https://popups.uliege.be/esaform21/index.php?id=82 Coordinators: Prof. Domenico Umbrello, Prof. Takashi Matsumura Co-organisers: Prof. Pedro J. Arrazola, Dr. Guenael Germain, Dr. Cédric Courbon Description: The main topics of the minisymposium on Machining and Cutting are: Experimental and numerical analysis of machining operations; Material characterization and formulation of effective constitutive laws when severe plastic deformation are induced; Analysis of the tool wear, friction and material fracture in machining and cutting; Application of traditional and advanced coolant methodologies (near to dry, MQL, cryogenic, etc.) for enhancing the machinability and the product’s performance; Surface integrity (prediction of residual stresses, roughness, microstructural changes). Mini Symposia fr Wed, 03 Mar 2021 09:34:51 +0100 Wed, 14 Apr 2021 09:54:55 +0200 https://popups.uliege.be/esaform21/index.php?id=82 0 https://popups.uliege.be/esaform21/index.php?id=316 When modelling a cutting operation, the constitutive model of the machined material is one of the key parameters to obtain accurate and realistic results. Up to now, the Johnson-Cook model is still the most used, even if an increasing number of models, such as the Hyperbolic TANgent (TANH) model, were introduced last years to overcome its limitations and come closer to the actual material behaviour. Experimental tests on dedicated equipment are usually required to identify the parameters of the constitutive models. This paper introduces the Coupled Eulerian-Lagrangian (CEL) formalism to model in 3D the Taylor impact test, one of the common tests to perform that parameters identification. Indeed, one identification way involves modelling the test to determine the constitutive model parameters by comparing the experimental and the numerical samples geometries. The developed CEL model is validated against a Lagrangian reference model for a steel alloy and the Johnson-Cook constitutive model. The main goal of using the CEL method is to get rid of the elements distortion due to the high strains and strain rates during the test. Mesh dependence of the results is highlighted and a recommendation is provided on the mesh to adopt for future work. The CEL model of the 3D Taylor impact test is then extended to the use of the TANH model. The results are finally compared with that of the Johnson-Cook constitutive model. Fri, 19 Mar 2021 08:52:29 +0100 https://popups.uliege.be/esaform21/index.php?id=316 https://popups.uliege.be/esaform21/index.php?id=455 For economic or process-related reasons, punching of structural sheet metal components often has to be used for car bodies. The difference in angle of attack between punch and sheet metal component is referred to as “slant angle”. However, at the current state of the art, no precise information is available on the characteristics of cutting surfaces in relation to the slant angles. For this reason, cost-intensive slider units are used for comparatively small slant angles of around 10° in order to ensure series suitability of corresponding punching processes. In this respect, recent studies performed by the authors have shown that good cutting surface qualities can also be achieved for slant angles distinctly beyond 10°. This contribution presents an empirical test series for the characterization of cutting surface parameters when punching with a slant angle. Here, the experimental cutting surface analysis showed an asymmetric characteristic of the cutting surface along the hole circumference. Furthermore, the investigated sheet metal materials HC340LA, DP600 and DP800 revealed recurring tendencies regarding the parameters “edge draw-in”, “clean cut”, “fracture surface” and “burr height”, which had been combined to corresponding three-dimensional regression models. With these regression models, cutting simulations could be calibrated, allowing a quality prognosis of cutting surfaces achievable when punching at specific slant angles. Fri, 19 Mar 2021 21:43:42 +0100 https://popups.uliege.be/esaform21/index.php?id=455 https://popups.uliege.be/esaform21/index.php?id=908 Tool wear remains of high interest for industry, as it influences process costs and part’s surface integrity. Although experimental and analytical investigations have been the main ways to investigate wear, the growing development of computational power enables predicting tool wear based on chip formation simulations. If this has been quite successful in turning, developments in milling are still limited due to the specific nature of this machining operation characterized by an interrupted cutting process leading to mechanical and thermal cyclic loadings onto the cutting tool. Wear modes are often not well characterized and become even more