Study On Staggered Extrusion Curvature Model Construction And Process Analysis Of Magnesium Alloy Bending Member

Lightweight is an important way to achieve energy reduction and emission reduction.Using arc material is a form of structural lightweight.Due to the need for bending process,the traditional arc material has the disadvantages of high cost and long production cycle.In the previous research of the research group,the staggered extrusion process is proposed.The arc material is obtained directly through the extrusion process,and the arc material is obtained quickly and conveniently.It has the advantages of the extrusion process,and there are no bending defects.The steplike stem is used for staggered extrusion to load the billet,and the curvature of the arc material in the extruded part can be adjusted by changing the staggered distance.In addition to the influence of staggered distance,the change of extrusion ratio can also change the structure and curvature.Therefore,aiming at different combinations of staggered distance and extrusion ratio,the forming process of loaded metal with special stem is systematically studied in this paper.The quantitative relationship between staggered distance h and extrusion ratio and curvature control of arc-shaped material is clarified.The evolution mechanism of characteristic parts of billet before extrusion in staggered extrusion process is revealed.It provides a theoretical basis for the application of staggered extrusion process.In order to clarify the forming process of metal loaded by special stem,the metal flow behavior of staggered extrusion was analyzed.At the initial stage of extrusion,the metal flow state and dead zone distribution are similar to the reverse extrusion flow state.With the gap between the billet and the stem filled,the metal flow state becomes similar to the forward extrusion state.The flow velocity at the extrusion die mouth presents a gradient distribution,and the end of the step-like stem near the core die presents the maximum flow velocity.For the shear stress analysis of typical parts,the stem shears the billet in the early stage of extrusion to form a triangular shear zone.Until the later stage of extrusion,the shear of the stem to the billet disappears,and there is only the shear effect at the die mouth.The load characteristics of stem and core die are analyzed.The load curves show four stages:pier thickness,press in,reverse extrusion filling and steady-state extrusion forming.Compared with the load curves of different staggered distance and extrusion ratio,the staggered distance has a great influence on the maximum load peak of the die.In order to obtain the quantitative relationship between staggered distance h and extrusion ratio ?,the upper limit model of staggered distance extrusion process was established.By calculating the plastic deformation power consumption of the model,the power consumption of the velocity discontinuity and the friction power consumption,the deformation power consumption of the model is obtained,and the eccentricity ? is calculated,and the theoretical curvature is calculated.In order to verify the accuracy of the model,the results of finite element simulation and experiment are compared with the theoretical load,extreme value of velocity and bending curvature.It is found that the simulation and experimental results are in good agreement,and the theoretical value is consistent with the change trend of both,but the value is slightly larger.Based on the above research,the characteristic region of staggered extrusion formed components with staggered distance h = 16 mm and extrusion ratio of 11.11 is analyzed.Before the billet is extruded,the shearing effect of the stem on the billet promotes the refinement of local grains in the extrusion barrel.After passing through the core die,it was further refined due to shear deformation,and complete dynamic recrystallization occurred.A.The {0001} basal texture of zones B and C tend to be perpendicular to the extrusion direction(ED),the texture of zone a in forward extrusion shifts counterclockwise,and the texture of zone B and C in reverse extrusion shifts clockwise.The texture of extruded D zone turns parallel to the extrusion direction(ED),but there is a certain deflection angle ??The above research is of great significance to the curvature control and microstructure control of arc-shaped materials formed by staggered extrusion process,provides a scientific basis for the formulation of magnesium alloy staggered extrusion process scheme and the accurate control of component curvature,and provides scientific guidance for the microstructure evolution of high-precision arcshaped materials.