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The article presents a list of articles related to materials science published in volumes 39, 40, and 41. The articles include "Adhesively-bonded joints and repairs in metallic alloys, polymers and composite materials," "Observations of common microstructural issues associated with dynamic deformation phenomena: Twins, microbands, grain size effects, shear bands, and dynamic recrystal," and "Role of entropy of fusion in phase transformation and selfdiffusion."

Purpose: The purpose of the work is a complex review of methods applied industrially as case hardening. The paper contains an overview of scientific and development works on surface case hardening methods, especially carburising and quenching, described in the literature from 2001-2020. Design/methodology/approach: State-of-the-art was reviewed by a critical review of the world literature published in 2001-2022, including theoretical work, scientific research, and industry reports. An additional examination of the state of the art was conducted in terms of patent works. Findings: The period of 2001-2020 was a time of intensive work on the modernisation of case hardening techniques to improve the repeatability and uniformity of the produced layers and minimise deformations after hardening. Developing computing technologies have played a large part in this progress. New technologies have also been developed. Research limitations/implications: The review of papers and patent databases was limited to databases providing English-language content options. Practical implications: Case hardening is a crucial stage of steel heat treatment in almost every industrial branch: mechanical, tool, automotive, railway, and aviation. Originality/value: A synthetic review of case hardening methods was presented, particularly carburizing and quenching methods; it also analysed the possibilities and directions of their development. conducted in terms of patent works. Findings: The period of 2001-2020 was a time of intensive work on the modernisation of case hardening improve the repeatability and uniformity of the produced layers and minimise deformations after hardening. computing technologies have played a large part in this progress. New technologies have also been developed. Research limitations/implications: The review of papers and patent databases was limited to databases Englishlanguage content options. Practical implications: Case hardening is a crucial stage of steel heat treatment in almost every industrial tool, automotive, railway, and aviation. Originality/value: A synthetic review of case hardening methods was presented, particularly carburizing methods; it also analysed the possibilities and directions of their development. Keywords. Heat treatment, hardening, quenching, distortions, carburizing, simulation Reference to this paper should be given in the following way: E. Wołowiec-Korecka, Case hardening development review (2001-2020). [ABSTRACT FROM AUTHOR]

Grain boundaries (GBs), which are among the mechanical properties of a material, are a microstructural aspect that contributes to the overall behavior of metal. A deep understanding of the behavior of the GBs' deformation, dislocation, and fracture will encourage the rapid development of new materials and lead to the better operation and maintenance of materials during their designed lifetimes. In this study, an integrated image processing toolset is proposed to provide an expeditious approach to extracting GBs, tracking their location, and identifying their internal deformation. This toolset consists of three integrated algorithms: image stitching, grain matching, and boundary extraction. The algorithms are designed to simultaneously integrate high and low spatial resolution images for gathering high-precision boundary coordinates and effectively reconstructing a view of the entire material surface for the tracing of the grain location. This significantly reduces the time needed to acquire the dataset owing to the ability of the low spatial resolution lens to capture wider areas as the base image. The high spatial resolution lens compensates for any weakness of the base image by capturing views of specific sections, thereby increasing the observation flexibility. One application successfully described in this paper is tracking the direction of the metal grain deformation in global coordinates by stacking a specific grain before and after the deformation. This allows observers to calculate the direction of the grain deformation by comparing the overlapping areas after the material experiences a load. Ultimately, this toolset is expected to lead to further applications in terms of observing fascinating phenomena in materials science and engineering. [ABSTRACT FROM AUTHOR]

This article explores the explicit modeling of the pseudoelastic response of porous shape-memory alloy (SMA) thick-walled cylinders under internal and external pressure. It discusses various constitutive models for SMAs and porous SMAs, including micro-mechanical and phenomenological models. The article proposes an explicit solution for a three-dimensional phenomenological model using the generalized differential quadrature method. It also discusses the initiation and propagation of phase transformations in porous SMAs, as well as the mechanical behavior of porous SMAs at low temperatures. The article presents a mathematical model for simulating the behavior of porous SMAs and describes the calculation of stress, transformation strains, and other variables. It discusses the discretization of a highly nonlinear differential relation using the GDQ method and validates the numerical solution through comparisons with analytical expressions and previous studies. The article analyzes stress and strain distribution in dense and porous SMA cylinders and discusses the use of an explicit model to analyze stress and deformation fields in pressurized cylinders. It examines the stress distribution along the wall of a cylinder under different temperatures and pressures, as well as the distribution of residual stresses and the recovery of transformation strains during unloading. The article also discusses the deformation behavior of SMAs under internal and external pressure and presents an explicit constitutive model for studying the behavior of dense and porous SMAs in pressurized cylinders. Finally, it provides a list of references to research papers and articles on materials science and engineering, covering various topics related to shape memory alloys. [Extracted from the article]

The characteristics of temperature change on die and billet are very complex during the deformation process because of the interaction between them and some unstable external factors. In this paper, the numerical simulation model for the crank shaft die forging was established by means of the rigid-plastic FEM method. The model was validated by optical non-contact 3D measurement-ATOS. Based on available research results, this paper explored the effect of temperature conditions on material deformation and die wear. Three parameters, press velocity and initial temperature of billet and die, were chosen to illustrate the effects. From the experimental results, the effect of process parameters on deformation ability of the material is simple, while the effect on die wear is relatively complicated. The press velocity plays an important role on die wear when the initial temperature of the billet has larger influence on material deformation. A conclusion can be drawn that when the initial temperature of the billet is 1100 °C, the initial temperature of the die is 250 °C, and the velocity is kept in the range of 200-300 mm/s, the optimum solution for deformation ability of the material and die wear can be obtained. It is possible for the conclusion to be extended further for the control of temperature condition to optimize die life and material deformation. [ABSTRACT FROM AUTHOR]

