Percentage Contribution Ratios Research Articles

تأثيرعوامل التشغيل الميكانيكي على تآكل آداة القطع وشكل الرقاقة عند عملية الخراطة الجافة لسبيكة الألومنيوم 6060 باستخدام آدوات قطع كربيدية مختلفة الأبعاد

This study presents an experimental investigation of tool wear and chip shape after turning 6060 aluminium alloy using wiper and conventional cutting tools under dry cutting conditions. The influence of parameters such as cutting speed, feed rate, depth of cut, and tool type on tool wear and chip shape were examined. A Taguchi L9 orthogonal array was employed to optimise the cutting parameter, and the effect of each parameter on tool wear was determined using analysis of means (ANOM) and analysis of variance (ANOVA). It was found that a combination of a cutting speed of 1000 rpm, feed rate at 0.1 mm/rev, and depth of cut of 0.5 mm achieved minimal tool wear when dry turning 6060 aluminium alloy using wiper tools. Also, the ANOVA indicated that the main factor contributing to lower tool wear was cutting speed followed by feed rate, with percentage contribution ratios (PCRs) of 54.75% and 37.67% respectively. This confirms that the relationship between cutting speed and tool wear is proportional. Additionally, the ANOVA results demonstrated that the depth of cut, and tool type had little impact on tool wear. Although the wiper and conventional tools are made of similar material with different nose geometries, the wiper insert showed limited abrasion at the higher cutting speed compared to the conventional one. All turning tests produced long irregular continuous curled chips at the beginning of the cutting process, which then changed from the curled to a string-like shape wrapped around the insert tip and the machined part at the end of the turning process. Meanwhile, all the cutting parameters were found to have only a minor impact on chip shape when dry turning 6060 aluminium alloy. Keywords: Dry turning, 6060 aluminium alloy, wiper and conventional coated carbide tools, tool wear, chip shape.

The Machinability Characteristics of Multidirectional CFRP Composites Using High-Performance Wire EDM Electrodes

Due to the abrasive nature of the material, the conventional machining of CFRP composites is typically characterised by high mechanical forces and poor tool life, which can have a detrimental effect on workpiece surface quality, mechanical properties, dimensional accuracy, and, ultimately, functional performance. The present paper details an experimental investigation to assess the feasibility of wire electrical discharge machining (WEDM) as an alternative for cutting multidirectional CFRP composite laminates using high-performance wire electrodes. A full factorial experimental array comprising a total of 8 tests was employed to evaluate the effect of varying ignition current (3 and 5 A), pulse-off time (8 and 10 µs), and wire type (Topas Plus D and Compeed) on material removal rate (MRR), kerf width, workpiece surface roughness, and surface damage. The Compeed wire achieved a lower MRR of up to ~40% compared with the Topas wire when operating at comparable cutting parameters, despite having a higher electrical conductivity. Statistical investigation involving analysis of variance (ANOVA) showed that the pulse-off time was the only significant factor impacting the material removal rate, with a percentage contribution ratio of 67.76%. In terms of cut accuracy and surface quality, machining with the Compeed wire resulted in marginally wider kerfs (~8%) and a higher workpiece surface roughness (~11%) compared to the Topas wire, with maximum recorded values of 374.38 µm and 27.53 µm Sa, respectively. Micrographs from scanning electron microscopy revealed the presence of considerable fibre fragments, voids, and adhered re-solidified matrix material on the machined surfaces, which was likely due to the thermal nature of the WEDM process. The research demonstrated the viability of WEDM for cutting relatively thick (9 mm) multidirectional CFRP laminates without the need for employing conductive assistive electrodes. The advanced coated wire electrodes used in combination with higher ignition current and lower pulse-off time levels resulted in an increased MRR of up to ~15 mm3/min.

Finite Element Modelling of Cutting Forces and Power Consumption in Turning of AISI 420 Martensitic Stainless Steel

Martensitic stainless steels have high hardenability, good strength and good corrosion resistance; however, high power consumption is encountered in machining operations due to their hard machinability. The consumption should be eliminated for cleaner production in terms of sustainable machining. Therefore, this study aims modelling of cutting forces and power consumption in turning of AISI 420 martensitic stainless steel based on finite element method. Finite element modelling of cutting forces is preferred to estimate optimum cutting parameters for less power consumption. In this regard, finite element simulations are performed based on three different levels as cutting speed, depth of cut and feed rate. Depth of cut could be assessed as the most important factor with percentage contribution ratio of 49.55% in respect of the power consumption. The average of 7% difference is achieved between experimental and simulated cutting forces. The deviation of 4.5% is evaluated between experimental results and simulation outputs by means of comparing the power consumption. The finite element modelling of cutting forces and power consumption is quite compatible with the experimental results, and it can be performed by high accuracy without excessive machining experiments of difficult-to-cut materials.

