热冲击作用下含缺陷磁电复合材料失效机理研究

The thermal analyses for magnetoelectroelastic composite are very important in industrial applications. As often observed, many structural components containing magnetoelectroelastic composite are subjected to thermal shock. Typical examples are reactor coolant pump structures which operate in cooling and/or heating environments. Thus, it is much important for studying and understanding the failure mechanism of magnetoelectroelast composite , which has been the front and focus area in interdisciplinary research. First,The direct method of solving the failure for magnetoelectroelastic composite under thermal impacts is developed by means of Hamiltonian dual system with the characteristic of symplectic conservation and orthrogonal after discrete time domain.Then,the theoretical model is presents with the consideratin the inertia term and the effect of the strain rate on thermal field. Afterwards, Time dependence of magnetoelectricity elastic field of several defects such as anti-plane, in-plane and dislocation are gained from the theoretical analysis.The relationship of thermal stressed and instantaneous heating rate is also discussed..The fracture of magnetoelectroelastic composite is a new young discipline,which is short of the experimental data. And applied electric and magnetic ?elds can enhance or inhibit crack growth, which cannot be explained via stress intensity factor and energy release rat. On the other hand,the nonsingular term of the elastic stress parallel to the crack plane, named as the elastic T -stress, plays a signi?cant role in determining the crack growth direction and in characterizing the near crack tip elastic-plastic stress state. To further understand crack-tip behavior of a magnetoelectroelastic material, knowledge of the in?uence of thermal loading, on the T -stress is a prerequisite. So the dependence between T-stress and thermal chock, electric field and magnetic field is investigated. Then the fracture criterion based on the nonsingular term of intensity factor is exploratively presented for the magnetoelectroelastic composite under thermal load in this program,which has been suggested as an effective fracture criterion in purely elastic material.The failure Mechanism is clarified.The research results will provide a scientific theory for the optimization design of intelligent material safety service.

本项目基于现代(强瞬变)高温环境中磁电材料安全设计关注的失效破坏性的基础性力学热点，研究含缺陷磁电复合材料热冲击断裂问题。首先，在离散时间域的基础上，充分利用对偶体系保辛、辛正交的优势，发展一种求解多场(完全)耦合时裂纹尖端场的直接方法，考虑惯性效应和应变速率对温度场的影响，构建失效问题的理论求解模型。然后，分析耦合场的动态响应，研究瞬态温度场变化规律，考察缺陷类型的影响，并探讨加热速度和热应力分布之间的关系。最后，针对磁电材料断裂问题实验数据缺乏，和应力奇异项等作为判据的不足，并考虑弹性T应力(非奇异项)可以影响裂纹扩展方向，深入地分析弹性T应力与外加热冲击及电磁场之间的关系，提出以弹性T应力热为出发点的断裂准则。此研究对阐明和理解磁电复合材料热冲击断裂失效机理有重要作用，为复杂环境中服役的材料/结构的优化设计提供理论依据。

磁电热弹材料在多场耦合情况下力学特性是尖端高技术装备分析与设计问题中存在共同的热点与前沿问题，本项目紧紧围绕解决这一个关键的科学问题，从材料学、力学、数学、热学、电磁学等学科交叉融合的角度出发，采用以理论分析为基础，基于辛方法对偶思想，首先进行力热多场耦合弹性问题的解析解的研究，给出了平面各向同性、正交各向异性和各向异性平面耦合场的解析解，并针对典型边界条件进行数值分析，拓展了力热耦合弹性解的范围，从而实现了用同一方法可求解系列问题。然后，采用分离变量法和本征展开方法通过增阶降维，推导非稳态热传导温度场问题的对偶方程组，给出了适用于任意跨厚比的非稳态热传导瞬态响应问题的解析分析与数值结果，建立起一种由本征值和本征解的直接求解瞬态热传导的方法，考虑到非零本征值本征解具有局部性特点，进一步讨论不同跨厚比、不同时间情况下温度和热流密度分布的端部效应问题。结合奇异积分方程和Gauss-Chebyshev方法研究正交各向异性基底-涂层结构中含有垂直于边界裂纹的平面断裂问题， 通过积分变换得到问题的形式解，然后利用边界条件通过积分变换与留数定理得到了一组奇异积分方程， 数值算例讨论了材料参数、裂纹物理性状、材料非均匀参数、涂层厚度的等参数对裂纹尖端的应力强度影子的影响。最后，基于弹性体本构关系、热平衡方程和导热方程，根据修正的H-R变分原理建立电磁热弹性材料在热荷载作用下的广义H-R变分原理，研究了热荷载作用下磁电材料方板的问题。本项目的研究为多耦合场理论方面的研究提供思路，为磁电复合材料与结构的设计与开发提供理论依据和技术支持。