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

Auxetic materials are those which exhibit negative Poisson’s ratio, i.e. these solids expand transversely when stretched longitudinally. In recent years the concept of semi-auxetics has been examined for cellular solids based on combination of re-entrant and hexagonal microstructures. In this paper we identify a type of rotating unit that gives positive Poisson’s ratio so that a study can be made on rotating sub-structures that exhibit both positive and negative Poisson’s ratio characteristics. A second type of rotating geometry, whose Poisson’s ratio shifts from negative to positive as stretching increases, has also been identified. Based on kinematical studies we explore the relationship between the on-axis Poisson’s ratios in terms of novel lattice geometry and the magnitude of deformation. [ABSTRACT FROM AUTHOR]

This paper proposes a pseudo-haptic feedback method conveying simulated soft surface stiffness information through a visual interface. The method exploits a combination of two feedback techniques, namely visual feedback of soft surface deformation and control of the indenter avatar speed, to convey stiffness information of a simulated surface of a soft object in virtual environments. The proposed method was effective in distinguishing different sizes of virtual hard nodules integrated into the simulated soft bodies. To further improve the interactive experience, the approach was extended creating a multi-point pseudo-haptic feedback system. A comparison with regards to (a) nodule detection sensitivity and (b) elapsed time as performance indicators in hard nodule detection experiments to a tablet computer incorporating vibration feedback was conducted. The multi-point pseudo-haptic interaction is shown to be more time-efficient than the single-point pseudo-haptic interaction. It is noted that multi-point pseudo-haptic feedback performs similarly well when compared to a vibration-based feedback method based on both performance measures elapsed time and nodule detection sensitivity. This proves that the proposed method can be used to convey detailed haptic information for virtual environmental tasks, even subtle ones, using either a computer mouse or a pressure sensitive device as an input device. This pseudo-haptic feedback method provides an opportunity for low-cost simulation of objects with soft surfaces and hard inclusions, as, for example, occurring in ever more realistic video games with increasing emphasis on interaction with the physical environment and minimally invasive surgery in the form of soft tissue organs with embedded cancer nodules. Hence, the method can be used in many low-budget applications where haptic sensation is required, such as surgeon training or video games, either using desktop computers or portable devices, showing reasonably high fidelity in conveying stiffness perception to the user. [ABSTRACT FROM AUTHOR]

Web-reinforced composite sandwich panels exhibit good mechanical properties in one-way bending, but few studies have investigated their flexural behavior and deformation calculation methods under conditions of four simply supported edges. This paper studies the bending performance of and deformation calculation methods for two-way web-reinforced composite sandwich panels with different web spacing and heights. Polyurethane foam, two-way orthogonal glass-fiber woven cloth and unsaturated resin were used as raw materials in this study. Vacuum infusion molding was used to prepare an ordinary composite sandwich panel and 5 web-reinforced composite sandwich panels with different spacing and web heights. The panels were subjected to two-way panel bending tests with simple support for all four edges. The mechanical properties of these sandwich panels during the elastic stage were determined by applying uniformly distributed loads. The non-linear mechanical characteristics and failure modes were obtained under centrally concentrated loading. Finally, simulations of the sandwich panels, which used the mechanical model established herein, were used to deduce the formulae for the deflection deformation for this type of sandwich panel. The experimental results show that webs can significantly improve the limit bearing capacity and flexural rigidity of sandwich panels, with smaller web spacing producing a stronger effect. When the web spacing is 75 mm, the limit bearing capacity is 4.63 times that of an ordinary sandwich panel. The deduced deflection calculation formulae provide values that agree well with the measurements (maximum error <15%). The results that are obtained herein can provide a foundation for the structural design of this type of panel. [ABSTRACT FROM AUTHOR]

The increased spatial resolution of a new characterization technique, precession electron diffraction (PED), makes possible the very accurate and automated quantitative characterization of technically interesting materials that historically have been difficult to analyze due to their dimensions and/or degree of deformation, including specifically ultrafine-grained metallic structures with high dislocation densities. PED, when coupled with the novel post-processing techniques that have been rigorously developed and presented for the first time in this paper, such as applying a Kuwahara filter to improve the angular resolution of the technique, makes it possible to determine grain size, texture, the density and spatial distribution of geometrically necessary dislocations, crystal orientation gradients, and the character of grain boundaries at the relevant length scale (the nanoscale) for such ultrafine-grained materials. The methods detailed in this paper place the determination of key microstructural features on a quantitative, rather than qualitative footing. These techniques have been applied to a hexagonal close-packed α-titanium. The results include the correlation between defect structure and microstructure with a nanometer resolution, the identification of regions containing few geometrically necessary dislocations, the quantification of dislocation densities in cell walls, and the quantification of deformation type in a statistically meaningful fashion. [ABSTRACT FROM AUTHOR]

