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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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2. USER’S MANUAL

This section is intended to be a brief user’s manual for those users who want to run the model with a cursory, rather than indepth, understanding of the underlying theory and equations. This section includes a description of the LS-DYNA wood model input, a brief parameter description, and methods of fitting the parameters to data. This section concludes with a brief description of the wood model theory and an example output file.

2.1 LS-DYNA INPUT

*MAT_WOOD_{OPTION}

This is material type 143. This is a transversely isotropic material and is available for solid elements in LS-DYNA. The user has the option of inputting his or her own material properties (<BLANK> option) or requesting default material properties for southern yellow pine (PINE) or Douglas fir (FIR).

Options include:
PINE
FIR
<BLANK>
such that the keyword cards appear:
*MAT_WOOD_PINE
*MAT_WOOD_FIR
*MAT_WOOD

Define the following card for all options:

Card Format

Card 1 1 2 3 4 5 6 7 8
Variable MID RO NPLOT ITERS IRATE GHARD IFAIL  
Type I F I I I F I  

Define the following cards for the PINE and FIR options:

Card 2 1 2 3 4 5 6 7 8
Variable MC TEMP QT QC UNITS IQUAL    
Type F F F F I I    

Define the following cards for the <BLANK> option (do not define for PINE or FIR):

Card 3 1 2 3 4 5 6 7 8
Variable EL ET GLT GTR nLT      
Type F F F F F      
Card 4 1 2 3 4 5 6 7 8
Variable XT XC YT YC S|| S^    
Type F F F F F F    
Card 5 1 2 3 4 5 6 7 8
Variable Gf I^ Gf II || B dmax|| Gf I^ Gf II^ D dmax^
Type F F F F F F F F
Card 6 1 2 3 4 5 6 7 8
Variable h|| hC|| n|| h^ hC^ n^    
Type F F F F F F    
Card 7 1 2 3 4 5 6 7 8
Variable N|| c|| N^ c^        
Type F F F F        

Define for all options:

Card 8 1 2 3 4 5 6 7 8
Variable AOPT              
Type I              
Card 9 1 2 3 4 5 6 7 8
Variable XP YP ZP A1 A2 A3    
Type F F F F F F    
Card 10 1 2 3 4 5 6 7 8
Variable D1 D2 D3          
Type F F F          
Variable Description
MID

Material identification (a unique number has to be chosen)

RO

Mass density

NPLOT

Plotting options:
EQ. 1: Maximum of parallel and perpendicular damage (default)
EQ. 2: Perpendicular damage

ITERS

Number of plasticity algorithm iterations (default is one iteration; values greater than 1 are not recommended)

IRATE

Rate-effect options:
EQ. 0: Rate-effect model turned off (default)
EQ. 1: Rate-effect model turned on

GHARD

Perfect plasticity override (values greater than or equal to zero are allowed). Positive values model late-time hardening in compression (an increase in strength with increasing strain). A zero value models perfect plasticity (no increase in strength with increasing strain). The default is zero.

IFAIL

Erosion perpendicular to the grain:
EQ. 0: No (default)
EQ. 1: Yes (not recommended except for debugging)

Define for PINE and FIR options:

Variable Description
MC

Percent moisture content (if left blank, moisture content defaults to saturated at 30 percent)

TEMP

Temperature in °C (if left blank, temperature defaults to room temperature at 20 °C)

QT

Quality factor options (these quality factors reduce the clear wood tension/shear and compression strengths as a function of grade):

EQ. 0: Grades 1, 1D, 2, 2D

 

Predefined strength-reduction factors are:

Pine: QT = 0.47 in tension/shear
QC = 0.63 in compression
Fir: QT = 0.40 in tension/shear
QC = 0.70 in compression

EQ. -1:DS-65 or SEL STR

 

Predefined strength-reduction factors are:

QT = 0.80 in tension/shear
QC = 0.93 in compression

EQ. -2:Clear wood

 
QT = 1.0 in tension/shear
QC = 1.0 in compression
GT. 0: User-defined quality factor in tension (values greater than 0 and less than or equal to 1 are expected; values greater than 1 are allowed, but may not be realistic.
QC

User-defined quality factor in compression (This input value is used if QT > 0. Values greater than 0 and less than or equal to 1 are expected. Values greater than 1 are allowed, but may not be realistic. If left blank when QT > 0, a default value of QC = QT is used.)

