| In recent years, with the strengthen of the green environmental protection idea,the new processing technology is more and more intentioned in the field of materialprocessing, however, the forming caused by magnetic is a forming way that relies onthe drive of the electromagnetic force. It has advantages of low energy consumption,no pollution and high precision. At the same time, with pipe barrel parts widely usedin the actual production and life, the forming caused by magnetic as a kind of highlyefficient and rapid forming technology is applied to the pipe barrel parts, which hasbecome more and more pressing technical needs in the current material processingfield. But pipe forming technology caused by magnetic is related to electromagnetic,electrotechnics, elastic-plastic mechanics and other interdisciplinary. the problem thathow to couple so many physical fields contained in the forming process is morecomplex, the traditional analytical method is difficult to realize the transient solution ofelectromagnetic field and structure field in the forming process, but the rapid developmentof computer technology and the improvement of the finite element theory provide theconditions to solve a series of problems encountered in the pipe forming process causedby magnetic. Therefore, based on ANSYS software, this article will develop thesimulation and analysis of the finite element about pipe bulging caused by magnetic.According to the basic principle of electromagnetic, combined with the feature ofthe symmetry structure of the forming system, the simplified2-D model of pipebulging caused by magnetic is established, through finite element pre-processing ofpipe, coil, mold, near-field region and far-field region, the finite element meshingmodel of the forming system is established. Making use of APDL parametric languagefeatures provided by ANSYS, this article uses the interrupt and reset technology forthe coupling field analysis to complete the application of the transient exciting currentand the solution of the electromagnetic-structure coupling field. Moreover, In order to study the collision problem between pipe and mold under the condition of the highspeed deformation，this article sets up the special contact analysis units on the outerwall of pipe and the inner cavity of mold to meet the need of stress and deformationanalysis when pipe touches mold instantly.The simulation results of the free bulging caused by magnetic of pipe shows thatpipe has narrow forced effect to the spatial distribution of magnetic field lines, and themagnetic force that pipe and coil suffer from mainly depends on the intensity of thetransient exciting current, but the magnetic field induced by pipe itself can reduce theuniformity of stress. At the same time, the deformation of pipe is mainly concentratedin the first half of the cycle, and the radial deformation declines successively from thecenter to the end, but the deformation process becomes more complex near the endarea, and appears the phenomenon of the uneven deformationCompared with the free bulging caused by magnetic, the bondage of mold underthe conditions of the forming can further reduce the divergence degree of the spacemagnetic field lines, simultaneously weaken the current density strength of pipe, andthere will be current distribution on the mold, this will cause the mold to produce heat,in turn, leading to the dissipation of energy of the system itself. Furthermore, thesimulation results also further show that the sharp rebound phenomenon will happenthe moment that pipe touches mold, and the rebound phenomenon is more markednear the center region. So whether the pipe can fully stick model largely depends onthe follow-up magnetic pressure of the system that is strong enough or not to force thebounced area to touch mold again.The influence of the parameters of the pipe forming caused by magnetic withmold on the deformation shows that the discharge voltage change will lead tovariations of magnetic field intensity and magnetic force, and in the theoreticalvoltage value range selected, appropriately increasing voltage can reduce the negativeeffect caused by the rebound phenomenon. Compared with the voltage, the influenceof wall thickness on the deformation process is mainly embodied in the aspect of thetransient stress distribution of pipe; appropriately increasing the wall thickness will do well to enhance the uniformity of the stress distribution on the axial section of pipe.Meanwhile, the study on the deformation rate of the different wall thicknesses alsoshows that the increase of wall thickness will lead to decrease of the deformation rate,but the deformation rate during the collision between pipe and mold is almostunchanged. It can be concluded that the touching process does not lead to the largeenergy loss of the system.In addition, the contact surface roughness between pipe and mold has also certaineffects on the deformation process, with the range of the friction coefficient from0.3~0.6, the contact surface roughness does not have a great influence on the propertyof the end-state sticking mold and the transient motion in the axial direction during thecontact process, but much too rough contact surface will not only reduce the wholeproperty of the sticking mold of pipe but also cause the local backward slidingphenomenon in the central location. In the end, this will lead to the local thinning ofthe wall thickness of pipe.Finally, in view of the actual demand for the different shapes pipe manufacturedin production, this article studies the bulging process caused by magnetic under thecondition of the untaught typed mold, analyzing dentally the impact of the differentshrinkage coefficients of die to the effect of pipe forming. The results show that theinfluence of die to the deformation of pipe is mainly concentrated in the opening area,instead of the end-state area. As for the aluminum pipe the wall thickness of which is1.2mm, when the shrinkage coefficient is0.65, the maximum location of the transientstress distribution appeared in the slope area of die, when m roses to0.67, it graduallyspreads to the entire opening area. What is more, in the range of theory, appropriatelyincreasing the shrinkage coefficient will contribute to the sticking mold of the outerwall of pipe; especially in the opening area of die, but the larger coefficient willreduce the overall effect of sticking mold. |
PDF Full Text Request