Material Removal Process Research Articles

Study on modelling simulation and distribution characteristics of residual stress during robotic weld end grinding of high strength modulated steel

Welding technology is widely used in the aerospace, construction, machinery, and rail transportation industries. After the welding process is completed, the weld seam is typically ground to improve the assembly accuracy and surface integrity of the structural part. However, residual stresses on the surface after grinding often affect the product performance and service life of structural components. Therefore, the formation mechanism and distribution of residual stresses after the robotic weld end grinding of high–strength modulated steel welds were investigated. First, a local contact geometric model of the grinding wheel and weld was established, and a grinding -force contact model was built based on this model. Next, a model of the heat-flow distribution in robotic end grinding was analysed, and the magnitudes of the heat flow in the contact and weld-width directions were calculated for the contact area. The results of these calculations were similar to the actual heat-flow distribution. Then, based on a theoretical analysis, the finite element method was used with a birth–death element to establish a force-thermal coupled residual stress prediction model, which could simulate the material removal process during actual grinding. Finally, the accuracies and reliabilities of the theoretical and simulation models were experimentally verified. The maximum error between the maximum simulated temperature and experimentally measured value was 10 %. The minimum error was 3 % when using the same process parameters, and the residual stress error was approximately 15 %. Based on the simulations, the variations in the temperature and residual stresses with time and position were explored. The highest weld-contact surface temperature of 417.75 °C was found when grinding using process parameters ap = 0.2 mm, vs = 23.55 m/s, vw = 20 mm/s. The residual tensile stresses could be up to +553 MPa in the longitudinal direction and −161 MPa in the transverse direction. The temperature in the zone of demarcation between the weld and base material was 212.8 °C, with maximum residual tensile stresses in both the longitudinal and transverse directions, of up to 352 MPa. The analysis revealed that the magnitude of the residual stresses was consistent with the temperature variation pattern, and that the grinding depth had the greatest influence on the residual stress distribution.

Numerical simulation of abrasive cutoff operation based on ALE adaptive meshing technique

Metal cutting is one of the most important and commonly used manufacturing processes in industry and has been studied for years; however, accurate simulation of cutoff operation is still a big challenge because of the complexity of the material removal process. The main challenge for the classical simulation method is computational difficulties during the material removal process, and furthermore, the material deletion criterion has to be somehow empirical. To conquer these problems, a more robust and efficient simulation technique for the cutoff process is proposed herein, in which the material removal is achieved through continuously adjusting mesh nodes on contact surfaces based on ALE adaptive meshing technique, instead of deleting elements. Finally, this new simulation technique is used to predict the heat partition and temperature field evolution during the cutoff operation of the steel plate. It is found that the obtained simulation results agree well with those by the analytical approach, demonstrating its effectiveness.

Influence of surface roughness and thermal characteristics in turning operation using nanofluid lubrication

The turning operation is commonly used as a major material removal process in the manufacturing industry. The rate of heat generation during machining operation causes deprivation in the surface finish of the workpiece, reduction in tool life, localized melting of burr, which results in built-up edge (BUE), and therefore causes high cutting force, etc. Any manufacturing technique requires adequate lubrication to attain the optimum tool tip temperature. The nanofluid can be used as a lubrication fluid for controlling the temperature. In the present study, the experimental data for temperature and surface roughness is obtained at different workpiece rotation speeds at the same depth of cut and the same feed of the turning operation. It is observed that at temperature reduces by 25 % to 33 % compared with the dry run at the tool tip and workpiece at spindle speeds equal to 250 RPM, 420, and 710 RPM using the mixing of cutting oil + water + different proportions of Al2O3 nanoparticles. It is also observed that the surface finish is also improved by 11.26 % to 17.26 % at different spindle speeds with the use of nanofluid as a lubricating fluid.

