Identification of Gurson's Material Constants by Using Finite Deformation/Elastic Plastic Finite Element Method and Kalman Filter

提出了一种基于逆分析的非线性本构方程材料参数估计方法。利用实验试样的可测响应，进行逆分析，预测未知材料常数的最适宜值。一般来说，预测的准确性取决于拉伸加载试验中试样的类型。为了确定最佳的标本配置，我们在这种方法中采用了卡尔曼滤波技术。我们选择多孔弹塑性材料的Gurson模型作为材料模型，其两个参数作为未知常数。Gurson本构模型已被广泛应用于研究各种金属的韧性断裂和剪切局部化。详细的有限元模拟证明了该方法在确定Gurson模型中与空洞成核有关的两个参数方面的有效性。在卡尔曼滤波过程中，我们发现收敛到正确解的速度取决于试样的形状、未知参数的初始估计值以及测量数据和计算参考数据的准确性。分析预测，当使用两个不同形状的试样受拉时（即一个带中心孔的矩形板和另一个带双侧缺口的板），收敛速度会有很大的改善。提出了一种识别弹粘塑性材料本构方程参数的简便方法。在该方法中，测量了劈裂霍普金森杆试验中输入和输出应力的时程，并利用测量的输入应力时程进行了有限元计算。通过将计算结果与实测的输出应力时程进行比较，利用卡尔曼滤波进行识别。为了证明该方法的有效性，用铜试件进行了霍普金森杆劈裂试验，并确定了表征粘塑性的两个参数。为了将该方法应用于冲击问题的研究，本文对该领域的逆分析研究进行了综述。结果表明，该方法存在多种问题。少

A new approach based on the inverse analysis is proposed for estimating material parameters of nonlinear constitutive equations. Using the measurable response of experimental specimens, the inverse analysis is carried out to predict most suitable values of unknown material constants. In general, the accuracy of prediction depends on types of specimens in tensile loading tests. In order to identify optimal specimen configurations, we have employed the Kalman filter technique in this approach. We have chosen the Gurson's model for porous elastic-plastic materials as the material model and its two parameters as the unknown constants. The Gurson's constitutive model has been widely used for studying ductile fracture as well as shear localization of various metals. Detailed finite element simulations are performed to demonstrate the effectiveness of the proposed method in determination of the two parameters relating to void nucleation in the Gurson's model. In the Kalman filter procedure, i … More t is found that the rate of convergence to the correct solutions depends on the shape of test specimen, initial estimates of the unknown parameters, and the accuracy of measured data as well as computed reference data. The analysis predicts that when two differently shaped specimens under tension are used (i.e., a rectangular plate with a center hole and the other plate with double side notches), a drastic improvement occurs in the rate of convergence.A new simple method for identifying the parameters in the constit utive equation for an elastic/visco-plastic meterial is proposed. In the propose d method, the time-histories of the input and output stresses in the split Hopkinson's bar test are measured, and a finite element calculation is performed using the measured time-history of the input stress. The identification employing the Kalman filter is carried out by comparing the calculated results with the meas ured time-history of the output stress. To demonstrate the usefulness of the proposed method, a split Hopkinson's bar test is performed using copper specimens, and two parameters characterizing the visco-plasticity are identified.In order to apply this method to impact problems, the researches on the inverse analysis in this field are reviewed. It is found that there exists a variety of problems which are suitable for this method. Less