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Low-temperature, low-pressure Cu-to-Cu direct bonding technology is a promising solution for next-generation high-density interconnects. Previous studies have shown that many properties of nanomaterials are determined by their structural characteristics. Therefore, the effect of the nanostructure (i.e., twin crystal and twin boundary, TB, sizes) on the bonding mechanism and mechanical response of the direct bonding of (111)-oriented nanotwinned Cu (NT-Cu) is studied using molecular dynamics simulations, where TB size means the TB layer thickness in terms of the number of atoms. The simulation results show that NT-Cu with extremely small twin crystals (e.g., 0.625 nm) have poor diffusivity. The number of dislocations induced by plastic deformation increases with increasing twin crystal size during stretching processes, degrading mechanical strength. The strain hardening of bonded NT-Cu with extremely small twin crystals (e.g., 0.625 nm) is dominated by the strong barrier created by a high density of TBs, whereas that with twin crystal sizes of 2.5–10 nm is dominated by dislocation–TB and dislocation–grain boundary interactions. Bonded NT-Cu with 2–6 atoms per TB layer exhibits softening at initial plastic deformation due to the onset of partial collapse of TBs; however, the strength then significantly increases with a further increase in strain due to strain hardening. [ABSTRACT FROM AUTHOR]

Applying graphene (Gr) coatings to high-entropy alloys (HEA) is anticipated to enhance their tribological characteristics. The current understanding of the mechanism by which the Gr/HEA is enhanced at the atomic level is still limited. Molecular dynamics simulations revealed the mechanical behavior and strengthening mechanism of the Gr/AlCoCrFeNi HEA during nanoindentation and nanoscratch. The results demonstrate a substantial increase in the indentation hardness of the Gr/AlCoCrFeNi HEA by about 2.4 times. When Gr changed from a single layer to three layers, it further improved (3.2 times for a double layer and 3.9 times for three layers). At the same time, the friction coefficient is effectively reduced. Furthermore, the elevated in-plane stiffness of the Gr coating leads to an expansion of the effective loading area, resulting in increased Shockley dislocation and stair-rod dislocation density within the Gr/AlCoCrFeNi HEA, thereby amplifying the strain hardening effect and reducing subsurface damage. Qualitative experiments confirmed the excellent wear resistance of the Gr/HEA, and coating Gr increased the width of scratches, effectively confirming our simulation results. These findings provide valuable insights for the development and design of Gr/HEA composite coatings with enhanced mechanical properties. [ABSTRACT FROM AUTHOR]

We simulate an alloy of HfNbTaTi mixed in six different proportions and also of the equiatomic system under uniaxial tensile loading at 300 K. Molecular dynamics simulation trajectories are analyzed using radial distribution functions, OVITO, bond-orientational order parameters, and coordination numbers. Equiatomic and the two other alloys (Hf 0.31 Nb 0.23 Ta 0.23 Ti 0.23 and Hf 0.23 Nb 0.31 Ta 0.23 Ti 0.23 ) containing comparable fraction of elements deform similarly through the formation of an amorphous state. Two alloys rich in Nb (Hf 0.17 Nb 0.50 Ta 0.16 Ti 0.17 ) and Ta (Hf 0.17 Nb 0.16 Ta 0.50 Ti 0.17 ) deform similarly resulting in the formation of bcc atoms, which transform to fcc at higher loading. Finally, alloys rich in Hf (Hf 0.50 Nb 0.16 Ta 0.17 Ti 0.17 ) and Ti (Hf 0.17 Nb 0.16 Ta 0.17 Ti 0.50 ) deform resulting in high dislocation densities and hcp atoms. These two hcp-rich alloys also undergo strain hardening. In each mixture during loading, local orientational order of all the different elements changes similarly. Atoms prefer to pair with other atoms than to themselves during tensile loading. [ABSTRACT FROM AUTHOR]

Hydra has a tubular bilayered epithelial body column with a dome-shaped head on one end and a foot on the other. Hydra lacks a permanent mouth: its head epithelium is sealed. Upon neuronal activation, a mouth opens at the apex of the head which can exceed the body column diameter in seconds, allowing Hydra to ingest prey larger than itself. While the kinematics of mouth opening are well characterized, the underlying mechanism is unknown. We show that Hydra mouth opening is generated by independent local contractions that require tissue-level coordination. We model the head epithelium as an active viscoelastic nonlinear spring network. The model reproduces the size, timescale and symmetry of mouth opening. It shows that radial contractions, travelling inwards from the outer boundary of the head, pull the mouth open. Nonlinear elasticity makes mouth opening larger and faster, contrary to expectations. The model correctly predicts changes in mouth shape in response to external forces. By generating innervated : nerve-free chimera in experiments and simulations, we show that nearest-neighbour mechanical signalling suffices to coordinate mouth opening. Hydra mouth opening shows that in the absence of long-range chemical or neuronal signals, short-range mechanical coupling is sufficient to produce long-range order in tissue deformations.

ABSTRACT To appropriately simulate the long‐term mechanical behavior of municipal solid waste (MSW), a constitutive model coupling the effects of biodegradation and fibrous reinforcement was developed. In the proposed model, the compressive deformation due to biodegradation was regarded as being caused by an additional equivalent stress. Considering the effect of biodegradation, an evolution equation of the equivalent stress was proposed, and a plastic volumetric strain hardening law was developed. A fibrous reinforcement parameter was introduced, which was associated with the fiber content, stress state, and plastic shear strain of MSW. A plastic shear strain hardening law was developed to model the fibrous reinforcement. Based on the associated flow rule and two plastic strain hardening laws, the proposed model was established. The proposed model well simulated the hardening properties of MSW, as evidenced by the stress‒strain curves and the consistent, nonlinear increase in volumetric strain with axial strain. The differences in the shear strength and volumetric deformation due to the confining stress and fiber content were also well simulated by the model. Furthermore, the model predictions accurately reflected the findings of experiments conducted over a period of 10 years. Finally, parametric investigations were used to calibrate this proposed model, which can well characterize the long‐term MSW mechanical behavior. [ABSTRACT FROM AUTHOR]

Surface integrity—comprising abrasive embedding, work hardening, and residual stress—is crucial for the performance of nickel-based superalloy components milled by abrasive waterjet (AWJ). Effective evaluation of this integrity is therefore essential. First, the effects of pure waterjet and small-size AWJ on the milled surface were analyzed, with abrasive embedding as a key indicator. It was found that small-size AWJ significantly reduced both the number and depth of abrasive particles embedded. Next, single-factor experiments determined the influence of AWJ process parameters on abrasive embedding, leading to the identification of optimal modification schemes (modification scheme 1 and modification scheme 2) for minimizing the number and depth of abrasives. Recommended processing parameters are waterjet pressure = 100 MPa, and step-over distance = 0.38 mm. Finally, it was observed that both modification schemes decreased surface hardness while significantly increasing residual compressive stress compared to the unmodified surface. These findings offer a theoretical and practical foundation for achieving high surface integrity in the milling of nickel-based superalloys using AWJ. [ABSTRACT FROM AUTHOR]

