Prismatic Cell Enclosure Mechanical Stress Distribution under Solid-State Anode Expansion
Prismatic solid-state cell enclosures demand module preloads between 2 and 8 MPa with flexible interlayers to control wall deflection and dendrites.
Laser Weld Shear Stress
Meaning
Internal force per unit area acting parallel to the fused interface of a laser-welded joint determines the mechanical strength of electrical connections in battery modules. Monitoring laser weld shear stress is critical because the thin aluminum and copper busbars are subjected to vibrations during vehicle operation. These joints must maintain low electrical resistance while resisting mechanical strain.
Load Condition
Thermal expansion and contraction of cells during high-power charging create significant shear forces across the joint. If laser weld shear stress rises too high, the resulting strain can lead to micro-cracking at the edge of the weld pool. The distribution of this stress depends on the penetration depth and width of the weld seam.
Structural Failure
Mechanical separation of the busbar from the cell terminal occurs when the joint is subjected to loads that exceed the shear strength of the metal alloy. When laser weld shear stress causes a complete or partial fracture, the contact resistance across the terminal spikes immediately, generating localized hot spots during current flow. This heating can melt adjacent plastic insulation or trigger a thermal event in the connected cell, and it can also cause the battery management system to shut down due to voltage sensing errors.
Evaluation Process
Lap shear tests pull welded specimens apart to measure the force required to break the joint. This test determines the maximum laser weld shear stress the weld can withstand.