Static Non-Linear Analysis (Geometric and Material Non-Linearity) 7

[generaluday]

I'm trying to setup a simple static non-linear analysis of a polycarbonate (PC) lamp housing, which has a tab that's inserted into a slot, and the tab undergoes a deformation of about 6mm to snap into the slot. I want to investigate the non-linear behavior of the tab "hinge" area as it undergoes plastic deformation.

These are the steps that I'm going through the set the analysis up.

1. Define the PC material, and in the Nonlinear tab, define the Nonlinearity Type as Plastic, the Yield Criterion as Von Mises, and enter the Initial Yield Stress value. Also, in the Nonlinear Properties, I define the Hardening Rule as Isotropic, and include the Stress-Strain curve (Strain vs. Stress in Femap) of the PC material under the Functional Dependence.

2. Create element type, create mesh, apply constraints, boundary conditions, loads, and define the non-linear analysis under Model > Load > Nonlinear Analysis and use the default setup with 10 Increments.

3. Run a Static Nonlinear analysis on this setup.

I'm getting a fatal error (well, 4 fatal errors) when I try to solve this. Is there something I'm missing in my setup? I've uploaded the Femap file.

I'd appreciate some help! Thanks.

 

[FEMAP2]

The main problem here is your stress vs. strain curve, Nastran does not allow the discontinuities/duplicate entries, your model has - delete the ones indicated. I also deleted function 1 since it's not used at all

X Y
0. 0.
10. 0.013
20. 0.023
30. 0.032
40. 0.04
50. 0.05
52. 0.3
53. 0.18 <---
53. 0.4
60. 0.06 <---
60. 0.5
64. 0.08 <---
68. 0.6
74. 0.7
82. 0.8

The model then runs.

 

[generaluday]

Thanks a lot, FEMAP2. I experimented with different stress-strain curves, and figured that out. I wonder why Nastran does not allow the discontinuities/duplicate entries, which most stress-strain curves contain. It's strange. I appreciate your response though!

 

[rb1957]

good catch FEMAP2 ... i thought it deserved an LPS !