on the compression deformation of filled gangue, a large-scale crushed gangue deformation testing system was utilized, and two sets of gradient loading experiments were designed. Through rigorous experimental analysis, distinct patterns of deformation during loading and constant load stages are elucidated, with a particular focus on the influence of water filling timing. Quantitative assessment reveals that early water filling induces rapid gangue deformation, primarily during loading stages, while later water filling stages exhibit a heightened impact on constant load stages. Moreover, the study identifies a stepped deformation phenomenon attributed to the irregularities in crushed gangue particles, shedding light on the underlying mechanisms governing gangue behavior under varying water filling conditions. Notably, an in-depth analysis of energy consumption patterns underscores the dominant role of strain, especially in later water filling stages, significantly influencing deformation characteristics. The study further explores the implications of water filling timing on mining subsidence effects, offering quantitative insights into the stability of gangue backfilling. Under the action of the cumulative deformation and concentrated filling effect, the equivalent filling height is slightly higher than that of the early water filling state, but this trend weakens with the increase of mining height. The conclusions of this study can provide experimental data for stability analysis of crushed gangue filling the abandoned mines with different water filling timing.

{001}〈101〉 texture evolution in Ti–37 mol%Nb (Nb–46.5 mass%Ti) alloy was determined under plane strain compression at the temperatures of 800°C, 950°C, and 1100°C, in which preferential dynamic grain growth (PDGG) took place. At lower temperature and higher strain rate such as 800°C–10−2/s, almost no grain growth occurred in the transverse direction (TD), and the α-fiber + near {111}〈110〉 in the γ-fiber texture was developed, which was a stable orientation as deformation texture. At higher temperature and lower strain rate such as 1100°C–10−3/s, the grain growth along the TD remarkably appeared by grain boundary bulging, and an extremely high pole density of the texture near the α-fiber, especially the rotated cube {001}〈101〉, evolved. A planar dislocation structure with pile-ups appeared and individual dislocations were uniformly distributed in the grains. The rotated cube texture fulfills the conditions of the deformation stability and the low Taylor factor in accordance with the PDGG mechanism. The essential aspect of the mechanism is the preferential growth of grains with a stable orientation for deformation and a low Taylor factor in the given deformation mode. [ABSTRACT FROM AUTHOR]

In today's manufacturing industries, hard competition between rival firms makes it compulsory for researchers to design lighter and cheaper machine components due to the megatrends of cost-effectiveness and anti-pollution. At this point, aluminum syntactic foams (ASFs) are new-generation engineering composites and come into the upfront as a problem-solver. Owing to their features like low density, sufficient elongation, and perfect energy absorption ability, these advanced foams have been considerably seductive for many industrial sectors nowadays. In this study, an industrial-oriented automatic die casting technology was used for the first time to manufacture the combination of AA7075/porous expanded clay (PEC). Micro evaluations (optical and FESEM) reveal that there is a homogenous particle distribution in the foam samples, and inspections are compatible with the other ASF studies. Additionally, T6 aging heat treatment was operated on one half of the produced foams to explore the probable impact of aging on the compressive responses. Attained results show that PEC particles can be an alternative to expensive hollow spheres used in the previous works. Besides, a favorable relationship is ascertained between the aging treatment and mechanical properties such as compression strength and plateau strength. [ABSTRACT FROM AUTHOR]

Nickel-based superalloys have become essential materials due to their excellent comprehensive properties as the miniaturization of products in the aerospace and energy fields develops. The complex microstructure and various strengthening mechanisms of nickel-based superalloys make the plastic deformation behavior extremely complicated at the mesoscopic scale. In this paper, compression experiments of nickel-based superalloy samples with different feature sizes (i.e. the sample diameter to grain size ratio, D/d) and different aging times at the mesoscopic scale were carried out. The coupling effect of feature size and δ phase on the compressive deformation behavior was studied. The results show that the δ phase plays a role in precipitation strengthening during compressive deformation at the mesoscopic scale. When D/d is in the range of 9.7–10.9, the flow stress decreases significantly with the increase of grain size, and a “smaller is weaker” size effect appears. When D/d is less than 9.7, the flow stress increases with the grain size, and a “smaller is stronger” size effect appears. Considering grain boundary strengthening, solid solution strengthening, and precipitation strengthening, a size effect model of flow stress was established. The calculated values were in good agreement with the experimental values. The inhomogeneity of the end surface and side surface increases with the decrease of feature size and the decrease of aging time. The presence of the δ phase reduces the inhomogeneous deformation of nickel-based superalloys during compressive deformation at the mesoscopic scale.

The normal operation of superstructure in loess areas will be related closely to the strength and stability of compacted loess. Loess samples derived from two different engineering sites in China were compacted with different compaction energy, and the main factors which will affect the strength and deformation of compacted loess were analyzed. Different soil samples were prepared with varying moisture content of 11 %–19 %. As the moisture content increases, the compression deformation of compacted loess increases. The immersion influence coefficient suitable for compacted loess was calculated in this study. During soaking in water for 4 days, the California Bearing Ratio (CBR) decreases gradually. Especially, in the process of soak, the lower the initial moisture contents of sample, the more obvious the CBR degradation of sample. It is suggested that soil should be compacted with appropriate compaction energy and moisture content. Furthermore, the loess should be compacted under the condition that the moisture content is slightly greater than the optimal moisture content. When the current moisture content is about 1.02 times the optimal value, the compaction performance of loess is better. As disclosed in this research, the compacted loess in optimal compaction state has smaller compression deformation, better stability and weaker sensitivity to saturation.

