Multi Axial Creep Fatigue Damage Accumulation in Vacuum Brazed Battery Pack Cooling Structures
Vacuum brazed aluminum cooling plates fail under coupled multi-axial creep-fatigue when pressure pulses interact with static cell swelling constraints.
Fillet Root Geometry
Meaning
Structural profiles defining the transition region between the weld seam and the base metal of a battery cell terminal determine the mechanical fatigue life of the electrical connection. Designers inspect the fillet root geometry of laser welds to ensure the joint can withstand the vibrations of transport applications. This specific contour controls the concentration of local stresses generated during mechanical loading.
It ceases to be the dominant failure factor when the weld penetration depth is insufficient.
Stress Distribution
Modifying the radius of the root joint alters the localized stress distribution under cyclic vibration loads. A generous radius in the fillet root geometry distributes the mechanical load across a wider surface, preventing the initiation of microcracks. In contrast, sharp transitions concentrate the forces and lead to rapid crack propagation.
Designers balance this shape against the speed of the laser welding process.
Manufacturing Limit
Controlling the laser power and scanning speed during terminal assembly dictates the consistency of the weld profile. Fluctuations in these process variables modify the fillet root geometry, resulting in inconsistent mechanical strength across a production run. To secure high yield, automated inspection systems scan the joint profile immediately after welding.
Mechanical Failure
Severe vibrations can initiate cracks if the root transition is too abrupt. This failure leads to high contact resistance and thermal runaway risks in the pack.