| Spinning is a kind of plastic forming process, with characteristics such as local continuous deformaiton, is an efficient process for forming cylindrical hollow parts. Stagger spinning is a special tube spinning. Three uniformly distributed rollers in circumferential direction are staggered at particular intervals both in axial and radial direction to complete multi-pass thinning in a single feed. However, there are also some defects and inappropriate simplified methods in current model of stagger spinning, relationship among key parameters affecting quality of products becomes more complicated. Some unique phenomenon such as interference have generated due to the existence of combination of different size parameters.This paper focuses on the key technical problems on stagger spinning process. A modified three-dimensional finite element model of stagger spinning in LS-DYNA platform are established, based on the characteristics of stagger spinning in actual production process process. Analysis of the deformation mechanism and influence of the force parameters are carried out. Based on this, influences of interference phenonmena are researched and methods to exclude interfence phenonmena are derived. Then, reseach of the key parameters without interference phenomena are conducted to make foundation for the accurate and efficient research of stagger spinning in both simulation and actual production.The specific contents include:The modeling method of the improved stagger spinning simulation model are propsed and analysis of the key influence parameters are conducted:based on the characteristics of stagger spinning processes, a modified three-dimensional finite element model is developed under the FE software environment of LS-DYNA, based on characteristics of stagger spinning process and actual production conditions. Characteristics of the model including full model, hexahedral element, speed boundary mode, full simulation, double precision mode, no-interference and so on. Modeling procedures and key technologies are compared and summarized.The analysis of forming mechanism and force parameters of stagger spinning: based on the conducted simulation model, the deformation mechanism of the regional flow parts is analyzed. Stress and strain under the continuous loading condition are extracted to analysis the process and characteristics of stagger spinning. Meanwhile, based on the deformation characteristics, analysis of the contact area and force are carried outThe analysis of the interference mechanism and elimination methodst:A unique phenomenon called position and inclination interference in stagger spinning process are characterized and investigated. A series of trials are presented to illustrate the causality of visible bulge and concave of wall thickness between position interference, as well as the imbalance and oscillation of roller force. Also, effects of inclination interference have been discussed. Finally, formulae of roller interval selection without interference phenomenon are derived based on the characteristics of position and inclination interference to help exclude invalid combination of roller intervals and guide selection of inclination of roller and blank, which will effectively reduce the amounts of invalid experiments or simulations.The analysis of key interference parameters without interference phenomenon: based on offered method, the ranges of key parameters without interference phenomena are obtained. After interference phenomena are excluede, research on the key character parameters are carried out. Appropriate combinations of three rollers are obtained. Then, research on effects of roller intervals on stagger spinning process have been conducted to make improvement of current research and offer reference for research of stagger spinning without interference phenomena. |
PDF Full Text Request