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This paper details the development of a hybrid process to machine micro-holes on a difficult to machine material like titanium (Ti-6Al-4V) alloy using a magnetic field-assisted electric discharge machining process. In EDM machining of micro-holes, there are certain issues like the circulation of dielectric and removal of debris which results in, a low aspect ratio of the hole, low material removal rate, deformed machined geometry, high tool wear rate and low surface integrity of workpiece. This research work aims to overcome these issues by combining processes like the magnetic field in the sparking region and the addition of powder particles to the dielectric medium. To study the effect of this hybrid process, the orthogonal array was formed and trials were conducted using the parameters input current (Ip), voltage (V), pulse on time (Ton) and pulse off time (Toff). The experimental results were compared with the non-hybrid machining process. The result shows that the material removal rate is considerably increased in the hybrid process.

In the present research, work focus has been given to determine mechanical properties of biodegradable industrial waste tea leaf fiber (WTLF), banana and flax fiber reinforced hybrid polymer composites using experimental approach. Banana fibers and WTLF were alkali treated with 5% NaOH solution. The hybrid composite laminates were manufactured using manually operated compression moulding machine with the volume fraction of 40:60 (Fiber: Matrix). As per ASTM standard, the mechanical characteristics were studied. The experimental results showed excellent mechanical characteristics for 5 wt% WTLF and 25- wt% banana fiber reinforced hybrid composites. The fractography analysis of untreated and alkali treated composites were examined using Scanning Electron Microscopy (SEM) and results revealed that superior mechanical bonding existed between fiber and polymer in case of alkali treated fiber composites.

Nowadays Titanium and its alloy materials are highly preferred for the parts of aircraft structures due to their unique properties such as good corrosive resistant and higher strength to weight ratio is sustained even at increased temperature. Even though these alloy materials are wicked for its low thermal conductivity and categorized as hard to machine alloys. Drilling of titanium alloys is a critical machining process in the fields such as medical, automobile and defence applications. In this alloy Ti–6Al–4V alloy is generally used for parts that need higher reliability therefore, surface finish and various failure to the adjacent surface layers of machined areas must to be resolved as per the customer requirement. This research work focuses on experimental study and optimization of machining parameter during dry drilling of titanium alloy (grade 5). An 8 mm diameter and 120 degree point angle solid carbide drill bits are used to carry out the experiments. The range of drilling spindle speed chosen for the experiment was between 20 to 50 m/min also feed rates were 0.05, 0.1, 0.15, and 0.2 mm/rev. Experimental analysis was done by focusing on surface roughness, circularity, hole diameter and exit burr for maintaining good quality hole. A Portable surface roughness measuring device was utilised to find surface roughness in the direction of feed on work piece material. Circularity and diameter of the machined hole was found by co-ordinate measuring machine (Contura-G2-Zeiss). From this experimental investigation it is found that feed has higher significance on surface finish when compared to drilling speed but when considering the circularity error speed has higher significance. Optimization and validation of experimental results was done by using the application of Taguchi’sdesign of experiments with signal to noise ratio graph and ANOVA

During trimming of edges of carbon fiber-reinforced polymer composite parts, issues such as resin degradation, delamination, and poor surface finish at the trimmed edges, and increased tool wear in cutting tools used is common. Therefore, it is essential to carry out investigations on edge trimming of carbon fiber-reinforced polymer to find the effect of cutting forces generated and the cutting tool temperature induced at different high speeds and feeds conditions. In this work, two different-coated router tools of titanium aluminum nitride-coated and diamond-like carbon-coated routers were used for investigating the effect of these coatings on cutting force and cutting tool temperature which affect the surface quality of trimmed carbon fiber-reinforced polymer. From the investigation, it was found that the diamond-like carbon-coated router tool has generated lower cutting forces, cutting tool temperatures, and, in turn, better surface finish even at high-speed conditions when compared to other tools. Due to the complex geometry of the router tool, online tool wear monitoring by acoustic emission technique was employed. Acoustic emission signals were taken as the measuring index of tool wear which shows good correlation with direct tool wear measurements. From the experiments, it was found that the tool performance of the diamond-like carbon-coated router is superior when compared to other tools. In addition, for edge trimming of carbon fiber-reinforced polymer composite parts, the diamond-like carbon router tool performed without much disturbance for a length of machining of around 5.9 m which is about 46% of increase in length of machining when compared to uncoated router tool.