In previous work, it has been shown that any suitably smooth plane proper-orthogonal tensor field can serve as a rotation tensor for generating a plane finite deformation. In this paper, this previous analysis is used to study plane finite twin deformations. We show that given a defined smooth curve which separates two arbitrarily prescribed rotation fields, a twin deformation field can be generated in a neighborhood surrounding such curve. Examples are presented for cases where the Jacobian of the finite deformation field is discontinuous or continuous across the defined curve. Twinning in an elastic region is also analyzed in some detail. [ABSTRACT FROM AUTHOR]

The deformation of structural alloys presents problems for power plants and aerospace applications due to the demand for elevated temperatures for higher efficiencies and reductions in greenhouse gas emissions. The materials used in such applications experience harsh environments which may lead to deformation and failure of critical components. To avoid such catastrophic failures and also increase efficiency, future designs must utilise novel/improved alloy systems with enhanced temperature capability. In recognising this issue, a detailed understanding of creep is essential for the success of these designs by ensuring components do not experience excessive deformation which may ultimately lead to failure. To achieve this, a variety of parametric methods have been developed to quantify creep and creep fracture in high temperature applications. This study reviews a number of well-known traditionally employed creep lifing methods with some more recent approaches also included. The first section of this paper focuses on predicting the long-term creep rupture properties which is an area of interest for the power generation sector. The second section looks at pre-defined strains and the re-production of full creep curves based on available data which is pertinent to the aerospace industry where components are replaced before failure. [ABSTRACT FROM AUTHOR]

Double groove ball-section ring (DGBR) is an important part of bearing rings. Cold DGBR rolling is an advanced continuous and local plastic forming technique by reducing cross section and increasing the diameter of ring blanks between rotating roll, and can directly obtain the DGBR with good mechanical properties. In this paper, the cold DGBR rolling processes from some initially rectangular blanks are investigated by using 3D-FE numerical simulation to reveal its deforming rules. Firstly, by analyzing the dimension relationship between rectangular blank and deformed ring, a new blank size design method is proposed based on rolling ratio and the volume conservation law, and thus a series of different original blanks can be precisely designed under different rolling ratios for a same final required DBGR. Secondly, under the ABAQUS/Explicit software environment, a reliable guide roll adaptive control-based 3D-FE model for cold DGBR rolling process is built via elastic-plastic dynamic explicit finite element method. Finally, several rectangular blanks are designed under different roll ratios and the deforming behaviors of cold DGBR rolling process are investigated with thorough numerical simulation. The results show that: (1) the maximum radial thickness of ring H reduces firstly slowly and then rapidly after the ball groove achieves its final shape; (2) the diameters of the ring expand gradually during the whole process and no sudden change occurs just when the final shape of the ball groove is completely formed; (3) the largest deformation occurs around the ball groove all the time under small rolling ratio; while under large rolling ratio, it occurs first around the ball groove and then gradually transfers to the ring outer surface; and (4) the inhomogeneous deformation degree increases with the progress of the process, and for final parts, it increases slowly first with the increasing of roll ratio and then fast when the roll ratio is greater than a certain value. These results will not only reveal the forming mechanisms of cold DGBR rolling process but also provide a basis to blank optimum design and process adaptive control of the relevant profiled ring rolling processes. [ABSTRACT FROM AUTHOR]

Severe plastic deformation (SPD) techniques have recently been developed for producing bulk ultrafine grained metallic materials. High pressure torsion (HPT) produces finer microstructures than those achieved by other SPD processes because of the higher imposed strain and hydrostatic pressure. It is known that HPT-processed metals show a highly heterogeneous microstructure not only along the radius due to the nature of torsional deformation but also through the thickness. Since the sample size for HPT is small, the local properties of HPT-processed specimens have not been investigated yet. In this paper, we propose a method to obtain stress-strain curves from nanoindenting curves by combining the finite element method and the recursion method. The nanoindentation technique was employed to elucidate the local mechanical properties, especially the stress-strain behavior. The method to extract the stress-strain curves from the load-displacement curves obtained by nanoindentation tests was applied to the edge region of the HPT-processed sample. The extracted properties correlated well with experimental results qualitatively.` [ABSTRACT FROM AUTHOR]

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

Severe plastic deformation (SPD) of titanium creates an ultrafine-grained (UFG) microstructure which results in significantly enhanced mechanical properties, including increasing the high cycle fatigue strength. This work addresses the challenge of maintaining the high level of properties as SPD processing techniques are evolved from methods suitable for producing laboratory scale samples to methods suitable for commercial scale production of titanium semi-products. Various ways to optimize the strength and fatigue endurance limit in long-length Grade 4 titanium rod processed by equal channel angular pressing (ECAP) with subsequent thermal mechanical treatments are considered in this paper. Low-temperature annealing of rods is found to increase the fatigue limit, simultaneously enhancing UFG titanium strength and ductility. The UFG structure in titanium provides an optimum combination of properties when its microstructure includes mostly equiaxed grains with high-angle boundaries, the volume fraction of which is no less than 50%. [ABSTRACT FROM AUTHOR]

In this paper, the plastic deformation behavior and strain homogeneity of the ZK60 Mg alloy during the multi-pass cyclic extrusion and compression (CEC) was simulated using the finite-element method (FEM) with a view to provide an insight into the mechanics of the process. Physical modeling (PM) experiment with same alloy was carried out to verify the results of the numerical simulations. The results show that two vortex flow regions with opposite flow direction are formed inside the cylindrical workpiece during CEC deformation. Although the deformation is inhomogeneous in both end regions of workpiece, a uniform region of equivalent strain exists, and the extent of uniform deformation increased with the increase in workpiece length. [ABSTRACT FROM AUTHOR]

