Manual for LS-DYNA Wood Material Model 143
1.9 MODEL INPUT
The previous eight subsections reviewed the behavior and properties of wood and the theory of the model. Here, we examine the effects of moisture content, temperature, and grade on model input parameters. Two methods are available for wood model input. One method is to provide the following input parameters:
- Five moduli for transversely isotropic constitutive equations.
- Six strengths for the yield criteria.
- Four prepeak hardening parameters.
- Eight postpeak softening parameters.
- Six rate-effect parameters.
These 29 parameters are listed in table 13 and were discussed in detail throughout this section (“Theoretical Manual”). Any consistent system of units may be used.
A second method is to request default material properties. Default material property requests are listed in table 14. This method is convenient because it allows the user to bypass the manual input of the material parameters.
Default material properties are provided for southern yellow pine and Douglas fir as a function of moisture content, temperature, grade, and units. A discussion of the effects of moisture, temperature, and grade is given in the following three subsections. Four consistent sets of units are available. Most of the default material properties are obtained from clear wood samples tested by FPL.(14)
In addition to the choice between user-supplied and default input parameters, the user may also specify control parameters. Control parameters include material identification, density, options to plot damage, increasing the maximum number of iterations performed by the plasticity algorithm, turning on/off the rate effects, overriding perfect plasticity, and controlling perpendicular erosion.
Table 13. User-supplied parameters for wood material model.
Moduli |
Parallel Normal Modulus |
EL |
Perpendicular Normal Modulus |
ET |
Parallel Shear Modulus |
GLT |
Perpendicular Shear Modulus |
GTR |
Parallel Major Poisson’s Ratio |
nLT |
Strengths |
Parallel Tensile Strength |
XT |
Parallel Compressive Strength |
XC |
Parallel Shear Strength |
S|| |
Perpendicular Compressive Strength |
YC |
Perpendicular Tensile Strength |
YT |
Perpendicular Shear Strength |
S^ |
Hardening |
Parallel Hardening Initiation |
N|| |
Parallel Hardening Rate |
c|| |
Perpendicular Hardening Initiation |
N^ |
Perpendicular Hardening Rate |
c^ |
Softening |
Parallel Mode I Fracture Energy |
Gf I || |
Parallel Mode II Fracture Energy |
Gf II || |
Parallel Softening |
B |
Parallel Maximum Damage |
dmax|| |
Perpendicular Mode I Fracture Energy |
Gf I ^ |
Perpendicular Mode II Fracture Energy |
Gf II ^ |
Perpendicular Softening |
D |
Perpendicular Maximum Damage |
dmax^ |
Rate Effects |
Parallel Fluidity |
h||> |
Parallel Fluidity |
hC|| |
Parallel Power |
n|| |
Perpendicular Fluidity |
h^ |
Perpendicular Fluidity |
hC^ |
Perpendicular Power |
n^ |
Table 14. Default material property requests for wood material model.
| Property |
Choices |
Input |
Wood Species |
Southern Yellow Pine |
Pine |
Douglas Fir |
Fir |
Moisture Content (%) |
30% (default) |
0 |
Any moisture content (MC) |
0 < MC £ 100 |
Temperature (°C) |
20 °C (default) |
0 |
Any temperature (T) |
-50 £ T £ 150 |
Grade |
Grades 1, 1D, 2, or 2D |
QT = 0 |
DS-65 or Structural Select |
QT = -1 |
Clear Wood |
QT = -2 |
Quality Factors (Q) |
0.0 < QT £ 1.0
0.0 < QC £ 1.0 |
Apply Quality Parameters |
Yes IQUAL = 0 |
Perpendicular (IQUAL) |
No IQUAL = 1 |
Wood Species |
GPa, mm, ms, kg/mm3, kN |
0 |
MPa, mm, ms, g/mm3, N |
1 |
MPa, mm, s, Mg/mm3, N |
2 |
lbf/inch2, inch, s, lb-s2/inch4, lbf |
3 |
FHWA-HRT-04-097
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