Surface integrity

Spécialité : « Génie industriel : conception et production » préparée au laboratoire G-SCOP (Sciences pour la Conception, l'Optimisation et la Production) dans le cadre de l'Ecole Doctorale « Ingénierie-Matériaux Mécanique Energétique Environnement Procédés Production » et au département RK5 « Mécanique appliquée » de l'Université Technique Bauman de Moscou présentée et soutenue publiquement par Dmitry BONDARENKO le 15 décembre 2010

These Super alloys sustain its strength at high temperature and pressure conditions. Such materials have great demand in aerospace industry, marine industry, and nuclear power plants. It is particularly used in the hot sections like engines, because of their high strength and corrosion resistance at high temperature and pressure but they are the most difficult to machine materials. Their high strength possesses large amount of heat generation while machining, which reduce life of tool. Strain rate sensitivity, work hardening and precipitation hardening of material leads to more tool wear. Surface integrity obtain while machining of superalloys is poor. Poor surface finish and high residual stresses are the main causes of failure of these material components. Cutting fluid apply at high pressure in chip forming zone. It affects environment and create problem of disposal of cutting fluid. So dry machining should be employed. This article is about the difficulties occurs during dry mac...

Burnishing is a plastic deformation process that reduces roughness while increasing hardness by introducing compressive residual stresses near the surface zone. These improvements will depend mainly on two fundamental variables: the applied load and the friction derived from the tool–surface interaction. Nevertheless, microstructural differences in the materials have not yet been considered within this interaction. This leads to a generalization of the process that can result in the failure of industrial components. Therefore, the aim of this work is to study the microstructural influence of the ball-burnishing process from a tribological perspective. Thus, martensitic and austenitic stainless steels were evaluated in terms of friction and surface integrity. The results show that parameterizing the process according to the tool–surface interaction is critical since improvements depend on friction as a function of the availability of plastic deformation of the crystallographic struct...

Dry Electric discharge machining EDM process is an environmentally safe approach for the machining over the conventional oil-based EDM machining. Bright mild steel is difficult to machine due to its cold forging manufacturing process. The experiments were carried on bright mild steel with a hollow copper electrode which is having thin wall thickness as per the design of experiment using Taguchi method. In this study, the process parameters for the dry EDM are evaluated and optimized with two methods, grey relational analysis (GRA) and grey fuzzy logic respectively. The optimization has been carried out for the multiple response variables, material removal rate (MRR), tool wear rate (TWR), and surface roughness (SR) against the process variables. The process variables considered for this study are current, pulse on time (POT) and oxygen gas pressure. Also, the variance analysis has been carried out statically for all the process parameters against the response variables. Grey relational analysis (GRA) and Grey fuzzy multiobjective optimization was used to optimize level of process parameters. This paper also compared optimization results of GRA and grey fuzzy optimization process. It was observed that 15 A current, 100 POT and 2 bar dielectric pressure showed optimized results for better MRR, TWR and SR during machining of workpiece. Current and POT were significant process parameters for MRR and TWR.

There is a requirement to find accurate parameters to accomplish precise dimensional accuracy, excellent surface integrity and maximum MRR. This work studies the influence of various cutting parameters on output parameters like Cutting force, Surface roughness, Flatness, and Material removal rate while face milling. A detailed finite element model was developed to simulate the face milling process. The material constitutive behavior is described by Johnson-Cook material model and the damage criteria is established by Johnson-Cook damage model. The result indicate significant effects of all three cutting parameters on MRR and both feed rate and depth of cut have significant effect on cutting force. Also, feed rate has significant effect on PEEQ and none of the parameters have effect on flatness.

Mechanical or thermal impacts on surfaces and near-surface layers during manufacturing processes often result in structural changes. They become detectable by photothermal techniques, when they correlate with alterations of thermal properties. We apply this approach on the detection of variations in ceramic surfaces. Vickers indentations model the mechanical load during grinding and a thermal surface treatment was performed by pulsed laser illumination. From the photothermal signals the depths and profiles of thermal conductivity variations depending on the different loading strengths could be reconstructed.

This paper investigates the influence of jet traverse speed on the surface integrity of 0.66 wt% Al2O3 nanoparticle reinforced metal matrix composite (MMC) generated by Abrasive Water Jet Machining(AWJM). Surface morphology, surface topography and surface roughness (SR) of the AWJ surface was analyzed. The machined surfaces of the nanocomposites were examined by laser confocal microscope and field emission scanning electron microscope (FESEM). Microhardness and elasticity modulus measurement by nanoindentation testing were also performed across thickness of the samples to see depth of the zone, affected by AWJ cutting. The result reveals that extent of grooving by abrasive particle and irregularity in AWJ machined surface increases as the traverse speed increased. Similarly, the rise in value of surface roughness parameters with traverse speed was also seen. In addition, nanoindentation testing represents the lower hardness and elastic modulus due to softening occurs in AWJ surface.

