/MAT/LAW15 (CHANG)
Block Format Keyword This law is used to model composite shell elements, similar to LAW25. The plastic behavior is based on the Tsai-Wu criteria (/MAT/LAW25 (COMPSH) for Tsai-Wu description) and failure is based on the Chang-Chang failure criterion is used.
It is recommended to use material LAW25 in combination with a separate Chang-Chang failure criteria (/MAT/LAW25 with /FAIL/CHANG keywords), instead of material LAW15.
Format
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
---|---|---|---|---|---|---|---|---|---|
/MAT/LAW15/mat_ID/unit_ID or /MAT/CHANG/mat_ID/unit_ID | |||||||||
mat_title | |||||||||
E11 | E22 | ||||||||
G12 | G23 | G31 | |||||||
b | n | fmax | |||||||
Ioff | |||||||||
α | |||||||||
c | ICC | ||||||||
S1 | S2 | S12 | |||||||
Fsmooth | Fcut | C1 | C2 |
Definitions
Field | Contents | SI Unit Example |
---|---|---|
mat_ID | Material
identifier. (Integer, maximum 10 digits) |
|
unit_ID | Unit Identifier. (Integer, maximum 10 digits) |
|
mat_title | Material
title. (Character, maximum 100 characters) |
|
Initial
density. (Real) |
||
E11 | Young's modulus in
direction 1. (Real) |
|
E22 | Young's modulus in
direction 2. (Real) |
|
Poisson's
ratio. (Real) |
||
G12 | Shear
modulus. (Real) |
|
G23 | Shear
modulus. (Real) |
|
G311 | Shear
modulus. (Real) |
|
b | Hardening
parameter. (Real) |
|
n | Hardening
exponent. Default = 1.0 (Real) |
|
fmax | Maximum value of yield
function. 2 Default = 1030 (Real) |
|
Maximum plastic energy per
volume unit. Default = 1030 (Real) |
||
Reference plastic energy
per volume unit. Default = 1.0 (Real) |
||
Ioff | Total element failure
criteria. 4
(Integer) |
|
Composite yield stress in
tension in direction 1. 2 (Real) |
||
Composite yield stress in
tension in direction 2. (Real) |
||
Composite yield stress in
compression in direction 1. (Real) |
||
Composite yield stress in
compression in direction 2. (Real) |
||
α | F12
reduction factor. 2 Default set to 1.0 (Real) |
|
Yield stress in shear and
strain rate compression in direction 12. (Real) |
||
Yield stress in shear and
strain rate tension in direction 12. (Real) |
||
c | Yield stress in shear and
strain rate coefficient. 2
(Real) |
|
Yield stress in shear and
strain rate reference. (Real) |
||
ICC | Strain rate computation
flag. 2
(Integer) |
|
Shear scaling factor.
1 (Real) |
||
Time relaxation. 3 Default = 1030 (Real) |
||
S1 | Longitudinal tensile
strength. 1 Default = 1030 (Real) |
|
S2 | Transverse tensile
strength. Default = 1030 (Real) |
|
S12 | Shear strength. Default = 1030 (Real) |
|
Fsmooth | Smooth strain rate option flag.
(Integer) |
|
Fcut | Cutoff frequency for
strain rate filtering. Default = 1030 (Real) |
|
C1 | Longitudinal compressive
strength. 1 Default = 1030 (Real) |
|
C2 | Transverse compressive
strength. Default = 1030 (Real) |
Example (Carbon)
#RADIOSS STARTER
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/UNIT/1
unit for mat
kg mm ms
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
#- 2. MATERIALS:
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/MAT/LAW15/1/1
Carbon
# RHO_I
1.8E-6 0
# E11 E22 nu12
41 3.3 .3
# G12 G23 G31
5.2 1.3 1.3
# b n fmax
8E-6 1 100000
# Wpmax Wpref Ioff
100000 0 0
# sigma_1yt sigma_2yt sigma_1yc sigma_2yc alpha
.786 .1566 .786 .1566 0
# sigma_12yc sigma_12yt c Eps_dot_0 ICC
.0655 .0655 0 0 0
# beta Tmax S1 S2 S12
1 .01 0 0 0
# Fsmooth Fcut C1 C12
0 0 0 0
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
#ENDDATA
/END
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
Comments
- Chang-Chang failure criteriaSix material parameters are used in the Chang-Chang failure criteria to describe the two different failure behaviors.
- For fiber breakage, the failure criteria is:
- Tensile fiber mode
(1) - Compressive fiber mode
(2)
- Tensile fiber mode
- For matrix cracking, the failure criteria is:
- Tensile fiber mode
(3) - Compressive matrix mode
(4) - Tensile fiber mode
- For fiber breakage, the failure criteria is:
- Before failed (damage parameter is less than 0), material is in elastic–plastic phase. The plastic behavior is based on the TSAI-WU criteria (see Tsai-Wu Formulation (Iform =0) for Tsai-Wu criterion description).
- After failed (damage parameter
is greater than or equal to 0), the stresses are
decreased by using an exponential function to avoid numerical instabilities.A relaxation technique is used by gradually decreasing the stress.
(5) With function of relaxation:
and
Where,- Time
- Start time of relaxation when the damage criteria is assumed
- Time of dynamic relaxation
- Stress components at the beginning of damage
- If a shell has several layers with one material per layer (different materials, different Ioff), the Ioff used is the one which is associated to the shell in the shell element definition.