Damage Dependent Constitutive Behavior and Energy Release Rate for a Cohesive Zone in a Thermoviscoelastic Solid

In this paper a cohesive zone is introduced ahead of a crack tip in order to avoid the singularity at the crack tip. By applying thermodynamics to the cohesive zone and the surrounding body, a fracture criterion will be established so that the inelastic energy dissipation both in the cohesive zone and the surrounding bulk material can be distinguished from the energy released by fracture, and the propagation of crack can be predicted. In addition, the cohesive zone constitutive equation is constructed utilizing the Helmholtz free energy in the form of a single hereditary integral for a nonlinear viscoelastic material. The resulting constitutive model for the cohesive zone contains an internal state variable which represents the damage state within the cohesive zone. When the cohesive zone opening displacement is known, the energy release rate is thus history dependent, which is expressed in terms of the damage state, the length of separation in the cohesive zone and the geometric configuration of the cohesive zone opening displacement. Example results contained herein demonstrate this effect. This revised version was published online in July 2006 with corrections to the Cover Date.     

Setup for Testing Materials with Plotting Complete Stress–Strain Diagrams

A setup for testing materials and processing the results obtained with construction of complete stress–strain diagrams is described. The setup has been created with allowance for the authors' previous experience and new ideas in testing materials of various classes under conditions of equilibrium deformation, as well as computer-based state-of-the-art technologies. The efficiency of the use of the setup developed is illustrated by the example of testing a maraging steel under equilibrium deformation involving construction of complete diagrams.     

Mechanical State Analysis of Load-Bearing Systems. Part 1. The Ultimate State

The study presents fundamentals of the ultimate state theory for the load-bearing systems operating under complex loading (mechanical fatigue, friction and wear, temperature, electrochemical corrosion). Energy criteria of the ultimate state and methods for calculating its parameters are proposed. Strength conditions taking into account both cyclic and contact loads have been set.     

一种韧性断裂损伤力学建模方法及其应用

基于连续损伤力学理论,综合考虑变形历史（温度、应变速率）对损伤的累积演化和临界损伤值的影响,提出了一种新的韧性断裂预测方法。建立了相应的韧性断裂准则,准确地预测了钛合金的热锻成形、镁合金的温热冲压成形和不锈钢板的液压成形过程中的破裂行为,表明该方法可以很好地用于存在变形历史的体积成形和板成形的成形极限预测。     

大理岩三轴压缩变形破坏与能量特征研究

利用伺服试验机对大理岩进行了常规三轴压缩试验,基于试验结果,研究了岩样三轴压缩变形破坏及其能量特征。结果表明,低围压时岩样内部材料并未均匀化,岩石表现为应变软化特性;而高围压时岩样内部材料强度由低到高逐渐屈服,变形趋于均匀,岩石出现塑性流动特性。岩石峰值应变与围压成正线性关系;岩石残余强度对围压的敏感性显著高于峰值强度。岩石破坏应变能随着围压的增大而增大,且两者成正线性关系;岩石全部断裂能随着围压的增加亦成正线性增加。     

Damage of a screw in the seal coupling

The damage to a screw on the head of a 1.8 liter personal car engine was nucleated as the result of common disadvantageous environmental influences and reversed loads leading to corrosion fatigue.     

Concept of Ultimate Fracture-Front Velocity in Cylindrical Cavity Expansion in a Brittle Material

Expansion of a cylindrical cavity in a brittle material is analyzed on the basis of the concept of the ultimate velocity of the fracture front. The boundary problems have been solved for the material regions of various states. The expansion pressure of a cylindrical cavity as a function of the expansion velocity in a ceramic material is given and compared to that of a spherical cavity.     

基于界面影响区特征的铜/铝复合板损伤行为研究

目的 基于Cohesive–GTN模型建立考虑了界面影响区的铜/铝复合板有限元损伤模型,研究铜/铝复合板塑性变形的损伤演化行为,精细化分析金属层状复合板的损伤机理。方法 采用拉伸试验机、显微硬度计、EDS能谱仪、扫描电镜等测试手段,结合试验模拟,将获取的参数输入ABAQUS有限元软件中并对模拟结果进行研究分析。结果 基于试验法确定了界面区的宽度约为3 μm,铜侧界面影响区宽度约为50 μm,铝侧界面影响区宽度约为100 μm。当塑性变形量逐步增加时,铜层材料较早发生损伤断裂,之后铝层进入集中失稳阶段,主裂纹贯穿铝层直至复合板材料整体发生断裂。此外,各异质层材料内部孔洞的体积分数不断增大,达到材料失效时的孔洞体积分数,材料发生损伤失效。结论 基于Cohesive–GTN模型建立考虑了界面影响区的铜/铝层状复合板有限元损伤模型,并结合试验验证了模型的合理性和可靠性。在考虑了界面影响区的基础上,研究了铜/铝复合板塑性变形损伤演化行为,揭示了铜/铝复合板塑性变形损伤机制,为后续金属复合板的损伤分析提供更为精细化的建模方法。     

Assessment of Limiting Damage in Materials under Static Loading with the Account of a Stress State

The model of damage accumulation in the material under multiaxial loading was used to develop the scheme of plotting the limiting damage surface of a structural material with regard to operating time and a stress state, which can be considered as material specifications useful for design calculations by damage criteria.     