Phase transformation and incidental effects of metastable crystalline TiAlN on the material removal mechanism

Spinodal decomposition of Ti1−xAlxN crystal structure significantly impacts their physical properties, particularly at the atomic scale. In this study, we employed systematic three-dimensional molecular dynamics simulations to understand the process of material removal in TiAlN. Orthogonal simulations were conducted with cutting depth and Al content as variables to analyze their impact on the phase transformation mechanism and the resulting surface finish. The simulations reveal that the aluminum content and depth of cut significantly influence the phase transformation process of supersaturated TiAlN crystals through spinodal decomposition. It is observed that the aluminum content has a maximum stable solubility of approximately 0.6 in TiAlN crystals, above which the system undergoes significant spinodal decomposition during cutting to produce hexagonal phases with lower hardness. Increasing the aluminum content leads to wider phase change and deeper sub-surface damage in the system. On the other hand, the cutting depth will promote phase transformation by affecting the stress distribution, thereby increasing the root mean square roughness of the height profile.

Machining mechanism of polycrystalline nickel-based alloy under ultrasonic elliptical vibration-assisted cutting

This work investigates the machining mechanism and deformation behavior of NiFeCo under conventional nanoscale cutting and ultrasonic elliptical vibration-assisted cutting (UEVC) through molecular dynamics simulation. The material removal process is considered in various vibration frequencies, amplitude ratios, and phase angles. In both cases, the highest shear strain, local stress, and temperature atoms are primarily located in the cutting area and chip volume, but the magnitudes are more significant under UEVC. The distribution analysis results of stacking fault and dislocation also show that grain boundaries strongly influence the deformation behavior and the local stress in the material. Moreover, in the cases of UEVC, the rise of vibration frequency and the decrease in amplitude ratio positively impact improving the material removal rate and reducing the average cutting force. Meanwhile, the change in phase angles affects only the timing of the peak in force value and has no significant effect on the resultant force and the cutting efficiency.

Evolution of the Interelectrode Gap during Co-Rotating Electrochemical Machining

A new co-rotating electrochemical machining method is presented to machine the complex structure inside annular parts such as flame tubes and aero-engine casings. Due to the unique shape and motion of electrodes, it is difficult to accurately compute the electric field intensity in the machining area. In this paper, the complex electric field model is simplified by conformal transformation, and the analytical solution of electric field intensity is exactly calculated. A material removal model is built on the basis of the electric field model, and the dynamic simulation of the material removal process is realized. The effects of the cathode radius, applied voltage, feed rate and initial interelectrode gap on the interelectrode gap (IEG) and material removal rate (MRR) are analyzed. The simulation results indicate that the MRR is always slightly less than the feed rate in a quasi-equilibrium state, resulting in a slow reduction in IEG. In addition, the final machining state is not affected by the initial IEG, and the MRR in a quasi-equilibrium state is determined by the feed rate. Several comparative experiments were carried out using the optimized processing parameters, in which the MRR and IEG were measured. The convex structures were successfully machined inside the annular workpiece with optimum machining parameters. The experimental results are in good agreement with the theoretical results, indicating that the established model can effectively predict the evolution process of MRR and IEG.

Erosion Investigation of Dimple Wall using Erosion-Coupled Dynamic Mesh.

The erosion of the dimple walls is investigated experimentally and numerically. A mathematical simulation framework was proposed to describe quantitatively the morphological evolution of the dimple wall quantitatively. As the wall shape continues to evolve, the wall shear stress, mesh deformation, and erosion rate would decrease and gradually tend to be constant. Two distinct regions have been identified along the dimple's windward wall surface: the wall's central area and the lateral area. In the central region, the wall profile flare occurs mainly in the early stage. In the lateral region, profile flare occurs mainly in the later stages of erosion. The microhardness of the wall surface shows a positive correlation with the erosion rate. The liquid-solid two-phase impinges on the wall at a smaller angle, and the wall material removal process is mainly based on the microcutting and slip mechanism. The results provide theoretical implications for the design of dimple-shaped, wide-channel welded plate heat exchangers.

Investigation on tearing damage of CFRP circular cell honeycomb in end-face grinding

CFRP circular cell honeycomb has promising applications in the aerospace field due to its excellent mechanical properties. However, a large number of periodically distributed tearing damages severely restrict the high-quality machining of CFRP circular cell honeycomb. This paper investigates the formation mechanism of tearing damages during end-face grinding of CFRP circular cell honeycomb and proposes suppression strategies. In this paper, a maximum undeformed chip thickness model considering tearing damage distribution is developed, and the evolution behavior of tearing damage is studied by combining the material removal process and grinding force. The grinding force and maximum tearing damage depth in different grinding conditions are analyzed. The results show that the formation of tearing damage in the cut-in stage is related to the weak stiffness of thin walls and the radial grinding force. The radial grinding force and maximum tearing depth can be altered by changing the maximum undeformed chip thickness which can be adjusted for different grinding speeds, feed rates, and offset ratios. The low-damage machining of CFRP circular cell honeycomb can be achieved by using a large offset ratio and variable feed rate.