This paper has clarified the anelasticity of 8Y-FSZ/α-alumina composites wherein the 8Y-FSZ phases are dispersed like islands. The amount of anelastic strain generated and the manner of anelastic deformation were compared to those of monolithic 8Y-FSZ. The anelastic strains of six kinds of 8Y-FSZ/α-alumina, as well as of monolithic 8Y-FSZ and monolithic α-alumina, were measured. The results showed that the anelastic strain was produced even in the composite where 8Y-FSZ phases existed as islands, and that the more the anelastic strain produced, the higher the volume fraction of 8Y-FSZ. In addition, the composition with a fully densified alumina phase had the effect of inhibiting anelastic strain in the 8Y-FSZ phase. [ABSTRACT FROM AUTHOR]

Some basic aspects of electromagnetic radiation (EMR) emission during quasi-static plastic deformation and crack propagation in ASTM B 265 grade 2 titanium sheets are reported in this paper. It has been observed that titanium emits several intermittent EMR signals starting near the yield and continuing up to fracture. The EMR emissions are sensitive to the applied strain rates. The number of EMR emissions shows a parabolic variation with strain rate, exhibiting a maxima. It appears that the temporary pinnings of the dislocations injected from the crack tip, which is essential for the emission of EMR as described in a recent model by the authors, do not adequately occur at high as well as low strain rates. At elevated temperatures, the square of the EMR amplitude is observed to be proportional to $$ \exp {\left( { - {mU} \mathord{\left/ {\vphantom {{mU} {kT}}} \right. \kern-\nulldelimiterspace} {kT}} \right)}, $$ where U is the activation energy for the movement of jogs, k the Boltzmann constant, T the temperature and m ≤ 1.0. [ABSTRACT FROM AUTHOR]

The application of severe plastic deformation (SPD) to bulk metals provides the opportunity of achieving grain sizes in the submicrometer and nanometer range. Several different SPD processing techniques are now available including Equal-Channel Angular Pressing (ECAP), High-Pressure Torsion (HPT) and Accumulative Roll-Bonding (ARB). This paper examines the principles of grain refinement using ECAP and gives examples of the advantageous properties that may be achieved including increased strength at ambient temperatures and a superplastic forming capability at elevated temperatures. [ABSTRACT FROM AUTHOR]

Abstract: A study of possibilities given by the developed Cellular Automata–Finite Element (CAFE) multi-scale model for prediction of the initiation and propagation of micro-shear bands and shear bands in metallic materials subjected to plastic deformation is described in the paper. Particular emphasis in defining the criterion for initiation of micro-shear and shear bands, as well as in defining the transition rules for the cellular automata, is put on accounting for the physical aspects of those phenomena occurring in two different scales in the material. The proposed approach led to the creation of the real multi-scale model of strain localization. This model predicts material behavior in various thermo-mechanical processes. Selected examples of applications of the developed model to simulations of metal forming processes, which involve strain localization, are presented in the paper. An approach based on the Smoothed Particle Hydrodynamic, which allows to overcome difficulties with remeshing in the traditional CAFE method, is presented in the paper as well. In this approach remeshing becomes possible and mesh distortion, which limits application of the CAFE method to simple deformation processes, is eliminated. [Copyright &y& Elsevier]

This paper presents some new results on the emission of electromagnetic radiation (EMR) during plastic deformation, crack initiation and propagation, and fracture of uncoated and tin–coated 0.15% carbon steel sheets. Intermittent EMR emissions have been observed even at stationary loading, which we term as secondary EMR emissions. These results are expected to provide an insight into the micro-mechanism of dislocation relaxation dynamics in metallic materials. [ABSTRACT FROM AUTHOR]

A general approach to simulate the mechanical behaviour of entangled materials submitted to large deformations is described in this paper. The main part of this approach is the automatic creation of contact elements, with appropriate constitutive laws, to take into account the interactions between fibres. The construction of these elements at each increment, is based on the determination of intermediate geometries in each region where two parts of beams are sufficiently close to be likely to enter into contact. Numerical tests simulating a 90% compression of nine randomly generated samples of entangled materials are given. They allow the identification of power laws to represent the evolutions of the compressive load and of the number of contacts. [ABSTRACT FROM AUTHOR]

The underlying atomistic mechanism of deformation is a central problem in mechanics and materials science. Whereas deformation of crystalline metals is fundamentally understood, the understanding of deformation of amorphous metals lacks behind, particularly identifying the involved temporal and spatial scales. Here, we reveal that at small scales the size-dependent deformation behavior of amorphous metals significantly deviates from homogeneous flow, exhibiting increasing deformation rate with reducing size and gradually shifted composition. This transition suggests the deformation mechanism changes from collective atomic transport by viscous flow to individual atomic transport through interface diffusion. The critical length scale of the transition is temperature dependent, exhibiting a maximum at the glass transition. While viscous flow does not discriminate among alloy constituents, diffusion does and the constituent element with higher diffusivity deforms faster. Our findings yield insights into nano-mechanics and glass physics and may suggest alternative processing methods to epitaxially grow metallic glasses. How matter deform is a central question in mechanics of materials science. Here, the authors reveal a size-dependent deformation in amorphous metals changing at ~100 nanometer sample size from collective homogeneous flow to interface diffusion realized through individual atomic transport. [ABSTRACT FROM AUTHOR]

