Thermo-mechanical fatigue module for fe-safe™

fe-safe/TMF™ (thermo-mechanical fatigue) was developed in conjunction with a major engine manufacturer to provide fast and accurate fatigue and durability analysis of structures subjected to fluctuating temperatures and stresses. It is now used widely by companies such as Perkins Engines, Caterpillar and Arvin Meritor.

fe-safe/TMF™ is used in conjunction with the standard version of fe-safe™ and incorporates additional time-dependent thermo-mechanical fatigue mechanisms. The analysis uses stress and temperature results from elastic finite element models. All the standard capabilities of fe-safe™, such as critical plane multiaxial fatigue and analysis of cast irons, are included.

fe-safe/TMF™ is ideal for components such as:

• pistons
• exhaust manifolds
• cylinder heads

fe-safe/TMF™ also allows high frequency mechanical cycles to be superimposed over thermal cycles.

Experience has shown that some or all of these features need to be included for accurate fatigue analysis of many engine components, depending on the type of material and the temperature regime. fe-safe/TMF™ has been used successfully with steel, aluminium and cast iron components, and has provided much more reliable identification of fatigue-critical locations and fatigue lives than is possible with more traditional approaches.

From the elastic FEA solutions, fe-safe/TMF™ generates elastic-plastic stress-strain responses that include the effects of strain rate and instantaneous temperature. A strain-life analysis for multiaxial stress states with standard or user-defined mean stress corrections is used.

A multi-pass fatigue analysis progressively introduces the effects of bulk stress relaxation and strain ageing (the reduction in fatigue strength with time at temperature).

The fatigue damage calculation also includes the effect of phase relationship between stress and temperature in each cycle, and allows damage to be calculated for instantaneous temperature at each point in the fatigue cycle.

fe-safe/Rotate™ is supplied as an optional add-on module for fe-safe™. It currently supports:

• ANSYS RST results files (.rst)
• ABAQUS FIL (.fil) files (ASCII or binary) containing element-nodal data
• MSC NASTRAN (.op2 & f06)
• NX NASTRAN (.op2 & f06)
• Pro/Mechanica (ASCII & binary)
• I-DEAS (.unv)
• Altair Hypermesh & Optistruct)