Help with modelling problem in abaqus explicit 2

[Jlog50]

Hello,

I am trying to model two bodies in contact which impact one another at a rather slow rate. When i run the problem in abaqus explicit it seems to run for a very long time and I do not reach a solution, when I model the problem in abaqus standard it solves in about 2 hours.

Also, if the impact is very slow and I reach a converged solution with abaqus standard might this be sufficient to model the problem I am looking at i.e. in my problem I believe it is a valid assumption to ignore inertial effects.

Any input/advice would be much appreciated.

Thanks

 

[rstupplebeen]

To accurately answer your question you need to provide more details of the event. Is it a bouncy ball on a table or a hammer and nail. What is the end goal of the analysis? I hope this helps.

Rob Stupplebeen

 

[Jlog50]

Thanks for your input Rob,

The problem is a ball in socket joint (metal on metal) and the end goal of the analysis is to assess the stresses under cyclic contact, stress, residual stresses and to determine the shakedown of the component.

I hope this clears things up more

Thaks again.

 

[rstupplebeen]

A quasi-static assumption is probably appropriate. I would do it in standard.

How is the actual test done? How fast is the loading? Are the inertial effects insignificant compared to the total load?

I hope this helps.

Rob Stupplebeen

 

[Jlog50]

The test is an artificial hip joint in an experimental simulator under load and rotational displacement. The loading is described as below:

0s 0.12s 0.32s 0.5s 0.62s 1s
300.0N 3000.0N 1500.0N 3000.0N 300.0N 300.0N

In terms of inertial effects I assume these can be ignored. The frequency of the system should be significantly greater than the frequency loading. Strain rate also seems rapid enough to avoid the need to consider the response of the system.

Any further thoughts/comments on this. Thanks again so much for you valauable input.

 

[Elabbasi]

Implicit analysis (Abaqus Standard) is clearly more suitable for this rate of loading. However, that does not mean that inertial effects have to be ignored. You can do an implicit transient dynamic analysis and compare the kinetic energy to the strain energy to make sure that it is negligible.

Regarding strain rate effects, they should be insignificant for the given loading rate and metallic materials.

Nagi Elabbasi

http://www.veryst.com

 

[Jlog50]

Thank-you Elabbasi and all for your valuable input.

I would like to conduct an implicit transient dynamic analysis, however, the guidance from the abaqus manual states that for an implicit transient dynamic analysis to be valid it must have linear material behaviour (I need to consider plasticity), NO contact (which I have in my problem) and NO non-linear geometric effects (which I am considering in my problem).

Does this mean I can not conduct an implicit transient dynamic analysis in my problem?

Any further advice would be much appreciated.

 

[Jlog50]

Just to add to the comments above.. those conditions are required for a linear transient dynamic analysis.

"A problem should have the following characteristics for it to be suitable for linear transient dynamic analysis"
- linear material behaviour (I need to consider plasticity)
- NO contact (which I have in my problem)
- NO non-linear geometric effects (which I am considering in my problem).

Any further advice would be much appreciated. Thanks

 

[Elabbasi]

You're welcome Jlog50.

The restrictions that you mentioned are for transient modal dynamic analysis (Section 6.3.7 in the 6.10 User's Manual). What you need is the Implicit dynamic analysis using direct integration (Section 6.3.2). That allows all three nonlinearities that you mentioned.


Nagi Elabbasi

http://www.veryst.com

 

[fruton]

"Implicit analysis (Abaqus Standard) is clearly more suitable for this rate of loading. However, that does not mean that inertial effects have to be ignored. You can do an implicit transient dynamic analysis and compare the kinetic energy to the strain energy to make sure that it is negligible."

Elabbasi could you expand a little more on the important of the comparison and how it helps us to understand if inertial effects can be ignored? Thanks.