Meaning
Time dependent reduction in mechanical stress occurs when a material is held at a constant deformation. This strain relaxation is particularly relevant for the polymers and adhesives used to secure battery cells and busbars. It can lead to the loosening of mechanical joints and the loss of electrical contact over several years of service.
Elastic Recovery
Initially, a compressed foam pad or a tightened bolt stores energy that pushes back against the load. Over time, strain relaxation causes the material to reorganize at a molecular level, reducing this resistive force. This change means that the initial pressure applied during assembly will not be the same as the pressure ten years later.
Creep Analysis
Testing materials at elevated temperatures accelerates the rate of physical change to simulate long term behavior. Understanding strain relaxation allows designers to choose materials that maintain their properties throughout the life of the battery. This data informs the selection of metals for springs and elastomers for gaskets.
Longterm Stability
If the tension in a connector drops too low, the electrical resistance will increase. Accounting for strain relaxation in the initial torque specification ensures that the assembly remains tight even after the material has softened. This planning prevents overheating and intermittent failures in high vibration environments.
