Applying SYMOS Numerical Simulation to the Selection of Wire Rope Isolators for the Medium Weight Shock Machine Test

摘要

COTS electronic equipment for Navy shipboard installation often require shock isolation protection in order to survive the Navy Medium Weight shock machine test as defined in MIL-STD-901. Wire rope mounts are a common type of isolator used in such an application. However, their non linearity together with the complexity of the shock machine make a proper selection of mounts for low g's response difficult and confusing. Attempts to use the acceleration history measured on the machine table as an input have often proved unreliable, so that Socitec and Shock-Tech have developed a global numerical model using a multi-body non linear computer program. The combination of machine, isolators and Cots equipment is modeled as four rigid bodies with non linear stiffness and damping coefficient. The simulation program is known as SYMOS. Its use provides a straight forward shock analysis that takes the machine parameters into account and allows for the direct evaluation of candidate isolators by changing only a few key variables, just as if the real test was actually implemented. Test results versus analytical model are reviewed and a type of cable isolator is described. This paper is an extension of an earlier technical paper entitled Navy Shock Machine Calibration by using Numerical Simulation published at the 1995 SV Symposium in San Diego.