Theory-Lesson 12(lightweight)

Question 1

What is the synergy of components regarding the LW design?

Answer 1

Synergy is a key component in the car design and specifically in the lightweight design.
The difficulty in that is that there are a lot of conflicting OFs and a lot of constraints.

For example, if we achieve 10% mass reduction is some way but the noise isolation is not acceptable, then the whole solution should be discarded.

Also, we should always take into account the crash requirements.

Question 2

Which are the categories of structural optimization?

Answer 2

1)Sizing optimization (beams size)
2)Shape optimization (position of control points)
3)Topology optimization (density of each cell)

Question 3

What is the main goal of topology optimization?

Answer 3

The main goal of topology optimization is to maximize the stiffness (minimize compliance) while reducing the mass of a structure.

Question 4

What was the first idea behind topology optimization?

Answer 4

Minimize the deformation energy by changing the density.

But since there are no constraints on this method,it is very problematic, mainly because it creates discontinuities.

Question 5

FE with topology optimization

Answer 5

The next idea was to discretize the structure in finite elements. The objective was to minimize the internal deformation energy but again this method had problems, mainly related with: checkerboards/mesh dependence/local minima

Question 6

SIMP method

Answer 6

the solid isotropic method with penalization introduces a penalty factor p which aims to diminish the contribution of elements with intermediate density to the stiffness matrix.

Again the objective is to maximize stiffness, which also means to minimize compliance.
The idea of this method is to allow intermediate densities of the elements (0 to 1 continuous). For each element the allowable density varies from ρmin to 1 (ρmin is introduced so as not to have problems with calculations).

Since ρ varies, E varies too.

Question 7

What is the role of sensitivity analysis on the SIMP method?

Answer 7

During each iteration, the optimization algorithm performs a sensitivity analysis to evaluate the impact of the variation of material densities has on the OFs to maximize stiffness.

Elements weighted with low material density factors eventually lose their structural importance and are eliminated during the process.

Question 8

What is the mesh-dependent filtering on the SIMP method?

Answer 8

This process aims to stop the phenomenon where discontinuities exist. It introduces an influence area for each element and averages the sensitivity of each element inside its influence region