Engineered Cementitious Composites also known as Strain‐hardening cementitious composites (SHCCs) has unique cracking patterns like cracks that have tiny widths and showcase high density. All of this makes it difficult and laborious to compute crack parameters from crack patterns. Unfortunately, this is an essential part of assessing durability and micromechanical modeling. SHSnet is developed to perform end‐to‐end semantic segmentation of SHCC cracks. SHSnet is efficient, attention based deep encoder‐decoder network with large receptive field. Loss function based on Tversky function were used for training the model. SHSnet with loss function shows promising result with mPrecision, mF1Score and mIoU of 0.87, 0.84 and 0.83 respectively for complex SHCC cracks while requiring at least an order of fewer computational parameters than those in the literature. An image processing unit is then used to estimate the width, number, and length of the cracks from the segmentation mask. Test results show that the computed crack parameters with SHSnet are exactly the same as that computed with an optical microscope but require ~100× less time. Results demonstrate that SHSnet works equally well in SHCCs with different surface textures, crack density, and widths; the final result was far superior to a conventional technique. This technique also shows promising results in an automatic evaluation of crack parameters relevant to durability and visualizing crack patterns even in the presence of artifacts during progressive testing. The results also demonstrate the necessity to accurately and densely calculate crack length and maximum crack width; else the durability results are expected to be significantly more conservative than the actual value. [ABSTRACT FROM AUTHOR]

Two distinct heat treatments, that is, intercritical quenching combined with low‐temperature tempering (QT) to control the initial quenching temperature, and salt‐bath quenching combined with partitioning (Q&P) to regulate the final quenching temperature, were employed on high‐strength low‐alloy (HSLA) steels to achieve multiphase microstructures characterized by high strength, low yield ratio, and good impact toughness. Comprehensive experiments involving tension test, low‐temperature impact, microstructural observation, and in situ tension have been conducted to compare the microstructures and mechanical properties. It is found that both kinds of specimens can achieve a good match between high strength‐toughness and low yield ratio. The microstructures are composed of lath martensite with ferrite for QT specimen and tempered martensite with bainite for the Q&P specimen, a combination of “soft” and “hard” phases thus resulting in a yield ratio lower than 0.85 for 900 MPa low‐alloy steels. Notably, the Q&P specimen exhibited a markedly superior uniform elongation of 6.1% compared to the QT counterpart of 3.2%, a phenomenon attributed to the work hardening rate during deformation. A combination of strong and weak lath structures in tempered martensite and bainite can induce dislocation propagation and the carbides can act as obstacles to dislocation motion, jointly enhancing work hardening. [ABSTRACT FROM AUTHOR]

Due to the process complexity of the high‐carbon high‐manganese steel (HMnS) in casting and arc welding, this article propose the coaxial powder‐feeding laser cladding (LC) of HMnS coating using self‐developed HMnS powders. Firstly, high‐carbon HMnS coatings are prepared on the 16Mn substrate using coaxial powder‐feeding LC technology. It has a single austenite phase, without large defects such as pores and cracks. Then, ultrasonic shock peening is used to harden the HMnS coating, and the mechanical properties such as microhardness, impact toughness, wear and tensile properties are measured, which prove that HMnS coating has excellent working hardening, plasticity, toughness, and wear resistance properties. Finally, transmission electron microscopy is used to investigate the coupling effects such as dislocations, multiple twinning, and stacking faults on the HMnS coating after tensile fracture (true strain 39.2%). The deformation strengthening mechanism based on the dynamic Hall–Petch effect is revealed. The research results provide a new method for the preparation of high‐carbon HMnS coatings, and a new idea for expanding the application of high‐carbon HMnS. [ABSTRACT FROM AUTHOR]

Background: The size effect and deformation instability exhibited by materials at the micro- and nano-scale constrain the development and application of miniaturized devices. Introducing different defects in materials through different technical means to improve the deformation stability of materials has been the main research point of micro- and nano mechanics. Objective: This paper presents a novel strategy to completely eliminate the instability of microscopic deformations by the introduction of high-density precipitates in aluminum alloys by means of suitable heat treatment. Methods: A suitable heat treatment is used to introduce a high density of precipitates in the 7075 aluminum alloy. Using the Focused Ion Beam technique and in situ micropillar compression tests, micron-sized single-crystal micropillars were fabricated and the size dependence of the strength and strain-hardening behavior of 7075 aluminum alloy was systematically analyzed. Results: Compared with precipitate-free Al–Mg alloy micropillars, the micropillars fabricated from 7075 aluminum alloy exhibited more stable deformation behavior, predominantly due to the impediment of dislocation motion by precipitates. The power-law exponent for yield strength relative to pillar size was determined to approach a near-zero value, indicating a negligible dependency of yield strength on specimen size. Similarly, the smaller the size of micropillar, the higher the hardening rate, which can be rationalized by exhaustion hardening. Conclusions: The proposed method can eliminate the size effect of materials with pillar size above 0.5 μm and leads to a stabilization in deformation behavior. These are advantageous for the application of micro- and nano-sized components in advanced engineering systems. [ABSTRACT FROM AUTHOR]

High-strength steels (HSSs) have been gaining increasing attention in recent years because of their potential application for lightweight structures. Hybrid structural steel I-sections, featured by dissimilar strength grades for constitutive plates, provide a more economical solution to suit bending loading scenario. This study conducted experiments on nine I-sections with Q690 flange plates under four-point loads, incorporating three different web strength grades including Q690, Q460, and Q355. Furthermore, the local buckling behavior of representative I-sections with various section geometries was analyzed using a validated numerical method to understand the role of web strength grade. Test and numerical analysis results revealed that the section with web steel in the strain hardening stage exhibited different levels of ductility among specimens with different strength webs. It was also observed that earlier yielding or inelastic buckling of the lower strength web plate in hybrid I-sections affects the local buckling behavior of I-girders, in terms of moment resistance and rotation capacity. In addition, the initial local imperfection mode used in numerical analysis was found to affect the rotation capacity of I-girders, but the effect of web strength grade remains consistent among I-sections with the same local buckling deformation mode. This study provides further insights into the local buckling behavior of hybrid I-sections subjected to uniform bending, laying the foundation for further development of design methods. [ABSTRACT FROM AUTHOR]

In eccentrically braced frames (EBFs), inelastic behavior is only permitted in the links. All members, except for the links, are designed according to the capacity design concept by using the link overstrength factor, Ω, so that they remain elastic even when the links develop their ultimate strength (including the strain-hardening effect). AISC 341 specifies that the Ω factor of link members must be 1.25 for beam and brace design and 1.1 for column design. In this study, the relevance of the current Ω factor was investigated. A total of 471 K-braced EBF systems with various conditions were designed using a multi-objective optimization technique, and nonlinear dynamic analyses were performed to evaluate the Ω factor. The results indicate that it is reasonable to use the current Ω factor for the design of beam outside link and brace; however, it leads to an overestimation of axial force in columns, especially in the lower stories of tall buildings. From the analysis results, a new Ω factor equation for column design was proposed. It was demonstrated that the structural quantities of 15-story frames designed using the proposed equation decreased by an average of 19% compared to those designed using the current Ω factor. [ABSTRACT FROM AUTHOR]

The high yield ratio and low strain hardening ability of titanium alloys significantly limit their engineering applications. In this work, a Ti65Zr30Cu5 (at.%) alloy with nanoscale α laths was additively manufactured and achieved a high yield strength of 1274 MPa and a high strain hardening rate up to 40% of the shear modulus. Results show that universal basal/pyramidal dislocation reactions occur during the tensile deformation process. This triggers high-density sessile 〈c 〉 dislocation junctions, which accumulate and pin other mobile dislocations. Consequently, abundant dislocation walls are induced, leading to a strong hetero-deformation-induced strain hardening effect. [ABSTRACT FROM AUTHOR]

