Meaning
Standard test protocols for thermomechanical fatigue evaluate material performance under simultaneous mechanical strain and temperature cycling. Standardizing this procedure allows laboratories to isolate thermal strain from mechanical strain during high-temperature testing. Compliance with astm e2368 ensures uniform phase relationships between temperature cycles and applied displacement.
This standard governs test piece geometry, temperature measurement methods, and data recording rates for metallic alloys used in high-temperature structural components.
Strain Control
Axial strain measurements require precise separation of thermal expansion from mechanical force to ensure valid fatigue data. Testing under astm e2368 demands high-frequency control loops that adjust total strain in real time based on continuous thermal expansion calculations. System calibrations prevent thermal lag from distorting the command signal during rapid temperature ramps.
Thermal Gradient
Dynamic heating and cooling rates generate internal temperature gradients across the specimen cross section. Under astm e2368, induction coils or direct electrical resistance heating keep axial temperature variations within specified limits across the gage section. Thermocouple contact and thermal response times are strictly specified to eliminate measurement lag.
Failure Threshold
Material life end conditions are defined by a measurable drop in tensile stress or complete physical separation. Data collected under astm e2368 provides baseline fatigue curves for structural design tools operating under combined thermal and mechanical fatigue conditions. The resulting stress strain response isolates high-temperature degradation mechanisms for accurate component life predictions.