In materials science and engineering, auxetic behavior refers to deformations of flexible structures where stretching in some direction involves lateral widening, rather than lateral shrinking. We address the problem of detecting auxetic behavior for flexible periodic bar-and-joint frameworks. Currently, the only known algorithmic solution is based on the rather heavy machinery of fixed-dimension semi-definite programming. In this paper we present a new, simpler algorithmic approach which is applicable to a natural family of three-dimensional periodic bar-and-joint frameworks with three degrees of freedom. This class includes most zeolite structures, which are important for applications in computational materials science. We show that the existence of auxetic deformations is related to properties of an associated elliptic curve. A fast algorithm for recognizing auxetic capabilities is obtained via the classical Aronhold invariants of the cubic form defining the curve. Related algorithmic alternatives are also considered. [ABSTRACT FROM AUTHOR]

Cellular automata (CA) are efficient and effective numerical tools for modeling various phenomena and processes, e.g., microstructure evolution in plastic working processes. In many cases, the analysis of phenomena can be carried out only in a limited space and on representative volume. This limitation determines the geometry of CA space hence boundary conditions are very important issues in modeling. The paper discusses different boundary conditions that can be applied to modeling. Taking into account the transformation of the modeling space, the model should allow the selection of boundary conditions. The modeling of certain phenomena and processes is directly related to changes in the geometry of a representative volume and therefore may require changes or reorganization of the modeled CA space. Four reorganization options are presented: halving, cutting and bonding, doubling, and straightening. A choice of boundary conditions may depend on particular space reorganization as used for the modeling of microstructure evolution. A set of decision rules for selecting space reorganization options taking into account the changes of CA shape and sizes is also presented. The modeling of flat and shape rolling processes utilizing some of the described techniques is shown. [ABSTRACT FROM AUTHOR]

When simulating fluids, such as water or fire, interacting with solids, it is a challenging problem to represent details of diffusion front in physical reaction. Previous approaches commonly use isotropic or anisotropic diffusion to model the transport of a quantity through a medium or long interface. We have identified unrealistic monotonous patterns with previous approaches and therefore, propose to extend these approaches by integrating the deformation of the material with the diffusion process. Specifically, stretching deformation represented by strain is incorporated in a divergence-constrained diffusion model. A novel diffusion model is introduced to increase the global rate at which the solid acquires relevant quantities, such as heat or saturation. This ensures that the equations describing fluid flow are linked to the change of solid geometry, and also satisfy the divergence-free condition. Experiments show that our method produces convincing results. [ABSTRACT FROM AUTHOR]

The article considers innovative materials for tunnel lining. This paper aims at research of the blocks of tunnel lining, reinforced with fiberglass reinforcement and polypropylene fibers. The research of strength and deformation characteristics of blocks for lining tunnels on the operational loads were carried out in the course of work. The task of the research was to test eccentric compression of two identical blocks of tunnel lining with fixing the basic parameters of deformation under load. Indices for the formation of cracks, fissures disclosure, deformability and strength of concrete non-destructive method using ultrasonic tester had been determined. [ABSTRACT FROM AUTHOR]

Of great importance in materials science is the design of effective functional materials that can be used in various technological fields. Nanomodified materials, which have fundamentally new properties and provide previously unrealized properties, have acquired particular importance. When creating heating elements and materials for deformation measurement, it is necessary to understand the patterns of heat release under conditions of mechanical deformation of the material, as this expands the potential applications of such materials. A study of elastomers modified with multi-walled carbon nanotubes (MWCNTs) has been carried at the MWCNTs concentration of 1–8 wt.%. The modes of heat release of nanomodified elastomers at a voltage of 50 V at different levels of tension are reported. The increment of the MWCNTs concentration to 7 wt.% leads to an increment in the power of heat emissions. It is worth noting the possibility of using the obtained elastomer samples with MNT as sensitive elements of strain sensors, which will allow obtaining information about physical and chemical parameters following the principles of measuring the change in electrical resistance that occurs during stretching and torsion. The changes in conductivity and heat emission under different conditions have been studied in parallel with Raman mapping and infrared thermography. The reported studies allow to make the next step to develop flexible functional materials for the field of electric heating and deformation measurement based on elastic matrices and nanoscale conductive fillers. [ABSTRACT FROM AUTHOR]

Silicon (Si) is one of the most abundant elements on Earth, and it is the most widely used semiconductor. Despite extensive study, some properties of Si, such as its behaviour under dynamic compression, remain elusive. A detailed understanding of Si deformation is crucial for various fields, ranging from planetary science to materials design. Simulations suggest that in Si the shear stress generated during shock compression is released via a high-pressure phase transition, challenging the classical picture of relaxation via defect-mediated plasticity. However, direct evidence supporting either deformation mechanism remains elusive. Here, we use sub-picosecond, highly-monochromatic x-ray diffraction to study (100)-oriented single-crystal Si under laser-driven shock compression. We provide the first unambiguous, time-resolved picture of Si deformation at ultra-high strain rates, demonstrating the predicted shear release via phase transition. Our results resolve the longstanding controversy on silicon deformation and provide direct proof of strain rate-dependent deformation mechanisms in a non-metallic system. Understanding the how silicon deforms under pressure is important for several fields, including planetary science and materials design. Laser-driven shock compression experiments now confirm that shear stress generated during compression is released via a high-pressure phase transition. [ABSTRACT FROM AUTHOR]

