/MAT/LAW83

Block Format Keyword

/MAT/LAW83 - Advanced Connection Material

Description

This law describes the Connection material, which can be used to model spotweld, welding line, glue, or adhesive layers in laminate composite material. Elastic and elastoplastic behavior can be defined. The plastic behavior of the material can be coupled in normal and shear directions for corresponding strain-rates. This material is applicable only to solid hexahedron elements (/BRICK) and the material time-step does not depend on element height.

Format

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
/MAT/LAW83/mat_ID/unit_ID
mat_title

E				Imass
fct_ID1		Y_scale1		X_scale1
RN		RS		Fsmooth	Fcut
fct_IDN	fct_IDS	XSCALE

Field	Contents	SI Unit Example
mat_ID	Material identifier (Integer, maximum 10 digits)
unit_ID	Optional unit identifier (Integer, maximum 10 digits)
mat_title	Material title (Character, maximum 100 characters)
	Initial density (Real)
E	Young’s modulus per unit length (Real)
Imass	Mass calculation flag Default = 0 (Integer) = 0: Element mass is calculated using density and volume = 1: Element mass is calculated using density and (means of upper and lower) area
fct_ID1	Normalized yield curve that specifies true stress vs. plastic elongation (Integer)
Y_scale1	Scale factor for ordinate of the normalized function, fct_ID1. See comment 10. Default = 1.0 (Real)
X_scale1	Scale factor for abscissa of the function, fct_ID1 See comment 10. Default = 1.0 (Real)
	Angle parameter used in the calculation of the effective true stress (Comment 8). Default = 0.0 (Real)	rad
	Exponent used in the calculation of the effective true stress (Comment 8). Default = 2.0 (Real)
RN	Maximum true stress in normal direction used in the calculation of effective true stress. Default = 1.0 (Real)
RS	Maximum true stress in shear direction used in the calculation of effective true stress. Default = 1.0 (Real)
Fsmooth	Strain rate filtering flag Default = 0 (Integer) = 0: no strain rate filtering = 1: strain rate filtering
Fcut	Cutoff frequency for the strain rate filtering Default = 1030 (Real)
fct_IDN	Function identifier defining a scale factor vs. the plastic displacement rate in normal direction. (Comment 9) Default = 0 (Integer)
fct_IDS	Function identifier defining a scale factor vs. the plastic displacement rate in shear direction. (Comment 9) Default = 0 (Integer)
XSCALE	Scale factor for the abscissa of functions fct_IDN and fct_IDS (Comment 9) Default = 1.0 (Real)

(Connect)

In this example, normal yield curve is fct_ID1=200. Maximal normal true stress is 0.2 Gpa and maximal shear true stress is 0.4 Gpa. = 2 which is used to fit the mixed-mode load case (30° or 60°) of connection. = 0, peel effect is not considered.

#RADIOSS STARTER

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/UNIT/1

unit for mat

kg mm ms

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

#- 2. MATERIALS:

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/MAT/LAW83/1/1

CONNECT MATERIAL

# RHO_I

7.8E-6

# E Imass

20 0

# fct_ID1 Y_scale1 X_scale1 ALPHA BETA

200 1 1 0 2

# RN RS Fsmooth Fcut

.2 .4 0 0

# fct_IDN fct_IDS XSCALE

0 0 0

/FAIL/SNCONNECT/1/1

# ALPHA_0 BETA_0 ALPHA_F BETA_F Ifail_so ISYM

0 2 0 2 1 1

# fct_0N fct_0S fct_FN fct_FS XSCALE_0 XSCALE_F

2001 2002 2003 2004 1 1

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

#- 3. FUNCTIONS:

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

/FUNCT/200

MAT83 curve

# X Y

0 1

1 1

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

/FUNCT/2001

fct_0N

# X Y

0 .5

1 .5

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

/FUNCT/2002

fct_0S

# X Y

0 .5

1 .5

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

/FUNCT/2003

fct_fN

# X Y

0 1

1 1

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

/FUNCT/2004

fct_fS

# X Y

0 1

1 1

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

#ENDDATA

/END

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

1.	This law is compatible with 8-noded hexadedron elements (/BRICK) only. The orientation of the element normal direction with respect to the element faces is important, and is defined as follows:

prop_connect_10

The element local coordinate system is constructed in the mid-plane section between the bottom (1-2-3-4) and top (5-6-7-8) faces.

mat_law83

The element has four Gauss integration points placed in the mid-plane section defined by points 1a, 2a, 3a, and 4a. These four points (1a, 2a, 3a, and 4a) lie midway between the bottom and top face nodes, and the orientation of the local coordinate axes (r-s-t) is the same as that of shell elements and t-axis is assume to be directed from bottom face to top face.

The stiffness modulus and stresses are defined per elongation in order to be independent from the initial height (from node 1 to 5, in the figure above) of the solid element. For example, E=210000 MPa/mm means that the normal stress increases by 210000 MPa for each 1 mm of elongation until the yield stress limit specified by the yield stress curve is reached. The stiffness in shear direction is assumed to be equal to the stiffness modulus, E. The Poisson’s ratio is equal to zero.

3.	The complete element elongation can be subdivided into an elastic portion (before yield stress is reached) and a portion of the plastic elongation. In the simplest case of uni-axial tension and compression, plastic elongation is calculated as:

normal_elongation_plastic = total_normal_elongation-true_normal_stress/E

The plastic elongation is accounted for when fct_ID1 is specified. This is usually a non-decreasing function, which represents true stress as a function of the plastic elongation. The first abscissa value of the function should be “0” and the first ordinate value is the yield stress. The function may have a stress decrease portion to model material damage.

4.	The material behavior is identical in tension and compression. The normal and shear DOF are not coupled in the elastic region.

5.	The normal and shear DOF are coupled in the plastic region. The effective true stress () is calculated from normal () and shear stress (), as follows:

•	fct_IDN and fct_IDS specify a scaling coefficient for normal and shear stress as a function of the plastic displacement rate.

•	sym is the sinus of the angle between the normal of the lower surface and the normal of the upper surface of the solid element.

6.	The height of the solid element can be equal to zero. The element height does not affect the time step. Only nodal time step is available for this material.

7.	All nodes of the solid elements must be connected to other shells or solid elements, slave nodes of rigid body (/RBODY) or slave nodes of tied interface (/INTER/TYPE2).

8.	When all nodes of the solid element become free, the element is deleted.

9.	The rupture criteria for this material is defined by /FAIL/SNCONNECT.

10.	The true stress will be taken from fct_ID1 as: