In general, materials have a complex response to dynamic loading and the following phenomena may need to be modeled.
Non-linear pressure response
Strain hardening
Strain rate hardening
Pressure hardening
Thermal softening
Compaction (for example, porous materials)
Orthotropic response (for example, composites)
Crushing damage (for example, ceramics, glass, concrete)
Chemical energy deposition (for example, explosives)
Tensile failure
Phase changes (for example, solid-liquid-gas)
The modeling of such phenomena can generally be broken down into three components:
Equation of State
An equation of state describes the hydrodynamic response of a material.
This is the primary response for gases and liquids, which can sustain no shear. Their response to dynamic loading is assumed hydrodynamic, with pressure varying as a function of density and internal energy.
This is also the primary response for solids at high deformation rates, when the hydrodynamic pressure is far greater than the yield stress of the material.
Material Strength Model
Solid materials may initially respond elastically, but under highly dynamic loadings, they can reach stress states that exceed their yield stress and deform plastically. Material strength laws describe this non-linear elastic-plastic response.
Material Failure Model
Solids usually fail under extreme loading conditions, resulting in crushed or cracked material. Material failure models simulate the various ways in which materials fail. Liquids will also fail in tension, a phenomenon usually referred to as cavitation.
Material Erosion Model
An erosion model can be added to any material in Engineering Data. Erosion models are used to overcome problems caused by large mesh distortions in Lagrange meshes. They do not model any physical phenomena, but can remove elements from the simulation which are heavily distorted or degenerate, and may cause the overall timestep of the analysis to become extremely small. See Erosion for further details on the erosion models which are available in Engineering Data.
Erosion models added to materials in Engineering Data work in combination with the global Erosion Controls specified in the Analysis Settings of an Explicit Dynamics analysis.
Engineering Data properties for explicit analyses in the Mechanical application cover a wide range of materials and material behaviors. Some examples are provided below:
| Class of Material | Material Effects |
|---|---|
| Metals |
Elasticity Shock Effects Plasticity Isotropic Strain Hardening Kinematic Strain Hardening Isotropic Strain Rate Hardening Isotropic Thermal Softening Ductile Fracture Brittle Fracture (Fracture Energy based) Dynamic Failure (Spall) |
| Concrete/Rock |
Elasticity Shock Effects Porous Compaction Plasticity Strain Hardening Strain Rate Hardening in Compression Strain Rate Hardening in Tension Pressure Dependent Plasticity Lode Angle Dependent Plasticity Shear Damage/Fracture Tensile Damage/Fracture |
| Solid/Sand |
Elasticity Shock Effects Porous Compaction Plasticity Pressure Dependent Plasticity Shear Damage/Fracture Tensile Damage/Fracture |
| Rubbers/Polymers |
Elasticity Viscoelasticity Hyperelasticity |
| Orthotropic |
Orthotropic Elasticity Orthotropic Strength |
The Engineering Data properties supported by explicit analysis are described below. Additional material modeling options, particularly in the areas of composite materials and reactive materials, are available in the Ansys Autodyn product.