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Investigation of Formability and Fracture in Advanced Metal Forming Process - Bulk Forging and Sheet Metal Forming

Yang, Xi
http://rave.ohiolink.edu/etdc/view?acc_num=osu1403889605

Abstract Details

2014, Doctor of Philosophy, Ohio State University, Mechanical Engineering.
The dissertation focuses on fracture induced formability in advanced metal forming techniques. The purpose of this study is to fundamentally understand the fracture mechanics in metal forming processes and propose innovative alternative/optimized solutions to produce high quality part without fracture. The dissertation is divided into two major parts: bulk forging and sheet metal forming In bulk forging part, three case studies were presented: 1. Precision forging of engine valves: the complete valve forging process (extrusion and coining) was investigated and the cracking at the “blade” area of the valve was predicted by Finite Element Simulations. Modified tooling design was proposed to reduce the cracking in forging. 2. Open die forging: comprehensive literature survey was conducted to explore the forming conditions that could influence part quality in open die forging. 3D FE simulation was conducted in order to emulate the actual forging process. Initial billet temperature was concluded to be the major factor to cause fracture. Adjustment of the initial temperature is one of the solutions to avoid fracture. 3. Bi-metal forging: an innovative gear forging concept for lightweight vehicle design was proposed and the forging process was validated by Finite Element simulations. Bi-metallic billet was designed and manufactured for test purpose. A new approach of utilizing induction heating method was studied and adopted to heat up the billet to achieve the required temperature gradients. Closed forging die design with special modification to prevent cracking was developed in the actual forging experiment to forge “pancake” shape parts. In sheet metal forming, the results of investigation on blanking and hole flanging of Advanced High Strength Steel (AHSS) were presented: 1. Blanking: the physical nature of blanking operation and the characters of a blanked edge were thoroughly investigated, using FEM and comparison of results with published data. The factors that influence that part quality including punch-die clearance, punch shape, punch and die corner radii were evaluated. Optimization of blanking conditions to provide better edge quality and enhanced tool life was proposed. 2. Hole flanging: issues and problems of the existing industrial standard that cause the un-reliable experimental results were investigated. Finite Element simulations were conducted to predict hole expansion ratio with a suitable selection of fracture criterion (empirical and theoretical). The correlation of blanking and hole flanging was investigated to study the influence of blanking operation on hole expansion ratio. A new hole flanging tooling design was proposed to provide robust experimental results.
Taylan Altan (Advisor)
Blaine Lilly (Committee Co-Chair)
Jerald Brevick (Committee Member)
Allen Yi (Committee Member)
280 p.
Mechanical Engineering
Forging, sheet metal forming, blanking, hole flanging, fracture

Recommended Citations

Citations

  • Yang, X. (2014). Investigation of Formability and Fracture in Advanced Metal Forming Process - Bulk Forging and Sheet Metal Forming [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1403889605

    APA Style (7th edition)

  • Yang, Xi. Investigation of Formability and Fracture in Advanced Metal Forming Process - Bulk Forging and Sheet Metal Forming . 2014. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1403889605.

    MLA Style (8th edition)

  • Yang, Xi. "Investigation of Formability and Fracture in Advanced Metal Forming Process - Bulk Forging and Sheet Metal Forming ." Doctoral dissertation, Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1403889605

    Chicago Manual of Style (17th edition)

osu1403889605
562
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This open access ETD is published by The Ohio State University and OhioLINK.