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Broaching operations require stiff machine tools that have to withstand high cutting forces. This work aims to develop a methodology to predict the macroscopic cutting forces on a real, internal broaching operation comprising a large number of teeth. The macroscopic forces are estimated, based on the addition of local forces that are applied to each section and are simultaneously in contact with the broach. These local forces are calculated using a model of specific cutting pressure, depending on the rise per tooth. This study uses two methods to identify this specific cutting pressure model, that is, a direct approach based on orthogonal cutting tests and an inverse approach based on an instrumented broaching operation. It is shown that the direct method is effective in identifying a specific cutting pressure model and enables the prediction of macroscopic forces. Moreover, the direct approach provides more comprehensive results in terms of radial forces.

In this study, artificial neural networks (ANNs) were used to study the effects of machinability on cutting parameters during turning of the cobalt alloy (Stellite 6). Cutting forces with three axes (Fx, Fy and Fz) were predicted by changing the tool tip radius (r), cutting speed (Vc), feed rate (f) and cutting depth (ap) with conventional lubrication. Experimental studies were conducted to obtain training and test data and a feed-forward back-propagation algorithm was used in the networks. The main test parameters are the tool tip radius (r, mm), cutting speed (Vc, m/min), feed rate (f, mm/rev), cutting depth (ap, mm) and cutting forces (Fx, Fy and Fz, N). r, Vc, f and ap were used as input data while Fx, Fy and Fz were used as output data. The mean percentage values of root mean square error (RMSE), mean absolute percentage error (MAPE) and mean absolute deviation (MAD) for Fx, Fy and Fz using the proposed models were obtained around 2 and 4.79%, respectively for training and testing. These results show that ANNs can be used to predict the effects of machinability on cutting parameters when cutting Stellite 6 on turning process. The results highlighted the performance of the studied configuration.

International audience; The wear of cutting tools remains a major obstacle. The effects of wear are not only antagonistic at the lifespan and productivity, but also harmful with the surface quality. The present work deals with some machinability studies on flank wear, surface roughness, and lifespan in finish turning of AISI 304 stainless steel using multilayer Ti(C,N)/Al2O3/TiN coated carbide inserts. The machining experiments are conducted based on the response surface methodology (RSM). Combined effects of three cutting parameters, namely cutting speed, feed rate and cutting time on the two performance outputs (i.e. VB and Ra), and combined effects of two cutting parameters, namely cutting speed and feed rate on lifespan (T), are explored employing the analysis of variance (ANOVA). The relationship between the variables and the technological parameters is determined using a quadratic regression model and optimal cutting conditions for each performance level are established through desirability function approach (DFA) optimization. The results show that the flank wear is influenced principally by the cutting time and in the second level by the cutting speed. In addition, it is indicated that the cutting time is the dominant factor affecting workpiece surface roughness followed by feed rate, while lifespan is influenced by cutting speed. The optimum level of input parameters for composite desirability was found Vc1-f1-t1 for VB, Ra and Vc1-f1 for T, with a maximum percentage of error 6.38%.

Manufacturers need to continuously improve productivity and reduce the most disadvantages. In the current work, an experimental study has been carried out in order to evaluate the influence of different cutting parameters on the various machining factors such as surface roughness, cutting force, cutting power, metal removal rate, and tool wear during turning of X210Cr12 steel using a multilayer-coated tungsten carbide insert with various nose radii (r). Tests are designed according to Taguchi’s L18 (21 × 34) orthogonal array. ANOVA has been performed to determine the effect of the cutting conditions, and mathematical models have been developed through response surface methodology (RSM). The results indicate that the feed rate and the tool nose radius are the main affecting factors on surface roughness while both tangential force and cutting power are affected mainly by the depth of cut followed by the feed rate and the nose radius. Other special tests of long term have been established in order to study the wear evolution and consequently to determine the tool life. The results indicate also that minimum quantity lubrication (MQL) leads to an important improvement in terms of the cutting tool life by a gain of 23~40% compared to wet and dry machining. It has been found that the MQL is an interesting way to minimize lubrication cost and protect operator health and the environment while keeping better machining quality.

Broaching is a productive and accurate process generating complex surfaces with high quality. In this process, cutting mechanisms occurring are very specific regarding conventional cutting (small uncut chip thickness, low cutting speeds, long encapsulated chips). However, few research have been conducted on this process and in particular in the topic of simulation. For that, an original Lagrangian model that enables to simulate long cutting time by means of an iterative procedure has been developed. Cutting forces, temperatures evolutions and chip morphology obtained with this model have been compared with results from experimental tests and ALE simulations.

Post-machining part distortions are commonly observed in thin-walled machined structures. This problem is intensified if the machined part is cellular, curved in profile, and complex in design. Different customized techniques are executed to overcome this issue and to attain the desired dimensional accuracy. This problem instigates mainly due to redistribution of material-induced residual stress subsequent to machining operations. Research work presented here deals with numerical and experimental investigations of part distortions encountered in thin-walled machined structures. Computational analysis and manufacturing simulations of cutting operations are executed in ANSYS® software. Computational work is validated through actual experimentation on a computerized numerical controlled machine with optimum cutting parameters. Coordinate measuring machine (CMM) geometric inspection is carried out to determine the attained machining accuracy. Material-induced residual stress is developed through sequential coupled field thermo-mechanical analysis. Large-scale cutting simulations are performed in an optimized sequence by employing element birth–death feature. Simulation predicted distortions and CMM statistics is evaluated, and it was found that both corroborate with each other. This validates the approach adopted to predict part distortions.

