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Binder jet 3D printing of ceramic materials is an additive manufacturing technology that enables the production of complex and multi-functional parts through the selective jet binding of precursor powder beds. The present study makes use of the 3D Sand Printing (3DSP) process to create moulds and cores in the casting industry. The use of the 3DSP components as functional parts in industrial production is limited due to the uncertainty associated with their mechanical properties, such as their permeability and thermal stability. Moreover, because of the porous nature of their printed structures, their mechanical properties are dispersed and rather difficult to reproduce. This study aims to characterise the impact of different printing parameters on the mechanical performance of printed parts. For this purpose, a specific device was made in order to assess the mechanical characteristics of samples printed via this technique. The effects of processing parameters such as the printing orientation and building direction on the compressive properties of the printed specimens have also been carefully studied. Microstructural analyses were performed to better understand the relationship between the 3DSP process and the mechanical properties of the components produced from it. The results show that the mechanical tests carried out significantly improve the property reproducibility of the samples made using this technique.

International audience; In this work, Al-Fe-Cr quasicrystal reinforced Al matrix composite was in-situ prepared by using selective laser melting from powder mixture of Al-Cu-Fe-Cr quasicrystal and pure Al. The effect of selective post-aging treatment on microstructure and mechanical properties were determined with focus on the metastable phases. The microstructural analysis, which was determined by X-ray diffraction and scanning electron microscopy, indicates that the Al-based intermetallic is precipitated from supersaturated α-Al after the aging process. Moreover, the compression tests were performed on the samples in form of dense and lattice structures (50% porosity). The elastic modules of dense and lattice structural samples reduce from 21.3 GPa and 4.4–14.6 GPa and 3.6 GPa by using a low cooling-rated aging process. After aging process, the compressive deformation behavior of dense part changes from elastic-plastic-fracture mode to elastic-plastic-densification mode. On the other hand, the failure mechanism of lattice structural sample changes from rapid-single-stage to slow-double-stage with an improvement of the strain at failure.

International audience; The friction of concrete on the interior skin of formworks takes place during the pouring of concrete into the molds. The present work investigates the friction of a granular material (i.e. fresh concrete) against metallic and polymeric surfaces. Interfacial behavior between different formulated concretes and formwork skins is characterized using a plane-plane tribometer dedicated to concrete tribometer. The formwork surface is measured before and after testing to quantify the wear issue. A Coulomb friction law is observed within the range of tested normal pressures. Tribological tests reveal that friction mechanisms depend on the interface properties. Two underlying mechanisms are hypothesized to explain the wearing of the formwork skin: a granulate-formwork solid-solid friction and a capillary-dominated friction.

International audience; In this research, Al-Fe-Cr quasicrystal (QC) reinforced Al-based metal matrix composites were in-situ manufactured by using selective laser melting (SLM) from the powder mixture. The parametrical optimization based on our previous work was performed with focus on laser scanning speed. From the optimized parameters, an almost dense (99.7%) free-crack sample was fabricated with an ultra-fine microstructure. A phase transition from decagonal QC Al65Cu25Fe10Cr5 to icosahedral QC Al91Fe4Cr5 could be observed as laser scanning speed decreases. Differential scanning calorimetry curves show that the QC phase is quiet stable until 500 °C. And then, the effects of annealing temperature on the microstructural and mechanical properties were determined. The results indicate that the recrystallization and growth behavior of α-Al grains could be prevented by QC particle during annealing. Furthermore, the growth of QC particle, which tends to form a porous structure, leads an improvement of Young modulus and decline of ductility.

The sticking of the concrete on metallic formworks during building construction generates many concrete wall defects. Several solutions have been proposed, among which surface lubrication and polymeric coatings are commonly applied. In this paper, the main functional signatures of a steel formwork skin and a polymeric coating were determined to understand their effect on the concrete sticking. The topographical, chemical and mechanical signatures of the surfaces were characterized at near-surface regions. The top of the steel formwork a 10 µm-thick layer is constituted of two oxides each one having specific tribological properties. Adding the polymeric coating on the formwork skin surface lowers its surface tension, which lowers the sticking by reducing the wettability. Moreover, the smaller roughness of the coating limits the susceptibility of mechanical anchoring. Nevertheless, scratch testing suggests a short durability of the polymeric coating due to its weak resistance to abrasion.

To functionalize a glassy polymer surface like the Polycarbonate (PC) several process are needed: milling, turning, polishing and a chemical attack process. These processes sign the surface on a large band frequency from mm-wavelength for the milling, to the nm-wavelength for the polishing and the chemical attack process, passing through the µm-wavelength for turning. However, the band frequency available with a measurement is limited by the size of the measure and the step scale of the sampling. In this paper, a method to characterize the evolution of the surface has been developed with Wavelet Transform approach. Surfaces of each step were measured with an interferometer under different magnifications (x5, x50, x115). Their signatures calculated with Mexican hat wavelet transform were lengthened by continuity between the different magnification. Some conditions of the continuity are needed as having the same size and the same step scale on the measurement by adding interpolation points for the lower magnification. The results show clear correlation between the multistage process signatures and the function printability evolution like optical, design and mechanical.