The effect of electric field/current on creep deformation was examined in fine-grained 8 mol% Y 2 O 3 stabilized cubic ZrO 2 (8Y-CSZ) under direct and alternative current (DC and AC) conditions. Even at similar sample temperature of 1160–1170 °C, although the electric fields/currents accelerate the deformation of 8Y-CSZ, the acceleration effect (athermal effect), which cannot be explained by an increase of the sample temperature due to Joule heating, is much pronounced in AC than in DC. Under the deformation without the electric field/current, the creep behavior can be characterized by diffusional creep processes with a stress exponent of n ≈ 1, whereas under DC and AC, the predominant mechanism changes to grain boundary sliding (GBS) with n ≈ 2. This indicates that the athermal effect under the electric field/current changes the deformation mechanism from diffusional creep to GBS mechanisms by enhancing GBS and its rate controlling process of cation diffusivity, especially in AC. [ABSTRACT FROM AUTHOR]

For engineering materials, it is important to search for strategies to enhance certain combinations of mechanical properties, because many performances, such as strength and toughness, are mutually exclusive. Effective strategies have evolved in the biological tissues of many plants and animals to construct composite materials with unique combinations of mechanical properties. One impressive example is found in the hammer-like appendages of mantis shrimp, which are exceptionally resistant to crushing because they must withstand the reaction forces created when attacking prey. In this paper, quasi-static compression tests, advanced microscopic observation, and spectroscopic analysis were employed to identify a series of characteristic changes, including changes in mineral composition and arrangement of chitin fibers, and the resulting toughening mechanisms are also examined. The combination of experiments and finite element analysis revealed that by combining different fiber arrangements and components in adjacent macroscopic layers, longitudinal stress could be shifted to the lateral direction, hence efficiently enhancing longitudinal compression resistance while avoiding catastrophic failure. Overall, these findings further the understanding of the fiber structure and toughening mechanism of appendages, which may serve as a foundation for the development of tough bioinspired composites.

Processes of plastic deformation in the interfacial zone of metals with different lattice types are examined using the molecular dynamics method. The investigation is performed on alpha iron, copper, and alpha titanium under two loading conditions, namely, uniaxial compression and interfacial shear. Structural rearrangement at the interface is analyzed depending on the interfacing metals and the lattice orientation of the grains relative to the loading direction. The results obtained show that the mechanism of plastic deformation is governed not only by the material and its strength properties, but also by the anisotropy of these properties due to the lattice orientation. [ABSTRACT FROM AUTHOR]

The tensile deformation is the most common forming principle in the sheet forming process, but there is a new tube forming process—tube hydro-forging has been developed based on the principle of compression deformation. In addition to the instability problem, a new surface defect—thickness distortion—was found in the compression deformation. In this paper, the wall thickness distortion is analyzed from the point of view of mechanics and deformation. It is revealed that in the low pressure tube hydroforming process, a bending moment exists and leads to some small wrinkles in the straight wall. In the tube hydro-forging, the small wrinkles would develop to the thickness distortion with the increase of compressive deformation. The wall thickness and compressive strain are two major effect factors. It is verified by experiments and simulation. This study helps to recognize the new surface phenomenon in compressive deformation. [ABSTRACT FROM AUTHOR]

Coal gangue and slime water are difficult to dispose and utilize on a large scale, which could cause environmental pollution and waste of resources. Therefore, the co-treatment of coal gangue and slime water can serve as an environmentally friendly and novel way for the collaborative resource of solid wastes. Based on this, a method for preparation of slime water-based cementitious material (SWCM) was developed, and the enhanced mechanical property of a coal gangue pile modified by SWCM (CGSWCM) was investigated. For the preparation of SWCM, 6 types of additives were selected, and solidification was achieved with a liquid to solid ratio of 3:1. A compressive strength of 0.45 MPa was acquired with raw SWCM, and the value decreased to 0.38 MPa, then increased to 0.44 MPa when the mass of the kaolin increased from 2 to 10 g. X-ray diffraction and scanning electron microscopy results showed that the pore size of the coal gangue pile decreased and the rod-like ettringite transferred to a linear shape when mass of kaolin increased. The analysis of thermogravimetry proved that the increased mass of kaolin improved the thermal stability, thus decreasing the mass loss. Therefore, it was proposed that the mechanical properties of CGSWCM was affected by evolved hydration product, gap between coal gangue particles and ettringite (AFT) morphology.

Broken waste rock as backfill materials is filled into the underground goaf and will encounter particle breakage under the overburden pressure. The damage degree of the crushed waste rock materials directly affects the compression properties of the backfill body and the control effect of strata movement and surface subsidence. Fractal theory can be used to quantify the breakage degree of waste rock particles. In this study, compression tests are carried out on the broken waste rock materials with different particle size distributions to investigate the influence of the particle size distribution on the fractal characteristics of waste rock backfill materials under compression. The results show that the waste rock specimens with discontinuous size grading and containing more coarse particles have higher stress when entering the stable deformation stage, larger strain if at the same stress level and larger breakage ratio after compression. The particle size distribution of the crushed waste rock specimens after compressive loading has superior fractal characteristics and the fractal dimension increases with the content of fine particles and decreases significantly under discontinuous size grading. The fractal dimension has significant negative exponential function regression relationship with the strain and the breakage ratio. The strain and the breakage ratio decline with the growing fractal dimension. If the waste rock specimens have continuous particle size gradation and higher content of fine particles, the fractal dimension, the strain and the breakage ratio of the waste rock backfill materials tend to be optimal and stable, proving a desirable initial particle size distribution of the waste rock backfill materials.

In this study, deformation behavior of a Zn alloy containing 0.2 wt. % magnesium was studied using compression tests. The compressive deformation was applied up to 1.6 true strain at a wide temperature range of −40 to 300 °C under strain rates of 0.003, 0.03 and 0.3 s−1. Microstructural observations indicated that dynamic recrystallization occurred at the all deformation conditions. Electron back scattered diffraction results implied that continuous dynamic recrystallization (CDRX) was operative during compression through progressive lattice rotation mechanism. Moreover, the new grains are rotated not only around the c-axis but also around the prismatic and pyramidal poles. The DRX progression was discussed considering the orientation factors provided for different slip systems. After compression, the initial extrusion texture was replaced by a new one including basal plane normal to the compression axis. Also, as the deformation temperature and the strain rate decreased, the volume fraction of DRX grains increased. The flow stress of the experimental alloy was successfully modeled based on an exponential constitute equation. An activation energy of 80.5 kJ/mol was obtained for deformation, which was justified according to the cooperation of limited grain boundary migration and dynamic dislocation recovery.

Electromagnetic interference (EMI) cause the equipments used in electronics and avionics industries to either deteriorate or malfunction. Therefore, EMI shielding is essential to ensure electronics equipment safety. The present investigation explores the EMI shielding effectiveness of micro-size cenosphere (2 wt.%, 4 wt.%, and 6 wt.%) filled aluminum matrix syntactic foams. The aluminum matrix syntactic foams were fabricated using stir-casting. The prepared samples were studied for their EMI shielding, microstructural characterization, compressive deformation behavior, and hardness. The cenosphere-filled aluminum syntactic foam exhibited better EMI shielding effectiveness, varied from −41.38 dB to −56.68 dB measured in the frequency range 8 to 12 GHz. This is due to microwave absorption and the dielectric nature of porous cenosphere fillers in the syntactic foam. The highest plateau strength 316.48 MPa and compressive yield strength of 289.53 MPa was achieved in 6 wt% cenosphere-filled syntactic foam. The microstructural study showed the presence of cenospheres in spherical form with homogeneous distribution. The observation shows good bonding between the matrix and cenosphere filler element. The micro-hardness measurement varied from 114 HV to 125.6 HV for the cenosphere filled syntactic foam (up to 4 wt %); further increasing the cenosphere wt% reduced the hardness. The XRD analysis showed the presence of reaction compounds AlSiO2, and Al2SiO5 which enhanced the brittleness in the syntactic foams. [ABSTRACT FROM AUTHOR]

The compressive deformation of backfill materials is large due to the large mining depth of coal seams and high mining-induced stress during the deep backfill mining. Therefore, the controlling effect on strata movement significantly differs from that in shallow coal seams. The research aims to explore the influences of the compressive deformation of backfill materials on the strata movement and stress evolution in deep backfill mining. For this purpose, the backfill panel in Xinjulong Coal Mine, Shandong Province, China was taken as an engineering case study; the changes in displacement, structural evolution, and stress distribution of overlying strata in the panel under compression ratios of backfill materials of 70%, 40%, and 20% were investigated. In addition, the influences of different compressive deformations of the backfill materials on the controlling effect on overlying strata were compared and investigated. The results showed that the displacement of overlying strata in the backfill panel decreases with the decreasing compression ratio: the maximum displacement of overlying strata decreases from 24.32 to 13.74 and 6.83 mm as the compression ratio is reduced from 70 to 40%, and 20%, respectively. Relative to the overlying strata at a compression ratio of 70%, the vertical displacements at compression ratios of 40 and 20% separately decrease by 43.5 and 71.9%. The lower the compression ratio of backfill materials, the better the control of overlying strata. The results provide theoretical support for optimizing the performance of backfill materials in deep backfill mines and controlling the ground pressure in the stope. [ABSTRACT FROM AUTHOR]