Johnson-Cook constitutive model is still the most used model in metal cutting simulation, although several drawbacks reported in the literature. A high number of Johnson-Cook model parameters can be found in the literature for the same work material. One question that may arise is “What is the most suitable set of Johnson-Cook model parameters for a given material?”. The present paper puts in evidence some issues related with the selection of these parameters from the literature. In this contribution, two sets of Johnson-Cook model parameters for Ti-6A-4 V are evaluated, using three types of metal cutting models. These models are based on three different formulations: Lagrangian, Arbitrary Eulerian-Lagrangian (ALE) and Couple Lagrangian-Eulerian (CEL). This evaluation is based on the comparison between measured and predicted chip geometry, chip compression ratio, forces, plastic deformation and temperature distributions.

International audience; The present work concerns an experimental study dealing with cutting parameters’ effects on the surface roughness, cutting force, cutting power, and productivity during turning of the polyoxymethylene (POM C) polymer. For that, a cutting tool made of cemented carbide was used. The work is divided into three steps. The first one deals with unifactorial tests, where the evolution of the machining parameters (roughness criteria, cutting force components, and cutting power) is investigated by varying cutting speed, feed rater, and depth of cut. The second part concerns the modeling of the output parameters: arithmetic roughness, cutting force, cutting speed, and material removal rate by using the results of a full factorial design (L27). The second step concerns the adoption of the two modeling techniques, which are the response surface methodology (RSM) and the artificial neural network (ANN). The obtained results related to two both techniques are compared in order to discern the most efficient one. The last step of the present research work concerns the multi-objective optimization using the desirability function (DF). The optimization was carried out according to three approaches, which are the “quality optimization,” “productivity optimization,” and the combination between the quality and productivity.

International audience; This paper is an attempt to compare artificial neural networks and response surface methodology for modeling surface roughness and cutting force in terms of better coefficient of determination (R2), lower root mean square error (RMSE) and model predictive error (MPE). Models were developed based on three-level Box-Behnken design (BBD) of experiments with 15 experimental runs composed of three center points, conducted on Inconel 718 work material using coated carbide insert with cutting speed, feed rate and depth of cut as the process parameters under dry environment. Results show that the artificial neural network (ANN) compared with RSM is a better reliable and accurate approach for predicting and detecting the non-linearity of surface roughness and cutting force mathematical models in terms of correlation and errors. Indeed, the ANN prediction model provides a maximal benefit in terms of precision of 10.1% for cutting force (Fv) and 24.38% for surface roughness (Ra) compared with the RSM prediction model.

International audience; Inconel 718 is among difficult to machine materials because of its abrasiveness and high strength even at high temperature. This alloy is mainly used in aircraft and aerospace industries. Therefore, it is very important to reveal and evaluate cutting tools behavior during machining of this kind of alloy. The experimental study presented in this research work has been carried out in order to elucidate surface roughness and productivity mathematical models during turning of Inconel 718 superalloy (35 HRC) with SiC Whisker ceramic tool at various cutting parameters (depth of cut, feed rate, cutting speed and radius nose). A small central composite design (SCCD) including 16 basics runs replicated three times (48 runs), was adopted and graphically evaluated using Fraction of design space (FDS) graph, completed by a statistical analysis of variance (ANOVA). Mathematical models for surface roughness and productivity were developed and normality was improved using the Box-Cox transformation. Results show that surface roughness criterion Ra was mainly influenced by cutting speed, radius nose and feed rate, and that the depth of cut had major effect on productivity. Finally, ranges of optimized cutting conditions were proposed for serial industrial production. Industrial benefit was illustrated in terms of high surface quality accompanied with high productivity. Indeed, results show that the use of optimal cutting condition had an industrial benefit to 46.9 % as an improvement in surface quality Ra and 160.54 % in productivity MRR.

In this study, an attempt has been made to statistically model the relationship between cutting parameters (speed, feed rate and depth of cut), cutting force components ( Fx, Fy and Fz) and workpiece absolute surface roughness ( Ra). The machining case of a martensitic stainless steel (AISI 420) is considered in a common turning process by means of a chemical vapor deposition–coated carbide tool. A full-factorial design (43) is adopted in order to analyze obtained experimental results via both analysis of variance and response surface methodology techniques. The optimum cutting conditions are achieved using mutually response surface methodology and desirability function approaches while the model adequacy is checked from residual values. The results indicated that the depth of cut is the dominant factor affecting ( Fx: 86%, Fy: 58% and Fz: 81%), whereas feed rate is found to be the utmost factor influencing surface roughness behavior ( Ra: 81%). In addition, a good agreement between the predicted and measured cutting force components and surface roughness was observed. The results are also validated experimentally by determining errors ( Fx: 6.51%, Fy: 4.36%, Fz: 3.59% and Ra: 5.12%). Finally, the ranges for optimal cutting conditions are projected for serial industrial production.