This article deals with the results of technological tests of pressability (Erichsen's - IE index and capping - limit drawing ratio (LDR)). It also presents on which material parameter (ductility, strain hardening exponent, coefficient of normal anisotropy...) should be given more emphasis when choosing a steel sheet, if stretching stress (uniaxial tension, biaxial tension) dominates during the production of stampings, or if dominates the "pull-pressure" technique (pulling out from under the flange). [ABSTRACT FROM AUTHOR]

Soft clay in the offshore area of the Yangtze River estuary has been investigated considering its basic physical properties. Forty-five unconfined compressive strength tests were conducted on the remolded marine soft clay to investigate the impacts of curing time T, water content w, plasticity index IP, and clay particle content ρc on the thixotropic static shear strength ratio As of the marine soft clay from the Yangtze River estuary. Results show that the stress--strain curves were primarily strain hardening and strain softening curve types. Unconfined compressive strength qu increased with an increase in T. All specimens with different basic physical properties were capable of thixotropic strength recovery. When T = 0-28 days, As increased rapidly, while for T > 28 days, As of most specimens increased slightly or tended to stabilize. The impacts of w, Ip and ρc on As do not follow a consistent pattern, but there is a strong correlation between As and w/wL (wL is the liquid-limit water content). For w/wL < 0.75, As increased with increasing w/wL, whereas for w/wL ≥0.75, As decreased with increasing w/wL. We proposed a simple and widely applicable power function prediction model for the As of the soft clay from the Yangtze River estuary. [ABSTRACT FROM AUTHOR]

Nickel-based single-crystal superalloys are widely used in aerospace and industrial gas turbine blades due to their excellent material properties. However, these alloys are also known for their difficulty in machining due to their superior physical properties. To improve the surface quality of machined parts, this study investigates the effects of different grinding conditions (dry grinding, flood, minimum quantity lubrication (MQL)) on the surface morphology, grinding-induced damage layer, and subsurface microstructure of nickel-based single-crystal superalloys. The experiments show that under MQL conditions, as the wheel speed increases, the grinding marks become more uniform, surface micro-defects decrease, and surface quality improves. A comparison of the thickness of the grinding-induced damage layer (D) obtained from dry grinding, flood, and MQL reveals that MQL cooling is more effective in reducing the damage layer thickness of nickel-based single-crystal superalloys compared to flood cooling. With an increase in wheel speed from 15 to 35 m/s, the thickness of the subsurface damage layer reduced from 14.2 to 11.4 µm using emulsion cooling and from 12.8 to 9.1 µm using MQL cooling. Unlike dry grinding, the use of grinding fluid significantly impacts the subsurface microstructure of the alloy, effectively suppressing work hardening and reducing the thickness of the grinding-induced damage layer, thereby improving the surface quality. It has important theoretical and practical significance to improve the quality of grinding surface. [ABSTRACT FROM AUTHOR]

Grain boundary hardening and precipitation hardening are important mechanisms for enhancing the strength of metals. Here, we show that these two effects can be amplified simultaneously in nanocrystalline compositionally complex alloys (CCAs), leading to near-theoretical strength and large deformability. We develop a model nanograined (TiZrNbHf)98Ni2 alloy via thermodynamic design. The Ni solutes, which has a large negative mixing enthalpy and different electronegativity to Ti, Zr, Nb and Hf, not only produce Ni-enriched local chemical inhomogeneities in the nanograins, but also segregate to grain boundaries. The resultant alloy achieves a 2.5 GPa yield strength, together with work hardening capability and large homogeneous deformability to 65% compressive strain. The local chemical inhomogeneities impede dislocation propagation and encourage dislocation multiplication to promote strain hardening. Meanwhile, Ni segregates to grain boundaries and enhances cohesion, suppressing the grain growth and grain boundary cracking found while deforming the reference TiZrNbHf alloy. Our alloy design strategy thus opens an avenue, via solute decoration at grain boundaries combined with local chemical inhomogeneities inside the grains, towards ultrahigh strength and large plasticity in nanostructured alloys. Grain boundary hardening and precipitation hardening are important mechanisms for enhancing the strength of metals. Here, these two effects are amplified simultaneously, by adding a suitable alloying element, leading to near-theoretical strength. [ABSTRACT FROM AUTHOR]

ABSTRACT This study investigated the fatigue fracture mechanisms and life prediction of clinched joints made from titanium alloy TA1. The fatigue tests revealed that TA1 titanium alloy clinched joints exhibited failure characterized by fracture of the lower plate at three distinct fatigue load levels. Additionally, finite element analysis indicated that cold work hardening enhanced the fatigue performance of these joints. Observations of fracture surfaces using scanning electron microscopy identified the crack source and its propagation path, which correlated with the location of maximum principal stress from the finite element simulations. Fretting wear was also observed in this critical region. Furthermore, fatigue life predictions for TA1 titanium alloy clinched joints were made using Paris' law and the local strain approach. Both methods closely matched experimental results across different fatigue life intervals. Overall, the local strain approach exhibited superior predictive capability compared to Paris' law, taking into account various influencing factors. [ABSTRACT FROM AUTHOR]

Metallic glass fibers have high strength, poor plasticity and low Young's modulus. In this study, it was used as a reinforcement to prepare metallic glass fiber reinforced epoxy composites with different fiber volume contents (20%, 30%, 40%, and 50%). The effect of fiber volume contents on the tensile properties of the metallic glass fiber reinforced epoxy composites was studied by experiment and the finite element analysis method. The experiment and simulation results are in good agreement. The tensile strength and plasticity of the metallic glass fiber reinforced epoxy composites increase with the increase of fiber volume contents. When the fiber volume content is 40% or 50%, a sharply necking feature appeared on the fibers and exhibited improved plasticity, due to the formation of interacting and arresting events of shear bands occurring at the interface between the metallic glass fibers and the epoxy. In addition, the strain hardening due to plastic deformation of the metallic glass fibers further enhanced the tensile strength of the metallic glass fiber reinforced epoxy composites. This is a first step toward toughening the inherently brittle metallic glass fibers under tensile conditions. Highlights: A novel CoFeSiB metallic glass fiber reinforced epoxy resin compositeThe increase of fiber volume fraction improves the tensile strength and plasticity of fiber reinforced composites.The strain hardening due to plastic deformation of the metallic glass fibers further enhanced the tensile strength of the metallic glass fiber reinforced epoxy composites. [ABSTRACT FROM AUTHOR]

Vegetated concrete substrate (VCS) is a kind of ecological cemented soil, which has very wide application prospect in high and steep rock slope eco-protection. Cement is an important component of VCS, but it has high energy consumption and environmental pollution. Fiber reinforcement plays an positive role in improving the mechanical properties of soil, and its use as a substitute for cement content in VCS under the condition of equal strength is rarely investigated. In this study, the unconsolidated-undrained (UU) triaxial compression test of unreinforced substrate as blank control samples (BCS) and reinforced substrate as fiber reinforced samples (FRS) were carried out. The test results showed that the stress-strain curve of VCS can be divided into compaction stage, elastic stage, plastic stage and strain hardening stage. The average peak strength increased by 34.3kPa, 53.6kPa, 218kPa and 81.8kPa as cement content of VCS was 0%,4%, 6% and 8%, respectively. The relationship between the peak strength and cement content of VCS could be better fit by Boltzmann function. The mathematical model of fiber instead of cement in VCS under the condition of equal strength was established. It is found that there is a critical point of cement content according to the mathematical model. The cement of VCS can be completely replaced by plam fiber as the cement content is less than the critical point. While the cement content is higher than the critical point, the cement of VCS can be partially replaced by plam fiber. The decrease of average cement content was 17.23%, 19.00%, 24.27% and 25.34% with 0.2%, 0.4%, 0.6% and 0.8% fiber content in reinforced substrate, respectively. The theoretical method and interpolation method for fiber substitute cement content of VCS under equal strength condition were proposed, which can provide technical guidance for ecological slope protection engineering practice of vegetated concrete. [ABSTRACT FROM AUTHOR]

