Theses and Dissertations

Issuing Body

Mississippi State University


Lacy, Thomas E.

Committee Member

Horstemeyer, Mark F.

Committee Member

Newman, James C.

Committee Member

Cherkaoui, Mohammed

Date of Degree


Document Type

Graduate Thesis - Open Access

Degree Name

Master of Science


James Worth Bagley College of Engineering


Department of Aerospace Engineering


Mechanical structure-property relations have been quantified for AISI 4140 steel under different strain rates and temperatures. The structure-property relations were used to calibrate a microstructure-based internal state variable plasticity-damage model for monotonic tension, compression and torsion plasticity, as well as damage evolution. Strong stress state and temperature dependences were observed for the AISI 4140 steel. Tension tests on three different notched Bridgman specimens were undertaken to study the damage-triaxiality dependence for model validation purposes. Fracture surface analysis was performed using Scanning Electron Microscopy (SEM) to quantify the void nucleation and void sizes in the different specimens. The stress-strain behavior exhibited a fairly large applied stress state (tension, compression dependence, and torsion), a moderate temperature dependence, and a relatively small strain rate dependence.



Finite Element Analysis (FEA) modeling||damage.||Internal State Variable (ISV)||4140 steel