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In general practice, chip breakers are used to break chips in turning operations for chip disposal. However, chips of highly ductile materials such as low carbon steel or thin chips generated in finishing operations may not be broken easily with conventional chip breakers. They cause chip-jam and significant downtime in actual production. This paper proposes a novel approach where the generated chip is not broken but guided to overcome first the chip-jam and next to improve the efficiency of conventional turning operations by realizing the chip-pulling turning process. A novel cutting tool geometry is developed to suppress the chip's side curl to generate straight continuous chip flowing away from the cutting point and hence suppress the chip-jam. The proposed tool tip geometry contains 'guide grooves' engraved onto the rake face. The groove topography is optimized to control the chip flow robustly at various cutting conditions so that the cut chip can be guided for effective chip guidance. Continuously flowing guided chip is then pulled to reduce the friction force on the rake face to enhance the machinability. Experimental results show that the designed cutting tool geometry robustly controls the chip flow, and the chip-pulling turning process shows significant potential towards achieving higher machinability in hard turning. [ABSTRACT FROM AUTHOR]

The scope of this paper is to investigate the damping performance of metal swarfs in hollow structures and to compare its vibration suppression performance with existing granular damping technologies. The effectiveness in suppressing vibrations in a hollow aluminum beam using aluminum, mild steel and stainless steel swarfs is compared to that of rubber spheres. Performance is compared using swept sine wave across a range of amplitudes from 0.1 g to 10 g for both first and the second modes of the beam. Considerable vibration suppression is observed for both modes, and the effect of filler type on damping and natural frequency variation is presented. [ABSTRACT FROM AUTHOR]

The ideal coating for twist drills used to drill deep holes should have both a high hardness and a smooth surface. The latter property is considered to ease chip evacuation through the drill’s chip flutes and, therefore, reduces the risk of chip clogging and possible premature drill fractures. For this reason, diamond-like carbon (DLC) appears to be a well-suited type of coating. This paper presents the results of cutting tests using DLC-coated HSS and cobalt-HSS twist drills when drilling deep holes of diameter 1.5 mm into plain carbon steel. Their capability to extract swarf from the borehole as well as their tool lives were investigated and compared to uncoated and TiN- and MoS2-coated drills. Although the DLC-coated drills showed a very good swarf disposal capability, they did not exhibit a longer tool life when compared to off-the-shelf drills. [ABSTRACT FROM AUTHOR]

Abstract: Unlike straight turning, the effective cutting conditions and tool geometry in contour turning operations are continuously changing with changing workpiece profile. This causes a wide variation in chip flow during the operation. Unfavorable chip flow can cause scratch/damage the machined surface, and lead to tool failure due to chip build up at the cutting edge. This paper presents a new methodology to predict the chip side-flow angle for complex grooved tool inserts in contour turning operations as well as experimental validation. Computer program has been developed to apply the predictive model to any contour workpiece profile and the capability of the predictive program is also presented in this paper. [Copyright &y& Elsevier]

The problem of chip disposal has become more acute with the invention of high speed carbide and ceramic tools. An intruding protrusion in the normal flow path of the chip has been found to be an effective method for chip-control. A study of the variables of the mechanics of chip formation, viz. an analysis of cutting forces, chip thickness and dynamic shear strain in relation to the size and location of the intruding protrusion reveals some interesting characteristics. This paper attempts to present a physical explanation of such behaviours of the cutting variables. [ABSTRACT FROM AUTHOR]

In this paper, a workpiece–fixture layout verification approach with the application of frictional contact and chip removal effects using a finite-element technique, is presented. The objective of the proposed system is to overcome the deficiencies of existing fixture design approaches. Workpiece–fixture layout verification analysis is carried out for time varying machining forces to ensure that the workpiece will be held against the cutting and clamping forces. The chip removal effect and frictional contact between the workpiece and the fixture elements are taken into account using a material removal approach based on element death technique and nonlinear finite-element analysis. A case study illustrates the application of the proposed approach. [ABSTRACT FROM AUTHOR]

