# RD-E: 5101 Size Optimization of a B-Pillar

This example defines a crash test on B-Pillar. The optimization objective is to minimize the mass of the B-Pillar by changing the shell thickness. The intrusion, which is defined by the optimization constraint is required to not be larger than the original model, to keep the passenger safe.

The setup of optimization in Radioss requires an extra input file apart from the usual Starter and Engine input files. The required file is an optimization input file named <name>.radopt (the Starter and Engine files are named <name>_0000.rad and <name>_0001.rad, respectively). The <name>.radopt file defines optimization entities such as the optimization objective, optimization constraints, design variables, optimization responses and so on.

## Options and Keywords Used

- Optimization objective (/DESOBJ)
- Optimization design variable (/DESVAR)
- Relate design variables to analysis model properties (/DVPREL1)
- Optimization design response (/DRESP1)
- Optimization design constraint (/DCONSTR)
- Material law (/MAT/LAW36 (PLAS_TAB))
- Shell property (/PROP/TYPE1 (SHELL))
- Initial velocity (/INIVEL)
- Interface (/INTER/TYPE7)
- Rigid body (/RBODY)

## Input Files

- B-Pillar (Thickness Optimization)
- <install_directory>/hwsolvers/demos/radioss/example/51_RADIOSS_Optimization/Size_Optimization

## Model Description

Units: mm, s, ton, N, and MPa

- Objective: Minimize mass
- Constraint: Maximum displacement of node 2021524 in Y direction (inside reinforcement) < 19.7 [mm]
- Design variables:
- Shell thickness of the middle reinforcement - allowable range [0.5mm, 3.0mm]
- Shell thickness of the inside reinforcement - allowable range [0.5mm, 3.0mm]

### Detailed Optimization Setup

### Optimization Objective

/DESOBJ is used to define optimization objective. In this example, it defines the minimal response #1.

### Optimization Constraint

In this example, you want to constrain the intrusion to not be larger than the original model
(before optimization). In the original model, max. y-displacement in node 2021524 is
19.7mm. Define this value as `cmax` in /DCONSTR
and in response 2, define 19.7 as the max. y-displacement (with
`RTYPE`=5,
`ATTA`=7) in node 2021524 (with
`PTYPE`=1,
`ATTI`=2021524).

`cmax`may differ.

### Design Variable

/DESVAR is used to define design variables and /DVPREL1 to relate design variables to analysis model property.

Two different design variables are defined: One for part 2000327 and one for part 2000329

- In /DESVAR with the range [0.5,3.0] - this will be used
in /DVPREL1.
In /DVPREL1 with

`prop_typ`and`prop_fid`the above variable can be used for shell thickness, and with`prop_ID`the thickness in shell property 2000327 will be used in the optimization run. `COEF`_{1}in /DVPREL1. In each iteration,`P`_{i}(the thickness value) will be equal to $$C0+\left(1.0\ast X\right)$$, where $$X\in \left[0.5,3.0\right]$$ which is defined in /DESVAR.(1)

### Radioss Options Used

/INIVEL and /INTER/TYPE7 are also used.

Use /INIVEL to optimize the B-Pillar under same initial kinetic energy.

## Results

- The latest design provides the best results. Verify whether the result is
feasible or not. In the *.out file
(Neon-b_pillar.out) this data is at end of each
iteration.
`FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED)`- indicates that the design is good.`INFEASIBLE DESIGN (AT LEAST ONE CONSTRAINT VIOLATED).`- indicates that the design variable definition needs to be checked/improved.This information can also be found in the output file hwsolver.mesg.

- In the *.out file
(Neon-b_pillar.out), check/verify the optimization
definition.
`Objective Function: Minimize Combined Mass`,`Run Type: Sizing Optimization`and so on. - By running the Optimization in Radioss, an equivalent OptiStruct model will also be automatically created and named *.fem (Neon-b_pillar.fem).

In the original model, the mass of the two parts is 3.0011e-3[Ton] and the optimized mass for these two parts is 2.4158e-3[Ton]. The mass is reduced by approximately 19.5%.

The thickness of part #2000327 is 1.328mm and the optimized thickness is 0.5539mm. The thickness is reduced.

`ATTB`=1 (for COMB) is defined).

In the last iteration, the mass was reduced to 2.4158e-3[Ton]. This new design still meets the constraint (< 19.7[mm]), defined in /DCONSTR.

In node 2021524, the max. y-displacement: