A comparative study on the fatigue life of the vehicle body spot welds using different numerical techniques: Inertia relief and Modal dynamic analyses

Abstract

Owing to the expensive and time-consuming nature of durability experiments, finite element based durability analysis is quite prevalent in the automotive industry. Numerical fatigue life analyses are typically divided into two different categories, the quasi-static methods which are faster and the dynamic methods which are more accurate. The aim of this paper is to compare the inertia relief and modal dynamic approaches in terms of formulation, accuracy and computation time. The chosen case study is the fatigue life of the vehicle body which is considered the main load-bearing component in a vehicle. By utilizing multi-body dynamics model and driving the vehicle on different standardized roads and by different velocities, the loadings, which act on the body are calculated and later used for the stress analysis. Then, by using the structural stress method, the fatigue life of the vehicle spot welds is calculated and the results are compared for both approaches. The findings reveal that the modal dynamic method is almost 37 times more time-consuming than the inertia relief approach, but if accuracy is desired, it can be up to 96% more accurate. Also as predicted, at low frequency loading, there is no major difference between the results of both methods.

Keywords

• body-in-white
• inertia relief
• modal dynamic
• spot weld
• structural stress method