This research work was carried out to find a suitably treated electrode for the required machining output response like MRR and TWR. The experimental design was formed using Box–Behnken design. Experiments were conducted to machine 500 µm holes on titanium (Ti-6Al-4V) alloy using copper electrodes. Input parameters selected were input current (Ip), pulse-on time (Ton), and pulse-off time (Toff). Material removal rate and tool wear rate were analyzed using contour plots. Based on these experimental data, the grey relational analysis technique was applied to find the optimal parameters for achieving maximum MRR and minimum TWR. Optimal parametric values obtained were input current (Ip) 4.0 A, pulse on time (Ton) 2.0 µs and pulse off time (Toff) 6.4 µs. The achieved optimized parameters were further used to conduct experiments with cryogenic treated and coated electrodes. Electrodes were coated with conductive materials (silver, nickel, and zinc) and non-conductive material (epoxy). The experimental results showed each type of electrode enhances a particular machining characteristic such as silver-coated electrode produced a higher value of MRR, epoxy-coated electrode achieved minimum TWR. It is observed from the results that this work can be applied to identify the suitable electrode for producing the desired machining output characteristics.

The present study aims in analyzing the mechanical behavior of natural fiber (abaca) reinforced polymeric composites under dynamic conditions. It is evident from the past research reports that natural fiber offers desirable physico-mechanical properties to the added polymers. In the present research work, abaca fiber is utilized for the preparation of composites due to its promising mechanical properties and resistance to salt water corrosion, its lignin content is 15% and grows up to 3 m. Abaca is extracted from leaf sheath of Manila hemp plant, it is a kind of banana family. Influence of temperature on the mechanical behavior of natural fibers needs to be identified to ensure its usage for high performance applications. Pure and chemically treated abaca fiber based vinyl ester composites are subjected to dynamic mechanical analysis (DMA). The reason for the chemical treatment of abaca fiber is to enhance its interfacial bonding with base matrix. Fourier transform infrared spectroscopy (FT-IR) analysis signifies the morphological changes in abaca fiber after chemical treatment. Storage modulus (E') and damping characteristics of abaca fiber reinforced vinyl ester composites are comparatively higher than in neat polymer. In addition, surface treatment of fiber demonstrates significant enhancement in storage modulus compound compared to pure and raw fiber reinforced polymer due to strong physical interaction between fiber and matrix.

Wire electric discharge grinding has been developed to generate cylindrical profiles on hard-to-machine microparts. The outcome of the part is influenced by the process conditions and the rotational speed of the spindle. This paper investigates the effects of machining parameters on material removal rate (MRR), surface roughness and circularity during wire electrical discharge grinding process of tungsten carbide workpiece. Experiments have been carried out by varying process conditions such as peak current, open circuit voltage, pulse off time, servo voltage and number of passes. Pulse current has the highest significance to obtain maximum MRR. To obtain the best surface quality, pulse current, number of passes and pulse off time are identified as the most significant parameters. Using the technique of order preference by similarity to ideal solution, the optimal conditions estimated are pulse current (38 A), open circuit voltage (60 V) and pulse off time (24 µs) for finish machining.

In recent decades, the noticeable amount of research has been carried out in the role of non-metallic inclusions and their relationship to the machinability of various steels. This paper compares the performances of EN alloy steels for varied machinability aspects throughout the machining under dry cutting condition. Cutting speed, feed, and depth of cut were the major ruling parameters affecting the machinability of materials. The present works review the machining of different alloy steels and the role of non-metallic inclusions in them. More precisely, the effects of composition and morphology of inclusions on machinability factors such as cutting force and chip size and shape are discussed and summarized. EN 1A Pb&Te alloy steel provides lower cutting force, and good curl or breakdown chips thus provides the better machinability.

This present study aims to investigate the dry sliding wear behaviour of tungsten disulfide (WS2) particle reinforced bronze matrix composite against surface hardened steel and to discover the optimum wear parameter values such as applied load, sliding distance, sliding velocity and volume fraction of reinforcement to reduce the specific wear rate. The composite specimens were fabricated by liquid metallurgy route by varying the volume fraction of solid lubricant particles and prepared as per American Society for Testing of Materials (ASTM) G99-95. The experiments were carried out based on Taguchi design of experiments technique with L27 orthogonal array. The wear tests were conducted in pin-on disc wear testing machine for different loads - 20N, 40N and 60N, sliding velocities - 2.09m/s, 2.62 m/s and 3.14m/s and sliding distances of 600m, 1200m and 1800m in unlubricated conditions. The significant influence of wear parameters on sliding wear, interactions and optimum combination of wear parameter values to minimize the wear rate were obtained by signal-to-noise (S/N) ratio and analysis of variance (ANOVA). The results demonstrated that inclusion of tungsten disulfide particles decreased the wear rate of bronze and also the increases in amount of secondary phase increase the wear resistance of composites. The effect of solid lubricant particle on interfacial temperature was also studied and reported. It was found that percentage of solid lubricant and load are the most significant factors influencing the friction and wear properties of composites. The results revealed that, WS2 particle reinforced bronze matrix composites were the potential component can be replaced for pure bronze products in wear resistance applications.

