Abrasive Jet Machining

Purpose: The purpose of this paper is to study and analyse the possible impact of International Financial Reporting Standards on the level of earnings management. The paper includes a review of all such studies from around the world. Design/Methodology: Existing studies available on the topic are systematically reviewed. Different journals, periodicals and websites were used to gather the information. Time period considered for the study is from 2005 to 2019. Although most of the papers relate to foreign countries as not much research is available in the Indian context. Overall, 60 papers were considered, but out of them only 40 were found to be suitable for the present study. The review has been segregated into 3 parts. 30% of the paper focus on the meaning and determinants of earnings management, 20% of the studies relate to IFRS adoption around the world. Remaining research tries to analyse the connection between adoption of international standards and level of earnings management. Findings: The adoption of IFRS standards has no significant impact on the level of earnings management of any country. In fact, the level has increased in some countries after the compulsory adoption. However, if certain other factors are taken into account along with IFRS like audit quality, corporate governance practices, board management, R&D disclosure, enforcement mechanism, investor protection regime etc., the combined effect have yielded different results for different countries. Research Limitations and Implications: The study focuses only on one major area related to IFRS i.e., its impact on earnings management of a firm. Although there are many other determinants of earnings management and also IFRS had its impact on various other areas. But due to certain research limitations those are not considered Purpose: The purpose of this paper is to study and analyse the possible impact of International Financial Reporting Standards on the level of earnings management. The paper includes a review of all such studies from around the world. Design/Methodology: Existing studies available on the topic are systematically reviewed. Different journals, periodicals and websites were used to gather the information. Time period considered for the study is from 2005 to 2019. Although most of the papers relate to foreign countries as not much research is available in the Indian context. Overall, 60 papers were considered, but out of them only 40 were found to be suitable for the present study. The review has been segregated into 3 parts. 30% of the paper focus on the meaning and determinants of earnings management, 20% of the studies relate to IFRS adoption around the world. Remaining research tries to analyse the connection between adoption of international standards and level of earnings management. Findings: The adoption of IFRS standards has no significant impact on the level of earnings management of any country. In fact, the level has increased in some countries after the compulsory adoption. However, if certain other factors are taken into account along with IFRS like audit quality, corporate governance practices, board management, R&D disclosure, enforcement mechanism, investor protection regime etc., the combined effect have yielded different results for different countries. Research Limitations and Implications: The study focuses only on one major area related to IFRS i.e., its impact on earnings management of a firm. Although there are many other determinants of earnings management and also IFRS had its impact on various other areas. But due to certain research limitations those are not considered

Abrasive jet machining (AJM) is a manufacturing technology based on erosion localization and intensification. AJM has a progressively important influence on the machining technology market. Over the past 20 years, there has been an exponential growth in the number of papers that discuss AJM. Various innovations and process developments such as intermittent, submerged, thermally assisted and other jet conditions were proposed. This paper examines AJM’s technological advantages and the variety of machining operations in different industries where AJM is utilized. Particular attention is devoted to the micro-texturing capabilities of powder blasting and its application in tribology. New evidence of ductile and brittle material removal mechanisms are reviewed together with recently discovered elastic removal mode. The effects of hydraulic, abrasive and machining parameters on particles kinetic energy, machined surface roughness and footprint size are described in detail. Nozzle wear has a strong dependence on nozzle materials, its geometry, particles size, hardness, and flow rate. The trend of AJM development is a shift from macro to micro scale. Improvements in micro-machining resolution, process controlling and erosion prediction are current challenges facing AJM.

Abrasive waterjet machining (AWJM) is a new machining process, the advantages of which include low cutting temperatures, no heat damage to the material being cut, minimal dust, and low cutting forces. This paper presents a state of the art review of research in this new process. The main topics discussed are mechanics of material removal, productivity, cutting forces, surface quality and nozzle wear.

