Stress Analysis of HEG Piston

Abstract

This report details finite element simulations performed on the High Enthalpy Shock Tunnel, Göttingen (HEG) piston for operation at burst pressures greater than 20 MPa. An axisymmetric finite element grid was used for all simulations. The piston body and brake pads were modelled and simulated under a number of different loading conditions. A uniform pressure of 20 MPa was applied in most cases and prospective burst pressures were determined via linear extrapolation to a safety factor of 1.0. It is recommended that a burst pressure of no more than 50 MPa be used. This equates to a safety factor of 1.5 to initial yielding for the most appropriate analysis (refined non­linear transient analysis with modified wall/brake/body contact over 20 ms). The use of a safety factor for the piston body is recommended