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Flexible roll forming is a modern process for producing profiles with changing cross section. One of the important defects in this process is the web warping of product that causes failure to obtain dimensional and geometrical tolerances. In this paper, mechanism of web warping occurrence was investigated by finite element simulation in ABAQUS/CAE software. Results of simulation indicated that inadequate longitudinal strain in the edge of profile’s flange in transition zone is the reason of profile’s web warping. Furthermore, the effect of geometric parameters of product such as flange length, bend angle, radius of transition zone and thickness on the web warping were determined. Analysis of variance showed flange length and bend angle are recognized as the most effective factors on warping of profiles with specific thickness. An equation for prediction of warping was proposed in terms of geometrical parameters of product. In order to verify the finite element model, the longitudinal strain of deformed strip edge was obtained from simulations and compared with the experimental results of other researchers. A good agreement between them confirmed the accuracy of the finite element model.

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Today, with the development of technology, industries such as automotive and construction require products with variable cross section. Multiplicity of steps, dimensional limitation and high production costs of the components caused flexible roll forming process used to produce these products. One of the main defects in this process is the fracture phenomenon. The fracture is observed on the bending edges at transition zone that sheet thickness is large compared to the bending radius. In this research the fracture phenomenon is investigated on flexible roll forming process of channel section using ductile fracture criteria. For this purpose finite element simulation of the process using Abaqus software is done. The fracture defect in this process is investigated using six ductile fracture criteria by developing a subroutine. Experimental tests are performed on 27 specimens precut sheet of AL6061-T6, using flexible roll forming machine built in Shahid Rajaee University. By comparing simulation results with experimental results, numerical results were validated. In addition, by comparing the results of ductile fracture criteria with experimental results, the Argon ductile fracture criteria, was chosen as the most appropriate criterion to predict fracture. Also the effects of parameters as sheet thickness, bending radius and bending angle on fracture with argon selected criterion is studied.