Papers by Keyword: Strain-Hardening

Abstract: Relationships between macroscopic and microscopic constitutive parameters associated with steady state DDRX are derived for a material in which strain-hardening and dynamic recovery are described by the Yoshie-Laasraoui-Jonas equation. First examples are given for illustration.

Abstract: The strain-hardening performance and characteristics of pipeline steel material have an important influence on the deformation behavior and arrest behavior of the line pipe. In this paper X70, selected, and the longitudinal and transverse tensile stress-strain curve and strain-hardening characteristics were analyzed. The results showed that the strain hardening exponent of the double-phased line pipes derived from the transvers stress-strain curve maintains relatively low level at early stage and increased gradually with variation of strain, which was different from the strain hardening behavior for the rest line pipes in this study. Phase ratio, grain size and dislocation density, precipitation, texture, etc. have an effect to the strain hardening behavior of pipeline steel.

Abstract: Ladle treatment of molten Hadfield steel considers as the new effective technique for producing Hadfield steel instead of conventional heat treatment process. New eutectic is formed as a result of the ladle treatment process. In this research, the strain-hardening property of the four grades of Hadfield steel containing granular new eutectic phase has been investigated, and compared with the conventional Hadfield steel. Optical and scanning electron microscope reveal that slip bands fractions vary through the five grades of steel as a result of deformation. XRD observation refers to the austenite phase is still the dominant phase through the whole five grades of steel after deformation. The results of the compression and hardness tests clarify that the new granular eutectic phase has a significant effect on the strain-hardening behavior, austenite stability. The nodularity of new eutectic phase is a considerable parameter in the function of yield strength, and hardness increment as well.

Abstract: During the operation of industrial vessels at high temperatures both elastic and inelastic behaviour of refractories may occur under intense thermomechanical loads. The latter one brings about an irreversible strain, which may cause mechanical failure of refractories and be responsible for the opening of joints. Besides material failure under tensile or shear loads, creep of refractories also may contribute to the occurrence of the irreversible strains. For quantitative assessment of the thermomechanical behaviour of an industrial vessel lining by the simulations, the accurate determination and description of creep behaviour of refractories at service related load levels is of importance. In this paper, a newly developed high temperature compressive creep testing equipment is introduced. Compared with conventional creep testing machines it enables the application of higher load levels as they occur under service conditions. A general testing procedure and displacement/time curves for various temperatures and loads are shown. For simulation purposes a Norton Bailey type creep law representing strain hardening is identified from the test results. An inverse evaluation procedure is performed for this purpose which exhibits high efficiency and robustness.

Abstract: We have investigated the strain-hardening mechanisms across the relevant scales in a Fe-22Mn-0.6C (wt.%) twinning induced plasticity steel by multi-scale microstructure characterization. The approach makes use of electron microscopy techniques such as electron channeling contrast imaging (ECCI) to characterize microstructure features at the micro/nanoscale, and atomic-scale investigations of partitioning behavior across interfaces and solid solution/clustering effects by atom probe tomography (APT). The contribution of most relevant microstructure features to strain hardening is analyzed.

Abstract: Engineered cementitious composites (ECC) are characterized by strain hardening and tight crack width control. Good fiber distribution can maximize fiber contribution. Processing can substantially influence fiber distribution, and consequently influence mechanical performance. Combined with the latest research results, this review summarizes the results of several studies in which the influence of processing on fiber distribution and mechanical performance was investigated. Based on the reviewed methods it is argued that the processing technique of producing ECC can improve fiber distribution.

Abstract: Engineered cementitious composites(ECC) are characterized by strain hardening and tight crack width control. Good fiber distribution can maximize fiber contribution at each stage of the crack bridging process. However, poor fiber distribution can be disadvantage to fiber contribution, even influence the robustness of strain-hardening. Combined with the latest research results, this review highlights the methods of improving fiber distribution in ECC. Good fiber distribution is based on excellent matrix fluidity, which can be determined by mineral admixtures, admixture and water/binder (w/c). Fiber included surface morphology, size and content of fiber have also an effect on fiber distribution in the ECC. Additionally, slag and sand size shape of matrix components play a surprising role on fiber distribution. Based on the reviewed methods it is argued that fiber optimization and matrix components tailoring can be used to improve fiber distribution.

Abstract: A finite cylindrical cavity expansion model for metal targets was proposed in consideration of the lateral free boundary and strain-hardening effect. Analytical solutions of radial pressure on the cavity wall were obtained. An engineering model for the penetration of rigid sharp-nosed projectiles into thick cylindrical metal targets with finite radius was developed. The influence of the radius ratio of target to projectile on penetration depth was studied. The present engineering model has good agreement with ballistic experiments and numerical simulation. The influence of the lateral free boundary of target on penetration depth needs to be considered for radius ratio of target to projectile less than 20.

Abstract: Seamless stainless microtube (SUS 304L) was selected for a detailed investigation of the strain-hardening influencing grain refinement and microstructural evolution during processing by varying press bending angles. The problem was approached in three stages. First, the microtubes were annealed to examine the initial grain size and analyzed the effect of grain size on mechanical properties by performing a tensile test. Second, a microtube press bending system was developed to observe springback behavior. Third, the microstructure of the microtube with different press bending angle was observed to investigate the effect of strain-hardening induced grain refinement on springback behavior. As a result, the occurrence of grain refinement reduced the springback amount. The mechanism of microstructure development in the shear zone during the press bending process is needle like, twin band and equiaxed and small rounded grains sequentially.

Abstract: Strain-hardening cement-based composites (SHCC) resist increased tensile stress after first crack formation, over a significant range of tensile strain. This increased strength and strain capacity is achieved by effective crack bridging by fibres, across multiple cracks of widths in the micro-range. Whether the crack width limitation translates into increased durability through retardation of ingress of moisture, gas and other deleterious matter, is scrutinised in this paper. The potential of the comparatively new composite material becomes obvious, yet it is clearly outlined that further research is necessary before we fully understand the basic mechanisms underlying durability of SHCC.