Studies on Machining Parameters While Milling Particle Reinforced Hybrid (Al6061/Al2O3/Gr) MMC

In this article, response surface methodology has been used for finding the optimal machining parameters values for cutting force, surface roughness, and tool wear while milling aluminum hybrid composites. In order to perform the experiment, various machining parameters such as feed, cutting speed, depth of cut, and weight (wt) fraction of alumina (Al₂O₃) were planned based on face-centered, central composite design. Stir casting method is used to fabricate the composites with various wt fractions (5%, 10%, and 15%) of Al₂O₃. The multiple regression analysis is used to develop mathematical models, and the models are tested using analysis of variance (ANOVA). Evaluation on the effects and interactions of the machining parameters on the cutting force, surface roughness, and tool wear was carried out using ANOVA. The developed models were used for multiple-response optimization by desirability function approach to determine the optimum machining parameters. The optimum machining parameters obtained from the experimental results showed that lower cutting force, surface roughness, and tool wear can be obtained by employing the combination of higher cutting speed, low feed, lower depth of cut, and higher wt fraction of alumina when face milling hybrid composites using polycrystalline diamond insert.     

Investigation on performance of abrasive water jet in machining hybrid composites

For machining of composites, abrasive water jet machining is widely employed. For assembly of the machine tool structure, production of slots is essential. In this paper, abrasive water jet machining of composite laminates was experimentally investigated for various cutting parameters in terms of average surface roughness (R_a) and kerf taper (K_t). By generating a response surface model, the experimental values obtained for quality characteristics (R_a and K_t) were empirically related to cutting parameters. The effects of cutting parameters on quality characteristics were analyzed by utilizing empirical models and also optimized within the tested range based on desirability approach. The optimum parameter levels were also validated by confirmation test. From this investigation, it is evident that for obtaining a minimum kerf taper, traverse speed, water pressure, and abrasive mass flow rate are significant parameters and for obtaining less surface roughness traverse speed is the significant parameter.     

Experimental investigations on cryogenic cooling by liquid nitrogen in the end milling of hardened steel

Milling of hardened steel generates excessive heat during the chip formation process, which increases the temperature of cutting tool and accelerates tool wear. Application of conventional cutting fluid in milling process may not effectively control the heat generation also it has inherent health and environmental problems. To minimize health hazard and environmental problems caused by using conventional cutting fluid, a cryogenic cooling set up is developed to cool tool–chip interface using liquid nitrogen (LN₂). This paper presents results on the effect of LN₂ as a coolant on machinability of hardened AISI H13 tool steel for varying cutting speed in the range of 75–125 m/min during end milling with PVD TiAlN coated carbide inserts at a constant feed rate. The results show that machining with LN₂ lowers cutting temperature, tool flank wear, surface roughness and cutting forces as compared with dry and wet machining. With LN₂ cooling, it has been found that the cutting temperature was reduced by 57–60% and 37–42%; the tool flank wear was reduced by 29–34% and 10–12%; the surface roughness was decreased by 33–40% and 25–29% compared to dry and wet machining. The cutting forces also decreased moderately compared to dry and wet machining. This can be attributed to the fact that LN₂ machining provides better cooling and lubrication through substantial reduction in the cutting zone temperature.     

Development of ANFIS model and machinability study on dry turning of cryo-treated PH stainless steel with various inserts

This present investigation deals about the machinability comparison of cryogenically treated 15-5 PH stainless steel with various cutting tools such as uncoated tungsten carbide, cryogenic-treated tungsten carbide and wiper geometry inserts. Cryo-treated PH stainless steel is considered as the work material in this investigation and experimental trials were performed under dry turning condition. The machinability aspects considered for evaluation are cutting force (F_z), surface roughness (R_a) and tool wear. The outcomes of experimentation reveal that the tungsten carbide inserts which are cryogenically treated provide improved performance in machining while comparing with conventional and wiper geometry inserts at all machining conditions. The measured cutting force and the observed flank wear were less for the cryo-treated inserts. However, wiper tool produces a better surface finish during machining. An artificial intelligence decision-making tool named Adaptive Neuro Fuzzy Inference System has been evolved to determine the relation among the considered input machining variables and output measures, namely cutting force and surface roughness of the machined surface. An analysis has been performed to compare the results obtained from developed models and experimental results.     

