This document discusses linear and nonlinear analysis of an aircraft engine bearing bracket. It begins by describing the problem setup, geometries, boundary conditions, and material properties used. It then discusses when to use linear versus nonlinear solvers, focusing on high deformation levels, modeling time-dependent simulations, complex boundary conditions, and geometries. The document also covers the three types of nonlinearity: material, geometric, and boundary nonlinearity. It notes nonlinear systems do not follow the superposition principle. In the post-processing questions section, it lists some potential questions about the performance and deformation of different models.

1. Linear & Nonlinear Analysis of an
Aircraft Engine Bearing Bracket
June 2022
Jousef Murad

2. Problem Setup

3. Geometries

4. Boundary Conditions (BCs)

5. Material Properties
Young’s Modulus 200 GPa
Poisson’s Ratio 0.27
Density 7833 kg/m³
Yield Stress 1.0 GPa
Material

6. ● High levels of deformation?
○ Might model nonlinear material properties
● Do you need to model a simulation over a period of time?
○ The linear solver is unable to model time, so the nonlinear solver is required
○ Even if you don’t need to see the effects of time, we can use the nonlinear solver with an end time of 1
second to get results that may be impossible with the linear solver
● What are your boundary conditions?
○ A simple simulation that consists of only applied forces and fixed supports should be modeled with the
linear solver
○ A complicated simulation consists of applied velocities should be modeled with the non-linear solver
● Are you working with complicated geometry?
○ The linear solver utilizes “contacts”. Any adjacent faces will be automatically detected, and held coincident
through the simulation regardless of the boundary conditions
○ The non-linear solver utilizes “physical contacts”. We can define two faces within a physical contact and
they will not be allowed to penetrate each other, but they are not held coincident except through boundary
conditions
Nonlinear Analysis Tips

7. ● Three types of nonlinearity!
○ Material nonlinearity :
■ Allows us to define materials that go into the “plastic region”
● Material does not follow Hooke’s law
■ Stress-strain curves are required
○ Geometric nonlinearity :
■ Body undergoes large deformations → strain-displacement relations become nonlinear!
○ Boundary nonlinearity :
■ Contact problems
Nonlinear systems are not equal to the sum of its parts → Systems do not satisfy superposition principle!
What is Non-Linear Static FEA?

8. - What can you say about the performance of Model 1 although it has a great strength/mass ratio?
- How does the deformation of Model 1 look like compared to the other models?
- Which model would you choose and why? Which geometric properties do you think contribute to the overall
performance of each component?
Post-Processing Questions (Voluntary)

9. Material Properties
● Linear-Elastic
● Young’s Modulus
● Poisson’s Ratio
● Density
● Plastic
● Young’s Modulus
● Poisson’s Ratio
● Stress
● Density
Linear vs. Nonlinear

10. Material Properties
● Linear-Elastic
● Young’s Modulus
● Poisson’s Ratio
● Density
● Plastic
● Young’s Modulus
● Poisson’s Ratio
● Stress
● Density
Linear vs. Nonlinear