Hyperelastic Material Card(MAT181)
Çetin BAKICI
James M. Kennedy
Dear Cetin,
*MAT_027 (*MAT_MOONEY-RIVLIN_RUBBER) does not include strain rate effects.
*MAT_181 (*MAT_SIMPLIFIED_RUBBER/FOAM) includes strain rate effects by a family of uniaxial curves at discrete strain rates.
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Please see the following presentations:
The paper below provides the implementation of *MAT_181:
Du Bois P.A., "A Simplified Approach to the Simulation of Rubber-like Materials Under Dynamic Loading", 4th European LS-DYNA Users Conference, Ulm, Germany, May, 2003.
http://www.dynalook.com/european-conf-2003/a-simplified-approach-to-the-simulation-of-rubber.pdf
Three material models were chosen for calibration, Ogden Rubber (*MAT_077_O) with linear viscoelasticity, Soft Tissue (*MAT_092) with viscoelasticity and Simplified Rubber (*MAT_181) with strain rate dependency. The results of the work revealed a good fit of the Ogden Rubber material model to low and intermediate strain rates. The Soft Tissue material model was less suited to accommodate the nonlinear strain stiffening of the adipose tissue since it is only of order two. The Simplified Rubber material model accommodated the nonlinear strain stiffening as the Ogden Rubber material model but suffered from the drawback of an instant response in the stress to a change in the loading velocity:
Engelbrektsson, K., "Evaluation of Materials Models in LS-DYNA for Impact Simulation of White Adipose Tissue", Master's Thesis, Department of Applied Mechanics, Chalmers University of Technology, Goteborg, Sweden, 2011.
http://publications.lib.chalmers.se/records/fulltext/147789.pdf
Finite element models of quasi-static material characterization processes were developed to assess hyperelastic material models available in LS-DYNA and ensure proper user input of data and parameters. Two material models were investigated: *MAT_77_O and *MAT_181:
Bondy, M., "Development of Procedures for Accurate Finite Element Modeling of the Dynamic and Quasi-Static Performance of Automotive Chassis Components Incorporating Hyperelastic Materials", Master's Thesis, Department of Mechanical, Automotive, and Materials Engineering, University of Windsor, Windsor, Ontario, Canada, January, 2013,
http://scholar.uwindsor.ca/cgi/viewcontent.cgi?article=5756&context=etd
Material tests were conducted on 60-durometer EPDM rubber, 80-durometer EPDM rubber, and the shear fender rubber. Seven LS-DYNA rubber material models (*MAT_007, *MAT_027, *MAT_031, *MAT_077_H, *MAT_077_O, *MAT_127, and *MAT_181) were evaluated using the properties obtained from the material tests. Shell and solid element modeling was investigated. Since solid elements were desired to simulate the energy absorbers, several ways to improve the physical deformation of the solid elements were explored:
Schmidt, J.D., Faller, R.K., Sicking, D.L., Reid, J.D., Lechtenberg, K.A., Bielenberg, R.W., Rosenbaugh, S.K., and Holloway, J.C., "Development of a New Energy-Absorbing Roadside/Median Barrier System with Restorable Elastomer Cartridges", MwRSF Research Report No. TRP-03-281-13, Midwest Roadside Safety Facility, University of Nebraska-Lincoln, Lincoln, Nebraska, July, 2013.
https://mwrsf.unl.edu/researchhub/files/Report278/TRP-03-281-13.pdf
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simple examples
A ball and a block are modeled out of solid elements. For material definition *MAT_MOONEY-RIVLIN_RUBBER keyword is used. The ball is given an initial velocity and it flies into the block and jumps back.
http://www.dynaexamples.com/intro-by-a.-tabiei/contact/contact-rubber/contact-rubber
This models a drum rotating with initial angular velocity. The drum is brought to rest by a rubber pad pressed against it. From this example you can learn about friction, rubber, rigid material and angular velocity.
http://www.dynaexamples.com/intro-by-a.-tabiei/contact/contact-friction-ii
Bird strike analysis using a rubber projectile with rate effects impacting a rigid plate. The rubber projectile is used to represent the "bird material" and is modeled using *MAT_SIMPLIFIED_RUBBER (MAT_181). Gelatin rebounds elastically (until tension failure). Gelatin appears to soften at higher strain rates. These effects are included in the model. Two types of force vs. change in gauge length at different strain rates are tested.
http://awg.lstc.com/tiki/tiki-index.php?page=QA+test+example+3
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Some comments regarding *MAT_181
https://polymerfem.com/community/finite-element-modeling-aa/rubber-modeling-in-ls-dyna/
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Sincerely,
James M. Kennedy
KBS2 Inc.
November 28, 2021
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