Material Removal In Machining Research Articles

A Micro-Topography Measurement and Compensation Method for the Key Component Surface Based on White-Light Interferometry.

The grinding grooves of material removal machining and the residues of a machining tool on the key component surface cause surface stress concentration. Thus, it is critical to carry out precise measurements on the key component surface to evaluate the stress concentration. Based on white-light interferometry (WLI), we studied the measurement distortion caused by the reflected light from the steep side of the grinding groove being unable to return to the optical system for imaging. A threshold value was set to eliminate the distorted measurement points, and the cubic spline algorithm was used to interpolate the eliminated points for compensation. The compensation result agrees well with the atomic force microscope (AFM) measurement result. However, for residues on the surface, a practical method was established to obtain a microscopic 3D micro-topography point cloud and a super-depth-of-field fusion image simultaneously. Afterward, the semantic segmentation network U-net was adopted to identify the residues in the super-depth-of-field fusion image and achieved a recognition accuracy of 91.06% for residual identification. Residual feature information, including height, position, and size, was obtained by integrating the information from point clouds and super-depth-of-field fusion images. This work can provide foundational data to study surface stress concentration.

Experimental study on the removal behavior of SiCf/SiC by traditional and ultrasonic vibration assist scratching with single grain diamond

Due to their excellent mechanical properties at elevated temperatures, Ceramic Matrix Composites (CMCs) are increasingly used in the manufacture of critical components for industries such as aerospace, nuclear and automotive. However, its high hardness, brittleness, anisotropy, and non-homogeneity lead to severe tool wear and uneven cutting process during material removal machining, making it difficult to control the surface quality. To gain an in-depth understanding of the material removal mechanism of CMCs for grinding processing, variable depth-of-cut scratch tests along different scratch directions under conventional and ultrasonic assist conditions were conducted. The results showed that ultrasonic assist scratch (UAS) caused more severe groove exit damage when scratching along the longitudinal direction of the fibers. The high-frequency hammering effect of ultrasonic vibration reduced the bending fracture of the fibers and increased the material removal when scratching along the transverse direction of the fibers, and reduced the area of groove edge chipping. In terms of scratching force, the scratching force along the longitudinal direction of the fibers is less than that along the transverse direction. In addition, ultrasonic vibration makes the material change from the original brittle fracture removal caused by extrusion, shear, and tension to the brittle fracture crack intersection removal prompted by hammering-scratching action, reducing the scratching force.

Numerical investigation of cutting stability and surface roughness in orthogonal milling

The vibrations produced by the chatter phenomenon are harmful for productivity in material removal machining. Some of the intolerable effects are: workpiece poor surface quality, tool wear, machine lifetime reduction. The flexibility of the cutting system favors vibrations especially when the cutting conditions are inconvenient. The flexibility is mainly linked to the cutting tool, which explains the consideration of the cutting tool as flexible in most of the analytical and numerical literature works. This work presents a numerical approach to investigate the orthogonal metal milling in order to study the chatter phenomenon effect on cutting stability and surface roughness. The proposed approach for numerical simulation uses the ABAQUS software, and includes a flexible tool on the immersion direction as well as on the feed direction. An explicit scheme and a Lagrangian formulation are retained, and the Johnson-Cook laws of behavior and damage are considered. The validation of the numerical results is conducted using experimental results.

Voxel-based modeling of transient material removal in machining

Voxel-based modeling of transient material removal in machining

Selected aspects of diagnosing material removal machining processes state

The article presents the results of works on the analysis of the possibility of using force measurements to determine the state of the machining process, both in relation to the phenomena occurring during machining and the workpiece itself compared to acoustic emission signal (AE). The research and analyzes were carried out for the commonly used material removal processes of objects; turning, milling, grinding and drilling. Various materials were processed - metal alloy Hardox 400 as well as fiber composite materials (GFRP - Glass Fiber Reinforced Polymer) and polymer construction material RenShape® BM5035 with various structures. As a result of the conducted analyzes, it was determined that the forces generated in the machine tool-holder-workpiece-tool layout can constitute a good diagnostic signal, on the basis of which it is possible to conclude about the state of the process.

