Akshay Dvivedi

Drilling Characteristics of Sisal Fiber-Reinforced Epoxy and Polypropylene Composites

Natural fiber composites have attracted global attention due to their lightweight, low-carbon footprint characteristics as well as good mechanical properties. Due to these distinct advantages, the application spectrum of these composites has grown at an unprecedented rate. These composites are used for making a wide variety of sophisticated engineering products; therefore, certain degree of machining operations is necessary for assembly purposes. Drilling is an indispensable machining operation that is frequently performed for making of holes to facilitate assembly of several components into an intricate part. In the present research endeavor, the drilling behavior of unidirectional sisal-epoxy and sisal-polypropylene composite laminates has been experimentally investigated. Chip formation characteristics in the context of both thermoset and thermoplastic natural fiber composite laminates have been discussed. Further, the analysis of drilling force signals has been reported and the mapping of drilling forces has been proposed. Influence of drill geometry, feed, and spindle speed on drilling forces and a comparative analysis of damage characteristics of drilled hole have also been reported. From the current research work, it has been established that the tooling requirement for drilling of composite laminates under investigation is substantially different.

Rotary mode ultrasonic drilling of glass fiber-reinforced epoxy laminates

The use of polymer–matrix composites in structural applications necessitates certain degree of machining operations to meet the final product integrity. Drilling is an essential machining operation being used in composite industries for making of holes for bolted joints. The conventional drilling, which is frequently used for making holes in polymer–matrix composite parts, is not convenient anymore because of plethora of challenges encountered. The major drawback is the drilling-induced damage, which mainly occurs due to the direct interaction between the tool and composite laminate. Therefore, there exists a research opportunity to develop cost-effective high-quality machining methods for composite laminates. In the present research endeavor, rotary-mode ultrasonic drilling process has been conceptualized and developed for the drilling of fiber-reinforced polymer composites. The influence of various process parameters including power rating, slurry concentration, and abrasive size on material-removal rate, tool wear rate, and average surface roughness (Ra) has been experimentally investigated. It has been observed that the entry and exit delamination is prevented, and hole circumferential edge quality is improved when holes are produced through rotary-mode ultrasonic drilling as compared to the conventional drilling. It has also been found that with substantial modification in the conventional ultrasonic drilling process, the drilling performance in terms of material-removal rate of glass-epoxy laminates can be significantly improved. The major contribution of the present research endeavor is the development of a novel method of making clean-cut damage-free holes in fiber-reinforced composite laminates.

Developments in abrasive flow machining: a review on experimental investigations using abrasive flow machining variants and media

The abrasive flow machining (AFM) technique uses a self-deforming tool, an abrasive laden media that is passed back and forth in the passage geometry of the hollow workpiece with the assistance of two hydraulically operated cylinders placed opposite to each other. The material is removed by abrasion generating finer surfaces in the area where flow is restricted. As the time advances various variants of AFM have been developed by different researchers to increase the productivity and improve the surface finish. Thus a combination of AFM and its process variants were developed to increase material removal rate and surface finish. This article provides a comprehensive review of recent developments in the process variants of AFM and the respective media.

Tool wear studies in fabrication of microchannels in ultrasonic micromachining.

Form accuracy of a machined component is one of the performance indicators of a machining process. Ultrasonic micromachining is one such process in which the form accuracy of the micromachined component significantly depends upon the form stability of tool. Unlike macromachining, a very small amount of tool wear in micromachining could lead to considerable changes in the form accuracy of the machined component. Appropriate selection of tool material is essential to overcome this problem. The present study discusses the effect of tool material, abrasive size and step feed in fabrication of microchannels by ultrasonic machining on borosilicate glass. Development of microchannels using ultrasonic micromachining were rarely reported. It was observed that tungsten carbide tool provided a better form accuracy in comparison to the microchannel machined by stainless steel tool. The tool wear mechanism in both materials is proposed by considering scanning electron micrographs of the tool as evidence. A one factor at a time approach was used to study the effect of various process parameters.

Experimental investigation and optimisation in EDM of Al 6063 SiCp metal matrix composite

Al 6063 SiCp metal matrix composite (MMC) was drilled by EDM to assess the machinability and obtain an optimal setting of process parameters. The effect of pulse-on (Ton), pulse-off (Toff), pulse current (Ip), gap control setting and flushing pressure on EDM of cast Al 6063-SiCp MMC was investigated. The machining conditions were identified for machining performance of the EDM process with respect to material removal rate (MRR) and tool wear rate (TWR) by pilot experimentation using one-factor-at-a-time approach. Taguchis technique was further applied to obtain an optimal setting of the EDM process parameters. The experimental results and subsequent analysis revealed that all the selected process parameters were significant. MRR increases with increasing Ip and Ton up to an optimal point and then drops. The effect of Ip is predominant on MRR as compared to other parameters.

