Research On Sidewall Curl Of Sheet Metal

Sidewall curl can make the error of the shape and dimension for the parts, and leads todifficulty for the subsequent welding and assembly.It even can cause the scrap parts in somesevere cases. Therefore, research and control on sidewall curl problem has some practicalsignificance.This paper mainly studied for sidewall curl problem, and explained the forming principleby analyzing the distribution of stress in the thickness direction of sheet metal. The analysisresults show that the stress difference in thickness direction can effectively decrease sidewallcurl problem. This paper designed the floating drawbead technology to reduce thicknessdirection stress difference in order to inhibite sidewall curl, and then used the finite elementsimulation and related experiments to verify the feasibility of this technology. In this paper,specific work is as follows:1. The theoretical analysis of mechanism of sidewall curlAt first, introduce the form of sidewall curl, and then analyze sidewall curl problem bycomparing the v-shaped bending and u-shaped bending. Take the flanged u-shaped crosssection as an example, the flanged u-shaped cross section can be divided into five parts. Thenstudy its stress in thickness direction and reverse bending moment after unloading. And thenilluminate the flanged U section springback especially the mechanism of its sidewall curlphenomenon by reverse bending moment of superposition.2. Floating drawbead technology is designedIntroduce the control principle and the general method of sidewall curl problem. Theblank-holder force is put forward from the factors influencing the sidewall curl. And achievethe effect controling sidewall curl by controlling the load curve of blank holder force. Anddesigned and produced stamping molds with the floating box of drawbead. Stamping resultsshow that the proposed drawbead float process can effectively control the sidewall curlproblem.3. Sidewall curl problem of the flanged u-shaped piece is studiedUse the finite element software ABAQUS to simulate the forming and springback of theflanged u-shaped piece in the plane strain condition, and analyzes the influence of the blank-holder force, material thickness and die radius on side curl and the springback angle.The results show that just increasing blank-holder force does not fundamentally restrain thesidewall curl. Floating drawbead technology under the condition of the smaller blank-holderforce, can effectively inhibit the side curl, and can avoid the fracture when blank-holder forceis too large. The experimental results also confirmed this.4. To study the side curl problem of box partsThe influence factors of sidewall curl and springback of box Angle is analyzed byAUTOFORM. And compare the traditional forming method and floating drawbeadtechnology on box wall curling effect. Simulation results show that the corner of the box haslittle influence on sidewall curl phenomenon, which shows the research conclusion of theflanged u-shaped piece sidewall curl phenomenon can also be used on the box. Floatingdrawbead technology using small blank-holder force can inhibit sidewall curl and greatlyreduce the fracture problem for the box.