Study On The Contact And Interaction Mechanism Between The Guiding Pads And The Hole Wall Of BTA Drill

Nuclear energy,as one of the cleanest energy,has developed rapidly in China in recent years.However,one of the bottlenecks in nuclear power equipment manufacturing is the deep hole processing of steam generator tube-sheet.BTA drill has been widely used in the deep hole processing of steam generator tube-sheet,with higher material removal rate and better machining hole accuracy.During working of BTA drill,the internal-chip removing and self-guidance principle are applied,guide pads not only perform a self-guidance function,also plays a vital role in hole forming and processing quality of hole wall.This paper takes the third generation deep hole processing technology of nuclear steam generator tube-sheet as the background,and provide relevant parameters for the nuclear tube-sheet deep hole drilling and relevant theoretical basis for the designing and optimization of BTA drill,with the study of hole forming mechanism in BTA drill drilling and contact relation between guide pads and hole wall.In this paper,taking guiding pads of BTA dill as the research object.The cutting mechanics model of BTA drill,based on the theory of metal cutting,is established;the contact mechanics model between BTA guide pads and hole wall is established,according to Hertz theory,metal elastic deformation theory and plastic deformation theory;The variation law of the deflection angle along the axial direction between the guiding pads and the hole wall is analyzed;the stress of the surface and the compression stress of the contact surface on the hole wall are analyzed;The effect of the guiding pads on the hole wall and the variation of the hole diameter are analyzed.ANSA finite element pre-processing software and ABAQUS finite element analysis software are used to analyze the relation between the BTA dill guiding pads and the hole wall.On account of geometry complexity for BTA drill cutter body,a good-quality meshed finite element analytical model is established with ANSA in order to make the result more accurate,then ABAQUS finite element analysis software is used to solve the model.Variation of hole diameter,compression deformation and contact areas between guide pads and hole wall are studied,under different drilling depth.The experimental platform for BTA drilling with staggered teeth was built,change laws of compression deformation between guide pads and hole wall are studied,the variation of drilling hole diameters,cut by BTA drill with different drilling depth,is studied.Through the study,the result can be found:the hole wall has the elastic and plastic deformation under the compression of first guide pads and second guide pads,the quantity of compression with the first guide pad is larger than the second’s.With the increase of the depth of drilling hole,the compression of the first guiding pads on the hole wall increases,and the hole diameter increases gradually,and the spiral growth trend in the hole diameter increases during the drilling.The inclination angle of the guiding pads and the hole wall always exists in drilling,and the increase of the feed rate at the same depth will lead to the increase of the inclination angle,the increase of drilling depth at the same feed can also lead to the increase of dip angle.The relation between the guiding pads and the contact area of the hole wall is just the opposite of the change of the inclination of the guiding pads and the hole wall.