Imperf Keyword In Optistruct

jerometeoh

Hi,

I am using imperfection keyword cards to solve a structure analysis in optistruct (non-linear static=), it is a cylinder with compressive loading.

I am wondering what the scale factor does?

For example, what is the difference if I specify a factor of 0.25 instead of 1? Will it alter the shell thickness basd on that or slightly move the nodal locations?

Lastly, what is the typical factor that is being used?

 

Thanks,

Jerome Teoh

harte

Hi Jerome,

The scale factor is a multiplier on the magnitude of the imperfection. So in your hypothetical of using 0.25 versus 1.0, the magnitude of the deformation will be 1/4 of the true value.

It doesn't affect shell thickness, it only affects nodal location. The imperfection is only considered in the solver calculation, and the final H3D result file still contains the mesh of the original structure. Usually the magnitude of the imperfection is very tiny, otherwise, it is recommended to create a new model.

I'm not entirely sure what is the typical factor used, but as stated above usually the magnitude of the imperfection is very tiny.

Regards,

Greg.