The machined surface integrity in the turning of hardened steels is adversely influenced by heat generation and friction which requires pacification of the temperature by the effective cooling-lubrication approach and cutting tool performance. The present research analyzes the surface integrity of hardened AISI 4140 steel during turning with recently developed scalable pulsed power plasma SPPP-AlTiSiN coated carbide tool under nanofluid-assisted minimum quantity lubrication (MQL). Zinc oxide nanoparticles and environmentally friendly radiator coolant are mixed to prepare the nano cutting fluid. This analysis addresses the various aspects of surface integrity concerning surface morphology, machined surface hardness, residual stress and white layer development, and machined surface finish under varying cutting parameters (depth of cut, speed, feed, nose radius). Response surface methodology (RSM) is suggested to predict and to optimize the surface roughness in hard turning. Thereafter...

Maraging steels are precipitation hardening steels used for highly loaded components in aeronautical and tooling industry. They are subjected to thermomechanical loads and wear, which significantly shorten their service life. Improvements of their surface mechanical properties to overcome such phenomena are of great interest. The purpose of our research was to investigate the influence of pulse density and spot size of a laser shock peening (LSP) process on the surface integrity with the fatigue resistance of X2NiCoMo18-9-5 maraging steel. Surface integrity was analyzed through roughness, residual stress, and microhardness measurements. The tests performed on resonant testing machine confirmed LSP is a promising process for increasing fatigue resistance of a component. Fatigue crack occurs, when the resonance frequency decreases. This moment, when the fatigue crack initiation phase ends and the fatigue crack propagation phase starts, was chosen as the moment of failure. We have prov...

This article outlines a technology for hole-finishing in short-length cylinder lines to improve wear resistance. The technology is based on an optimized diamond-burnishing (DB) process. The latter was implemented on conventional and CNC lathes, milling machines, and machining centers using a simple burnishing device with an elastic beam. The material used in this study was AISI 321 austenitic stainless steel. The governing factors used were the radius of the diamond insert, burnishing force and feed rate. The objective functions relating to surface integrity characteristics were selected on the basis of their functional importance relative to the wear resistance of the processed hole surface: height and shape roughness parameters, surface microhardness, and surface residual axial and hoop stresses. The one-factor-at-a-time method (used to reduce the factor space), a planned experiment, and regression analyses were used. The multi-objective optimization tasks, which were defined for ...

Abrasive Waterjet technology is a machining process using high speed water with the addition of mineral abrasive grains to remove the workpiece material. Due to the intrinsic properties of the process, the interface zone where the material removal occurs is hidden in the workpiece. One of the possibilities to observe propagation of the cutting front is to visualise it by means of a thermal camera or in the case of transparent materials by an optical camera also. The resulting images can be analysed by using the methods of digital image processing to extract the parameters of the cutting front, which can be used to control the process.

Ti-6Al-4V grade titanium alloy is the most popular alloy and is used for a wide range of applications in aerospace, marine, power generation and offshore industries etc., because of its very good mechanical properties such as high tensile strength, fatigue resistance, highest strength-to-weight ratio, extraordinary corrosion resistance and toughness even at elevated temperatures. Wire Electrical Discharge Machining (WEDM) is extensively used for machining of complex shapes in the field of die and mould making, medical, aerospace and automobile industries for machining of too hard materials. WEDM is essentially a thermal process with a complex metal removal mechanism, involving the formation of a plasma channel between the wire/tool and workpiece, resulting in the material removal, which also leads to surface roughness, work hardness, over cut, white layer, heat effected zone, surface structural changes, metallurgical transformations and cracking. These properties determine the operational behaviour of the material and can be included in one term called surface integrity. In this Investigation multi cutting pass i.e. rough/main cut and trim/finish cut approach was adopted to improve the quality of surface characteristics of WEDM surface of Titanium alloy. The results show that the WEDMed surface topography shows dominant micro voids, thick white layer and heat affected zone and even micro cracks at high pulse on time and pulse current and these are low at low pulse on time and pulse current during trim cuts. Further surface topography and micro structural changes were observed through scanning electron microscopy (SEM) micrographs.

This article presents aspects regarding an innovative nonconventional technology: abrasive water jet cutting. There are presented aspects regarding technique of abrasive water jet cutting (principle, parameters, and theoretical considerations about them), equipment (with emphasis on very high pressure pump) and performance of this technology (materials possible to be cut, cutting parameters for some materials). There are presented also results (theoretical aspects, specific techniques, cutting results) regarding other than cutting technological operations possible to be performed with abrasive water jet: drilling with abrasive water jet. Many of those presented in this article are results from research activity of the authors or from doctoral thesis.