Investigation of the specific cutting energy and its effect in shearing dominant precision micro cutting

Abstract The analysis of SCE (specific cutting energy) is vital for determining the machining efficiency. Conventionally, the machining forces are used to determine SCE, which is quantified as the energy that is consumed to remove unit volume of material. To correlate the micro-mechanics of material deformation and small-scale material removal in machining, in this research paper, the SCE has been modelled with consideration of shearing mechanism. While developing the model, small scale material indentation and deformation phenomena have been correlated with complex tool-work interaction behaviour in micro machining. The experiment was conducted for validation of the model for different light-weight materials i.e. Al alloy and Cu alloy. The investigation was done through the analysis of cutting forces and the visual examination of microchip morphology. It was found that the nonlinear increase and sharp fall of specific shearing energy (UShe) occur owing to the variations of the material removal mechanism. This is especially valid for lower values of UCT (undeformed chip thickness).

Studies on the grinding force, size effect, surface texture, and mechanism of material removal in the grinding of AA6061-TiB2/ZrB2 in situ composite

Machining and conversion of aluminum matrix composites into a desired shape with accuracy has been a challenge for many years. Grinding is a process aimed at achieving better-quality surface finish along with reasonable rate of material removal. The present article describes the influence of operating parameters on the tangential grinding force, size effect, and surface integrity in the grinding of in situ aluminum matrix composites using various grinding wheels. The material removal mechanism of the in situ composite under different grinding conditions is established. Experimental results show that the grinding operating parameters have significant influence on the tangential grinding force, size effect, surface integrity, and material removal. Scanning electron and atomic force microscopy findings indicate presence of numerous surface defects on the grounded surface under all grinding conditions. Diamond grinding wheel outperformed the CBN and Al2O3 wheels by requiring lower grinding force and specific grinding energy and generating lower surface defects. Surface defects, including grinding striation, delamination, and ridge formation are unavoidable under all machining conditions. However, the aforementioned surface defects indicate the ductile mode of material removal at all experimental conditions. Undeformed chip thickness under various grinding conditions plays a significant role in material removal and surface generation. These findings help to understand the mechanism of material removal in machining of in situ composites under various grinding conditions, which helps in attaining the economic production rate without compromising the surface integrity.

Prediction of critical cutting depth for ductile-brittle transition in ultrasonic vibration assisted grinding of optical glasses

The modes of material removal in machining of brittle materials consist of ductile mode and brittle mode. It is believed that there is an obvious distinction between the energy expenditures in these two modes. In this paper, the specific energies expended in ductile and brittle modes removal are modeled as a function of ultrasonic vibration parameters, grinding parameters, and work-material intrinsic properties. An approach to predict the critical cutting depth for ductile-brittle transition in ultrasonic vibration assisted grinding of glasses is proposed based on the analytical expressions for the specific cutting energies consumed in ductile and brittle modes of machining. The critical cutting depth is identified at the point where both curves of specific energies expended in ductile and brittle modes intersect. Scratching tests of BK7 and JGS1 optical glasses are conducted to verify the validity of the proposed model. Experimental results are found to correspond well with the predicted data.

The Effect of Quench-Induced Residual Stresses on the Distortion of Machined Thin-Walled Parts

In the heat treatment process, during the quenching of aluminum alloy, a high level of residual stresses is observed due to the severe thermal gradient at the surface and center of the work piece, which acts as the main source of distortion in machined parts. This article attempts to investigate the correlation between quench-induced residual stresses and the distortion of thin-walled parts during machining. The effects of polymer and uphill quenching methods in comparison with water quenching in the reduction of residual stresses are investigated on an experimental basis. By conducting the machining tests, the effects of residual stress on distortion and the effect of material removal in machining on stress redistribution are investigated. The results indicate that by adopting the polymer quenching method, the level of residual stress and distortion can be reduced significantly. According to the results, material removal in machining causes an imbalance in the compressive and tensile stresses, leading to a redistribution of the stress and distortion.

