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Publication Number: FHWA-HRT-04-097
Date: August 2007

Measured Variability Of Southern Yellow Pine - Manual for LS-DYNA Wood Material Model 143

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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

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