The Kolsky (Split Hopkinson) Bar has become a well-known and established experimental technique for characterizing the mechanical behavior of materials subjected to dynamic loading conditions. Kolsky bar based experimental techniques facilitate the application of controlled and repeatable dynamic loading conditions to a specimen as well as the high resolution measurement of the resulting mechanical response. In recent decades the technique has been refined and adapted to provide more complex dynamic stress-states beyond uniaxial compression. However, the increasing complexity of the experimental apparatus introduces uncertainty to the traditional specimen deformation measurement techniques.
In this thesis, a direct non-contact optical measurement technique is introduced to significantly improve the resolution of specimen deformation measurements. This novel technique, known as a splitting beam laser occlusive extensometer, is capable of measuring the displacement of both specimen ends with independent and tunable resolutions. This technique provides specimen deformation measurements with accuracy and precision superior to that of traditional methods used in Kolsky bar experiments. The relatively low cost and simplicity of this system make it a desirable alternative to other non-contact direct measurement techniques.
The proposed technique is then further expanded upon with the addition of a third measurement channel. The third channel is specifically introduced to measure the small displacements characteristic of a material undergoing elastic deformation, without sacrificing the measurement range required to capture the relatively large plastic deformations observed in ductile materials
The proposed techniques are demonstrated and validated using dynamic tensile test of common metallic materials with well-known properties. Additionally, these experimental results are used to investigate the accuracy of traditional deformation measurement techniques used in Kolsky tension bar experiments.
Number of Pages
Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial 4.0 License
Loeffler, Colin, "A Novel Splitting Beam Laser Extensometer Technique for Kolsky Tension Bar Systems" (2018). Mechanical Engineering Research Theses and Dissertations. 13.