Mechanical properties and deformation mechanisms of defect-free copper nanoparticles are investigated by combining experiments with atomistic simulations. The compressive strength of the particles increases with decreasing size and tends to saturate near the theoretical strength in the small-size limit. In this limit, the intrinsic size dependence of the strength is governed by the stochastic nature of dislocation nucleation near the particle surface. The particle deformation process evolves from the initial strain softening to strain hardening as the particle accumulates residual damage. The normalized strength-size relation for Cu is compared with those for Au, Ni, and Pt. The lack of universal behavior among the four FCC metals is discussed. Heavily deformed Cu nanoparticles develop polycrystalline structures and change the lattice orientation from [111] to [110]. The experiments and simulations reveal the twinning mechanism of the lattice rotation leading to the new grain formation. [Display omitted] [ABSTRACT FROM AUTHOR]

Carbon nanotube (CNT)-reinforced NiAl intermetallic composites were produced via powder metallurgy, particularly spark plasma sintering. The aim of this study was to evaluate the room temperature compressive behaviour of the sintered NiAl-CNT composites with a focus on the toughening mechanisms of the CNT reinforcement and the resulting microstructures. Remarkably, the NiAl-0.5 wt% CNT composites exhibited a balanced combination of strength and toughness despite a trade-off tendency, due to the presence of both coarse and fine bimodal grains in its microstructure. Mechanical properties of 831 MPa, 429 MPa and 360 HV were recorded for the ultimate compressive strength (UCS), compressive yield strength (CYS) and microhardness of the NiAl-0.5%CNT intermetallic composites, respectively, along with a compressive strain of 12% being higher than the unreinforced NiAl. [ABSTRACT FROM AUTHOR]

Recently, aluminum matrix syntactic foams (AMSFs) have become considerably popular due to their special physical and mechanical properties. Since these advanced engineering materials have a significant potential for different industrial applications, they can also be interpreted as alternatives to particle reinforced metal composites and traditional metal foams. This study, different from common laboratory scaled methods used in technical literature, emphasizes the possibility of AMSF fabrication using fully automated industrial-focused cold chamber die casting technology. In this context, 1–2 mm, 2–4 mm, and bimodal (50%vol) expanded glass (EG) reinforced syntactic foam samples were manufactured via a specially designed casting machine. Macro- and micro-observations (optical and SEM analyses) indicated that all fabricated syntactic samples exhibited perfect matrix/filler harmony using the proposed method. Density values of fabricated foams varied from 1.17 to 1.50 g/cm3 depending on EG size range. For the determination of mechanical properties, quasi-static compression tests were performed. Furthermore, T6 heat treatment was applied to some foam samples to comprehend the probable effects of the heat treatment on the compressive properties and fracture behaviors. The results showed that although there was a positive relationship between heat treatment and compressive properties of the fabricated foams, T6 treatment altered the failure styles of the samples by triggering matrix brittleness. [ABSTRACT FROM AUTHOR]

A novel flexible woven heat sink (FWHS) composed of sintered copper braided belts was proposed here to meet the heat dissipation requirements of the flexible radiator installed in a narrow space. The sintering treatment was employed to ameliorate the tensile and bending properties as well as the thermal conductivity of the FWHS. The thermal resistance network model and the temperature field analysis in cases of natural convection and forced convection were presented to evaluate the thermal performance of the FWHS. The results show that the FWHS sintered at 850 °C with the expanded shape at a compressed height of 55 mm can reduce the temperature of heat source by 17.1% compared to the uncompressed FWHS, which demonstrates its outstanding advantage of maintaining high efficiency of heat dissipation under compressive deformation.

To study the mechanical behavior of gangue filling materials in depth, through the physical compression testing of red-sandstone gangue of different sizes and numerical simulation of grain flow, the bearing characteristics and deformation and failure rules of gangue compacting were comprehensively compared and analyzed from macroscopic and microscopic perspectives. The results show that under the same vertical load, the settlement decreases monotonously with the decrease of grain size, and the filling effect is significantly enhanced. Structure of force chain between particles evolves from the "polygon" structure to the "triangle" structure, and small particle forms a stable structure earlier than large particle. With the gradual increase in axial strain, the main propagation direction of the force chain is the vertical direction. The distribution law of the tangential contact force of large gangue in the later stage of loading is basically the same as that of small gangue in the early stage Comparison of force chain structures of gangue samples with different sizes under the same strain. [Display omitted] • Gangue breakage was studied from a macroscopic and microscopic perspectives. • Stiffness changes in three stages of gangue compression process were defined. • Force chains structure of gangue compression proces was studied. • Small particles forms a stable structure earlier than large particles. [ABSTRACT FROM AUTHOR]

Large unique block Ni–Cr–Al superalloy foam was fabricated using a combination method of powder-alloying, multi-sheet stacking, and hot compression processes. Subsequently, the compressive properties and deformation behaviors of multi-sheet stacked block metallic foam were investigated from room temperature to 1073 K. The analysis of the resulting structural characteristics of the block foam showed that the interfaces between the sheets have complex strut interactions, such as contacted (deformed) and intersected struts. The relative density was measured as 2.93% for sheet foam and 4.90% for block foam. The compressive deformation of sheet and block Ni–Cr–Al foams showed the typical compressive stress–strain curves of plastically deformable metallic foams regardless of foam type. However, different deformation behaviors in the plateau regions were detected based on the type of foam. It is noteworthy that the yield strength of block foam showed a relatively lower value than that of sheet foam, even though the block foam had higher relative density. The existence of unique interfaces in the multi-sheet stacked block foam may have affected strength and plastic deformation. Finally, distinct compressive behaviors related to the structural and microstructural characteristics of block Ni–Cr–Al foam are discussed. [ABSTRACT FROM AUTHOR]