Inconel 718 is a Ni superalloy widely used in high responsibility components requiring excellent mechanical properties at high temperature and elevated corrosion resistance. Inconel 718 is a difficult to cut material due to the elevated temperature generated during cutting, its low thermal conductivity, and the strong abrasive tool wear during cutting process. Finishing operations should ensure surface integrity of the component commonly requiring the use of hard metal tools with sharp tool edges and moderate cutting speeds. Polycrystalline cubic boron nitride (PCBN) tools recently developed an enhanced toughness suitable for these final operations. This paper focuses on the study of PCBN tools performance in finishing turning of Inconel 718. Several inserts representative of different manufacturers were tested and compared to a reference carbide tool. The evolution of tool wear, surface roughness, and cutting forces was analyzed and discussed. PCBN tools demonstrated their suitability for finishing operations, presenting reasonable removal rates and surface quality.

Inconel 718 is a Ni superalloy widely used in high responsibility components requiring excellent mechanical properties at high temperature and elevated corrosion resistance. Inconel 718 is a difficult to cut material due to the elevated temperature generated during cutting, its low thermal conductivity, and the strong abrasive tool wear during cutting process. Finishing operations should ensure surface integrity of the component commonly requiring the use of hard metal tools with sharp tool edges and moderate cutting speeds. Polycrystalline cubic boron nitride (PCBN) tools recently developed an enhanced toughness suitable for these final operations. This paper focuses on the study of PCBN tools performance in finishing turning of Inconel 718. Several inserts representative of different manufacturers were tested and compared to a reference carbide tool. The evolution of tool wear, surface roughness, and cutting forces was analyzed and discussed. PCBN tools demonstrated their suitabil...

This article outlines a technology for hole-finishing in short-length cylinder lines to improve wear resistance. The technology is based on an optimized diamond-burnishing (DB) process. The latter was implemented on conventional and CNC lathes, milling machines, and machining centers using a simple burnishing device with an elastic beam. The material used in this study was AISI 321 austenitic stainless steel. The governing factors used were the radius of the diamond insert, burnishing force and feed rate. The objective functions relating to surface integrity characteristics were selected on the basis of their functional importance relative to the wear resistance of the processed hole surface: height and shape roughness parameters, surface microhardness, and surface residual axial and hoop stresses. The one-factor-at-a-time method (used to reduce the factor space), a planned experiment, and regression analyses were used. The multi-objective optimization tasks, which were defined for ...

This review paper analyses and summarises the results found while studying the slide burnishing (SB) of metal components refracted through a prism during the surface engineering (SE) process, over the period of January 2019 to January 2023. According to the classification of SE processes defined in the article, SB as a technique in the scope of SE that belongs to the group of static surface cold working (SCW) processes, based on severe surface plastic deformation, and is realised under the condition of sliding friction contact with the treated surface. When the deforming element is natural or artificial diamond, SB is known as diamond burnishing (DB). SB is especially suited for axes, shafts, and holes with circular cross-sections but can also be implemented on flat-face and complex surfaces. SB is eco-friendly and a very economical method for producing mirror-like surface finishes on a wide range of ferrous and non-ferrous machined surfaces, but it can also be realised as a hardeni...

Surface integrity is a key property in the functional performance of machined parts and assembled engineering components. In this study, the effects of cutting conditions and tool wear on the surface integrity of Ti-6Al-4V titanium alloy after high-speed dry end milling were investigated. Different cutting speeds (100-300 m/min) and feeds (0.03 and 0.06 mm/tooth) as well as TiAlN + TiN physical vapor deposition (PVD)-coated carbide tool were employed during the machining trials. Surface roughness value and sub-surface microhardness of the machined surfaces were measured, and the corresponding alterations beneath the surface were characterized through electron microscopy. Results showed that surface roughness values at different cutting speeds directly depends on the tool conditions. The use of a new tool contributed to a higher surface quality of 185 nm compared to 320 nm for the used tool at the highest investigated cutting speed. It was found that operating the end milling with the new tool at a higher feed rate significantly decreased the surface roughness of the machined surface from 415 to 225 nm at a lower cutting speed. Feed marks and material redeposition defects were detected on the surface, while plastic deformation was observed in the sub-surface of the machined surface. Microhardness measurement revealed that no significant alterations occurred at the sub-surface when lower cutting speed and feed were employed. Higher cutting speed and feed rate enhanced the sub-surface alteration and resulted in considerable plastic deformation. Microscopic observations further highlighted this behavior.

Surface integrity of workpieces after machining processes is one of the most essential requirements of engineers in advanced industries, since it has significant effect on performance and service life of the components. Based on this, thermal and mechanical loads generated by machining are responsible for change in mechanical properties of the machined workpiece and consequently, they should be controlled. Among them, Ti-6Al-4V is utilized extensively by engineers because of its excellent properties. Therefore, at the present study, extensive experiments were conducted to characterize the performance of machining operation regarding the surface integrity of Ti-6Al-4V super alloy. Hence, the effect of experimental conditions on microhardness profile, surface roughness, grain size, and maximum machining temperature was studied. The results indicated that, cutting speed is a predominant parameter for enhancement of surface microhardness and increase in feed rate has the striking influence on thermal loads enhancement. The results also demonstrated that, increasing depth of cut has the lower influence on grain size variation.

