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对GH4169高温合金开展了不同应力三轴度(-0.33~0.33)、不同应变率(0.001~5 000 s-1)、不同温度(293~1 073 K)条件下的材料性能试验.基于Johnson-Cook失效模型的框架,研究了Johnson-Cook(JC)失效模型及已有文献提出的修改形式中应力三轴度项拟合结果的不确定性及应变率对失效应变的线性关系描述局限性问题,通过提出的特定参数确定方法与耦合应力三轴度的应变率效应指数函数,建立了一种唯象修正的失效模型.基于GH4169高温合金的试验结果,标定了修正的失效模型与JC模型中各个参数.结果表明:在不同应力三轴度下,GH4169的失效应变表现出不同的应变率效应;与传统的JC模型相比,修正的失效模型更能够较好地描述GH4169的失效行为;同时能够保证失效应变的非负性. 相似文献
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采用上限法确定了钨合金线材无模拉拔成形速度场及力能参数物理模型.分析了钨合金线材无模拉拔成形的变形模型、速度场以及力能参数的影响因素及影响规律,无模成形力能参数的影响因素主要有冷热源间距、断面减缩率、变形温度、拉伸速度、冷热源移动速度以及材料种类等,为无模拉拔成形工艺工业化应用奠定基础. 相似文献
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应用一类超弹性应变能函数,通过非线性弹性理论,研究了静脉壁在跨壁压及轴向拉伸联合作用下的变形和应力分布等力学特性,并分析了静脉壁的负压失稳问题.首先利用超弹性材料薄壁圆筒模型,得到了静脉壁在跨壁压及轴向拉伸联合作用下的变形方程,给出了正常静脉压下静脉壁的变形曲线和应力分布曲线,讨论了静脉壁的变形和应力分布规律.然后给出了负跨壁压下静脉壁的变形曲线,并由能量比较讨论了静脉壁的负压失稳问题. 相似文献
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结合位错运动的热激活理论,基于无屈服概念,提出了一组描述金属材料变形规律的弹/粘塑性本构方程.方程从总体上考虑了应变率、应变历史、应率变历史、硬化和温度等效应,具有较强的物理基础.恒温单轴条件下商业纯钛的力学性能的理论预测与实验结果相比较,存在着良好的一致性. 相似文献
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讨论有限变形和小变形假设下本构关系的区别.并将其运用于混凝土的弹。粘塑性本构关系研究,提出了一个应变率相关的动态力学模型.模型基于Ottosen的4参数屈服准则,分别考虑混凝土在硬化阶段和软化阶段加载面的不同变化规律,建立冲击荷载下的混凝土本构关系。该模型可以应用于冲击载荷下混凝土材料响应的模拟.引进Green Naghdi客观率建立有限变形的混凝土模型.根据大量实验结果对应变率和材料强度的关系提出合理假设,使模型可以反映混凝土大变形的动态力学行为,为相关工程问题的研究提供有益的思路和有效的工具。 相似文献
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The overall deformation behavior of rubber-toughened polymers (e.g. PC/ABS blends) exhibits a pronounced plastic dilatancy. As this volume increase results from diverse micromechanisms the appropriate structure of a macroscopic model is not obvious. In this contribution, different material models featuring plastic dilatancy are compared with regard to their ability to capture the deformation behavior of PC/ABS in different loading situations. All models are calibrated to match experimental data under uniaxial tension in terms of true stress-strain curves and the evolution of volume strain. Afterwards they are employed in finite element (FE) simulations of single-edge-notch-tensile (SENT) tests. Patterns of plastic deformation computed from the different material models are compared to experimental findings. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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The relationship between the tensile strength and deformation characteristics, composition, and structural organization of
films obtained by casting of two-component water-based system blends — a solution of the rigid partly crystalline polymer
polyvinyl alcohol (PVA) and an emulsion of the compliant amorphous polymer polyvinyl acetate (PVAc) — has been investigated.
The aim of this investigation was to ascertain the possibility of obtaining film materials with increased deformability based
on the biodegradable PVA. The composition dependences of the initial modulus of elasticity, the maximum stress, yield stress,
the ultimate strength, the ultimate strain, and of the unit work of fracture and other characteristics of films have been
analyzed. An analysis of the tensile true stress–strain curves of systems with volume fractions of PVA less than 0.5 points
to their considerable orientation strengthening upon tension. 相似文献
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Summary. Systems of integer linear (Diophantine) equations arise from various applications. In this paper we present an approach,
based upon the ABS methods, to solve a general system of linear Diophantine equations. This approach determines if the system
has a solution, generalizing the classical fundamental theorem of the single linear Diophantine equation. If so, a solution
is found along with an integer Abaffian (rank deficient) matrix such that the integer combinations of its rows span the integer
null space of the cofficient matrix, implying that every integer solution is obtained by the sum of a single solution and
an integer combination of the rows of the Abaffian. We show by a counterexample that, in general, it is not true that any
set of linearly independent rows of the Abaffian forms an integer basis for the null space, contrary to a statement by Egervary.
Finally we show how to compute the Hermite normal form for an integer matrix in the ABS framework.