In this work, the structural mechanisms of the cooling rate effect on the deformation behaviors in metallic glasses (MGs) is studied, by performing the synchrotron radiation-based experiments coupled with a series of simulations. It is found that a MG prepared at lower cooling rate has the higher yield strength and is more likely to soften itself, resulting in lower plasticity. This is because some atomic-to-cluster level structural factors, such as coordination numbers, atomic packing efficiencies, cluster concentrations and regularities. In addition, a quantitative analysis reveals that higher cooling rate leads to more free volumes, and significantly affect the evolution of free volumes during the compressive deformation, tuning the formation and the evolution of shear transformation zones, as well as the yield strength and the plasticity. [ABSTRACT FROM AUTHOR]

An open‐cell metallic foam is newly manufactured using the electrostatic powder spraying (EPS) process, and its room temperature compressive and energy absorption properties are investigated. EPS is a process that uses electrostatic forces. The powder is negatively charged by applying direct current high voltage and undergoes electrostatic spraying on a positively charged polyurethane pre‐form. To control relative density (ρ*/ρ), three different spray amounts are applied (2.5, 3.5, and 4.5 kg m−2). Also, the relative density is measured to increase constantly with the spray amount. The room temperature compressive curves of the EPS foams represent the typical compressive stages (linear elastic, plastic collapse, and densification) of metallic foam. The plateau strengths of the EPS foams measure 0.48 MPa (spraying amount: 2.5 kg m−2), 0.76 MPa (spraying amount: 3.5 kg m−2), and 1.23 MPa (spraying amount: 4.5 kg m−2), respectively. Also, EPS 316L foam with the smallest spray amount has a lower energy absorption amount compared with other types of foam. This study also discusses the compressive and energy absorption behaviors of an open‐cell metallic foam manufactured using the EPS process in relation to its structural and microstructural characteristics. [ABSTRACT FROM AUTHOR]

Broken gangue from the collapsing roof of a longwall coal panel can be used as the backfilling material for goaf backfilling. The particle size gradation has important influence on the compressive deformation of the gangue backfilling material and particle breakage. The compressive deformation of the gangue backfilling materials at 4 different particle size grades is simulated by PFC3D in this paper. The law of the compressive deformation of the gangue backfilling material, the particle cluster distribution and the variation of the gangue block shape are analyzed. The microscopic mechanism of the compressive deformation of the gangue backfilling material is investigated based on the force-chain distribution. The results indicate that when the gangue backfilling material has a small particle size, the specimen has low porosity and a few amounts of the broken particles can fill the pores of the material. When the particles have relatively large sizes, the specimen has relatively high porosity and the broken particles are unable to completely fill the pores. The loading conditions of the particles can only be changed by the frame structure formed by the large particles. If the proportion of the particle size grade is reasonable, a frame structure forms due to the large particles and the small particles with various particle sizes can fill the pores of the backfilling material. This enhances the deformability of the gangue and decreases the compressive deformation of the backfilling material. After backfilled into the goaf, the backfilling material bears the overburden pressure, which means the process of roof convergence is the process of compressive deformation of the backfill body. That is to say, the stiffer the backfilling material, the better the control effect. The importance of the reasonable proportion of the particle size grade is explained from the aspect of microscopic breakage of the particles, which provides a scientific basis for backfill mining. Image 1 • Influence of particle size on compressive deformation of gangue was studied. • Large particles formed skeleton structure and small particles filled the pores. • Different particle size after crushing led to different compression performance. • Particle breakage was studied from a macroscopic and microscopic point of view. • Small particles increased the coordination number of large particles. [ABSTRACT FROM AUTHOR]

In this study, the compressive deformation of crushed sandstone was tested using a crushed rock deformation-seepage test system, and the effects of various factors, including crushed rock grade, grade combination, water saturation status, and stress loading method (i.e., continuous loading or cyclic loading and unloading), on the compressive deformation of crushed sandstone was analyzed from four perspectives including stress-strain, bulking coefficient, deformation mechanism and energy dissipation. The results indicate that the stress-strain relations of crushed sandstone are closely associated with all factors considered, and are well represented by exponential functions. The strain observed for a given applied stress increased with increasing crushed rock grade throughout the loading period. Crushed sandstone grades were combined according to a grading index (n), where the proportion of large-grade rocks in the sample increased with increasing n. The bearing capacity of a water-saturated crushed sandstone sample with n = 0.2 was less than that of an equivalent dry sample for a given applied stress. The stress-strain curve of a water-saturated crushed sandstone sample with n = 0.2 under cyclic loading and unloading was similar to that obtained under continuous loading. Observation and discovery, the deformation mechanism of crushed sandstone was mainly divided into four stages, including crushing, rupture, corner detachment and corner wear. And 20% of the work done by testing machine is used for friction between the crushed sandstone with the inner wall of the test chamber, and 80% is used for the closing of the void between the crushed sandstone, friction sliding, crushing damage. [ABSTRACT FROM AUTHOR]

