/MAT/LAW87 (BARLAT2000)
Block Format Keyword This elasto-plastic law is developed for anisotropic materials, especially aluminum alloys.
Yield stresses can be defined either by user-defined functions (plastic strain versus stress) or analytically by a combination of Swift-Voce model. The model is based on Barlat YLD2000 criterion. 1
Format
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
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/MAT/LAW87/mat_ID/unit_ID or /MAT/BARLAT2000/mat_ID/unit_ID | |||||||||
mat_title | |||||||||
ρi | |||||||||
E | ν | Iflag | VP | c | p |
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
---|---|---|---|---|---|---|---|---|---|
α1 | α2 | α3 | α4 | Ifit | |||||
α5 | α6 | α7 | α8 |
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
---|---|---|---|---|---|---|---|---|---|
σ00 | σ45 | σ90 | σb | Ifit | |||||
r00 | r45 | r90 | rb |
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
---|---|---|---|---|---|---|---|---|---|
Chard |
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
---|---|---|---|---|---|---|---|---|---|
a | Fcut | Fsmooth | Nrate | ||||||
Blank line |
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
---|---|---|---|---|---|---|---|---|---|
fct_IDi | Fscalei | ˙εi |
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
---|---|---|---|---|---|---|---|---|---|
a | αsv | n | Fcut | Fsmooth | |||||
A | ε0 | Q | B | K0 |
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
---|---|---|---|---|---|---|---|---|---|
a | |||||||||
Am | Bm | Cm | Dm | Pm | |||||
Qm | ε0 mart | VM0 | |||||||
AHS | BHS | MHS | NHS | EPS0HS | |||||
HMART | K1 | K2 | |||||||
T0 | Cp | Eta |
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
---|---|---|---|---|---|---|---|---|---|
CRC1 | CRA1 | CRC2 | CRA2 | ||||||
CRC3 | CRA3 | CRC4 | CRA4 |
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) |
|
ρi | Initial
density (Real) |
[kgm3] |
E | Young's
modulus (Real) |
[Pa] |
ν | Poisson's
ratio (Real) |
|
Iflag | Yield stress definition flag.
(Integer) |
|
VP | Strain rate choice flag.
4
(Integer) |
|
Ifit | Material parameter fit flag.
|
|
αi | Barlat material parameters
with i=1~8. (Real) |
|
σ00 | Yield strength in 00
direction (rolling direction). (Real) |
[Pa] |
σ45 | Yield strength in 45
direction. (Real) |
[Pa] |
σ90 | Yield strength in 90
direction. (Real) |
[Pa] |
σb | Yield strength biaxial
loading. (Real) |
[Pa] |
r00 | Lankford r-value in 00
direction (rolling direction). (Real) |
|
r45 | Lankford r-value in 45
direction. (Real) |
|
r90 | Lankford r-value in 90
direction. (Real) |
|
rb | Lankford r-value in
biaxial loading. (Real) |
|
Chard | Hardening coefficient.
|
|
a | Exponent in yield
function. 2 Default = 2 (Integer) |
|
αsv | Swift-Voce weighting
coefficient. 2
Default = 0.0 (Real) |
|
Q | Voce hardening
coefficient. (Real) |
[Pa] |
K0 | Voce hardening
parameter. (Real) |
[Pa] |
B | Voce plastic strain
coefficient. Default = 0.0 (Real) |
|
A | Swift hardening
coefficient. (Real) |
[Pa] |
n | Swift hardening
exponent. Default = 1.0 (Real) |
|
ε0 | Swift hardening
parameter. Default = 0.00 (Real) |
|
Fsmooth | Smooth strain rate option
flag when VP=0. 4
(Integer) |
|
Fcut | Cutoff frequency for
strain rate filtering, Appendix: Filtering. 7 Default = 10KHz (Real) |
[Hz] |
c | Cowper-Seymonds reference
strain rate. (Real) |
[1s] |
p | Cowper-Seymonds strain
rate exponent. 5 (Real) |
|
Nrate | Number of yield functions.
2
(Integer) |
|
fct_IDi | Yield stress versus plastic strain
identifier. (Integer) |
|
Fscalei | Scale factor for ordinate for fct_IDi. Default = 1.0 (Real) |
[Pa] |
˙εi | Strain rate
i corresponding to fct_IDi.
