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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 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]

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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]

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]

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]

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]

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]

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.

In the present work the numerical modeling results for the following severe plastic deformation processes: equal channel angular pressing, T-shaped pressing, cruciform pressing and 2D forging are presented. Two criteria - regularity of strain intensity distribution and rigidity coefficient of stressed state - were used for comparative analysis. Experimental research of severe plastic deformation processes was carried out. [ABSTRACT FROM AUTHOR]

A new way of generating large plastic strain in a billet by splitting it plastically by a reciprocating punch is investigated. The concept of incremental angular splitting (I-AS) is explained by referring to the severe plastic deformation process of incremental equal channel angular pressing (I-ECAP). Results of laboratory trials of I-ECAP and I-AS, using a purposely designed AA1070 billet, are presented and both processes are compared. Further comparison is based on Vickers hardness distribution in the billet subjected to I-ECAP and I-AS. FE simulation results give an indication of strain distribution in both processes. The main advantages of I-AS appear to be more flexibility in the billet choice and more uniform strain distribution in the first pass of the process. A possibility of creating a gradient material by I-AS with a flat punch is considered. [ABSTRACT FROM AUTHOR]

The review focuses on the current studies of the deformation response and accompanying structural transformations of thermoplastic semicrystalline polymers subjected to uniaxial tension prior to the yield point. The mechanisms of strain-induced cavitation of amorphous layers and damages of crystalline lamellae are analyzed in line with novel results on the deformation behavior of solid polymers at temperatures exceeding the glass transition point. The coupling of viscoelastic and plastic deformation mechanisms with the small-strain structural transformations is critically discussed on the basis of the advanced theoretical modeling of mechanical properties of semicrystalline polymers. [ABSTRACT FROM AUTHOR]

study was carried out into the possibility of employing ECAP processing in lieu of mechanical milling for the purpose of developing powder-based hydrogen storage alloys. Mg and Mg-Ti powder compacts were encapsulated in a copper block and were subjected to ECAP deformation to an apparent strain of ε = 4. This resulted in the consolidation of the compacts as well as in the refinement of their structures. The values of coherently diffracting volume size were as small as 70-80 nm, quite comparable to those achieved with mechanical milling. It is, therefore, concluded that ECAP processing can be employed successfully for the purpose of structural refinement. As for material synthesis, however, the ECAP is less efficient in expanding the interfacial area. Therefore, it is necessary to impose relatively heavy strains to able to achieve comparable expansion in the interfacial area. It appears that an advantage of ECAP deformation is the development of structures which have improved ability for milling. It is, therefore, recommended that in the processing of hydrogen storage alloys, the powder mixtures may be first processed with ECAP in open atmosphere and then by mechanical milling of a short duration carried out under protective atmosphere. [ABSTRACT FROM AUTHOR]

Early age cracking is usually the result of internal tensile stresses induced by self-desiccation shrinkage (SDS) rather than external loading. Hence, the prediction of early age cracking risk is strongly linked to autogenous shrinkage development. Both the ultimate magnitude of shrinkage and the time zero (TZ), at which shrinkage starts to develop an internal stress, could be decisive for high-performance concrete (HPC) durability. The moment TZ can be considered as the borderline between autoplastic shrinkage and effective shrinkage. Deformation rate curves might be used as a framework to identify the three main phases of hardening that occur in cement paste as hydration progresses, and the development rate of autogenous shrinkage (AS). The present study proposes starting shrinkage measurement (autogenous or total) from the moment when the rate of deformation reaches its maximum value (the first peak in the curve) and the shrinkage strain rate curve pattern changes sharply, or at the end of plastic-shrinkage. To determine the TZ with more accuracy and predict the critical moment when internal stresses may start to develop, continuous shrinkage measurement was carried out on different HPC mixtures designed with three water-to-binder ratios (w/b) of 0.26, 0.30, and 0.35, using three binder types. Results have shown that the rate of deformation development at an early age would be a reliable method to distinguish the three main phases of cement hydration reaction: liquid, semiliquid/transition, and hardened. The rate of deformation evolution may also indicate the moment when shrinkage strains evolve quickly and start to build up an internal tensile stress that could lead to cracking. The new method proposed, based on the development of the rate of deformation, has revealed itself to be highly efficient for adequate determination of TZ and could be used for all concrete types independently of specimen size. [ABSTRACT FROM AUTHOR]

