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Cemented carbide cutting tools containing a high percentage of cobalt binder (9-13%) are used for rough machining applications involving interruptions, owing to their high fracture toughness. However, these tools are prone to deformation under such conditions. A design approach can be effectively used to develop a coating scheme which optimizes the critical properties of such coatings for improved...
The optimal method calculating the fractal dimension of a machined surface profile is discussed in this paper. Through the analysis of the results calculated by use of the Weiestrass-Mandelbrot fractal function with known fractal dimensions, the variation method is found to be the best one for calculating the fractal dimensions of the surface profiles among the power spectrum method, the cover method...
Surface residual stresses due to turning operations in AISI 304 type stainless steel were studied as a function of machining speed, feed rate, depth of cut, and tool geometry and coating. Residual stress tensors were determined using X-ray diffraction technique. The effects of turning conditions and tool on the residual stresses were discussed in terms of mechanically and thermally induced non-homogeneous...
The surface integrity of the machined component has received greater attention over the last 20 years, especially in relation to high performance materials. Due to the inherent differences between abrasive machining and single point cutting, distinct surface texture patterns will be produced, which together with the associated metallurgical alterations can lead to substantial variations in component...
Nickel-based alloys can be machined using techniques similar to those employed to cut ferrous materials, however, additional requirements are imposed due to the poor machinability of these alloys. Through a series of cutting tests, the authors have applied techniques to optimise the cutting conditions for high speed steel circular saw blades machining materials from three principal categories of nickel-based...
Experimental data has shown that calcium containing resulphurised free machining austenitic stainless steel has much better machinability than resulphurised free machining austenitic stainless steel, especially in terms of tool life. A thick adhering layer has been found on the rake and flank faces of a WC-TiC-Co cutting tool when machining calcium containing resulphurised austenitic stainless steel...
In order to clarify further the formation of an adherent layer on a cutting tool when machining a calcium deoxidized low sulphur content austenitic free machining stainless steel, the deformation and crack propagation around inclusions were monitored dynamically using a micro-cutting device in a scanning electron microscope. The temperature distribution field within a cutting tool under conditions...
An experimental study was conducted to determine the influence of material properties on the surface integrity and texture that results from abrasive waterjet (AWJ) machining of metals. A microstructure analysis, microhardness measurements, and profilometry were used in determining the depth of plastic deformation and surface texture that result from material removal. Models now available for dry...
The influence of cutting parameters and material properties on the residual stress fields resulting from abrasive waterjet (AWJ) machining of metals was analyzed. The measurement and evaluation were conducted using X-ray diffraction with the sin 2 ψ and X-ray integral method (RIM) of analyses. For all materials and cutting conditions, a significant bi-axial compressive residual stress was...
Slip-rolling friction and wear tests were performed in a twin disc tribometer of the Amsler type at 3 GPa over 2 million revolutions. Unadditivated paraffinic oil and water were used as lubricants. The surfaces of the ceramics were machined by different processes, resulting in different surface roughnesses (i.e. rough and fine honed, rough and fine ground, rough and fine lapped, and rough and fine...
This study addresses the influence of grinding-induced roughness, subsurface damage and residual stress on the repeated impact behavior of silicon nitride, a leading material for diesel poppet-valves. A ball-on-flat repeated impact tester was used to evaluate the impact wear of GS-44 silicon nitride coupons machined in three different conditions: coarsely ground (with 80-grit wheel), finely ground...
To investigate the effect of tool geometry in nanometric cutting, molecular dynamics (MD) simulations of nanometric cutting were carried out with tools of different edge radii relative to depth of cut. Simulation studies were carried out by varying the tool edge radius, r (3.62– 21.72 nm) and depths of cut, d (0.362–2.172 nm) by maintaining the d r ration constant (0.1, 0.2 and 0.3). Variations of...
With the projected widespread application of Metal Matrix Composites, it is necessary to develop an appropriate technology for their efficient and cost-effective machining. This paper deals with the study of feasibility of rotary carbide tools in the intermittent machining of Al/SiCp composites. A rotary tool holder was designed and fabricated for this work. Experiments were designed using Taguchi...
The formation of tribo-layers during machining is very common, especially when machining 'free machining' steels. Previous flow zone models of metal cutting have not included the shear strain rate distribution at the tool-chip interface, although the distribution directly affects contact behaviour. A new flow zone model is developed, based on the concept of the cutting interface, which occurs where...
A study was undertaken to investigate the wear mechanisms of CBN/TiC cutting tools in the finish machining of BS 817M40 (AISI 4340) steel of 52 HRC. A fourfold variation in tool wear rate was observed in the machining of three different heats of this steel. One of the primary characteristics of the tool wear surfaces is the manner in which the TiC phase stands proud of the CBN phase. The relative...
A study was undertaken to investigate the mechanisms of alumina/TiC cutting tool wear in the finish turning of hardened steels with particular cognisance of the work material inclusion content. A six-fold variation in tool life was observed when machining different heats of BS 817M40 steel (similar to AISI 4340) of 52 HRC. In machining steels containing Ca-bearing mixed oxide inclusions, a reaction...
In this investigation the tribological characteristics of rapidly solidified Al–8Fe–4Ce with improved elevated temperature properties were studied. Such characteristics were compared with cast aluminum–silicon alloy and cast zinc–aluminum alloy. These materials included Al–13Si, Zn–35Al, Zn–35Al–Si, Zn–35Al–3.75Si and Zn–35Al–5.8Si. The wear rates of all materials were tested on a crossed-cylinders...
Polycrystalline cubic boron nitride (PCBN) cutting tools are widely used in the ultra-precision machining of stainless steel mould inserts for the injection moulding of optical lenses. During the machining of a spherical or an aspherical profile on a mould insert, the cutting speed reduces significantly to approximately 0 as the cutting tool is fed towards the centre of the machined profile. This...
Chip-form/chip-breakability and tool-wear/tool-life are two important aspects commonly considered in evaluating the performance of a machining process. The advent of new grooved tools with complex chip-groove geometry has required a better understanding of the curling behavior of the chip for effective curling and breaking of the chip. This paper presents a methodology for modeling chip-curl in machining...
This paper describes results from recent research projects aimed at understanding the failure mechanisms of diamond-coated carbides in machining fiberboard and particleboard. The objective of these projects is to bring about considerable improvements in tool life during the machining of wood and wood-based products through the application of hard coatings to the cutting edge. Machining experiments...
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