Date of Award
2025
Document Type
Thesis
Degree Name
Master of Science in Engineering (MSE)
Department
Mechanical Engineering
Committee Chair
Nathan Spulak
Committee Member
Babak Shotorban
Committee Member
Robert Lowe
Research Advisor
Nathan Spulak
Subject(s)
Materials--Mechanical properties--Testing--Methods, Strains and stresses--Measurement, Constitutive model free testing
Abstract
Advances in imaging techniques allow for the determination of full-field displacements and strains during materials testing. However, most analysis techniques rely on strain gages and virtual extensometers instead of utilizing all available full-field data. Those methods that do utilize the full-field strain and displacement measurements, such as Finite Element Model Updating and the Virtual Fields Method, must also rely on a user-defined constitutive material models to relate the stresses and strains. While these methods can provide accurate full-field stresses and insights into complex material behavior in some cases, they are constrained by the fact that they require a pre-selected constitutive model. If the chosen constitutive model is ill-suited for describing the actual material behavior, the resulting stress field derived from the above analyses will be inaccurate. Therefore, the feasibility of developing a new solver method to determine full-field stresses without the use of stress vs. strain constitutive equations is investigated, through the application of basic physics principles and common-sense constraints. Different constitutive-model free solving methods are developed, and evaluated using simulated full-field displacements and strains generated from the finite element analysis software LS-DYNA as input data in order to solve for the full-field stresses. The theoretical full-field stresses from finite element analysis are then compared against the predicted stress fields from each solver to assess the accuracy and feasibility of different methods. The solver method is able to solve simple square specimens under elastic-plastic loading correctly for their full-field stresses. Additionally, it can solve for the full-field stresses of a square specimen with a varying Young’s modulus. However, specimens with more complex geometry are not able to be solved correctly. The applied physics principles and assumptions are reasonable for the complex specimens, but their implementation leads to trivial solutions.
Recommended Citation
Barnes, Joel David, "Development of a constitutive model free method to determine full-field stresses based upon fundamental physics principles" (2025). Theses. 804.
https://louis.uah.edu/uah-theses/804