Loading...

The comparison of M-K and GTN models in prediction of forming limit diagrams

Soleimanifard, Ali | 2014

393 Viewed
  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 46215 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Assempour, Ahmad
  7. Abstract:
  8. Knowing the magnitude of the maximum strain before necking is of utmost importance in the processes of designing sheet metals. Thus, numerous experimental and theoretical efforts have been done to answer these questions. In order to predict allowed strains in biaxial stretching, an experimental diagram was introduced called “Forming Limit Diagram” in which major strain is plotted versus minor strain and if the corresponding point to the strain on the sheet is higher than this diagram, necking will occur. One of the most popular methods of obtaining forming limit diagrams is using a hemispherical rod for shaping sheet, which is named as “Nakazima Test” and then the critical strains are obtained in the bending mode. Among the theoretical methods, M-K and GTN models can be noted which are two of the best known and most widely used methods in this field. In M-K model, it is assumed that an initial groove exists in the sheet as a flaw and since this area is weak, necking begins from there. GTN model investigates the microstructural changes of metals during plastic deformation and study of ductile fracture in metals. Ductile fracture includes: creation of micro-voids in place of impurity particles, growth of micro-voids caused by increased strain on the samples, and finally interconnection of voids and the establishment of macroscopic crack. Despite the numerous studies done on these methods, it has not been identified which of these methods can have the best and closest prediction from forming limit diagrams compared to each other in different situations. Therefore, this project attempts to compare these methods. In order to accomplish this aim, Nakazima test was used as an experimental method. Forming limit diagrams developed by M-K and GTN models were also run by finite element software, Abaqus. Finally, by a detailed comparison between diagrams obtained from both methods, the results were presented. Based on these results, it can be said that the GTN model predicts the forming limit diagrams more cautiously being compared to the M-K model
  9. Keywords:
  10. Marciniak-Kuczynski Model ; Forming Limit Diagram (FLD) ; Necking ; Gurson-Tvergaarol-Needleman (GTN)Model

 Digital Object List

 Bookmark

No TOC