Erosion damage of polymeric material by slurry

An attempt was made to reveal the erosion mechanism of a plastic material in slurry containing glass beads of approximately 176 μm in diameter. The experimental observations were interpreted in terms of parameters such as the impact velocity V_p, the impact angle α of the beads and the striking efficiency η. A theoretical flow analysis for a solid-liquid two-phase flow was made and it was found that the trajectories of the particles curved as they approached the specimen, indicating that the actual surface onto which the particles were impinging was much narrower than that which would be expected for sand erosion in an air stream. In the slurry erosion the impact velocity and impact angle differed greatly at different positions of the specimen. This is possibly due to the differences in the density and viscosity of liquid and air. Two distinctly different types of erosion were observed: a typical brittle behaviour occurred near a stagnant point, after an initial incubation period, whereas at a distance from the stagnant point only a slight surface roughness was produced. These two different types of erosion produced a clear boundary. Erosion rates depended on the positions of the specimen and were found to be proportional to (V_p sin α)^2.6. This suggested that the normal component of the impact velocity of the particle determined the erosion rate of the plastic material due to slurry.     

Studying local liquid velocity in liquid–solid packed bed using the newly developed X-ray DIR technique

Combination of X-ray Digital Industrial Radiography (DIR) and Particle Tracking Velocimetry (PTV) techniques for local liquid velocity measurement (V_LL) has been newly developed and successfully applied for trickle bed reactor (TBR). The technique was validated against newly developed fiber optical probe technique. This work attempts to highlight the applicability of this newly developed technique on a liquid–solid packed bed reactor. In this work, liquid was represented by water and solids were represented by EPS beads. The EPS beads were chosen because of its low density property. Three superficial liquid velocities (V_SL) were applied to the system. The experiment was replicated four times. The digital industrial radiography (DIR) consists of a complementary metal oxide semiconductor (CMOS) digital detector and X-ray source. Results of this work suggest that the technique has been successfully applied and comparable with previous work that has been done in the literature. It also suggests that there will be a maximum measurable interstitial liquid velocity when it travel inside the packed bed. The measured V_LL can have a maximum range that is between 4 and 4.7 times that of its V_SL. For V_SL=0.42±±2%, the V_LL-Max is in between 1.7 cm/s and 1.9 cm/s, V_SL=0.84±±2%, the V_LL-Max is in between 3.6 cm/s and 4.0 cm/s, and for V_SL=1.11±±2%, the V_LL-Max is in between 4.3 cm/s and 4.8 cm/s.     

Calculation of negative-pressure chip in suction-type internal chip removal system and analysis of influencing factors

Compacted graphite iron (CGI) is considered as the ideal material to make modern fuel-efficient diesel engine. Due to the vermicular or worm-like graphite distributed among the ferrite/pearlite matrix, CGI behaves better physical and mechanical properties in comparison with gray cast iron (GCI) and spherical graphite spheroidal cast iron (SGI). However, these good properties bring about the machining challenges. So it is important to appropriately select cutting parameters to machine this material with economy and efficiency. The present study investigated the influence of cutting parameters, such as cutting speed V, feed rate f, and exit angle Ψ, on workpiece material removal volume Q and cutting burr height on the entrance side H₁ and on the exit side H₂ during high-speed milling of CGI by the coated carbide tools_. On this basis, the relatively optimum high-speed cutting parameters were selected under the research condition. Cutting tool failure mechanism was also investigated with the aid of scanning electronic microscope (SEM) and energy-dispersive system (EDS) (SUPRA55, Germany) analysis. The results showed that Q, H₁, H₂, and the type of cutting burr on the exit side of the machined surface could be influenced by the cutting parameters. And the relatively optimum cutting parameters are V = 800 m/min, f = 0.25 mm/rev, and Ψ = 60°. Adhesive wear and thermal cracks which were perpendicular to the cutting edge were common wear mechanisms during the cutting process. However, with an increase in feed rate, mechanical cracks which were parallel to the cutting edge could be found on the flank face of the cutting tool.     

A comparative evaluation of the turning of reinforced and unreinforced polyamide

This work presents an experimental study on the cutting process for polyamides PA 6 and PA 66-GF30 (reinforced with 30% glass fiber). The experiments were carried out on extruded workpieces using cemented carbide (K15) tools in turning. The objective of this study is to evaluate the influence of the glass fiber reinforcement on the chip compression ratio R _c, chip deformation å, friction angle ρ, shear angle Φ, normal stress σ, and shear stress τ under prefixed cutting parameters (cutting velocity and feed rate). The experimental physical model was compared with the Merchant equation.     

