مهندسی مکانیک شریف (Nov 2017)
INVESTIGATION OF FRACTURE ON FLEXIBLE ROLL FORMING PROCESS USING DUCTILE FRACTURE CRITERIA AND FLD CRITERION
Abstract
Using cold roll forming process can only produce profiles with constant cross-sections.While industries, such as automotive and construction, require profiles with variable cross sections.High costs and dimensional limitation of these products by production methods with limited flexibility, such as incremental forming, deep drawing, and hydroforming, led to the idea of using roll-forming process to produce these components discussed. That is the famous the process of forming parts with variable cross-sections or flexible roll forming process.This process has some defects like other forming processes that are causing unexpected forms. The main defects of this process are web warping, the deviation from the desired edge position, edge wrinkling, fracture at bending edges, longitudinal deflection. One of the main defects in this process is the fracture phenomenon. The fracture is observed on the bending edges at transition zone in which sheet thickness is largely compared to the bending radius. In this research, the fracture phenomenon was investigated on flexible roll forming process of channel section using ductile fracture criteria and FLD criterion. For this purpose, finite element simulation of the process was done using Abaqus software.The fracture defect in this process was investigated using six ductile fracture criteria and FLD criterion. Then, experimental tests were performed using flexible roll forming machine made in Shahid Rajaee Teacher Training University. By comparing simulation results with experimental results, numerical results were validated. In addition, by comparing the results of ductile fracture criteria and FLD criterion with experimental results, the Argon ductile fracture criteria were chosen as the most appropriate criteria to predict fracture. Also, the effects of parameters were studied as sheet thickness, bending radius, and bending angle on fracture with argon as the selected criterion. The investigation results showed that by increasing the sheet thickness, bending angle increases the risk of fracture defects in the product; by increasing bending radius, the risk of fracture defects in the product decreases.
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