Modelling of kerf width and surface roughness using vibration signals in laser beam machining of stainless steel using design of experiments

Manufacturing industries are increasingly interested in laser beam machining as an efficient material removal process. Accordingly, there is great motivation in the modelling of the machining process to understand the physics behind the machining process in order to improve the machining efficiency. The present study made an attempt to predict surface roughness, kerf width and metal removal rate by utilizing the vibration signals measured during the laser beam machining of AISI 304 stainless steel. As per Taguchi’s L9 design of experiments, nine experiments were conducted at three levels of laser power (2.0, 1.5 and 1.0 kW), laser frequency (10, 8 and 6 kHz), cutting speed (3.0, 2.5 and 2.0 m/min) and nozzle tip distance (1.2, 1 and 0.8 mm) on 6 mm thickness of sheet metal and the vibration of sheet metal was measured using an accelerometer. It was observed that, the sheet vibration along the cutting direction increased the metal removal rate and sheet vibration perpendicular to the cutting direction caused surface roughness. Mathematical models were developed with the vibration data and predicted the surface roughness, kerf width and metal removal rate. The root mean square error of the responses was calculated as 0.615 µm, 5.44 µm and 0.259 m3/min for surface roughness, kerf width and metal removal rate respectively, demonstrating a significant correlation with experimental results. Furthermore, effect of laser power, laser frequency, cutting speed and nozzle tip distance on the surface roughness, kerf width, heat affected zone and metal removal rate was studied. The laser power and cutting speed have significant effect on these responses. Finite element modelling based simulation was carried out and studied effect of molten metal temperature on the heat affected zone. Temperature in the molten pool reached to maximum of 1773 K and the heat affected zone increased, when the laser power increased to 2.0 kW. The root mean square error between the measured and simulated heat affected zone was computed as 4.68 µm, indicating a good correlation between both.

Slurry pressure at the cutting zone in multi-wire sawing: An experimental study

Multi-wire sawing has been widely used in the processing of semiconductor material wafers employed in integrated circuits, solar cells, etc. Recently, free abrasive multi-wire sawing has been gradually replaced by solid abrasive multi-wire sawing technology in the domain of solar wafers. However, free abrasive sawing still plays an important role in the processing of electronic-grade monocrystalline silicon wafers, where the requirements on the wafer quality are continuously increasing. Because the free abrasive multi-wire sawing process is very complex, its material removal mechanisms are not fully understood. In this study, experiments were designed to measure the slurry pressure at the cutting zone during a free abrasive multi-wire sawing process to fabricate monocrystalline silicon wafers, and the pressure distribution condition throughout the cutting zone was obtained. Two sets of micropores of 0.17 mm diameter were processed on the experimental workpiece to transmit the cutting zone fluid pressure to the sensor. Each group of micropores consisted of 17 small pores, divided into three rows, with the row spacing consistent with the pitch width of the wire guide. During installation, the center line of each row of micropores was aligned with the center line of the steel wire. The pressure at the cutting zone was measured using the micropores to transfer the slurry pressure to the sensor. Calibration experiments were conducted by considering the capillary effects of the micropores, and the actual pressure at the cutting zone was obtained. Experimental results show that the slurry pressure was 0.16 bar at 40 mm near the slurry inlet. As the distance from the slurry inlet increased, the pressure fluctuated around 0.14 bar. Furthermore, at a distance of 160 mm from the slurry inlet, the sensor was not able to detect the pressure at the cutting zone. The experimental results from the free abrasive multi-wire sawing pressure measurement showed that material removal involves a three-body action comprising the metal wire, abrasive grains, and workpiece. At the cutting zone far from the location of the slurry inlet, forming a stable and continuous film with the slurry is difficult. The experimental results confirm that the force of material removal during the sawing process mainly comes from the wire tension of the steel wire. The film thickness of the slurry in the cutting zone is determined by the diameter of the abrasive between the wire and ingot. The experimental conclusion is of great significance for understanding the complex material removal process in the cutting zone for multi-wire sawing.

