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ISO 12111 & ASTM E2368 Metallic materials — Fatigue testing — Strain-controlled thermomechanical fatigue testing method
ISO 12111:2011Metallic materials — Fatigue testing — Strain-controlled thermomechanical fatigue testing method
ISO 12111:2011 is applicable to the TMF (thermomechanical fatigue) testing of uniaxially loaded metallic specimens under strain control. Specifications allow for any constant cyclic amplitude of mechanical strain and temperature with any constant cyclic mechanical strain ratio and any constant cyclic temperature-mechanical strain phasing.
ASTM E2368-24 Standard Practice for Strain Controlled Thermomechanical Fatigue TestingSignificance and Use
In the utilization of structural materials in elevated temperature environments, components that are susceptible to fatigue damage may experience some form of simultaneously varying thermal and mechanical forces throughout a given cycle. These conditions are often of critical concern because they combine temperature dependent and cycle dependent (fatigue) damage mechanisms with varying severity relating to the phase relationship between cyclic temperature and cyclic mechanical strain. Such effects can be found to influence the evolution of microstructure, micromechanisms of degradation, and a variety of other phenomenological processes that ultimately affect cyclic life. The strain-controlled thermomechanical fatigue test is often used to investigate the effects of simultaneously varying thermal and mechanical loadings under idealized conditions, where cyclic theoretically uniform temperature and strain fields are externally imposed and controlled throughout the gage section of the specimen.
Scope
This practice covers the determination of thermomechanical fatigue (TMF) properties of materials under uniaxially loaded strain-controlled conditions. A “thermomechanical” fatigue cycle is here defined as a condition where uniform temperature and strain fields over the specimen gage section are simultaneously varied and independently controlled. This practice is intended to address TMF testing performed in support of such activities as materials research and development, mechanical design, process and quality control, product performance, and failure analysis. While this practice is specific to strain-controlled testing, many sections will provide useful information for force-controlled or stress-controlled TMF testing.
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