Conventional machining of polymeric composite materials is often both technically and economically less effective because the structural characteristics inherent in fibre reinforcement promote excessive tool wear. In recent years, abrasive waterjet machining (AWJM) has been proving to be successful in the machining of such materials. This paper presents a state of the art review of research in AWJM of polymeric composite materials. Among the main topics discussed are mechanisms of material removal, productivity and surface quality

This paper reports the identification of abrasive water jet process parameters for the cutting of AA5083-H32 aluminium alloy using the fuzzy TOPSIS method. Such identification requires a precise work in abrasive water jet (AWJ) cutting, considering that it determines the quality and performance of the process. In the present work, optimisation studies were carried out through using the fuzzy TOPSIS method for the determination of better optimal process parameters. The Taguchi full factorial method was used for the experimental design and the weighting of each output response was determined by a triangular fuzzy number method. The selection of optimal input parameters such as water jet pressure of 150 MPa, abrasive mesh size of #80 and jet impingement angle of 80º have been suggested for the precise work conducted in AWJ. A scanning electron microscope (SEM) was used for examining the AWJ cut surfaces at the optimal level of process parameter settings. An energy dispersive X-ray spectroscopy was employed to confirm the number of silicon particles embedded in the cut surfaces. The experimental result indicates the improvement in the quality of AWJ cutting by the fuzzy TOPSIS method through the identification of better optimal input process parameters.

A R T I C L E I N F O Keywords: abrasive jet machining micro-machining surface texturing solid particle erosion artificial joints A B S T R A C T Hectares of tribological micro-texture must be machined per year to reduce friction and wear in artificial ar-ticular joints. Productive and cost-effective tribo-texturing of freeform surfaces consisting of hard-to-machine materials is a current manufacturing challenge. This study evaluates the accuracy and productivity of micro abrasive jet machining when fabricating micro-channels on metal in a mask-less way. The influence of micro abrasive jet process parameters on micro-channel's geometry and fabrication speed is in focus in this study. We blast 27-μm alumina powder through Ø0.5 mm nozzle at Co-Cr-Mo substrate under 0.1-0.8 MPa of air pressure, 30°-90°of nozzle angles and 0.5-3.5 mm of stand-off distance. Measurements show that the micro-channels can be as narrow as 110% of the nozzle diameter and have V-, U-or W-shaped bottom at the particular stand-off distance and air pressure. The fabrication speed of 550 μm × 5 μm channels (width × depth) reaches 260 mm/ min and allows to texture the femoral head of a hip joint within several minutes using a single nozzle and a few grams of abrasives. Overall, the accuracy, productivity and cost-effectiveness of micro abrasive jet machining are highly suitable for tribological surface texturing of artificial joints.

Despite the large number of abrasive waterjet machining (AWJM) models developed so far, there still has been confusion about the nature by which workpiece surfaces are eroded. The finite element method (FEM) could provide both qualitative and quantitative means in order to explain the AWJ erosion process. This paper presents an attempt to model the AWJM process using the powerful tool of the finite element method. The main objective is to develop an FE model which would enable to predict the depth of cut without any cutting experiments. The new model takes into account the precise representation of the constitutive behaviour of the workpiece material under AWJ dynamic loading conditions. Interaction of the abrasive particle with the workpiece material is traced at small time increments. The model accurately predicts the depth of cut as a result of AWJ impact and the results are in good agreement with experimental results.

Understanding the exact nature of erosion of workpiece materials by abrasive waterjet machining (AWJM) is still confused, although it is important for successful modeling of this promising process. This paper presents a first attempt to model the AWJM process using the powerful tool of the finite element method (FEM) in order to explain the abrasive particle-workpiece interaction. Also the model predicts the behaviour of the process. The main objective is to develop an FE model which would enable to predict the depth of cut without any cutting experiments. The new model takes into account the precise representation of the constitutive behaviour of the workpiece material under AWJ dynamic loading conditions which was ignored in previous AWJM models in which the flow stress was represented by a constant value. Additionally, deformations, stresses and strains occurring in the workpiece material in the vicinity of the cutting interface as a result of the erosion impact by AWJ, could be obtained. In the present model, forces acting on the abrasive particle need not be initially determined, as in previous AWJM studies, as they are automatically calculated at each time step. The results show that the finite element method is a useful tool in predicting abrasive-material interaction and AWJ depth of cut.

