/MAT/LAW71
Block Format Keyword This law describes the behavior of superelastic materials. It allows modeling the behavior of the shape memory alloys (such as Nitinol).
The particularity of these materials is that all of the strain is recovered upon unloading even when large deformations are reached. Besides, the material shows a hysteretic response in a complete loading-unloading cycle. The full recovery is due to phase change in the microstructure. The model is based on the work of Auricchio et al. 1997. This law is compatible with beam (/PROP/TYPE18 (INT_BEAM) only), solid and shell elements.
Format
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
---|---|---|---|---|---|---|---|---|---|
/MAT/LAW71/mat_ID/unit_ID | |||||||||
mat_title | |||||||||
E | E_mart | ||||||||
EpsL | CAS | CSA | TS_AS | TF_AS | |||||
TS_SA | TF_SA | Cp | Tini |
Definition
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) |
||
E | Young's
modulus. (Real) |
|
Poisson's
ratio. (Real) |
||
E_mart | Martensite Young's
modulus. Default = 0.0 (Real) |
|
Material parameter
defining the start of phase transformation from austenite to
martensite (AS). 1 (Real) |
||
Material parameter
defining the end of phase transformation from austenite to
martensite (AS). 1 (Real) |
||
Material parameter
defining the start of phase transformation from martensite
to austenite (SA). 1 (Real) |
||
Material parameter
defining the end of phase transformation from martensite to
austenite (SA). 1 (Real) |
||
Material parameter
measuring the difference in response between tension and
compression. Default = 0 (Real) |
||
EpsL | Maximum residual
strain. 2 (Real) |
|
CAS | Stress-Temperature
rate during loading. Default = 0 (Real) |
|
CSA | Stress-Temperature
rate during unloading. Default = 0 (Real) |
|
TS_AS | Reference
temperature for start of transformation (AS). Default = 298K (Real) |
|
TF_AS | Reference
temperature for end of transformation (AS). Default = 298K (Real) |
|
TS_SA | Reference
temperature for start of transformation (SA). Default = 298K (Real) |
|
TF_SA | Reference
temperature for end of transformation (SA). Default = 298K (Real) |
|
Cp | Specific heat
capacity. Default = 1030 (Real) |
|
Tini | Initial
temperature. Default = 360 K (Real) |
Example (Metal)
#RADIOSS STARTER
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/UNIT/1
unit for mat
Mg mm s
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
#- 2. MATERIALS:
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/MAT/LAW71/1/1
metal
# RHO_I
6.50E-9
# E Nu E_mart
62500 .3 51000
# sig_AS_s sig_AS_f sig_SA_s sig_SA_f alpha
450 600 300 200 0.20
# EpsL CAS CSA TS_AS TF_AS
0.045 1 1 383 343
# TS_SA TF_SA CP TINI
363 403 837 360
#ENDDATA
/END
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
Comments
- If E_mart=0, then Young's modulus is considered constant, equal to E, and not dependent on the phase fraction of the material.
- The different stresses , , and , defining the start and the end of phase transformation, as well as the residual strain EpsL, correspond to the case of a uniaxial tensile test:
- The parameter
is computed from the initial value of the
austenite to martensite phase transformation in tension
and compression
from the relation.
(1) When /MAT/LAW71 is used with beam elements, the parameter must be set to .
- The Drucker-Prager type
loading function
is introduced using the stress deviator
, the pressure
and the temperature.
(2) Two functions are defined for the start and the final point of transformation from austenite to martensite (A → S) or from martensite to austenite (S → A).(A→S) (S →A) Start point of transformation Final point of transformation Condition Evolution equation of martensite During loading: During unloading: are the material parameters. The conversion of austenite to martensite takes place when above conditions (in table) are verified.
- List of Animation output
(/ANIM/BRICK/USRI):
- USR 1= Martensite phase fraction
- USR 2= Loading function
- USR 3= Unloading function