Objective: To examine the influence of compressive and deflective force on the filaments of 7 commercially available powered toothbrushes. Method and Materials: The deformation (collapse under force) of the filaments on individual brush heads was measured at a rate of 4 mm/mm using an Instron load testing machine under applied loads of 0.5 to 3.0 N. The load was directed perpendicular to the long axis of the filaments. The peak deflection force (deflecting of the filaments from their normal position) was measured with the head of the powered brush oriented horizontally to the applied load. Measurements were taken while the brush head was stationary and during oscillation. Data for peak deflective force were analyzed using a general linear model with post hoc Tukey tests. Results: All powered toothbrushes showed filament deformation when increasing loads were applied. Deformation of the filaments was greatest at 0.5 N and 1.0 N for the Teledyne and was recorded at 1.70 mm and 3.67 mm, respectively. At 2.0 N, greater deformation (5.50 mm) occurred with the Blend-a-Dent, and at 3.0 N, the Sonicare powered toothbrush exhibited a deformation of 3.95 mm. Over the whole range of applied forces, the Braun D15 showed the lowest deformation effects. The different deformations of the filaments recorded between the heads of all powered toothbrushes tested were significant (general linear model, P < .001). Also a decrease in peak deflective force was observed between stationary and oscillating toothbrush heads. Conclusions: The compressive and peak deflective forces vary between different brushes, and the ability to resist deformation depends on the arrangement of the filaments on the head of the powered brush. [ABSTRACT FROM AUTHOR]

The mechanical behavior of materials based on the alkali activation of construction and demolition waste during and after their exposure to high temperatures was studied. The studied materials were based entirely on either, waste bricks or waste ceramic tiles, while a potassium hydroxide / sodium silicate solution was used as alkali activator. The compressive deformation of the alkali activated materials was tested during exposure to 850 - 1050 °C (on-fire testing) and the residual compressive strength was measured after exposure to 600 - 1050 °C for 2 h (post-fire testing), simulating the standard ISO 834 time-temperature curve. Microstructural changes and bulk properties were also assessed. The experimental results showed similar behavior of both materials in post-fire tests. Their compressive strength declined in between 600 and 800 °C and rose at 1050 °C, exceeding the initial value. Their density decreased 8 - 9% at 1050 °C, while their mass loss was 7 - 10% at this temperature. In the on-fire tests, the waste ceramic tile-based material presented plastic strain without any obvious macro-fracture at all the temperatures tested, while the waste brick-based material retained its elasticity and behaved as ceramic material up to 1000 °C with obvious macro-fractures. According to the experimental results, both alkali activated materials have the potential to be used as fire-resistant building materials. [Display omitted] • The alkali activated CDWs can be used as fire-resistant building materials. • Elastic behaviour of the brick waste-based alkali activated materials under load, up to 950 °C. • Pseudo-plastic strain of the ceramic tile waste -based alkali activated materials under load, at 850 °C and above. • Recovery of mechanical strength after cooling of the CDW-based alkali activated materials exposed to fire. • Microstructural transformations of the alkali activated materials at elevated temperatures affected the mechanical strength. [ABSTRACT FROM AUTHOR]

Turtle shells comprising of cortical and trabecular bones exhibit intriguing mechanical properties. In this work, compression tests were performed using specimens made from the carapace of Kinixys erosa turtle. A combination of imaging techniques and mechanical testing were employed to examine the responses of hierarchical microstructures of turtle shell under compression. Finite element models produced from microCT-scanned microstructures and analytical foam structure models were then used to elucidate local responses of trabecular bones deformed under compression. The results reveal the contributions from micro-strut bending and stress concentrations to the fractural mechanisms of trabecular bone structures. The porous structures of turtle shells could be an excellent prototype for the bioinspired design of deformation-resistant structures. In this study, a combination of analytical, computational models and experiments is used to study the underlying mechanisms that contribute to the compressive deformation of a Kinixys erosa turtle shell between the nano-, micro- and macro-scales. The proposed work shows that the turtle shell structures can be analyzed as sandwich structures that have the capacity to concentrate deformation and stresses within the trabecular bones, which enables significant energy absorption during compressive deformation. Then, the trends in the deformation characteristics and the strengths of the trabecular bone segments are well predicted by the four-strut model, which captures the effects of variations in strut length, thickness and orientation that are related to microstructural uncertainties of the turtle shells. The above results also suggest that the model may be used to guide the bioinspired design of sandwich porous structures that mimic the properties of the cortical and trabecular bone segments of turtle shells under a range of loading conditions. [ABSTRACT FROM AUTHOR]

