A Dynamic Durability Analysis Method and Application to a Battery Support Subsystem

The battery support in a small car is an example of a subsystem that lends itself to mounted component dynamic fatigue analysis, due to its weight and localized attachments. This paper describes a durability analysis method that was developed to define the required enforced motion, stress response, and fatigue life for such subsystems. The method combines the large mass method with the modal transient formulation to determine the dynamic stress responses. The large mass method was selected over others for its ease of use and efficiency when working with the modal formulation and known accelerations from a single driving point. In this example, these known accelerations were obtained from the drive files of a 4-DOF shake table that was used for corresponding lab tests of a rear compartment body structure. These drive files, originally displacements, were differentiated twice and filtered to produce prescribed accelerations to the finite element model. The resulting responses from the model correlated well with measured data and the technique was applied with confidence in resolving a durability issue during prototype development of the battery support. Issues such as data recovery settings, resultant file sizes, and the use of alternative solver machines (parallel desktops vs high performance mainframe) are discussed.