A continuum model of paperboard material possessing a high degree of anisotropy is established. To handle the anisotropy, three vectors are introduced which phenomenologically represent the preferred directions of the material. The in-plane director vectors deform as line segments and the out-of-plane direction deforms as a normal vector. This allows for a decoupling of the in-plane and the out-of-plane responses in shearing. The model is developed for large plastic strains and consequently an expression for the plastic spin has been proposed. The choice of plastic spin allows for a control of the direction in which permanent deformations will occur. To show the predictive capabilities of the model, the important industrial process of creasing is simulated. Both the simplified line crease setup, as well as the actual rotation crease setup used in industrial applications are studied. [ABSTRACT FROM AUTHOR]

Abstract: This article presents our take on the area of bulk ultrafine-grained materials produced by severe plastic deformation (SPD). Over the last decades, research activities in this area have grown enormously and have produced interesting results, which we summarise in this concise review. This paper is intended as an introduction to the field for the “uninitiated”, while at the same time highlighting some polemic issues that may be of interest to those specialising in bulk nanomaterials produced by SPD. A brief overview of the available SPD technologies is given, along with a summary of unusual mechanical, physical and other properties achievable by SPD processing. The challenges this research is facing—some of them generic and some specific to the nanoSPD area—are identified and discussed. [Copyright &y& Elsevier]

Abstract: This paper presents a series of experiments on high-velocity fracture of ice. Two types of experimental results are examined: standard material characterization under compression, and fracture modes observed under high-velocity impact. These fragmentation modes were observed during impact on rigid supports as well as deformable plates. The dynamic fracture phenomena were analyzed using a Cordin ultrafast imaging system. Two types of ice were tested: equiaxed and monocrystalline ice. The results give valuable information both for the understanding of high-velocity ice fracture mechanisms and for the validation of the computation tools. [Copyright &y& Elsevier]

Abstract: Due to providing reduced mechanical and thermal damages to workpiece surfaces, waterjet machining that is one of the most promising non-conventional processing methods found its niche application in cutting/shaping of materials with low machinability indexes. It can be even a more attracting technology if plain waterjet (PWJ) milling is employed due to reduced running costs (absence of abrasives) and the elimination of surface contaminations (grit embedment). The paper reports for the first time PWJ milling of a notoriously difficult-to-cut material, gamma titanium aluminide (γ-TiAl). Trials of different jet paths with varied milling parameters (e.g. water-hammer pressures, stepovers, number of passes) were conducted for understanding the removal mechanism of γ-TiAl in plain waterjet milling. The findings showed that the threshold water-hammer pressure for eroding the target material and for achieving uniform erosion were in the vicinity of 800MPa and greater than 1GPa, respectively. In addition, different fracture modes were observed on γ-TiAl when PWJ milling: (i) plastic deformation and crack initiation; (ii) stress wave propagation; (iii) micropits due to joint of crack lines; (iv) intergranular cracking/fracture, triple split and interlamellar/translamellar fracture. The stages (i)–(iii) occurred at lower water-hammer pressures and number of passes while the subsequent stage (iv) was only observed at higher water-hammer pressures or number of passes. The knowledge accumulated when studying the material removal mechanism and surface morphology enabled successful generation of 3D PWJ milled features (e.g. shallow pocket). To evaluate the capability of PWJ milling process, the geometrical accuracy and surface quality of the pocket has been examined. Finally, the advantages and drawbacks of the PWJ milling process are discussed to allow the definition where the technology is economically viable. [Copyright &y& Elsevier]

It is crucial for the carbon concentration of 9% Cr steel to be reduced to a very low level, so as to promote the formation of MX nitrides rich in vanadium as very fine and thermally stable particles to enable prolonged periods of exposure at elevated temperatures and also to eliminate Cr-rich carbides M23C6. Sub-boundary hardening, which is inversely proportional to the width of laths and blocks, is shown to be the most important strengthening mechanism for creep and is enhanced by the fine dispersion of precipitates along boundaries. The suppression of particle coarsening during creep and the maintenance of a homogeneous distribution of M23C6 carbides near prior austenite grain boundaries, which precipitate during tempering and are less fine, are effective for preventing the long-term degradation of creep strength and for improving long-term creep strength. This can be achieved by the addition of boron. The steels considered in this paper exhibit higher creep strength at 650 °C than existing high-strength steels used for thick section boiler components. [ABSTRACT FROM AUTHOR]

In 2003 Nature Materials article, Keckes et al. presented deformation properties of a variety of woods in relation to deformation of their individual wood cells. Their point is “The remarkable mechanical properties of biological materials reside in their complex hierarchical structure...”. This holds for mineral-based biological materials such as bone as well as for wood. Indeed, one of us (J.L.K.) introduced the concept that to explain the material properties of cortical bone, it was necessary to treat it as a complex material/structural hierarchical composite. Calculations to determine anisotropic properties of bone measured using ultrasonic wave propagation techniques, were extended to similar measurements on both soft and hard woods. These anisotropic properties calculations have been extended to include data based on mechanical measurements of orthotropic elastic constants of both soft and hard woods for comparison with both earlier ultrasonic measurements and mechanical testing on other woods. This work illustrates the fact that understanding and modeling the properties of wood is a complex task as the symmetry changes with scale. For example, lignin is isotropic, hemicellulose and cellulose are transversely isotropic, while the cells and microstructure have orthotropic symmetry. [ABSTRACT FROM AUTHOR]

