K. M. Patel

Determination of an Optimum Parametric Combination Using a Surface Roughness Prediction Model for EDM of Al2O3/SiCw/TiC Ceramic Composite

Alumina has become one of the most popular ceramic materials used in wear-resistant and structural applications due to its attractive physical characteristics together with chemical inertness at elevated temperature. Its inherent brittleness and low fracture toughness make its machining difficult and consequently limit its utilization. Considerable improvement in mechanical properties of the single-phase alumina ceramic has been achieved by incorporating SiC whisker, TiC particles into Al2O3, which also allow electrical discharge machining (EDM) to fabricate components with complex geometry and widen the applications. This article presents an experimental investigation of the influence of parametric setting on machining performance during EDM of Al2O3/SiCw/TiC ceramic composite. In EDM, machining parameters determine the quality of surface produced. Second order regression model has been developed for predicting surface roughness (SR) in terms of machining parameters using the response surface methodology. The significance of machining parameters selected has been established using analysis of variance. The surface roughness prediction model has been optimized using a trust region method. This methodology helps to determine the best possible parametric setting for electrical discharge machining of ceramic composite.

Understanding the Role of Weight Percentage and Size of Silicon Carbide Particulate Reinforcement on Electro-Discharge Machining of Aluminium-Based Composites

This study investigates the feasibility of fabricating microholes in SiCp-Al composites using micro-electro-discharge machining (micro-EDM) with a rotary tube electrode. Material removal rate (MRR), electrode wear rate (EWR), and hole taper were considered as responses for the study. Machining was performed on 5 and 10 wt% SiCp-Al composites having particle size of 50 µm and 150 µm to evaluate machining characteristics. Pulse-on duration, pulse-off duration, sparking gap voltage, and servo-speed were used as input variables for EDM of SiCp-Al composites by varying the weight percentage of SiC-reinforced particles and the size of reinforcement. The experimental results indicate the weight percentage and size of the SiC in SiCp-Al metal matrix composites (MMCs) to be important parameters while machining using micro-EDM. The relative contributions of each process variable on MRR, EWR, and hole taper were found using the analysis of variance (ANOVA) technique. The experimental results reveal that servo-speed significantly affects the MRR and EWR, while pulse-on duration affected the taper.

Study on Machinabilty of Al2O3 Ceramic Composite in EDM Using Response Surface Methodology

Electric discharge machining (EDM) has been proven as an alternate process for machining complex and intricate shapes from the conductive ceramic composites. Al 2 O 3 based electrodischarge machinable Al 2 O 3 ―SiC w ―TiC ceramic composite is a potential substitute for traditional materials due to their high hardness, excellent chemical, and mechanical stability under a broad range of temperature, and high specific stiffness. The right selection of the machining condition is the most important aspect to take into consideration in the EDM. The present work correlates the inter-relationships of various EDM machining parameters, namely, discharge current, pulse-on time, duty cycle, and gap voltage on the metal removal rate (MRR), electrode wear ratio (EWR), and surface roughness using the response surface methodology (RSM) while EDM of Al 2 O 3 ―SiC w ―TiC ceramic composite. Analysis of variance is used to study the significance of process variables on MRR, EWR, and surface roughness. The experimental results reveal that discharge current, pulse-on time, and duty cycle significantly affected MRR and EWR, while discharge current and pulse-on time affected the surface roughness. The validation of developed models shows that the MRR EWR and surface roughness of EDM of Al 2 O 3 ―SiC w ―TiC ceramic can be estimated with reasonable accuracy using the second-order models. Finally, trust-region method for nonlinear minimization is used to find the optimum levels of the parameters. The surface and subsurface damage have also been assessed and characterized using scanning electron microscopy. This study reveals that EDMed material unevenness increases with discharge current and pulse-on time.

Processing issues, machining, and applications of aluminum metal matrix composites

ABSTRACT Aluminum metal matrix composites (AMMCs) used in different industries from automotive to aerospace for specific purposes. Many problems hinder the full-scale industrialization of AMMCs but the main problems include wettability, particle distribution, porosity, and chemical reaction. These problems have explicit effects on mechanical, wear, and corrosion resistance properties of the composite materials. Therefore, it is essential to cope up with these problems for better quality of AMMCs. This paper focuses on issues related to AMMCs fabrication, corrosion resistance, wear resistance, machining parameter optimization, and chip analysis of AMMCs. Literature provides a guideline to researchers about present scenario of AMMC fabrication using stir casting process. Moreover, paper presents properties and applications of AMMCs.

Welding speed effect on joint properties in air and immersed friction stir welding of AA2014

In immersed friction stir welding, the workpiece is fully immersed in the water during welding. This work illustrates the effect of welding speed on mechanical properties and microstructure. Friction stir welding joints were produced using AA2014-T6 at different welding speeds ranging from 80 to 125 mm/min with constant rotational speed of 1000 r/min in air and immersed water conditions. Results revealed that with an increase in welding speed, the tensile strength of joint increased, this is due to a reduction in heat input while using both air and immersed friction stir welding, which in turn reduces the dissolution of strengthening precipitates. Microstructure result showed that grain size decreased with an increase in welding speed due to less heat input at increased welding speed. The dissolution of strengthening precipitates weakened with an increase in welding speed in both air and immersed friction stir welding, leading to an increase in hardness value at the nugget zone. Maximum tensile strength was obtained at a welding speed of 100 mm/min in immersed friction stir welding and was around 17% higher compared with a maximum tensile strength obtained using air friction stir welding.