AWJ machinability performance of CS/UPR composites with the effect of chemical treatment

This work focuses on the effect of chemical treatment of coconut sheath/unsaturated polyester (CS/UPR) composite on the performance of abrasive waterjet machining (AWJM). Two different chemical treatments, namely alkali (NaOH) and trichlorovinylsilane, were imposed on the CS fiber. Further, the induced compressive strength arising as a result of AWJM was studied along the radial and depth directions of the composite. Experimental results revealed significantly lower induced stress at all points compared to the ultimate stress of CS/UPR composites except the free-edge loading condition. The chemically treated composites also exhibited inconsistent results in the machining characteristics such as kerf taper angle (T_a) and surface roughness (R_a) under varying cutting conditions. However, no direct correlation was seen between interfacial adhesion and T_a and R_a of the cutting zone. The maximum decrease of 12% of T_a and 22% of R_a was found for silane-treated composites compared to the untreated ones. In addition, the composite failure mechanisms such as fiber pullout, fiber breakage, interfacial debonding, matrix failure, and voids were identified in the cutting surfaces through scanning electron microscopy analysis.     

Effects of geometric angle and cutting speed on cutting forces and tool wear of ceramic cutting tools during peripheral up-milling of high-density fiberboard

In this paper, cutting forces and tool wear of ceramic cutting tools are investigated by up-milling high-density fiberboard under different geometric angles and cutting speeds. The results show that tangential force (F_t) and normal force (F_r) decrease with the increase of rake angle. The values of F_t and F_r at the higher speed cutting condition are lower than that at the lower speed condition. The flank wear (VB) declines with increased clearance angle and decreased cutting speed. The tool wear patterns observed on the ceramic cutting tools are pull-out of grain, cracking, tipping, and flanking. Abrasive wear and adhesive wear are the main mechanisms of the ceramic cutting tools. In all, on the premise of guaranteeing the ceramic cutting tools’ strength, the ceramic cutting tool with a bigger rake angle and clearance angle is advisable in high-density fiberboard machining, in terms of lowering the energy consumption and production cost required for machining.     

Optimal selection of cutting parameters in multi-tool milling operations using a genetic algorithm

In the milling of large monolithic structural components for aircraft, 70–80% of the total cut volume is removed using high-speed roughing operations. In order to achieve the economic objective (i.e. optimal part quality in minimal machining time) of this process, it is necessary to determine the optimal cutting conditions while respecting the multiple constraints (functional and technological) imposed by the machine, the tool and the part geometry. This work presents a physical model called GA-MPO (genetic algorithm based milling parameter optimisation system) for the prediction of the optimal cutting parameters (namely, axial depth of cut (a _p), radial immersion (a _e), feed rate (f _t) and spindle speed (n)) in the multi-tool milling of prismatic parts. By submitting a preliminary milling process plan (i.e. CL data file) generated by CAM (computer-aided manufacturing) software, the developed system provides an optimal combination of process parameters (for each machining feature), respecting the machine–tool–part functional/technological constraints. The obtained prediction accuracy and enhanced functional capabilities of the developed system demonstrate its improved performance over other models available in the literature.     

Micro-mechanical modeling of machining of FRP composites – Cutting force analysis

Orthogonal machining of unidirectional carbon fiber reinforced polymer (UD-CFRP) and glass fiber reinforced polymer (UD-GFRP) composites is simulated using finite element method (FEM). A two-phase micro-mechanical model with fiber assumed elastic and the matrix elasto-plastic is used to estimate the cutting forces during machining. A cohesive zone simulated the interface debonding between the fiber and matrix. Fiber failure was based on maximum principal stresses reaching the tensile strength. The matrix elastic modulus was degraded to include damage once yield strength was reached. The model assumes plane strain and quasi-static condition. The cutting forces during orthogonal machining were studied both experimentally and numerically for a range of fiber orientations (θ), depths of cut (t) and tool rake angles (γ). The contact forces developed between the tool and the fiber provided a good estimate of the cutting (F_h) and thrust (F_v) forces during the orthogonal cutting process. The failure of fiber is found to be a combination of crushing and bending, with the bending effect becoming more significant as the fiber orientation changes from 90° to 15°.     

Impact of graphite particle on milling of Al/15Al2O3 and Al/15Al2O3/5Gr composites

ABSTRACT

Hybrid Metal Matrix Composites (MMCs) are a new class of composites, formed by a combination of the metal matrix and more than one type of reinforcement having different properties. Machining of MMCs is a difficult task because of its heterogeneity and abrasive nature of reinforcement, which results in excessive tool wear and inferior surface finish. This paper investigates experimentally the addition of graphite (Gr) on cutting force, surface roughness and tool wear while milling Al/15Al₂O₃ and Al/15Al₂O₃/5Gr composites at different cutting conditions using tungsten carbide (WC) and polycrystalline diamond (PCD) insert. The result reveals that feed has a major contribution on cutting force and tool wear, whereas the machined surface roughness was found to be more sensitive to speed for both composite materials. The incorporation of graphite reduces the coefficient of friction between the tool–workpiece interfaces, thereby reducing the cutting force and tool wear for hybrid composites. The surface morphology and worn tool are analyzed using scanning electron microscope (SEM). The surface damage due to machining extends up to 200 µm for Al/15Al₂O₃/5Gr composites, which is beyond 250 µm for Al/15Al₂O₃ composites.     

