Study On Strip Wound Die For Compound Cold Extrusion

Compound cold extrusion is a high-efficiency, high-quality, low-power, low-cost dieprocessing technology, which plays an important role in modern processing. However, the diebears great loads during the forming process. The concave die bears the greatest and mostcomplex load, likely to cause the failure of the die. Prestressed structure concave die is aneffective way to significantly improve the life of the die, which is essentially a concave diewhere a prestress is imposed to offset or partially offset the die load, so as to improve the die life.Prestressed structure concave dies are generally divided into combined prestressed concavedies and strip-wound prestressed concave dies. Strip-wound prestressed concave die came intobeing and it has a greater prestress, which has been developed and put into production inabroad. The development at home is still in the initial stage, and it will have an positive impacton the mold industry if successfully developed.On the basis of previous studies, the stress of the cold extrusion die in the working state isanalyzed and further studies on winding the strip-wound prestressed concave die are madethrough integrated numerical simulation, theoretical analysis and experimental research. Somemeaningful conclusions have been obtained.Firstly, the key technology of the numerical simulation of cold extrusion is developed,which provides technical support for the subsequent finite element analysis. After some coldextrusion parts are researched, finite element analysis of the concave die stress in the coldextrusion process of the combined prestressed concave die and the thick-walled cylinderconcave die are carried out through methods of contact constraints and remeshing. Theequivalent stress distribution of the extrusion die is obtained. In contrast, too small prestresswill lead to the failure of the die, which proves that prestress is of great significance on thestress distribution of concave die.In order to seek concave dies which can provide a greater prestress, research on thestrip-wound prestressed concave die is put on the agenda. The prestress of strips cannot bemeasured directly. As a result, the relationship between preload and displacement of the dieinner diameter is needed through theoretical calculation. The credibility of the results is verifiedthrough numerical simulations. With the measurement of the core diameter before and after steel strip winding and the relationship between preload and displacement of the die innerdiameter, the prestress provided by strip-wound prestressed concave die can be obtained.Secondly, the winding process of strip-wound prestressed concave die is developed tocarry out the winding smoothly, which is the basis for the strip winding. The beginning andending is the key of the strip winding. Lots of analysis shows that the cementing is the bestchoice. Tensile shear strength tests of four kinds of high-strength metal plastic are proved to befeasible. Through the comparison, selection of high-strength metal plastic can meet the needs.The design and manufacture strip winding end provides a guarantee for the smooth winding.Finally, wind the strip-wound prestressed die. Calibrate the tension system of windingdevice before winding to ensure the accuracy of the device output tension. At the same time,standard specimens are made for tensile strength tests which provide guidance for the windingtension. The die sleeve for winding is designed and manufactured. Through the average ofmulti-point measurements, displacements of the die inner diameter are measured and theprestress provided by strip-wound die is obtained. Compared with the prestress provided bycombined die, the superiority of the strip-wound die is demonstrated.To sum up, our conclusion is superior and provides theoretical and technical support to thefurther design and development of strip-wound prestressed concave die.