Cu alloys have been widely used in the manufacture of liners because of their high density, good plasticity, and excellent thermal conductivity. In order to achieve excellent jet stability and penetration performance, it is necessary to further improve the mechanical properties of Cu-based liners. Nevertheless, the simultaneous enhancement of strength and ductility of the Cu alloys remains a huge challenge due to the strength–ductility trade-off phenomenon of metals/alloys. In this study, the microstructure evolution of rare earth Nd-modified Cu alloy and its effect on mechanical properties were investigated using OM, SEM, EBSD, and TEM techniques. The results show that the ultimate tensile strength (218 MPa) and elongation (50.7%) of sample 1 without Nd are the lowest. With increasing Nd content; the tensile strength and elongation of the samples increase; and the mechanical properties of sample 4 are the best, with a tensile strength of 278.6 MPa and elongation of 65.2%. In addition, with the increase in Nd content, not only is the grain size of the Cu-Nd alloy refined, but also the strength and plasticity are improved so that the strength–ductility trade-off phenomenon is improved. The strength improvement is mainly attributed to grain refinement strengthening, dispersion strengthening, and strain hardening. The increase in ductility is mainly related to the improvement of the microstructure heterogeneity by the Nd element. [ABSTRACT FROM AUTHOR]

This study investigates the preparation of ultrahigh-strength AZ80 magnesium alloy bulks using room temperature multidirectional forging (MDF) at different strain rates. The focus is on elucidating the effects of multidirectional loading and strain rates on grain refinement and the subsequent impact on the mechanical properties of the AZ80 alloy. Unlike hot deformation, the alloy subjected to room temperature MDF exhibits a lamellar twinned structure with multi-scale interactions. The key to achieving effective room temperature MDF of the alloy lies in combining multidirectional loading with small forging strains per pass (6%). This approach not only maximizes the activation of twinning to accommodate deformation but ensures sufficient grain refinement. Microstructural analysis reveals that the evolution of the grain structure in the alloy during deformation results from the competition between {10 1 ¯ 2} twinning or twinning variant interactions and detwinning. Increasing the forging rate effectively activates more twin variants, and additional deformation passes significantly enhance twin interaction levels and dislocation density. Furthermore, at a higher strain rate, more pronounced dislocation accumulation facilitates the transformation of twin structures into high-angle grain boundaries, promoting texture dispersion and suppressing detwinning. The primary strengthening mechanisms in room temperature MDF samples are grain refinement and dislocation strengthening. While increased dislocation density raises yield strength, it reduces post-yield work hardening capacity. After two passes of MDF at a higher strain rate, the alloy achieves an optimal balance of strength and ductility, with a tensile strength of 462 MPa and an elongation of 5.1%, significantly outperforming hot-deformed magnesium alloys. [ABSTRACT FROM AUTHOR]

This study used laser additive manufacturing technology to fabricate austenitic–martensitic stainless steel functionally graded materials (ASS-MSS FGM). The microstructure and mechanical properties of ASS-MSS FGM were characterized, and the surface integrity after milling experiments of the ASS-MSS FGM was analyzed. The microstructure of the ASS-MSS FGM exhibited a dense subgrain structure with diverse subgrain types and no fixed growth direction. The microhardness of the ASS-MSS FGM increased from 283 HV to 530 HV due to the increased proportion of the martensitic phase. The ASS-MSS FGM tensile specimens fractured in the austenitic stainless steel region. The tensile strength is 896 MPa, which is increased by 121 MPa compared to ASS. The fracture elongation is 18%, which is increased by 140% compared to MSS. The milling experiments revealed that the degree of work hardening decreased by 8.1% along the building direction of the ASS-MSS FGM. Compared with the austenitic and martensitic layers, the degree and depth of work hardening of the gradient layer were in the transitional zone between them. The microstructure of ASS-MSS FGM after the milling mainly exhibited three deformation phenomena: grain squeezed deformation, grain broken dislodgement, and grain sheared fracture. [ABSTRACT FROM AUTHOR]

AbstractIn the present investigation, the selective laser melting (SLM) technique has been utilized for the 3-dimensional printing (tensile test specimens) of SS316L steel powder at 00 (horizontal) and 900 (vertical) angles. Further, an experimental and finite element analysis approach has been made to analyse the effect of printed orientation or direction on the Hollomon power law parameters (strain hardening exponent (n) and strength coefficient (K)) and ductile damage parameters (fracture strain (εf), stress triaxiality (η) and strain rate (ε̇)). The influence of printing orientation on plastic deformation behavior has also been analysed. The results revealed that 00 angle 3D-printed specimens exhibited 11.05%, 21.97% and 9.50% more yield strength, tensile strength and elongation than 900 angle 3D-printed tensile test specimens. Further, the strain hardening exponent (n) and strength coefficient (K) (Hollomon power law hardening model parameters) for 00 angle 3D-printed specimens are 35.80% and 32.47% more than the 900 angle 3D-printed tensile test specimens respectively. The fracture strain for 00 angle 3D-printed specimens is 37.82% less than the 900 angle 3D-printed tensile test specimens. The percentage difference between FEA and experimental results is less than 5% which shows the good prediction capability of estimated Hollomon power law parameters and ductile damage model parameters with developed FEA model for 00 and 900 3D printed specimens. [ABSTRACT FROM AUTHOR]

In order to reveal the influence of stress paths on the stress-strain characteristics of natural sedimentary soft soil, physical and mechanical properties, conventional triaxial and stress path tests were carried out on the undisturbed soft soils of Tianjin and Hengshui Lake. The systematical investigation was conducted on the stress-strain characteristics and influencing factors of natural sedimentary soft soil under different stress paths. The main conclusions are as follows: stress-strain characteristics of soft soil are changed by the variation of the structural and bonding characteristics. Under the drainage shear, Tianjin soft soil with weaker structural and bonding characteristics reveals the strain hardening characteristics similar to remolded soil, while Hengshui Lake soft soil with stronger structural and bonding characteristics exhibits the strain softening characteristics of undisturbed soil. Due to the presence of structural and bonding characteristics, natural sedimentary soft soil can hear tensile stress and show expansion deformation. The content of clay particles and colloidal particles of Hengshui Lake soft soil are higher than Tianjin soft soil, exhibiting obvious bonding characteristics, higher shear strength and more significant expansion deformation under the axial unloading stress paths. The conclusions can provide reference for the design calculation and constitutive model of natural sedimentary soft soil. [ABSTRACT FROM AUTHOR]