In laser-assisted machining (LAM), the laser source is focused on the workpiece as a thermal source and locally increases the workpiece temperature and makes the material soft ahead of the cutting tool so using this method, the machining forces are reduced, which causes improving the surface quality and cutting tool life. Machinability of advanced hard materials is significantly low and conventional methods do not work effectively. Therefore, utilizing an advanced method is inevitable. The product life and performance of complex parts of the leading industry depends on surface integrity. In this work, the surface integrity features including microhardness, grain size and surface roughness (Ra) and also the maximum cutting temperature were investigated experimentally in LAM of Ti-6Al-4V. According to the results, cutting speed has inverse effect on the effectiveness of LAM process because with increasing speed (15 to 63 m/min), temperature decreases (524 °C to 359 °C) and surface rou...

Titanium alloys have numerous applications in the aerospace and medical industry due to their high strength and low weight. In the manufacturing of aerospace parts, surface integrity plays a key role due to its strong relationship with fatigue life and performance of the components. Since titanium alloys are difficult-to-machine, their Conventional Machining (CM) provides some technical limitations. As an alternative method, Laser-Assisted Machining (LAM) can be employed for this purpose and it is recommended for machining of hard materials. Laser Machining is the hybrid machining technique in which laser radiation is localized in front of cutting zone. However, surface integrity of the machined part should be controlled in LAM process due to the thermal effects of laser beam in to the workpiece material. Therefore, at the present study, experimental investigations were performed for both conventional and laser-assisted machining of Ti-6Al-4 V alloy and their results on surface integrity were compared and discussed together. In this regard, important indications of surface integrity including microhardness, grain size, surface roughness as well as thermal loads generated during the removal process were evaluated at different machining parameters. The results demonstrated that the use of laser-assisted machining under controlled process conditions can be significantly useful for improvement of surface integrity indications in machining of Ti-6Al-4 V superalloy.

High temperature generated and stresses induced as a result of turning of Ti6Al4V results in poor surface finish. The aim of this study was to investigate the effect of coolant temperature on the surface roughness of Ti6Al4V which is a core material used as an implant. A cooling system was developed to reduce the temperature of the coolant (soluble oil) from room temperature to 2oC. Ti6Al4V was turned in dry and cooled (at temperatures 5, 7, 9 and 11 oC) conditions. The experiment was designed using central composite design of (Response surface methodology) Design Expert 11.0 to generate an array and optimize the machining parameters. The machining parameters used were cutting speed, feed rate, depth of cut and coolant temperature. Results analyses show that cutting speed and depth of cut had considerable effect on surface roughness of Ti6Al4V. Surface roughness reduced when coolant temperature was reduced. The results of this study shows that turning Ti6Al4V at a very low cutting t...

In the present research work, performance of dielectric media (conventional EDM oil and distilled water) is studied in the context of machinability of Inconel 825 during electro-discharge machining. In this work, machinability is evaluated in purview of material removal efficiency, tool wear rate, and surface integrity of the machined specimen. Study of surface integrity includes morphological study as well as analysis of topographical measures like surface roughness, surface crack density, white layer thickness, foreign material migration, metallurgical characterization along with phase alteration and precipitation of intermetallic compounds and finally, micro-hardness tests. Experimental results suggest that as compared to EDM oil, distilled water (used as dielectric media) adversely affects the efficiency towards material removal, and promotes formation of rough surface. An important observation is that when EDM oil is used as dielectric media, carbide formation is attributed to the machined surface due to pyrolysis of hydro-carbon. While in case of distilled water, its decomposition causes oxide formation at the machined surface instead of carbides. Moreover, it is observed that peak discharge current imposes positive effect on both surface crack density, and white layer thickness. Microhardness depth profile confirms presence of hardened layer up to certain depth beneath the machined surface followed by gradual truncation, as distance is increased towards interior of the parent material.

In the present research work, performance of dielectric media (conventional EDM oil and distilled water) is studied in the context of machinability of Inconel 825 during electro-discharge machining. In this work, machinability is evaluated in purview of material removal efficiency, tool wear rate, and surface integrity of the machined specimen. Study of surface integrity includes morphological study as well as analysis of topographical measures like surface roughness, surface crack density, white layer thickness, foreign material migration, metallurgical characterization along with phase alteration and precipitation of intermetallic compounds and finally, micro-hardness tests. Experimental results suggest that as compared to EDM oil, distilled water (used as dielectric media) adversely affects the efficiency towards material removal, and promotes formation of rough surface. An important observation is that when EDM oil is used as dielectric media, carbide formation is attributed to the machined surface due to pyrolysis of hydro-carbon. While in case of distilled water, its decomposition causes oxide formation at the machined surface instead of carbides. Moreover, it is observed that peak discharge current imposes positive effect on both surface crack density, and white layer thickness. Microhardness depth profile confirms presence of hardened layer up to certain depth beneath the machined surface followed by gradual truncation, as distance is increased towards interior of the parent material.