Titanium alloys present superior properties like resistance to corrosion, high strength to weight ratio etc, but possess poor machinability. Titanium alloy Ti-6Al-4V is the most commonly used titanium alloy in aerospace and medical device industries. Titanium and its alloys are notorious for their poor thermal properties and are classified as difficult-to-machine materials. Drilling is an important machining process since it is involved in nearly all titanium applications. It is desirable to develop optimized drilling processes for Ti and improve the hole characteristics such as hole diameter, circularity and exit burr of currently available processes. Due to the low machinability of the alloys under study, selecting the machining conditions and parameters is crucial. The range of spindle speed and feed rate, which provide a satisfactory tool life, is very limited. The hole quality (hole diameter and circularity), thrust force, torque and exit burr were evaluated at various spindle speeds, feed rates combinations. The optimized parameter is chosen using the multi-objective weighted sum optimization technique.

In recent years, the utilization of metal matrix composites (MMC) have increased in engineering fields of automobile, aviation, aerospace, construction and microelectronics. In conjunction with innovations in these advanced materials, machining them to obtain good dimensional accuracy and surface integrity has become a challenge. In this present work, 15 % (by weight) SiC particle reinforced aluminium is synthesized by stir casting technique. The synthesized MMC is end milled using Ø16 mm carbide end mill in a CNC milling machine and the machining parameters explicitly cutting speed, feed rate and depth of cut are optimised for minimum surface roughness and total force acting on the tool using response surface methodology (RSM) and artificial neural network (ANN). The un-coated cutting tool insert was compared with the nanocomposite coated insert on tool wear at optimised cutting conditions.

Composites are used in conjunction with another material to form a multi-material stack-up, which results in greater strength to weight ratios. In a wide range of aerospace applications dissimilar material stack-ups of composites and aluminium and/or titanium are used. Drilling is probably the most common machining operation applied to composites since components made out of composite materials are usually near net shaped and require only holes for assembly integration. In this investigation, experiments were conducted by varying the drilling parameters and determining the optimum cutting conditions for drilling of CFRP/Ti stacks using Genetic Algorithm (GA) optimization technique. Tool wear study was performed by drilling 100 holes each with 118° and 130° point angle drills. Less progressive tool wear and better chip evacuation was achievable in 130° point angle drills when compared with 118°point angle drills.

Titanium alloys are fascinating materials due to their unique high strength–weight ratio that are maintained even at elevated temperatures, exceptional fracture and corrosion resistance characteristics along with their compatibility over polymers composite materials. On the other hand, titanium and its alloys are notorious for their poor thermal properties and high reactivity with cutting tools which classifies as difficult-to-machine materials especially at higher cutting speeds. High Speed Machining (Vc ≥ 54 m/min) attracts huge benefit on material removal rate, machining time, cutting forces, heat removal and tool life. To enhance machinability, the effect of the rake angle on the cutting force and temperature must be thoroughly understood. In order to overcome the machinability issues associated with machining of Ti alloys, an attempt has been made in this study to observe the effect of rake angle, speed, feed rate on the cutting forces and temperature along with chip formation in orthogonal turning process supported through out with AdvantEdge FEA. A total of 48 experiments were performed with four different rake angles at three different higher spindle speeds along with four different levels of feed with a constant depth of cut of 2.75 mm. Final arguments support over small positive rake angle along with high spindle speeds and small feed values for low temperature and better surface finish. AdvantEdge FEA comparison shows close agreement with experimental results particularly at higher spindle speeds and feed levels suggesting them as better option for further advancement in high speed turning of titanium alloys.

International audience; In this paper, experimental and numerical study of drilling of carbon fibre reinforced plastic (CFRP) laminate with aluminium alloy stacks has been carried out. Drilling of these multi-materials is a challenging task to manufacturing engineers because of different mechanical properties of materials. In this work, the impact of the machining parameters on the effect of twist drill and the geometry of double cone drill on cutting forces, holes quality and on CFRP/Al interface have been investigated. From the experimental study, it was found that the double cone drills induce less thrust force compared to the standard twist drill. From the numerical analysis based on the linear fracture mechanics of the CFRP and the plastic behaviour of the aluminium with isotropic hardening, on the one hand, the critical thrust force responsible for the delamination of the last ply as a function of the aluminium thickness has been identified and on the other hand, the maximum thrust force responsible for the interface separation of CFRP/AI has been predicted as a function of the aluminium thickness.