For qualitative prediction of chip morphology and quantitative prediction of burr size, 2D and 3D finite element (FE) based turning models have been developed in this paper. Coupled temperature-displacement machining simulations exploiting the capabilities of Abaqus® with a particular industrial turning insert and a newly proposed geometrical version of this insert have been performed. Limitations of 2D models in defining the chip morphologies and surface topologies have been discussed. The phenomenological findings on the Poisson burr (Side burr) formation using 3D cutting models have been highlighted. Bespoke geometry of the turning insert has been found helpful in reducing the Poisson burr formation, as it reduces the contact pressures at the edges of tool rake face-workpiece interface. Lower contact pressures serve to decrease the material flow towards workpiece edges (out of plane deformation). In contrast, higher contact pressures at tool rake face-workpiece interface lead to more material flow towards workpiece edges resulting in longer burr. Simulation results of chip morphologies and cutting forces for turning an aluminum alloy A2024-T351 have been compared with the experimental ones. Finally, it has been concluded that the newly proposed geometry of the insert not only decreases the burr but also helpful in lessening the magnitude of tool-workpiece initial impact.

This contribution presents three-dimensional turning operation simulations exploiting the capabilities of finite element (FE) based software Abaqus/Explicit. Coupled temperature-displacement simulations for orthogonal cutting on an aerospace grade aluminum alloy AA2024-T351 with the conceived numerical model have been performed. Numerically computed results of cutting forces have been substantiated with the experimental data. Research work aims to contribute in comprehension of the end-burr formation process in orthogonal cutting. Multi-physical phenomena like crack propagation, evolution of shear zones (positive and negative), pivot-point appearance, thermal softening, etc., effecting burr formation for varying cutting parameters have been highlighted. Additionally, quantitative predictions of end burr lengths with foot type chip formation on the exit edge of the machined workpiece for various cutting parameters including cutting speed, feed rate, and tool rake angles have been made. Onwards, to investigate the influence of each cutting parameter on burr lengths and to find optimum values of cutting parameters statistical analyses using Taguchi&rsquo, s design of experiment (DOE) technique and response surface methodology (RSM) have been performed. Investigations show that feed has a major impact, while cutting speed has the least impact in burr formation. Furthermore, it has been found that the early appearance of the pivot-point on the exit edge of the workpiece surface results in larger end-burr lengths. Results of statistical analyses have been successfully correlated with experimental findings in published literature.

This article presents the development of two-dimensional and three-dimensional finite element–based turning models, for better prediction of chip morphology and machined surface topology. Capabilities of a commercial finite element code Abaqus®/Explicit have been exploited to perform coupled temperature–displacement simulations of an aerospace grade aluminum alloy A2024-T351 machining. The findings show that two-dimensional cutting models predict chip morphologies and machined surface textures on a plane section (with unit thickness) passing through the center of workpiece width, and not at the edges. The contribution highlights the importance of three-dimensional machining models for a close corroboration of experimental and numerical results. Three-dimensional cutting simulations show that a small percentage of material volume flows toward workpiece edges (out of plane deformation), augmenting the contact pressures at the edges of tool rake face–workpiece interface. This enhances the burr formation process. Computational results concerning chip morphologies and cutting forces were found in good correlation with experimental ones. In the final part of the article, numerical simulation results with a modified version of a particular turning tool have been discussed. It has been found that the proposed geometry of the tool is helpful in reducing burr formation as well as cutting force amplitude during initial contact of cutting tool with the workpiece material.

The present paper highlights the importance of size effect consideration during the modelling of material removal by cutting tool, especially when passing from maco-to-micro scales. For that, the presented study concerns an orthogonal case of down-cut milling where the chip thickness is evolving. Consequently, to capture the scale effect when passing from macro to micro dimensions, the theory of gradient plasticity were adopted.

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

Broaching is a productive and accurate process generating complex surfaces with high quality. In this process, cutting mechanisms occurring are very specific regarding conventional cutting because of the small uncut chip thickness, the low cutting speeds and the long chips encapsulated in a narrow groove. However few researches have been conducted on this process and in particular in the topic of simulation. For that, two numerical models have been developed: a common Arbitrary Lagrangian-Eulerian model (ALE) and an original lagrangian model that enables to simulate long cutting time by means of an iterative procedure. This has allowed numerical results regarding cutting forces and temperatures evolutions and also the chip morphology. Finally, an experimental set-up has been developed in order to compare numerical and experimental results obtained.

International audience; This contribution deals with a computational investigation highlighting the effects of cutting speed and depth of cut on chip morphology and surface finish for down-cut milling case. the global aim concerns the comprehension of multiphysical phenomena accompanying chip formation in rough, semifinish, and finish cutting operations, exploiting a three-dimensional finite element model. numerical work has been performed in two phases. in the first phase, a three-dimensional model for rough cut operation has been validated with the experimental results, including chip morphology and cutting force evolution for an aerospace grade aluminum alloy a2024-t351. in the second phase, the model has been extended to semifinish and finish three-dimensional cutting operations. the numerical findings show that as depth of cut decreases (toward finish cutting), spatial displacement of workpiece nodes along the depth of cut increases. this represents an increase/extension in the percentage of volume undergoing shear deformation, resulting in higher dissipation of inelastic energy, hence contributing to size effect in finish cutting operation. the results also depict that material strain rate hardening enhances the material strength at higher cutting speeds. these material strengthening phenomena help to generate a smooth continuous chip morphology and better surface texture in high-speed finishing operations. the study highlights the significance of three-dimensional numerical modeling to better understand the chip formation process in semifinish and finish machining operations, regardless of the immense effort in computational time.