芳纶纤维/环氧树脂复合材料损伤与断裂过程的声发射特性

研究了芳纶/环氧复合材料在承受拉伸载荷时的损伤与断裂行为.发现不同损伤类型表现出不同的声发射特性,从声发射信号的某几种关联图中可以较好地判断损伤发生的类型,并可根据某些声发射特征参量值对临界承载值进行合理的确定.     

爆破地质体损伤力学与断裂力学应用界限的探讨

简要地介绍了应用不同尺度观测爆破地质体中存在的缺陷和裂纹，详细叙述了爆破地质损伤力学和断裂力学应用界限。     

高应力条件下爆破振动对岩石破坏研究

文章介绍了爆破振动的检测方法及主要过程,利用爆破振动时频分析得出某质点振动参数,利用动态应力理论将爆破振动对岩石作用转化为动态应力.以大理岩为例分析高应力条件振动波动态应力对岩石的反复压缩卸载过程,并指出在高应力条件下,爆破振动对岩石的破坏作用更加明显.     

蠕变断裂局部损伤方法的有限元模型

提出了蠕变断裂局部损伤方法的有限元模型，通过有局部薄弱环到引入损伤单元，较好地不了多向应力条件下蠕变损伤发生和发展的规律，应用一有限元模型分析缺口圆棒试样的蠕变变形与损伤，得到的计算结果与试验结果能够较好的相吻合。     

确定性疲劳累积损伤理论进展

著名的Miner-Palmgren线性累积损伤理论的提出已有70余年，但由于疲劳问题的复杂性，迄今为止还没有一个模型的工程应用价值能与该理论媲美。疲劳累积损伤理论仍在发展与完善中。文章根据疲劳损伤与疲劳累积损伤理论的特点，将确定性疲劳累积损伤理论分成两大类，即线性累积损伤理论和非线性累积损伤理论，并将主要的非线性累积损伤理论分成五类：a. 基于损伤曲线法的非线性累积损伤理论；b. 基于材料物理性能退化概念的非线性累积损伤理论；c. 基于连续损伤力学概念的非线性累积损伤理论；d. 考虑载荷间相互作用效应的非线性累积损伤理论；e. 基于能量法的非线性累积损伤理论。文章分析了每一类模型中有代表性模型的物理背景，回答了模型在疲劳累积损伤理论中存在的主要问题，简要评述了模型的优缺点，讨论了确定性疲劳累积损伤理论的几个关键问题。     

掏槽爆破爆炸能量与损伤岩体破坏的能量匹配

对掏槽爆破的本质进行了探讨,指出掏槽爆破中岩石的开裂、破碎以及高温高压下的团结都是装药爆炸所释放的能量与岩石自身损伤状态匹配的结果,同时也给出了发生这些现象所必须满足的匹配条件。     

疲劳损伤对蜂窝纸板平台应力的影响

目的研究在不同疲劳损伤条件下,蜂窝纸板平台应力的变化规律和损伤机理。方法首先将蜂窝纸板进行温湿度预处理,然后对其进行5种预压缩后再进行不同次数的疲劳压缩,接着进行准静态压缩,最后得到不同疲劳损伤条件下蜂窝纸板的本构关系曲线。结果蜂窝纸板疲劳损伤因原纸纤维无规则排序刚度下降而引起,疲劳损伤对蜂窝纸板平台应力影响较大,在不同疲劳损伤条件下,疲劳损伤对蜂窝纸板平台应力的影响有一定的规律。结论蜂窝纸板在运输过程中受到疲劳损伤后,必须考虑其平台应力的变化。     

工程陶瓷磨削加工损伤的探讨

探讨了磨削过程中工程陶瓷的损伤机理及损伤过程．在讨论损伤的形成与扩展时,回顾了具有代表性的能量优先假说,对其依据的理论基础及实际意义加以分析、评论,提出了自己的观点．还提出了工程陶瓷加工的损伤预报和预测方面一些亟待研究的课题。     

气云爆炸下钢筋混凝土板毁伤的数值分析

为了研究气云爆炸下钢筋混凝土板的毁伤评估,通过ANSYS有限元数值模拟方法,研究了钢筋混凝土板的在气云爆炸下的毁伤情况。采用超压-冲量毁伤准则,以剩余承载力为毁伤指标绘制了不同毁伤程度的P-I曲线,通过数学计算拟合了P'-I'-D毁伤曲面公式,并利用数值模拟验证该公式的正确性,将数值分析和公式计算得到的毁伤程度D的比较,在不同毁伤程度下D的误差最大为14.30%。因此,该公式可用于评定钢筋混凝土板在气云爆炸下的毁伤程度。     

复合材料飞轮损伤与断裂的结构模拟

本文对复合材料飞轮的受力与损伤情况进行了分析;设计了多种模拟复合材料飞轮的断裂与损伤的静态加载结构,这些结构为用声发射方法检测复合材料飞轮的断裂与损伤的研究工作带来了很大方便,实验证明是可行性的.