Optimization of surface roughness in end milling Castamide

Castamide is vulnerable to humidity up to 7%; therefore, it is important to know the effect of processing parameters on Castamide with and without humidity during machining. In this study, obtained quality of surface roughness of Castamide block samples prepared in wet and dry conditions, which is processed by using the same cutting parameters, were compared. Moreover, an artificial neural network (ANN) modeling technique was developed with the results obtained from the experiments. For the training of ANN model, material type, cutting speed, cutting rate, and depth of cutting parameters were used. In this way, average surface roughness values could be estimated without performing actual application for those values. Various experimental results for different material types with cutting parameters were evaluated by different ANN training algorithms. So, it aims to define the average surface roughness with minimum error by using the best reliable ANN training algorithm. Parameters as cutting speed (V _c), feed rate (f), diameter of cutting equipment, and depth of cut (a _p) have been used as the input layers; average surface roughness has been also used as output layer. For testing data, root mean squared error, the fraction of variance (R ²), and mean absolute percentage error were found to be 0.0681%, 0.9999%, and 0.1563%, respectively. With these results, we believe that the ANN can be used for prediction of average surface roughness.     

Chip formation analysis in micromilling operation

In mechanical micromachining, understanding the chip formation mechanism is critical to optimize the machining parameters and improve the workpiece performance. In this work, the entire slot micromilling process on Al6061-T6 by one flute carbide cutter was simulated by means of finite element method (FEM). Under this machining parameters set, the chip was found to be segmented type. The simulation results matched with the experimental results on the burr and chip morphologies and the cutting force. The segmented chip formation process was described from the viewpoint of chip velocity. The variations of the tool chip contact length (l _T ) and the shear band length (l _S ) were studied in detail. The chip formation mechanism was studied quantitatively by means of hybrid analytical-FEM approach. Through calculating the chip moments, “tool rake moment” M _Tool and “shear band moment” M _Work, it has been found that the main reasons of the segmented chip formation are the variations of the l _T and l _S . The Arcona–Dow model (AD model) and Merchant model (MM model) were utilized to calculate the M _Work respectively. The AD model performed better in the microscale than the MM model. In the segment generation occasion, the average chip velocity value in chip bending process was much greater than the one before chip bending, which was about the cutting speed. The chip root velocity was almost constant in the entire micromilling process, and the chip tip velocity increased greatly in the chip bending instant due to the chip angular acceleration. The chip angular acceleration was acquired, respectively, from FEM and the analytical method based on the M _Tool and M _{Work_AD} calculations. The agreement of these two approaches validated the correctness of the chip moments calculations. The results of this work were useful to understand the micromilling mechanism and improve the workpiece performances.     

Optimization of pulsed GTA welding process parameters for the welding of AISI 304L stainless steel sheets

Optimization of pulsed gas tungsten arc welding (pulsed GTAW) process parameters was carried out to obtain optimum weld bead geometry with full penetration in welding of stainless steel (304L) sheets of 3 mm thickness. Autogenuous welding with square butt joint was employed. Design of experiments based on central composite rotatable design was employed for the development of a mathematical model correlating the important controllable pulsed GTAW process parameters like pulse current (I _p), pulse current duration (T _p), and welding speed (S) with weld bead parameters such as penetration, bead width (W), aspect ratio (AR), and weld bead area of the weld. The developed models were checked for adequacy based on ANOVA analysis and accuracy of prediction by conducting a confirmation test. Weld bead parameters predicted by the models were found to confirm observed values with high accuracy. Using these models, the main and interaction effects of pulsed GTAW process parameters on weld bead parameters were studied and discussed. Optimization of pulsed GTAW process parameters was carried out to obtain optimum bead geometry using the developed models. A quasi-Newton numerical optimization technique was used to solve the optimization problem and the results of the optimization are presented.     

