Date of Award

Summer 2019

Project Type

Thesis

Program or Major

Mechanical Engineering

Degree Name

Master of Science

First Advisor

Marko Knezevic

Second Advisor

Brad L Kinsey

Third Advisor

Todd S Gross

Abstract

The following research explores the continuous bending under tension (CBT) incremental forming process effects on four dual phase (DP) steels: DP 590, DP 780, DP 980, DP 1180. A parameter study was conducted, finding the ideal parameters for increased elongation to fracture compared to tension of over five times for DP 1180 and DP 980. These parameters were found to be a normalized bend depth of 3.5 and a crosshead pull speed of 1.35mm/s. Using these parameters, following tests were conducted on all four steels by stopping the CBT process before fracture at 2, 4, 6, 8, and some even at 10 and 12 CBT cycles. Smaller tensile specimens were machine from these CBT processed strips and uniaxial tension tests were performed to study the residual ductility of CBT testing. The strength of all steels increased with increased cycle count by 200-400 MPa, however the ductility decreased by over half. Using neutron diffraction, the texture evolution of the CBT process was explored. Results showed a preferred orientation in the {011} fiber in the pulling direction. This research also proves simulating the CBT process and matching to experimental data can be a method for extrapolating post-necking hardening behavior of DP 980 and DP 1180. The experimental data and results are further explained in the following chapters.

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