The present study, aims to investigate, under turning conditions of hardened AISI H11 (X38CrMoV5-1), the effects of cutting parameters on flank wear (VB) and surface roughness (Ra) using CBN tool. The machining experiments are conducted based on the response surface methodology (RSM). Combined effects of three cutting parameters, namely cutting speed, feed rate and cutting time on the two performance outputs (i.e. VB and Ra), are explored employing the analysis of variance (ANOVA). Optimal cutting conditions for each performance level are established and the relationship between the variables and the technological parameters is determined using a quadratic regression model. The results show that the flank wear is influenced principally by the cutting time and in the second level by the cutting speed. Also, it is that indicated that the feed rate is the dominant factor affecting workpiece surface roughness.

Long-term wear tests on the CBN tool behaviour during hard turning of AISI D3 (60 HRC) have been investigated. The evolution of surface roughness, cutting forces and temperature has been studied according to the cutting parameters and tool wear. Results show that CBN is resistant to wear despite of aggressiveness of AISI D3 steel. A great part of heat generated is mainly dissipated throughout the chip; at a cutting speed of 320 m/min the chip temperature is found to be 14 times higher than that recorded in the workpiece. The cutting speed range of 90 to 240 m/min has been found suitable to cut this material. The former speed range is appropriate to respect the cutting constraints, whereas beyond 240 m/min a drastic increase in tool wear occurs, causing a remarkable drop in tool life. Roughness measurements reveal a dependence on CBN tool wear. However, although the wear rises up to the allowable flank wear of value 0.3 mm, roughness Ra remains around 1.0 μm. The feed rate remains the most affecting factor...

Improvement in machining efficiency requires better comprehension of multiphysical cutting process phenomenon under real dynamic cutting conditions. Present work suggests a multi-scale interaction of mesoscopic level cutting with macroscopic level machine tool dynamics to optimize cutting process parameters and potentially improve interactive design process. For that, the case of an orthogonal down-cut peripheral milling, for an aeronautic aluminium alloy A2024-T351, has been treated. A finite element based multi-scale dynamic cutting model has been conceived with a commercial finite element based code ABAQUS®/EXPLICIT to predict the chip morphology under dynamic cutting conditions. Later, combines the elasticity of a classical high speed milling spindle system (tool, tool-holder and rotor) with the mesoscopic level chip formation process. A qualitative parametric study with various stiffness and damping coefficient values for high speed milling spindle system shows that, a less rigid un-damped milling system generates higher amplitude tool vibrations during cutting. In this situation, the temperature rises at tool-workpiece interface, enhancing material softening. Present study deals with the consequences of this softening on affecting the chip morphology (evolution of segmented chip morphology), and machined surface integrity. Further, numerical simulation results depict that the higher values of cutting speed and uncut chip thickness are associated with higher values of milling cutter vibration amplitudes.

Thermostamping of woven fabrics shows promise for being a viable means for making high-volume low-cost composites. A number of research teams around the world have been developing finite element methods for simulating this thermostamping process, and in an effort to understand the strengths and limitations of the different simulation methods, an international benchmark survey was conducted for a double-dome geometry. Comparisons were made by observing the resulting draw-in of the fabric and shear angles developed in the fabric after stamping. In this paper, simulations results as submitted by the various research teams are compared. Where possible, the simulation results are compared to experimental data. Forming parameters for a next round of simulations for comparison amongst the participating labs are presented.

Continuous textile reinforcements hold crucial role when composites are employed as load bearing components. Numerical simulations of the composite forming processes are essential in the design phase of the composite structures. The continuous approach predicts the mechanical characteristics of woven composite fabrics during forming which considers the fibrous materials as a continuum in average at macroscopic scale. An algorithm based on a hypoelastic behaviour is proposed for the simulation of composite reinforcement forming processes. It is shown here that using hypoelastic law with an objective derivative based on the warp and weft fibre rotation tensors can correctly trace the specific behaviour of the woven materials. A number of elementary tests validate the numerical output with theoretical results and the de facto standard in-plane shear test of picture frame has also been validated numerically. An experimental device for textile composite forming on a double dome has been implemented. This forming case has been defined as an international benchmark of woven composites. The simulations performed with the proposed numerical approach show a good agreement with the experimental results obtained with this double dome device.

International audience; The clear multi-scale structure of composite textile reinforcements leads to develop continuous and discrete approaches for their forming simulations. In this paper two continuous modelling respectively based on a hypoelastic and hyperelastic constitutive model are presented. A discrete approach is also considered in which each yarn is modelled by shell finite elements and where the contact with friction and possible sliding between the yarns are taken into account. Finally the semi-discrete approach is presented in which the shell finite element interpolation involves continuity of the displacement field but where the internal virtual work is obtained as the sum of tension, in-plane shear and bending ones of all the woven unit cells within the element. The advantages and drawbacks of the different approaches are discussed.