Effects of entraining velocity of lubricant and sliding velocity on friction behavior in stainless steel sheet rolling

A series of experiments was carried out using a rolling-type tribometer to investigate the effects on friction behavior of the entraining velocity of the lubricant at the inlet to the contact zone (V) and sliding velocity during deformation (ΔV). Experiments with stainless steel sheets of two different surface roughnesses showed that the variations in the friction coefficient with entraining velocity V and sliding velocity ΔV are largely dependent on the initial surface texture of the workpiece. For a smooth workpiece, the friction coefficient decreases with increasing sliding velocity ΔV but keeps almost constant with increasing entraining velocity V. However, for a rough workpiece, the friction coefficient initially decreases slowly and increases largely with increasing sliding velocity ΔV or decreasing entraining velocity V. Observation of the rolled surface for a smooth workpiece shows that, with increasing entraining velocity V, the slip band becomes more marked, and with increasing sliding velocity ΔV, the rubbed portions become more conspicuous. For a rough workpiece, galling occurs at high sliding velocity ΔV. The critical condition for galling outbreak is shown on the V-ΔV graph. The galling outbreak process is observed by interrupting the rolling process.     

Application of Taguchi-based gray relational analysis for evaluating the optimal laser cladding parameters for AISI1040 steel plane surface

The effect of various laser cladding process parameters like laser power, scan speed, and powder feed rate on clad bead quality characteristics (or clad bead geometry) for AISI 1040 steel substrate have been studied by performing a number of experiments with L ₉ orthogonal array. In order to find the process parametric setting for best quality clad bead based on experimental results, a multiresponse optimization technique using gray relational analysis (GRA) is presented in this paper. The GRA is applied on laser cladding process to find out the gray relational grade for each experiment. On optimization, power of 1.25 kW, scan speed of 0.8 m/min, and a powder feed rate of 11 gm/min have been found to be the best parametric setting for laser cladding operation of AISI 1040 steel substrate. Moreover, the analysis of variance is also performed to determine the contribution of each control factor on the clad quality characteristics. Finally, to ensure the robustness of GRA, a confirmatory test is performed at selected optimal parametric setting.     

锯切花岗石过程中金刚石串珠的磨损特性

通过跟踪烧结式金刚石绳锯切割花岗石过程中串珠直径磨损及串珠表面金刚石磨粒的磨损,研究串珠的磨损规律,并建立金刚石串珠的磨损模型。进行金刚石绳锯切割花岗石试验,试验结果表明,在金刚石串珠锯切过程中,单颗串珠沿其轴向出现不均匀磨损。串珠前端的磨损量会明显大于串珠中、后端磨损量,串珠后端的磨损也略大于串珠中端的磨损,串珠呈现腰鼓状磨损;串珠前端金刚石磨粒的平均出露高度高于串珠中、后端的磨粒平均出露高度,但在岩屑的磨蚀作用下,串珠前端的高出露金刚石磨粒容易产生非正常脱落。串珠磨损可分为腰鼓形状成形及腰鼓形状保持两个阶段。在切削负荷及岩屑磨蚀的共同作用下,串珠前、中、后三个部分在两个阶段的磨损表现各不相同。串珠前端是以岩屑磨蚀为主,而对于串珠中端,则是主要承受切削负荷。串珠后端两种作用的影响程度相对较弱。     

Study of face milling of hardened AISI D3 steel with a special design of carbide tools

This paper studies the impact of a special carbide tool design on the process viability of the face milling of hardened AISI D3 steel (with a hardness of 60 HRC), in terms of surface quality and tool life. Due to the advances in the manufacturing of PVD AlCrN tungsten carbide coated tools, it is possible to use them in the manufacturing of mould and die components. Experimental results show that surface roughness (R_a) values from 0.1 to 0.3 μm can be obtained in the workpiece with an acceptable level of tool life. These outcomes suggest that these tools are suitable for the finishing of hardened steel parts and can compete with other finishing processes. The tool performance is explained after a tool wear characterization, in which two wear zones were distinguished: the region along the cutting edge where the cutting angle (κ) is maximum (κ_max) for a given depth of cut, and the zone where the cutting angle is minimum (κ?=?0) that generates the desired surface. An additional machining test run was made to plot the topography of the surface and to measure dimensional variations. Finally, for the parameters optimal selection, frequency histograms of R_a distribution were obtained establishing the relationship between key milling process parameters (V_c and f_z), surface roughness and tool wear morphology.     

