Browsing by Author "Welsh, M. J. M."
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Item Open Access Calculating the shear angle in orthogonal metal cutting from fundamental stress-strain-strain rate properties of the work material(College of Aeronautics, 1964-03) Oxley, P. L. B.; Welsh, M. J. M.An analysis of the orthogonal metal cutting process is made which enables the shear angle to be calculated from certain fundamental properties of the work material and the specified cutting conditions. Shear angles are calculated for a range of cutting conditions and good agreement is shown between theory and experiment. In particular, such trends as the decrease in shear angle with decrease in cutting speed and the tendency for the chip to become discontinuous at slow cutting speeds which are found experimentally and cannot be explained in terms of previous shear angle analyses, are shown to be consistent with the present analysis.Item Open Access Determination of effective stress-effective strain relationship for use as a machinability index(College of Aeronautics, 1964-03) Welsh, M. J. M.In recent work it has been shown that the effective stress effective strain relationship of a work material is important in determining the shear angle in orthogonal cutting. This note describes the method of obtaining this relationship.Item Open Access An explanation of the apparent bridgman effect in merchant's orthogonal cutting results(College of Aeronautics, 19) Oxley, P. L. B.; Welsh, M. J. M.Abstract In Merchant's modified shear angle solution it is assumed following Bridgman that the shear strength of the work material is a function of the hydrostatic stress. Although Merchant's experimental results confirm the assumed relation subsequent workers have failed to obtain such agreement. In this paper it is shown that Merchant's results can be explained independently of the Bridgman effect by considering the variable flow stress properties of the work material, which are strain-rate dependent.Item Open Access Preliminary report on the analysis of the stresses in a die-bolster combination(College of Aeronautics, 1964-08) Oxley, P. L. B.; Welsh, M. J. M.An analysis is presented of the stresses in a carbide die-steel bolster combination. Results from a computer treatment of this analysis are given in tabular and graphical form. Suggestions are made as to the choice of interface diameters, and a nomogram is drawn enabling the maximum allowable interference to be selected.Item Open Access The relevance of the mechanics of metal cutting to machinability(College of Aeronautics, 1965-08) Enahoro, H. E.; Welsh, M. J. M.INTRODUCTION The process of metal cutting is a subject of great importance to the makers and users of machine tools. Extensive research has gone into the subject but has still left most of the phenomena unexplained. Tool life is the main interest and before any real improvement in this factor can be made, the basic metallurgical factors governing the interaction between tool and workpiece must be better understood. Such improvement can be effected through control of the wear process since both tool and workpiece are metallic and machining is a process of metal flow which is associated with a serious wear problem. The absence of exact knowledge has however hampered empirical and mathematical approaches to the problem. Basically all machining operations are considered as either oblique or orthogonal cutting, the former requiring three dimensions to specify the geometry of the cutting part of the tool and the latter two. The basic metal cutting process to be considered is that which is common, in one form or another, to all metal cutting operations using a tool, that of the wedge-shaped tool in fig. 1 (a-j) (1). Analyses of cutting have been mainly concentrated on the relatively simple case of orthogonal or two-dimensional cutting. Here the tool is so set that its cutting edge is perpendicular to the direction of relative motion between tool and workpiece and generates a plane parallel to the original work surface. In doing this the tool removes a layer of material termed the chip. One of the major objectives of metal cutting theory is the determination of machining forces, chip geometry, tool life, energy consumption and surface finish from a knowledge of the physical properties of the workpiece and tool material and the cutting conditions alone. If this could be achieved, lengthy chip measurements, delicate dynamometry, tedious and costly tool life tests and surface finish measurements might be dispensed with.