Machining induced surface integrity is studied in the context of Electrical Discharge Machining (EDM) of Grade 5 Ti-alloy (Ti-6Al-4V). Experiments are conducted using copper electrode submerged in kerosene (as dielectric media). Different settings of peak discharge current, and pulse-on duration are utilized for conducting EDM experiments. Surface integrity of the EDMed specimen is assessed in purview of surface morphology, and topographical characteristics like surface roughness, surface crack density, white layer thickness, metallographic features, material migration, and micro-indentation hardness. Effects of peak current, and pulse-on duration are observed on influencing surface integrity of the end product. Additionally, data in regards of material removal efficiency, and tool wear rate are presented to support root causes behind surface and sub-surface damages.

Due to increased demand of dimensional accuracy and high precision of manufactured parts, wire electrical discharge machining (WEDM) became very popular, especially for 'difficult-to-cut' materials like titanium alloys. Grade 5 Ti alloy (Ti-6Al-4V) has enormous application in aerospace and biomedical fields. WEDM performance of Ti-6Al-4V is somewhat restricted due to its poor thermal conductivity, formation of hard and brittle carbide-/oxide-rich layer and often surface cracking which affect fatigue performance of the part product. Therefore, multi-cut strategy is adapted to mitigate machining-induced defects. The multi-cut mode consists of one main/rough cut followed by a number of trim/finish cuts. Aspects of surface integrity of the WEDMed Ti-6Al-4V obtained in different modes of cut are delineated in this reporting. Three slots are produced: (1) main cut; (2) main cut followed by one trim cut; and (3) main cut followed by two trim cuts using uncoated brass wire and zinc-coated brass wire, respectively. Surface morphology along with topographical features including roughness average, crack density, recast layer thickness, material immigration, residual stress and micro-indentation hardness is studied. Results obtained thereof are analysed with relevance to kerf width, material removal rate and wire wear.

Ball burnishing is a technique of surface enhancement that can provide residual compressive stresses on the surface to improve surface roughness, hardness and wear resistance of the material. The ball burnishing tool developed can be used on conventional lathe machine. It is observed that tool is giving satisfactory results to improve surface finish of AA6351. By using the designed tool Surface finish of 0.069 micrometer is achieved. Depth of penetration proved to be the predominant parameter among the parameters used.

In today's business environment, the trend towards more product variety and customization is unbroken. Due to this development, the need of agile and reconfigurable production systems emerged to cope with various products and product families. To design and optimize production systems as well as to choose the optimal product matches, product analysis methods are needed. Indeed, most of the known methods aim to analyze a product or one product family on the physical level. Different product families, however, may differ largely in terms of the number and nature of components. This fact impedes an efficient comparison and choice of appropriate product family combinations for the production system. A new methodology is proposed to analyze existing products in view of their functional and physical architecture. The aim is to cluster these products in new assembly oriented product families for the optimization of existing assembly lines and the creation of future reconfigurable assembly systems. Based on Datum Flow Chain, the physical structure of the products is analyzed. Functional subassemblies are identified, and a functional analysis is performed. Moreover, a hybrid functional and physical architecture graph (HyFPAG) is the output which depicts the similarity between product families by providing design support to both, production system planners and product designers. An illustrative example of a nail-clipper is used to explain the proposed methodology. An industrial case study on two product families of steering columns of thyssenkrupp Presta France is then carried out to give a first industrial evaluation of the proposed approach.

Additive manufacturing can rapidly fabricate the desired components by selectively melting and solidifying feedstock, rather than conventional subtractive machining. However, the difference between the two routes in terms of surface integrity of the final component is relevant. This paper presents a strategy to control the surface characteristics of additively manufactured stainless steel by roller burnishing. In particular, process parameters have been carefully selected to improve the surface integrity of the worked material. The quality of the surface has been analyzed in terms of roughness, hardness, microstructure and residual stresses. The overall product endurance under high cycle fatigue load has been evaluated.

In today's business environment, the trend towards more product variety and customization is unbroken. Due to this development, the need of agile and reconfigurable production systems emerged to cope with various products and product families. To design and optimize production systems as well as to choose the optimal product matches, product analysis methods are needed. Indeed, most of the known methods aim to analyze a product or one product family on the physical level. Different product families, however, may differ largely in terms of the number and nature of components. This fact impedes an efficient comparison and choice of appropriate product family combinations for the production system. A new methodology is proposed to analyze existing products in view of their functional and physical architecture. The aim is to cluster these products in new assembly oriented product families for the optimization of existing assembly lines and the creation of future reconfigurable assembly systems. Based on Datum Flow Chain, the physical structure of the products is analyzed. Functional subassemblies are identified, and a functional analysis is performed. Moreover, a hybrid functional and physical architecture graph (HyFPAG) is the output which depicts the similarity between product families by providing design support to both, production system planners and product designers. An illustrative example of a nail-clipper is used to explain the proposed methodology. An industrial case study on two product families of steering columns of thyssenkrupp Presta France is then carried out to give a first industrial evaluation of the proposed approach.

