A Study On Technology Of Doule-Sided Roll Forming Of Discal Parts

In order to meet the demand for the turbine disk with larger diameter and higher properties,a new technique of double-sided roll forming of discal parts has been developed recently.As the fundament of the technology,the basic feature and deformation rule are studied by means of combining theoretical analysis,numerical simulation and experiments in this thesis.The obtained studied results are listed as below.Firstly,the geometric parameters for describing the roll forming results are defined,and then the parameters affecting the final forming results are also defined.The parameters include the workpiece geometry,tool geometry and processing parameters.Under some assumptions a mechanical model of the double-sided roll forming of discal parts is developed here,and an expression of roll forming load is derived from the model.A set of curves for describing the variation of the force and the moment with the roller conical angle,the roller front end radius and the high reduction are presented.By using the commercial software DEFORM3D,the roll forming processes under different conditions are simulated numerically and the influences of the roller geometry,processing parameters on roll forming load,strain distribution,strain rate distribution,velocity distribution,and the groove configuration are also obtained.The single groove test,the interaction test of grooves,the roll forming test of wide groove and roll forming test of the planar disk are carried out for different purposes.A lot of data on the groove depth,"shuaigao"(means height of the material stack after roller),the impress depth,other material stacks,the disk radius spread and etc are measured and the variations of the groove depth,shuaigao,the impress depth,the disk radius spread with rolling times,groove position and the roller rotate speed are summarized from the data.An expression on relationship of the roller feed in disk thickness direction with roller rotate speed,groove position and the groove depth has been derived by means of the fitting analysis of above data.The equation can eliminate the error due to the structure rigidness of the tester.The data on the material stack and its effect area are measured during wide groove roll forming under different rolling times and different rolling positions.The experimental result from both groove interaction test and wide groove rolling test show that it is better for the disk shape and surface quality that the roller feed from center to outskirts of discal part.Above experimental results are used for design of roll forming processing parameters of a planer disk.The roll forming test shows that the formed planer disk has a few error and better surface quality,which shows the validity of above experimental results.Some defects,such as skidding,pulley defect,disk warp and excessive material stack etc,may appear during roll forming.The cause and preventives of the defects are studied here by using multiple methods.The study of skidding defect is emphasized here.A theoretical relationship between the minimum friction coefficient without skidding,the roller size and the groove geometry has been derived.By means of numerical simulation,the skidding mechanism has been discovered through comparing both disk circumferential speed and roller circumferential speed.In experimental work,a method for evaluating skidding has been defined,a lot of experimental data on influences of the rolling times,roller speed on skidding are measured,and the technical methods for avoiding skidding have been suggested here.A comparison of both calculated and experimental results on single groove rolling shows that both results are in agreement very well.More qualitative comparisons of them show that the conclusions from the numerical simulation are believable and available for analysis of actual roll forming process.Finally,a design procedure of the gradual roll forming for general complex asymmetric discal parts has been studied.The key of the processing design is to a method to calculate the workpiece size and the roller displacement in every rolling step from the high reduction,the rolling position and the roller rotate speed.In order to validate the design procedure a roll forming test of an actual aeroengine turbine disk with reduced scale has been carried out.The size error of the formed disk is very small.The result shows the developed design procedure of the gradual roll forming is available.