Land Length Research Articles

Surface Integrity in Machining AISI 4340 Steel

The effect of cutting speed and tool wear land length on the surface integrity of quenched and tempered AISI 4340 steel machined under dry, unlubricated orthogonal conditions is determined. The surface region of machined test pieces is examined using optical microscopy, scanning electron microscopy, X-ray microprobe analysis, microhardness measurements, and profilometry. In addition, tool forces are measured and tool temperatures calculated. The results of the investigation show that during machining a damaged surface region is produced which is quite different from the bulk of the material. It is found when cutting at low speeds with sharp cutting tools that the damage is restricted to a variety of geometrical defects associated with the surface. It is found when cutting at high speeds or with tools having large artificially controlled wear lands that considerable subsurface damage involving changes in metallurgical structure and hardness is produced. The results are interpreted in terms of the type of chip produced during machining, the temperatures generated during machining, and the interaction between the tool nose region and workpiece. It is suggested that observations based on scanning electron microscopy are more indicative of the true surface condition than surface roughness measurements.

The effect of rake face configuration on the curvature of the chip in metal cutting

Previously published work on the mechanics of cutting with restricted contact length tools has indicated the importance of the length of the zone of sticking friction. A simple method of determining the length of this zone is proposed. The effect of the primary land configuration on chip formation and on the formation of a special built-up-edge is examined experimentally. From the results of tests on a single workpiece material, the relationship between the land length, primary rake angle and chip curl radius when using tools with chip forming grooves is obtained, enabling the chip curl radius-undeformed chip thickness relationship to be predicted.

On Microchip Formation During Machining of a High Strength Steel

The effect of cutting speed and wear land length on the phenomenon of microchip formation during machining of quenched and tempered AISI 4340 steel under dry orthogonal conditions is determined. Machined test pieces are examined using scanning electron and optical microscopy. Surface roughness is determined using a profilometer. A possible mechanism of microchip formation based on the interaction between the surfaces of the tool and freshly machined work piece is discussed. It is suggested that the grooves left by the generation of microchips may act as sources for the initiation of failures by creep, fatigue and stress corrosion cracking. It is also suggested that the results obtained using scanning electron microscopy may be more indicative of the true surface condition than surface roughness measurements.

On surface damage during machining of AISI 4340 STEEL

The effect of cutting speed and wear land length on the surface damage produced during machining of quenched and tempered AISI 4340 steel under dry, orthogonal conditions was determined. Machined test pieces were examined with a scanning electron and optical microscope. Surface roughness was determined with a profilometer. The results of the investigation show that during machining considerable surface damage is produced; the intensity of which decreases with an increase in cutting speed and wear land length. It was found that the surface damage existed in a wide variety of forms which included chatter marks perpendicular to the direction of relative work-tool motion, long straight grooves parallel to the direction of work-tool motion, large cavities, workpiece debris, tool debris, plastic deformation, cracks, microcracks and voids. The results are interpreted in terms of the type of chip produced during machining and the interaction between the tool nose region and work piece. It is shown that scanning electron microscopy is more indicative of the true condition of the surface than surface roughness measurements.

摩耗面における突起生成について(第2報)

The methods for obtaining the surface density of asperities and the real distribution of asperity heights, which differs from the distribution appearing on the surface profile curve, are considered about the isotropic and anisotropic surfaces. In the cace of the isotropic surfaces, the asperities are assumed to be spherical at least near summits. Then the surface density of asperities and the real distribution of asperity heights are obtained from the number of the peaks within a defined land length of the surface profile curve, the distribution of the peak heights appearing on it, the mean base radius of the spherical asperities, the distribution of the effective asperity heights and so on. In the case of the anisotropic surfaces, the asperities are assumed to be ellipsoidal at least near their summits. Then the method is derived with which those ellipsoidal asperities are replaced by spherical asperities which are equivalent to the original ones.

The influence of flank wear, cutting speed and cutting fluid on the surface and sub-surface workhardening produced in an orthogonal planing operation

This work is a continuation of an investigation into the factors influencing the degree and depth of workhardening produced in the surface layers of an orthogonally cut workpiece. Presently, the influence of tool flank wear land length, cutting speed and cutting fluid are reported for mild steel and aluminium alloy cut by H.S.S. tools at very low speeds; this speed range having been chosen so that the results can be applied to broaching. A mechanism by which the cutting process causes surface workhardening has been proposed previously and has been used to explain the results obtained in the earlier investigations. This model is used again to explain the influence of the cutting variables presently examined. In the last section, the influence on the degree and depth of workhardening of all the cutting variables examined in this and in the previous investigations are listed and predictions are made of the effects to be anticipated as 1. (i) the range of cutting speeds is extended, 2. (ii) restricted rake face tools are used, 3. (iii) cutting edge sharpness is increased and, 4. (iv) cutting tool lubrication is improved.

Aluminum Wire by Cold Hydrostatic Extrusion

Electrical grade aluminum wire was made by hydrostatic extrusion. Extrusion ratios ranged from 2.5:1 to 630:1. The surface finishes, diametric variations, and electrical and mechanical properties were found to compare favorably with aluminum wire drawn through conventional dies at lower composite reductions. Several process variables, including the effects of an external draw stress, die angle, and land length of die, were also investigated. The extrusion pressures and yield strengths of the extruded wires were theoretically calculated, using Pugh’s analysis for the total work done and the total strain in hydrostatic extrusion. These values were compared with the experimental results.