Study Of Small Radius Tube Bending With Numerical Experiment Based On Response Surface Methodology

Because of the space limitation, tubes on ship are often bended with very small radius. This would lead to forming defects such thinning, wrinkling and section flattening, thus result in production difficulty.In the process of tube bending, one forming index being optimized may worsen the other index. Besides, there are many influencing factors which interact with each other. Researches before mostly discussed the changing law of one index regarding one factor. This thesis analyzes tube bending process with response surface method(RSM) so that the variation of forming index is studied considering multiple factors and the interactions between factors are included. Plus, the qualified factor region limited by multiple forming indexes can also be gained.This thesis conducted the RSM analysis for two cases respectively: one for small radius bending of a thin tube using mandrel with a core ball, the other for small radius bending of a thick tube using mandrel without core ball. Based on four design factors, this work investigated three forming indexes namely: interior wrinkling ratio, exterior thinning ratio and section flattening ratio. Central composite design was used for design of experiments, response models were gained through series of numerical experiments and fitting analysis. Primary limit index was predicted, factors’ effects were discussed and preferable value of main factors were recommended, mechanical explanations were made based on finite element analysis(FEA) results. Design factor region qualified for all three indexes were achieved and optimal settings and response models were verified by FEA.In order to ensure the validity and efficiency of the series numerical experiment used in RSM process, key settings of effective tube bending simulation were forwarded, secondary development of function and graph user interface was conducted, a special plug-in for tube bending numerical experiments which covers the whole process including modeling, job submission and post processing was formed, key functions such as series models generation, continuing submission of jobs and automatic index calculation and field output writing were added in order to serve tube bending study with RSM.Effective study can be done using response surface method with the help of tube bending numerical experiment plug-in, meaningful conclusions can be achieved and the qualified area limited by multiple forming index can be referenced in the die set of actual production.