Introduction

*SECTION_SOLID
 Breaking Post Exhibits Hourglassing
 LS-DYNA Manual Section: *SECTION_SOLID

Additional Sections:
*CONTACT_ERODING_SINGLE_SURFACE
 *INITIAL_VELOCITY_GENERATION

Example: Breaking Post Exhibits Hourglassing

Filename: section_solid.hourglassing.k

Description:
A rigid beam strikes a post near the top of the post. There is hole cut out
of the lower portion of the post to reduce its' section modulus and thus,
allow it to snap-off easier. In the first model, the post begins to break,
but hourglassing starts to dominate the solution and the post does not
completely snap.

In the second model, a fully integrated solid formulation is used for the post,
causing the post to snap-off as desired.

Model:
The beam is constructed with rigid shell elements. An initial velocity is given
to the beam using the *INITIAL_VELOCITY_GENERATION keyword. The post is
constructed with solid elements using a piecewise linear plasticity material
model with failure. Single point constraints (SPC's) are placed on the bottom
of the post. Eroding single surface contact is required in order for the
contact to behave properly while the post snaps in two
(*CONTACT_ERODING_SINGLE_SURFACE).

Results:
The first model results are significantly different than the second model
due to hourglassing.