Inducing compressive stress on the machined surface is a desirable practice in ultra-precision metal cutting to improve the part quality. An important parameter to analyse the machining performance is the material flow stress, which plays a crucial role in the material deformation characteristics in machining. As the dimensions of the workpiece descend from macro to micro scale in metal forming, the flow stress reduces accordingly. Hence, based on the ‘surface model’ analogy developed for metal forming coupled with the crystal plasticity effect, an attempt has been made in this study to construct a flow stress model for ultra-precision machining process. While developing the model, for the first time, the size factor ( η, d/h o ) is introduced to incorporate the material ‘grain size effect’ in ultra-precision machining. The proposed model is validated with experimental results of Al6082 alloy of different grain sizes. Orthogonal turning experiments were conducted on an ultra-precision machine by utilizing the concept of ‘cutting edge radius effect’, which is identified as the relative tool sharpness ( RTS ) and quantified as the ratio of undeformed chip thickness ( h c ) to edge radius ( r n ). In this paper, the investigation on the material flow stress is carried out by considering the phenomenon of the shifting material flow separation (cutting) from primary deformation zone to material deformation (ploughing and rubbing) at tertiary deformation zone. The distribution of contact stresses along the tool rake and flank faces at the minimum value of RTS (h c /r n ) of 0.01 substantiates the ploughing effect (compressive stresses are induced into the machined layer) rather than chip separation. Moreover, the distinct variation of the machined surface quality and μ-chip morphology at the extreme low and high RTS conditions distinguishes the material ploughing effect from the cutting effect. Additionally, for the same RTS value, it is found that different grain materials (Cu and Mg alloy) exhibited variations in flow stress, chip morphology and surface quality. Therefore, material grain size is an influential factor for analysing machining performance with material flow stress at ultra-precision level. [ABSTRACT FROM AUTHOR]

The paper proposes a new technique of recycling metallic chips and presents the results of examination of the products thus obtained. The aim of the experiments was to recycle commercial purity (cp) titanium Grade 2 chips obtained by turning, and to produce a solid bulk material. The recycling was realized using a plastic working process. The titanium chips were first subjected to preliminary consolidation and then directly extruded using the KOBO process. The properties of the recycling final product were examined and compared with those of the as-received, solid cp-titanium Grade 2 (reference material). The recycling process yielded a well consolidated solid titanium rod with a diameter of 8 mm. The consolidation effect was high which was confirmed by the fact that only a small number of voids and discontinuities distributed randomly were observed. The final material had a homogeneous grained structure. The equiaxial grains observed on the transverse and longitudinal sections had similar sizes. The mechanical properties of the recycled material (estimated based on the results of microhardness measurements and uniaxial compression tests) were comparable with those of solid cp-titanium Grade 2. [ABSTRACT FROM AUTHOR]

The M 2 factor and other parameters often used in evaluating the beam quality of lasers are not sufficient. Based on the beam characteristics of semiconductor laser, the paper presents a new expression for the beam quality on semiconductor laser. The new beam quality factor can not only evaluate the beam quality of the semiconductor laser but also evaluate the beam quality of the semiconductor laser chips via collimating and focusing lenses. The results give us grounds to make the following conclusions: the new beam parameter product succeeds in its universality and adaptability in collimating and focusing lenses of a multi-emitter semiconductor laser made by stacking several signal emitter chips. [ABSTRACT FROM AUTHOR]

An easy-to-produce sawtooth chip is the main feature of the high-speed milling of hardened steel. In previous works, a theoretical geometric model was proposed for the sawtooth chip formation to predict the strain and strain rate in the shear band during chip formation; these properties are important when describing the deformation characteristics for the cutting of hardened steel materials. In the cutting process, however, the changes and distributions of stress and strain can hardly be obtained using a theoretical model. This paper modifies the conventional empirical Johnson–Cook constitutive equation by employing stress–strain curves at high temperature and a high strain rate obtained using split Hopkinson pressure bar technology and considering the negative strain rate effect and temperature effect of the material, especially for SKD11 (62 HRC) hardened steel. A thermo-mechanical coupled two-dimensional planar strain finite element model for the high-speed milling of SKD11 hardened steel with a modified Johnson–Cook constitutive equation is presented. The geometric characteristics of chip formation during the high-speed milling of SKD11 are predicted and the results are in good agreement with experimental results. Employing the modified finite element model, the stress and strain in the shear band during high-speed cutting are quantitatively analyzed and found to be in close agreement with the results of a theoretical model analysis. It is found that the cutting speed has a critical value at which the stress and strain reach a certain value and the distributions of stress and strain change in the shear band, resulting in the generation of a sawtooth chip. Moreover, the cutting force, cutting temperature, and selection of a coated tool are discussed according to results obtained with the modified finite element model. The cutting force and difference in temperature decrease while the temperature increases as the cutting speed increases. Compared with a TiAlN-coated tool, a TiSiN-coated tool performs better in cutting SKD11 hardened steel in terms of the cutting temperature. [ABSTRACT FROM AUTHOR]

Without proper chip evacuation, gun drills will fail under intense thermal and mechanical loading during deep hole drilling of high temperature superalloys like Inconel 718. In gundrilling, the efficiency in evacuating chips is governed by the geometry of gun drills that defines the hydraulic boundary conditions for coolant and chip flow. In this paper, we propose a novel computational fluid dynamics (CFD) model that is capable to simulate and quantify the chip transportation behavior under high pressure coolant for drill geometry optimization. This is demonstrated through a case study on improving the shoulder dub-off design of commercial gun drills, which have a high tendency in trapping chips at the hole bottom. A more effective design criterion for the shoulder dub-off is thus proposed. [ABSTRACT FROM AUTHOR]

