共查询到17条相似文献,搜索用时 125 毫秒
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含与不含晶界空穴的双晶体蠕变行为研究 总被引:1,自引:1,他引:0
基于晶体滑移理论,建立了各向异性镍基合金双晶体的蠕变本构模型和蠕变寿命预测模型,通过MARC用户子程序CRPLAW将上述本构模型进行了有限元实现,并对双晶体蠕变行为进行了计算分析,考虑了:(1)晶体取向的影响;(2)垂直、倾斜和平行于外载方向的三种位向晶界情况;(3)晶界处引进空间空穴的影响。结果表明,双晶体上特别是微空穴和晶界附近区域的蠕变应力应变呈现不同的变化规律,对此晶粒晶体取向和晶界位向有较大的影响;微空穴的存在削弱了双晶体的承载能力,显著地影响了双晶体蠕变持久寿命;相同条件下,垂直晶界对双晶体模型的蠕变损伤影响最为强烈,倾斜晶界次之,平行晶界最小;微空穴的生长与晶界位向和晶体取向有强烈的依赖关系,其中垂直晶界更有利于晶体滑移和微空穴生长。 相似文献
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各向异性双晶和三晶体弹塑性应力场分析 总被引:3,自引:0,他引:3
用三维弹塑性晶体滑移有限元程序对不同晶体取向的双昌和三晶体在昌界和三晶交点处的应力集中科技司和滑激活规律进行了计算分析。双晶体在计算时考虑取向的影响,计算结果表明,晶界处应力有较大的出现复杂的变化规律,这种规律与晶体取向相关;三晶交点和晶界使得三晶体应力重新分布,三晶交点可能是应力集中之地,但也可能不造成应力集中,这主要与三个晶体取向相关。本文计算表明,只有仔细地研究细观过程,才能准确理解金属材料 相似文献
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晶粒的取向和变形性质对双晶体循环变形影响的模拟研究 总被引:2,自引:0,他引:2
应用晶体细观力学方法,分析了双晶体循环变形过程中组元晶粒取向及其变形性质(Bauschinger效应和循环硬化)的影响,发现双晶体的反向屈服及循环硬化行为为主要由组元晶粒性质支配,晶间内应力的影响是次要的,晶粒取向对宏微观应力应变行为有重要的影响,取向对称性较弱或罗硬差别较大的双晶体晶界影响较大。 相似文献
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考虑晶界效应的多晶体有限变形分析 总被引:1,自引:0,他引:1
将晶界及其影响区综合考虑,建立了考虑晶界效应的力学模型,结合晶体塑性理论,利用有限变形有限元对多晶体进行数值模拟,数值结果显示了细观层次下晶粒变形场的特点,理论计算同实验定性一致。 相似文献
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比较了铜单晶体和多晶体疲劳行为的异同,提出了研究双晶体疲劳行为的必要性.总结了具有不同晶体取向和晶界的铜双晶体的疲劳行为的最新进展.利用平行晶界铜双晶体的取向因子和晶界影响区,总结了在循环载荷作用下的晶界强化模型.分析了垂直晶界铜双晶体循环塑性变形行为的特点,讨论了组元晶体取向对垂直晶界铜双晶体循环应力-应变曲线的影响.提出了提高单晶体和双晶体疲劳强度的控制因素. 相似文献
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多晶体变形、应力的不均匀性及宏观响应 总被引:9,自引:0,他引:9
从单晶滑移变形分析的角度探讨多晶体塑性变形和应力的不均匀性及宏观力学响应:建议了
一种当前构形下以应力为基本变量的单晶黏塑性增量迭代计算方法;用Voronoi晶粒集合体
模型研究多晶体由于晶粒几何及取向的随机性造成的变形和应力的不均匀性, 进行了多晶集
合体的宏观响应和晶粒位向演化数值分析. 结果表明:(1)多晶体内等效塑性应变和应力分量在统计上呈现高斯分布,在应变硬化过程中, 随着塑性变形增加多晶体微观应力的统计变异系数会越来越大;(2)用Voronoi模型计算可得到沿最大剪应力方向的滑移变形带;(3)多晶体内最高三轴拉应力一般出现在晶界特别是三晶交界处;(4)Voronoi模型能用于织构分析. 相似文献
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The rate dependent crystallographic finite element program was implemented in ABAQUS as a UMAT for the analysis of the stress distributions near grain boundary in anisotropic bicrystals and tricrystals, taking the different crystallographic orientations into consideration. The numerical results of bicrystals model with the different crystallographic orientations shows that there is a high stress gradient near the grain boundaries. The characteristics of stress structures are dependent on the crystallographic orientations of the two grains. The existing of triple junctions in the tricrystals may result in the stress concentrations, or may not, depending on the crystallographic orientations of the three grains. The conclusion shows that grain boundary with different crystallographic orientations can have different deformation, damage, and faUure behaviors. So it is only on the detail study of the stress distribution can the metal fracture be understood deeply. 相似文献
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Wang Mingzhang Lin Shi Li Chenghua Wang Zhongguang Xiao Jimei 《Acta Mechanica Solida Sinica》1997,10(4):345-351
The cyclic deformation of aluminium bicrystals was numerically simulated by using a crystalline micromechanical approach to study the effects of crystallographic orientation and deformation properties of constituent grains. Both the macro-and micro-stress-strain responses were analyzed. It was shown that the whole Bauschinger effect and cyclic hardening behavior of bicrystals is primarily controlled by the corresponding properties of the constituent grains, and that the effects of internal stresses induced by the grain boundary and the interaction between grains are secondary. The crystallographic orientation of constituent grains was also shown to have significant influence on the macro-and micro-mechanical behavior of the bicrystals. There were smaller symmetry in the orientation or greater difference in the strength between grains and more remarkable GB effects. 相似文献
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《International Journal of Solids and Structures》2007,44(10):3267-3277
In order to understand the initiation behavior of microstructurally small cracks in a stress corrosion cracking condition, it is important to know the tensile normal stress acting on the grain boundary (normal GB stress). The local stress in a polycrystalline body is enhanced by the inhomogeneity which stems from the shape and orientation of each grain. The stress in a three-dimensional polycrystalline body consisting of 100 grains with random orientation, under a remote uniform tensile stress condition, is evaluated by the finite element method. It was revealed that the local stress on the polycrystalline body is inhomogeneous under uniform applied stress and becomes large at those grain boundaries that are perpendicular to the load axis, though there is large fluctuation. It was also shown that the normal GB stress tends to be large near the triple points due to the deformation constraint caused by adjacent grains. Finally, the maximum stress on the surface of a large component caused by the inhomogeneity was evaluated by using Gumbel statistics. 相似文献