Additive manufacturing can rapidly fabricate the desired components by selectively melting and solidifying feedstock, rather than conventional subtractive machining. However, the difference between the two routes in terms of surface integrity of the final component is relevant. This paper presents a strategy to control the surface characteristics of additively manufactured stainless steel by roller burnishing. In particular, process parameters have been carefully selected to improve the surface integrity of the worked material. The quality of the surface has been analyzed in terms of roughness, hardness, microstructure and residual stresses. The overall product endurance under high cycle fatigue load has been evaluated.

In today's business environment, the trend towards more product variety and customization is unbroken. Due to this development, the need of agile and reconfigurable production systems emerged to cope with various products and product families. To design and optimize production systems as well as to choose the optimal product matches, product analysis methods are needed. Indeed, most of the known methods aim to analyze a product or one product family on the physical level. Different product families, however, may differ largely in terms of the number and nature of components. This fact impedes an efficient comparison and choice of appropriate product family combinations for the production system. A new methodology is proposed to analyze existing products in view of their functional and physical architecture. The aim is to cluster these products in new assembly oriented product families for the optimization of existing assembly lines and the creation of future reconfigurable assembly systems. Based on Datum Flow Chain, the physical structure of the products is analyzed. Functional subassemblies are identified, and a functional analysis is performed. Moreover, a hybrid functional and physical architecture graph (HyFPAG) is the output which depicts the similarity between product families by providing design support to both, production system planners and product designers. An illustrative example of a nail-clipper is used to explain the proposed methodology. An industrial case study on two product families of steering columns of thyssenkrupp Presta France is then carried out to give a first industrial evaluation of the proposed approach.

In today's business environment, the trend towards more product variety and customization is unbroken. Due to this development, the need of agile and reconfigurable production systems emerged to cope with various products and product families. To design and optimize production systems as well as to choose the optimal product matches, product analysis methods are needed. Indeed, most of the known methods aim to analyze a product or one product family on the physical level. Different product families, however, may differ largely in terms of the number and nature of components. This fact impedes an efficient comparison and choice of appropriate product family combinations for the production system. A new methodology is proposed to analyze existing products in view of their functional and physical architecture. The aim is to cluster these products in new assembly oriented product families for the optimization of existing assembly lines and the creation of future reconfigurable assembly systems. Based on Datum Flow Chain, the physical structure of the products is analyzed. Functional subassemblies are identified, and a functional analysis is performed. Moreover, a hybrid functional and physical architecture graph (HyFPAG) is the output which depicts the similarity between product families by providing design support to both, production system planners and product designers. An illustrative example of a nail-clipper is used to explain the proposed methodology. An industrial case study on two product families of steering columns of thyssenkrupp Presta France is then carried out to give a first industrial evaluation of the proposed approach.

Burnishing is a Severe Plastic Deformation process having the potential to replace expensive finishing post processes. It is considered a super finishing process due to its results in terms of drastic roughness reduction. Also, additional advantages include the surface integrity improvement functionalized to the specific application. Even though burnishing is widely applied for surface improvement of conventional materials, knowledge about its effect on additively manufactured metals is still limited. This paper aims to fill this gap presenting experiments on roller burnishing on additively manufactured stainless steel in order to improve its tribological performance. The experimental campaign was carried out to find suitable process parameters able to drastically improve the tribological behavior of the final product. In particular, the influence of the burnishing forces on the whole surface quality has been addressed. The overall results demonstrate that the selected burnishing co...

Burnishing is considered a super finishing process able to drastically increase surface quality in terms of hardness and roughness of the manufactured parts. Consequently, it is considered appealing for the performance enhancement of products where the surface quality plays a crucial role. However, when burnishing grade 5 titanium alloy, a quantitative relationship between process parameters and surface integrity is still missing. This work provides a deep analysis of the burnishing parameters and their influence on the surface integrity of Ti-6Al-4V. In particular, starting from a large experimental campaign, statistical analysis of the results is performed and models able to describe the surface integrity response based on different burnishing parameters are presented. The overall results allow us to clearly define the relationship within the input and output variables identifying, by the proposed models, different operational windows for surface integrity improvement.

In today's business environment, the trend towards more product variety and customization is unbroken. Due to this development, the need of agile and reconfigurable production systems emerged to cope with various products and product families. To design and optimize production systems as well as to choose the optimal product matches, product analysis methods are needed. Indeed, most of the known methods aim to analyze a product or one product family on the physical level. Different product families, however, may differ largely in terms of the number and nature of components. This fact impedes an efficient comparison and choice of appropriate product family combinations for the production system. A new methodology is proposed to analyze existing products in view of their functional and physical architecture. The aim is to cluster these products in new assembly oriented product families for the optimization of existing assembly lines and the creation of future reconfigurable assembly systems. Based on Datum Flow Chain, the physical structure of the products is analyzed. Functional subassemblies are identified, and a functional analysis is performed. Moreover, a hybrid functional and physical architecture graph (HyFPAG) is the output which depicts the similarity between product families by providing design support to both, production system planners and product designers. An illustrative example of a nail-clipper is used to explain the proposed methodology. An industrial case study on two product families of steering columns of thyssenkrupp Presta France is then carried out to give a first industrial evaluation of the proposed approach.