difficult to model as far as hard to machine material such as martensitic stainless steels are concerned. The present work propose to investigate wear in orthogonal milling of a 15-5PH martensitic stainless steel. An experimental campaign is first performed to identify the wear modes when cutting this material with uncoated and coated carbide tools. Milling forces, tool wear and material transfer are especially studied. A multi-scale numerical procedure is then developed by combining an Arbitrary-Lagrangian-Eulerian (ALE) thermomechanical model to a pure thermal sub-model in order to predict the thermomechanical loadings withstood by the tool. The thermal sub-model is applied at the scale of the coating in order to extract the thermal gradients generated by the interrupted cutting. These loadings are finally compared to the reported wear modes to identify a correlation and improve their understanding. Mon, 22 Mar 2021 09:59:54 +0100 https://popups.uliege.be/esaform21/index.php?id=908 https://popups.uliege.be/esaform21/index.php?id=918 The shortest possible tool stickout has been the traditional go-to approach with expectations of increased stability and productivity. However, experimental studies at Danish-Advanced-Manufacturing-Research-Center (DAMRC) have proven that for some tool stickout lengths, there exist local productivity optimums when utilizing the Stability Lobe Diagrams for chatter avoidance. This contradicts with traditional logic and the best practices taught to machinists. This paper explores the vibrational characteristics and behaviour of a milling system over the tool stickout length. The experimental investigation has been conducted by tap testing multiple endmills where the tool stickout length has been varied. For each length, the modal parameters have been recorded and mapped to visualize behavioural tendencies. The insights are conceptualized into a tool tuning approximation solution. It builds on an almost linear change in the natural frequencies when amending tool stickout, which results in changed positions of the Chatter-free Stability Lobes. Validation tests on the tool tuning approximation solution have shown varying success of the solution. This outlines the need for further research on the boundary conditions of the solution, to understand at which conditions the tool tuning approximation solution is applicable. Mon, 22 Mar 2021 10:02:42 +0100 https://popups.uliege.be/esaform21/index.php?id=918 https://popups.uliege.be/esaform21/index.php?id=1505 In manufacturing, hybrid systems of metal additive manufacturing and cutting in the same platform have been attractive in terms of low volume production of customized parts, complex shape, and fine surface finish. Milling is conducted to finish rough surface fabricated in additive process. The fundamental machinability of the additive workpiece should be studied because the material properties are different from metals produced in the conventional process. The paper discusses the cutting forces in milling of AISI 420 stainless steel fabricated in additive process. The cutting tests were conducted to measure the cutting forces and the chip morphologies for tool geometries. The cutting forces were also analyzed in an energy-based force model. In the analysis model, three-dimensional chip flow is interpreted as a piling up of orthogonal cuttings in the planes containing the cutting velocities and the chip flow velocities, where the cutting model is made by the orthogonal cutting data acquired in cutting tests. The chip flow direction is determined to minimize the cutting energy. The cutting forces, then, were predicted in the determined chip flow model. The cutting force model was validated in comparison of simulated forces with the actual ones. Mon, 22 Mar 2021 20:04:28 +0100 https://popups.uliege.be/esaform21/index.php?id=1505 https://popups.uliege.be/esaform21/index.php?id=1878 Drilling operations lead to temperatures and forces that may locally reach significant magnitude and thus impair the surface and material integrity. Optimizing the cutting conditions could limit these degradations, which are more significant in the case of low thermal conductivity materials such as titanium alloys. Robust numerical modelling is a relevant alternative to such issues but must rely on strong in-process experimental measurements. Unfortunately, the confined nature of the cutting area during drilling prevent from any straight forward field-measurement. The proposed multi-scale strategy consists in validating the developed 3D FEM models both at micrometric and millimetric scales, using coupled full-field measurements. The limited access to the cutting area is overcome by means i) of oblique cutting tests at microscale and ii) tube