The Mechanical Properties of Sialon–Boron Nitride Composite Ceramics

The production of sialon and sialon–boron nitride composites using oxidized (up to ~15 wt.% O) Si3N4–18 wt.% AlN composite powders resulting from plasma chemical synthesis is studied. Hot pressing of these powders to nonporous state at 1620–1775°C is accompanied by the formation of composites consisting mainly of a mixture of β-sialon (z = 1.5–2) and o′-sialon. Boron nitride additions in an amount of up to 15 wt.% lead to the formation of composites that contain BN lamellar grains in the matrix of single-phase β-sialon (z = 1.5–2). The mechanical and tribological characteristics of the composites with micron and submicron grains are examined. It is observed that the dependence of scratch hardness on contact strength is almost linear for the sialon ceramics and sialon–boron nitride composites. The material is removed during machining through intensive brittle fracture. The introduction of boron nitride into sialon ceramics in an amount of more than 5% is accompanied by approximately a tenfold increase in the material removal in machining, making possible turning operations.

Characterisation of abrasive tools active surface after the impregnation process by modified ARS method based on imaging and analysis of the scattered light

Smearing of the GWAS is a serious problem in high-efficiency material removal machining processes. One of the actions that allow a reduction of this effect is the introduction of an impregnate into the structure of abrasive tools. This work presents the application of light scattering method combined with image processing and analysis techniques used for assessment of grinding wheels 1 35 × 10 × 10 SG/F46 G10VTO impregnated by non-metallic elements after the grinding of Titanium Grade 2® alloy. Assessment of the GWAS consisted of the acquisition of scattered light images and their analysis by Image Pro®-Plus 5.1 and ImageJ 1.47 software. The realised observations of the GWAS after machining showed that impregnation had considerable influence on the intensity and course of smearing of abrasive tools. The element that has the best influence on the level of smearing on the GWAS was the graphite, followed by amorphous carbon and sulphur.

The Study of Tool Wear Performance on Pocket Milling Strategy

The increasing productivity demand in machining industry has lead for fast material removal machining technique of pocket milling using different tool path strategies. This project aims to study about the effect of different tool path strategies on tool wear when machining aluminium alloy 7076. Five milling strategies were evaluated outward helical, inward helical, back and forth, offset on part one-way and offset on part zigzag. CATIA V5R19 was used to setup milling path and the machining experiments were carried out on a HAAS’ 3 axis CNC milling machine. The machining was held under wet condition with 2500 rpm cutting speed, 800 mm/min feed rate, 2 mm radial depth of cut and 2 mm axial depth of cut. The results showed that the best tool path strategies are inward helical and offset on part one-way, while the worst tool path strategy is outward helical. Failure to evacuate chip during pocket milling is the main reason to cause rapid tool wear due to temperature rise and higher contact time and area of cutting tool with the chip. Results from this experiment help to guide the machinist to perform pocket milling effectively.

Numerical Modeling of Wire Electrical Discharge Machining of Super Alloy Inconel 718

Wire Electrical Discharge machine (EDM) is a versatile method for making micro product of complex geometry. The process parameters play a critical role for the accuracy and precision of the component. Inconel 718 is a super alloy used for many critical operations. It is a challenging task for ding EDM operation of Inconel-718. It is highly essential to study the process mechanics for effective micro-EDM operation. In the present investigation, numerical simulation of wire EDM has been carried out using ANSYS software in order to determine temperature profile, Material Removal Rate (MRR) for single discharge and converted into the multi-discharge. For multi-discharge machining material removal was calculated by calculating the no. of pulse. Justification of model has been done by comparing the experimental versus numerical result obtained under the same parameter

Cutting Forces Parametric Model for the Dry High Speed Contour Milling of Aerospace Aluminium Alloys

Cutting forces is one of the most important outputs in material removal machining processes. Their values depend on a large number of parameters, such as the cutting tool material and geometry, the workpiece material or the cutting parameters, among others. In this paper, cutting forces behavior have been analyzed as a function of feedrate and cutting speed, for the high-speed peripheral milling of UNS A92024-T3 (Al-Cu) stacks. This alloy is widely used in the manufacturing process of aircraft structural elements. From this analysis, different parametric models have been adjusted to experimental data, establishing Fn=f(fz,V) relationships that allow an approximation to the values of force components for machining conditions dependent on those variables.