Particle shape factor Surface roughness Developed interfacial area ratio Size effect A B S T R A C T Specific surface treatments to enhance adhesion, osseointegration and other area-related processes contribute greatly to the cost of manufacturing functional products. It is thus necessary to develop a productive and cost-efficient surface treatment technique for modifying the surface of bio-medical alloys such as Co-Cr-Mo to improve their bio-functionality. This study estimates the capabilities of the micro-blasting technique for a developed bone/implant interfacial area. Eight abrasive fractions of white aluminium oxide were comprehensively measured and blasted at a Co-Cr-Mo substrate. Then, this substrate was analysed in terms of nine roughness parameters. We found no significant variation in convexity, circularity or aspect ratio among 5-300 µm particles. The amplitude and space parameters of the eroded surface were proportional to the particles' kinetic energy, and two hybrid parameters were subject to the particle size effect. The working hypothesis is that the particle size effect on the wear rate and root mean square (RMS) gradient of the surface slope are two aspects of one phenomenon. The size effect is known in a wear issue, yet this is the first time the size effect has been reported in relation to surface morphology. Variation in the RMS gradient with variation in particle size was analytically explained by the relative bluntness theory. The developed interfacial area was proportional to the impact energy and inverse to the tip radius of the particle. Blasting of angular abrasives larger than 60 µm was capable of doubling the surface area, while blasting of abrasives larger than 300 µm produced appropriate topography for mechanical fixation at the bone/implant interface.

Erosion of ductile materials by abrasive waterjet machining (AWJM) is still a complex phenomenon. This paper presents a first attempt to simulate the abrasive waterjet machining (AWJM) process using the finite element method (FEM) in order to determine the workpiece response in this erosive wear process. Additionally, deformations occurring in the workpiece material in the vicinity of the cutting interface as a result of the high speed AWJ impact could be obtained. The results indicate that the finite element method is a useful tool in the prediction of the AWJ deformations.

Modeling of abrasive waterjet machining (AWJM) has been finding widespread interest for the past twenty years. Due to the complex interaction of several AWJM parameters, combined with the nonlinear dynamic high speed impact of several thousands of small abrasive particles on the workpiece surface, the mechanism of material removal has not yet been fully understood. The current paper presents an attempt to explain the mechanism of material removal in AWJ, as a result of abrasive particle impact through step by step tracing of the abrasive particle as it is interacting with the workpiece material. The new model considers the elastic-plastic behavior of the workpiece material. Also the non linear dynamic loading conditions which are characteristic feautres of AWJM are accounted for in the pesent study. The failure of the workpiece material is examined analytically, by means of a virtual finite element (FE) AWJ experiment, and experimentally, by means of scanning electron microscopy (SEM) and surface topographies. Stress results indicate that the workpiece material is subject to severe highly localized plastic deformation and as a result, small overlapping craters are generated. These craters are formed by high compressive stresses at the cutting interface. The finite element results indicate a good agreement with experimental results.

Although several theoretical and experimental models have been developed for abrasive waterjet machining #AWJM), the exact nature of
erosion is not yet understood. This paper presents an attempt to model AWJM using the ®nite element method #FEM) in order to explain the
abrasive particle±workpiece interaction process. Also, the model predicts the depth of deformation as a result of abrasive particle impact.
The main objective is to develop an FE model which would enable the prediction of the depth of cut without any cutting experiments. The
new model takes into account the precise representation of the constitutive behavior of the workpiece material under AWJ dynamic loading
conditions which was ignored in the previous AWJM models. In the present model, forces acting on the abrasive particle need not be
initially determined, as in previous AWJM studies, as they are automatically calculated at each time step. The results show that plastic
deformation is very localized. Finally, the present FE results are consistent with experimental results.