It is highly desired yet challenging to develop advanced elastomers with excellent mechanical properties, including high strength and toughness. In this work, strong and tough rubber/rubber compound vulcanizates were facilely prepared by blending ethylene-propylene-methylene (EPM) and isoprene rubber (IR) together with dicumyl peroxide (DCP) and subsequent vulcanization, since both EPM and IR can be vulcanized synchronously by DCP and the well-crosslinked structure of EPM/IR vulcanizate presented a stable phase separation state. By tuning their composition, EPM/IR vulcanizates could present remarkably improved mechanical strength and toughness, as well as excellent energy dissipation and deformation recovery abilities. Furthermore, EPM/IR/SiO2 nanocomposites with better properties were prepared by introducing silica nanoparticles into EPM/IR vulcanizates. It was found that the high toughness and strength of EPM/IR vulcanizates and EPM/IR/SiO2 nanocomposites mainly resulted from the combination of stretchability of EPM and strain hardening of IR. Their excellent energy dissipation and deformation recovery abilities were related to the macromolecular characteristics of EPM and IR, compatibility between EPM and IR, and their crosslinking dynamics. [ABSTRACT FROM AUTHOR]

Anti-fatigue design in the machining process of aviation material requires advanced processes to enhance the surface integrity and a holistic model which can optimize the process aiming at maximum fatigue life. In the present study, the axial ultrasonic assisted milling process was utilized to machine the Inconel 718 while the process executes the thermomechanical cutting and peening action simultaneously. To optimize the process factors, a hybrid model using a combination of regression analysis and an analytical model was developed to correlate the machining factors, i.e., vibration amplitude, cutting velocity and feed rate to fatigue life. Herein, the former was used to map the process inputs to surface integrity aspects (SIAs), viz. roughness, hardness and residual stress; then, the SIA was mapped to fatigue life through a stress-based approach. The obtained results revealed that there is close agreement between the measured and predicted values of fatigue life where the prediction error is less than two times the dispersion. On the other hand, applying ultrasonic vibration at the highest amplitude together with the maximum feed rate and cutting velocity yield significant improvement in fatigue life, i.e., three times the same condition without ultrasonic vibration in light of the enhancement of compressive residual stress and work hardening of the surface layers. [ABSTRACT FROM AUTHOR]

At present, gradient‐structure alloys with strong properties can be machined by strong surface plastic deformation. This kind of alloy also has high strength, excellent plastic toughness, and work hardening properties. Herein, nanometer polycrystalline nickel–cobalt alloys with grain gradient are studied. The change of mechanical properties and evolution mechanism of internal defects of graded polycrystalline nickel–cobalt alloys under shear loading are emphatically revealed, and the unusual strengthening mechanism brought about by gradient structure is revealed. The results show that grain gradient microstructure can improve the strength and maintain the toughness of the alloy to a certain extent. The uneven grain boundary distribution due to the gradient structure brings different hindering effects to the dislocation movement. Therefore, the mechanical properties exhibited are different from those of uniform microstructure. [ABSTRACT FROM AUTHOR]

A novel Al-Cu-Ni composite, featuring Ni-Al3Ni2/Al3Ni core–shell intermetallics within its matrix produced via powder metallurgy, was subjected to isothermal compression tests at different conditions so as to garner an insight into its hot deformation behaviour. These experiments were conducted from 300 to 500 °C, with strain rates varying from 0.0001 s−1 to 0.1 s−1. It is found that the flow stress is influenced by both strain rate and temperature. As the deformation temperature reduced or the strain rates increased, the peak stress level increased. To characterize the flow stress of the composite, a sine-hyperbolic constitutive equation was developed and the calculated value of activation energy (234 kJ/mol) was substantially higher than that for the self-diffusion of pure Al. Subsequently, the strain-compensated Arrhenius model and the artificial neural network (ANN) model were developed to predict the composite flow behaviour. With a lower average absolute relative error of 2.266%, a smaller root means square error of 0.668 MPa, and a higher correlation coefficient of 0.999 than the Strain-compensated Arrhenius model, the ANN model is more predictable. The processing maps show that the ideal hot working conditions for the composite are between 400 and 500 °C, with strain rates between 0.0001 s−1 and 0.01 s−1 with an efficiency of 37%. The uneven distribution in the shape and size of Core–shell/Al3Ni intermetallic compounds influenced the flow stress curves, leading to dynamic recrystallization (DRX), followed by partial dynamic recovery (DRV), and ultimately strain hardening at 0.01 s−1 & 0.1 s−1. The occurrence of recrystallization and recovery up to a specific strain followed by strain hardening at all the deformation temperatures is a rare phenomenon and has been attributed to the structure and composition of core–shell intermetallics. The occurrence of work hardening at higher strains throughout the operational range of temperatures imparts greater reliability to structural components. [ABSTRACT FROM AUTHOR]

The present study explores the application of single‐step quenching and partitioning (QP) treatments to low‐silicon commercial AISI 4140 steel. Fractions between 4.6% and 7.8% of retained austenite (RA) are stabilized at room temperature. Specimens quenched at 240 °C and partitioned for 10 min exhibit the highest tensile strength, surpassing 2000 MPa, with an elongation at break of up to 10%. This condition marks the effectiveness of austenite in improving tensile properties. Partitioning times exceeding 5 min lead to a second deformation stage, linked to an intense strain‐induced transformation of austenite into martensite. Comparative quenching and tempering (QT) treatments are conducted to highlight the role of RA in enhancing ductility. The QP samples show improved ductility and strain hardening. Furthermore, an energetic approach is employed to highlight the stability of RA by analyzing the difference in the tensile curves observed between QP and QT conditions. A critical value for stability is reached between 5 and 10 min of partitioning. The work proves the viability of successfully applying QP on AISI 4140 achieving high mechanical properties and improved ductility. [ABSTRACT FROM AUTHOR]

Successful management of chalk reservoirs for various subsurface applications as well as construction in chalk/limestone formations rely on descriptions of compaction behaviour commonly predicted from laboratory experiments. This study aims to understand and describe better the compaction behaviour that oil and water-saturated chalk undergo. Seven North Sea Lower Cretaceous chalk samples with initial porosity ranging from 31 to 45% were compacted hydrostatically in the laboratory. The traditionally named elastic, transitional, elastoplastic and strain hardening phases were identified from stress–strain curves. The observed compaction behaviour is described in phenomenological terms based on the interpretation of Biot's coefficient as a measure of grain-to-grain contact area within the chalk frame. Biot's coefficient was derived from elastic wave velocities and bulk density via Gassmann fluid substitution by first approximations assuming a simple calcite-bearing rock frame. Biot's coefficient identifies both elastoplastic and elastic phases in the initial compaction phase traditionally denoted as the elastic phase. The plastic component of the elastoplastic phase presumably originates from closure of micro-crack introduced by unloading and equilibration from core recovery. Biot's coefficient is a reliable indicator of pore collapse, and a specific constant magnitude of purely elastic strain controls the onset of pore collapse. In situ reservoirs presumably only experience the elastic strain during effective stress changes, not the elastoplastic behaviour seen in experiments. Yet, as laboratory experiments often form a calibration background for large-scale models, quantifying the plastic component of elastoplastic phases and pore collapse from pure elastic strain provides new insight to improve models and avoid the unphysical use of porosity as a controlling physical parameter. Highlights: During initial compaction, both elastoplastic and elastic phases exit and are identified from Biot's coefficient. During compaction, a local minimum Biot's coefficient derive from ultrasonic velocities is a reliable indicator of pore collapse. A critical and purely elastic strain derived from applied stress and dynamic moduli is the controlling mechanism of pore collapse. Identification of subphases and a critical pore collapse elastic strain provides new insight into calibration of reservoir model from experiments. [ABSTRACT FROM AUTHOR]

