MEASUREMENT OF DYNAMIC RESPONSE OF SS316 UNDER HIGH STRAIN RATE LOADING

Abstract

The paper discusses the experimental methods and techniques to measure the dynamic response of austenitic stainless steel SS316 subjected to the intense shock load of high explosive. The strains experienced by the material are transient in nature and last for a fraction of second with peak strain value of 15%. For experimentation, the cylindrical structures of austenitic stainless steel SS316 in various diameter 200mm-400mm, height 200mm-800mm & thickness 1-1.2mm were arranged by IGCAR . These cylinders were filled with water and rigidly held from both ends in a counter weight foundation. The experiments were conducted by detonating the explosive charge at the center of these water filled cylinders. The quantity of explosive used in trials varies from 4grams to 50grams. The response of the cylindrical structure under intense load of high explosive charge was measured by using post yield strain gages having strain limit of 15 %. The TML make post yield strain gauges model No.YFLA-10 were pasted on the cylinder in axial and shear directions to measure the dynamic axial and hoop strains. The strain gauges used were made of constantan material having 120Ω resistance, 10mm length and gauge factor of 2.1. These gauges were pasted on the cylindrical structure with the help of cynoacrylite (CN). As the strain generated in the material under explosive load is dynamic in nature, so TML make modular high bandwidth amplifier each having bandwidth of 200khz were used to condition the outputs of strain gauges. The conditioned outputs from strain gauges were recorded using data acquisition system having bandwidth greater than 200 kHz. High speed photography has also been used to capture the transient deformation of the cylimderical structure during the detonation.. The acquired strain data in instrumented trials has been used in determining the strain limit of austenitic stainless steel SS316 under high strain rate in explosive environment.