A feasibility study on wire electrical discharge machining of carbon fibre reinforced plastic composites

This paper details preliminary experimental work to investigate the wire electrical discharge machining (WEDM) of unidirectional carbon fibre reinforced plastic (CFRP) composites using a high tensile strength zinc rich coated brass wire (0.25 mm diameter). A fractional factorial L18 Taguchi experimental design was employed to evaluate the influence of varying open gap voltage (120 and 140 V), ignition current (3 – 5 A) as well as pulse on-time (0.8 – 1 µs) and off-time (4 – 8 µs) on material removal rate (MRR), top (Wt) and bottom (Wb) kerf widths as well as workpiece edge damage. The ignition current and pulse off-time were found to be statistically significant factors affecting MRR based on an analysis of variance, with percentage contribution ratios (PCR) of 48.5% and 24.3% respectively. It was observed that MRR, which ranged between 0.43 and 2.41 mm3/min, increased with both ignition current and pulse on-time due to the higher discharge energy generated in the machining gap. No signs of workpiece damage in terms of delamination or surface burning was apparent, despite the higher MRR. Conversely, the larger open gap voltage surprisingly led to reductions in MRR, which was likely due to unstable gap conditions caused by greater levels of residual melted resin within the gap or re-deposition on the workpiece surface. In terms of kerf width, ignition current was revealed as the sole significant factor with respect to the top surface (up to ~ 0.28 mm) having a PCR of 56.6%, while none of the variable parameters had a major effect on the bottom kerf width.

An investigation on deformation behaviors of energy absorbers for passenger coaches

Thin-walled structures is used commonly as energy absorbers at the front and back of the coaches. These parts should be designed to minimize the damage to the vehicle and prevent the passengers from fatality and/or injury by absorbing the collision energy in railway transportation. In this paper, deformation behaviors of tube like structures with truncated cone under the axial impact load were investigated by means of finite element analysis (FEA). The energy absorbers having tube like structures were modelled at the same weight and have three different wall thickness and taper angle. As a result of FEA, the performances of straight and truncated cone type energy absorbers were compared in terms of energy absorption capacities and an optimization study was done to determine the effects of thickness and taper angle on energy absorbing performances of the members. The analysis of variance in 95% confidence level was applied in order to determine the effects of design parameters on total efficiency (TE). Besides, optimum design parameters for TE were determined by using Taguchi optimization methodology. Thickness was found as the most significant parameter on total efficiency with 60.52% percentage contribution ratio according to ANOVA results.

An Investigation into the Dependency of Cutting Forces on the Volume Fraction and Fibre Orientation during Machining Composite Materials

This paper presents an empirical force model quantifying the effect of fibre volume fraction and fibre orientation on the cutting forces during orthogonal cutting of unidirectional composites. Glass fibre plates and high speed steel cutting tools are used to perform orthogonal cutting on shaping machine whereas cutting forces are measured using platform force dynamometer. The analysis of forces shows almost linear dependency of cutting forces on the fibre content for both cutting and thrust forces. High dependency of cutting forces is also observed on fibre orientation with high percentage contribution ratio (up to 95.31%). Lowest forces corresponded to 30o and highest to 90o fibre orientation. Multivariate regression technique is used to construct the empirical model.

Characteristics of Machining Parameters on WEDM Titanium Alloy

Wire electrical discharge machining is a material removal process of electrically conductive materials by the thermo-electric source of energy. This kind of machining extensively used in machining of materials with highly precision productivity. This work presents the machining of titanium alloy (TI-6AL-4V) using wire electro-discharge machining with brass wire diameter 0.5mm.The objective of this work is to study the influence of three machining parameters namely peak current, pulse off time and wire tension to cutting rate, material removal rate, surface roughness and kerf width followed by suggesting the best operating parameters towards good machining characteristics. A full factorial experimental design was used with variation of peak current, feed rate and wire tension, with results evaluated using analysis of variance techniques. Parameter levels were chosen based on best practice and results from preliminary testing. Main effects plots and percentage contribution ratios are included for the main factors and their interactions.