Optimization of machining parameters using magnetic-force-assisted EDM based on gray relational analysis

This work developed a novel process of magnetic-force-assisted electrical discharge machining (EDM) and conducted an experimental investigation to optimize the machining parameters associated with multiple performance characteristics using gray relational analysis. The main machining parameters such as machining polarity (P), peak current (I _P), pulse duration (τ _P), high-voltage auxiliary current (I _H), no-load voltage (V), and servo reference voltage (S _V) were selected to explore the effects of multiple performance characteristics on the material removal rate, electrode wear rate, and surface roughness. The experiments were conducted according to an orthogonal array L18 based on Taguchi method, and the significant process parameters that affected the multiple performance characteristics of magnetic-force-assisted EDM were also determined form the analysis of variance. Moreover, the optimal combination levels of machining parameters were also determined from the response graph and then verified experimentally. The multiple performance characteristics of the magnetic-force-assisted EDM were improved, and the EDM technique with high efficiency, high precision, and high-quality surface were established to meet the demand of modern industrial applications.     

Sustainability analyses of cutting edge radius on specific cutting energy and surface finish in side milling processes

The aim of this work is to determine the influence of cutting edge radius on the specific cutting energy and surface finish in a mechanical machining process. This was achieved by assessing the direct electrical energy demand during side milling of aluminium AW6082-T6 alloy and AISI 1018 steel in a dry cutting environment using three different cutting tool inserts. The specific energy coefficient was evaluated as an index of the sustainable milling process. The surface finish of the machined parts was also investigated after machining. It was observed that machining with the 48.50-μm cutting edge radius insert resulted in lower specific cutting energy requirements when compared with the 68.50 and 98.72-μm cutting edge radii inserts, respectively. However, as the ratio of the undeformed chip thickness to cutting edge radius is less than 1, the surface roughness increases. The surface roughness values gradually decrease as the ratio of undeformed chip thickness to cutting edge radius (h/r _e) tends to be 1 and at minimum surface roughness values when the ratio of h/r _e equalled to 1. However, the surface roughness values increased as h/r _e becomes higher than 1. This machining strategy further elucidates the black box and trade-offs of ploughing and rubbing characteristics of micro machining and optimization strategy for minimum energy and sustainable manufacture.     

Comparative evaluation of machinability characteristics of Nimonic C-263 using CVD and PVD coated tools

Machining of Nimonic C-263 has always been a challenging task owing to its hot strength, low thermal conductivity, tendency to work harden and affinity towards tool materials. Although coated tools have been used to overcome some of these challenges, selection of coated tool with appropriate deposition technique is of immense significance. The current study attempts to comparatively evaluate various performance measures in machining of Nimonic C-263 such as surface roughness, cutting force, cutting temperature, chip characteristics, and tool wear with particular emphasis on different modes of tool failure for commercially available inserts with multi-component coating deposited using chemical vapour deposition (CVD) and physical vapour deposition (PVD) techniques. Influence of cutting speed (V_c) and machining duration (t) has also been investigated using both coated tools. The study demonstrated remarkable decrease in surface roughness (74.3%), cutting force (6.3%), temperature (13.4%) and chip reduction coefficient (22%) with PVD coated tool consisting of alternate layers of TiN and TiAlN over its CVD coated counterpart with TiCN/Al₂O₃ coating in bilayer configuration. Severe plastic deformation and chipping of cutting edge and nose, abrasive nose and flank wear along with formation of built-up-layer (BUL) were identified as possible mechanisms of tool failure. PVD coated tool successfully restricted different modes of tool wear for the entire range of cutting speed. Superior performance can be attributed to the hardness and wear resistance properties, thermal stability due to presence of TiAlN phase and excellent toughness owing to PVD technique and multilayer architecture.     

Parametric optimization of CNC turning process for hybrid metal matrix composite

Machining of hybrid metal matrix composite is difficult as the particulates are abrasive in nature and they behave like a cutting edge during machining resulting in quick tool wear and induces vibration. An attempt was made in this experimental study to evaluate the machining characteristics of hybrid metal matrix composite, and a mathematical model was developed to predict the responses, namely surface finish, intensity of vibration and work-tool interface temperature for known cutting condition while machining was performed in computer numerical control lathe. Design of experiments approach was used to conduct the trials; response surface methodology was employed to formulate a mathematical model. The experimental study inferred that the vibration in V _x, V _y, and V _z were 41.59, 45.17, and 26.45 m/s², respectively, and surface finish R _a, R _q, and R _z were 1.76, 3.01, and 11.94 μm, respectively, with work-tool interface temperature ‘T’ of 51.74 °C for optimal machining parameters, say, cutting speed at 175 m/min, depth of cut at 0.25 mm and feed rate at 0.1 mm/rev during machining. Experimental results were in close conformity with response surface method overlay plot for responses.     

