Ansys nCode DesignLife
Stress & Strain Based Fatigue Life Prediction

The standard EN method uses the Coffin-Manson-Basquin formula, defining the relationship between strain amplitude and the number of cycles to failure.

A wide range of methods are provided for defining the SN curves, including the ability to interpolate multiple material data curves for factors such as mean stress or temperature. Further options are also provided to account for stress gradients and surface finishes.

Output is the safety factor. The program uses material parameters calculated from tensile and torsion tests. Account for manufacturing effects by using equivalent plastic strain in the unloaded component.

This is widely used as a key design criterion for engine and powertrain components.

Covers seam welded joints including fillet, overlap and laser welded joints. Stresses can either be taken directly from FEA models (shell or solid elements) or calculated from grid point forces or displacements at the weld. The approach is appropriate for weld toe, root and throat failures.

Life calculations are made around a spot weld at multiple angle increments and the total life reported includes the worst case. Python scripting enables modeling of other joining methods such as rivets or bolts.

It provides the capability to predict fatigue in the frequency domain and is more realistic and efficient than time-domain analysis for many applications with random loading, such as wind and wave loads.

The Thermo-Mechanical Fatigue (TMF) option provides solvers for high-temperature fatigue and creep by using stress and temperature results from finite element simulations. TMF includes high temperature fatigue methods Chaboche and Chaboche Transient. Creep analysis methods include Larson-Miller and Chaboche creep.

The adhesive bonds option enables durability calculations on adhesive joints in metallic structures. Adhesive bonds are modeled with beam elements and grid point forces are used to determine line forces and moments at the edge of the glued flange. Approximate calculations of the strain energy release rate are made at the edge of the adhesive and, by comparison to the crack growth threshold, a safety factor is calculated.