International audience; Drilling and fastening of hybrid materials in one-shot operation reduces cycle time of assembly of aerospace structures. One of the most common problems encountered in automatic drilling and riveting of multimaterial is that the continuous chips curl up on the body of the tool. Drilling of carbon fiber reinforced plastic (CFRP) is manageable, but when the minute drill hits the aluminium (Al) or titanium (Ti), the hot and continuous chips produced during machining considerably damage the CFRP hole. This study aims to solve this problem by employing nano-coated drills on multimaterial made of CFRP and aluminium alloy. The influence of cutting parameters on the quality of the holes, chip formation and tool wear were also analyzed. Two types of tungsten carbide drills were used for the present study, one with nano-coating and the other, without nano coating. The experimental results indicated that the shape and the size of the chips are strongly influenced by feed rate. The thrust force generated during drilling of the composite plate with coated drills was 10-15% lesser when compared to that generated during drilling with uncoated drills; similarly, the thrust force in the aluminium alloy was 50% lesser with coated drills when compared to thrust force generated without coated drills. Thus, the use of nano-coated drills significantly reduced the surface roughness and thrust force when compared with uncoated tools.

International audience; The thrust force and surface roughness of plain carbide drill (K20) with drill parameters (drill diameter, spindle speed and feed rate) in drilling carbon fibre reinforced plastic (CFRP) laminate/aluminium (Grade 2024) stack was experimentally investigated in this study. A L27 orthogonal array and signal-to-noise (S/N) were employed to analyze the effect of drill parameters. Using Taguchi method for design of a robust experiment, the interactions among factors are also investigated. The analysis of variance (ANOVA) shows that the feed rate and drill diameter are the most significant parameters to the overall performance while drilling CFRP/al stack. Nano-coated tools used for drilling made of tungsten carbide; show that the shape and the size of the chips are strongly influenced by the feed rate. The thrust force generated during drilling of the composite materials with coated drills is 10% to 15% less when compared with the thrust force generated during drilling with uncoated drills. Moreover, the thrusts forces in the aluminium are 50% less with coated drills compared to thrust force generated without coated drills. Apart from the forces the nanocoated drills make it possible to carry out holes in the composite plates and aluminium with surface roughness 50% lesser compared with those obtained with uncoated tools.

Carbon fibre reinforced plastics (CFRP) and titanium (Ti) stacks have been steadily replacing metals as choice for engineering materials in aerospace applications. Although materials can be manufactured separately and stacked together to attain a near-net shape, it still involves post processing operations such as trimming and drilling. In order to drill holes efficiently without defects (delamination, circularity, variation in hole diameter) in the CFRP/Ti stacks, it is essential to understand the machining behavior of stacks. An experimental study on the drilling of CFRP/Ti stacks was conducted using K20 carbide drill. The drilling characteristics were evaluated for drilling force and torque, delamination in CFRP, drilled-hole quality (hole diameter and circularity) and exit burr height in Ti. This paper describes an attempt made to maximize the hole quality parameters by employing multi-objective optimization using weighted sum method.

International audience; Drilling of CFRP/Al or CFRP/Ti, or AI/CFRP/Ti is a challenge to manufacturing engineers. Drilling of CFRP is manageable but the minute drill hits the Al or Ti, those hot and continuous chips destroy the hole. Few studies are carried out in this aspect; CFRP/Al is not reported till date. It is important to select right process parameters when drilling multimaterial stack since each material in the stack requires a different set of machining parameters. Hence, Drilling trials have been carried out in carbon-fibre reinforced plastics (CFRP)/aluminium (Grade 2024) stack without coolant, with plain carbide (K20) drills of various diameters to choose optimum process parameters. The parametric influences on thrust force, torque as well as surface finish were experimentally evaluated. The experimental results show that the quality of holes can be improved by proper selection of cutting parameters. This is substantiated by monitoring thrust force, torque, surface finish, circularity and hole diameter. For the CFRP, the circularity is found to be around 6 mu m at low feed rates, when the feed is increased the circularity increases to 25 mu m. The wear tests carried out show that, during first 30 holes, thrust force in CFRP undergoes a more important increase (90%) than thrust force of aluminium (6%).

Titanium and its alloys are attractive materials due to their unique high strength-weight ratio that is maintained at elevated temperatures. Ti-6Al-4V alloy are notorious for their poor thermal properties and are classified as difficult-to-machine materials. Drilling is an important machining process since it is involved in nearly all titanium applications. It is desirable to develop optimised drilling processes for Ti and/or improve the hole characteristics such as hole diameter, circularity and exit burr of currently available processes. Due to the low machinability of the alloy under study, selecting the machining conditions and parameters is crucial. The hole quality, thrust force, torque and exit burr were evaluated at various spindle speeds, feed rates combinations. The optimised parameter is chosen using the multi-objective weighted sum optimisation technique. The tool life for the optimised parameter was studied and the life of the carbide drill was observed to be 140 holes in drilling of titanium.