drilling tests. Thermal fields are evaluated using an infrared camera while kinematic fields are determined by image correlation (DIC) using a high-speed camera. The experimental and numerical fields are then compared, and numerical results are extended over several revolutions by means of purely thermal 2D analytical model. Tue, 23 Mar 2021 10:08:38 +0100 https://popups.uliege.be/esaform21/index.php?id=1878 https://popups.uliege.be/esaform21/index.php?id=1903 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 configuration is able to successfully modify the surface characteristics of the steel, making it appropriate for critical applications. Furthermore, the experimental findings allow to conclude that burnishing process can replace a series of post processes needed after additive manufacturing, drastically reducing the time and costs associated to the manufacturing process and meeting Industry 4.0 requirements. Tue, 23 Mar 2021 10:33:26 +0100 https://popups.uliege.be/esaform21/index.php?id=1903 https://popups.uliege.be/esaform21/index.php?id=2107 Nickel based superalloys, such as Waspaloy, are extensively used to manufacture components that operate under high temperature cyclic loads, because of their superior chemical and thermo-mechanical properties. In particular, these artifacts are mainly produced by shaping and/or finishing machining operations. Despite of their huge properties, these alloys show an extremely poor workability, that makes them part of the group of the so called difficult-to-cut materials. Therefore, the proper selection of the machining conditions is always challenging for the designers. In this context, predictive models represent an extremely useful tool to numerically simulate the machining process, guaranteeing a good knowledge of the material behavior under machining conditions, and avoiding expansive and time consuming experimental campaigns. Besides, the proper selection of the material rheological model is of fundamental importance in order to obtain precise and affordable results from the numerical model. In this work a Johnson-Cook based viscoplastic flow behavior model was proposed. The model was obtained from Artificial Neural Network (ANN) based interpolation techniques and validated using orthogonal machining experimental tests. Moreover, the proposed model was compared with other rheological models available from literature to benchmark their affordability and assessing their performances. Tue, 23 Mar 2021 12:48:40 +0100 https://popups.uliege.be/esaform21/index.php?id=2107 https://popups.uliege.be/esaform21/index.php?id=2224 Increased stability in machining processes is highly desired by all machining industries when vibrations and specially chatter occur. This phenomenon is defined as a self-excited vibration that occurs due to the regeneration of waviness of the workpiece surface. In machining industry, the trend is to rely on the trial and error method or mere experience when deciding the machining spindle speeds, depths of cut and tool stick-outs, all of which are parameters directly related to chatter occurrence. Currently, the shortest possible tool stick-out is chosen by default, but literature has proven that longer stick-outs may bring some advantages when it comes to material removal rates. Aiming to prove this theory, this paper will discuss the influence of the tool stick-out on machining chatter occurrence. To that end, the effect of the tool stick-out on the modal parameters of the system, on the Stability Lobe Diagram (SLD) and on productivity will be analysed. Therefore, a number of Tap-Tests to different tool/tool-holder/stick-out combinations have been performed, in order to gather the data (FRFs and SLDs) where the analysis is based on. Last but not least, some machining tests have been conducted aiming to compare the theoretical chatter occurrence conditions, provided by the SLD, with the experimental ones. For that, two Al5083 workpieces have been slot milled under different cutting conditions, facilitating the unexpected results wherein the conclusions have been based upon. Tue, 23 Mar 2021 14:42:49 +0100 https://popups.uliege.be/esaform21/index.php?id=2224 https://popups.uliege.be/esaform21/index.php?id=2373 Composites materials and especially FRP are increasingly employed in many fields of applications (transport, aerospace, …) due to the current trend of improving global energy performances of new designs notably by mass saving. However the use of metallic materials such as aluminum and titanium alloys is still necessary in many cases and a lot of structures are made of a dual technology called stacks (panels composed of different layers of FRP and metal bounded together). Combining the different properties of these materials