There are a few kinds of structures that are created to fill in as a system, for example, springs, torsion bars, and axles, among others. They are structures, since they comprise of one single body, with no movement joints, however, with degrees of freedom, allowed by the mechanical compliance of the body. This aspect is extremely difficult to represent in durability assessment, since these structures-mechanisms are highly sensitive to dynamic effect of the system and the traditional method to predict fatigue (load history) is static and does not consider how the structure responds dynamically to the loading. In this chapter, we will study the fatigue behavior of two generic components, a classical structure and a structure-mechanism, using three different methods of calculation: load history (static), transient modal superposition (dynamic), and frequency domain modal superposition (dynamic). The objective is to demonstrate the differences between each calculation methodology due to the different ways each considers the dynamic effect.
Part of the book: Strength of Materials