Excavation Inverse Analysis for Identifying Plastic-Material Properties
by Elasto-Plastic Finite Element Model
Yoon Seok Yang
In this paper, an inverse analysis scheme which estimates material properties and geometric shape of ground with plastic behavior from observation data under excavation is suggested. To analyze the ground with plastic behavior, consistent tangent moduli is adopted for plastic analysis. For an excavation analysis, we calculate the unbalanced stress defined as the difference between the stresses before and after excavation. The domain parameterization technique is adopted to deal with the shape variation of ground. Variational statement in the referential configuration is discretized by utilizing isoparametric mapping and linear mapping.
RQP (Recursive Quadratic Programming) is used for optimization algorithm. In optimization algorithm, the object function is defined as the least squared error between the measured data and the calculated data. The direct differentiation of the equilibrium equation with variational form is used to obtain the 1st order sensitivity of displacement. Sensitivity with regard to plasticity design variable can be obtained by direct differentiation of consistent tangent moduli, and sensitivity with regard to geometry design variable can be obtained by direct differentiation of mapping from the reference coordinate to the real coordinate. In this paper, the validity of proposed inverse analysis technique is demonstrated through three examples.
Consistent tangent moduli, Gauss-Newton approximation, direct differentiation, RQP (Recursive Quadratic Programming), domain parameterization