Shell0

Shell Assembly

Tested with CGX 2.19 / CCX 2.19

• Investigation of shell edge to shell face connection using modal analysis
• Various contact versions
• Various element types

File	Contents
run.fbd	Simulation control script for CGX
values.fbd	Parameter values
pc-ns.inp	CCX input, node-to-surface penalty contact
pc-ss.inp	CCX input, surface-to-surface penalty contact
tie.inp	CCX input, MPC contact with *tie
equ.inp	CCX input, MPC contact with *equation
test.py	Python script for automatic parameter sweep

Results

The complete test is run using

> ./test.py

This generates a table with the frequency results for the various contact types and element types:

Results.md

MPC contact with *tie and penalty contact lead to a stiff connection between shell edge to shell face. Node-to-surface penalty contact and MPC contact with *tie show similar behaviour. The frequencies for penalty contact are usually slightly lower than with MPC contact, which is plausible, as the penalty contact has added compliance.

Surface-to-surface contact gives frequencies which differ severely from the reference MPC contact. Also, for S8R elements, there are only 5 frequencies close to zero (should be 6 rigid body modes).

Penalty contact (both surface-to-surface and node-to-surface) requires the modal analysis being performed as a perturbation step with a preceding static step (in the given case with no load applied). Note that the first result increment in a perturbation analysis is not a mode shape. For uniform test conditions, all simulations use a dummy static step and a subsequent frequency perturbation step.

MPC contact with *equation leads to a hinged connection at shell edge to face contact (7 rigid body modes).

Simulation

A single simulation is run using

> cgx -b run.fbd

Two separate parts are generated and meshed with shell elements. Specify element type and contact version using the parameters in values.fbd.

Parameter	Value	Description
etyp	qu4	Element type (qu4, qu8, qu8r)
ctyp	tie	Contact version (tie, equ, pc-ns, pc-ss)

When the simulation is done, the script displays an animation of the first mode.

Browse through the individual mode shapes using the PageDown and PageUp keys.