Zn–8Al alloy with density 6.3 g/cm3 was foamed by using cenosphere particles as a thickening agent and CaH2 as foaming agent via stir-casting technique. The cenosphere particles also worked as a space holder to create microporosity into the foam structure. The relative density of the hybrid foam has been obtained in the range of 0.18–0.27. The synthesized hybrid foam was studied under microscopic evaluation and compressive deformation behavior. From scanning electron microscopic observation, it was found that cenosphere particles are dispersed into the cell walls of the hybrid foam as the strengthening material. Compressive deformation of the samples sliced from the foam ingot was examined with different conditions to find out the effect of strain rate and temperature. The properties were evaluated in terms of plateau stress, energy absorption capacity, densification strain, maximum stress and energy absorption efficiency. The present work is focused on the parameters which affect energy absorption efficiency of hybrid foam. It was noted that plateau stress and energy absorption capacity increases with relative density and strain rate. The temperature of the furnace during the compression test was varied from 100 to 250 °C and the result obtained shows that plateau stress and energy absorption capacity values reduces with an increase in temperature during the compression test. The energy absorption efficiency of the hybrid foam varies in the range of 56–90% as it depends on the compressive deformation. More constant plateau region results in higher energy absorption efficiency. Densification strain is found to be almost constant for each set of conditions. [ABSTRACT FROM AUTHOR]

Water removal rate during drying depends on the microstructural pathways of water migration from inside the food materials. The water removal rate also depends on the mechanical properties of plant tissue. There is no literature that shows the interrelationship between viscoelastic property and transport phenomena during drying. In this study, the influence of viscoelastic property of plant-based food material on transport phenomena during drying has been experimentally investigated. Granny Smith apple, pears, and beet root has been taken as the sample in this study. A 2 kN Instron universal testing machine and ImageJ software were used in order to measure and analyze the viscoelasticity of the samples. Three different fruits Granny Smith apple, pears, and beet root show different viscoelastic properties along with different energy loss due to hysteresis. A positive relationship was found between energy loss due to viscoelastic nature of materials and drying kinetics. This correlation can be explained by the nature of the cell wall stiffness that facilitates or hinders the water migration in mechanical and thermal energy applications. [ABSTRACT FROM AUTHOR]

This work characterizes Late Cretaceous calc-alkaline volcanic rocks in Gastre, Northern Patagonia, Argentina. These newly found porphyritic rocks bear an 40Ar–39Ar amphibole age of ~ 74–76 Ma, a subduction-type geochemical signature and a deep, garnet-bearing source. Extruded in a stage of low magmatic activity in the Northern Patagonian Andes (~ 41–44° S), they could represent an eastward migration of the Late Cretaceous magmatic arc that was associated with a regional compressive deformational stage in the South American margin. [ABSTRACT FROM AUTHOR]

This article deals with closed-cell aluminum alloy LM13-cenosphere hybrid foams (ACHFs) with cell anisotropy prepared through stir casing technique. The compressive deformation behavior of hybrid foams in both transverse and longitudinal directions was measured at a strain rate of 0.01/s. The hybrid foam loaded in longitudinal direction (LD) shows higher plastic collapse stress than that in transverse direction (TD). The stress drop ratio is also observed to be higher in the LD. The plastic collapse stress and energy absorption capacity of ACHFs follow the power law relationship with relative density in both the directions. The plateau stress is higher in case of LD and densification strains are marginally higher in case of LD than that in TD. [ABSTRACT FROM AUTHOR]

The compressive deformation behavior of a high-pressure die-cast Silafont®-36 aluminum alloy was evaluated in relation to the microstructural changes during deformation. No strain rate sensitivity was observed for the alloy compressed at room temperature. The as-cast microstructure consisted of softer primary α-Al dendrites and harder Al-Si eutectic structure, which was well depicted by the difference in the nanohardness values using high-speed nanoindentation mapping. The load-bearing capacity of eutectic Si particles and thermal mismatch enhanced dislocation density strengthening were identified to be the predominant strengthening mechanisms in the alloy, plus a certain degree of Orowan strengthening mechanism. The work hardening capacity of the cast alloy was mainly attributed to the increase in the dislocation density in the softer α-Al matrix, which was further assisted by the presence of eutectic Si particles. The relative increase in the flow stresses also corresponded well to that in the nanohardness values of the α-Al grains with increasing strain levels. • A compressive yield strength of 197 MPa is attained in the cast aluminum alloy. • Eutectic Si particles and enhanced dislocation density lead to a high strength. • Nanohardness and XRD can be used to reveal deformation structures. • Work hardening is mainly related to the dislocation density in the α-Al matrix. • The increase in flow stress corresponds well to the change in nanohardness. [ABSTRACT FROM AUTHOR]

Microstructures and compressive yield strength of a novel γ′-strengthened Fe-based superalloy with about 55 wt% iron are investigated after aging at 700 °C for various durations. We found that the γ′ particle always displays a spherical shape and its size increases only from 9 ± 1.6 to 51 ± 14.0 nm with increasing the aging time up to 10,000 h. Meanwhile, the distribution of carbides at grain boundaries is always discontinuously, and no topologically close-packed phases are visible in the alloy during aging. Compressive deformation tests disclose that the yield strength of the experimental alloy at 700 °C increases firstly and then decreases with particle size. Microstructural observations uncover that the predominant deformation mechanism changes from shearing of γ′ particles by weekly-coupled dislocations to shearing by strongly-coupled dislocations and then to Orowan looping with enlarging particle size at the beginning of plastic deformation. Based on these results, it is deemed that the evolution of microstructure and deformation mechanism with aging time leads to the changes in the yield strength during thermal aging. • A novel Fe-based superalloy with 55 wt% Fe is developed. • The novel alloy is strengthened mainly by the γ′ phase. • No harmful phases form in the new alloy during aging at 700 °C. • The microstructure in the novel alloy is relatively stable during aging at 700 °C. [ABSTRACT FROM AUTHOR]