The paper presents a deep experimental study on surface modifications induced by roller burnishing process of Ti6Al4V titanium alloy. The experimental campaign has been performed based on a design of experiments at varying lubrication/cooling strategies, roller geometry, coating, and burnishing speed. The overall surface integrity has been analyzed in terms of surface roughness, micro hardness, topography, microstructural changes, and tribological performance. The results allowed to better define the relationships within burnishing process parameters and the surface quality of the final component. In particular, the obtained evidences show that cryogenic cooling conditions and coating tools significantly improve the hardness of the final component while the MQL lubrication leads to superior surface roughness. Overall, the process always improves the wear resistance of the components with optimal results when cryogenic cooling and coated tools are employed. Thus, the outcomes of the extensive experimental campaign allow to define a combination of process parameters leading to improved Ti6Al4V surface quality.

In today's business environment, the trend towards more product variety and customization is unbroken. Due to this development, the need of agile and reconfigurable production systems emerged to cope with various products and product families. To design and optimize production systems as well as to choose the optimal product matches, product analysis methods are needed. Indeed, most of the known methods aim to analyze a product or one product family on the physical level. Different product families, however, may differ largely in terms of the number and nature of components. This fact impedes an efficient comparison and choice of appropriate product family combinations for the production system. A new methodology is proposed to analyze existing products in view of their functional and physical architecture. The aim is to cluster these products in new assembly oriented product families for the optimization of existing assembly lines and the creation of future reconfigurable assembly systems. Based on Datum Flow Chain, the physical structure of the products is analyzed. Functional subassemblies are identified, and a functional analysis is performed. Moreover, a hybrid functional and physical architecture graph (HyFPAG) is the output which depicts the similarity between product families by providing design support to both, production system planners and product designers. An illustrative example of a nail-clipper is used to explain the proposed methodology. An industrial case study on two product families of steering columns of thyssenkrupp Presta France is then carried out to give a first industrial evaluation of the proposed approach.

During machining, surface modifications are directly related to the process dynamic affecting the thermomechanical properties of the materials. The physics phenomena (such as dynamic recrystallization, hardening and recovery effects) are difficult to be experimentally evaluated during the cutting operations, therefore the simulations are very important tools to understand their evolution. Orthogonal cutting experiments were conducted on Waspaloy under different cutting parameters and lubri-cooling conditions. The machined surfaces were evaluated via optical microscope and the surface integrity was analysed in terms of microstructural changes and microhardness. The deformation mechanisms that occurred in chip formation and on the machined surface were investigated in order to build-up a physically based constitutive model. Subsequently, the developed material model was implemented via sub-routine in a commercial Finite Element software. The numerical prediction strategy was validated through comparisons with experimental outcomes (cutting forces, temperature and metallurgical changes) and employed to predict the variables of scientific interest (microstructural modifications and microhardness). The overall absolute error in predicting the principal cutting force, feed force and temperature were approximately equal to 5%, 9% and 7% respectively. Furthermore, the developed model permits to explore the metallurgical changes and their evolution during the machining process varying cutting parameters and lubri-cooling conditions.

Surface quality is one of the most impellent customer requirements in machining. The main aspect of surface quality on machined parts is probably surface integrity, such as roughness and residual stresses. In particular, residual stresses in the machined surface and subsurface are affected by tool geometry, material and machining parameters. These residual stresses can have significant effects on the service quality and the component life; they can be determined by either empirical or numerical investigations for the selected configurations; however, they are expensive procedures. The problem becomes more difficult if the aim is the inverse determination of the cutting conditions which correspond to a requested residual stress profile, inside the machined material. This paper presents a predictive hybrid model based on the artificial neural networks (ANNs) and finite element method (FEM) that can be used for both forward and inverse prediction. The former is able to determine a residual stresses profile corresponding to a given tool, material and process conditions, the latter is able to determine these conditions when a constraint on the residual stresses distribution is given. Three layer neural networks were trained basing on selected data from numerical investigations on hard machining of 52100 bearing steel, and then validated with data obtained by experiments. Prediction errors range between 4% and 16% for the whole data set, both for forward analysis and inverse process design, showing that this hybrid ANN-FEM based approach provides a robust framework for 52100 machining analysis.

