Damage initiation for ductile materials in low-cycle fatigue

Damage initiation criteria for ductile materials

The damage initiation criterion is a phenomenological model for predicting the onset of damage due to stress reversals and the accumulation of inelastic strain in a low-cycle fatigue analysis. It is characterized by the accumulated inelastic hysteresis energy per cycle, $Δ w$ , in a material point when the structure response is stabilized in the cycle. The cycle number in which damage is initiated is given by

N_{0} = c_{1} Δ w^{c_{2}},

where $c_{1}$ and $c_{2}$ are material constants. The value of $c_{1}$ is dependent on the system of units in which you are working; some care is required to modify $c_{1}$ when converting to a different system of units.

The initiation criterion can be used in conjunction with any ductile material.

Input File Usage

DAMAGE INITIATION, CRITERION=HYSTERESIS ENERGY

Elements

The damage initiation criteria for ductile materials can be used with any elements in Abaqus/Standard that include mechanical behavior (elements that have displacement degrees of freedom). This includes cohesive elements based on a continuum approach (Modeling of an adhesive layer of finite thickness).

Output

In addition to the standard output identifiers available in Abaqus/Standard (Abaqus/Standard output variable identifiers), the following variable has special meaning when a damage initiation criterion is specified:

CYCLEINI: Number of cycles to initialize the damage at the material point.