Meaning
Material degradation modes occur when structural components experience simultaneous cyclic mechanical stresses and transient thermal fields. Structural durability assessments evaluating thermo mechanical fatigue analyze damage caused by constrained thermal expansion in constrained battery pack structures and cooling manifolds. The interaction between thermal strain and mechanical load alters crack initiation and propagation rates compared to room-temperature fatigue testing.
Engineering teams evaluate this phenomenon to design resilient busbar connections and heat exchangers capable of enduring thousands of thermal shock cycles over vehicle operating lifespans.
Damage Mechanism
Combined thermal cycling and cyclic mechanical stress accelerate creep deformation and grain boundary oxidation within structural metals. Under thermo mechanical fatigue conditions, phase differences between strain and temperature alter the microstructural degradation path, creating intergranular cracking at lower total cycle counts. Mechanical constraint prevents natural expansion, converting thermal energy directly into high internal stresses.
Cycle Testing
Validation testing utilizes specialized servo-hydraulic test frames equipped with rapid induction heating and forced-air cooling systems. Characterization of thermo mechanical fatigue requires controlling temperature waveforms and mechanical strain profiles simultaneously under closed-loop digital feedback. Test protocols measure stress relaxation and hysteresis energy to build predictive damage accumulation models.
Design Constraint
Component engineering requires minimizing structural constraints that prevent free thermal expansion. Flex joints and expansion loops mitigate stress concentration in high-temperature pack regions.
