Optimizing the Two Hole Model

This example uses the principle of a relief notch and demonstrates how the optimization task should be defined.

Define a numerical variable (VARIABLE) that contains the maximum stress value of the nodes in the primary notch:
```
VARIABLE
 ID_NAME    = REF_NODE_STRESS
 DEF_TYPE   = SYSTEM
 UPDATE     = EVER
 TYPE       = SIG_MISES
 ND_GROUP   = REFERENCE_NODES
 GROUP_OPER = MAX
END_
```
The variable stress value is updated in each iteration.

Define a Design Response (DRESP) with the maximum von Mises Stress in the design area:

DRESP
 ID_NAME    = DRESP_VON_MISES
 DEF_TYPE   = SYSTEM
 TYPE       = SIG_MISES
 ND_GROUP   = design_nodes
 GROUP_OPER = Max
END_

Reference the Design Response and Variable in the Objective Function (OBJ_FUNC):
```
OBJ_FUNC
 ID_NAME = minimize_deviation
 DRESP   = DRESP_VON_MISES, ,REF_NODE_STRESS
 TARGET  = MINMAX
END_
```
The objective function of the optimization problem is to minimize the deviation of the stress values in the design area from the variable reference values. That means the maximum stress value in the design area (secondary notch) is closer to the stress level found in the reference area (primary notch) where the stress level in the primary notch is lowered.

The result looks as follows:

The stresses at the reference nodes in the design area are drastically minimized through the optimized relief notch: