Hideaki Kudo

Some new slip-line solutions for two-dimensional steady-state machining

Abstract For restricted and unrestricted cutting tool faces, certain new slip-line fields have been obtained where there is completely or nearly uniform frictional resistance and which produce a straight chip and are valid beyond the limitations of previous solutions. Some possibly correct solutions showing chip curl have also been presented, e.g. where the frictional resistance decreases along the tool face from the tip to the tool-material separation point. Using these, cutting resistance or force, curl radius, chip thickness ratio and natural contact-length have been determined in relation to the rake angle and friction stress. Slip-line fields containing a built-up edge were obtainable only where the rake angle was negative and where there was chip curl.

An upper-bound approach to plane-strain forging and extrusion—I

Abstract Flow patterns on sections of lead billets during various plane-strain forging and extrusion operations are photographed and presented. These are compared with predicted most suitable velocity fields obtained by the method described in Parts I and II of this series of papers. The agreement is satisfactory and the proposed upper-bound-approach method is thus found to be simple and reliable for practical purposes.

Temperature Measurement of CBN Tool in Turning of High Hardness Steel

Abstract The temperature at the tool flank, which has an effect on the tool life and on the machined surface integrity, is measured using a two-color pyrometer with a fused fiber coupler. This pyrometer makes it possible to measure the temperature of a very small object without emissivity affecting the results. A CBN tool is used as the cutting tool. A high carbon chromium bearing steel, a chromium molybdenum steel and a quenched carbon steel are used as work materials. The temperature of the tool is highly affected by the cutting speed, but the influence of the depth of cut and the feed rate is not so great. In the cutting of the high carbon chromium bearing steel, the temperature is 800 °C at a cutting speed of 100 m/min and increases with the increase of cutting speed, reaching 950 °C at 300 m/min. There is a close relation between the tool temperature and the hardness of the work material. The influence of cutting speed on tool wear is considerable.

A slip-line field for mid-plane cracking or splitting in sheet drawing

Abstract Many of the two-centred fan slip-line field solutions for sheet drawing have been shown to be statically inadmissible due to overstressing at the die exit when the mid-plane hydrostatic pressure approximately equals -κ. An attempt is made to overcome this problem by the proposal of an alternative slip-line field which allows exit splitting at the mid-plane. The limitations on the use of this slip-line field are described and in the light of these limitations a further possible field is suggested for wall ironing.

Cropping of Round Bar Utilizing Plastic Fatigue

As an alternative to existing bar and tube cropping techniques, a cropping method is described which utilizes plastic fatigue fracture and consists of roller grooving and subsequent rotary bending. Solid billets thus cropped at an appropriate number of rotations to fracture have flat and smooth cut ends and show no deterioration in ductility in a subsequent side pressing test. The present technique is most suitable for relatively brittle materials, such as high-speed steel, since only several tens of rotations are required to obtain a good cut end. Preliminary experiments in applying this method to tube cropping give promising results. Directions to shorten the cropping time for less brittle materials are suggested.