Theses and Dissertations
ORCID
https://orcid.org/0009-0003-8271-1323
Advisor
Whittington, Wilburn
Committee Member
Smith, Aaron
Committee Member
Hammi, Youssef
Committee Member
Rhee, Hongjoo
Date of Degree
5-10-2024
Original embargo terms
Embargo 2 years
Document Type
Dissertation - Open Access
Major
Mechanical Engineering
Degree Name
Doctor of Philosophy (Ph.D)
College
James Worth Bagley College of Engineering
Department
Department of Mechanical Engineering
Abstract
This work investigates the interactions between impact devices and material response in the realm of solid mechanics, utilizing explicit finite element analysis and experimental methods based on the split-hopkinson pressure bar. It focuses on understanding how tools like jackhammers use hammer strikes to generate pressure waves, then the wave is transferred through a chisel to materials such as rocks to cause fracture. The interaction between the wave and the rock is complex. Under dynamic loading the mechanical response of materials changes and significant losses occur due to reflections and inefficient pressure states. This research explores how chisel geometry can be optimized to control critical parameters influencing rock fracture, including stress state, pulse length, and peak pressure. The use of notches to influence the stress state, periodic boundaries to influence the pulse length and pressure amplification in tapers the increase the pressure showed an improvement in efficiency in jackhammers. Additionally, this work extends insights of the concept of pressure amplification in solids, to liquids inside tapered pipes, enhancing the understanding of phenomena like pulse pressure amplification in arteries and water hammer effects in piping systems. Two innovative contributions emerge from this work: a novel amplifier design for water cannons, improving these machines efficiency and showing promise for applications in water jet cutting and drilling, and a novel process for extruding nanocrystalline magnesium. This process leverages pressure amplification and impact-induced plastic shear deformations to refine crystal size, offering a new avenue for producing various nanocrystalline materials.
Recommended Citation
Jarachi, Marouane, "Effect of pressure on viscoplasticity and its usefulness in designing impact devices" (2024). Theses and Dissertations. 6127.
https://scholarsjunction.msstate.edu/td/6127