The morphology and distribution of CD1a positive Langerhans cells in normal and squamous cell carcinoma of cervix

Power consumed in metal cutting is typically converted into heat near the cutting tool edge. Cutting fluids are then provided to a cutting zone in order to improve the tribological characteristics of machining processes and to dissipate the generated heat. The use of conventional cutting fluids however has lately been questioned due to the adverse impact on the environment and human health. Therefore, trends are directed to various alternatives such as vegetable oils (VOs). VOs offer a combination of good biodegradability and high lubricity, eco-friendly and compatibility with additives, low toxicity and volatility, high flash points and high viscosity indices. This paper details preliminary experimental results when turning Ti-6Al-4 V. The impact of VO-based cutting fluids, cutting tool materials and working conditions were investigated. Two sets of experimental plans were designed comprising 25 and 27 tests with analysis of variance (ANOVA) employed to evaluate the effect of process variables on Ra and tool flank wear. In general, surface roughness Ra ranged between 0.56 μm and 1.81 μm and statistical analysis showed that the main contributing factor for Ra is feed rate having a high Percentage Contribution Ratio (PCR) of 94.4%. Noticeable increase in tool tip flank wear was recorded when higher cutting speeds were used.

Optimisation of Dry Electrical Discharge Machining of High Speed Steel using Grey-Relational Analysis

Dry electrical discharge machining (DEDM) is considered as a green format of the conventional oil dielectric EDM where a gas is used as the dielectric medium. This paper details experimental results when DEDM of high speed steel workpieces using multi-response optimisation. Experimental trials were performed to investigate the influence of current, pulse on-time, duty factor, gas pressure and spindle rotational speed on material removal rate (MRR), surface roughness (Ra) and radial over cut (ROC). Grey relational analysis (GRA) based on Taguchi approach was employed for multi-objective optimisation of DEDM responses. Confirmation trials were subsequently conducted and results showed that process responses can be successfully optimised using GRA. Results showed that current, duty factor and air pressure were found to be statistically significant factors at 90% confidence level, with percentage contribution ratios (PCRs) of 72.8%, 4.3% and 3.7% respectively. Micro pores and minor surface cracks were visible in the majority of specimens.

Properties of polypropylene fiber reinforced concrete using recycled aggregates

In this study, recycling of rubble obtained during urban transformation and manufacturing new concrete using this material was experimentally studied. Different combinations were generated using the recycled concrete aggregates and polypropylene fiber. Natural aggregates were replaced by recycled concrete aggregates (RCAs) and volume of 0%, 1% and 1.5% fiber were introduced for each series. Although concretes’ physical and mechanical properties were affected negatively by RCA due to RCA’s higher porosity and water absorption capacity, high strength concrete was eventually manufactured. Additionally, although fiber content increases flexural properties, there is no significant difference observed between 1% and 1.5%. Percentage contribution ratios of parameters which influence the results of experiments were also calculated by means of analysis of variance (ANOVA) method. As the result of ANOVA which is carried out on specimens containing fiber and recycled concrete aggregate, main factor on changes of compressive strength were determined as aggregate type, while fiber content were also influential on flexural and splitting tensile strength besides aggregate type.

Investigation of Cutting Tools and Working Conditions Effects when Cutting Ti-6al-4V using Vegetable Oil-Based Cutting Fluids

Power consumed in metal cutting is typically converted into heat near the cutting tool edge. Cutting fluids are then provided to a cutting zone in order to improve the tribological characteristics of machining processes and to dissipate the generated heat. The use of conventional cutting fluids however has lately been questioned due to the adverse impact on the environment and human health. Therefore, trends are directed to various alternatives such as vegetable oils (VOs). VOs offer a combination of good biodegradability and high lubricity, eco-friendly and compatibility with additives, low toxicity and volatility, high flash points and high viscosity indices. This paper details preliminary experimental results when turning Ti-6Al-4V. The impact of VO-based cutting fluids, cutting tool materials and working conditions were investigated. Two sets of experimental plans were designed comprising 25 and 27 tests with analysis of variance (ANOVA) employed to evaluate the effect of process variables on Ra and tool flank wear. In general, surface roughness Ra ranged between 0.56μm and 1.81μm and statistical analysis showed that the main contributing factor for Ra is feed rate having a high Percentage Contribution Ratio (PCR) of 94.4%. Noticeable increase in tool tip flank wear was recorded when higher cutting speeds were used.