A NOTE ON INCORPORATING TOOL LIFE VARIABILITY IN THE GEOMETRIC PROGRAMMING FORMULATION OF MACHINING ECONOMICS PROBLEMS

This note incorporates tool life variability in the geometric programming formulation of machining economics problems by transforming the probability of tool failure while machining a part to a function of the cutting variables for both Markovian and non-Markovian tool failure processes. Numerical examples show that the stochastic nature of tool life cannot be ignored, since it results in different optimal cutting variable values compared to the deterministic tool life case.     

Single-point scratching of 6061 Al alloy reinforced by different ceramic particles

Aluminium alloys reinforced by ceramic particles have been widely used in aerospace and automotive industries for their high stiffness and wear resistance. However, the machining of such materials is difficult and would usually cause excessive tool wear. The effect of ceramic particles on the cutting mechanisms is also unclear. The purpose of this study is to investigate the cutting mechanisms and the relationship between specific energy of scratching and depth of cut (size effect). The single-point scratch test was carried out on 6061 Al and its composites reinforced by Al₂O₃ and SiC ceramic particles using a pyramid indenter. The results indicated that the scratch process was composed of rubbing, ploughing, plastic cutting and reinforcement fracture. A simple model was proposed to interpret the apparent size effect. The effect of reinforcement on the specific energy was correlated to the ratio of volume fraction to particle radius. The paper found that for machining MMCs, a larger depth of cut should be used to maintain a lower machining energy, especially for those with a larger ratio of volume fraction to particle radius.     

Tool life and surface integrity when milling inconel 718 with coated cemented carbide tools

Abstract

This paper presents a study of tool life and surface integrity while machining superalloy Inconel 718 using coated cemented carbide tools. In the machining of heat resistant superalloys used in aeronautical applications and classified as difficult‐to‐machine, tool life is an important parameter in evaluating the performance of the cutting tools. Surface quality of the workpiece is one of the important criteria in determining tool life. Our tests have been done under various combinations of speed, feed rate, and depth of cut to verify the change in surface roughness due to increasing tool wear. The behavior of the uncoated, TiN, and TiCN layers using various cutting conditions was analyzed. At the end, a choice of coating and optimization of the cutting conditions has been proposed.     

Computer-aided design of the effects of Fe2O3 nanoparticles on split tensile strength and water permeability of high strength concrete

In the present paper, two models based on artificial neural networks and genetic programming for predicting split tensile strength and percentage of water absorption of concretes containing Fe₂O₃ nanoparticles have been developed. To build these models, training and testing of the network by using experimental results from 144 specimens produced with 16 different mixture proportions were conducted. The data used in the multilayer feed forward neural networks models and input variables of genetic programming models have been arranged in a format of eight input parameters that cover the cement content, nanoparticle content, aggregate type, water content, the amount of superplasticizer, the type of curing medium, age of curing and number of testing try. According to these input parameters, in the two models, the split tensile strength and percentage of water absorption values of concretes containing Fe₂O₃ nanoparticles were predicted. The training and testing results in the neural network and genetic programming models have shown that every two models are of strong potential for predicting the split tensile strength and percentage of water absorption values of concretes containing Fe₂O₃ nanoparticles. Although neural network has predicted better results, genetic programming is able to predict reasonable values with a simpler method rather than neural network.     

A new formulation for martensite start temperature of Fe–Mn–Si shape memory alloys using genetic programming

This study presents genetic programming (GP) soft computing technique as a new tool for the formulation of martensite start temperature (M_s) of Fe–Mn–Si shape memory alloys for various compositions and heat treatments. The objective of this study is to provide a different formulation to design composition at certain ranges and to verify the robustness of GP for the formulation of such characterization problems. The training and testing patterns of the proposed GP formulation is based on well established experimental results from the literature. The GP based formulation results are compared with experimental results and found to be quite reliable.     

Spanende Bearbeitung von Bauteilen aus Al‐Matrix‐Verbundwerkstoffen

Machining of Components of Al Matrix Composites The microstructure of metal matrix composites consists of hard reinforcements which are embedded in a metal matrix. The high hardness of the reinforcements leads to a difficult processing of these materials. The present paper demonstrates the machining of components of Al matrix composites for the automotive and the aircraft industry. The components are SiC particle reinforced brake drums, cylinder blocks with local Si particle and Al₂O₃ short fiber reinforced cylinder liners and TiB₂ particle reinforced extrusion molding profiles. The investigations illustrate that good results can be achieved when machining these components by turning, boring, drilling and milling with polycrystalline diamond (PCD) or CVD diamond thick‐film cutting tool materials.     

