岩石爆破损伤模型及评述

岩石爆破损伤模型是将岩石的动态断裂作为一个连续的损伤累积过程来处理,其基本点是建立损伤变量与岩石内微裂纹密度的关系,并预测在爆炸载荷作用下岩石的损伤和破坏过程。在分析研究现有岩石爆破损伤模型的基础上,对模型中损伤变量的定义及有效体积模量进行了评述,并指出了现有岩石爆破损伤模型存在的不足及发展方向     

以损伤变量为特征的岩石损伤理论研究进展

文章从损伤变量定义的方法入手,讨论了基于宏微观理论的损伤变量定义方法及其相应的损伤模型.通过对这两类定义方法的优缺点进行讨论后指出,宏微观结合的损伤变量定义方法是以后损伤变量定义的最佳方法及岩石爆破损伤理论模型的发展趋势.     

爆炸荷载作用下围岩累积损伤效应的数值分析

巷道爆破开挖推进过程中,循环爆破开挖的多次扰动作用使保留岩体产生累积损伤,导致岩体力学参数的弱化,从而造成工程岩体的宏观失效。利用ANSYS/LS-DYNA的重启动技术,通过损伤云图和损伤变量D的变化,对圆形巷道循环进尺过程中爆破作用下的岩体累积损伤效应进行研究。计算结果表明:随着掌子面推进爆破次数的增加,围岩的损伤程度加深,但影响深度变化较小;在装药量和爆心距不变的情况下,损伤量与爆破次数之间有很好的非线性关系,即爆破损伤的累积具有非线性特性。     

岩体单孔爆破损伤的三维数值模拟研究

为了探究单孔爆破情况下岩石损伤情况，基于ANSYS/LS-DYNA软件，采用RHT材料模型，建立了多组三维数值模型，探究了三维空间下岩石单孔爆破在不同装药长度、不同地应力条件下的损伤情况，并结合自定义变量—有效损伤率来表征岩石在单孔爆破条件下损伤的时空演化规律。结果表明：从孔底到自由面，岩石的损伤逐渐增大，距离炮孔越近，岩石的损伤越严重；随着装药长度的增加，围岩对药卷的空间约束作用也在增强，岩石损伤的增长速率会逐渐减小；地应力在岩石的爆破过程中对岩石损伤具有抑制作用，且岩石损伤会向着地应力最大的方向发展。     

12Cr1MoV钢低周疲劳损伤研究

为了预测锅炉、压力容器的整体寿命,用连续介质损伤力学理论研究了工程材料的低周疲劳损伤演变过程.采用循环应力幅定义损伤变量D,根据有效应力概念,建立了低周疲劳各向同性连续损伤模型,并通过控制应变的疲劳试验,用该模型对锅炉常用材料12Cr1MoV钢试件进行了疲劳损伤的测量.研究表明,当循环进行到80%寿命时,损伤进入局部化阶段,宏观裂纹开始形成,较好地验证了损伤演变模型;所建立的模型形式简单,参数少,易测量,具有明确的物理意义,对锅炉的寿命估算有参考价值.     

纯弯曲梁的应力损伤失效分析和预测

本文提出了梁的弯曲应力损伤失效分析方法,推导了梁弯曲应力损伤基本方程,与Ｋａｃｈａｎｏｖ的材料受载横截面减少定义拉伸损伤变量类似,以梁的弯曲惯性矩减少定义弯曲损伤变量。并且弯曲损伤模型的材料常数可由Ｋａｃｈａｎｏｖ拉伸损伤模型的材料常数确定。并且对应力损伤材料提出了便于工程应用的失效预测方程。     

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。     

岩石爆破层裂机理的研究

基于连续介质损伤力学，从Ｎａｊａｒ各向同性脆性损伤的能量定义出发，从能量角度分析了爆炸应力波传播过程中岩石损伤程度的变化，确定了岩石发生层裂的判据，即当入射压缩波尚未反射部分与反射拉伸波叠加后出现的拉应力等于岩石的损伤抗拉强度（本文简称）时，岩石发生层裂。从而弥补了岩石爆破层裂理论的不足，完善了岩石爆破机理。     

岩石爆破光弹性损伤模型实验研究

通过损伤材料的光弹性分析，提出了利用损伤光弹性材料进行岩石爆破机理研究的新方法。通过实验，摸索出损伤光弹性材料制作的可行措施，得到了可用来进行光弹性试验研究的光弹性材料，并对材料的力学性能以及爆炸作用下损伤对材料中应力波的影响及其相互作用进行了研究。     

以损伤变量为特征的岩石损伤理论研究进展

从损伤变量定义的方法入手,讨论了基于不同的损伤变量定义方法及其相应的损伤模型.通过对损伤变量从纯唯象的定义方法到考虑裂纹细观的定义方法的探讨,说明了损伤模型的发展趋势.     

