Application of Fracture Mechanics to Specify the Proof Load Factor for Clamp Band Systems of Launch Vehicles

This article presents a methodology for evaluation of the proof load factor (PLF) for clamp band system (CBS) made of M250 Maraging steel following fracture mechanics principles.CBS is most widely used as a structural element and as a separation system. Using Taguchi’s design of experiments and the response surface method (RSM) the compact tension specimens were tested to establish an empirical relation for the failure load (P _max) in terms of the ultimate strength, width, thickness, and initial crack length. The test results of P _max closely matched with the developed RSM empirical relation. Crack growth rates of the maraging steel in different environments were examined. Fracture strength (σ_f) of center surface cracks and through-crack tension specimens are evaluated utilizing the fracture toughness (K _IC). Stress induced in merman band at flight loading conditions is evaluated to estimate the higher load factor and PLF. Statistical safety factor and reliability assessments were made for the specified flaw sizes useful in the development of fracture control plan for CBS of launch vehicles.