Date of Award
2025
Document Type
Thesis
Degree Name
Master of Science in Engineering (MSE)
Department
Mechanical Engineering
Committee Chair
Nathan Spulak
Committee Member
Nicholas Ginga
Committee Member
Yooseob Song
Research Advisor
Nathan Spulak
Subject(s)
Materials--Mechanical properties--Testing, Strains and stresses--Measurement, Digital image correlation
Abstract
The rate sensitivity of materials is an important aspect to consider when designing components; such as in manufacturing processes, aerospace vehicle impacts/propulsion systems, and automobile collisions. Characterizing a material’s rate sensitivity can be expensive and time consuming due to multiple tests being necessary at each given strain-rate to fully characterize the response. This project proposes a methodology to determine the material response at multiple truly constant true strain rates from a single test using non-uniform geometry and the strain localization phenomenon. Finite element simulations using Ansys LS-DYNA are used to design potential new test specimen geometries to induce constant and numerous strain-rates across the specimen. The four most promising geometries are fabricated and tested. Digital Image Correlation (DIC) is utilized to obtain full-field data so that the area specifically around the necked region can be analyzed. Then, using an array of virtual extensometers, the instantaneous cross-sectional area is calculated for the determination of the true stress at a given point. Strain-rates across the specimen are determined with time differentiation and true stress-strain curves are generated. The data is then analyzed to determine the feasibility of inducing multiple constant strain-rates and determining the corresponding material behavior from a single test. The Virtual Fields Method (VFM) is also introduced and used in a simple case to demonstrate its capacity to identify material parameters utilizing the full-field DIC displacement and strain data.
Recommended Citation
Daignault, Derryk Lee, "Determination of material deformation at truly constant strain rates utilizing full-field stress and strain measurements" (2025). Theses. 736.
https://louis.uah.edu/uah-theses/736
