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发表于 2009-10-10 15:56:31
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来自 湖北武汉
i think foam material is strongly rate dependent.i donot find the illustration related to this topic neither. is the rate dependent theory and FEA fomulation of the model impefect yet? Here are reference selected from help documentation.i do not know how to deal with the rate dependent issue.
Highly compressible (urethane) foam material model often used for padded materials such as seat cushions. In compression, the model assumes hysteresis unloading behavior with possible energy dissipation. In tension the material model behaves linearly until tearing occurs. For uniaxial loading, the model assumes that there is no coupling in transverse directions. By using input shape factor controls (a hysteresis unloading factor (HU), a decay constant (β), and a shape factor for unloading) the observed unloading behavior of foams can be closely approximated. The stress-strain behavior can be specified at only one temperature. Input the elastic modulus (EX) and density (DENS) with the [url=mkMSITStore:C:\Program%20Files\Ansys%20Inc\v100\commonfiles\help\en-us\ansyshelp.chm::/Hlp_C_MP.html]MP[/url] command. Input the load curve ID for nominal stress vs. strain, the tension cutoff (tearing) stress, the hysteresis unloading factor, the decay constant, the viscous coefficient, the shape factor for unloading, the failure option when the cutoff stress is reached, and the bulk viscosity action flag with TB,FOAM,,,,2 and locations 1 - 8 of the TBDATA command:
TB, FOAM,,,,2 | TBDATA, 1, LCID (load curve ID for stress-strain behavior) | TBDATA, 2, TC (tension cutoff stress, default=1E20) | TBDATA, 3, HU (hysteretic unloading factor: between 1.0 - no energy dissipation (default) and 0.0 - full energy dissipation) | TBDATA, 4, β (decay constant) | TBDATA, 5, DAMP (viscous coefficient, values between 0.05 and 0.5 are recommended) | TBDATA, 6, SHAPE (shape unloading factor, default = 1) | TBDATA, 7, FAIL (failure option when cutoff stress is reached: 0.0 - tensile stress remains at cutoff value, 1.0 - tensile stress reset to zero) | TBDATA, 8, BVFLAG (bulk viscosity action flag: 0.0 - no bulk viscosity (recommended) and 1.0 - bulk viscosity active) |
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