International audience; Concrete, a commonly used material in the construction industry, interacts with metallic surfaces such as formwork during pouring and reinforced bar during lifespan. Formworks are designed to minimize hardened concrete adherence in order to avoid wall defects after formwork removal. In opposite, reinforced bar designs aim at maximizing their adherence to concrete for optimizing the transmission of mechanical solicitations. The present review investigates the surface properties that govern bonding of freshly poured concrete onto metallic surfaces. Identifying the underlying mechanisms of adhesion highlighted the importance of substrate characteristics (roughness, composition), concrete curing and compaction), and interfacial additives (release agents, wetting). This paper addresses the basic requirements in designing a functional surface interacting with concrete and emphasizes today challenges.

Multiple parallel scratches are often analyzed to understand the material removal mechanisms due to abrasion. However, successive scratches with different orientations may represent better the conditions found in machining processes, such as honing and belt finishing. The objective of this work was to analyze the cutting forces and the phenomena of material removal due to abrasion, arising from angular scratches in low carbon steel. Experimental and numerical techniques were considered. In both, analyses considered the presence of an initial set of parallel scratches, followed by a second set of scratches with different orientations (10, 20 or 30°) with respect to the previous one. The cutting action was performed by a tool representing an abrasive particle, which had a cono-spherical geometry with 235 µm tip radius and 30° apex angle. The cutting settings were: 50 m/min scratch velocity and 100 µm depth of cut. In the experimental part, scratches were conducted using a shaper machine tool equipped with a tungsten carbide (WC-Co) stylus. Tests were conducted on a Kistler platform, which allowed force measurement. Surfaces were later analyzed with an optical profilometer. The numerical simulations considered a ductile damage model with element deletion to provide the material removal during the scratches. Experimental and numerical results showed that the angle affects the cutting forces, especially when one scratch crosses a previously scratched region. The 20° case was the most critical, especially in terms of the cutting forces, due to the accentuated material strain-hardening for this condition. Likewise, this fact was corroborated by numerical results, which indicated a higher energy necessary to plastic deformation, and a reduced material removal at 20°.

Various applications require surfaces with anti-fingerprint properties. This article reviews the surface properties that govern the fingerprinting process. The achievement of surfaces free of finge...

International audience; Honing is a manufacturing process which uses friction and abrasion mechanisms at a reduced velocity to print a multiscale and anisotropic texture on the liner surface of automotive engines. It enables to enhance the functional performances of a ring-pack system. However, industrial honing basically generates cross-hatched rectilinear textures. This paper proposes new surface textures, generatedby an innovative honing prototype machine, with original patterns (circles and ellipses) at different size and aspect ratio. Then, the friction performances of each generated surface are evaluated using a reciprocating ring–liner tribometer and compared with industrial helical slide honed (HSH) texture. The results show that ellipse patterns oriented at ring sliding direction contribute the most to reduce the friction coefficient.

In this work, a novel tungsten steel was in-situ prepared using selective laser melting (SLM) and hot isotropic pressing (HIPing). The sample is firstly prepared by SLM from powder mixture of maraging steel and WC for the net-shaped manufacturing requirement. Then, the effects of HIPing on microstructure evolution and mechanical properties of SLMed WC/maraging steel composite were investigated with focus on in-situ reaction. The as-SLMed sample presents a composite structure of γ (Fe, Ni) (austenite) and WC, which transits into α-Fe (ferrite and martensite) matrix with a large amount of Fe(Ni)–W–C η phase precipitates after HIPing. The η phase, which shows two morphologies (sub-micro and nano scales), locates mainly in grain boundary and inner-grain of α-Fe, respectively. The interfaces between η, WC and α-Fe were determined using transition electron microscopy from barely existing partial melted WC. A stable graded multi-scaled structure appears between partial melted WC and matrix. After the HIPing process, the ultimate tensile strength and yield strength increase from 980 MPa to 561 MPa–1470 MPa and 1025 MPa, respectively, with a slight decrement in elongation from 7% to 6%.

International audience; Fe-Ni-Si soft magnetic parts, using Ni coated high silicon steel powder, were manufactured by selective laser melting process. The type of defect changes from porosity to cracks and the relative density increases, from 50% to 99%, with the decreasing laser scanning speed. The microstructural analyses indicate that the low laser scanning speed fully melted the nickel coating and high-silicon steel core. The EBSD study showed that the separated island and lamellar mesostructures appeared on the top and side view respectively. Moreover, no apparent texture were observed. The magnetization saturation of SLM processed sample decreased, as the laser scanning speed was increased. Consequently, the magnetic properties of SLM processed Fe-Ni-Si alloy also showed anisotropic feature in building and scanning directions, which can be attributed to their different mesostructure.

International audience; The molten metal flow under low-pressure filling was investigated both experimentally and numerically insidesand molds with different cross sections and different pressure ramps. The proposed fluid dynamics simulationpredicts quantitatively the observed filling oscillations. An analytical model is developed to link the over-heightwith the geometrical restriction and the pressure ramp. The calculated over-height is proportional to the rampand non-linearly impacted by the section change as confirmed by the experimental results.

Cylinder liner surface has a great influence on frictional and wear performances of combustion engines during the running-in period. Two surface texture anisotropies produced by plateau honing (PH) and helical slide honing (HSH) processes (which consist of 50° and 130° cross-hatched grooves, respectively) are commonly used in automotive industry for thermal combustion engine cylinder liners. They are generated by a three stages process. The first stage, rough honing, removes enough material to obtain the desired cylindricity. The second step, finish honing, generates the honed texture which consists of grooves with a specific cross-hatch angle. The third stage permits to reduce the surface peaks and therefore allows varying plateau superficial roughness amplitude. This paper is devoted to studying the influence of respectively smoothness and plateauness on honed surface wear and friction performances during running-in. For that, HSH and PH textures are generated using different final honing stage durations in order to obtain different levels of surface peak clipping. Then, friction, wear and surface topography evolution were analyzed during running-in tests on a reciprocating ring-liner tribometer under mixed lubrication regime. The results show that the superficial surface roughness generated by helical slide honing has a very low contribution into friction. This is promising for the honing process optimization, in which the third stage can be significantly reduced or avoided.

