Abstract
The construction of a forming limit diagram (FLD) is a conventional approach to obtain limit strains and to evaluate the formability of sheet metal. Appropriate necking criteria should be applied to determine the forming limit curve (FLC) accurately. In recent years, deep research on the determination of the FLC has been carried out; meanwhile, several necking criteria have been proposed. However, the application of inappropriate necking criteria would cause deviations when determining FLCs. In this study, both Marciniak and Nakajima tests were carried out on the AA5086 aluminum sheet to make a comparative investigation of different necking criteria in the determination of FLCs. In the Marciniak test, four existing necking criteria were chosen to construct FLCs, and analyzed in detail. The well-performed time dependent and position dependent methods were selected for the Nakajima test. Meanwhile, the modified Wang method based on the height change of the adjacent points was proposed. The comparative results showed that the time and position dependent methods were relatively conservative in both experiments, while the modified Wang method could identify the onset of localized necking more accurately.
Highlights
Metal sheet forming has been widely used in various industrial production processes, especially in the automotive [1,2] and aeronautic [3] fields
The results indicated that the time and position dependent method were quite similar on the left side of the forming limit curve (FLC), while a slightly higher limit strain was obtained by the time criterion, rather than the position dependent method, on the right side
Experimental Marciniak and Nakajima tests were used to study the effect of necking criteria on the determination of the FLCs for AA5086 aluminum sheet
Summary
Metal sheet forming has been widely used in various industrial production processes, especially in the automotive [1,2] and aeronautic [3] fields. A lightweight design based on metal sheet forming has become popular in industrial production. The metal formability has generally been restricted by the failure limit corresponding to the onset of localized necking. The forming limit diagram (FLD) raised by Keeler and Backofen [4] has been a common method for the evaluation of metal formability. By measuring the limit deformation of the metal sheet under different strain paths, the forming limit curve (FLC) could be constructed according to the critical major and minor strains. Afterwards, safety and failure regions are separated by the shape and location of the FLC
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
