Analysis And Control Of Forming Defects Of Corrugated High Strength Steel Plate

With the increasing demand of construction industry, profilesmade by high-strength steel have gained their popularity.At the same time, difficulties bring by the poor formability of high-strength steel haveemerged. In this research, causes of forming defects for corrugated high strength steel plateare studied, and corresponding solutions are proposed.There are three methods to shape a single wave of a corrugated steel plate, namely"Bilateral Convergence (BC)","Fixed Unilateral Convergence (FUC)" and "MobileUnilateral Convergence (MUC)". To study the effect of different factors on the defects of edge buckling and oil canning, an orthogonal experiment was carried out with five factors (transversal convergence value, pass distance, thickness of sheet metal, down-hill value and width of web part) and three levels. The experiment was applied using commercial finite element code MSC.MARC. Longitudinal andtransversal strains at web parts were collected to implementrange and variance analysis. To avoid dangerous redundant deformation, longitudinal strain at different parts of the profile was calculated for each of the three forming methods. In addition, the obtained formulas can be used to deduce forming length. The safety factorfor forming length calculationwas simply researched.Aiming at a particular instance, the roll flower was designed and optimized using the forming length formula, and "down hill’Value was calculated. Moreover, a springback control method was proposed.The results of orthogonal experimentshowed thatthe most influential factors are transversal convergence value and pass distance, indicating that over large transversal convergence value and over short pass distance are the main causes of edge buckling and oil-canning.The calculation of longitudinal strain showed that the most serious longitudinal strain emerges at MUC forming process, and the mildest longitudinal strain emerges at BC forming process. Longitudinal strain is the main redundant deformation in roll forming process of corrugated steel plate. For all of the three forming methods, web part and wave-top part attain the largest longitudinal strain, suggesting a probability of edge buckling and corner wavy. The longitudinal strain at bevel edge of a wave gradually varies from large at top area to small at middle area and large again at web area. The average value of bending angle at precedent and current forming pass is the key value to determine whether the "down hill" method should be adopted. When the average value is smaller than a particular value, the largest longitudinal strain emerges at the top of wave, and "down hill" method can be applied to balance the longitudinal stress at different parts. Whereas the largest longitudinal strain emerges at the web part when the average value is smaller than the particular value, and the "down hill" method is then unwanted. The particular value varies from different forming methods. For FUC forming, qualified profile can be achieved when the safety factor is2. Eventually, the optimized forming die was designed.