The present contribution deals with milling tool vibration effects on chip morphology, cutting force, and cut surface topology. The study concerns an orthogonal down-cut peripheral milling case for aeronautic aluminium alloy A2024-T351. A finite-element-based hybrid dynamic cutting model (HDC model) is proposed to predict the chip morphology under dynamic cutting conditions. The latter is conceived with commercial software ABAQUS®/EXPLICIT and combines the stiffness of a high-speed milling spindle system (tool, toolholder, and rotor) with the chip formation process. A qualitative parametric study with various stiffness and damping coefficient values for a high-speed milling spindle system has been performed. The results concerning chip morphology and cutting force are compared with experimental data, while the surface profiles are compared with those obtained by considering a perfectly rigid spindle system. As expected, a less rigid undamped milling system generates higher-amplitude tool vibrations during milling. In this situation, the temperature rises at the tool—workpiece interface, enhancing material softening. This softening promotes chip segmentation and increases waviness of the machined surface profile. The numerical results show that higher values of cutting speed and uncut chip thickness are associated with higher vibration amplitudes.

Numerical analysis of the forming processes for composite materials has already an acknowledged worth and thus urge to explore even more flexible techniques. The current research is intended to analyse the woven fabric composites using benchmark geometry of double dome for forming. The study has been carried out both experimentally and numerically. The latter has been accomplished by means of a continuous approach; used to analyse numerically the fibrous media exploiting a commercial finite element code i. e. ABAQUS/Explicit. The use of hypoelastic law with an objective derivative based on the fibre rotation tensor makes it possible to track the re-orientation of fibres after deformation. The user material subroutine VUMAT has been developed to incorporate the algorithm and the formulations adopted for fibrous media analysis. The tests have been executed by selecting two different orientations of fabric with respect to the edges of the die or punch. The experimental tests have been duly performed with a local development of forming tools. The digital image correlation (DIC) has also been exploited treating only the final form of the woven reinforcements to measure the shear angles. The numerical results corroborate very well with the experimental output in terms of a number of parameters selected for comparison.

In the present contribution, numerical and experimental methodologies concerning orthogonal cutting are proposed in order to study the dry cutting of an aeronautic aluminium alloy (A2024-T351). The global aim concerns the comprehension of physical phenomena accompanying chip formation according to cutting velocity variation. For the numerical model, material behaviour and its failure criterion are based on the Johnson–Cook law. The model proposes a coupling between material damage evolution and its fracture energy. A high-speed camera was used to capture the chip formation sequences. The numerical results show that the chip–workpiece contact and the tool advancement induce bending loads on the chip. Consequently, a fragmentation phenomenon takes place above the rake face when the chip begins to curl up. The computed results corroborate with experimental ones. The numerical results predict the residual stress distribution and show high values, along the cutting direction, on the machined workpiece surface.

In the present contribution, experimental and numerical methodologies concerning orthogonal cutting are proposed in order to study the dry cutting of an aeronautic aluminium alloy (A2024-T351). The global aim concerns the comprehension of physical phenomena accompanying chip formation with respect to cutting speed, such as chip segmentation and fragmentation. For experimental validation, series of tests are carried out concerning geometrical analysis of the chip; video sequences of chip formation with a high-speed camera, and high-frequency sampling measurements of the cutting force signal are realised. For the numerical approach, the material and its ductile shear failure behaviour are based on the Johnson-Cook laws. The material failure model exploited considers both damage evolution and energy coupling. Numerical results concerning cutting force and segmentation frequency are compared to experimental ones. Moreover,an analysis of damage distributions is presented.

International audience; Surface integrity is extremely affected by manufacturing processes conditions especially the evolution of cutting tool performance. Many researchers, in the domain of material machining, focused their works on the elaboration of models predicting tool wear combining both numerical and experimental approaches. Most of published numerical cutting models simulate the chip formation for a few micro to millisecond time periods. For that, all corresponding experimental tests, needed for the model validation, are usually carried-out in special time conditions which not reflecting industrial situations. Indeed, the latters are characterized by tool wear whose evolution can affect extremely cutting force levels and the final workpiece integrity. In this context, the main purpose of the proposed research work is to develop a FEM model, based on the commercial code ABAQUS, to simulate wear phenomenon of tool insert in the case of orthogonal cutting operation. The present research work is based on a lagrangian approach including an explicit step with the cutting model simulating the chip formation and an Implicit step reproducing the equivalent thermo-mechanical loading applied on the tool. An energetic based wear criterion (EBWC) is integrated in the model to simulate tool wear. Moreover experimentations are carried out to put out wear phenomenon and results are used to validate numerical simulations. They permit to quantify the energy dissipated by friction, which is at the base of the elaboration of the EBWC.

The present paper is a contribution to the investigation of physical phenomena accompanying sawtooth chip formation in the case of hard turning. The study concerns the machining with coated carbide of tempered AISI 4340 steel with a Rockwell C hardness of 47 HRC. The main idea in this paper deals with the establishment of a direct relationship between serrated-chip morphology simultaneously with force component signals derived from acquisition at high frequency and with the width of facets detected on a workpiece machined surface. This experimental work was supported by a numerical simulation based on Abaqus/ Explicit software. Numerical results dealing with effect of temperature evolution on the chip morphology show that the beginning of the sawtooth chip initiation is due to an adiabatic shear at the tool tip with propagation pathway towards the free surface. In addition, computed results have a good corroboration with those obtained experimentally.

