Theoretical Research And Numerical Simulation On The Four-Roll Bending Forming Process

The four-roller coiling machine has been increasingly used in aerospace,petrochemical and marine industries because of its high forming precision,pre-bending and short straight edges.With the increasing demand for high-precision cylinder parts in industrial equipment,insufficient research on roll forming theory and the four-roll bending process have led to low roll forming accuracy and low efficiency,which restricts the automation of four-roller coils and their application in industry.Therefore,the research on the control of sheet forming accuracy and the determination of process parameters during the roll forming process of the four-roller coiler will be studied in this paper.Based on the theory of plate bending and deformation,this paper studied the evolution of stress and strain in the deformation zone during the four-roll bending forming process.By establishing the four-roll bending process model of the plate,the numerical relationship between the displacement of the side roller and the forming radius were deduced.In addition,the finite element simulation test was used to analyze the influence of the factors such as the displacement of the side roller,the thickness of the plate and the bending speed on the forming quality in the four-roll bending forming process.The simulation results show that as the displacement of side roll increased,the downtrend of the sheet forming radius gradually slow down and the quality of the formed sheet also decreased.Plastic strain fluctuation on plate surface will decrease as the thickness increase,quality of thick plate will be better than that of thin plate.Rotational speed has less influence on final shape radius,while reduce rotational speed will improve the uniformity of formed plate,reducing plastic strain fluctuations of plate shaping surface,forming quality can also be improved.It was verified that the multi-pass roll-bending forming process can effectively improve the roll forming defects and improve the quality of roll forming by using the finite element simulation test to compare the results of single-pass and multi-pass test.By establishing the multi-pass roll-bending forming control algorithm,the standard deviation of the forming radius is reduced,the distribution uniformity in the circumferential direction is improved,and the three-pass roll-bending forming of the plate can be achieved by appropriately adjusting the process parameters.The results show that with the increase of the number of roll-bending,the plastic strain distribution on the surface of the plate is more stable and uniform,and the plastic strain fluctuation on the surface of the cylinder is significantly lower.At the same time,the plastic strain difference between the four-roller pre-bending stage and the continuous roll bending stage also decreases as the number of roll-bending increases,it shows that the multi-pass roll-bending method can effectively improve the processing precision of the plate.;The control algorithm of multi-pass roll-bending based on actual roll-bending data has strong adaptability and is almost unaffected by plate thickness.It can not only improve the sheet forming quality after multi-pass roll-bending,but also facilitate three-pass roll-bending forming,effectively improve the efficiency of sheet metal processing.As verified by the four-roll bending forming test,the four-roller bending process model established in this paper has good accuracy,and the four-roll bending simulation model and multi-pass roll-bending forming control algorithm have high reliability and applicability.Through numerical modeling and simulation experiments,it can provide a theoretical basis for the determination of four-roll bending process parameters,improve the work efficiency,and provide theoretical guidance for the automation of four-roller coiling machine.