Modeling and Influence of Machining Parameters on Titanium Aloy

Wire electrical discharge machining (WEDM) is a material removal process of electrically conductive materials by the thermo-electric source of energy which is extensively used in machining of materials for a highly precision productivity. This work presents the machining of titanium alloy (TI-6AL-4V) using WEDM with a brass wire diameter of 0.25mm.The objective of this work is to study the influence of three machining parameters, namely peak current (IP), feed rate (FC) and wire tension (WT) to cutting speed and surface roughness as a responses. Response Surface Methodology was used to develop second order model in order to predict cutting speed and surface roughness responses. The results showed that the average percentage error between the predicted and experimental value for both models was less than 2%. Effects of each parameter and their interaction with percentage contribution ratios (PCR) are included for each response.

High-speed ball nose end milling of burn-resistant titanium (BuRTi) alloy

Following a brief introduction to aero-engine materials and the development of BuRTi alloy (Ti-25V-15Cr-2Al-0.2C), the paper details a statistically designed machinability experiment involving high-speed ball end milling. Testing utilised 8 mm diameter AlTiN-coated carbide ball nose end mills in a Taguchi L8 fractional factorial design with six factors, each at two levels. Output measures related to tool life/wear, cutting forces, workpiece surface roughness, microstructure and microhardness. Main effect plots, tabulated ANOVA data, percentage contribution ratio (PCR) values together with graphical and SEM data are presented. Use of the lowest material removal rate, high-pressure (70 bar) cutting fluid and a workpiece orientation of 45° resulted in the longest tool life with a machining time of ~60 min; however, surface roughness was poor, and there was smeared/adhered material to a depth of 20 μm. Additionally, carbide fracture/pull-out was observed near the workpiece surfaces whereas microhardness depth profiles from sectioned, mounted and polished samples showed a moderate increase in surface hardness of ~80HK0.25 above the bulk value.

Influence of Machining Parameters on Surface Roughness in WEDM Titanium Alloy

Wire electrical discharge machining (WEDM) is a material removal process of electrically conductive materials by the thermo-electric source of energy .This kind of machining extensively used in machining of materials with highly precision productivity. This work presents the machining of titanium alloy (TI-6AL-4V) using wire electro-discharge machining with brass wire diameter 0.25mm.The objective of this work is to study the influence of three machining parameters namely peak current (IP), feed rate (FC) and wire tension (WT) to material removal rate and surface roughness followed by suggesting the best operating parameters towards good surface finish. A full factorial experimental design was used with variation of peak current, feed rate and wire tension, with results evaluated using analysis of variance (ANOVA) techniques. Parameter levels were chosen based on best practice and results from preliminary testing. Main effects plots and percentage contribution ratios (PCR) are included for the main factors and their interactions. Peak current was shown to have the greatest effect on surface roughness (33% PCR).

Micro-Milling of Hardened AISI D2 Tool Steel

The paper presents an experimental investigation into the slotting of hardened AISI D2 (~62HRC) tool steel using 0.5mm diameter coated (TiAlN) tungsten carbide (WC) end mills. SEM analysis of tool morphology and coating integrity was undertaken on all tools prior to testing. Tool wear details are given based on resulting cutter diameter and slot width reduction. In addition, cutting forces are also presented together with details of workpiece burr formation. A full factorial experimental design was used with variation of cutting speed, feed rate and depth of cut, with results evaluated using analysis of variance (ANOVA) techniques. Parameter levels were chosen based on microscale milling best practice and results from preliminary testing. Main effects plots and percentage contribution ratios (PCR) are included for the main factors. Cutting speed was shown to have the greatest effect on tool wear (33% PCR). When operating at 50m/min cutting speed with a feed rate of 8µm/rev and a depth of cut of 55µm, cutter diameter showed a reduction of up to 82µm for a 520mm cut length. SEM micrographs of tool wear highlighted chipping / fracture as the primary wear mode with adhered workpiece material causing further attritious wear when machining was continued up to 2.6m cut length. All tests produced burrs on the top edges of the slots which varied in size / width to a lesser or greater degree. Under the most severe operating conditions, burr width varied from approximately 50µm to more than 220µm over the 520mm cut length. Cutting forces in general were less than 12N up to test cessation.

