Loading...

Determination of Forming Limit Diagram with Existence of Normal Stress and Investigation on the Methods of Calibration in this Diagram

Khakpour Nejad Khaki, Hamid | 2009

657 Viewed
  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 40098 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Assempour, Ahmad
  7. Abstract:
  8. Theoretical studies in the analysis of sheet metal failures are referred to obtain the Forming Limit Diagrams (FLDs). Since extracting the Forming Limit Diagrams experimentally is cost and time consuming, many researches have been accomplished for obtaining these diagrams theoretically. However, in many of these researches, the assumption of plane stress state has been used to obtain the FLD, which is not correct in some processes such as hydroforming because of high level of normal stress. In this study, determination of the forming limit diagram with existence of the normal stress is based on the Marciniak and Kuczynski model. Newton-Raphson method has been used to find the set of variables. The structure of FLD prediction algorithm is in a way that it is possible to apply Von Mises and Hill48 yield criterions and different hardening laws. The results show that existence of the normal stress shifts up the forming limit diagram. The increase of limit strain in plane strain state ( ) has been investigated quantitatively for better understanding of this effect. Also, the effects of work hardening coefficient, strain rate sensitivity and normal anisotropy have been studied on the FLD. In M-K model, using the groove zone thickness to safe zone thickness ratio, instead of sheet thickness, is a week point. In this study, to overcome this problem, some available methods have been reviewed and the best of them has been selected and introduced with regard to the limitations, accuracy and application of them.

  9. Keywords:
  10. Forming Limit Diagram (FLD) ; Marciniak-Kuczynski Model ; Numerical Method ; Normal Stress ; Sheet Thickness

 Digital Object List

  • محتواي پايان نامه
  •   view

 Bookmark

No TOC