Machinability Characterization of 3D Printed PEEK

The 3D printing technology is being applied more and more every day, this is a consequence of its applicability and low waste generation, becoming one of the best options to obtain good quality pieces. Sometimes, post machining processes are necessary to fulfil tight tolerances or achieve complex geometries by means of the connection between different pieces printed using this technology. The field of knowledge and studies focused on 3D printing is in constant evolution. There are plenty of materials that can be used to apply 3D printing technology. Among them, PEEK is one of the best options when good mechanical properties are required. Being applied in aeronautic or automobile industry, is also used in biomedical applications, such as prosthesis or mechanical components among others. Within the machining processes, milling, turning, and drilling are the most widespread. Orthogonal cutting is a machining process in which the cutting edge of the tool is perpendicular to the cutting speed, and it is commonly used when a simple and pure study of the mechanism behind a material removal process is required. In this study, tests that analyze the orthogonal cutting on 3D printed PEEK samples using different orientations (0o and ±45o) have been conducted. The influence of cutting speed (30, 60 and 90 m/min) and depth of cut (50, 100 and 150 μm) is studied through the analysis of cutting forces and surface finish quality. As a general approximation, it can be seen that the fiber orientation affects significantly to the forces monitored but unexpectedly, lightly to the surface finish.

Hyperspectral Photoluminescence Imaging for Spatially Resolved Determination of Electrical Parameters of Laser‐Patterned Perovskite Solar Cells

Absolute calibrated hyperspectral photoluminescence (PL) imaging is utilized to access, in a simple and fast way, the spatial distribution of relevant solar cell parameters such as quasi‐Fermi level splitting, optical diode factor, Urbach energies E u, and shunt resistances R sh, without the need for electrical measurements. Since these metrics play a significant role in evaluating the process windows for electrical series interconnection by laser patterning, this approach is followed to systematically locate and quantify electrical losses that may occur as a result of the laser‐patterning process for monolithic series interconnection. It is shown that both picosecond and nanosecond laser pulses can be used for successful series interconnection. In both cases, only minor lateral material alterations occur, localized in a few μm wide region adjacent to the edges of the scribe lines. Furthermore, the acquisition and analysis of these hyperspectral PL datasets provide insights in the material removal process, from which it is concluded that the perovskite is rather resilient against the thermal impact of the laser.

Comparative Study on Micro-Grinding Performance of 2.5D Cf/SiCs, 2.5D SiCf/SiCs, and SiC Ceramics.

To investigate the micro-grinding process and performance of 2.5D Cf/SiC composites and 2.5D SiCf/SiC composites in depth, single-factor micro-grinding experiments were conducted by using SiC ceramics as a comparison. Differences in the material removal process, surface microstructure, surface roughness, and grinding force of the three materials under the same grinding parameters were comparatively analyzed. The results indicate that crack propagation is severe during the micro-grinding process of SiC ceramics. The ground surface is uneven, accompanied by pit defects and large surface roughness Ra. However, the presence of reinforcing fibers and interfaces in the two types of composites can inhibit crack propagation or change their extension directions. Therefore, their surfaces are smooth and flat after grinding, with small defects and low surface roughness Ra. In addition, the grinding processes of the two composites are both related to fiber orientation. There are differences in crack propagation paths and fiber fracture positions in the weft fiber layer and the radial fiber layer, which result in different forms of grinding defects. During micro-grinding, the real-time force signals of 2.5D Cf/SiC composites and 2.5D SiCf/SiC composites are relatively stable, while the signals of SiC ceramics have a large number of spikes. The average micro-grinding force of the three materials is: SiC ceramics > 2.5D SiCf/SiC composites > 2.5D Cf/SiC composites.

