Tension split Hopkinson bar tensile testing

• Main Author: Soo, Aaron Cai Liang
• Other Authors: Shu Dong Wei, David
• Format: Final Year Project
• Language: English
• Published: 2019
• Subjects: Engineering::Mechanical engineering
• Online Access: http://hdl.handle.net/10356/78730
• Institution: Nanyang Technological University

This Split Hopkinson Pressure Bar (SHPB) is an experimental technique used to measure the stress and strain of a material under dynamic condition. The difference from Static Tests is that SHPB involves deformation at high strain rates ranging from 1,000s-1 to 10,000s-1. In NTU School of Mechanical and Aerospace Engineering, there are three types of SHPB technique used, which generates dynamic loads through compression, tension, and torsion. The theory of SHPB is based on generating longitudinal stress waves which propagates along the experimental set up which is made up of elastic steel bars made of stainless steel 304. To measure the generated stress during the experiment, strain gauges are mounted on the incident bar and transmitted bar at 0.5m away from the individual bar ends. The strain gauges are connected to a wheatstone bridge, followed by a strain meter, which converts data collected from the experiment to voltage form, which is then displayed on a Yokogawa oscilloscope. With the data of the incident, reflected, and transmitted from the oscilloscope, the stress, strain, and strain rate can be calculated and analysed. The aim of this project is to ensure the accuracy, reliability and repeatability of the SHPB experimental set up in NTU. The striker bar velocity was measured and compared with the velocity obtained from Finite Element Method (FEM) Analysis. Several calibrations run and bar apart tests were also carried out to determine and ensure the percentage error is below 10%. After calibration, tests were carried out on specimens with different geometries. With the data obtained, results were acquired and compared with the results from past researchers. At the end of this report, problems encountered and possible experimental errors will be discussed, and solutions will be recommended to further improve the current experiment set up.