Surface texturation at micro- and meso-scales plays an important role in applications where cosmetic, aesthetic and self-cleaning functionalities are specified. This research paper deals with a multiscale surface, in which texturing and texture have a larger influence because they are scaled differently. The experimental approach highlights the important effect of texture and texturing on the anti-fingerprinting performance rated in term of surface wettability. We examine first, in detail, the wetting response of surfaces textured on aluminum alloy 6063 plates using nano-peening with various processing parameters. Roughness was measured by atomic force microscopy (AFM) and interferometry. Surface wettability was quantified using the sessile drop method. The calculation takes into account the wetting behavior of the textured surfaces at different scales. Correlations were made between the surface roughness and its functionality.

International audience; Nowadays buildings construction is performed by pouring concrete into molds called formworks that are usually prefabricated metallic modules. Defects such as stripping may possibly form during the removal of the formwork if the interfacial bonding between the concrete and the formwork is high. Making use of a new pull-off tensile test designed in our laboratory, a correlation has been established between the formwork surface functional signatures and its adherence propensity to concrete. The originality of this near-to-surface test was to characterizethe concrete-to-formwork adherence by measuring the required force to pull the concrete from the formwork surface. The design of the test coupon was validated by finite element analysis that proves the small deformation of the tested formwork specimen under the tensile loading and the homogeneity of the applied tensile stress at the interface. The interfacial bonding to concrete has been compared between bare and coated formwork. Both metallic and polymer coatings have been studied. The analyses of the pull-off test results enabled us to understand the bonding mechanisms at the concrete-coating interfaces. The pull-off tensile test was proven capable of ranking formwork coatings according to their adherence to concrete.

In this work, almost dense (over 99.8 %) Ti-Mo alloy samples were manufactured by directed energy deposition (DED) from a mixture of pure Ti and pure Mo (7.5 wt.%) powders. As a consequence of thermal accumulation and in-situ heat treating during the DED process, as-deposited samples present a graded microstructure along the building direction along with a phase transition from hcp-α Ti to bbc-β Ti. Mechanical properties were determined by tensile tests from flat samples harvested at different altitude positions. As altitude increases from the base plate, yield strength decreases from 681 MPa to 579 MPa and ultimate tensile strength from 791 MPa to 686 MPa. Elongation of the as-deposited material increases from 10 % to 25 % while the Young’s modulus keeps a low value of 105 GPa for the entire DEDed sample.

Current demands of higher damage-tolerance in the Aerospace industry resulted in resurging interest in β , or near β , titanium alloys. The combination of attractive properties of this class of alloys also led to the consideration of beta alloys for castings. Such alloys, however, are more difficult to cut than α - β titanium alloys due to their limited ability to work harden and the effect of β -stabilizers on ductility. These factors affect failure modes and active wear mechanisms of cutting inserts. This paper investigates some of the wear modes exhibited by WC-Co inserts when end milling the α near- β alloy Ti- x . In addition to being of near- β composition, this alloy is characterized by a fine sized microstructure (range of 1−5 μ m). The study focuses on SEM and EDS observations of the wear patterns exhibited by two groups of inserts. The first is uncoated WC-Co, whereas the second is coated with multi layers of TiAlN. The results of this post-mortem study are compared to wear patterns, observed under identical conditions, while milling the α - β alloy Ti6Al4V. Results show that inserts used in machining the Ti- x alloy exhibit wear modes that contrast those exhibited when machining Ti64. The paper discusses factors leading to such occurrences and studies the influence of the alloy microstructure on tool effectiveness and failure modes.

Dry machining is being recognized as ecological machining due to its less environmental impact and manufacturing cost. However, the choice of dry machining is mainly influenced by the workpiece material properties, machining operation and cutting conditions. The recent emergence of austempered ductile iron (ADI) can be considered a significant economic advantage to the increasing industrial demand for cost- and weight-efficient materials. However, due to its microstructure-induced inherent properties, ADI is considered hard-to-machine material. Thus, the dry drilling of ADI is investigated in this paper. The ADI material used in the present study is produced using an innovative process route for near net shape casting production. Drilling experiments are conducted on a DMU80P Deckel Maho five-axis machining centre using PVD-coated carbide tools under dry cutting environment. The dry drilling of ADI under different cutting conditions is evaluated in terms of specific cutting force and tool wear analysis. The influence of cutting conditions on chip morphology and surface roughness is also investigated. The experimental results revealed that the combination of the low feed rate and higher cutting speed leads to the higher mechanical and thermal loads on the tool's cutting edge, resulting in higher specific cutting force values. This behaviour is further supported by the chip morphology analysis, which revealed the formation of segmented chips at higher cutting speed with segment spacing increase with an increase in feed rate. Depending upon the cutting parameters, different modes of tool failures including crater wear, flank wear, chipping, breakage and built-up edge were observed. Surface roughness analysis revealed the influence of tool wear and chip morphology on the machined surface finish.