Default = 1.0 (Real) 5 |
[1s] |
Am | Parameter A for martensite
rate equation. (Real) |
|
Bm | Parameter B for martensite
rate equation. (Real) |
|
Cm | Parameter C for martensite
rate equation. (Real) |
|
Dm | Parameter D for martensite
rate equation. (Real) |
[1K] |
Pm | Parameter P for martensite
rate equation. (Real) |
|
Qm | Parameter Q for martensite
rate equation. (Real) |
[K] |
ε0 mart | Parameter
ε0
for martensite rate
equation. (Real) |
|
VM0 | Initial volume fraction
VM0 for martensite rate
equation. (Real) |
|
AHS | Parameter
AHS
in Hansel hardening
law. (Real) |
[Pa] |
BHS | Parameter
BHS
in Hansel hardening
law. (Real) |
[Pa] |
MHS | Coefficient
m
in Hansel hardening
law. (Real) |
|
NHS | Exponent
n
in Hansel hardening
law. (Real) |
|
EPS0HS | Reference strain
ε0
in Hansel hardening
law. (Real) |
|
HMART | Martensite ΔHγα coefficient in Hansel hardening law. | [Pa] |
K1 | Temperature parameter
K1
in Hansel hardening
law. (Real) |
|
K2 | Temperature parameter
K2
in Hansel hardening
law. (Real) |
|
T0 | Initial
temperature. (Real) |
[K] |
Cp | Specific heat per mass
unit. (Real) |
[Jkg⋅K] |
Eta | Taylor-Quinney
coefficient. (Real) |
|
CRCi | Chaboche Rousselier
kinematic parameter C i=1~4. (Real) 3 |
|
CRAi | Chaboche Rousselier
kinematic parameter A i=1~4. (Real) 3 |
[Pa] |
▸Example 1 (with Barlat parameters input Iflag=0 and Ifit=0)
▸Example 2 (with experiment data input Ifit=1)
▸Example 3 (with Hansel yield model (Iflag=2) and kinematic hardening model (Chard=1))
Comments
- The yield function is
expressed as:
(1) f=ˉσ−σy(2) ˉσ= 121a(φ′(X′)+φ″(X″)) 1a(3) φ′(X′)=|X′1−X′2|a(4) φ″(X″)=|2X″2+X″1|a+|2X″1+X″2|aX' and X" denote the principal values of the tensors X' and X" which are a linear transformation of the stress deviator, which leads to:(5) φ′(X′)= [(X′xx−X′yy)2+4(X′xy)2]a2(6) φ″(X″)=[32(X″xx−X″yy)+12√(X″xx−X″yy)2+4(X″xy)2]a+[32(X″xx−X″yy)−12√(X″xx−X″yy)2+4(X″xy)2]aThe tensors X' and X" are linear transformations of the stress tensor:
X′=L′σ and X″=L″σ(7) L′=13[2α1−α10−α22α20003α7](8) L″=19[−2α3+2α4+8α5−2α6α3−4α4−4α5+4α604α3−4α4−4α5+α6−2α3+8α4+2α5−2α60009α8] - The yield stress could
be defined either by tabulated input or using the analytic Swift-Voce model.
- Iflag=0: Tabulated.
- It is possible to add total strain rate dependency by defining a number Nrate of functions.
- Iflag=1: The analytic Swift-Voce model is expressed
as:
(9) σy=αsv[A(ˉεp+ε0)n]+(1−αsv)[K0+Q(1−exp(−Bˉεp))]Where,- ˉεp
- Equivalent plastic strain.
- Iflag=2: Hansel hardening model is
considered.
(10) σy={BHS−(BHS−AHS)e(−m[ˉεp+ε0]n)}(K1−K2T)+ΔHγαVmTemperature is updated in the law when adiabatic conditions:(11) ΔT=ηˉσdˉεpρCpThe martensite rate equation is computed as follows:(12) ∂Vm∂ε={0ifε<ε0BA⋅e(QT)⋅(1−VmVm)(B+1B)⋅(Vm)p2⋅(1−tanh[C+DT])fε≥ε0
- Iflag=0: Tabulated.
- If
Chard>0, a kinematic hardening model of Chaboche
Rousselier is used:
- The back stress is
calculated as:
(13) With,a=4∑i=1ai(14) ai=AiCidεp−CiaiΔˉεp - The yield stress is
computed as follows when combined isotropic kinematic hardening is
chosen:
(15) σy=(1−Chard).σiso_hard+Chard.σkin_hard
- The back stress is
calculated as:
- The strain rate
filtering is available to smooth strain rates when tabulated input is
chosen.List of Animation output (in /ANIM/SHELL/USRII/JJ):
- USR 1= plastic strain
- USR 2= effective stress
- USR 3= increment of plastic strain
- When Iflag=1 (analytic Swift-Voce formulation is used) strain rates
effect is taken into account using Cowper-Symonds expression:
(16) σy=σy(1+(˙εc)1p)If VP=0: ˙ε is the total strain rate.
If VP=1: ˙ε is the plastic strain rate.
If c=0 or p=0, the strain rate effects are not taken into account.
- When Iflag=0 (tabulated formulation) then:
If VP=0: ˙εi is the total strain rate.
If VP =1: ˙εi is the plastic strain rate.
- Strain rate
filtering:
If VP=0 (dependency on strain rate), the default value of Fcut = 10KHz.
If VP=1 (dependency on plastic strain rate), Fsmooth and Fcut are ignored.
- If Ifit=1, the coefficients αi will be automatically fit in the Radioss Starter. The tensile yield strengths σ00,σ45,σ90 and Lankford ratios r00,r45,r90 must be determined from uniaxial tension experiments along the rolling, diagonal and transverse directions at an amount of plastic work corresponding to a plastic strain equal to 0.2%. σb and rb should be determined from biaxial test, for the same amount of plastic strain.