NO E Young Modulus, no Plasic part just elastic arc and the crush. Wich model to you in LS-DYNA.
leszpol
NO Young Modulus E (there is no line part at the begeninig ) , no Plasic part just nonlinear elastic arc and then crush. Wich model to use in LS-Dyna. There is no strig line part at the begining. I am afraid there is no adecuate model ?
James Kennedy
Dear Leszek,
Some notes of possible interest.
LS-DYNA handles nonlinear elastic material behavior through a variety of specific material models, primarily categorized as hyperelastic for large strains and certain specific models for small-strain nonlinearity.
Key Material Models for Nonlinear Elasticity
The choice of material model (defined by the *MAT keyword in the input deck) is crucial and depends on the specific material and the nature of the deformation.
· Hyperelastic Materials (MAT_HYPERELASTIC): These models are the most common approach for materials that exhibit large, recoverable deformations and a nonlinear stress-strain relationship, such as rubber, foam, and some soft tissues.
o MAT_HYPERELASTIC_RUBBER (MAT_077H) or MAT_SIMPLIFIED_RUBBER_FOAM (MAT_181) are recommended for general rubber-like materials.
o MAT_MOONEY-RIVLIN_RUBBER (MAT_027) is another classic hyperelastic model, though sometimes less recommended than newer models depending on the specific application.
o These models define the material behavior based on an energy potential function rather than a constant modulus, capturing the storage and release of energy during deformation.
· Orthotropic Nonlinear Elastic Materials: LS-DYNA includes models for materials with directional properties.
o MAT_ORTHOTROPIC_ELASTIC (MAT_002) is a hyperelastic model suitable for large elastic deformations in orthotropic materials, like some composites.
· Discrete Elements: For modeling components like springs or beams, specific nonlinear elastic models are available.
o MAT_067 (NONLINEAR_ELASTIC_DISCRETE_BEAM) and MAT_S04 (SPRING_NONLINEAR_ELASTIC) define nonlinear force-displacement relationships for discrete elements.
Considerations for Implementation
· Model Selection: The selection of the appropriate *MAT card is the first and most critical step. The Ansys LS-DYNA Material Models page provides a useful selector tool.
· Material Characterization: Most advanced nonlinear elastic models require input data (e.g., stress-strain curves from physical testing) to define their parameters accurately.
· Hypoelasticity vs. Hyperelasticity: LS-DYNA's basic MAT_ELASTIC is a hypoelastic model, which may cause instabilities or nonlinear behavior at large strains and is generally not recommended for modeling rubber-like behavior. Hyperelastic models (e.g., MAT_077H) are preferred for large, fully recoverable deformations.
· Implicit vs. Explicit Solvers: Nonlinear elastic problems can often be solved using either explicit or implicit methods in LS-DYNA, depending on the specific problem dynamics and stability requirements.
· Validation: It is essential to compare the stress-strain results from the simulation with physical test data to validate the chosen material model and its parameters.
Sincerely,
James M. Kennedy
KBS2 Inc.
November 22, 2025
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