| Budget Amount *help |
¥8,600,000 (Direct Cost: ¥8,600,000)
Fiscal Year 1997: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1996: ¥7,900,000 (Direct Cost: ¥7,900,000)
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| Research Abstract |
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
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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
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