Functional performance of a machined product is strongly influenced by its surface characteristics that are frequently modified from the process. These changes must be taken into account when modeling the machining process. This work presents the modeling of grain size and hardness changes induced during turning of AA 7075-T651 alloy using the Finite Element (FE) method. The implemented user subroutine is able to describe the microstructural changes and the dynamic recrystallization in order to correctly simulate the formation of new grains and their influence on the material flow stress. The model is experimentally calibrated and validated to predict the evolution of the surface conditions (grain size, hardness, etc.) when varying the cutting speeds and tool nose radii. All simulations were performed for dry and cryogenic cutting conditions using uncoated carbide tools.

Inducing thermo-mechanical loads during the machining of hard materials lead to the severe grain refinement and hardness variation into the machined surface. This variation significantly affects the performance and the service quality of the products. Inconel 718 superalloy is one of the difficult-to-machine materials employed widely in aerospace industries and its surface characteristics after final machining process is really important. The main objective of this study is to implement a reliable finite element (FE) model for orthogonal machining of Inconel 718 alloy and prediction of the microstructure changes during the process. At first, experimental results of cutting forces, chip geometry and maximum temperature were taken into account to identify the most suitable material model out of the seven models found in the literature. Then, the FE numerical model was properly calibrated using an iterative procedure based on the comparison between simulated and experimental results. Moreover, a user subroutine was implemented in FE code to simulate the dynamic recrystallization and, consequently, to predict grain refinement and hardness variation during the orthogonal cutting of Inconel 718 alloy. Zener-Hollomon and Hall-Petch equations were employed to respectively predict the grain size and microhardness. In addition, the depth of the affected layer was controlled using the critical strain equation. As overall, a very good agreement has been found between the experimental and simulated results in term of grain size, microhardness and depth of the affected layer.

Machining Inconel 718 alloy is a challenge due to its low machinability. This thermal resistant alloy combines high strength even at high temperatures with strain hardening tendency that causes high forces and extreme cutting temperatures during the machining. These issues force industries to achieve suitable machining processes to deal with this kind of alloys and the high worldwide competitiveness. Nevertheless, environmental considerations must to be taken into account due to growing environmental concerns. In the work here presented, cryogenic cooling with external MQL lubrication (CryoMQL) working along with CO2 as internal coolant is proposed for milling Inconel 718 with the aim of not only improving from a technical point of view but also environmental. This technique was compared with other lubricooling techniques. The results show that internal CryoMQL improves tool life by 57% in comparison with emulsion coolant, achieving 120% if it is compared with MQL in stand-alone mode.

Descaling is a recent application of abrasive water jet machining. Several parameters can affect the steel surface and influence the descaling effect of abrasive water jet machining. The influence of the jet parameters has been experimentally studied, and the width of the surface morphology and roughness measured. The results show that the descaling width increases as the jet distance increases from 10 mm to 90 mm; the material removal at the cross section tends to be uniform. As the abrasive particle size is increased from 75 lm to 150 lm, the descaling width decreases whereas the material removal uniformity increases. Increasing the jet pressure from 30 MPa to 70 MPa increases the descaling width and material removal; the surface roughness improves to some extent, but the descaling uniformity decreases. As the jet angle is increased from 30°to 90°, the uniformity of the material removal decreases despite the increase in the descaling width. JOM

Inconel 718 (IN718) is a precipitation hardened nickel-base super-alloy exhibiting poor machinability and used in the hot section of aircraft engines. These components are subjected to severe thermo-mechanical loads in a highly corrosive environment, limiting their service life due to cracks and wear. Due to their high added-value, repair of damaged IN718 components is an interesting alternative instead their replacement. Repair process involves material removal of the damaged zone and subsequent cavity refill. Nevertheless, material removal of IN718 by conventional methods is a challenging task. Abrasive Water Jet (AWJ), a non-conventional machining process, offers a potential alternative to mitigate IN718 machining problems. However, research on the impact of AWJ process parameters during IN718 milling on the surface and material integrity is limited in the literature. Furthermore, in repair context, no study proposes AWJ machining as material removal process. The present work foc...

This paper investigates the effect of different cutting parameters (cutting speed, feed rate, and depth of cut) on surface integrity defined in terms of surface roughness and microhardness in dry hard turning process. The workpiece material used was hardened alloy steel AISI 52100 and it was machined on a CNC lathe with coated carbide tool under different settings of cutting parameters. Three cutting parameters each at three levels were considered in the study. Central composite design (CCD) of experiment was used to collect experimental data for surface roughness and microhardness. Statistical analysis of variance (ANOVA) was performed to determine significance of the cutting parameters. The results were analysed using an effective procedure of response surface methodology (RSM) to determine optimal values of cutting parameters. Several diagnostic tests were also performed to check the validity of assumptions. The results indicated that feed rate is the dominant factor affecting the surface roughness whereas the cutting speed is found to be the dominant factor affecting the microhardness. Results also revealed that within the range investigated, good surface integrity is achieved when feed rate and depth of cut are near their low levels and cutting speed is at high level. Finally, the optimal cutting parameters and model equations to predict the surface roughness and microhardness are proposed.