Date of Award

4-3-2024

Publication Type

Thesis

Degree Name

M.A.Sc.

Department

Mechanical, Automotive, and Materials Engineering

Keywords

Digital Image Correlation;Dual Phase Steel;Formability;Microhardness;Sheared Edge

Supervisor

Daniel Green

Supervisor

Randy Bowers

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

Abstract

The sheared edge formability of DP980 steel was examined through mechanical analysis at different wear conditions of D2 tool steel trimming dies. Tensile and microhardness testing were conducted to quantify the effects of die wear on the mechanical properties at the sheared edge. A half dog-bone shaped tensile specimen allowed for separate testing of both the part side and the scrap side of the sheared sheet. Based on the tensile strength and elongation results observed in the first 80,000 trimming cycles, the effect of die wear does not significantly influence the sheared-edge formability of the part edge. These tested specimens exhibited a predominantly ductile failure mode; few brittle characteristics were noted at the sheared edge. A transitional fracture mode and lower total elongation occurred when testing the scrap edge of the trimmed specimens. This difference was attributed to the geometric differences between the part and scrap edges of the trimmed specimens, with the scrap edge exhibiting a significant burr associated with the end of the shearing process. For all tested specimens, the microhardness values measured at the sheared edge increased to a maximum at the transition point where the burnish and fracture zones meet. At more severe die wear conditions, this maximum value remained at this transition point both at and away from the sheared surface. At less severe wear conditions (fewer trim cycles), the highest hardness remained at the transition point near the sheared surface; however, peak values measured away from the sheared surface shifted closer to the top surface of the sheared specimen. Consistent peak hardness values were measured over the range of die wear conditions tested. It is concluded that manufacturers can rely on the consistent formability of the sheared edge of trimmed DP980 steel parts when using D2 tool steel dies up to 80,000 trimming cycles.

Download

Share

COinS