Application of the Hough Transform for Automated Analysis of Kolsky Bar Data

Abstract

The Kolsky Bar, also known as the split-Hopkinson pressure bar, has become one of the most commonly used apparatuses when studying the dynamic behavior of materials. Despite its popularity, limited standards exists with respect to the design, data collection, and data analysis approach used. A lack of standardization can lead to lab-to-lab variation in reported dynamic behavior for nominally identical materials. A key step during data reduction is the appropriate selection of the signal windows used in the one-dimensional wave propagation analysis of recorded strain gauge signals. The presented work provides an automated analysis approach for selecting signal windows based on the Hough transform. The approach is agnostic to loading mode (e.g., tension vs. compression), applicable to both pulse-shaped and non-pulse shaped experiments, robust in the presence of naturally occurring signal oscillations and noise, and has rapid computation time. Two cases are selected to demonstrate the viability of applying the Hough transform to recorded Kolsky bar signals. In the first case, the bar wave speeds of maraging steel tension and compression Kolsky bars are determined. The second case demonstrates the application of the Hough transform technique in the study of the dynamic compression behavior of additively manufactured Inconel 718. A stress-strain curve generated using the automated HT-based technique is compared to those determined manually showing the automated approach provides a closely matching result. Window selection automation provides an important step toward improving consistency of results reported, data processing throughput, and traceability of dynamic mechanical property data generation.