Taguchi techniques‐based study on the effect of mobile phone conversation on drivers' reaction time

PurposeThe purpose of this paper is to demonstrate application of the Taguchi method‐based conceptual signal‐to‐noise (S/N) approach and Pareto analysis of variance (ANOVA) to determine optimum level of three important factors related to mobile phone conversation during driving, namely time of drive (day or night), distance between cars, and mobile phone call duration that minimizes drivers' reaction time (RT) in braking response.Design/methodology/approachThree levels of each factor based on the experience, are considered in the present study. The design of experiment, in the form of an L18 orthogonal array, as proposed by Genichi Taguchi is used to conduct 18 experiments. A total of 27 young male subjects participated in the experimental study. The experimental task involved pressing the brake pedal of the car by the driver upon seeing another car in front while the driver is talking on a mobile phone. Drivers' performance, measured in terms of RT in braking response, is recorded. Conceptual S/N ratio and Pareto ANOVA are employed to investigate the drivers' performance.FindingsResults show that within the test range, drivers' performance, i.e. RT in braking response is optimum (minimum) when they performed the driving task at day time, distance between cars is long (20 meters), and mobile phone call duration is short (30 seconds). Mobile call duration is found to be the dominant parameter with a percentage contribution ratio of 41.882 percent towards the laid down objective followed by time of driving, 32.003 percent and distance between cars, 1.353 percent.Practical implicationsThis paper provides valuable information to the drivers with respect to the use of optimum level of these factors in order to minimize their RT in braking response.Originality/valueTo the best of the authors' knowledge, no study has been conducted in the past to investigate the effect of these factors on the performance of drivers when they use mobile phones for conversation during driving. In addition, no attempt has yet been made to find the optimal level of these factors from drivers' performance in braking response view point. This paper is an original research work of authors and in the opinion it carries significantly important values as it provides new information to the persons who talk on mobile phones during driving.

Drill geometry and operating effects when cutting small diameter holes in CFRP

The paper details experimental results when drilling small holes (1.5 mm diameter cemented carbide drills with varying end point and helix geometry) in thin quasi-isotropic, unbacked carbon fibre reinforced plastic (CFRP) laminate (typical cutting time ∼0.4 s/hole). The study utilised an L12 Taguchi fractional factorial orthogonal array with analysis of variance (ANOVA) employed to evaluate the effect of drill geometry and drilling conditions on tool life and hole quality. Main effects plots and percentage contribution ratios (PCR) are detailed in respect of response variables and process control factors. More conventionally, tool wear and cutting force data are plotted/tabulated, together with micrographs of hole entry/exit condition and internal hole damage. Drill geometry and feed rate in general had the most effect on measured outputs. Thrust force was typically below 100 N at test cessation; however, drill wear progression effectively doubled the magnitude of force from test outset. Entry and exit delamination factors ( F d) of ∼1.3 were achieved while the maximum number of drilled holes for a tool life criterion VB Bmax of ≤100 μm was 2900 holes using a stepped, uncoated drill with a feed rate of 0.2 mm/rev.

Workpiece surface modification using electrical discharge machining

Electrical discharge machining (EDM) is a widely used process in the mould / die and aerospace industries. Following a brief summary of the process, the paper reviews published work on the deliberate surface alloying of various workpiece materials using EDM. Details are given of operations involving powder metallurgy (PM) tool electrodes and the use of powders suspended in the dielectric fluid, typically aluminium, nickel, titanium, etc. Following this, experimental results are presented on the surface alloying of AISI H13 hot work tool steel during a die sink operation using partially sintered WC / Co electrodes operating in a hydrocarbon oil dielectric. An L8 fractional factorial Taguchi experiment was used to identify the effect of key operating factors on output measures (electrode wear, workpiece surface hardness, etc.). With respect to microhardness, the percentage contribution ratios (PCR) for peak current, electrode polarity and pulse on time were ~24, 20 and 19%, respectively. Typically, changes in surface metallurgy were measured up to a depth of ~30 μm (with a higher than normal voltage of ~270 V) and an increase in the surface hardness of the recast layer from ~620 HK 0.025 up to ~1350 HK 0.025.