沿〈111〉晶向冲击加载下铜中纳米孔洞增长的塑性机制研究

 用分子动力学方法计算模拟了沿〈111〉晶向冲击加载过程中，单晶铜中纳米孔洞（直径约1.3 nm）的演化及其周围区域发生塑性变形的过程。模拟结果表明，在沿〈111〉晶向冲击加载后，在面心立方（fcc）结构中的4族{111}晶面中有3族发生了滑移。伴随孔洞的增长，在所激活的3族{111}晶面上，观察到位错在孔洞表面附近区域成核，然后向外滑移，其中在剪切应力最大的〈112〉方向上，其位错速度超过横波声速，其它〈112〉方向的位错速度低于横波声速。模拟得到的位错阻尼系数范围与实验值基本符合。由于孔洞周围产生的滑移在空间比较对称，孔洞增长形貌接近球形。在恒定的冲击强度下，孔洞半径增长速率近似保持恒定，其速率随着冲击强度的增加而增大。     

渗碳层断裂韧性评定新方法

本文依据裂纹沿渗碳层扩张时所特有的ＰＯＰ－ｉｎ现象提出了一种评定渗碳层断裂韧性的新方法。研究表明：ＰＯＰ－ｉｎ现象是渗碳层断裂韧性正梯度分布造成的；根据ＰＯＰ－ｉｎ点处的载荷及相应的裂纹长度计算出的渗碳层ＫＩＣ－ｘ分布曲线是评定其断裂韧性的基础，而对渗碳层断裂韧性的客观评定需综合考虑断裂韧性沿渗层的分布及梯度分布     

间接骨折的应变片测量

本文设计的实验把离体猪股骨埋入明胶中,实现了更近实际的创伤模拟和实施了应变片测量技术在生物组织上的直接应用。证实了间接骨折是由应力波造成,而不是由空腔效应引起的。观察到骨的断裂表现出极强的脆性性质。     

Variational formula for a body with a crack and its applications (review)

A review is made of studies on the variational formula for a body with a crack, asymptotic expansions, weight functions, and displacements of crack faces __________ Translated from Prikladnaya Mekhanika, Vol. 43, No. 8, pp. 30–46, August 2007.     

A crack on the grain boundary — An analysis based on crystal plasticity theory

The influence of the mismatch of the lattice orientation on the deformation and stress fields of a crack located on the grain boundary is studied by means of the finite-element analysis taking account of finite deformatio and finite lattice rotation. The plane strain calculations for an fcc crystal subjected to mode I loading are performed on the basis of the crystalline plasticity described by a planar three-slip model. For the crack-tip shapes and the dominant deformation modes on slip systems, results of all the cases analysed here are in qualitative agreement with the earlier analytical and numerical solutions. Our results indicate that the lattice orientation difference may greatly influence the shear stress along the grain boundary which is related to grain-boundary sliding, while the normal stress along the grain boundary, which may induce cleavage fracture, is virtually insensitive to it. The influence of the lattice orientations on the crack-tip fields is also investigated under small-scale-yielding conditions and the comparison with the results of finite deformation is made.     

脆性材料动态断裂数值模拟

本文借鉴于Perzyna 的基本思想及Seaman 等人的实验结果,提出了一个脆性材料动态断裂模型.利用本文的模型对Cochran 的实验结果进行了数值模拟,其计算结果比Cochran 的计算结果与实验吻合得更好.     

混凝土Ⅰ-Ⅱ复合型裂纹断裂准则研究方法概述

I—II复合型断裂是混凝土断裂中最常见的一种形式．断裂力学基本上有两种分析裂缝稳定性的方法:应力强度因子法和能量法,在混凝土断裂性能的描述上两者应该是等效的．本文介绍了不同种断裂准则的基本假定、判别标准、适用范围,并与实际试验结果相比较,指出各种断裂准则的优缺点．     

????????????????????????????о?

基于射孔完井水平裂缝中支撑剂均匀充填，考虑充填层强度、油层和流体 物性以及裂缝的渗流条件，研究了地应力及渗流引起的附加应力联合作用的支撑剂充填层渗 流模型和力学模型，并进行现场应用. 研究表明，所建立的模型对压裂油井支撑剂回采出砂 状况分析具有较高的符合率，油井总体符合率、不出砂井符合率和出砂井符合率分 别为84.66\%, 84.18\%和88.10\%, 为大庆油田压裂油井防砂措施实施方案制定提 供了决策支持，有利于提高措施有效率.     

不均匀性焊接接头弹塑性断裂力学问题的有限元分析

本文对含裂纹焊接接头的简化模型——软夹硬不均匀裂纹体和硬夹软不均匀裂纹体——进行了弹塑性有限元分析,研究了材质力学性能不均匀性对OOD的影响规律.还研究了在静载和疲劳载荷下材质不均匀性对软夹硬不均匀体裂纹扩展行为的影响.     

A study of the in situ transverse tensile lamina strength and the classical solution of the opening mode crack in a 0/90/0 laminate

In this paper, the classical solution of the opening mode crack in the 90° layer of 0/90/0 laminates has been determined by means of Fourier transformations and the procedure of Copson for a pair of dual integral equations. The fracture behavior and the in situ transverse strength of the 90° layer have been quantitatively studied in graphite/epoxy laminates, based on the solution obtained above. The results show that the stress intensity factor of this kind of laminates, which is different from that of a single unidirectional 90° layer, decreases with the increase in thicknessb, or modulusE _L orG _LT of the 0° layer and also decreases with the decrease in the thickness of the 90° layer. So the lamination effect manifests itself and thein situ transverse strength of the 90° layer is thereby enchanced. The theoretical calculations agree with the experimental data presented by D.L. Flaggs. Supported by National Natural Science Fundation of China.