Volume 32, Issue 5 (September 2004)
Combining a Fatigue Model With a Shock Response Spectrum Algorithm
Product fragility assessment in packaging is described using a Damage Boundary Curve (DBC), which evaluates the velocity change and deceleration of an input shock for its damage potential to a product. The DBC assumes a brittle characteristic of components. A more realistic model is to assume ductility of components, resulting in something called Fatigue Damage Boundary (FDB) curves, which incorporate not only velocity change and deceleration, but also number of cycles to failure. The purpose of this study was to incorporate a mathematical model that accounts for the ductile nature of many products into a Shock Response Spectrum (SRS) algorithm. The advantage of incorporating SRS with a fatigue model is the ability to use any shock pulse shape to generate FDB curves and to use any shock pulse shape for finding material properties of a component in question. Using any shape shock pulse eliminates the dependency on traditional shock tables (half-sine and trapezoidal shock pulse shapes). Software was developed to demonstrate the new SRS-fatigue algorithm and to verify its applicability.