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Grain boundaries(GBs) can serve as effective sinks for radiation-induced defects, thus notably influencing the service performance of materials. However, the effect of GB structures on the zero-dimensional defects induced by irradiation has not been fully elucidated. Here, the evolution of cascade collision in the single-crystal(SC),bicrystalline(BC), and twinned crystalline(TC) copper is studied by atomic simulations during irradiation. The spatial distributions of vacancies and interstitials a... 相似文献
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Michael D. SangidHans J. Maier Huseyin Sehitoglu 《International Journal of Plasticity》2011,27(5):801-821
In this paper, we construct a model for prediction of fatigue crack initiation based on the material’s microstructure. In order to do so, the energy of a persistent slip band (PSB) is monitored and an energy balance approach is taken, in which cracks initiate and the material fails due to stress concentration from a PSB (with respect to dislocation motion). These PSBs are able to traverse low-angle grain boundaries (GB), thus belonging to clusters of grains. As a consequence of the ongoing cyclic slip process, the PSBs evolve and interact with high-angle GBs, the result of which leads to dislocation pile-ups, static extrusions in the form of ledges/steps at the GB, stress concentration, and ultimately crack initiation. Hence, this fatigue model is driven by the microstructure, i.e. grain orientations, widely distributed grain sizes, precipitates, PSB-GB interactions, as well as the affect of neighboring grains. The results predict that cracks initiate near twin boundaries from PSBs spanning a single large grain with a favorable orientation or multiple grains connected by low-angle GBs. Excellent agreement is shown between model predictions and experimental data. 相似文献
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《International Journal of Plasticity》2004,20(4-5):783-810
It is well known that the presence of continuous fibres in SiC/Ti composites leads to a high mechanical anisotropy of the composite between the longitudinal and the two transverse directions. But it is also possible that the crystallographic texture of the matrix may lead to a non-negligible anisotropy of the mechanical properties of the composite. The crystallographic orientation of the matrix grains was determined using the Electron BackScattering Diffraction technique. A local texture of the matrix of the composite is thus evidenced. Finite Element calculations are used to determine the stress field in the matrix resulting from an applied transverse loading. The representative mechanical quantities thus determined are discussed in relation with the fundamental mechanisms of plastic deformation of the matrix. Finally, the crystallographic texture of the matrix of the composite is taken into account in the numerical modellings using a three-scale model that combines crystal plasticity, a polycrystalline aggregate model and a periodic homogenization through a Finite Element unit cell for the composite analysis. 相似文献
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In this paper, a unit cell model with a film cooling hole has been set up to analyze the crystallographic stress characterization and failure behavior under temperature gradient of nickel-base single crystallographic superalloys (SC). The aim of this work is to study the failure behavior of SC blades with film cooling. The distribution of cooling air pressure on the hole side surface and the distribution of the temperature around the hole are obtained from the fluid analysis. The result of the temperature distribution is then transferred to the finite element model (cell model) by the interpolation method. The cell model is analyzed by the crystallographic rate dependent finite element method (FEM). Special attention is put on the influence of temperature gradient. The influence of the loading boundaries, i.e. displacement loading and stress loading, on the stress characterization around hole is also taken into consideration. The results show that temperature gradient hole has much influence on the stress characterization. Different types of loading boundaries result in different types of stress and strain distributions. There is clear stress concentration near the hole under displacement loading, while there is clear strain concentration under stress loading. The failure characterization has been studied by the strain energy density criterion. It is shown that the temperature gradient has influence on the failure behavior. 相似文献