MSE Seminar: Jason Johnson, Development of the Axisymmetric Expanding Ring: A High Strain-Rate Materials Characterization Test

PhD Candidate advised by Dr. Glenn Daehn, Department of Materials Science and Engineering, The Ohio State University

Abstract

Towards the end goal of high rate tensile characterization of any material, existing ideas and newly developed technology have been combined in the form of a test platform dubbed the FIRE system. The acronym stands for Fully Instrumented Ring Expansion, a concept that is capable of evaluating the dynamic behavior of a wide range of materials in tension at strain rates well in excess of 103 s-1. At the center of the design is a collection of techniques used to impulsively drive ring shaped samples radially outward in a highly symmetric fashion. This geometry avoids many of the traditional pitfalls associated with high rate testing such as end effects and critical extension speeds. Precision velocimetry has been adapted to the system utilizing state of the art optical and electronic equipment via a subassembly known as PDV (Photon Doppler Velocimetry). The PDV capabilities at present include determination of sample velocities up to 3.2 km/s with simultaneous displacement resolution on the order of 1-10 µm. As validation of the techniques developed, numerous representative material studies were carried out and compared to established data from other sources. Results were found to be in favorable agreement, verifying the efficacy of the methods. Additionally, the expanding ring test has been applied in conjunction with sample types and actuator technologies not reported previously. This provides an expanded usefulness to the test, which has been developed to the point now of being user friendly.

Bio

My primary area of interest is advanced manufacturing techniques; my experience for the past five years here at OSU has dealt with electromagnetic and other impulse based metal forming processes. Previously at MSU I had worked in powder processing and consolidation of thermoelectric materials. I have had far more training and hands on experience in a shop than most people my age (28); manual and CNC machining, welding & brazing, woodworking and electronics. For fun I play guitar, rebuild engines, maintain cars and create wood furniture. I also enjoy hiking and camping with my wife, our dogs and our new son Maxwell.