Investigation to study the applicability of solid lubricants in machining for clean and green manufacturing

Purpose The quality of the surface being machined and tool life are greatly affected by heat generated during machining. Abundant use of cutting fluid leads to higher production rates and a threat for environment and worker’s health. Hence, the need is to identify eco-friendly lubricants. The purpose of the current work is to investigate the effects of solid lubricants (boric acid and molybdenum disulphide) mixed with oil during turning of EN-31 using cemented carbide tools. The concentration of solid lubricants in oil is varied to analyze output parameters such as surface roughness, process temperature, power consumption and tool wear. Design/methodology/approach EN 31 steel material is machined at various cutting speeds and constant feed and depth of cut to determine the effects of dry, wet and solid lubricant assisted machining. Findings Experimental study revealed that the solid lubricants performed better while machining and therefore it may be considered as environment friendly and cost effective way of lubrication as compared to flood cooling. Research limitations/implications The work can be extended to identify the effects of solid lubricants on micro hardness and cutting force. Practical implications From the findings of the work, solid lubricants may be considered as suitable choice as compared to fluid cooling because it improves process performance without much affecting the environment and worker’s health. Originality/value So far the use of solid lubricants in machining is limited. The results of the work will be useful to explore various efficient way to apply solid lubricants.

Structural Analysis of CFRP Layered Laminate under Bi-Axial Loading

Due Due to extensive use of Carbon Fiber Reinforcement Polymer (CFRP) composite in various application such as aerospace, defence, automobile, sports etc. there is a challenge before the industry to deliver the best quality product. To improve the quality of the product there is a need for analysis to ensure the safety and dimensional stability during its application. The experimental approach can be used to ensure quality of product which requires huge amount of time and cost. To avoid this, as an alternative options analytical and numerical approach can be used for conducting analysis. In this paper, static structural analysis of the layered un-symmetric composite laminate under normal loads has been performed. Stresses and strains in every layer of the laminate has been calculated using analytical and Finite Element Analysis (FEA) models. For obtaining analytical results a MATLAB program is developed for ease of calculation of stresses and strains for any number of layers in the laminate. The MATLAB program is based on Classical Lamination Theory (CLT). FEA is performed using ANSYS APDL. The results obtained from FEA and analytical are compared and both the results are found in good agreement. The maximum difference is 0.37% at 45o layer in maximum shear stress in xy-plane.

Analyzing Hertzian contact stress developed in a double row spherical roller bearing and its effect on fatigue life

Purpose The purpose of this paper is to describe a method permitting the creation of a realistic model of spherical roller bearing with the aim of determining contact stress and fatigue life based on dynamic loading conditions. The paper also aims to recognize the effect of tolerance values on contact stress and fatigue life. Motion and load transmission in spherical roller bearing occurs within the assembly by elliptical curved contacting surfaces. The stress produced by the transmitted load would be very high because of least contacting area between these surfaces. Design/methodology/approach The paper describes a methodology to determine contact stress using analytically as well as finite element method for spherical roller bearing. The comparison for the both each approach for contact stress at different loading condition is carried out. Prediction of fatigue life based on dynamic loading conditions for bearing is also determined using finite element model. The effect on induced contact stress and fatigue life by varying tolerances on inner race dimensions have been found out. Findings The paper suggests that the maximum stress produces at the start or end of the contacting arc under static loading condition in spherical roller bearing. The analytical and finite element approach is in good agreement. The fatigue life prediction is useful for selecting loading conditions for various applications of double row spherical roller bearing. Tolerance level at inner ring raceway radius is kept high because of manufacturing constrain of complex curvature geometric shape. Research limitations/implications The present approach does not consider dynamic loading conditions for contact stress analysis. Therefore, researchers are encouraged to analyze the effect of wear, lubrication and other tribological aspects on bearing life. Originality/value The paper includes determination of contact stress and prediction of fatigue life for spherical roller bearing using analytical as well as finite element approach. The tolerance values at inner race are identified as per manufacturing constraint based on contact stress and fatigue life.

Determination of an optimum parametric combination using a tensile strength prediction model for friction stir welded AA8011 aluminium alloy

Friction stir welding is widely used for the welding of aluminium. The heat required for welding is produced using non-consumable tool. Welding input parameters play a vital role in determining the strength of joint and quality of a weld joint. In the present study, mathematical model has been developed using response surface method to predict strength of the friction stir welded AA8011 aluminium alloy. Four factors, five levels central composite design has been used to reduce the number of experimental conditions. Adequacy of the developed model has been checked by statistical tool analysis of variance and validated by Chi square test. Conformation experiments have been carried out to verify validity of the developed model. The developed mathematical model can predict the tensile strength of FSW joints. Results of the study indicate that the maximum tensile strength found in the FSW welded joint is 75% of the parent metal tensile strength. Genetic algorithm is used for the optimisation of the tensile strength. A calculator has also been developed using visual basic for calculation of tensile strength.