Study of cumulative damage to a solid rocket motor grain during highway transportation

AbstractDue to strategic requirements, tactical missiles need to be transported several times before they are launched. For this reason, this study examined the cumulative damage that occurs in a solid rocket motor grain during road transportation. Constant-stress reciprocating tensile tests of a composite solid propellant were designed and carried out, and the characteristic fatigue curve of the propellant was fitted and analyzed. By processing power spectral density data for equipment transportation tests, a vibration acceleration load spectrum for a solid rocket motor grain in the process of highway transportation was obtained. A three-dimensional finite-element calculation model of a solid rocket motor was established, and the stress response of the motor grain was simulated. After this, cyclic loads were obtained using a rainflow counting method. The cumulative damage to the solid rocket motor grain during highway transportation was calculated according to Miner’s linear cumulative-damage model and evaluated. It was concluded that during transportation, the maximum stress of the solid rocket motor is 0.2 MPa, the maximum strain is 0.03, and the maximum displacement is 19.32 mm, all of which are found in the front stress-release boot. After 4000 km driving on the highway, the damage to the front stress-release boot of the grain is thus the greatest, with a value of 0.0796. The damage to the inner hole of the grain was found to be the smallest, with a value of 0.0438.