This overview highlights very recent achievements and new trends in one of the most active and developing fields in modern materials science: the production of bulk ultrafine-grained (UFG) materials using severe plastic deformation (SPD). The article also summarizes the chronology of early work in SPD processing and presents clear and definitive descriptions of the terminology currently in use in this research area. Special attention is given to the principles of the various SPD processing techniques as well as the major structural features and unique properties of bulk UFG materials that underlie their prospects for widespread practical utilization. [ABSTRACT FROM AUTHOR]

Twinning, as a deformation mode, is a complement to slip. This paper deals with the study from a qualitative point of view, as well as from a quantitative one. Besides techniques widely used in materials science studies such as electron backscattered diffraction (EBSD) or X-ray diffraction (XRD), colour image analysis technique are presented here. Its results manage to confirm or complete the ones obtained, thanks to others methods. [Copyright &y& Elsevier]

This paper proposes a local stress concept to evaluate the fretting fatigue limit for contact edge cracks. A unique S–N curve based on the local stress could be obtained for a contact edge crack irrespective of mechanical factors such as contact pressure, relative slip, contact length, specimen size and loading type. The analytical background for the local stress concept was studied using FEM analysis. It was shown that the local stress uniquely determined the Δ K change due to crack growth as well as the stress distribution near the contact edge. The condition that determined the fretting fatigue limit was predicted by combining the Δ K change due to crack growth and the Δ Kth for a short crack. The formation of a non-propagating crack at the fatigue limit was predicted by the model and it was experimentally confirmed by a long-life fretting fatigue test. [ABSTRACT FROM AUTHOR]

Nanocrystalline metals and alloys, with average and range of grain sizes typically smaller than 100 nm, have been the subject of considerable research in recent years. Such interest has been spurred by progress in the processing of materials and by advances in computational materials science. It has also been kindled by the recognition that these materials possess some appealing mechanical properties, such as high strength, increased resistance to tribological and environmentally-assisted damage, increasing strength and/or ductility with increasing strain rate, and potential for enhanced superplastic deformation at lower temperatures and faster strain rates. From a scientific standpoint, advances in nanomechanical probes capable of measuring forces and displacements at resolutions of fractions of a picoNewton and nanometer, respectively, and developments in structural characterization have provided unprecedented opportunities to probe the mechanisms underlying mechanical response. In this paper, we present an overview of the mechanical properties of nanocrystalline metals and alloys with the objective of assessing recent advances in the experimental and computational studies of deformation, damage evolution, fracture and fatigue, and highlighting opportunities for further research. [Copyright &y& Elsevier]

The mechanisms of macroscopic ductile deformation of brittle ceramics during grinding operations are still unclear although the microcracking-free processes of grinding have been used widely in industry. This paper analyses the dislocation structure in the plastic zones of scratched alumina. It is shown that there exist three independent slip systems (two basal and one prism) and two twin systems even far below the critical onset temperatures of these systems that is usually expected. This new finding explains the formation mechanism of the macroscopic deformation induced by scratching and indicates that it is the stress field around the cutting edge which plays an important role in the activation of the slip systems. The present study offers a new insight into the mechanism understanding of material removal in ductile-regime grinding of ceramic materials. [ABSTRACT FROM AUTHOR]

In gasoline engines, CDA (cylinder deactivation) affects greatly the tribological performance of ring/liner system while reducing the emissions and improving the fuel economy. The analyses on the tribological performance of ring/liner system under the CDA mainly focus on the ideal circular cylinder liner and fixed fully flooded lubrication condition. In this study, a numerical investigation on the tribological performance of a compression ring-cylinder liner system is presented under the CDA with consideration of the cylinder liner deformation and the transition between the fully flooded and starved lubrication conditions. A mixed lubrication model coupled with oil transport model and JFO (Jacobson-Floberg-Olsson) conservative cavitation algorithm is proposed to evaluate the frictional properties. Based on the model, the tribological performance is investigated under the standard operation condition and the CDA. Meanwhile, the influence of cylinder liner deformation and oil supply on the tribological performance is also evaluated. Results show that the tribological performance of the compression ring-cylinder liner system is greatly changed when the CDA is adopted. In particular, under the CDA, the overall power loss and FMEP (friction mean effective pressure) value are increased about 27.29% and 53.51%. The study also demonstrates the necessity to consider the cylinder liner deformation and oil supply in the simulation of compression ring-cylinder liner system under the CDA. [ABSTRACT FROM AUTHOR]

Stress-driven grain boundary (GB) migration in ultrafine-grained materials with nanotwinned structure is theoretically described. In the framework of the theoretical model, the stress-driven high-angle GB migration is accompanied by migration of twin boundaries which adjoin this GB. Energetic characteristics and critical stresses of the GB migration accompanied by the twin boundary migration are calculated. [ABSTRACT FROM AUTHOR]