offers many advantages regarding the mechanical and structural aspects. This is nevertheless for the same reason that machining and especially drilling stacks is a laborious task: the tools and cutting conditions are way too divergent to avoid vibrations, problems of dimensional tolerances and delamination of the composite. The knowledge and characterization of the drilling cutting forces is a first step to solve these issues. The purpose of this article is to provide an accurate macroscopic analytical model fitted for stacks and compare it quantitatively with experimental tests. The given model is divided in two parts (i.e. respectively adapted for the two materials) and is based on the discretization of the cutting edge. The proposed algorithm is able to predict accurately drilling force and torque along time in function of the cutting conditions, the tool and material configurations. A reverse least squared method is used to obtain the empirical input parameters, allowing to minimize the number of experimental drilling tests to obtain the empirical input parameters. Tue, 23 Mar 2021 18:03:56 +0100 https://popups.uliege.be/esaform21/index.php?id=2373 https://popups.uliege.be/esaform21/index.php?id=2424 The highly used Ti6Al4V alloy is a well know hard-to-machine material. The modelling of orthogonal cutting process of Ti6Al4V attract the interest of many researchers as it often generates serrated chips. The purpose of this paper is to show the significant influence of cutting speed on chip formation during orthogonal cutting of Ti6Al4V along with different material constitutive models. Finite element analyses for chip formation are conducted for different cutting speeds and are investigated with well-known Johnson-Cook constitutive model, a modified Johnson–Cook model known as Hyperbolic Tangent (TANH) model that emphasizes the strain softening behavior and modified Johnson-Cook constitutive model that consider temperature dependent strain hardening factor. A 2D Lagrangian finite element model is adopted for the simulation of the orthogonal cutting process and the results from the simulations such as calculated forces, chip morphologies are analyzed and are compared with the experimental results to highlight the differences. The results analysis shows that, the temperature in the secondary deformation zone is directly proportional to the cutting speed. Tue, 23 Mar 2021 18:41:10 +0100 https://popups.uliege.be/esaform21/index.php?id=2424 https://popups.uliege.be/esaform21/index.php?id=2459 Machining continues to dominate the market among manufacturing processes requiring in-depth investigation on how material removal processes influence the surface integrity of the products. In this paper, experimental studies were carried out to evaluate the influence of several process parameters on surface integrity changes of Ti6Al4V alloy and to improve the overall process/product performance. In particular, orthogonal cutting operations were conducted varying the process parameters as cutting speed, feed rate and cooling conditions (dry, MQL and cryogenic cooling). Product quality specifications have been monitored in terms of microstructure, hardness modification, phase changes, also including tool wear analysis. Indeed, a systematic study is necessary since various factors are simultaneously involved, as well as changes during processing. Thus, due to the complexity of the process and the number of factors involved, the analysis of variance (ANOVA) was performed to optimize the process through the identification of significant parameters to maximize the useful tool-life and minimize the time of production. Tue, 23 Mar 2021 19:15:08 +0100 https://popups.uliege.be/esaform21/index.php?id=2459 https://popups.uliege.be/esaform21/index.php?id=3749 In recent years, polymeric materials are being used at an increasing rate in the biomedical industry. In particular, Ultra-High-Molecular Weight Polyethylene (UHMWPE), a thermoplastic polymer characterized by high toughness, good chemical stability and self-lubricating properties, is an ideal candidate for the manufacture of bearing implants used in hip or knee replacements. Nevertheless, it is difficult to achieve a good level of surface finish when turning it, because of its high instability at increasing temperature. In the present study, cryogenic machining was applied instead of dry cutting to machine a biomedical grade UHMWPE at different cutting speeds. The surface finish was assessed in terms of surface roughness, crystallinity degree and hardness in correspondence of the surface. To correlate machinability results with the UHMWPE mechanical behaviour, uniaxial tensile tests were performed in a wide range of temperatures. The obtained results showed that the