UNITS

Unit options:
EQ. 0: gigapascals (GPa), mm, milliseconds (ms), kilograms per cubic millimeter (kg/mm3), kilonewtons (kN)
EQ. 1: MPa, ms, grams per cubic millimeter (g/mm3), newtons (N)
EQ. 2: MPa, mm, s, megagrams per cubic millimeter (Mg/mm3), N
EQ. 3: lbf/inch2, inch, s, pound second squared per inch to the fourth power (lb-s2/inch4), pounds force (lbf)

IQUAL

Apply quality factors perpendicular to the grain:
EQ. 0: Yes (default)
EQ. 1: No

Remarks: Material property data are for clear wood (small samples without defects such as knots), whereas real structures are composed of graded wood. Clear wood is stronger than graded wood. Quality factors (strength-reduction factors) are applied to the clear wood strengths to account for reductions in strength as a function of grade. One quality factor (QT) is applied to the tensile and shear strengths. A second quality factor (QC) is applied to the compressive strengths. As an option, predefined quality factors are provided based on correlations between LS-DYNA calculations and test data for pine and fir posts impacted by bogie vehicles. By default, quality factors are applied to the parallel strengths and to the perpendicular strengths. An option is available (IQUAL) to eliminate application perpendicular to the grain.

Define for <BLANK> option only:

Variable Description
EL

Parallel normal modulus

ET

Perpendicular normal modulus

GLT

Parallel shear modulus (GLR = GLT)

GTR

Perpendicular shear modulus

nLT

Parallel major Poisson’s ratio

XT

Parallel tensile strength

XC

Parallel compressive strength

YT

Perpendicular tensile strength

YC

Perpendicular compressive strength

S||

Parallel shear strength

S^

Perpendicular shear strength

Gf I ||

Parallel fracture energy in tension

Gf II ||

Parallel fracture energy in shear

B

Parallel softening parameter

dmax||

Parallel maximum damage

Gf I ^

Perpendicular fracture energy in tension

Gf II ^

Perpendicular fracture energy in shear

D

Perpendicular softening parameter

dmax^

Perpendicular maximum damage

h||

Parallel fluidity parameter in tension/shear

hc||

Parallel fluidity parameter in compression

n||

Parallel power

h^

Perpendicular fluidity parameter in tension/shear

hc^

Perpendicular fluidity parameter in compression

n^

Perpendicular power

N||

Parallel hardening initiation

c||

Parallel hardening rate

N^

Perpendicular hardening initiation

c^

Perpendicular hardening rate

Define for all options:

AOPT  material axes option (see MAT_OPTIONTROPIC_ELASTIC for a more complete description):

 

EQ. 0: Locally orthotropic with material axes determined by element

 

EQ. 1: Locally orthotropic with material axes determined by a point in space and the global location of the element center; this is the a-direction

 

EQ. 2: Globally orthotropic with material axes determined by vectors defined below, as with *DEFINE_COORDINATE_VECTOR

XP, YP, ZP    Coordinates of point p for AOPT = 1

A1, A2, A3    Coordinates of vector a for AOPT = 2

D1, D2, D3    Components of vector d for AOPT = 2

Remarks: One common option is AOPT = 2. The user defines vectors a and d. Typically, a is the parallel-to-the-grain direction and d is one of the perpendicular-to-the-grain directions. Then, a x d = c and c x a = b, where a, b, and c are the principal material axes.

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