In dry turning operation, various parameters influence the cutting force and contribute in machining precision. Generally, the numerical cutting models are adopted to establish the optimum cutting parameters and results are substantiated with the experimental findings. In this paper, the optimal turning parameters of AA2024-T351 alloy are determined through Abaqus/Explicit numerical cutting simulations by employing the Johnson-Cook thermo-viscoplastic-damage material model. Turning simulations were verified with published experimental data. Considering the constrained and nonlinear optimization problem, the artificial neural networks (ANN) were executed for training, testing, and performance evaluation of the numerical simulations data. Two feedforward backpropagation neural networks were developed with ten hidden neutrons in each hidden layer. The Log-Sigmoid transfer function and the Levenberg-Marquardt algorithm were applied in the model. The ANN models were studied with four input parameters: the cutting speed (200, 400, and 800 m/min), tool rake angle (5°, 10°, 14.8°, and 17.5°), cutting feed (0.3 and 0.4 mm), and the contact friction coefficients (0.1 and 0.15).The two target parameters include the tool-chip interface temperature and the cutting reaction force. The performance of the trained data was evaluated using root-mean-square error and correlation coefficients. The ANN predicted values were compared both with the Abaqus simulations and the published experimental findings. All of the results are found in good approximation to each other. The performance of the ANN models demonstrated the fidelity of solving and predicting the optimum process parameters.

The present contribution put forwards a 3D FE approach to perform a parametric study on the effects of depth of cut and cutting speed on surface and chip mor-phologies, for machining an aerospace grade aluminium alloy A2024-T351.The ultimate objective is to improve the comprehension of chip formation phenomenon during rough to finish down cut milling process. Numerical inves-tigations have been realized in two successive steps. Pri-marily, a 3D model for rough cut machining has been de-veloped. Simulation results of later model were compared with the experimental ones. Onwards, numerical models for semi-finish to finish cutting cases were established. It was found that, workpiece nodal displacements along depth of cut are higher for finish cutting operations. This represents an increased percentage of volume under inelastic deformation, resulting in higher energy dissipation. Furthermore, it was numerically found that at higher cutting speeds material strengthens, due to strain rate hardening phenomenon. These strengthening phenomena results in continuous chips and fine quality surface topologies in finish cutting operations, performed at higher cutting speeds. DOI: http://dx.doi.org/10.5755/j01.mech.19.5.5538

Finite element based models for cutting operation present outstanding complexities due to their nonlinear and multi-physics coupling. Nevertheless, there is no uniform standard for the comparison between cutting simulation models based on different software. The present work deals with various methodologies to simulate orthogonal cutting operation for Ti-6Al-4V Titanium alloy inside two commercial codes: ABAQUS and DEFORM. The aim is to show how considered optimal FE numerical approaches can imply agreements or disparities in outputs between the two pre-cited codes. In order to carry out a comparative study between the two codes, similar conditions concerning geometrical models and cutting parameters were adopted. A multi-physic comprehension related to chip formation, cutting forces, temperature evolutions, and surface integrity was presented. Moreover, the numerical results were compared with experimental ones for a deeper discussion on numerical predictions, and problems with current simulation were addressed to improve and support process innovations.DOI: http://dx.doi.org/10.5755/j01.mech.19.3.4656

One of major problems accompanying metal cutting is the appearing of relative vibrations between tool and the machined work-piece. These vibrations are essentially the result of cutting process itself. They can cause a waved machined surface and limit the process performances, severely. These vibrations can also affect tool life-time and lead to a fast harmful of certain machine tool parts (bearings, slides .....). In the present paper a relationship between vibrations and cut surface roughness in the case of turning, throughout a building of mathematical correlation, is proposed. This allows the prediction of roughness based on the knowledge of tool-nose displacements. The latter evaluated from the gathering of signal accelerations. DOI: http://dx.doi.org/10.5755/j01.mech.19.1.3612

This research work concerns the elaboration of a surface roughness model in the case of hard turning by exploiting the response surface methodology (RSM). The main input parameters of this model are the cutting parameters such as cutting speed, feed rate, depth of cut and tool vibration in radial and in main cutting force directions. The machined material tested is the 42CrMo4 hardened steel by Al 2 O 3 /TiC mixed ceramic cutting tool under different conditions. The model is able to predict surface roughness of Ra and Rt using an experimental data when machining steels. The combined effects of cutting parameters and tool vibration on surface roughness were investigated while employing the analysis of variance (ANOVA). The quadratic model of RSM associated with response optimization technique and composite desirability was used to find optimum values of cutting parameters and tool vibration with respect to announced objectives which are the prediction of surface roughness. The adequacy of the model was verified when plotting the residuals values. The results indicate that the feed rate is the dominant factor affecting the surface roughness, whereas vibrations on both pre-cited directions have a low effect on it. Moreover, a good agreement was observed between the predicted and the experimental surface roughness. Optimal cutting condition and tool vibrations leading to the minimum surface roughness were highlighted.