The semi-solid deformation behavior of Ti-7Cu titanium alloy in the temperature range of 1,223 K to 1,473 K and strain rate range of 0.005 to 5 s−1 have been investigated by hot compressive testing. The results show that the maximum and stability stresses decrease with decreasing strain rate and increasing temperature. A yielding occurred to the alloy at a higher strain rate under all experimental temperatures. The flow behaviors were described by a constitutive equation based on the Arrhenius equations and the deformation activate energies is also calculated. By comparing with microstructure of the solid deformation, the liquid in semi-solid deformation can overcome the restriction of the movement of solid particle, which reduced the dislocation pile-up during deformation and caused low deformation resistant stress.

AX61 magnesium alloy was reinforced with short Saffil fibres using squeeze cast technology. Samples were cut from the casting in two directions: parallel and perpendicular to the fibre plane. Samples were deformed in compression at various temperatures from room temperature to 300 °C. Various strengthening mechanisms such as load transfer, increased dislocation density, Orowan and Hall–Petch strengthening were analysed. During deformation, the stress relaxation tests were subsequently performed. The relaxation curves were evaluated with respect to Li and Feltham equations with the aim to find stress components in matrix and parameters of the thermally activated process(es).

The 6xxx aluminum alloy is the first choice for automotive lightweight forgings due to its excellent performance, high strength and low weight. The production time of current aluminum alloy forging generally exceeds 10 h. To reduce the production time of traditional aluminum alloy forgings, 6082-T6 aluminum alloy is used in the forming process. The effects of different heating temperatures (200 °C, 300 °C, and 400 °C) and deformation degrees (30%, 50%, and 70%) on the deformability and properties of 6082-T6 billets have been investigated. The results show that when the heating temperature is higher than 300 °C, the compressive deformation resistance obviously decreases with increasing strength. With compression at 200 °C and 70% deformation with short heating time, the strength of the sample is close to the T6 (solution treatment and artificial aging) state. A large number of dislocations and subgrains were introduced due to the compression deformation, and their amounts decreased as the heating temperature increased. The size of the precipitated phase β′′ slightly grows under a heating temperature of 200 °C. However, when the heating temperature is higher than 300 °C, the precipitated phase gradually changes from β′′, which is optimal for the strengthening effect, to β′ and β, which offer weaker strengthening. Therefore, under a lower heating temperature of 200 °C for 5 min, a large number of dislocations are introduced with the β′′ precipitated phase, leading to higher strength with less heat treatment time.

Under compressive testing at 400C and a strain rate range of 0.05-5 s-1, the hot deformation behavior and microstructure evolution of an as-cast (AC), as-extruded (with a bimodal grain structure (named as Ex-1) or a relatively uniform fine grain structure (Ex-2)) WE43 alloy have been investigated and compared. The results indicate that the AC sample exhibits the highest peak stress, while the Ex-2 sample has the lowest value. Within the AC material, fine grains were firstly formed along the pancake-like deformed grains (as a necklace structure). The necklace structure was also formed within the Ex-1 and Ex-2 materials at high strain rates of 0.5 and 5 s-1. However, a lamellar structure that the coarse elongated grains divided by parallel boundaries was formed within the Ex-1 material. A relatively more homogeneous fine grain structure is achieved after a true strain of 1.0 within the Ex-2 material at a low strain rate of 0.05 s-1. In addition, a discontinuous dynamic recrystallization mechanism by grain boundary bulging is found to occur. After a true strain of 1.2, a (0001) fiber texture, a typical rare earth (RE) texture, and a relatively random texture are formed within the AC, Ex-1, and Ex-2 WE43 alloy material, respectively.

In order to examine the effect of microballoons type on microstructure and compressive deformation behaviour of aluminum syntactic foam, alumina reinforced and cenosphere reinforced aluminum syntactic foams have been made through stir-casting technique. Alumina microballoons reinforced aluminum syntactic foam (AMRASF) has been developed using stir casting technique. Volume fraction of alumina microballoons in AMRASF varies in the range of 0.39–0.74. The compressive deformation behavior of these AMRASF is compared with that of cenosphere reinforced aluminum syntactic foam (CPRASF). The AMRASF does not exhibit clear plastic collapse stage as observed in case of CPRSAF. It is further noted that AMRASF shows the existence of work hardening phenomena after yielding but CPRASF does not show any significant work hardening after yielding even at higher relative densities of foam. This is explained on the basis of characteristics of alumina microballoons and cenospheres and interface characteristics between matrix and respective microballoons used. Effect of individual microballoons’ characteristics on the foam properties has also been explained. [ABSTRACT FROM AUTHOR]