Article Contents
Article Contents

# Optimal control of perfect plasticity part I: Stress tracking

• * Corresponding author: Christian Meyer

This research was supported by the German Research Foundation (DFG) under grant number ME 3281/9-1 within the priority program Non-smooth and Complementarity-based Distributed Parameter Systems: Simulation and Hierarchical Optimization (SPP 1962)

• The paper is concerned with an optimal control problem governed by the rate-independent system of quasi-static perfect elasto-plasticity. The objective is to optimize the stress field by controlling the displacement at prescribed parts of the boundary. The control thus enters the system in the Dirichlet boundary conditions. Therefore, the safe load condition is automatically fulfilled so that the system admits a solution, whose stress field is unique. This gives rise to a well defined control-to-state operator, which is continuous but not Gâteaux differentiable. The control-to-state map is therefore regularized, first by means of the Yosida regularization resp. viscous approximation and then by a second smoothing in order to obtain a smooth problem. The approximation of global minimizers of the original non-smooth optimal control problem is shown and optimality conditions for the regularized problem are established. A numerical example illustrates the feasibility of the smoothing approach.

Mathematics Subject Classification: 49J20, 49K20, 65K10, 74C05, 74C10.

 Citation:

• Figure 1.  Legend; values in $\big[{ \rm{GPa}}\big]$

Figure 2.  Evolution of $|\sigma(x,t)|_F$

Figure 3.  Zoom to the left part of the beam from the left column of Figure 2

Table 1.  Comparison of the numerical results for different values of $\lambda$

 $\lambda$ iteration $\langle {g_h} , {-g_h} \rangle_{H^1_0( \mathcal{X}_c)}$ $\frac{F_\delta(\ell_h - \tau \,g_h) - F_\delta(\ell_h)}{\tau}$ err $\operatorname{dist}_ \mathcal{K}$ 0.001 100 -4.7174e-07 -4.8520e-07 0.027751 0.00048 0.01 25 -2.0089e-07 -2.0869e-07 0.037369 0.00192 0.1 33 -2.4687e-07 -2.5552e-07 0.033854 0.01781 1 58 -2.1643e-07 -2.1790e-07 0.006773 0.13652 10 100 -2.0106e-06 -2.0122e-06 0.000833 0.62584 100 62 -2.4884e-07 -2.4876e-07 0.000338 5.31148

Table 2.  Comparison of the numerical results for different numbers of time steps

 $n_t$ iteration $\langle {g_h} , {-g_h} \rangle_{H^1_0( \mathcal{X}_c)}$ $\frac{F_\delta(\ell_h - \tau \,g_h) - F_\delta(\ell_h)}{\tau}$ err $\operatorname{dist}_ \mathcal{K}$ 8 51 -2.3590e-07 -2.8903e-07 0.183828 0.0478 32 45 -2.4318e-07 -2.5225e-07 0.035941 0.1066 128 58 -2.1643e-07 -2.1790e-07 0.006773 0.1365 512 48 -2.2542e-07 -2.2541e-07 0.000045 0.1318 2048 41 -2.3150e-07 -2.3165e-07 0.000662 0.1339
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