This paper questions the perfect thermal contact conditions usually assumed at the tool-chip interface in machining. Dry orthogonal cutting tests are first conducted on a AISI 1045 steel with TiN coated carbide tools. Tool-chip contact zones are analysed by SEM-EDS and sticking and sliding parts are dissociated. A formation mechanism of a Thermal Contact Resistance (TCR) is proposed from the real contact area extracted. A Finite Element (FE) model based on the Arbitrary-Lagrangian-Eulerian (ALE) approach is then employed to investigate the influence of such thermal contact conditions on the cutting process. Evolution of the main cutting outputs such as average cutting forces, average chip thickness, tool-chip contact length and thermal fields is assessed. It is demonstrated, on one side, that average cutting forces, chip thickness and tool-chip contact length are shown to be insensitive to a TCR. On the other side, heat flux transmitted to the tool, temperature distribution on the tool rake face as well as continuity of temperature across the tool-chip interface are clearly affected depending on its amplitude. This study emphasizes that the existence of a TCR at the tool-chip interface can completely modify local heat partition compared to a perfect thermal contact. The possible occurence of an imperfect contact in machining should be highly considered and modelled based on thermal exchange considerations. Local heat transfer models at the interface are still required to reach more reliable and physically based simulations.

The global aim of this paper is to propose a complete analytical model concerning the material removal. In order to take into account all the aspects of the process, a “phenomena split approach”, based on the assumption that the material removal is the summation of three major contributions, ploughing, spring back and “pure cut” was adopted. This new methodology is developed on the base of experimental tests and industrial experience. In fact the chip is not systematically present. When the chip exists, a part of theoretical layer of the material to be removed is transformed in lateral burrs and elastic compression under the tool tip. In this paper this new approach is presented and the “pure cut” contribution is developed in details. This analytical sub-model of chip formation is calibrated and fitted with a finite element modeling, in order to presents new hypothesis and new formula based on the physics close to the tip of the tool. The chip is considered rigid and uniform, and the regime is supposed stationary. Thermo-mechanical law is applied in shear zones where plastic strain, temperature and strain rate are concentrated. The model takes into account the cutting edge radius too, using an equivalent cutting angle. The friction coefficient at the interface tool-chip is also analytically computed and the present model is considered predictive.DOI: http://dx.doi.org/10.5755/j01.mech.18.6.3161

In this paper, an analytical approach is proposed to model chip formation in the case of turning process. Numerical simulations of chip genesis are performed in order to fit efficiently the proposed analy- tical model. In particular, cutting edge radius influence, temperature and internal stresses distribution are studied using finite element modelling. Numerical model setting is made with experimental and literature data using forces and chip thickness.

Machining processes are widely used in different industries to cut different engineering parts. Usually, optimisation of these processes is made by experimental or numerical simulations. In particular, surface integrity modelling of the final piece is very important for the fatigue behaviour. In this paper modelling of the residual stresses in the fresh workpiece produced is studied. In particular finite element modelling using ABAQUS Explicit is employed in order to simulate chip formation and an implicit static calculation is made to have spring back in the workpiece after cooling. Orthogonal cutting process is chosen because it is simple and practice and different calculations method and numerical options are employed in order to replicate as well as possible physics during the process. In particular it is taken into account the cutting radius of the tool and the boundaries conditions of the workpiece. The setting of the numerical model is executed regarding the experimental conditions used. In the experimental section a complete study of the influence of the residual stresses by process variables (feed, cutting speed) is presented.

The present work deals with the presentation of analytical methodology allowing the modeling of chip formation. For that a “decomposition approach”, based on assuming that the material removal is the summation of two contributions, ploughing and pure cut was adopted. Moreover, this analytical model was calibrated by a finite element model and experimental data in terms of temperature and applied forces evolutions. The global aim is to propose to the industrial community, an efficient rapid-execution analytical model concerning the material removal in the case of an orthogonal cutting process.

Nowadays, numerical simulation of cutting processes receives considerable interest among the scientific and industrial communities. For that, various numerical codes are used. Nevertheless, there is no uniform standard for the comparison of simulation model with these different software. So, it is often not easy to state if a given code is more pertinent than another. In this framework, the present work deals with various methodologies to simulate orthogonal cutting operation inside two commercial codes Abaqus and Deform. The aim of the present paper is to build a common benchmark model between the two pre-cited codes which can initiate other numerical cutting model comparisons. The study is focused on the typical aeronautical material - Ti-6Al-4V - Titanium alloy. In order to carry out a comparative study between the two codes, some similar conditions concerning geometrical models and cutting parameters were respected. A multi-physic comprehension related to chip formation, cutting forces and temperature evolutions, and surface integrity is presented. Moreover, the numerical results are compared with experimental ones.

