Endurance limit and static failure

Three parameters describe the endurance limit in the strain life approach: the number of cycles at the endurance limit and the corresponding stress and strain. In the Durability page of the Simcenter 3D material definition, entering any one of these three parameters will cause the other two to be calculated.

If the number of cycles (NE) is specified, then the strain at the endurance limit (εE) is calculated from the Manson-Coffin- Morrow equation, and the stress at the endurance limit (σE) is calculated from this strain and the Ramberg-Osgood equation.

Likewise, if the stress or strain at the endurance limit is specified, the other is calculated from the Ramberg-Osgood equation and the corresponding number of cycles to failure is calculated from the Manson-Coffin-Morrow equation.

Parameter	Symbol	Unit
Number of cycles at endurance limit	NE	1
Strain at endurance limit	εE	1%
Stress at endurance limit	σE	MPa

The static failure strength of the material may be specified for tension and compression loads separately. They may be specified by stress values or by strain values. The nonspecified values are calculated consistent according to the Ramberg- Osgood equation. Furthermore it is possible to estimate the static strength of the material.

The estimated tensile strength of the material is determined by the strain where the engineering stress reaches its maximum. The tensile stress value belonging to this strain is calculated consistent to the Ramberg-Osgood equation. The compressive strength in stress is estimated to be three times higher than the tensile strength. The compressive strain is again calculated to be consistent.

This estimation procedure gives in general a very high static strength of the material and should only be used if the real strength of the material is not known. This high estimated strength is visible in the high strain values which lie often over 100%. However, this estimation prevents Specialist Durability from calculating too much static failure in a structure while still showing static failures where the stresses are definitively too high.

Parameter	Symbol	Unit
Tensile strength (Stress)	Smax	MPa
Tensile strength (Strain)	εmax	1%
Compressive strength (Stress)	Smax	MPa
Compressive strength (Strain)	εmin	1%

Learn more

Local stress-strain behavior

Constant amplitude life curves

Determining material properties

Mean stress and damage parameters

Axial versus torsion tests

Notch analysis

The strain-life analysis in Specialist Durability

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Endurance limit and static failure, Simcenter 3D 2021.1 Series

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