Papers by Keyword: Strain-Hardening

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Authors: Zhi Gang Jiang, Dian Yi Song, Fei Liu
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.
Authors: Heng Mao Niu, Yong Ming Xing, Yan Ru Zhao
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.
Authors: Jürgen Hirsch, Kai F. Karhausen, L. Löchte
Authors: Aaron Alejandro Aguilar Espinosa, Neil Fellows, Oscar Portillo
Abstract: The numerical simulation of crack closure is employed to assist on the prediction of crack growth rate. Under fatigue load, the stress-strain response of metals is altered due to cyclic loading. For this reason, the material properties characterization is of prime concern as an input parameter to obtain reliable results. From numerical simulations, it was observed that simple material models do not provide accurate data for long crack lengths. In this paper, the effect that different hardening models have on the opening response of a cracked component when it is subject to variable amplitude loading is analyzed. The interaction effects (crack arrest/acceleration) for long crack length simulation are specially highlighted. For this purpose, a 6082-T6 aluminium alloy was analyzed experimentally and numerically in order to measure crack closure, and then, those data were used to predict fatigue crack growth rate under different patterns of overload. The Paris equation and the Elber crack closure concept were employed. The results showed that small variations in the opening stresses obtained from different material models produce high overestimated simulations of crack growth rate. Also, it was proved that the crack closure mechanism is able to take into account interaction effects due to variable amplitude loading.
Authors: J. Bonneville, P. Spätig, Jean-Luc Martin
Authors: Ling Xue Kong, Peter D. Hodgson
Authors: Sheng Li Jin, Harald Harmuth, Dietmar Gruber
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.
Authors: Kaneaki Tsuzaki, Andrey Belyakov, Yuuji Kimura
Abstract: Deformation microstructures were studied in a two-phase (about 60% ferrite and 40% austenite) Fe – 27%Cr – 9%Ni stainless steel. Severe plastic working was carried out by rolling from 21.3×21.3 mm2 to 7.8×7.8 mm2 square bar followed by swaging from Ø7.0 to 0.6 mm rod at an ambient temperature, providing a total strain of 6.9. After a rapid increase in the hardness at an early deformation, the rate of the strain hardening gradually decreased to almost zero at large strains above 4. In other words, the hardness approached a saturation level, leading to an apparent steadystate deformation behaviour during cold working. The severe deformation resulted in the evolution of highly elongated (sub)grains aligned along the rolling/swaging axis with the final transverse (sub)grain size of about 0.1 μm and the fraction of high-angle (sub)boundaries above 60%. However, the kinetics of microstructure evolution in the two phases was different. In the ferrite phase, the transverse size of deformation (sub)grains gradually decreased during the processing and approached 0.1 μm at strains of about 6.0, while the transverse size of the austenite (sub)grains rapidly reduced to its final value of 0.1 μm after a relatively low strain about 1.0.
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