Severe plastic deformation is generally achieved using novel techniques such as Equal Channel Angular Pressing (ECAP) or High Pressure Torsion (HPT), but may also be achieved by more conventional methods such as very heavy rolling. Microstructure evolution is examined in an iron aluminide intermetallic rolled to strains up to 3.3 using Transmission Electron Microscopy (TEM) and orientation determinations by Kikuchi line analysis. After the highest strains the microstructure is still characterized as a recovered submicron-scale dislocation structure, with generally low angles across the various boundaries, and a high density of dislocations inside these boundaries. The structures observed show a dependence on orientation of the underlying parent grain, with [001] orientations showing poorer rearrangement to cellular structures than grains with [113–111] orientations. [ABSTRACT FROM AUTHOR]

The tensile behaviors of the ultrafine-grained (UFG) pure copper prepared by cold rolling have been investigated. The UFG-Cu exhibited high strengths and low ductility. The ductile dimple-like fracture surfaces and persistent-slip-bands (PSBs)-like local shear bands in the tension-deformed UFG-Cu were observed, both of which typically spanned tens of grain sizes. This observation indicated that the fracture mechanisms operated at a larger scale than the grain size and eventually involved collective grain activities. Moreover, localized shear bands provided the experimental evidence to the localized plastic deformation, which was the one of the dominant reasons, causing the low ductility in the UFG-Cu. [ABSTRACT FROM AUTHOR]

A SiCw/6061Al composite was fabricated through a squeeze-casting route and hot extruded to obtain a composite with directionally aligned whiskers. Based on observed changes in whisker orientation and length before and after deformation, compressive deformation behaviour of the directionally aligned SiCw/Al composite was investigated. It is found that when the compressive temperature is much lower than the solidus of the matrix alloy, the compressive flow stress of the directionally aligned composite is increased with compressive strain first and then decreased. When the compressive temperature equals the solidus of the matrix, however, the compressive flow stress of the directionally aligned composite is increased monotonously with compression strain. During compression, whisker rotation and breakage occurred, and the higher the compressive temperature, the easier the whisker rotation and hence the smaller the degree of whisker breakage. When the compressive strain was quite high, the degree of whisker breakage was serious even at the temperature as high as the solidus of the matrix. Analyzing changes in whisker orientation and breakage before and after compression indicates that the decreased compressive flow stress with compressive strain is the result of the decreased load carrying ability of whiskers caused by whisker rotation and breakage. Compared with whisker rotation, whisker breakage has a bigger contribution to the decreased compressive flow stress. No strain softening in the composite compressed at 580°C can be thought to be a result of the very low strengthening effect of whiskers at such a high temperature. From the point of view of whisker breakage, to get higher properties of SiCw/Al composite parts made by means of plastic forming, too high plastic strain should not be suffered by SiCw/Al composites during the plastic forming. [ABSTRACT FROM AUTHOR]

The effect of stacking fault energy (SFE) on the evolution of microstructures during room temperature tensile testing has been investigated at two strain rates of 8.3×10−4 and 1.7×10−1/s in pure copper, Cu-2.2%Al, and Cu-4.5%Al alloys with SFE values of, approximately, 78, 20 and 4 mJ/m2, respectively. The mechanism of deformation changes from simple slip leading to cell formation in the high SFE metal, Cu, to overlapping and/or intersecting deformation twins in low SFE alloy, Cu-4.5%Al. The effect of strain rate is such that it results in rather poorly defined cell boundaries in copper, with a smaller cell size at higher strain rates for similar grain sizes and strain values. The alloys deform by twinning and the propensity of deformation twins increases with both a decrease in SFE value and increase in strain rates. [ABSTRACT FROM AUTHOR]