Present work highlights the importance of material strain rate hardening characteristics as an influential factor in increasing material strength, as uncut chip thickness decreases from macro to micro-level dimensions during down-cut milling process. It has been found for a strain rate dependent material (A2024-T351) that rake face-chip contact length increases nonlinearly when tool approaches to micro-level of uncut chip thickness. This suggests higher energy consumption due to frictional interaction at tool-chip interface, resulting in higher specific cutting energy. In addition, results depict that increase in cutting speeds are attributed to increased rake face-chip contact lengths. Furthermore, to analyze the contribution of the strain gradient hardening on size effect phenomenon during micro cutting operations, modified Johnson-Cook material model (strain gradient-based approach) of the equivalent stress has been formulated in ABAQUS®/EXPLICIT via its user subroutine VUMAT. The results put forward the significance of strain gradient hardening to fully capture the size effect phenomenon du-ring micro cutting operations, at high cutting speeds for a strain rate dependent material. Finally, milling experiments have been performed to validate the numerical model in terms of specific cutting energy and chip morphology. http://dx.doi.org/10.5755/j01.mech.17.1.210

Modeling of metal cutting has proved to be particularly complex, especially for tool-chip interface. The present work is mainly aimed to investigate the limiting shear stress at this interface in the case of Titanium alloy (Ti-6Al-4V) dry cutting based on a FE-model. It was first shown that the surface limiting shear stress is linked to the contact pressure and the coefficient of friction (CoF). A relationship between CoF and the limiting shear stress was given, and the effect of the temperature on the limiting shear stress was also considered. After that, an orthogonal cutting model was developed with an improved friction model through the user subroutine VFRIC in Abaqus/Explicit software. The numerical results obtained were compared with experimental data gathered from literature and a satisfied agreement was found. Finally, the effects of cutting speed, CoF and tool-rake angle on chip morphologies were analyzed.

The present investigation proposes to identify statistically the ranges of strain, strain rate and temperature.

Contrary to the classical continuous media of metallic structures, fibrous composites have a very specific mechanical behaviour due to their composition. The prediction of the properties in simulating the forming processes of woven reinforcements necessitates special analysis methods. The objective of this research work is to present the continuous approach which can be exploited within a commercial code (e.g. ABAQUS, used here). For that we treat, primarily, the elementary tests with continuous approach in large deformations with three different methods i.e. single element with unidirectional fibers, single element with bidirectional fibers and two superimposed elements with unidirectional fibers. The tests are performed using locally developed user material subroutine (VUMAT) for membrane elements in ABAQUS/Explicit. The numerical results of the elementary tests conform with each other and to the exact analytical solutions. Also, these tests are extended to the bias extension test, picture frame test, hemispherical dome forming and the international benchmark draping of double dome. The numerical outputs reasonably corroborate with experimental tests.

The use of composite materials is strongly increasing in aeronautics industry. Consequently there is a need for numerical analysis of these composite components. To perform accurately the service live analyses, it is necessary to know the direction and the density of the fibres at any point of the part. These directions are mainly depending of the forming of the composite. Because they are woven, textile reinforcements can reach very large in‐plane shear strain during manufacturing. A numerical tool that simulates this forming process permits to envisage the feasibility of a process without defect but also to know the directions of the reinforcements after shaping. These directions condition strongly the mechanical behaviour of the final textile composite structure. In addition, the angles between warp and weft yarns influence the permeability of the reinforcement and thus the filling of the resin in the case of a liquid moulding process. The forming of composite reinforcement can be made on a single ply ...

The textile reinforcements used for composites are multiscale materials. A fabric is made of woven yarns themselves composed of thousand of juxtaposed fibres. For the simulation of the draping of these textile reinforcements several families of approaches can be distinguished in function of the level of the modelling. The continuous approaches consider the fabric as a continuum with a specific behaviour. The discrete approaches use models of some components such as the yarns and sometimes the fibres. Different approaches used for the simulation of woven reinforcement forming are investigated in the present paper. Among them, an approach based on semi discrete finite elements made of woven unit cells under biaxial tension and in-plane shear is detailed. The advantage and inconvenient of the different approaches are compared.

This contribution deals with thermo-mechanical effects on chip morphology. Only the case of hard turning of AISI4340 steel (47 HRC) is treated. The study proves that serrated chip formation is the result of a softening phenomenon simulated by using Abaqus/Explicit software. The beginning of the saw-tooth chip initiation is due to an adiabatic shear at the tool tip with a propagation pathway towards the free surface. However, due to heat insulation accompanying a purely adiabatic calculation, it is impossible to simulate the evolution of the thermal field in the cutting tool. In order to stop heat dissipation affecting the model (to respect the adiabatic hypothesis), for the machined workpiece, a fully coupled thermal-stress analysis was adopted with a zero conductivity value of the machined material. Therefore, heat in the workpiece is generated only by material strain and friction. Moreover, a parametric study is proposed of thermal properties such as variations of contact conductance and the fraction of frictional work converted to heat at the tool/workpiece interface.

In manufacturing industry, a high interest in analytical methods are usually researched because there are very practicable to use but those methods do not take into account all the aspects of the contact between the work material and the tool. In particular, ploughing and spring back are usually not considered, which is pertinent for small cutting edge radius but not for bigger ones (used tools). In reality, a part of the work-piece becomes chip and another part slides under the tool (elastic phenomena) and laterally (burrs). A separation line appears between those phenomena and the material under this surface stays in the work-piece during tool action. In this zone, elastic and plastic aspects induce temperature and spring back at the rear of the tool, which is important for residual stresses in the work-piece after cooling. In this paper, a simple analytical formulation is proposed in order to model the separation surface value. This analytical approach is fitted with 2D and 3D numerical simulations and verified with experimental forces and burr measurement.