Received July 9, 1999 / Revised version received May 8, 2000 / Published online May 4, 2001 相似文献
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V. D. Fikhman B. V. Radushkevich G. V. Vinogradov 《Mechanics of Composite Materials》1972,8(6):973-977
A apparatus designed for the extension (stretching) of yielding polymers at a constant true stress is described. The changes taking place in the general, rubber-elastic, and irreversible deformations aredetermined, together with the corresponding rates of deformation, as well as the viscosity and relaxation characteristics, during the extension (tensile strain) of block polystyrene at various constant true stresses and a temperatore of 130°C.All-Union Scientific-Research Institute of Synthetic Fiber, Kalinin. Translated from Mekhanika Polimerov, No. 6, pp. 1104–1109, November–December, 1972. 相似文献
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Z. Kwang-Hua Chu 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2009,60(3):529-542
The rate of deformation for glassy (amorphous) matter confined in microscopic domain at very low temperature regime was investigated
using a rate-state-dependent model considering the shear thinning behavior which means, once material being subjected to high
shear rates, the viscosity diminishes with increasing shear rate. The preliminary results show that there might be the enhanced
rate of deformation and (shear) yield stress due to the almost vanishing viscosity in micropores subjected to some surface
conditions: The relatively larger roughness (compared to the macroscopic domain) inside micropores and the slip. As the pore
size decreases, the surface-to-volume ratio increases and therefore, surface roughness will greatly affect the (plastic) flow
in micropores. By using the boundary perturbation method, we obtained a class of microscopic fields for the rate of deformation
and yield stress at low temperature regime with the presumed small wavy roughness distributed along the walls of an annular
micropore. 相似文献
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The rate of deformation for glassy (amorphous) matter confined in microscopic domain at very low temperature regime was investigated
using a rate-state-dependent model considering the shear thinning behavior which means, once material being subjected to high
shear rates, the viscosity diminishes with increasing shear rate. The preliminary results show that there might be the enhanced
rate of deformation and (shear) yield stress due to the almost vanishing viscosity in micropores subjected to some surface
conditions: The relatively larger roughness (compared to the macroscopic domain) inside micropores and the slip. As the pore
size decreases, the surface-to-volume ratio increases and therefore, surface roughness will greatly affect the (plastic) flow
in micropores. By using the boundary perturbation method, we obtained a class of microscopic fields for the rate of deformation
and yield stress at low temperature regime with the presumed small wavy roughness distributed along the walls of an annular
micropore. 相似文献
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In this study, an acrylonitrile-butadiene-styrene (ABS) terpolymer was reinforced with HNO3-treated short carbon fibers (SCFs). The effects of SCF concentration on the tensile properties of the composites were examined.
Increasing the SCF concentration in the ABS matrix from 10 to 30 wt.% raised its tensile strength and tensile modulus. To
obtain a strong interaction at the fiber-matrix interface, polyamide-6 (PA6) at varying concentrations was introduced into
the ABS/10 wt.% SCF composite. The incorporation and increasing the amount of PA6 in the ABS/PA6/SCF systems upgraded their
tensile properties due to the improved adhesion at the fiber-matrix interface, which was confirmed by the growing tensile
strength. These results were also supported by scanning electron micrographs of the ABS/PA6/SCF composites, which exhibited
an enhanced adhesion between the SCFs and the ABS/PA6 matrix. 相似文献
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The results of an experimental investigation of the deformation behavior of rubbery amorphous polymers (polybutadiene SKD) at low strain rates and large deformation times are described. It is shown for the first time by a viscometric method that the process of strain development in rubbery polymers has a stepwise character. A model that takes the breakdown of the structure into account is proposed for describing the stepwise nature of the strain development. 相似文献
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Z. J. Huang 《Journal of Optimization Theory and Applications》1992,75(2):331-344
In this paper, by a further investigation of the algorithm structure of the nonlinear block scaled ABS methods, we convert it into an inexact Newton method. Based on this equivalent version, we establish the semilocal convergence theorem of the nonlinear block scaled ABS methods and obtain convergence conditions that mainly depend on the behavior of the mapping at the initial point. This complements the convergence theory of the nonlinear block scaled ABS methods. 相似文献
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Conclusions A significant effect of the addition of LCP on the mechanical properties and their anisotropy has been established. Already, if one considers the shape of curves of the stress-strain relationship it can be seen that curves typical for semicrystalline polymers (pure polypropylene) with clearly visible yield point and significant cold drawing leading to an anisotropic stiffening are changing into curves without yielding and with a brittle failure (LC-rich blends). Generally, the tensile elasticity modulus increases with increasing LCP content for both MD and TD. The maximum value of anisotropy of elastic properties was noted for a rather low content of LCP (c = 5%). On the contrary, the stress at yield decreases with increasing LCP content. The same was observed for the strain at yield but in both cases an important increase of anisotropy has taken place. Consequently, the total elongation during drawing (strain at break) showed a drastic decrease for blends with higher LCP content (about 60–80 times). The addition of the LCP to polypropylene has led to a stiffness increase (higher elasticity modulus) but simultaneously to a considerable plasticity decrease. As a confirmation of these observations, there served also the creep test where a decrease of the creep compliance (by two times) for LC-rich blends as compared with pure PP was noted.It also should be emphasized that, generally, a smaller effect of LCP content on the elastic deformation was noted than that on the time dependent effects (nonelastic creep deformation).Published in Mekhanika Kompozitnykh Materialov, Vol. 30, No. 4, pp. 442–450, July–August, 1994. 相似文献