Multi objective optimization in drilling of Al6063/10%SiC metal matrix composite based on grey relational analysis

A grey relational analysis is a novel technique for forecast, developing relational analysis and in decision-making in numerous areas of manufacturing or production processes in industry. In this investigation, an attempt has been made to optimize input process parameters considering assigned weight fraction of output quality characteristics using grey relational analysis. The output quality characteristics considered are thrust force, torque and surface roughness under the experimental domain of cutting speed, feed, step diameter and point angle. The drilling experiments were designed as per Taguchi design of experiments using L9 orthogonal array. The combined methodology of orthogonal array design of experiments and grey relational analysis was implemented to establish the best possible input process parameters that give minimum thrust force, torque and surface roughness. The results reveal that with the help of grey relational analysis, output quality characteristics can be enhanced efficiently.

Developments on electrochemical discharge machining: A review of experimental investigations on tool electrode process parameters

The electrochemical discharge machining is a combination of electrochemical machining and electrical discharge machining. The machining is achieved by chemical etching effect and melting of workpiece material due to electrical discharges. This process is used for a variety of nonconductive materials (glass, quartz, ceramic, Pyrex and so on) for the purpose of micromachining and specially for micro electro mechanical system applications. This article presents a comprehensive review of recent developments on tool electrode process parameters, which have resulted in enhanced efficiency and accuracy of the machining process. The tool electrode process parameters are shape, size, roughness, insulation and motion of tool and so on. These process parameters affect the process performance in terms of material removal rate, surface quality and dimensional accuracy of micromachined products. For example, spherical tool geometry provides five times higher material removal rate as compared to cylindrical tool geometry. The impact of electrochemical discharge machining process parameters associated with tool electrode is also discussed. A summary of review and proposed research directions is presented in this article.

A hybrid approach to multi-criteria optimization based on user’s preference rating

In machining, there exist different quality characteristics that define overall process quality. These quality characteristics are controlled by different input process parameters. Thus, for best possible process quality, optimization is required. The resultant quality characteristics have different weightage of preference depending upon the requirements of the individuals or group. If in a group, the individuals have conflicting interests, it becomes difficult to take decisions. In this article, a new hybrid approach for multi-criteria optimization has been proposed based on the user’s opinion/preference while defining quality characteristics. Accordingly, the new technique may be termed as ‘User’s Preference Rating’ method for optimization. The major advantage of this method is that any number of opinions of the individuals can be considered for calculating the weights. Furthermore, in this technique, it is not essential to specify relationship between all quality characteristics. The implementation of the technique has been illustrated using data during ultrasonic machining of titanium.

Parametric Evaluation on Near-Dry Electric Discharge Machining

Near-dry electric discharge machining (EDM) is an eco-friendly process. It does not produce toxic fumes and consequent health hazards. The near-dry EDM generally utilizes a mixture of two phase (liquid and air) dielectric for machining. This investigation reports the influence of four processing parameters, viz. current, flushing pressure, duty factor, and lift on three responses. The responses measured were material removal rate (MRR), tool wear rate (TWR), and surface roughness (SR). The work material chosen was high speed steel (HSS). Mathematical models have been proposed herein for evaluation of the effect of processing parameters in near-dry EDM. These models were developed using response surface methodology (RSM). The experimental results reveal that the process parameters taken into consideration were significant for MRR. The TWR was negligible in near-dry EDM. This process gives a finer surface finish with thinner recast layer even at higher discharge energies as compared to conventional EDM.

Effect of Pulse Duration on Quality Characteristics of Blind Hole Drilled in Glass by ECDM

Electrochemical discharge machining (ECDM) has proven its usefulness for micro-machining of hard, brittle, and nonconductive materials. Pulse duration is one of the most important process parameters in ECDM. The present article investigates the effect of pulse duration on aspect ratio of glass material machined by ECDM. An effective range of pulse duration was identified experimentally to achieve better control on the quality characteristics. The quality characteristics measured were machining depth, surface damage, aspect ratio, and tool wear. Results reveal that a limited range of pulse duration affects the quality characteristics leading to high aspect ratio. Further, values of process parameters for high aspect ratio of holes were identified. Effect of applied voltage on tool wear was also investigated.