Determination of the Forming Limit Strain of Sheet Metals by the Time-dependent Method

시간의존법에 의한 금속판재 성형한계변형률의 결정

Kim, S.G.;Oh, T.H.;Kim, J.D.;Kim, H.J.

  • Received : 2015.06.29
  • Accepted : 2015.08.31
  • Published : 2015.10.01


The forming limit diagram (FLD) is the most commonly used tool for evaluating of sheet metal formability in the manufacturing field as well as the finite element analysis (FEA)-based design process. Determination of the forming limits is considerably influenced by testing/measuring machines, techniques and conditions. These influences may cause a large scatter in FLD from laboratory to laboratory. Scatter is especially true when the ‘position-dependent method’, as is specified in most national and international standards, is used. In the current study a new ‘time-dependent method’ is proposed, which is to determine the forming limit strains more accurately and reasonably when producing a FLD from experimental data. This method is based on continual strain measurement during the test. The results are compared to those from the existing standardized methods.


Time-dependent Method;ISO 12004-2;Forming Limit Strain;Forming Limit Diagram;Nakajima Test