Suction experiments have been extensively applied for skin characterization. In these tests the deformation behavior of superficial tissue layers determines the elevation of the skin surface observed when a predefined negative (suction) pressure history is applied. The ability of such measurements to differentiate between skin conditions is limited by the variability of the elevation response observed in repeated experiments. The scatter was shown to be associated with the force exerted by the observer when holding the instrument against the skin. We have developed a novel suction device and a measurement procedure aiming at a tighter control of mechanical boundary conditions during the experiments. The new device weighs only 3.5 g and thus allows to minimize the force applied on the skin during the test. In this way, it is possible to reliably characterize the mechanical response of skin, also in case of low values of suction pressure and deformation. The influence of the contact force is analyzed through experiments on skin and synthetic materials, and rationalized based on corresponding finite element calculations. A comparative study, involving measurements on four body locations in two subjects by three observers, showed the good performance of the new procedure, specific advantages, and limitations with respect to the Cutometer®, i.e. the suction device most widely applied for skin characterization. As a byproduct of the present investigation, a correction procedure is proposed for the Cutometer measurements, which allows to partially compensate for the influence of the contact force. The characteristics of the new suction method are discussed in view of future applications for diagnostic purposes. [ABSTRACT FROM AUTHOR]

The article discusses the paradigms representing the evolution of science and technology theory and simulation-based science and empirical science. It talks about the fatigue behavior and the different aspects of material science.. It discusses the stress and strain factor, deformations and crack nucleation.

We investigate the feasibility of using a surrogate-based method to emulate the deformation and detachment behaviour of a biofilm in response to hydrodynamic shear stress. The influence of shear force, growth rate and viscoelastic parameters on the patterns of growth, structure and resulting shape of microbial biofilms was examined. We develop a statistical modelling approach to this problem, using combination of Bayesian Poisson regression and dynamic linear models for the emulation. We observe that the hydrodynamic shear force affects biofilm deformation in line with some literature. Sensitivity results also showed that the expected number of shear events, shear flow, yield coefficient for heterotrophic bacteria and extracellular polymeric substance (EPS) stiffness per unit EPS mass are the four principal mechanisms governing the bacteria detachment in this study. The sensitivity of the model parameters is temporally dynamic, emphasising the significance of conducting the sensitivity analysis across multiple time points. The surrogate models are shown to perform well, and produced ≈ 480 fold increase in computational efficiency. We conclude that a surrogate-based approach is effective, and resulting biofilm structure is determined primarily by a balance between bacteria growth, viscoelastic parameters and applied shear stress. [ABSTRACT FROM AUTHOR]

Effective lithium-ion battery module modeling has become a bottleneck for full-size electric vehicle crash safety numerical simulation. Modeling every single cell in detail would be costly. However, computational accuracy could be lost if the module is modeled by using a simple bulk material or rigid body. To solve this critical engineering problem, a general method to establish a computational homogenized model for the cylindrical battery module is proposed. A single battery cell model is developed and validated through radial compression and bending experiments. To analyze the homogenized mechanical properties of the module, a representative unit cell (RUC) is extracted with the periodic boundary condition applied on it. An elastic–plastic constitutive model is established to describe the computational homogenized model for the module. Two typical packing modes, i.e., cubic dense packing and hexagonal packing for the homogenized equivalent battery module (EBM) model, are targeted for validation compression tests, as well as the models with detailed single cell description. Further, the homogenized EBM model is confirmed to agree reasonably well with the detailed battery module (DBM) model for different packing modes with a length scale of up to 15 × 15 cells and 12% deformation where the short circuit takes place. The suggested homogenized model for battery module makes way for battery module and pack safety evaluation for full-size electric vehicle crashworthiness analysis. [ABSTRACT FROM AUTHOR]

This study investigated a methodology based on image processing and statistics to characterize and model the deformation upon controlled and uniform magnetic field and the relaxation under zero field of droplets observed in aqueous solutions of sodium alginate incorporating magnetic maghemite nanoparticles stabilized by adsorption of citrate ions. The changes of droplet geometry were statistically analyzed using a new approach based on the data obtained from optical microscopy, image processing, nonlinear regression, evolutionary optimization, analysis of variance and resampling. Image enhancement and then image segmentation (Gaussian mixture modeling) processes were applied to extract features with reliable information of droplets dimensions from optical micrographs. The droplets deformation and relaxation trends were accurately adjusted by the Kohlrausch-Williams-Watts (KWW) function and a mean relaxation time was obtained by fitting the time evolution of geometry parameters. It was found to be proportional to the initial radius of the spherical droplets and was associated to interfacial tension. [ABSTRACT FROM AUTHOR]

We recently pointed out the important role of dermis deformation by pulsating arterial pressure in the formation of a photoplethysmographic signal at green light. The aim of this study was to explore the role of this novel finding in near-infrared (NIR) light. A light-emitting diode (LED)-based imaging photoplethysmography (IPPG) system was used to detect spatial distribution of blood pulsations under frame-to-frame switching green and NIR illumination in the palms of 34 healthy individuals. We observed a significant increase of light-intensity modulation at the heartbeat frequency for both illuminating wavelengths after a palm was contacted with a glass plate. Strong positive correlation between data measured at green and NIR light was found, suggesting that the same signal was read independently from the depth of penetration. Analysis of the data shows that an essential part of remitted NIR light is modulated in time as a result of elastic deformations of dermis caused by variable blood pressure in the arteries. Our observations suggest that in contrast with the classical model, photoplethysmographic waveform originates from the modulation of the density of capillaries caused by the variable pressure applied to the skin from large blood vessels. Particularly, beat-to-beat transmural pressure in arteries compresses/decompresses the dermis and deforms its connective-tissue components, thus affecting the distance between the capillaries, which results in the modulation of absorption and scattering coefficients of both green and NIR light. These findings are important for the correct interpretation of this widely used medical technique, which may have novel applications in diagnosis and treatment monitoring of aging and skin diseases. [ABSTRACT FROM AUTHOR]