MATX60

Bulk Data Entry Defines additional material properties for piece-wise nonlinear elastic-plastic material for geometric nonlinear analysis.

Format

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
MATX60	`MID`	`EPSPF`	`EPST1`	`EPST2`	`FSMOOTH`	`C`	`F`	`EPSF`
	`TPID`	`PSCA`

Strain rate dependent material, at least 4 times, at most 10 times:

(2)	(3)	(4)
`TID1`	`FSCA1`	`EPSR1`
`TID2`	`FSCA2`	`EPSR2`
etc	etc	etc

Example

(1)	(2)	(3)	(4)	(5)	(6)
MAT1	102	900		0.33	1E1
MATX60	102

	101	1.0	4.2E-7
	102	1.0	4.2e6

Definitions

Field	Contents	SI Unit Example
`MID`	Material ID of the associated MAT1. 1 No default (Integer > 0)
`EPSPF`	Failure plastic strain. Default = 10³⁰ (Real > 0)
`EPST1`	Maximum tensile failure strain. 5 Default = 10³⁰ (Real > 0)
`EPST2`	Maximum tensile failure damage. 6 Default = 2.0*10³⁰ (Real > 0)
`FSMOOTH`	Strain rate smoothing flag. OFF (Default) ON
`C`	Hardening coefficient. 0.0 (Default) The hardening is a full isotropic model. 1.0 Hardening uses the kinematic Prager-Ziegler model. Between 0.0 and 1.0 Hardening is interpolated between the two models. (1.0 ≥ Real ≥ 0)
`F`	Cutoff frequency for strain rate filtering. Only for shell and solid elements. Default = 10³⁰ (Real ≥ 0)
`EPSF`	Tensile strain for element deletion. Default = 3.0*10³⁰ (Real > 0)
`TPID`	Identification number of a TABLES1 that defines pressure dependent yield stress function. No default (Integer > 0)
`PSCA`	Scale factor for stress in pressure dependent function. Default = 1.0 (Real)
`TIDi`	Identification number of a TABLES1 that defines the yield stress vs. plastic strain rate function corresponding to EPSRi. Separate functions must be defined for different strain rates. No default (Integer > 0)
`FSCAi`	Scale factor for `TIDi`. Default = 1.0 (Real)
EPSRi	Strain rate. Strain rate values must be given strictly in ascending order. (Real)

Comments

The material identification number must be that of an existing MAT1 Bulk Data Entry. Only one MATX60 material extension can be associated with a particular MAT1.
MATX60 is only applied in geometric nonlinear analysis subcases which are defined by ANALYSIS = EXPDYN. It is ignored for all other subcases.
The first point of yield stress functions (plastic strain vs. stress) should have a plastic strain value of zero. If the last point of the first (static) function equals 0 in stress, the default value of EPSMAX is set to the value of the corresponding plastic strain.
When the plastic strain reaches EPSMAX, the element is deleted.
If the first principal strain $ε$ ₁ reaches $ε$ _t1 (EPST1), the stress $σ$ is reduced by:
(1)
$σ = σ (\frac{ε_{t 2} - ε_{1}}{ε_{t 2} - ε_{t 1}})$

with $ε$ _t2 = EPST2.
If the first principal strain $ε$ ₁ reaches $ε$ _t2 (EPST2), the stress is reduced to 0 (but the element is not deleted).
If the first principal strain $ε$ ₁ reaches $ε$ _f (EPSF), the element is deleted.
Strain rate filtering is used to smooth strain rates. The input F is available only for shell and solid elements.
Hardening is defined by ICH.

Figure 1. Isotropic Hardening

Figure 2. Prager-Ziegler Kinematic Hardening
The kinematic hardening model is not available with global formulation (NIP = 0 on PSHELX), that is hardening is fully isotropic.
In case of kinematic hardening and strain rate dependency, the yield stress depends on the strain rate.
TPID is used to distinguish the behavior in tension and compression for certain materials (that is pressure dependent yield). This is available for solid elements only. The effective yield stress is then obtained by multiplying the nominal yield stress by the yield factor PSCA corresponding to the actual pressure.
If ${\dot{ε}}_{n} \leq \dot{ε} \leq {\dot{ε}}_{n + 1}$ ( ${\dot{ε}}_{n}$ =EPSRn), yield stress is a cubic interpolation between functions f_n-1, f_n, f_n+1 and f_n+2.
If $\dot{ε} \leq {\dot{ε}}_{1}$ , yield stress is interpolated between functions f₁, f₂, and f₃.

If ${\dot{ε}}_{Nfunc- 1} \leq \dot{ε} \leq {\dot{ε}}_{Nfunc}$ , where Nfunc is the function number for strain rate, yield is extrapolated between functions f_Nfunc-3, f_Nfunc-2, f_Nfunc-1 and f_Nfunc.

If $\dot{ε} > {\dot{ε}}_{Nfunc}$ , yield is extrapolated between functions f_Nfunc-2, f_Nfunc-1, and f_Nfunc.
Strain rate values must be given strictly in ascending order. Separate functions must be defined for different strain rates.
This card is represented as an extension to a MAT1 material in HyperMesh.