To study the effect of a rough texture on tactile perception, the human finger was equipped with a sensor very sensitive to the vibration generated during a touch test. The range of vibrational frequencies is well consistent with the frequency of Pacini. To analyze the vibrational characteristics of the human finger under different experimental conditions, our experimental results are based on two quantitative parameters: a parameter which measures the amplitude of the average vibration level L v (dB), and a parameter related to the spatial resolution of the human finger and which is identified as the characteristic wavelength corresponding to the maximum of the power spectral density (PSD) in the Pacinian frequency band (1–500 Hz). For a constant normal force, the parameter L v (dB) allowed us to compare the received vibration with the finger as a function of the nature of the surface scanned, the scanning speed, the amplitude and wavelength of roughness. Depending on the scan rate used, it was possible to identify the wavelength filter of the human finger, which can be defined as the ratio of the scanning speed to the frequency corresponding to the maximum PSD: λ f (mm)= v/ω . This result allowed us to set a lower speed 10 mm/s for better spatial resolution that can be achieved in the case of abrasive paper: 0.2 mm. To understand the role of texture morphology on finger deformation and vibration, a 3D contact model has been developed. Assuming the finger elastic deformation, the results of the contact model show the way the roughness is printed on the human fingerprint and the effect it produces on the contact pressure and give Von Mises stress for various textures.

The functional texture of polished edge of an ophthalmic lens is controlled by the characteristics of the finishing process by which the surface edge is produced. In order to assess the selection of edge surface finish for production purposes, tribo-acoustic sensor that mimics human sensory perception is used. The assumptions underlying the methods are that certain sounds, such as the old and surprisingly sensitive fingernail test, have a close association with somatosensory precepts. In this paper, an existing sensor was modified and adapted, via biomimetic knowledge transfer of sensory perception in humans (touch perception). If an artificial finger with smooth surface slides over an edge of polished lenses, the friction induced micro-wear traces, waviness (termed macro-roughness) and the form (hills and valleys) population varies. In touch perception tests, we showed that the texture stimulus (friction noise) delivered to artificial finger depends on the edge finish quality. The results also revealed that the effects of the edge finish on touch are frequency dependent—only sounds with the same frequency as the vibrotactile frequency enhanced tactile detection. These results demonstrate that texture finish influences touch perception in highly systematic way and suggest that similar coding of wear traces produce by polishing may underlie the processing information of quality assessment and selection of the edge ophthalmic glass.

International audience; The texture change during running-in alters the performance and efficiency of a tribo-mechanical system. During mass production of cylinder liners, a final finishing stage known as ''plateau honing'' is commonly added to reduce the running-in wear process of the liner surface. The majority of researchers think that this operation improves the engine efficiency and decreases oil consumption. It was believed that there are close links between the surface topography of honed cylinders change and their wear resistance during running-in. However, these interactions have not yet been established. Some running-in wear models were developed in the open literature to predict topographical surface changes without considering the running-in conditions. The present paper thus investigates the various aspects of the wear modeling that caused running- in problems in honed surfaces and its implications on ring-pack friction performance. To illustrate this, plateau honing experiments under different conditions were first carried out on an instrumented vertical honing machine. The plateau honing experiments characterize the surface modifications during running-in wear of cast-iron engine bores using advanced characterization method. Based on the experimental evidence, a running-in wear model was developed. Finally, a numerical extension of the developed model was applied to solve the Reynolds equation by taking into account the real surface topographies of the engine bore. This enables us to predict realistic friction performance within the cylinder ring-pack tribosystem.

The sand mold 3D printing technologies enable the manufacturing of molds with great dimensional accuracy. However, the roughness of as-cast components is higher when cast in a 3D printed mold rather than in a traditional sand mold. Coating the inner cavity is an efficient solution but can be costly and, in the narrowest cavities, not achievable. Finding a procedure to reduce the as-cast roughness without coating would ease the casting procedures. In the present work, surface analysis of ZE41 magnesium alloy is presented after being cast in 3D printed furan sand molds without coating using the low-pressure casting process. The molten metal temperature was measured during casting at different positions along the cast cavity. The as-cast surface roughness was correlated to the molten metal temperature and solid fraction at the time of contact against the sand mold surface.

International audience; Honing is an industrial alternative of internal grinding for finishing large-diameter bores of internal combustion engine cylinders. This paper introduces a hybrid approach for a multi-scale analysis of surface finish in abrasive honing. The methodology is based on morphological identification of scratch pattern of manufactured surfaces, produced at various honing conditions, and their 2D continuous wavelet decomposition. The activated abrasion mechanisms were then discussed based on quantitative analysis of geometrical scratch pattern and multi-scale surface modifications of honing signature. Results show clearly that honed surface finish is primarily controlled by the size and the geometry of abrasive grains (i.e. wear of abrasive sticks). Since the abrasive is in continuous balanced contact with the work in honing operating at constant-force grinding, there is less deflection of the work. Moreover, it appears that honing signature shows a multi-scale fractal structure along the observation scales. This makes it possible to identify an optimal honing route preserving honing sticks abrasiveness and increasing their texturing capacity to confer high volume of oil retention at honed surfacefinish.