Mechanism in scratching of calcium fluoride with magneto-plasticity

Magnetic field-tuned dislocation plasticity (i.e., magneto-plasticity) has attracted growing attention for assistance to limit the damage evolution of brittle ceramics in the material removal process. However, the mechanism controlling material removal of brittle ceramics with magneto-plasticity remains far from clear. Therefore, combined stress field modeling and molecular dynamics (MD) simulations were performed for scratching of a ceramic material, calcium fluoride (CaF2), to investigate the magneto-plasticity mechanism during the material removal process of brittle ceramics. The stress field calculation with magneto-plasticity was first conducted, which suggests a general reduction in scratching stress on the subsurface under the magnetic field effect. It is also found that the degree of reduction in scratching stress is significantly influenced by the magnetic field intensity and direction as well as strain rate. The reduced scratching stress is responsible for the suppressed formation and evolution of cracks and defects in scratching. Subsequently, MD simulations in scratching of CaF2 show that the application of a magnetic field can facilitate dislocation nucleation, enlarge the range of dislocation propagation, and regularize the dislocation distribution, indicating the advancement in elastic-plastic transition and dislocation mobility. From the views of energy criterion and crystal plasticity, a magnetic field can decrease the required work and resolved shear stress for dislocation slip, which results in a lower scratching stress level. The combined theoretical method of this study broadens the comprehension of magneto-plasticity on deformation mechanism in the material removal process of ceramics and offers theoretical direction for the application of magnetic field assistance in ceramic processing.

Electro-mechanical-thermal energy coupling characteristics analysis and EFMM-based energy modelling for machine tools considering dynamic thermal environment

Machine tool is an isolated thermodynamic and inefficient energy-consuming system, whose energy consumption is increasingly influenced by its internal thermal environment. While the thermal environment changes dynamically due to the complex electro-mechanical-thermal (EMT) energy conversion characteristics. Therefore, it is urgent to expound the multi-energy coupling mechanism to establish an accurate energy model for machine tool. However, the existing studies merely emphasize the electro-mechanical conversion that related to the material-removal (MR) process and fail to reveal the dynamic characteristics of energy caused by EMT, which results in inaccurate energy models. In light of this, the energy flow matrix modelling (EFMM) method, which can model the multi-energy flows automatically and accurately, is introduced to construct a generic energy balance matrix equation for machine tool, where the coupling relationship between electrical, mechanical and thermal energy are taken into consideration. Subsequently, the dynamic mechanical and thermal energy are analyzed, respectively. Based on this, the total energy consumption and cutting energy efficiency models for machine tool in a dynamic thermal environment are established. The reliability and accuracy of the constructed models are demonstrated by the case study and comparative analysis. The results indicate that the average relative errors of the proposed energy models are mostly within 5 %. The presented approach is conducive to understanding the multi-energy coupling characteristics and providing a feasible way for energy-efficient machine tools.

Numerical modeling to predict threshold fluence for material ejection in Laser-Induced forward transfer of metals

Laser-induced forward transfer (LIFT) uses a pulsed laser beam to propel material from a donor (containing a glass coated with a thin material film) onto a receiving substrate, resulting in pixellated material deposition. The deposition characteristics depend on the material ejection modes that vary with film thickness and laser parameters. This study develops a computational model based on the finite volume method for LIFT of gold films using nanosecond pulses, which captures two different ejection modes for droplet depositioncap ejection and jet ejection. The model computes the temperature distribution and predicts potential ejection regimes for different film thicknesses, providing an understanding of the material removal process. Cap ejection occurs at lower laser fluences when the entire film thickness in the irradiated zone is in the molten phase. In comparison, jet ejection occurs at higher laser fluences caused by vapor pocket formation at the glass-film interface. The model predicts threshold fluences with greater than 90% accuracy for film thickness less than 583 nm. However, for the film thickness of more than 583 nm, the simulations underpredict the threshold fluence, suggesting that laser absorption by the film decreases due to vapor formation at the glass-film interface. Besides, it is observed that higher fluences can cause melting and vaporization of the glass at the interface leading to possible contamination of the deposited material. The proposed model can be used to choose the operating window for laser parameters for droplet deposition in LIFT, which otherwise is challenging using experiments.

Polishing of metal 3D printed parts with complex geometry: Visualizing the influence on geometrical features using centrifugal disk finishing.

