CZone crush stress

CZone crush stress is characteristic of the compressive crush stress magnitude of a material at an active crush front for the CZone capability.

CZone crush stress:

  • is required for the CZone crush modeling technique (see CZone analysis);

  • is specified as a material property but does not directly influence constitutive calculations associated with element integration points;

  • limits the contact pressure magnitude at an actively crushing interface, such that the compressive stress of the underlying material approximately equals the crush stress at an active crush front;

  • is relevant only in the context of shell elements; and

  • can depend on the deformation rate at the crush front, material direction, temperature, or field variables.

This page discusses:

See Also
In Other Guides
*CRUSH STRESS
*CRUSH STRESS VELOCITY FACTOR
CZone analysis

ProductsAbaqus/Explicit

CZone crush stress

The crush stress can be thought of as the stress of the crushing body at the crushing interface. The crush stress is specified as a material property but actually does not directly influence the constitutive calculations associated with element integration points; rather, the crush stress limits the contact pressure magnitude at an actively crushing interface as discussed in CZone analysis.

The crush stress in the composite material can be a constant or can vary as a function of the angle, θ, between the local x-direction of the crushable element and the contact normal direction projected to the plane of the element.

Input File Usage

Use the following option to define a constant crush stress:

CRUSH STRESS
crush stress

Use the following option to define the dependence of crush stress on the angle θ:

CRUSH STRESS
crush stress, material angle in degrees

For example:

CRUSH STRESS
90.0, 0.0
60.0, 45
90.0, 90
60.0, 135
90.0, 180

Crush stress as a function of a field variable

The crush stress in the composite material can vary as a function of a predefined field variable. This field variable can represent any physical or geometrical quantity that might affect the crush stress, such as curvature of the laminate.

Input File Usage

Use the following option to define the crush stress as a function of a field variable:

CRUSH STRESS, DEPENDENCIES

For example, the following definition can be used to define a crush stress that increases by 10% in curved regions of the model versus flat regions. The example assumes that curvature information is defined by the second field variable (FV2), which has been initialized with a value of one at the nodes in the curved regions of the model and a value of zero in the flat regions. Field variable dependency is evaluated only at the beginning of the analysis. Subsequent changes in the field variable will have no effect on the crush stress of the material. 

CRUSH STRESS, DEPENDENCIES=5
90.0,   0.0, , , 0.0
60.0,  45.0, , , 0.0
90.0,  90.0, , , 0.0
60.0, 135.0, , , 0.0
90.0, 180.0, , , 0.0
99.0,   0.0, , , 1.0
66.0,  45.0, , , 1.0
99.0,  90.0, , , 1.0
66.0, 135.0, , , 1.0
99.0, 180.0, , , 1.0

Crush stress as a function of velocity

The crush stress in the composite material can depend on the deformation rate at the crush front. The crush stress velocity factor is used to scale the crush stress based upon velocity. The scaling factor is calculated from a user-supplied table of scaling factor versus relative surface velocity.

The final crush stress is the velocity dependence factor multiplied by the original crush stress. No extrapolation of the supplied data is performed for velocities that lie outside the maximum or minimum value supplied, as shown in Figure 1.

Figure 1. Crush stress is held constant outside of the supplied data range.

Input File Usage

Use the following option to specify the crush stress velocity factor:

CRUSH STRESS VELOCITY FACTOR

For example:

CRUSH STRESS VELOCITY FACTOR
1.5, 0.0
1.5, 1.0
1.25, 10.0
1.0, 100.

Elements

CZone crush stress is relevant only for shell elements in Abaqus/Explicit.