VM-LSDYNA-WB-008

VM-LSDYNA-WB-008
Plastic Compression of a Pipe Assembly

Overview

Reference: Crandall, S. H & Dahl, N.C. (1959). An Introduction to the Mechanics of Solids. McGraw-Hill. 180 (ex. 5.1)
Analysis Type(s): Explicit Dynamics with Workbench LS-DYNA
Element Type(s): Axisymmetric
Input Files:Link to Input Files Download Page

Test Case

There are two coaxial tubes. The inner one is made of 1020 CR steel and has a cross-sectional area As. The outer tube is made of 2024-T4 aluminum alloy and has a cross-sectional area Aa. They are compressed between heavy, flat end plates, as shown in the problem sketch. Determine the load-deflection curve of the assembly as it is compressed into the plastic region by an axial displacement.

This test case is also solved using Ansys Mechanical. See VM-WB-MECH-047.

Figure 13: Problem Sketch

Problem Sketch

Material PropertiesGeometric PropertiesLoading

VMSIM047_CR_steel:

Es = 26,875,000 psi
σ(yp)s = 86,000 psi

VMSIM047_T4_aluminum alloy:

Ea = 11,000,000 psi
σ(yp)a = 55,000 psi
ν = 0.3
ℓ = 10 in

Steel:

Inside radius =
1.9781692 in
Wall thickness = 0.5 in

Aluminum:

Inside radius =
3.5697185 in
Wall thickness = 0.5 in

1st Load step:

δ = -0.032 in

2nd Load step:

δ = -0.05 in
3rd Load step:
δ = -0.10 in

Analysis Assumptions and Modeling Notes

Assume that the end plates are so stiff that both tubes are shortened by exactly the same amount. Because the geometry and loading are symmetric about the y-axis, the above problem can be analyzed as an axisymmetric problem.

Results Comparison

 TargetWorkbench LS-DYNAError (%)
Load, lb for Deflection @ 0.032 in10244001021485 –0.285
Load, lb for Deflection @ 0.05 in12620001255440 –0.520
Load, lb for Deflection @ 0.1 in12620001253700 –0.658