application of cryogenic machining was an efficient mean to increase the surface finish: in fact, smoother and harder surfaces were obtained regardless of the adopted cutting parameters. Mon, 29 Mar 2021 14:24:30 +0200 https://popups.uliege.be/esaform21/index.php?id=3749 https://popups.uliege.be/esaform21/index.php?id=3793 Plunge milling is a critical process step in mass manufacturing of rectangular shapes in electrical connector components. These shapes are manufactured by drilling a pilot hole and subsequent plunge milling with a radial offset (pitch) one or more times. The plunged cavity serves as guidance for the final broaching cut. In light of new legislative initiatives, the electronics industry is forced to use lead-free Cu-Zn-Alloys for mass manufacturing of these connectors. The plunging tool is deflected due to the higher cutting forces experienced in machining of lead-free CuZn-alloys in comparison to alloys with lead. This results in an offset of the milled cavity and negatively impacts tool guidance in the subsequent broaching process. Therefore, the geometric tolerances cannot be met. In this paper, the effect of tool geometry and cutting parameters on the workpiece geometry in plunge milling is investigated. The effect of the microstructure of the work-piece materials CuZn37, CuZn42 and CuZn21Si3P on the tool deflection and cutting force components is examined. The tools used vary regarding the design of the corner in terms of the corner chamfer and the inner shaft thickness. Friction between chips in the tools inner flutes and the cavity walls reduced workpiece accuracy. Improvements were achieved by reducing the width of the cutting corner chamfers, using large inner flutes and applying low cutting parameters. Mon, 29 Mar 2021 14:39:29 +0200 https://popups.uliege.be/esaform21/index.php?id=3793 https://popups.uliege.be/esaform21/index.php?id=3844 Hybrid structures made of fiber-reinforced plastics (FRP) and metals are currently in focus of research and industry to develop weight reduced and functional optimized components for lightweight solutions. Manufacturing processes were adapted and developed to produce components based on hybrid materials with high economic efficiency. The cutting process is used to pre-assemble the semi-finished products or to post-process the edges of consolidated parts. The mechanisms of damage edge behavior and possible cutting qualities on these parts are not investigated jet. To close this knowledge gap and to support the future application of hybrid FRP-Metal-Laminates different cutting procedures were studied. This paper shows the process related dependences on the failure behavior of two dimensional specimens. The failure modes are described via quality characteristics like surface roughness, trueness and precision of the cut as well as influences of aging processes. In the end optimized parameter for each process are shown and compared under technical and economic criteria for large scale production. In the scope of this work an experimental study of piercing of glass and carbon fiber reinforced thermoplastic with different steel and bonding agents at different cutting sequences were performed. It was shown that the cutting edge geometry significantly differs. Possible mechanical explanations of the dependencies were formulated. Also the accuracy of the cuts was evaluated which showed a higher accuracy for the steel component. The measurements on the surface roughness could not show any dependencies and relations. Mon, 29 Mar 2021 14:49:59 +0200 https://popups.uliege.be/esaform21/index.php?id=3844 https://popups.uliege.be/esaform21/index.php?id=4212 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 focuses on a multi-scale characterization of the influence of AWJ process parameters (pressure, traverse speed, step-over distance and abrasive size) on surface roughness, depth of cut, abrasive embedment and residual stress, during milling of untreated IN718. Surface integrity characterization on the milled surfaces was conducted through 3D optical microscopy, profilometry and SEM techniques. Residual stress measurements were performed in longitudinal and transverse directions with respect to the machining path using XRD technique. The results showed that all milled surfaces presented abrasive embedment and a compressive residual stress state with similar values in both directions. Up to 15% of the area of a milled surface consisted of abrasive embedment. The tool path has not influenced the residual stresses. Furthermore, surface roughness is dependent on pressure and traverse speed; depth of cut is influenced by pressure, traverse speed and grit size; abrasive embedment depends on pressure, step-over distance and grit size; whilst, residual