Parts produced with metal additive manufacturing often suffer from a poor surface finish. Surface finishing techniques are effective to improve the quality of 3D printed surfaces, however they have as downsides that they also slightly change the geometry of the part, in an unpredictable way. This effect on the geometrical features of complex parts has received little attention. In this research, we illustrate a method to visualize the impact of surface finishing techniques on geometrical features, as well as their effectiveness on parts with high shape-complexity, by using centrifugal disk finishing as a case study. We designed and 3D printed test parts with different features using selective laser melting, which were coated with a blue metal lacquer prior to polishing. After polishing, the blue lacquer was eroded away from the spots that were easily reached by the polishing process, yet had remained on the surfaces that could not be reached by the process. We used measurements of material removal and image processing of the remaining blue lacquer on the surfaces to analyze these effects. Using this method, we were able to derive a number of specific design guidelines that can be incorporated while designing metal AM parts for centrifugal disk finishing. We suggest that this visualization method can be applied to different polishing methods to gain insight into their influence, as well as being used as an aid in the design process.

Modeling of Specific Energy in the Gear Honing Process

Gear honing is a cost-efficient method for the finishing of hardened gears in which material removal is realized through honing wheel and workpiece gear interactions. There are a number of indicators used for evaluating the degrees of these interactions, among which specific energy is a more appropriate one than the others since it is capable of quantifying the amount of energy consumption during the material removal process. Nevertheless, models for the prediction of specific energy in gear honing have not been thoroughly investigated. This work presents a theoretical model of specific energy to quantitatively evaluate the material removal efficiency in the external gear honing process. To develop the model, an analytical material removal rate and a honing force model are proposed, and the feasibility of the proposed model is validated against external gear honing experiments. The correlations of specific energy with processing parameters are investigated and the material removal efficiency scores of external gear honing and grinding are compared and discussed. The present approach enables an in-depth understanding of the abrasive–material interactions in the gear honing process and the effects of processing parameters on material removal efficiency.

LASER MACHINING OF BASALT GLASS HYBRID COMPOSITE USING DEMATEL METHOD

Hybrid composites are materials made of two or more different types of fibers incorporated into a single polymer matrix the year 2019 publication failure analysis in bio composites, fiber-reinforced composites, and hybrid composites. A hybrid composition of basalt and glass layer fabricated and its various mechanical properties after being tested. Glass-fiber composite is a magnificence of fiber-reinforced polymer composites. Hybrid compounds are common ones two or more in the matrix combining different types of fiber products manufactured by various hybrid gave researchers compounds have many definitions. A laser machine is a target material that interacts with a laser beam it is a material removal process done by such a device that uses photon energy processing to the target object thermal or photochemical energy is carried in the form of removing the items directly and by melting evaporation elimination. Commercial, industrial, aeronautical, maritime, and recreational constructions can utilize hybrid composites for their main structural components. It offers a wide range of advantages in the aerospace sector, including strong impact resistance, outstanding fatigue and corrosion resistance, and both. A hybrid composite made of layers of basalt and glass has been created, and after that, its varied mechanical characteristics have been examined. It takes time to precisely machine these composite materials. The mechanical performance of the hybrid composite is decreased by a number of constraints in traditional machining, including fiber pullout, delamination, burr formation, matrix crack development, etc. These issues might result in a poorly machined surface. The decision-making trial and evaluation laboratory (DEMATEL) is regarded as an efficient technique for locating the causal links in a complex system. It focuses on assessing the interdependencies between elements and identifying the crucial ones using a visual structural model. Lamp current (amp), Pulse frequency (Hz), Cutting speed (mm/min), Pulse width (ms), Air pressure (bars). From the result, it is seen that Lamp current got the first rank whereas the Pulse width is having the lowest rank.

Investigation on tribo-characteristics of electrochemical jet machined part manufactured by laser powder bed fusion

Electrochemical jet machining (ECJM) is a toolless electrochemical-based material removal process suitable for finishing the Laser powder bed fusion (L-PBF) manufactured parts. However, the investigation of the tribological characteristics of the finished part is unknown. Therefore, in this article, an investigation was made to evaluate the tribological characteristics of the electrochemical jet machined surface of SS316L part produced by L-PBF. The experimental results revealed improvement in the roughness parameters after the ECJM. The wear tests revealed that the friction coefficients (COF) of the finished samples were significantly lower in comparison to the as-manufactured samples. During the investigation, the dominating mechanisms of the wear were found to be adhesive and delamination wear.