【作者】 张强；

【导师】 王熙；

【作者基本信息】 上海交通大学 ， 力学， 2015， 硕士

【摘要】 非均质材料以其独特的材料性质随位置变化的分布特性,在各种极端环境及多场载荷作用的工程结构中得到广泛应用。本文以非局部弹性理论为基础,研究力、热、电、磁多场载荷下考虑小尺度效应的非均质材料内部的微观损伤愈合规律。在建立材料性质沿径向指数分布的非均质体内孔洞动态收缩的力学模型后,利用非局部弹性理论得到非均质体内孔洞边缘扩散层中的应变能,并结合晶格扩散和化学位梯度变化规律求出非均质晶体内孔洞收缩速率和自愈时间的解析表达式。结果表明小尺度效应可以通过增加晶体内孔洞的收缩速率和减小内孔洞愈合到稳定的尺寸来有效的促进非均质晶体内孔洞自愈;当材料特性沿径向的分布指数为1时将获得最佳的内孔洞收缩结果;适当改变环境温度变化和施加特定的电、磁场也能促进内孔洞自愈收缩;非均质压电体周围的外加电势会对其内孔洞的收缩速率起到较大的影响。更多还原

【Abstract】 Heterogeneous material with its unique material character distribution, has been widely used in a variety of extreme environments and multi-field. On the basis of the nonlocal elastic theory, this paper explored small scale effect on the microscopic damage healing performance within heterogeneous materials under the multi-load of force, electric, temperature and magnetic. After established a simplified three-dimensional mechanical model to meet the material parameter radial distribution and the dynamic construction of a heterogeneous grain, the author figured out the strain energy in the edge of void diffusion layer inside heterogeneous grain according to nonlocal elastic theory. Then combined lattice diffusion and chemical potential gradient, the analytical expressions of void shrinkage rate and healing time were obtained. The results show that the small-scale effect could promote the self-healing of a void within heterogeneous grain through increasing the shrinkage rate and reducing the stable size of holes; when the exponent of material properties radial distribution is 1, the process of shrinkage would get the best; changing the ambient temperature appropriately and applying the specific electromagnetic field can also accelerate the healing process; the electronic potential would somehow hinder the void healing in piezoelectric crystal.更多还原