stresses are influenced by traverse speed and grit size. Thu, 01 Apr 2021 16:20:25 +0200 https://popups.uliege.be/esaform21/index.php?id=4212 https://popups.uliege.be/esaform21/index.php?id=4246 Sustainable machining involves the use of environmentally friendly cooling and lubrication fluids. A novel approach of lubricated liquid carbon dioxide (LCO2) can be used to replace conventional cutting fluids while promising benefits such as cleaner machining and higher productivity. In this study, milling of martensitic stainless steel was performed under different cooling and lubrication conditions (dry, flood, LCO2, LCO2 + MQL). Cutting tool (ball end mill, d = 8mm) was protected by a TiAlSiN PVD hard coating, while the same uncoated tool was used as a reference. Tool life time measurements were taken under different cooling and lubrication conditions at pre-determined time intervals, until the critical tool wear of 0.2 mm was reached on the flank face. At the same time, thermocouples were inserted into the workpiece to measure the temperature directly below the cutting zone. The influence of different cooling and lubrication conditions on surface roughness parameters was also investigated. From the experimental results, surprisingly, conventional flooding machining outperformed LCO2 and LCO2 + MQL assisted machining in terms of surface roughness. Moreover, the TiAlSiN coated tool exhibited roughly three times longer tool life time when compared to the uncoated tool at the same machining conditions. Whereas both, LCO2 and LCO2 + MQL cooling/lubricating strategies significantly reduce the temperature in the cutting zone, dry machining strategy provides the longest tool life time. Thu, 01 Apr 2021 17:15:38 +0200 https://popups.uliege.be/esaform21/index.php?id=4246 https://popups.uliege.be/esaform21/index.php?id=4284 Austenitic and duplex stainless steels are considered be the best in corrosion resistance among different grades of stainless steels. Due to high strength, duplex stainless steels applications are increasingly as an alternative to the austenitic stainless steels. In this sense, the machining study of this materials is an important issue, in order to better understand the performance of the tools and the quality of the parts manufactured for high-demand industries. In this research, the machinability of both stainless steels was evaluated in the drilling operation, using drills with three cutting edges. This type of drill geometry is particularly useful when conventional solid carbide drills fail. The drill point of triple edge is very stable, demonstrating optimal positioning accuracy and better performance in deep bores. Using the same tool geometry, a comparative analysis of drilling performance on austenitic and duplex stainless steels was made. In experimental procedure, external low-pressure cooling or internal high-pressure cooling was applied alternatively. The cutting vibration, the tool wear, the roughness and the hole diameter accuracy were evaluated in the series of holes made. The obtained results show that the most important factor to increase the number of holes made is the use of high-pressure internal cooling. When external cooling is used, AISI 304 have a worse behaviour than duplex stainless steel, due to greater susceptibility to built-up-edge formation and work hardening. The tool deterioration is mainly non-uniform chipping for external cooling and flank wear for internal cooling. Thu, 01 Apr 2021 17:49:43 +0200 https://popups.uliege.be/esaform21/index.php?id=4284 https://popups.uliege.be/esaform21/index.php?id=4302 The phenomenon of tool wear strongly affects the efficiency of machining and the quality of machined products. The experimental approach to investigate tool wear requires several time consuming tests. Finite Element Methods (FEM) can be utilized to predict tool wear and tool life as function of process parameters and tool geometry. The commercial software for Finite Element Analysis (FEA) are limited by the impossibility to update the geometry of the worn tool. This research utilizes a self-released subroutine in order to modify the tool geometry in DEFORM 3D simulations by considering the volume reduction of the tool. The model was validated with experimental data obtained by drilling tests on Inconel 718 using conventional metal working fluids (MWF). The correct profile of the simulated worn tool was individuated by comparing the prediction of the simulation with the real tool geometry. The FEM simulation allowed to predict how torque changes during the tool life. In a predictive maintenance perspective, the model can be implemented to optimize the tools replacement. Thu, 01 Apr 2021 17:57:27 +0200 https://popups.uliege.be/esaform21/index.php?id=4302