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PREDICTION AND REDUCTION OF DEFECTS IN SHEET METAL FORMING

Fallahiarezoodar, Ali, fallahiarezoodar
http://rave.ohiolink.edu/etdc/view?acc_num=osu1523879307901727

Abstract Details

2018, Doctor of Philosophy, Ohio State University, Industrial and Systems Engineering.
Sheet metal forming is the process of forming a metal blank into a useful part. The objective is to form the part within the required tolerances without any defects. Defects in sheet metal forming appeared as tearing, necking, wrinkling, and springback. Advanced high strength steels and high strength aluminum alloys are increasingly used in the automotive industry to satisfy the demand for improved safety and increased fuel efficiency. However, high strength materials tend to exhibit low formability and high springback compared to normal mild steels. Several parameters affect the quality of the final part, including blank material, tool material, friction, lubrication, as well as process parameters such as forming speed and forming temperature. Determining of material properties and formability is required to design the tooling and manufacturing process. The common methods for determining the material properties are reviewed. The limitations of the forming limit diagram are discussed and a practical method for developing the forming limit diagram is presented. Friction and lubrication play an important role in providing high quality parts. Friction conditions depend on sheet and tool material, surface qualities, type of lubricant and process conditions such as contact pressure, sliding velocity, and temperature. Laboratory tests for evaluating deep drawing lubricants should be designed to emulate the conditions of actual forming processes. This work will compare the effectiveness of the cup draw test and twist compression test for evaluating metal stamping lubricants. Effects of contact pressure and sliding velocities on lubricant performance are evaluated. Also, numerical simulations are developed to predict the temperature increase in the part during each test. Results illustrate that testing conditions during the cup drawing test is closer to industrial deep drawing operations than twist compression test. In addition to friction and lubrication, springback affects the dimensional accuracy of stamped parts. Accurate prediction of springback is necessary in die design stage. Springback occurs after stamping and ejection of the part as result of elastic recovery of the part. To accurately predict springback through finite element analysis, the material model should be well defined for accurate simulation and prediction of stresses and strains after unloading. Despite the development of advanced material models that comprehensively describe the Bauschinger effect, transient behavior, permanent softening, and the unloading elastic modulus degradation, the prediction of springback is still not adequate for production parts. Dies are often recut several times, after the first tryouts, to compensate for springback and achieve the required part geometry. The material properties that affect the springback are studied and effect of each property is investigated. Results reveal that the E-modulus is the most important material property defining the elastic recovery of the material and springback. A methodology for determining an average E-modulus to provide accurate springback prediction is presented. The method is expanded to determine the variation of E-modulus with plastic strain to simulate the springback in real industrial part and achieve more accurate springback prediction before manufacturing a production die. Finally, effect of post-stretching method on reduction of springback is investigated both experimentally and numerically.
Taylan Altan (Advisor)
Farhang Pourboghrat (Committee Member)
Jerald Brevick (Committee Member)
153 p.
Mechanical Engineering

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Citations

  • Fallahiarezoodar, fallahiarezoodar, A. (2018). PREDICTION AND REDUCTION OF DEFECTS IN SHEET METAL FORMING [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1523879307901727

    APA Style (7th edition)

  • Fallahiarezoodar, fallahiarezoodar, Ali. PREDICTION AND REDUCTION OF DEFECTS IN SHEET METAL FORMING. 2018. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1523879307901727.

    MLA Style (8th edition)

  • Fallahiarezoodar, fallahiarezoodar, Ali. "PREDICTION AND REDUCTION OF DEFECTS IN SHEET METAL FORMING." Doctoral dissertation, Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1523879307901727

    Chicago Manual of Style (17th edition)

osu1523879307901727
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This open access ETD is published by The Ohio State University and OhioLINK.