The tempering process is applied in marine 10Ni5CrMoV steel to study microstructure, and mechanical properties by multi‐scale characterizations, strain hardening behavior, and cryogenic toughening mechanism are further investigated. As the tempering temperature increases from 590 to 630 °C, the dislocation density decreases by up to 25% and the austenite volume fraction decreases by up to 35%. Additionally, the morphology of austenite changes from strip to bulk, which weakened the pinning effect on the laths, leading to a coarsened martensite and an increase in the equivalent grain size. Based on the modified Crussard–Jaoul analysis, the specimens at different tempering temperatures exhibit a single‐stage strain hardening behavior during plastic deformation. The increase in strength is attributed to the continuous transformation‐induced plasticity effect and the increasing dislocation density. Furthermore, high austenite volume fraction and the proportion of grain boundary misorientation above 45° promote the release of stress concentration and hinder the propagation of cracks. This results in an increase in the ductile–brittle transition temperature (DBTT) of the specimens from −105 to −135 °C. At a tempering temperature of 610 °C, the specimen demonstrates an outstanding balance between yield strength (868 MPa) and cryogenic toughness (DBTT of −135 °C). [ABSTRACT FROM AUTHOR]

Implementation of existing stress–strain models for cold-formed steel requires the input of key material parameters determined from corner coupon tests on cold-formed portions. This paper proposes various approaches that can accurately describe the stress–strain responses of cold-formed steel by using corner material properties if known, or by using parent material properties and the corner geometry after cold-forming in the absence of corner material properties. First, a comprehensive database of coupon test results of cold-formed steel is assembled. A total of 483 corner coupon test results with 236 full stress–strain curves are collected from 31 sources, covering a large range of steel grades with nominal yield strength varying from 235 to 960 MPa. The applicability of existing empirical models for determination of the enhanced yield strength, ultimate strength, and ultimate strain is carefully evaluated. New predictive expressions for the required input parameters (namely, 0.01% or 0.05% proof stresses for the use of the two-stage Ramberg-Osgood model, and the strain hardening exponent for the use of one-stage material model) are subsequently derived. Prediction performances of the two-stage Ramberg-Osgood model and the one-stage material model are then evaluated against experimental stress–strain curves under different availabilities of primary material parameters. According to the proposed approaches, the minimum required input parameter to utilize these models is only the yield strength of cold-formed steel or, alternatively, the yield strength of the parent metal and corner geometry after cold-forming. The developed models are proved to be accurate in predicting the monotonic stress–strain response (up to the ultimate point) of cold-formed steel, and they are suitable for use in parametric studies and advanced modeling of cold-formed structures. [ABSTRACT FROM AUTHOR]

Eccentrically Braced Frames (EBFs) equipped with steel shear links primarily sustain large deformation demands through inelastic actions in the links, including yielding, bucking, and fracture of the steel plates or weld parts. This failure mode becomes more complex and results in highly nonlinear behavior using Low-Yield-Point (LYP) steels for the construction of the links due to their high strain hardening capacities. The existing analytical models have been presented for links made of normal steel grades, and thus there is a substantial research need for developing an analytical model to capture the actual behavior of links made of LYP steels. To fill this gap, this paper developed both shear-hinge and shear-spring-based models for performance-based evaluation of EBFs equipped with LYP steel shear links, which are more practical models in general-purpose structural analysis programs. The accuracy of the proposed model was assessed by comparing it with existing experimental tests and analytical models. As a result, there is good agreement between the proposed model and test results in terms of initial stiffness, post-yielding stiffness, and strength, which shows significant improvement over existing analytical models. [ABSTRACT FROM AUTHOR]

The tribological phenomena concerning the lubrication regime change (LRC) during bulk metal forming are comprehensively studied. A multi-step cold forward extrusion process shows the evolution of LRC and reveals the shortcomings of the traditional Coulomb friction law. The previous works of the specific author's research group on friction are reviewed, focusing on the LRC during bulk metal forming. Various LRC phenomena from various examples are revealed. It has been found that the drawing and forward extrusion processes are vulnerable to LRC because of significant sliding motion at the material–die interface, and that when the strain hardening of the material is slight, the influence of friction increases, and as a result, the influence of LRC increases excessively. The new findings also include the impact of LRC on the macroscopic phenomena of the process and the reason for the sharp increase in friction coefficient via LRC, which is validated by the work of Wilson. This paper aims to make engineers and researchers think much of the tribology with lubricant in bulk metal forming with a focus on the dependence of tribological phenomena on the state of the lubricants and the irrationality of traditional friction law, especially in the forging of materials with a low strain hardening capability. [ABSTRACT FROM AUTHOR]

Following sustainability in manufacturing, the machining chain can be optimized by either reducing the time and energy consumption of each operation or eliminating the unnecessary operations subjected to keeping the quality of the final product as consistent. However, the roadblock in designing an optimum machining chain is lack of prediction tool to interact between the included operations. In this paper, an integrated algorithm is developed to simulate the surface roughness generation and following modification caused by milling and burnishing, respectively. Predict the surface roughness generation by milling process and its alternation after burnishing. The algorithm works on the basis of clouds of points which were generated in the engagement region of tool and workpiece and their transformation from tool to workpiece coordinate systems. Moreover, some mechanical attributes of the process regarding effect of surface work hardening and elastic rebound were added to the algorithm to enhance the accuracy of simulation. To verify the results, a series of burnishing experiments with multi-roller rotary tool have been carried out on the surface of the finish-milled samples and the surface roughness change was taken into investigation. The obtained results showed that by applying the work hardening and springback effect to predictive algorithm the prediction accuracy of roughness at submicron level enhances up to 50%. It was also found that the most influential parameters influencing the surface roughness after milling-burnishing sequence are milled surface roughness, burnishing force and pass number. In addition, results showed that applying burnishing after rough machining consumes lots of energy to achieve nanoscale surface finish. Accordingly, the sequence of rough-milling, finish-milling and burnishing results in achieving sound surface finish within significantly shorter period of time and applied force. [ABSTRACT FROM AUTHOR]

To ensure consistent performance of additively manufactured metal parts, it is advantageous to identify alloys that are robust to process variations. This paper investigates the effect of steel alloy composition on mechanical property robustness in laser-directed energy deposition (L-DED). In situ blending of ultra-high-strength low-alloy steel (UHSLA) and pure iron powders produced 10 compositions containing 10–100 wt% UHSLA. Samples were deposited using a novel configuration that enabled rapid collection of hardness data. The Vickers hardness sensitivity of each alloy was evaluated with respect to laser power and interlayer delay time. Yield strength (YS) and ultimate tensile strength (UTS) sensitivities of five select alloys were investigated in a subsequent experiment. Microstructure analysis revealed that cooling rate-driven phase fluctuations between lath martensite and upper bainite were a key factor leading to high hardness sensitivity. By keeping the UHSLA content ≤20% or ≥70%, the microstructure transformed primarily to ferrite or martensite, respectively, which generally corresponded to improved robustness. Above 70% UHSLA, the YS sensitivity remained low while the UTS sensitivity increased. This finding, coupled with the observation of auto-tempered martensite at lower cooling rates, may suggest a strong response of the work hardening capability to auto-tempering at higher alloy contents. This work demonstrates a methodology for incorporating robust design into the development of alloys for additive manufacturing. [ABSTRACT FROM AUTHOR]

