Oasys LS-DYNA Environment 8.1 VOLUME 3 ... - Oasys Software

Oasys LS-DYNA Environment: User Guide (Version 8.1)
The formula is:
failure strain = ln (original area)
area at failure
Resultant plasticity (type 28) can be used with Shell or Belytschko-Schwer beam elements to
bypass the normal solution method which calculates stresses at each integration point in the
cross-section. This is computationally cheaper but can be inaccurate in some situations.
Strain rate sensitivity can be included in many of the material types e.g. types 3, 18 and 24 allow
input of Cowper Symonds rate effect parameters. Typical values for mild steel are c = 1300s -1
and p = 5. There is generally less rate effect in high strength steels. If experimental data is
available, use the curve LCSR in material type 24 to define how the rate effect varies with strain
rate the viscoplastic option gives much smoother response but at cost of higher CPU usage.
CONCRETE
Concrete can be represented using material type 78 (MAT_SOIL_CONCRETE), which includes
both volumetric crushing and strain softening in shear (to simulate cracking).
RUBBER
Material type 27 (MAT_MOONEY_RIVLIN_RUBBER) is generally reliable. Others available
include types 31, 77, 7 and 6. Of these, 7 is not recommended. For low strain applications type
6 is recommended.
FOAM
Material types 38 (MAT_BLATZ_KO_FOAM), 53 (CLOSED_CELL_FOAM), 57
(MAT_LOW_DENSITY_FOAM), 62 (MAT_VISCOUS_FOAM), 63
(MAT_CRUSHABLE_FOAM), 75 (MAT_BILKHU_DUBOIS_FOAM) and 83 (FU-CHANG-
FOAM) are all written specifically for foams. It is also possible to model foams using material
types 5 (MAT_SOIL_AND_FOAM) and 26 (MAT_HONEYCOMB). Oasys recommend the
following:
! For materials which show permanent crush (e.g. expanded polystyrene, ureaformaldehyde
foam, etc.), use material type 63. A stress-strain load curve is defined, and
unloading is elastic.
! For materials which show hysteretic stress-strain behaviour but which recover to close
to the original shape, use material type 57. With HU set to 0.01 and BETA set to 0.0, the
amount of hysteresis depends on SHAPE. SHAPE = 10.0 gives high hysteresis (most of
the energy is absorbed) while SHAPE = 0.1 gives negligible hysteresis.
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