Correlating MAT_057_LOW_DENSITY_FOAM
ME3D
Hi everyone,
I am having trouble correlating LS-DYNA simulation results with experimental data for a low-density foam application.
My goal is to create a single *MAT_057 card that works for both 3-point bending and compression tests.
When I used the Stress-Strain curve from the compression test in *MAT_057,
the compression simulation matched the experimental force-displacement curve very well.
However, using this same material model for the 3-point bending analysis led to a huge discrepancy.
Does anyone have experience with this type of analysis, or could you recommend a proper calibration procedure?
Best regards,
ME3D
James Kennedy
Dear ME3D
From https://www.d3view.com/tensile-failure-in-low-density-foams/
Bala, S., “Tensile Failure in Low Density Foams”. December, 2010.
When modeling low-density foams, it is important to consider potential failure under tensile loading. In
LS-DYNA, the most popular constitutive material model is MAT_LOW_DENSITY_FOAM (MAT_057),
in which the default treatment of foams under tensile loading is linear with no failure. The Elastic Modulus
(Emax) in tension is computed to be the max( max(slope of the stress-strain curve in compression), E). With
this treatment, the element does not fail and its stiffness in tension is based on Emax.
One option provided by LS-DYNA is to input a limiting stress in the form of TC (Tensile cut-off stress)
which essentially models a elastic-perfectly plastic behavior in tension. Under tensile loading, when the
tensile stress reaches the value of TC, the stress is min( tensile_stress, TC) for any further loading.
In addition to TC, we can also specify FAIL = 1, to reset the tensile stress to zero for any tensile loading
beyond TC thereby eliminating the element’s capacity to offer any further resistance under further tensile
loading. It must be noted that when tensile stress reaches TC with FAIL =1, the element is NOT eroded
but simply loses resistance along tensile direction. Upon unloading, the element continues to have zero
stress until it reaches a relative volume of 1 (original volume) after which the stress is governed by the
compressive behavior.
Sincerely,
James M. Kennedy
Kbs2 Inc.
June 1, 2026
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