The effects of an addition of 4 wt pct V on the mechanical properties and microstructure of a Ti–4Al–3Cu–2Fe (wt pct) alloy manufactured by extrusion of compacts of TiH2/Al/Cu/Fe powder blend followed by vacuum annealing were investigated. It was found that the V addition changed the microstructure of the alloy from lamellar structure to basket-wave structure, increased the volume fraction of β phase from 47 to 53 pct, and reduced the average α lamella thickness significantly from 4.0 to 1.5 μm. Surprisingly, these compositional and microstructural changes cause only a small increase of the yield stress (from 1132 to 1151 MPa) and elongation to fracture (from 6.1 to 6.5 pct), but the strain hardening rate of the alloys are substantially enhanced over a narrow strain range of 0.9-1.7 pct, leading to a clear increase of the ultimate tensile strength from 1184 to 1252 MPa. The main mechanism for the microstructural changes caused by the V addition is the enhanced stabilization of β phase by V atoms and the growth restriction of α lamellae by V partitioning between α and β phases. The enhancement of strain hardening rate can be attributed to the enhance the number density of the α/β interfaces associated with the decrease of the α lamella thickness and which provides more effective barriers for the movement of dislocations. [ABSTRACT FROM AUTHOR]

Cold spray is a solid-state additive manufacturing technology and has significant potential in component fabrication and structural repair. However, the unfavourable strength–ductility synergy in cold spray due to the high work hardening, porosity and insufficient bonding strength makes it an obstacle for real application. In recent years, several methods have been proposed to improve the quality of the cold-sprayed deposits, and to achieve a balance between strength and ductility. According to the mechanism of how these methods work to enhance metallurgical bonding, decrease porosity and reduce dislocation densities, they can be divided into four groups: (i) thermal methods, (ii) mechanical methods, (iii) thermal–mechanical methods and (iv) optimisation of microstructure morphology. A comprehensive review of the strengthening mechanism, microstructure and mechanical properties of cold-sprayed deposits by these methods is conducted. The challenges towards strength–ductility synergy of cold-sprayed deposits are summarised. The possible research directions based on authors' research experience are also proposed. This review article aims to help researchers and engineers understand the strengths and weaknesses of existing methods and provide pointers to develop new technologies that are easily adopted to improve the strength–ductility synergy of cold-sprayed deposits for real application. [ABSTRACT FROM AUTHOR]

Featured Application: This paper develops an innovative post-weld composite treatment process, which can significantly improve the formability of aluminum alloy tailor welded blanks compared with the traditional single post-weld treatment method. The mechanical properties and cross-sectional geometric dimensions of the fusion zone (FZ), heat affected zone (HAZ), and base metal (BM) of 6xxx series aluminum alloys are inconsistent after filler wire welding, which reduces the formability of aluminum alloy tailor welded blanks (TWBs). This paper proposes a post-weld cold rolling-solution heat treatment (PWCR-SHT) composite process, and the effects of weld excess metal, plastic deformation, and SHT on the formability of aluminum alloy TWBs are studied. The results show that the PWCR-SHT composite process eliminates the weld excess metal and internal pores, reduces the stress concentration at the weld toe, eliminates the local strain hardening behavior, and causes recrystallization in the FZ region. The cupping value of aluminum alloy TWBs using SHT is 105% of BM, in comparison, the cupping value of aluminum alloy TWBs using the PWCR-SHT composite process is 119% of BM, which is the result of the combined effect of geometric dimensions consistency and mechanical properties consistency. [ABSTRACT FROM AUTHOR]

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Layered structures comprising coral sand and gravel have been observed in hydraulic filled foundations in the coral reefs in the South China Sea, leading to anisotropy in their physical and mechanical properties. However, the effect of a layered structure on the strength and deformation of the coral soil foundation remains unclear. In this study, a series of large-scale triaxial compression tests and step-loading tests were carried out on four types of samples, i.e., clean coral sand, clean coral gravel, sand-over-gravel layered sample, and gravel-over-sand layered sample, to investigate the impact of confining pressure and the layered structure on the strength and failure modes of these soils. The results indicate that the stress–strain relationships of all samples predominantly exhibit strain hardening under drained conditions. Under identical confining pressures, the peak strength of clean coral sand is the lowest, while that of coral gravel is the highest. The peak strengths of the two layered samples fall between these extremes, with the gravel-over-sand layered sample exhibiting higher strength. All four samples have similar peak friction angles, slightly exceeding 40°. The difference in peak strength among the four types of samples is attributed to the variations in cohesion, with the cohesion of clean coral gravel being up to four times that of clean sand, and the cohesion of layered samples falling between these two. Both clean sand and clean gravel samples exhibit a bulging phenomenon in the middle, while the layered samples primarily exhibit bulging near the coral gravel layer. In the step-loading tests, the bearing capacity of the layered samples falls between those of clean coral sand and coral gravel, with the gravel-over-sand layered samples demonstrating higher strength. Moreover, the p-s curve of the gravel-over-sand layered samples obtained from the large-scale triaxial apparatus under a confining pressure of 400 kPa resembles that from the plate load tests on the same samples. [ABSTRACT FROM AUTHOR]

Obtaining precise parameters of deformation modes remains a significant challenge in materials science research. Critical resolved shear stresses (CRSS) and work hardening, particularly in hexagonal metals, are crucial parameters for constitutive laws in crystal plasticity. This paper presents a novel approach to determine CRSS and specific hardening matrix coefficients for commercially pure zirconium (α -Zr) at room temperature. In situ methods are employed to measure displacement fields using grids applied to the sample surface, while a comprehensive characterization of the activated deformation systems is performed via SEM and TEM. The CRSS for prismatic 〈 a 〉 , pyramidal 〈 a 〉 , and 10 1 ¯ 2 and 1 1 2 ¯ 1 twinning systems, as well as the self-hardening for prismatic slip and several work-hardening coefficients (for prismatic/prismatic and prismatic/pyramidal interactions), are reported in Zr single crystals. Finally, the results are compared with findings from the literature and atomistic simulations. [ABSTRACT FROM AUTHOR]

The interface between soil and concrete in cold climates has a significant effect on the structural integrity of embedded structures, including piles, liners, and others. In this study, a novel temperature control system was employed to conduct direct shear tests on this interface. The test conditions included normal stress (25 to 100 kPa), temperature (ranging from 20 to −6 °C), water content (from 10 to 19%), and shear rates (0.1 to 1.2 mm/min). Simultaneously, the deformation process of the interface was continuously photographed using a modified visual shear box, and the non-uniform deformation mechanism of the interface was analyzed by combining digital image correlation (DIC) technology with the photographic data. The findings revealed that the shear stress–shear displacement curves did not exhibit a discernible peak strength at elevated temperatures, indicating deformation behavior characterized by strain hardening. In the frozen state, however, the deformation softened, and the interfacial ice bonding strength exhibited a positive correlation with decreasing temperature. When the initial water content was 16% and the normal stress was 100 kPa, the peak shear strength increased significantly from 99.9 kPa to 182.9 kPa as the test temperature dropped from 20 °C to −6 °C. Both shear rate and temperature were found to have a marked effect on the peak shear strength, with interface cohesion being the principal factor contributing to this phenomenon. At a shear rate of 0.1 mm/min, the curve showed hardening characteristics, but at other shear rates, the curves exhibited strain-softening behavior, with the softening becoming more pronounced as shear rates increased and temperatures decreased. Due to the refreezing of interfacial ice, the residual shear strength increased in proportion to the reduction in shear rate. On a mesoscopic level, it was evident that the displacement of soil particles near the interface exhibited more pronounced changes. At lower shear rates, the phenomenon of interfacial refreezing became apparent, as evidenced by the periodic changes in interfacial granular displacement at the interface. [ABSTRACT FROM AUTHOR]

