Long Term Interconnect Creep and Weld Fatigue under Cyclic Thermal Load in Heavy Formats
Thermal expansion and cell swell induce cyclic shear stresses that trigger weld fatigue and interconnect creep, requiring compliance flexure loops.
Strain Concentration Factor
Meaning
Structural design parameters that quantify how localized mechanical stress increases near sharp corners or welds help predict the failure points of battery casings and terminal tabs. The strain concentration factor is a critical variable in assessing the fatigue life of cell components subjected to cyclic thermal swelling. Minimizing this factor prevents localized mechanical failures that can lead to gas leaks or electrical open circuits, thereby ensuring the long-term safety of the module.
Stress Analysis
Geometric discontinuities such as the weld joint between the terminal tab and the current collector create regions of high stress. By calculating the strain concentration factor, engineers identify where cracks are most likely to initiate under mechanical vibration. This calculation allows for the optimization of the joint geometry.
Design Optimization
Rounded corners and smooth transitions reduce the local stress peaks in the battery components. Applying a lower strain concentration factor to the design of the cell terminals increases their resistance to fatigue during transport and operation. This is especially important for heavy-duty electric vehicle applications.
Failure Investigation
During post-mortem analysis of failed cells, investigators often find that fractures occurred at points of high stress concentration. Understanding the strain concentration factor helps in redesigning the failed component to prevent a recurrence of the issue. This structural refinement is a key part of continuous product improvement.