框架结构在冲击荷载下的损伤与非线性分析

利用集中损伤力学的方法对三维框架结构在冲击载荷作用下的损伤分析。其基本思路是:把损伤参数作为系统的内部变量,在有限元的基础上,将连续介质力学、断裂力学和塑性铰概念结合起来分析结构的力学行为。最后通过对一个二层框架结构进行数值模拟分析,并与ABAQUS的计算结果作比较,验证其可行性。     

THE INFLUENCE OF THE HARDENING STATE ON TIME DEPENDENT DAMAGE AND ITS CONSIDERATION IN A UNIFIED DAMAGE MODEL

Abstract— A model is presented for the prediction of the lifetime of metals in the high-temperature range under arbitrary variable multiaxial load. The definition of an internal variable for damage in continuum damage mechanics is adopted, which allows indirect measurement of damage via the deformation behaviour. To acquire some knowledge of damage evolution, damage is measured in two ways during uniaxial strain controlled cyclic tests: (a) a change of the modulus of elasticity and (b) a decrease of the peak stress. Surprisingly, both methods lead to results which are in good agreement. A new damage law is then developed (with reference to known models and lifetime rules) which is a modification of the creep damage law of Rabotnov that is extended by a dependence on the inelastic strain rate instead of the dependence on internal variables to take into account the hardening state. Uniaxial as well as multiaxial formulations of the new damage model (Inelastic Strain Rate Modified (ISRM) model) are presented.
The parameters of the ISRM model are determined with a view to applying them to AISI 316 L(N) austenitic steel. Some of the parameters are derived from standard creep experiments. To determine further parameters, the ISRM model is applied to uniaxial cyclic tests. Both failure behaviour and damage evolution are well described.     

Damage Constitutive Equations and its Application to Fiber Reinforced Composites under Transverse Impact

Two continuous field variables, called as continuity tensor and damage variable tensor, are used to describe the anisotropic responses of an elastic-brittle material under transverse impact load. Based on the continuum damage mechanics, anisotropic damage constitutive equations in both full and incremental forms are proposed here. The expressions of effective elastic module tensor, damage variable tensor and damage propagation force tensor are further derived, and the methods for determining the tensors are explained in detail. An example of strain and damage response of a fiber reinforced composite laminated plate under transverse impact load is employed to demonstrate the application of this theory. In the example, the damage variable coupled with geometric large deformation of laminated plate is also considered. The calculating results illustrate the influence of damage on strain field in the impacted laminated plate.     

损伤力学理论在混凝土结构中的应用技术进展

总结了最近几年国内外基于损伤力学理论的混凝土结构性能研究。详细概述了静力损伤本构关系、动力损伤本构关系、弹塑性损伤本构关系、混凝土随机损伤本构关系、徐变损伤模型、冻融作用下的损伤模型和腐蚀-化学作用下的损伤模型。总结了该研究领域存在的一些问题,并对今后的研究方向提出了建议。     

Mechanics of small damage in fiber-reinforced composite materials

In this work the new concept of small damage is examined within the framework of continuum damage mechanics. In particular, special emphasis is given to a new damage variable that is defined in terms of the elastic stiffness of the material. Only the scalar case is studied in this work. The scalar definition of the new damage variable was used recently by many researchers. The investigation of the new scalar damage variable and the new concept of small damage is carried out on fiber-reinforced composite materials.     

含损伤复合材料的湿热弹性响应

依据不可逆热力学理论, 未引入任何附加假设, 建立了湿热弹性各向异性损伤复合材料的一般理论。应用建立损伤本构方程的本构泛函展开法, 推导出湿热弹性损伤材料全部本构方程的一般形式, 其中包括比自由能密度表达式、 应力-应变关系、 熵密度方程、 损伤应变能释放率表达式、 吸湿对偶力表达式、 湿-热-固-损伤耦合的热传导方程和损伤演化方程。研究表明, 在本构方程中含有若干损伤效应函数, 表征损伤对材料宏观力学性能与湿、 热性能的影响, 其具体形式可由细观力学解确定, 从而使连续损伤力学与细观损伤力学有机结合在一起。最后, 从细观力学与实验观测两个角度, 举例说明损伤效应函数与系数张量的确定方法, 为分析变温变湿环境下复合材料的损伤问题提供重要的理论依据。      

塑性损伤的发展与应用

本文介绍了塑性损伤的机制和建立塑性损伤模型的一般方法;系统地分析比较了基于连续介质力学、细观力学、连续损伤力学等多种损伤理论,推导了它们之间的内在联系;综述了三轴度、应变路径、组织等对塑性损伤的影响,重点阐述了损伤-塑性流变的耦合分析;还介绍了电阻测量、统计与定量表征、有限元等塑性损伤的分析方法;并且分析了目前塑性损伤...     

A simple damage model for concrete considering irreversible mode‐II microcracks

A simple damage model with the concept of mode‐II microcracks on crack wall contributing to the irreversible strains for concrete is developed. By applying the micromechanics method, a microcell‐based damage model is introduced to understand the damage behaviour. Further, by introducing the physical interpretation of the damage variable using thermodynamic method, a novel damage variable (irreversible‐damage variable) is proposed to describe the irrecoverable strains generated by both mode‐II microcracks and irreversible‐frictional sliding. With this methodology, a simple continuum damage mechanics model is developed in which both elastic and irreversible damages are considered. As demonstrated by the comparison with experimental results, the proposed model is characterized by accuracy of solutions, sufficiency of physical sense and convenience of implementation.