Showing 4 results for Forming Limit Curve
Parviz Kahhal, , ,
Volume 13, Issue 9 (12-2013)
Abstract
Present study describes the approach of applying Response Surface Methodology (RSM) with a Pareto-based multi-objective genetic algorithm to assist engineers in optimization of sheet metal forming. In many studies, Finite element analysis and optimization technique have been integrated to solve the optimal process parameters of sheet metal forming by transforming multi objective problem into a single-objective problem. This paper aims to minimize the objective functions of fracture and wrinkle simultaneously. Design variables are blank-holding force and draw-bead geometry (length and Diameter). Response surface model has been used for design of experiment and finding relationships between variables and objective functions. Forming Limit Curve (FLC) has been used to define the objective functions. Finite element analysis applied for simulating the forming process. Proposed approach has been investigated on a cross-shaped cup drawing case and it has been observed that it is more effective and accurate than traditional finite element analysis methods and the ‘trial and error’ procedure.
Mir Emad Hosseini, Seyed Jamal Hosseinipour, Mohammad Bakhshi Jooybari,
Volume 15, Issue 11 (1-2016)
Abstract
A Forming Limit Diagram (FLD) is a graph which depicts the major strains versus values of the minor strains at the onset of localized necking. Experimental determination of a FLD is usually very time consuming and requires special equipment. Many analytical and numerical models have been developed to overcome these difficulties. The Gurson- Tvergaard- Needlemann (GTN) damage model is a micromechanical model for ductile fracture. This model describes the damage evolution in the microstructure with physical equations, so that crack initiation due to mechanical loading can be predicted. In this work by using the GTN damage model, a failure criterion based on void evolution was examined. The aim is to derive constitutive equations from Gurson's plastic potential function in order to predict the plastic deformation and failure of sheet metals. These equations have been solved by analytical approach. The Forming Limit Diagrams of some alloys which studied in the literatures have been predicted using MATLAB software. The results of analytical approach have been compared with experimental and numerical results of some other researchers and showed good agreement. The effects of GTN model parameters including 〖 f〗_0 〖,f〗_C 〖,f〗_N,f_f , as well as anisotropy coefficient and strain hardening exponent on the FLD and the growth procedure of void volume fraction have been investigated analytically.
Maryam Geran Gharakheyli, Hamid Gorji, Mohammad Bakhshi, Mohammad Javad Mirnia,
Volume 17, Issue 6 (8-2017)
Abstract
Tube hydroforming is a process which is considered to produce integrated and seamless parts in recent years. The numerical prediction of tearing to design the right equipment in this process is important. In this study, the formability of 304 stainless steel tube by free bulge test was experimentally and numerically evaluated to determine the forming limit diagram. The Gurson- Tvergaard- Needleman (GTN) is a micromechanical model to predict ductile fracture of metals. In order to determine the defining parameters of the GTN damage model, the experimental tensile test of the standard sample and the finite element simulation using ABAQUS software was performed. Using this criterion in the ABAQUS software and comparing the force-displacement diagram obtained from the experimental tensile test and the finite element simulation, the parameters of the GTN model was obtained by the inverse method. Then, the geometrical parameters of the die in the free bulge hydroforming process were investigated by the GTN ductile fracture criterion and the forming limit diagram of the 304 stainless steel tube was numerically obtained. The experimental tests were also carried out to verify the results of the finite element simulation. It’s shown an acceptable agreement
Ahmad Amini, َََali Alavi Nia,
Volume 23, Issue 6 (5-2023)
Abstract
Considering the increasing use of high-speed presses, such as high-speed servo presses, in the automotive industry, it seems necessary to investigate the formability of sheet metals in this range of forming speed. Therefore, this study has been conducted to investigate the effect of medium strain rate forming on the formability of the St14 steel sheet. Tensile tests were done at various strain rates, and formability tests were performed to create forming limit curves at the quasi-static and impact forming. Finite element simulation was used to extract the numerical forming limit curves. The material model was entered into the simulation by considering the strain rate effect using the VUHARD subroutine. The results of tensile tests showed that some influential strain-hardening indicators reduce with strain rate enhancement. Also, using the material model, the tensile behavior was predicted with good accuracy at each strain rate. In impact forming, fracture and strain concentration was transferred to the dome center, and the dome height in biaxial stretching was reduced by 17.1% compared to quasi-static forming due to the variation of frictional conditions. The forming limit curve of impact forming was shifted to the lower values and right side of the forming limit diagram compared to quasi-static forming. In impact forming, the forming limit in plane-strain condition was reduced by 8.1% compared to quasi-static forming. Also, the simulation results, including fracture position, forming limit curve, and dome height in both forming processes, were in good agreement with the experimental results.