Micro-abrasive jet machining (AJM) is an advanced subtractive machining technology with ample opportunities to form regular micro-patterns on freeform surfaces. AJM removes material mainly through erosion and abrasion, which transform kinetic energy to fracture and deform substrates. The kinetic energy of a solid particle is tightly connected to its velocity, which is the most significant source of error in precise prediction of a machined feature. The present study involves both theoretical analysis and two-dimensional axisymmetric numerical simulation of particle velocity fields at the lower end of the micro-scale. The developed model represents the finest particles in a cylindrical nozzle down to an inner diameter of 100 μm. The computed results agree well with the experimental data. It is shown that, due to viscous friction, such nozzles are significantly less efficient in terms of particle saturation with kinetic energy. The study highlights the effects of nozzle diameter and length, air pressure, particle size and density on particle velocity development through the jet field. Finally, practical recommendations and multiple regression models of maximum particle velocity, location from the nozzle exit and simplex velocity profile approximation are offered for management of particle kinetic energy.

The abrasive waterjet machining (AWJM) process is so complex, due to the interaction of several working parameters, that its micro erosion mechanisms have not yet been completely understood. Understanding the interaction of a single abrasive particle with the workpiece material constitutes the basic step in understanding the occuring complex erosion phenomena. This paper presents the results of an extensive program of AWJ experimentation, which was recently carried out at the department of Machine Technology.

Abrasive jet machining is a metal removal process involving erosion of work surface on account of impingement of stream of high speed abrasive particles through a nozzle by high pressure air or gas. The small bits of work surface material get loosened due to repeated impacts and get loosened thereby being carried away by jet of abrasive particles. This paper reviews various parameters of abrasive jet machining and their respective effect on different materials

Abrasive machining and finishing processes are techniques of material removal that are introduced in order to cut workpiece materials
with the nominal mechanical and thermal residual stresses. These processes utilize continuous material removal by abrasive medium that
can be in forms of water, abrasive particles or a mixture of these two. The benefit of eliminating excessive mechanical cutting force results in
enhanced cutting of brittle or soft materials. On the other hand, removal of thermal cutting source provides a capability of cutting plastics and
diminished the chances of thermal cracking in workpiece. Abrasive finishing processes have been introduced as complementary to abrasive
cutting techniques in order to increase the precision and surface quality of manufactured parts. The most common of these techniques are water
jet machining (WJM), abrasive jet machining (AJM), abrasive water jet machining (AWJM) and magnetic abrasive machining processes such as
magnetic abrasive finishing (MAF), magneto-rheological abrasive finishing (MRF) and magneto-rheological abrasive flow finishing (MRAFF).

Abrasive water jet turning (AWJT) is an advanced machining technique surpassing the traditional turning by not inducing severe thermal or mechanical stresses in the machining zone. Nevertheless, controlling the performance of this process is very challenging as being dominated by several process parameters in addition to the complex physical nature of material removal. The present work aims to create a finite element (FE) model in order to examine the effect of traverse rate and jet impact angle on the erosion process in the radial mode of AWJT. The chosen workpiece material was AISI 4340 and the material model of Johnson-Cook (JC) was adopted for it to realize its behavior. The 3 2 full factorial design was employed to prepare the test plan under three levels of the two process factors. After performing the simulations, the crater geometry was observed for each factor combination in the test plan. The model results were consistent to some extent with the experimental studies and can be further used to predict the radial depth of cut (DOC) in AWJT.

Understanding the mechanism for brittle material removal via solid particle impact is important for various areas such as energy and aerospace industries. The existing analytical formulation of erosion damage, consistent with indentation fracture theory, overestimates actual erosion by over 200%. This study complements an existing analysis by prescribing a realistic shape and mechanical properties to the impinging particle. We quantitatively show that a lateral crack in glass does not nucleate at the indenter's tip or the theoretical plastic depth, but at an intermediate depth. This depth can be found by implementing the actual particle penetration depth into Hill's ratio. Several new geometries of the particle's impacting tip are proposed as ways to achieve adequate particle penetration depth instead of an expanding hemispherical cavity. The crater depth, surface roughness, and erosion efficiency of borosilicate glass are predicted with 10%, 24%, and 23% error, respectively, using a simple analytical routine.