International audience; Skin in biological systems, including humans, perform several synchronized tasks (mechanical, protec-tive, tactile, sensory, etc.). Tribological function is among skin tasks and may determine the survivabilityof many species. Cross comparison of tribological functional traits of skin of different species, albeit interesting, is rarely encountered, if at all exists, in tribology literature. One interesting example is that of snake and human skins. This skin pair was the subject of many studies for transdermal drug delivery. Results in that context concluded that snakeskin is highly compatible with human skin despite apparent differences in surface structure and topology. The reported compatibility raises curious question ofwhether there exists frictional or tribological compatibility between the two skins and if so, under what conditions, and which context. In this work, we report, for the first time in open literature, results of a comprehensive comparative investigation of shed snakeskin and human skin with respect to tribological behaviour. To this end, we compared the frictional response of shed skin obtained from P. regius and human skin from different anatomical sites, gender, and age. The results imply that, in essence, the mechanisms governing the friction response of human skin are common to snake skin despite difference in chemical composition and apparent surface structure. In particular, both skin types display sensitivity to hysteresis and adhesive dissipation. Human skin, however, being more sensitive to hysteresis than snakeskin. One interesting finding of the study is that the ratio of the coefficients of friction for snake and human skin, when sliding on the same interface, depends on the reciprocal of their respective moduli of elasticity.

The present paper investigates the simulation analysis of simultaneous mold filling and solidification of ductile iron casting in a permanent mold by virtue of its thermal characteristics. Thermal analysis was performed to determine the solidification behavior and nature of alloy of the melt during its solidification. It revealed the variation in the nature of alloy due to the variations in eutectic freezing and carbon equivalent of the melt. The obtained thermal parameters from the thermal analysis were further used for the casting simulation of the melt. The simulation results show a progressive solidification behavior of the casting. There is a significant decrease in the overall heat transfer coefficient with time during the solidification process. The simulation results were further verified experimentally. The experimental results show porosity defects at the top section of the casting. Two distinct zones (center and outer) were observed on the produced samples based on the average graphite nodule counts and average graphite nodule size.

International audience; Multistage abrasive finishing processes (grinding, polishing, honing, etc.) are commonly used to produce the geometrical properties of a surface to meet its technical functionalities in the operating characteristics of contacting parts in friction, relating to their durability and reliability (running-in performance, wear resistance, load-carrying capacity, etc.). Coarse abrasive grits followed progressively finer ones are used, which leads to a multiscale stratified surface texture. In this article, a numerical model of elastohydrodynamic (EHD) contact coupled to a multiscale surface texture model was developed that allows tracking the scale effect of surface features and their interactions on friction performance and lubricant flow under hydrodynamic lubrication conditions. Because the simulation model has as an input the surface topography and to overcome the variability in surface finish formation, textured surfaces at different stages of the finishing process were simulated (virtual texturing method). Surface topography can be decomposed into two principal components: superficial roughness and valleys. Superficial roughness was modeled using a fractal model and a scaling factor was introduced to model valley patterns. The results show the relationship between friction and surface scales.

A cylinder liner possesses fairly intricate surface requirements due to its complicated functions. It needs to provide adequate surface roughness to resist wear as well as to store and retain lubricants during high temperatures. The liner surface texture is anisotropic, produced by the honing process, with resultant deep visible scratches left on it [1] . The prominence of the honing grooves observed suggests that surface texture significantly affects ring-pack performance, although this effect is not clearly understood. In this paper, a numerical model was developed to investigate the effects of groove characteristics on the lubrication condition and friction at the interface between the piston ring and cylinder liner. This model aims to solve the average Reynolds equation, which depends on the real surface topographies of the cylinder liner, and describes the influence of surface irregularities on the lubricant flow under hydrodynamic lubrication conditions, considering lubricant film rupture and cavitations. Numerical results help to determine the optimum lateral groove characteristics to reduce friction and then noxious emissions.

Machinability study on drilling of green austempered ductile iron (ADI) grade was conducted using a TiAlN-coated tungsten carbide drill. The green ADI grade was produced by a novel manufacturing technology known as continuous casting-heat treatment technology to save energy and time in foundry. However, in spite of good combination of strength, toughness and enhanced wear resistance, the microstructural properties of ADI sometimes lead to machinability issues. The effect of cutting parameters on cutting force coefficients, chip morphology, and surface integrity of the drilled surface were discussed. Results showed that the strength properties of novel ADI are comparable to that of ASTM grade 1 ADI, whereas percent elongation is comparable to that of ASTM grade 2 ADI. Results obtained also showed that the combined effect of cutting speed at its higher values and feed rate at its lower values can result in increasing cutting force coefficients and specific cutting energy. At higher cutting speed, hardness values increases at the subsurface layer of the drilled surface due to plastic deformation.

A cutting induced-damage process involving matrix cracking, fiber fracture and interlaminar delamination often occurs when machining composite materials. Compared to metals, relatively little research has been carried out in this topic. Generally, damage mechanisms in machining composites include four types of wear modes: transverse matrix cracking, fiber–matrix interface debonding, fiber rupture and inter-ply delamination. The surface quality plays an important role in the improvement of fatigue life and wear resistance of composite components. In the case of high speed machining composite materials, the surface quality of the finished product may be improved by modifying the machining parameters. Due to the complex nature of this process, we focus here on the effect of cutting parameters on surface damage of the machined component and thus wear resistance. The later has been predicted using dynamic explicit finite element method. In this investigation a progressive failure analysis has been adopted for analysing damage process within the fiber reinforced polymer (FRP) workpiece. After damage is detected, selective stiffness degradation is applied to the workpiece material. It has been shown in this study that matrix cracking and interface shearing occur first, followed by wear of fibers. The damage progression in the matrix and interface occurs in parallel directions to the fiber axis. A random growth of fiber fracture has been observed and mainly localized in a plane with a specific direction. The effect of fiber orientation on wear resistance of the composite structure and cutting induced damage process has been investigated. Damage progression was found to be strongly influenced by the fiber orientation of the FRP composite.

This paper deals with the relationship between wear resistance of diamond tools and the emission of particles while machining metal matrix composites reinforced with silicon carbides particles. Metal matrix composite is a difficult to machine material. Due to abrasive action of the reinforcement, diamond tool seems to be the more appropriate tool. Nanostructured diamond coated tool and various PCD tools were used in this study to investigate their wear resistance and their impact on particle generation. Bar turning tests were conducted on aluminum alloy reinforced with different level of particles (0, 15, 25 and 35% of SiCp). Airborne particles were measured in situ with a spectrometer and sorted in 15 size channels each six seconds. Morphology of chip and tool rake face was observed. The quantity of particles and the metrology of the airborne aerosol were linked for each tool and each level of reinforcement to tool wear resistance and chip morphology. The increase of particle size is associated to extraction of SiC particles from chip on shear plane and form workpiece material, whereas the increase of quantity of particles corresponds to diamond grains removed due to abrasive wear mode. Tool behaviour had important effect on aerosol metrology and on its consequences on airway if inhaled.

Coolants and lubricants for machining can improve the machinability of the workpiece, increase productivity, and extend tool life by reducing tool wear. However, for environmental and economic reasons, recent research in industry and academia has sought ways to reduce the use of machining fluids. This paper reports the use of dry and minimum quantity lubrication (MQL) to drill austempered ductile iron (ADI), a new class of materials used for light weight automotive components like connecting rods and crankshafts. In this study, ADI is produced by a novel processing technique known as continuous casting-heat treatment process. The novel technique is developed by the integration of casting (in die casting) and heat treatment processes in the foundry to save energy and time. This paper deals with an experimental investigation on the role of MQL drilling on the cutting forces, tool wear and surface roughness of newly produced ADI at industrial speed-feed combinations by TiAlN-coated tungsten carbide tool. MQL drilling, performance is then compared with the dry and conventional drilling process under the same experimental conditions and environment. The results include significant reduction in tool wear, cutting forces and surface roughness by MQL drilling, mainly through reduction in the cutting zone temperature.

In mass production of cylinder liners, the industrial honing involves multistage abrasive finishing processes, using at first a coarse abrasive stones, and then progressively finer grades, so that a very structured surface of liner is produced. A useful method in diagnosis of industrial honing is presented. It is based on the use of multiscale surface analysis to study the progress of abrasive wear mechanisms which occurred in honing while it was in operation. Thus, the examination of generated surface components by honing to detect the topographical signatures, and especially, signatures of surface in the right scale, is an important part of quality assessment in cylinder liner production.

A consistent increase in demand for special tools designed to enhance an efficient honing of engine cylinder bores is observed. Metallic Bonded Diamond Stones (Dia-M) are more and more used for their wear resistance and their high tool life. However, the hardness of this Metallic Bond leads to the degradation of the honed surface aspect by the formation of smudgy grooves edges (blechmantel). This torn and folded metal affects the required functional performances of the cylinder bore. In this study, two new diamond coated abrasive stones with Vitrified and Resinoid Bonds (respectively Dia-V and Dia-R) are tested and compared to the Dia-M sticks. The influences of bond material on the honing reliability are studied in terms of honed surface aspect, material removal rate and wear properties. Results reveal that the stiffness and the openness structure of the Resinoid Bond leads to a better trade off between surface aspect and tool life.

In this work, an attempt is made to develop a novel approach based on the concept of process signatures to investigate the correlation of the quality of manufactured surface and the process of its generation which is independent to manufacturing conditions. The process signature is the multiscale modifications of surface topography, which depicts the essential changes of the surface state produced on the original surface after abrasive machining. An advanced signal processing technique, the continuous wavelets transform is used to identify the multiscale transfer function of the process which represents the amount of surface modifications. The applicability of this methodology is demonstrated by several practical examples. It is shown that the signature is strongly influenced by abrasive dispersity and granulometry, process induced modes of deformation. The work demonstrates also that the process signatures respond in a predictable fashion to changes in process variables and combinations of stage.

International audience; This paper addresses the effects of bonds and grains of abrasive tools on the edge aspect of ground glass surface. Diamond grains and silicon carbide (SiC) grains combined with two bond types, i.e., resin and metal, were considered for this study. The surface edge characteristics were characterized using scanning electron microscope (SEM) and interferometer observations. In particular, the spectrum of arithmetic mean was investigated for distinguishing the different scales of analysis. Experimental results showed that the grinding forces vary sensitively with bond type and wheel velocity. Using diamond grains' wheel, it was found that roughness level obtained with metallic bond is lower than that obtained with resin bond. However, using a resin-bonded wheel, two mechanisms of material removal were revealed according to grains' type. (i) A partial ductile regime, i.e., ductile streaks and brittle fracture, obtained with diamond grains, and (ii) a fully ductile regime obtained with SiC grains. Thus, it was found that ground surface obtained using SiC grains' wheel has a better roughness than that obtained using diamond grains wheel. Besides, SiC grains seem to lead to more marked streaks and form defects.

This paper reports on experimental test program to study the effect of the coating structure associated with the machining of metal matrix composite (MMC). The composite materials investigated were respectively a 5%, 15% and 25% by volume SiC particle-reinforced A2009 aluminum alloy. The machining of these materials is indeed very difficult due to the abrasive effect of reinforcement upon the cutting tool. In this work, the ability of coated tools with nanostructured CVD diamond coatings to cut MMC components is discussed during dry machining. The performances of three different structures of CVD diamond coating are then considered using classical parameters (cutting forces, tool life, residual stress) and innovative criterion such as dust emission. The results show that in spite of their similar thickness, the coatings have various performances. The tool life was varied in a ratio of 1 to 6 irrespectively to the cumulative wear evolution which was monitored in situ with a power measurement and quantified ex situ using a white light interferometer.

With the increasing use of ultra-hard abrasives and the introduction of more powerful and rigid machines, honing process is spreading its performances. In industrial honing of cylinder liners for internal combustion engines, the degree of penetration that Metallic Bonded Diamond (MBD) abrasive stones have experienced compared to conventional Vitrified Bonded Silicon Carbide (VBSC) tools is obvious. The long tool life of metal bonded diamond sticks is however balanced by its main role in producing torn and folded metal without cutting-effect finish. To simultaneously reduce folding and remove the stock with improved stone life, an experimental investigation is reported on the process variability in finish honing behavior due to stone inconsistency and nature of its properties. We consider the achievable performances by finish honing of cast iron liners with a new abrasive stone. This superabrasive consists of micro-sized diamond abrasives which are bonded with vitrified bond (VBD). By selection of finer grit abrasive while honing with VBD tool, conditions could be created that gave a cutting-effect finish to the diamond honing and minimized the folding over.

This work attempts to examine the mechanisms of fatigue when cracks synergetically initiate in more than one site at the specimen surface. The metal matrix composites (MMC) i.e. silicon carbide particles reinforced aluminium matrix composites (Al/SiC p –MMC), seem to be good candidates to accelerate fatigue failures following multi surface initiations (MSI). Closure effects of MSI mechanisms on the variation of fatigue behaviour are explored for various stress states. Experiments were carried out using non pre-treated and pre-treated specimens. Using an Equivalent Ellipse Method (EEM), it is shown that the aspect of surface finish of specimen plays an important role on crack growth. Scanning Electron Microscope (SEM) inspections have lead to distinguishing the initiation regions from propagation regions and final separation regions. It is also revealed that the total lifetime of specimens is sensitive to heat treatment. Moreover, it is found that the appearance of MSI in cycled materials is more probable at high level of fatigue loads.

Thanks to its mechanical and tribological performances compared to the other types of steel, cast iron has been more and more used. Ductile iron is used for several structural applications, particularly when both rigidity and good machinability are required. The second largest area of application of ductile iron is the automobile industry thanks to its lower density, good wear resistance and its low friction coefficient. In this work an experimental wear test emphasizes the role of graphite in the tribological behaviour of a nodular cast iron. Correlation between tribological parameters and wear mechanisms has been investigated. Particularly, the effect of normal load and attack angle of conical indenter on the wear mechanisms has been checked out. The numerical model has also been investigated in order to better understand the tribological graphitic behaviour. It also highlights the correlation between tribological parameters and wear mechanisms.

Belt finishing with different particles size results mainly in different thickness of the total mechanically deformed layer and surface profile projections that depend, to a great extent, on the change in the mechanism of wear. Such a modification often represents a transition in the nature of physical mechanisms (cutting, plowing or sliding), leading to a concomitant change in the rate of material removal. Transition in wear mechanism can also be associated with a change in the abrasiveness properties of the abrasive coated belts. This paper outlines a method by which these transitional regimes can be illustrated graphically on plots of grit size against abrasion energy or applied pressure in connection with the produced surface state (i.e. roughness) for a given wear rate. It is supported by numerous experiments which show that the quality of the finished surfaces is dependent on the wear state of the coated abrasive belt. The “maps” showing wear rates and mechanisms suggest the existence of promising way for increasing the efficiency of abrasive technological processes.

Progressive failure of unidirectional glass fiber-reinforced polymer composites (FRP) was studied using finite element analysis in orthogonal machining. Chip formation process and damage modes such as matrix cracking, fiber–matrix debonding and fiber breaking were modelled by degrading the material properties. Damage analysis was carried out using Hashin, Maximum stress and Hoffman failure criteria. After damage was detected, selective stiffness degradation was applied to the workpiece material. The objective of this study is to better understand the chip formation process and to analyse the cutting-induced damage from initiation stage until complete chip formation. The effect of the fiber orientation on cutting forces and sub-surface damage was investigated with different failure criteria. The results were addressed in terms of cutting forces evolution and damage progression in the composite structure during machining. It was demonstrated that the use of the stiffness degradation concept with the appropriate failure criterion responds potentially in a predictable fashion to changes in chip formation process for machining of FRPs.

Cobalt-base materials are widely used as weld hardfacing deposits in hot forging industry. When the cobalt-base hardfacing alloys are deposited using the MIG welding process, the weld energy with the sequences of the welding are at least the two important variables which influence the behaviour of most hardfacing deposits in service conditions. The purpose of this work is to consider their role in connection with the work-hardening ability of Stellite 21 weld hardfacing deposits. An experimental parametric study of several welded-layers related to their friction behaviour is performed. The friction-induced work hardening (FIWH) ability of Stellite 21 deposits is considered to assess the influence of the two welding parameters. Results show that depending on the used welding sequences, the amount of the applied energy determines the dilution rates across the thickness of the deposits. Microscopic observations at the friction surface confirm that the highest FIWH rates, owing to stacking faults brought out, increase the wear resistance.

We study failure of coated carbide tools due to thermal loading. The study emphasizes the role of thermo–physical properties of the tool material in enhancing wear resistance of the tool. We show that heat conduction in the tool active zone is a function of the so called thermodynamic forces. Due to coupling between thermal and mechanical states within the active volume of the tool material, three distinct thermal zones evolve. The first, which is located on the rake face close to the primary shear zone, exhibits a severe drop in its ability of thermal conduction. The second zone, located at the tool tip is characterized by a predominant thermo mechanically induced conduction anisotropy. The anisotropic behaviour, forces heat to partially flow toward the thermally dead zone whence contributing to the intense thermal energy accumulation within the affected material volume. The third zone is one where the thermally triggered degradation of conduction takes place. Heat flow, in light of the existence of these zones, evolves such that, the tip of the tool will be almost thermally congested. The congestion is thought to be the mechanism that renders the energy needed to activate wear mechanisms available.

High speed dry machining presents considerable technical challenges to the manufacturing community. This is because metal removal without using cutting fluids, while environmentally benign, implements an aggressive environment that affects the integrity of the cutting tool materials. Within such an environment, most of the operative wear mechanisms have their roots in thermal activation. As such, the efficiency of heat removal at the tool-workpiece interface assumes considerable importance. Efficiency of heat removal, on the other hand is a direct function of thermal transport properties of the tool material and the manner of their variation under realistic operation conditions. As such, this work investigates the influence of thermal conduction on mass attrition of cutting tools. The study scours the thermal environment in machining an aeronautical grade alloy, α–β titanium Ti-6242S, in dry mode. The analysis of thermal conduction conditions of a tungesten carbide cutting insert reveals that due to the influence of thermodynamic forces, thermal conduction anisotropy may arise. This leads to the existence of three primary zones within the active zone of the tool. The first, which is close to the primary shear zone of the work piece, and is located on the rake face, is completely thermally blocked. The second zone which is located at the tool tip is characterized by a predominant anisotropy in conduction. The anisotropic behaviour, allows heat in the vertical direction, toward, the thermally dead zone. The third zone is one where the anisotropy is not as pronounced. Heat flow, in light of the existence of these zones, evolves such that, the tip of the tool will be almost thermally congested. The congestion makes available the energy needed to activate wear mechanisms.

This study intended to investigate the effect of tribological parameters on wear mechanisms and friction coefficient for homogeneous and heterogeneous materials. Particularly, effects of particle geometry and normal load on the tribological behaviour of an aluminium alloy and nodular cast iron have been developed. These materials are used in two industrial applications. The first one is used to transport granular material. It has been shown that damage of used truck’s buckets is produced. However, the nodular cast iron is used in automobile industry thanks to its lower density, good wear resistance and its low friction coefficient. A scratch test was used and the wear mechanisms were observed for different attack angles. The normal load was also varied and correlation between wear mechanisms, tribological parameters and friction coefficient was highlighted.

This paper addresses a study to achieve a method of assessment of coated abrasives for precision belt grinding based on the identification of the prevailing relationships between the changing features of fixed grains on flexible coated belts and grinding performance. A set of parameters was defined which describe the aluminium oxide resin-bonded belt characteristics including active grits density, cutting edge dullness, chip storage space and mean effective indentation. A parametric study was made of the effects of coated belt characteristics on surface finish performance with different grain sizes for grinding different workpiece materials. Experimental results are discussed in relation to the prevailing mechanisms of the process at the belt-work interface which can be separated into cutting and ploughing components. This enables also to describe the grit wear mechanisms operating with coated abrasives when grinding two engineering materials.

This paper investigates the relationship between wear and the conditions of heat removal at the tip of the tool. In this work we team numerical simulations to SEM imagery in order to map the thermal conductivity within the tool zone of action of a coated carbide (WC-CO) tool. The results indicate that depending on the temperature rise, the tool tip might undergo a severe drop in thermal conduction. This drop may locally restrict the ability of the tool material to dissipate the applied thermal load. This may nucleate thermally congested clusters within the tool tip where the material completely loses the ability to transport heat. The constriction of thermal transport renders an energetically active zone where the thermal energy available may be used to activate wear through different mechanisms. It is also found that the immediate layer under the surface of the tool tip is important to enhance the ability of the tool material to dissipate the thermal loads. The results highlight the importance of enhancing the efficiency of heat removal within the tool active zone in order to improve wear resistance.

This article investigates the machinability of two Al/SiC particulate metal-matrix composites (MMC) with 5 and 15% vol. SiC particles. Dry turning tests were performed with three different CVD diamond-coated tools. In a first series of experiments, various cutting conditions were tested and their effects on tool wear mechanisms were studied. For the second series, optimal cutting conditions were chosen and tool life was investigated. The consumed spindle power was continuously measured; it was shown that its increasing follows the evolution of the tool wear criteria. Residual stresses at the machined surfaces were measured by X-ray diffraction technique. The effect of SiC percentage in the MMC on the machinability was also investigated.

The contribution of gear tooth flank surface micro-finish on gear noise has not yet been taken into consideration. This paper is devoted to study the simultaneous effect of tooth roughness and lubricant viscosity on automotive gear vibrations. The vibrations performances were evaluated on an instrumented test rig under both dry and wet conditions. A non-destructive replication technique coupled to 3D optical measures was used to acquire the flanks topographies, which were characterized using multiscale decomposition. A three-dimensional finite element simulation of a helical gear was performed to assess the micro-scales impact on gear noise. Numerical representative surfaces morphologies were introduced into the simulation and compared through the transmission error calculation. Results have shown gear noise dependence on tooth finishing processes.