线性规律功能梯度材料断裂行为实验研究

焦散线方法与高速摄影技术结合，对线性规律功能梯度材料的I型静、动态断裂特性进行实验研究，并利用有限元软件进行数值模拟. 首先推导了线性规律功能梯度材料静、动态裂尖的焦散线初始曲线方程和参数方程，提出通过迭代方法根据功能梯度材料的复杂焦散线方程求解应力强度因子. 为对比材料梯度对断裂行为的影响，利用重力沉降法制备了3种梯度变化规律的试件. 然后对功能梯度材料试件进行三点弯曲实验，通过CCD和高速摄影装置采集试件焦散线图像，提取各种静、动态断裂参数. 最后通过与有限元模拟结果进行对比，证明在功能梯度材料断裂实验中焦散线方法的有效性，并详细分析了不同梯度变化规律对材料静、动态断裂性能的影响. 

EXPERIMENTAL STUDY ON FRACTURE BEHAVIOR OF LINEAR FUNCTIONALLY GRADIENT MATERIALS

Static and dynamic fracture behaviors of functionallygradient materials (FGMs) with linear variation of the shear modulus areexperimentally studied with caustics method and high speed photographytechnique, and numerically investigated through finite element method (FEM).Firstly the caustics equations relative to the caustics principles and theelastic solution at mode I crack in FGMs are deduced through an iterativenumerical method. Three kinds of specimens with different variation of shearmodulus are synthesized by a gravity-assisted vertical casting process. Thenthree-point-bending experiments are performed and the caustics patterns areshot through CCD and high speed photography equipment. The static anddynamic stress intensity factors of FGMs specimens are obtained throughcaustics method. Finally, The experimental results are validated with thenumerical results to investigate the influences of the stiffness variationon the static and dynamic fracture characteristics.