# OS-E: 2040 Contact Pressure Response

This example highlights the OptiStruct capability to use nonlinear responses in optimization from version 2018 onwards.

The contact pressure and contact force can be used as response in DRESP1 card in optimization formulation. Contact pressure is output under contact traction/normal and contact force is output under contact force/normal, contact force/tangent. Response from the main surface is used in optimization formulation.

## Model Files

Refer to Access the Model Files to download the required model file(s).

The model file used in this example includes:

contpres_QA.fem

## Model Description

Model consists of two solids with thickness of 20 mm each. Node to surface contact is established between the solids. For the nonlinear static analysis run, a force of 900N distributed centrally over the top solid surface (9*100) is applied. Optimization with objective of minimizing the mass with the contact pressure set at upper bound of 0.335 as the constraint is set up.

- Young's modulus
- 210 x 10
^{3}MPa - Poisson's ratio
- 0.3
- Density
- 7.9 x 10
^{-9}ton/mm^{3}

## Results

The converged optimized model, the weight has reduced weight from 2.37635 E-3 to 2.37585 E-3 tons and the contact pressure is reduced from 0.3444 MPa to 0.3351 MPa.