Research On Incremental Forming Mechanism And Process Parameters Of Figure-eight Parts

The sheet metal incremental forming process is an emerging flexible moldless forming technology.The shape of the part is decomposed into a series of contour contours.The sheet material is locally deformed under the layer-by-layer motion of the tool and finally formed into the desired shape.Compared with the traditional sheet forming methods,it does not require a special mold and has better adaptability to parts with complex shapes.It has broad application prospects in the context of increasing demand for small-batch production and accelerating the iterative speed of product updates.Over the past two decades,the forming mechanism of incremental forming technology have been researched by many scholars,but the research objects are symmetrical truncated cone parts,cylindrical parts or truncated tetrahedron parts.Most of the parts in actual processing are asymmetrical or incompletely symmetrical,so the forming mechanism of such objects needs further study.In this paper,the incremental forming mechanism of a representative part—a figure-eight part among asymmetrical parts(axisymmetric and centrally symmetric not at the same time)is studied.Firstly,the incremental forming process of the part is simulated with three-layer solid elements,and the similarities and differences of thickness distribution,equivalent strain distribution,the proportion of each strain component,the axial strain and the circumferential strain in the two characteristic sections—the middle section and the corner section of the part during the forming process is discussed.The results show that the middle section of the part after forming is thinner than the corner section,and the maximum thickness difference is about 0.2mm.Since the middle section and the corner section are at the same contour,the sine theorem cannot completely applicable to the thickness prediction in the incremental forming of asymmetric parts;the forming process is a collection of tensile,bending,and shear effects;the middle section and corner section of the part have small differences in normal strain,different proportions in shear strain,and 12,which has a large proportion in the middle section,was the main factor causing the middle section of serious thickness reduction.Secondly,the incremental forming process of parts under different process parameters is simulated with shell elements,which has higher computational efficiency,and the equivalent stress,equivalent strain and thickness of the middle section and corner section under different process parameters are analyzed in detail.The results show that the tool diameter should not be too large or too small;the smaller the layer feed,the more uniform the equivalent stress and equivalent strain distribution of the part,and the better the forming quality;both the equivalent stress and equivalent strain increase with the decrease of the forming angle,and the thickness reduction is more serious;under the influence of the tool infeed and lifting,compared with the middle section,the corner section has a higher equivalent stress and equivalent strain value in the early forming area,and the thickness reduction is more serious.As the amount of deformation is increased,the result is exactly the opposite.Finally,the multi-pass forming method was used to process the figure-eight straight-walled parts.The sheet first cracked at the middle section when it was stretched to about 18 mm,which was consistent with the simulation results that more serious thinning exist in the middle section,and the forming angle of the first pass has a greater effect on the minimum part thickness.