The present paper deals with the mechanisms of chip formation during cutting operations. It deals with some experiments characterising the chip morphologies and microstructure chip investigations under high loadings. In this contribution, mechanisms of chip segmentation are presented. The effect of cutting conditions on cutting forces is treated. Consequently, the chip segmentation phenomenon was correlated to cutting forces evolutions. Also, an investigation on chip strain localisation is carried out. Numerical simulations dealing with chip formation and considering thermomechanical phenomena are also presented. Some numerical results related to chip formation based on the theory of strain gradient plasticity are also discussed. Moreover, the effect of machining system stiffness on chip segmentation is analysed. [ABSTRACT FROM AUTHOR]

Abstract: Magnox swarf contaminated with trace levels of Al metal is an important UK legacy waste originated from the fuel rod cladding system used in Magnox nuclear power stations. Composite cements made from Portland cement and blast furnace slag form a potential encapsulation matrix. However the high pH of this system causes the Al metal to corrode causing durability issues. Geopolymers derived from metakaolin are being investigated as an alternative encapsulation matrix for Magnox swarf waste and the corrosion kinetics and surface interactions of Al with metakaolin geopolymer are reported in this paper. It is shown that the pH of the geopolymer paste can be controlled by the selection of metakaolin and the sodium silicate solution used to form the geopolymer. A decrease in pH of the activation solution reduces corrosion of the Al metal and increases the stability of bayerite and gibbsite layers formed on the Al surface. The bayerite and gibbsite act as a passivation layer which inhibits further corrosion and mitigates H2 generation. The research shows that optimised metakaolin geopolymers have potential to be used to encapsulate legacy Magnox swarf wastes. [Copyright &y& Elsevier]

Abstract: Nowadays wood should be of principal sources of biomass. This wood is transformed into chips in order to increase automatic operations and to decrease the technical effort needed at the energy conversion plant. Typical high quality chips, which are used to feed small woodchip boilers, vary in size from 10 × 10 × 5 mm to 15 × 15 × 8 mm. Chips that are relatively square and flat are easily conveyed, augured, and fed into the system smoothly. We are mainly interested in the raw material of inferior quality. A disc chipper test bench was constructed in our laboratory to study the chipping process in cutting conditions which are similar to those used in the industry. The test bench design allows many factors to be varied include cutting speed, feed per tooth, cutting angles, anvil height and cutting direction. In this paper, we attempt to understand the effect of several factors on chip size distribution. Four feeds per tooth, four cutting angles, two sharpness angles and three cutting speeds were chosen to cut wet logs of oak and fir wood, while the other factors remained constant. The results are similar for both oak and fir. The proportion of small chips decreases when we increase the feed per tooth, the cutting angle and the sharpness angle, whereas it increases when the cutting speed is increased. The feed per tooth and the cutting speed have a linear effect on the variations in the size distribution, while the cutting angle has a non-linear effect on these variations. [ABSTRACT FROM AUTHOR]

This paper includes the findings of an experimental study on instabilities of the chip formation process during end milling of Ti6Al4V alloy and the influence of these instabilities on chatter formation. It has been identified that the chip formation process has a discrete nature, associated with the periodic shearing process during machining. The chip formed during machining of titanium alloy Ti6Al4V is found to be mainly with primary serrated teeth appearing in the main body of the chip. Secondary serrated teeth resulting from the coagulation of a certain number of primary serrated teeth also happen to appear at the free or constrained edge of the chip, especially when the system enters into chatter. In order to identify the interaction of these chip instabilities with the prominent natural vibration of the machine tools system components, the different mode frequencies of the vibrating components of the system have been identified using experimental and finite element modal analyses, and vibration responses during actual cutting have also been recorded using an online vibration monitoring system. The vibration signals in frequency domain (fast Fourier transform) have been analyzed to identify the chatter frequencies and the peak amplitude values. Chatter was found to occur at two dominant mode frequencies of the spindle. These mode frequencies at which chatter occurred have been compared with the chip serration frequencies in a wide cutting speed range for different conditions of cutting. it has been concluded from these findings that chatter occurs during end milling due to the resonance of the machine tools system component when the frequency of primary serrated teeth finis approximately equal to the "prominent natural frequency" modes of the system components, which are the two mode frequencies of the VMC machine spindle in this particular case. [ABSTRACT FROM AUTHOR]

