Fri, Mar 12, 2021 @ 03:00 PM - 04:00 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Speaker: Samuel Goldman, USC AME PhD Student
Talk Title: A Case Study of the Failure of a Compression Spring in a Lunar Percussion Mechanism
Abstract: The Regolith and Ice Drill for the Exploration of New Terrains (TRIDENT) is a rotary-percussive drill being used on several upcoming Lunar exploration programs. Life testing of this drill resulted in the unexpected early failure of a critical compression spring, which cannot be explained by quasi-static analysis. The purpose of this work is to determine if transient dynamic behavior resulting from percussion can explain this failure. An experiment is conducted comparing the effect of various types of spacers, and it is found that a neoprene spacer allows the spring to survive more than twice as many cycles compared to metallic spacers. Additionally, the dynamic response of this system to impact is modeled using the Distributed Transfer Function Method (DTFM), and is compared to FEA and discrete element techniques. It is found that DTFM is capable of bounding the response as computed by FEA, while the discrete element model underestimates peak shear stress by more than 25% in boundary coils. FEA and DTFM both show that wave propagation within the spring could result in peak shear stresses in boundary coils that are over 20% higher than middle coils. These results suggest that percussive wave propagation can explain the early failure of this spring.
Biography: Sam Goldman is a Ph.D. student under Dr. Flashner. His research focus is primarily in modeling and experimentation of percussion mechanisms used in extraterrestrial geotechnical tools. Sam has a B.S. in Biomedical Engineering from The Ohio State University, and an M.S. in Aerospace & Mechanical Engineering from USC.
Host: AME Department
More Info: https://usc.zoom.us/s/96549200347
Audiences: Everyone Is Invited
Posted By: Christine Franks