This paper aims to develop a new continuous strength method (CSM) to more accurately predict the strain-hardening characteristics of high-strength aluminum alloy circular hollow sections (CHSs) under axial compression. A total of 11 stub column specimens made of 7A04-T6 and 6061-T6 aluminum alloys underwent testing. Additionally, 16 sets of experiment data were gathered from open sources, encompassing various aluminum alloy types such as 6082-T6, 6061-T6, and 6063-T5. Validated by experimental result, the finite element (FE) model was applied in a series of comprehensive parameter studies, supplementing the limited test result of high-strength aluminum alloy stub columns. Based on the experiment and FE results, this paper proposes a new CSM relation to determine the cross-sectional resistance of high-strength non-slender CHS aluminum alloys under compression. The cross-sectional resistance obtained from tests are compared with predicted strengths determined using the European code, as well as the solution of the CSM proposed in a previous study and in this paper. The comparison illustrates that the strength predictions in the European code and the previous study are conservative. Compared with the European code and the previous study, the strength prediction formula proposed in this paper improves accuracy by 11% and 5%, respectively, while reducing scatter by 8.4% and 2%, respectively. [ABSTRACT FROM AUTHOR]

The tension-compression yield asymmetry caused by the strengthening of Mg-Zn-Gd-Zr alloy due to extrusion deformation is an important issue that must be addressed in its application. In this study, the effects of loading direction on the tensile and compressive mechanical behaviors of Mg-5Zn-2Gd-0.2Zr alloy were systematically investigated. As the loading angle (the angle between the loading direction and the extrusion direction) increases from 0° to 30°, 45°, 60° and 90°, the tensile yield strength decreases more significantly than the compressive yield strength. Consequently, the tension-compression yield asymmetry is gradually improved. Additionally, the ultimate compressive strength decreases more markedly than the ultimate tensile strength with the increment of the loading angle. In tensile tests conducted at 0°, 30° and 45°, two distinct stages of decreasing strain hardening rates are typically observed. For the 60° and 90° tensile tests, one unusual ascending stage of strain hardening rate is observed. For all compressive tests, three stages of strain hardening are consistently noted; however, the increment in strain hardening rate caused by {10–12} extension twinning decreases with the increasing loading angle. A model combining loading angle and Schmid factor distribution was established. The calculated results indicate that the dominant deformation modes during the yielding process also vary significantly with the loading conditions. This clarification highlights the differences in yield strength variations between tension and compression. Finally, an analysis of the plane trace and crack propagation direction near the fracture surface reveals the fracture mechanisms associated with tensile and compressive tests at different loading directions. This study promotes understanding of the mechanical behaviors of Mg-5Zn-2Gd-0.2Zr alloy under different loading directions, and helps to thoroughly elucidate the anisotropic effects of texture on the mechanical properties of magnesium alloys. [ABSTRACT FROM AUTHOR]

It is common to observe that monotonic K1c (lab air) and K1scc (NaCl solution) decrease with increasing YS of an alloy. K1c is measured in lab air and K1scc in an aqueous solution such as NaCl. It is noted that K1c is not considered as a subcritical parameter while K1scc is. Interestingly, for a given alloy, both these parameters seem to be inter-related. That is, K1scc is linearly related to K1c, such that K1scc increases with increasing K1c. This may indicate that plasticity is affecting the K1scc behavior. This article looks into the conditions that affect K1scc for steels, Al-alloys, and Ti-alloys. This linear variation of K1scc with K1c seems to be independent of alloy YS, E, microstructure, and work hardening rate. This observation seems similar in all three systems of alloys. How these parameters are interrelated is analyzed and discussed in detail. [ABSTRACT FROM AUTHOR]

In this work, the texture evolution, mechanical properties, and formability of cold-rolled lightweight steel annealed at 500, 600, 700, and 800 °C for 30 min were investigated. The phases in the annealed specimens mainly included ferrite, austenite, and martensite. The retained austenite showed a trend of increasing and then decreasing with the increase in annealing temperature. At the annealing temperature of 700 °C, the retained austenite content reached the maximum value of 53.0%, resulting in a large amount of martensitic TRIP effect during the subsequent deformation. So the steel obtained the optimal mechanical properties with the ultimate tensile strength of 1613 MPa, ultimate elongation of 30.2%, and largest product of strength and ductility of 48.7GPa%. In addition, the annealing temperature of 700 °C was conducive to the stamping texture of {111} < 110> orientation, as well as higher strength, and the plastic strain ratio (r), the strain hardening index (n), and the flexural strength ratio (ReL/Rm) were 1.25, 0.55, and 0.41, respectively, the material obtained excellent formability. [ABSTRACT FROM AUTHOR]

A series of biobased aliphatic‐aromatic copolyesters, poly(pentylene dodecanoate‐co‐furandicarboxylates) (PPeDFs) were synthesized via an esterification and polycondensation melt process. The copolyesters were characterized using gel permeation chromatography, Fourier transform infrared spectroscopy, 1H NMR spectroscopy, differential scanning calorimetry, thermogravimetric analysis, wide angle x‐ray scattering, and tensile testing. The thermal transition behavior was strongly dependent on composition, with the melting and glass transition temperatures reaching a minimum at approximately equimolar ratio of D to F. All copolyesters were stable below 300°C with their R600 (the weight of material remaining at 600°C) values increasing with F fraction. PPeD to PPeDF30 (e.g., mole ratio D/F = 7:3) show sharp PPeD crystalline reflections only while broad PPeF reflections are shown in PPeF and PPeDF90. PPeDF40 to PPeDF80 showed both crystal structures. The fractional crystallinity for the PPeD was much higher than PPeF and the fractional crystallinity of the copolymers showed a minimum at D/F ratios closer to the latter. The stress at break and modulus both exhibited maxima at D/F ratios that were either high or low, but somewhat surprisingly a strong maximum in percent elongation at break of over 600% occurs at PPeDF40. For this composition, a typical plastic behavior curve was found including a yield point, high elongation at break, and strain hardening. Highlights: Poly(pentylene dodecanoate‐co‐furandicarboxylates) (PPeDFs) are synthesizedMechanical properties, a function of D:F ratio. High elongation at 40 mol% F.Two melting temperatures/crystal structures, one PPeD, the other PPeFGlass transition temperature minimum at intermediate D:F ratios [ABSTRACT FROM AUTHOR]

This study entails comprehensive analyses of the temperature dependence of tensile properties and strain-controlled low cycle fatigue behavior exhibited by ASTM A302 grade C steel, which is specifically a manganese-molybdenum-nickel alloy. Tensile strength at elevated temperature ranges from 400 to 428 °C closely approximates those measured under ambient conditions, while the ductility properties show a noteworthy increase compared to ambient temperature testing conditions. Cyclic stress responses at elevated temperatures are characterized by two discernible stress cyclic hardening phases. Fatigue lives of the materials tested at 400, and 428 °C reveals a significantly prolonged fatigue life compared to testing under ambient temperature conditions. The transition of fatigue life for specimens tested under ambient temperature conditions is approximately two times shorter than that observed under elevated temperature conditions. The substantial extension of fatigue lives is attributed to the strengthening effect of the peak dynamic strain aging within the test temperature range predominates over the adverse effects of elevated temperature conditions. Drawing from the experimental findings, comprehensive derivations of cyclic stress–strain responses and fatigue properties have been formulated to elucidate the effects of elevated temperature conditions. [ABSTRACT FROM AUTHOR]