Nanoparticles are used in industrial and domestic applications to control customized product properties. But there are several uncertainties concerning possible hazard to health safety and environment. Hence, it is necessary to search for methods to analyze the particle release from typical application processes. Based on a survey of commercial sanding machines, the relevant sanding process parameters were employed for the design of a miniature sanding test setup in a particle-free environment for the quantification of the nanoparticle release into air from surface coatings. The released particles were moved by a defined airflow to a fast mobility particle sizer and other aerosol measurement equipment to enable the determination of released particle numbers additionally to the particle size distribution. First, results revealed a strong impact of the coating material on the swarf mass and the number of released particles. [ABSTRACT FROM AUTHOR]

Machining swarf is a finely divided metal powder that is prone to spontaneous heating and, in some cases, spontaneous combustion. The fine particle size, large amount of particle surface area, and the presence of moisture all promote rapid oxidation. This hazard dramatically increases disposal costs for swarf and interferes with recycling efforts. A potential method for minimizing spontaneous heating and facilitating recycling of the swarf is to spray a fluid on the material that coats the particles and creates a barrier between the metal and oxygen. Surface coatings could be tested for their effects on the spontaneous heating potential of swarf by treating a sample of swarf with a fluid that would coat the particles, then monitoring its heating behavior. This paper describes the results of applying corrosion inhibitors and machining fluids to the swarf, and monitoring the spontaneous heating behavior using a testing method developed specifically for this purpose. The effects of different types of surfactants and the effects of surfactant concentration on the spontaneous heating of swarf are discussed. [ABSTRACT FROM AUTHOR]

Abstract: Crime scene investigators are often asked to examine swarf from break‐in sites and compare it with swarf found on a suspect. Occasionally, elemental composition of swarf from these two sources does not match. It is generally assumed that cutting metal does not induce changes in chemical composition. However, this study shows that, if a matrix contains iron, chromium, and nickel, composition of swarf produced from cutting the matrix with an abrasive saw may indeed alter. In this study, we cut a stainless steel sheet using a standard cutoff saw. Swarf was sorted and chemically analyzed by EDS/SEM, and the following relationships between chip morphology and modified composition were discovered: elongated chips remained unchanged; changes in the irregular chips appeared to be random, possibly because they are formed in a number of different ways; composition of spherical chips changed with size. [ABSTRACT FROM AUTHOR]

Diamond-coated wire (DCW) sawing of Si solar ingots generates swarf which is analyzed using micro-Raman spectroscopy. Two types of Si swarf are found. Particulate swarf is crystalline and shows residual compressive stress. Fibrillar swarf is amorphous and shows residual tensile stress. The origin of particulate, crystalline swarf is attributed to brittle machining, while the origin of fibrillar, amorphous swarf is attributed to ductile machining. Finite element modeling suggests that brittle machining resulting in particulate, crystalline swarf generation is initiated by sharp diamond microparticles. On the other hand, ductile machining resulting in fibrillar, amorphous swarf generation is caused by blunt diamond microparticles. Over the course of sawing, the ratio of crystalline/amorphous phase in swarf decreases, quantifying the average loss in sharpness of diamond microparticles. Thus, micro-Raman spectroscopy can be an effective analytical tool for quantifying and monitoring DCW sawing processes for Si solar ingots. [ABSTRACT FROM AUTHOR]

Si nanoparticles are produced from Si swarf which is a waste during slicing Si ingots to produce Si wafers for solar cell use. The beads mill method produces flake-like Si with scores of nanometers width from Si swarf. Subsequent photochemical dissolution with light longer than 560 nm wavelength in a 0.5 % HF solution results in sphere-shaped Si nanoparticles of 1-7 nm diameter. Si nanoparticles dispersed in ethanol show blue photoluminescence at ~400 nm (3.1 eV) under UV irradiation, indicating band-gap widening due to the quantum confinement effect. The band-gap energy of most of the Si nanoparticles is estimated to be 2.5-3.3 eV from the PL spectra, corresponding to the Si nanoparticle size of 1.9-3.2 nm. On the other hand, Si nanoparticles produced by immersion in the HF solution in the dark show much weaker blue photoluminescence. These results demonstrate that the Si dissolution reaction is greatly enhanced by photo-generated holes. [ABSTRACT FROM AUTHOR]

Stainless steel materials have been used in many fields such as automotive, food, medical, chemistry etc. by applying machining operations although they are categorized under a group of materials whose machinability is difficult due to high strength, low thermal conductivity and work hardening tendency during machining. It is possible that these materials can be machined by using various cutting fluids, but cutting fluids have disadvantages such as being harmful to the environment and health. In this study, it is intended that the minimum quantity lubrication method is applied by using commercial vegetarian cutting fluid and uncoated and TiN coated WC cutting tools during milling of AISI 304 (austenitic stainless steel) and AISI 420 (martensitic stainless steel) materials and the sustainable machining is realized. Milling operations will be repeated even by applying the dry machining for the purpose of being able to compare the results obtained from minimum quantity lubrication method. The workpiece surface roughness and chip forms were investigated. [ABSTRACT FROM AUTHOR]