The abrasive waterjet machining (AWJM) process is so complex, due to the interaction of several working parameters, that its micro erosion mechanisms have not yet been completely understood. Understanding the interaction of a single abrasive particle with the workpiece material constitutes the basic step in understanding the occuring complex erosion phenomena. This paper presents the results of an extensive program of AWJ experimentation, which was recently carried out at the department of Machine Technology.

Erosion of ductile materials by waterjet machining is still a complex phenomenon. This paper presents a finite element model of the waterjet machining (WJM) process. Cutting forces, deformations and stresses occurring in the workpiece material in the vicinity of the cutting interface as a result of erosion impact by the waterjet could be obtained. The results indicate that the finite element method is a useful tool in the analysis of  this process. Further research work is currently being conducted by the authors.

The improved scratch resistance of epoxy-based coatings on titanium alloy is greatly needed in the current biomedical device sector. Due to commercial factors, this improvement must be either non-consumptive or inherited from the antecedent machining steps. This study contributes an extensive understanding of Ti-6Al-4 V surface topography, microstructure, chemistry and wettability generated with various processes, such as milling, polishing, hydrofluoric acid-etching and micro-blasting with different process parameters by utilizing optical and electron microscopy, energy-dispersive X-ray spectroscopy, X-Ray diffraction and surface tension. The phenolic resin is then spin-coated, cured and scratched with a conical indenter in a constant loading mode. The influence of roughness parameters, microstructural and chemical changes on wettability and delamination size, pattern and mode are analyzed. The root mean square gradient of surface slope and the developed interfacial area ratio are found to be in good correlation with the delamination factor. The delamination factor and specific traction force after micro-blasting are improved by a factor of two compared to that achieved by polishing or milling and is superior to that obtained by acid-etching. This study, therefore, clearly demonstrates the strong potential of micro-blasting as a pretreatment technique to enhance the adhesion strength and scratch-resistance of epoxy coating on titanium implants.

This study proposes a novel, cost-efficient and productive technique, Tribo-blast, to tailor surface topography for tribological purposes. Tribo-blast is based on mask-less micro-blasting with spherical or angular particles and precisely controlled process parameters. This approach enables rapid fabrication of μ-pockets (5-50 μm) on free-form surfaces comprised of any material. A particle with a new 3D geometry-a spinning top-is proposed to match the shape and dimensions of the irregular craters formed in a metallic target by an angular particle at the normal impact angle. The results were experimentally validated on stainless steel 316L, Co-Cr-Mo and Ti-6Al-4V alloys. A simple analytical routine allowed for control over the size, area, concentration and homo-geneity of randomly distributed angular and spherical μ-pockets with <20% error. The Abbott-Firestone curve and texture ratio can be tailored according to one's intended design. The bearing index of the tailored surface was more than two times that of the lapped surface, and fluid retention was increased one hundred times. Thus, this approach is considered to be more productive, cost-effective and simple than current micro-texturing techniques.

Micro-blasting is a non-conventional subtractive micro-manufacturing technology based on erosion localisation and intensification. The thermal aspects of erosion are rarely discussed in the literature and commonly neglected in the analysis of erosion mechanism and quality control of machined surface. This study uses analytical, numerical and experimental approaches to explore erosion temperature in relation to micro-blasting of carbon steels. The research shows that, in terms of temperature, airborne erosion by solid particles is a double-natured process; the surface temperature may increase up to a few thousand degrees Celsius after a single impact, yet it dissipates at the subsurface over several microseconds. Melted and adhered drops of the metallic substrate were found in optical images of abrasive particles and SEM images of a machined surface. EDX elemental analysis confirmed that a thin metal layer was deposited on the particle's interface. Despite this, several FEM models and measurements taken by a thermocouple and IR camera-showed that the steady-state temperature is negligible. The heat generated during each impact has sufficient time to dissipate, leaving a residual temperature of a few degrees before the next impact at the same site. This heat accumulation could elevate the temperature to a few hundred degrees, particularly when the workpiece is small, although convective cooling by air flow effectively dominates this effect. In general, small and slow abrasives are recommended to reduce the temperature. Application of alumina particles smaller than 27 µm to blast low-carbon steels produces minimal negative consequences.