Eine verallgemeinerung der höheren planetenbewegungen

If Σ_j performs a relative rotation Σ_j/Σ_j−1 with respect to Σ_j−1 about a point A_j−1ϵΣ_j−1 with constant angular velocity (j = 1, …, n), the product Σ_n/Σ₀ of these rotations is called planetary motion (W. Wunderlich[15]). This paper deals with a generalization (V-planetary motion) which is obtained by replacing an arbitrary number of relative rotations by translations with constant velocity. The polodes and the envelopes of straight lines (G-trochoids) are proved to be V-trochoids, i.e. point paths under V-planetary motions. The motion of the canonical frame along a G-trochoid is a V-planetary motion again. Therefore the evolute and all evolutoids of G-trochoids are G-trochoids. The isoptic curve of two G-trochoids is proved to be a V-trochoid. Furthermore it is given a characterization of G-trochoids, which contains an unknown characterization of cycloidal trochoids. Finally, examples for the occurence of V-trochoids are given. These curves occur, for instance, as plane intersections of ruled surfaces generated by certain space motions.     

Robust weighting applied to optimization of AISI H13 hardened-steel turning process with ceramic wiper tool: A diversity-based approach

A mixed ceramic is a type of cutting-tool material widely employed for machining hardened steels. The usage of a mixed ceramic along with a wiper geometry can help double the feed rate, thereby increasing productivity while keeping the surface roughness (Ra) as low as possible. Analyses of manufacturing processes, such as a machining process, show that the various possible controlled parameters can be modeled by multiobjective mathematical models to ensure their optimization. Hence, the aim of this study was optimize a hard turning process using a robust weighting based on diversity to choose the final Pareto optimal solution of the multiobjective problem. The responses of the material removal rate (MRR), Ra parameter, and cutting force (Fc) were modeled by using the response surface methodology; in this methodology, decision variables, such as the cutting speed (Vc), feed rate (f), and depth of cut (d), are employed. The diversity index, as a decision-making criterion, proved to be useful in mapping the regions of minimum variance within the Pareto optimal responses obtained in the optimization process. Hence, the study demonstrates that the weights used in the multiobjective optimization process influence the prediction variance of the obtained response.     

Prediction of cutting forces in mill turning through process simulation using a five-axis machining center

Mill turning is a process applied in the milling of a curved surface while the workpiece rotates around its center. Depending on the eccentricity of the tool, when a flat-end mill tool performs a curved trajectory perpendicular to the rotation axis of the tool, its bottom part is engaged in removing material. In order to optimize the process, the cutting force needs to be predicted. Hence, in this work, an approach to simulating the cutting force in mill turning is presented. The case of non-eccentricity of the tool is considered. The undeformed chip geometry is modeling as a function of the tool engagement considering the process kinematics. Experiments were conducted on a five-axis machining center enabling the measurement of the X–Y and Z components of the cutting forces. In order to verify the influence of the bottom part of the tool on the cutting forces, experiments were carried out using three different cutting depths. Numerical cutting simulations and experimental test results are compared to validate the proposed approach.     

Effect of tilted plate vibration on solidification and microstructural and mechanical properties of semisolid cast and heat-treated A356 Al alloy

To optimize the machining process, finding the minimum uncut chip thickness is of paramount importance in micro-scale machining. However, strong dependency of the minimum uncut chip thickness to the tool geometry, workpiece material, tool-work friction, and process condition makes its evaluation complicated. The paper focuses on determination of the minimum uncut chip thickness experimentally during micro-end milling of titanium alloy Ti-6Al-4V with respect to influences of cutting parameters and lubricating systems. Experiments were carried out on a CNC machining center Kern Evo with two flute end mills of 0.8 and 2 mm diameters being used in the tests for micro- and macro-milling, respectively. It was found that the micro-milling caused more size effect than macro-milling due to higher surface micro-hardness and specific cutting forces. The specific cutting force depended strongly on feed rate (f _z) and lubricating system, followed by depth of cut (a _p) and cutting speed (v _c), mainly in the micro-scale. All output parameters were inversely proportional to the specific cutting force. Finally, depending on different process parameters during micro-milling of Ti-6Al-4V, the minimum uncut chip thickness was found to vary between 0.15 and 0.49 of the tool edge radius.