A predictive model of the critical undeformed chip thickness for ductile–brittle transition in nano-machining of brittle materials

There is a distinct transition in the mode of material removal in machining of brittle materials if the undeformed chip thickness is below a critical threshold of submicron scale. It is believed that at such small scale of material removal, the energy required to extend pre-existing flaws in the microstructure of brittle material exceeds the energy required to mobilize the micro-structural dislocations and hence plastic deformation serves as the dominant mode of material removal. It is postulated that a transition in the mode of material removal in machining of brittle materials is accompanied by a corresponding shift in the representative mode of energy expenditure. Hence, machining energy is a viable parameter to characterize the modes of material removal in machining of a brittle material. This paper presents a specific cutting-energy based model to predict the ductile–brittle transition point in ultra-precision machining of brittle materials. The energy expended in brittle and ductile modes of machining is modeled as a function of work-material intrinsic properties, tool geometry and process parameters. The transition point is identified in terms of undeformed chip thickness at which the mode of energy undergoes a transition from the plastic deformation based one to the fracture based one. The validity of the proposed model is verified by single-edge cutting tests on single-crystal silicon and BK7 glass. The experimental results are found in good agreement with model results.

Meshfree isoparametric point interpolation method (IPIM) for evaporative laser drilling

An isoparametric point interpolation method (IPIM) has been developed to analyze evaporative laser machining. The method is based on isoparametric representation of the unknown in the local domain. It also uses a simple strong form, but shows to be powerful enough to handle highly localized boundary conditions. Solution in a typical influence domain is approximated by a polynomial function. The problem is geometrically nonlinear because the domain is not known a priori due to material removal in machining. An iterative scheme is introduced to solve the nonlinear problem. The material removal is handled by redistributing points in the domain. This renders the point distribution non-uniform same as random distribution. Three different boundary conditions considered are of essential, convection, and laser irradiation type. The numerical results show very good agreement with those by FEM and BEM.

An experimental approach to study the capability of end-milling for microcutting of glass

Glass is a hard and brittle material. It is finding mounting quantum of applications in semiconductor, opto-electronics, and mold manufacturing sectors. However, glass is not amenable to machining because of its low fracture toughness. If machined with conventional approach, the mechanism of material removal in machining of glass is fracture based that results into poor quality of the machined surface and imparts subsurface damage. In order to achieve superior surface finish, glass must be machined in ductile mode. Ductile-mode machining is now a well-established technique but most of the work has been performed with single-point cutting processes. To assess the capability of ductile-mode machining with multipoint cutting process, fundamental studies are highly desired. This paper reports the results of an experimental investigation into ductile-mode machining of glass by milling process. Side-milling tests have been performed on the glass workpiece to identify the key parameters governing the ductile-brittle transition mechanism. Experimental results demonstrate that fracture-free surface can be machined on glass by milling process. Cutting forces were analyzed to comprehend the dynamic behavior of the cutting process in ductile mode.

Engineering of surface layer in material removal machining

Methodology developed for designing and investigation of the characteristics of technological and exploitation surface layer aiming to provide conditions under which a surface layer with predictable characteristics of mate surfaces will be generated is described in the paper. Methodology possesses syntheses of performances for creation and analysis of models for surfaces generated with different types of machining, and import of measured surfaces data. Basis for the surface layer modelling with deterministic and stochastic structure is method of kinematical–geometrical copying of the cutting tool geometry as a function of machining conditions and method of virtual modelling comprising synthesis of theoretical functions simulating also disturbing factors appearing in the process of material removal. Definition of correlation existing between the parameters describing surface geometrical structure and technological parameters for surface machining is also enabled. These activities are performing with support of the originally created software (CADSIM) designed in Visual Basic in interaction with MS Access, AutoCAD and MATLAB.

Improving High-Speed Machining Material Removal Rates by Rapid Dynamic Analysis

Stability prediction and chatter avoidance in high-speed machining requires knowledge of the tool point dynamics. In this paper, three advances toward the rapid identification of the tool point frequency response and corresponding stable cutting parameters are described: 1) stable speeds determination using non-contact periodic impulsive excitation of the tool point (produced by spindle rotation and a stationary magnet) in conjunction with once-per-revolution sampling, 2) Receptance Coupling Substructure Analysis for the analytic prediction of the tool point response, and 3) once-per-revolution sampling of the audio signal during cutting to determine stability behavior.