Cutting Edge Wear of Tungsten Carbide Tool in Continuous and Interrupted Cutting of a Polymer Composite

An experimental study was conducted to evaluate the performance of C6 tungsten carbide, C2 tungsten carbide, and Polycrystalline Diamond (PCD) inserts in cutting Graphite/Epoxy (Gr/Ep) composites. Continuous and interrupted cutting tests under dry conditions were made to cut woven fabric and tape Gr/Ep composites. It was found that continuous cutting mode and high cutting speeds significantly reduce tool life of carbides. Machining of tape Gr/Ep reduces the tool life more than the machining of fabric work pieces. Also, C2 grade carbide inserts had a longer tool life than C6 carbide inserts despite the type of work piece or machining condition used. It was observed that a PCD insert's life was about 100 times of C2 carbide inserts during continuous cutting and at high speeds.     

Experimental studies on the cryogenic machining of biodegradable ZK60 Mg alloy using micro-textured tools

Reducing the contact area between the cutting tool rake surface and chip promotes the machining performance of the work material and increases the tool life. Magnesium alloys are ductile-lightweight materials that form continuous chips during machining. The present investigation discusses the orthogonal turning of ZK60 magnesium alloy with linearly textured cutting inserts under both dry and liquid nitrogen (LN₂) cooling conditions. Linear grooves that are parallel and perpendicular to chip flow direction were created using Nd-YAG laser on the tungsten carbide cutting inserts. The effect of texturing combined with the application of LN₂ cooling is studied by evaluating the machining temperature and forces, microhardness, surface roughness and tool wear. Textured tools considerably minimize the liaison area of the chip with the rake plane compared to non-textured tools, which resulted in favorable effects in machinability. In case of cryogenic machining, textured tools substantially minimize the friction by the coupled effect of micro-pool lubrication and the formation of thin-film lubrication between the tool–chip/tool–work interfaces. Parallel-textured tools aided with cryogenic cooling exhibit superior performance during machining among the different types of tools employed in the present investigation.     

Drehen und Fräsen pulvermetallurgischer Hartlegierungen für warmgehende Werkzeuge

Turning and Milling of Powder Metallurgical Hard Alloys for Tools in Hot Working Applications Hard metals are high wear resistant materials. The microstructure of these composites consists of hard phases which are embedded in a metal matrix. The high hardness and the high content of the hard phases lead to a difficult machining of these materials. The present study investigates the turning and milling of D3 cold work steel (X210 Cr 12) and the powder metallurgical Fe‐based alloys ASP60 and ASP23 + WC/W₂C. The cutting tool materials were polycrystalline cubic boron nitrides (CBN) and ceramic inserts. The machining process could be judged by means of tool wear and machining quality (surface roughness and changes in the surface near zone). The investigations illustrate that the machinability of the different hard metals depends on the cutting speed and the cutting tool material.     

Cutting Performance and Wear Mechanism of Multilayer Diamond-Coated Tools

Monolayer and multilayer diamond films are deposited on WC-Co cemented carbide by hot-filament chemical vapor deposition. The growth characteristics of diamond coatings are analyzed. Cutting performance characteristics such as tool life and the stability of machining process in the machining of presintered ZrO₂ are compared based on the variation of cutting speed and resultant cutting force, and workpiece surface roughness. For the monolayer diamond coatings, as the concentration of CH₄ increases from 1% to 5%, the diamond crystal is transformed from micron columnar crystal to nanocluster crystal. The multilayer diamond coatings combine the advantages of micron- and nanocrystalline structures. The multilayer diamond-coated tool exhibits longer service life and better machining quality. Because of the appearance of the brittle–plastic conversion mechanism, the surface integrity of ZrO₂ processed by multilayer diamond-coated tool is relatively high. As for the uncoated tool, the workpiece is mainly machined by brittle spalling. The interfacial stratified fracture system between the interlayers is proposed to be the toughening mechanism of the multilayer structure.     

Simultaneous determination of optimal machining conditions and tool replacement policies in constrained machining economics problems by geometric programming

This paper presents an analytical model for the simultaneous determination of the optimal machining conditions (cutting speed and feed) and the optimal tool replacement policy in constrained machining economics problems by geometric programming. The optimal preventive tool replacement policy is initially determined as a tool life fractile (independent of the underlying tool life distribution) and then it is expressed as actual tool life by utilizing the underlying tool life distribution applicable to the combination of tool material, workpiece properties, and machining conditions. Constraints on the optimal values of cutting speeds, feeds, and/or optimal tool replacement policy based on maximum allowable values and/or surface finish requirements are handled through the optimization of the dual objective function. It is shown that the optimal cost distribution does not depend on the cost coefficients in the objective function. Finally, the model is applied to two-stage systems where the necessary conditions are derived for increasing the synchronization between the two stages.