Mechanical Engineering - Theses
Permanent URI for this collection
Search Results
1 - 1 of 1
-
ItemEffect of tool form and workpiece geometry in metal cutting( 1970)A survey on the mechanics of cutting has been carried out. It is shown that little or no work has been done on the cutting analyses of practical three dimensional machining operations such as form cutting or turning. (Appendix A). Thin shear plane deformation analyses are developed for double edged tools. These involve triangular tools performing full depth and chevron type vee grooves as well as lathe cuts. Two alternative yet similar analyses are derived for lathe cuts. A numerical investigation of these analyses is made from which it is shown that the dimensionless power force FP/TA is related to the chip length ratio and is virtually independent of all other variables. Thus variables which alter the chip length ratio will change the forces in machining. These analyses, like all other orthogonal cutting analyses, cannot theoretically predict the chip length ratio although it can be experimentally measured with relative ease and rudimentary equipment. It is also found that there is no theoretical justification for the chip flow rule nc = i in turning. The geometry and specification of lathe tools is studied and the problems and errors in grinding such tools are determined. The difficulty of finding the ‘best’ specification with respect to the theory of cutting is considered by applying the single edge oblique cutting theory and the developed double edged tool analyses. It is shown that no positive conclusion can be achieved without theoretical predictions of the chip length ratio. An experimental investigation is carried out to check the analyses. A series of orthogonal cutting tests is run to form a basis for comparisons with the other cutting operations. Statistical methods such as regression analysis, analyses of variance and co-variance are used to process the data. It is found that the experimental trends for the various tool-work combinations are consistent with those obtained from orthogonal cutting. The measured forces in cutting are shown to be due to cutting-edge forces and deformation forces represented by the analyses of cutting. The shear stress in orthogonal cutting is constant and compares favourably with the constant values found from full depth triangular cuts as well as from higher speed up-milling results. Substantial qualitative and quantitative correlation is achieved between all the tests run showing that the analyses are reasonable representations of the physical case. Methods of using the analyses for predicting the forces in machining are developed and discussed.