Theses and Dissertations

Issuing Body

Mississippi State University

Advisor

Horstemeyer, Mark F.

Committee Member

Oppedal, Andrew L.

Committee Member

Kennan Crane, Kennan Charles.

Committee Member

Rhee, Hongjoo.

Date of Degree

5-6-2017

Document Type

Dissertation - Open Access

Major

Mechanical Engineering

Degree Name

Doctor of Philosophy

College

James Worth Bagley College of Engineering

Department

Department of Mechanical Engineering

Abstract

An investigation of the microstructure-mechanical property relationships for gray cast iron and a vintage ASTM A7 steel are presented herein. Gray cast iron was shown to have a moderate sensitivity to strain rate and a large disparity in behavior between compression, tension, and torsion. ASTM A7 steel was shown to behave in a more complex manor with the strain rate sensitivity having a negative relationship in tension and positive relationship in compression and torsion, the tensile stress-state producing the highest stress response, and the material producing a higher stress response when exposed to elevated temperatures. The counterintuitive behavior observed in A7 steel was attributed to dynamic strain aging. The Mississippi State University Internal State Variable Plasticity-Damage model was updated to accurately capture negative strain rate sensitivity and DSA embrittlement by developing kinematic, thermodynamic, and kinetic constitutive relationships for dynamic strain aging. A parametric study was performed to elucidate the behavior of the new internal state variable for dynamic strain aging. Gray cast iron was successfully calibrated to a pre-DSA version of the plasticity-damage model and A7 steel was successfully calibrated to the updated plasticity-damage model.

URI

https://hdl.handle.net/11668/16589

Comments

torsion||tension||High strain rate||Gray cast iron||ASTM A7 steel||stress-state||dynamic strain aging||structure-property||negative strain rate sensitivity||stress-strain||internal state variables||plasticity||constitutive model||damage||compression

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