Successful development, evaluation, and qualification of propulsion systems such as turbojet and turbofan engines and rocket motors require the measurement of the performance and reliability of these systems. Thrust stands or testers are instruments for solid and liquid motors test. These apparatuses extract the characteristics of motors such as temperature, pressure, force and torque. In this paper, the dynamic design principles of a typical thrust stand have been detailed and methods to improve dynamic response have been developed. A thrust stand should be affected by random vibrations of solid motors as slightly as possible during firing. At first some Power Spectral Density (PSD) of three kinds of solid motors has been calculated by MATLAB codes. Then a number of tester structures by Solidworks have been designed and their dynamic responses have been determined by ANSYS codes. An attempt has been made to improve dynamic responses through changing the structure. Results showed that just some models could be improved. Increase of natural frequencies protects the structure from motors random vibrations. Truss structure is a good choice for testers. Decrease of mass, using different types of tube sections and short members are effective methods for improving dynamic responses. پرونده مقاله

Successful development, evaluation, and qualification of propulsion systems such as turbojet and turbofan engines and rocket motors require the measurement of the performance and reliability of these systems. Thrust stands or testers are instruments for solid and liquid motors test. In this paper, a method for calculating of solid motors random vibrations effects on a thrust stand structure is developed. At first some Power Spectral Density (PSD) of three kinds of solid motors has been calculated by MATLAB codes. Then a typical thrust stand which has been designed based on special dynamics principles, has been modeled in Solidworks and transferred to ANSYS. In ANSYS, the structure has been analyzed modal and spectral. Then each motor's PSD has been applied on structure separately and maximum stress has been determined by ANSYS codes. Fallowed by structure fatigue life has been estimated by a formula derived from compound of Miner's cumulative fatigue damage ratio equation and Gaussian distribution curve. Results showed amount of PSD at first frequencies has more effect on structure fatigue life and just based on maximum motor thrust can not come to a definite conclusion about the vibrations effects. پرونده مقاله