Rajesh Kumar Sharma

Basics and applications of rapid prototyping medical models

Purpose – This study aims to provide an overview of rapid prototyping (RP) and shows the potential of this technology in the field of medicine as reported in various journals and proceedings. This review article also reports three case studies from open literature where RP and associated technology have been successfully implemented in the medical field. Design/methodology/approach – Key publications from the past two decades have been reviewed. Findings – This study concludes that use of RP-built medical model facilitates the three-dimensional visualization of anatomical part, improves the quality of preoperative planning and assists in the selection of optimal surgical approach and prosthetic implants. Additionally, this technology makes the previously manual operations much faster, accurate and cheaper. The outcome based on literature review and three case studies strongly suggests that RP technology might become part of a standard protocol in the medical sector in the near future. Originality/value – ...

Comparative analysis of textured and grooved hydrodynamic journal bearing

Research is being focused on to find the influence of surface variations such as texturing or grooving on the bearing performances. Though, earlier it was restricted to the theoretical aspects alone, however, with the help of advance manufacturing techniques (laser surface texturing, etching, special grinding process, etc.), it has become possible to produce micro-textures or grooves on the surface of journal bearing. The objective of the present study is to numerically compare the influence of spherical texture and micro-grooving (longitudinal and transverse) on friction coefficient and average temperature of journal bearing at low and high eccentricity ratios. From the findings, it has been observed that the micro-grooving reduces the friction coefficient and average temperature is maximum in comparison with spherical texture.

THERMO-MECHANICAL PROPERTIES OF SILICON CARBIDE-FILLED CHOPPED GLASS FIBER-REINFORCED EPOXY COMPOSITES

The effect of addition of silicon carbide (SiC) filler in different weight percentages on physical properties, mechanical properties, and thermal properties of chopped glass fiber-reinforced epoxy composites has been investigated. Physical and mechanical properties, i.e., hardness, tensile strength, flexural strength, interlaminar shear strength, and impact strength, are determined with the change in filler content to notice the behavior of composite material subjected to loading. Thermo-mechanical properties of the material are measured with the help of a dynamic mechanical analyzer. The result shows that the physical and mechanical properties of SiC-filled glass fiber-reinforced epoxy composites are better than unfilled glass fiber-reinforced epoxy composites. Viscoelastic analysis for different compositions indicate that adding too much SiC content results in degradation in energy absorption capacity of the material and hence overall performance of the composites, whereas adding too much (more than 10 wt.%) SiC content increases the elastic behavior of the composite.

Thermo-Mechanical Properties and Abrasive Wear Behavior of Silicon Carbide Filled Woven Glass Fiber Composites

A study was done to determine the effect of physical, mechanical, thermal and three body abrasive wear response of Silicon Carbide (SiC) filled Glass Fiber Reinforced Epoxy (GFRE) composites. The main purpose was to study the influence of different weight percentages (wt.%) of SiC filler in addition to that of glass fiber. A three body abrasive wear analysis was conducted by varying different factors such as fiber/filler reinforcement, abrasive particle size, normal load, sliding distance and sliding velocity. An attempt was made to find out the dominant factor and the effect of each factor on specific wear rate analysis. Physical and mechanical properties, i.e. density, hardness, tensile strength, flexural strength, inter laminar shear strength and impact strength, were determined for each weight percent of filler reinforcement to determine the behavior of mechanical properties with varying SiC filler loading. Thermo – mechanical properties of the material, i.e. storage modulus, loss modulus and tan delta with temperature were measured using a Dynamic Mechanical Analyzer (DMA). The result shows the increasing / decreasing trend and critical points of each analysis. The trend and major factors responsible for reducing the specific wear rate were determined. Mechanical properties, i.e. hardness and impact strength, increase with the increase in SiC content, whereas tensile strength, flexural strength and inter laminar shear strength decrease. Worn surfaces were studied using scanning electron microscopy (SEM) to give an insight into the wear mechanisms.

Comparative investigations on three-body abrasive wear behavior of long and short glass fiber-reinforced epoxy composites

The purpose of this investigation is to determine the three-body abrasive wear behavior of long and short E-glass fiber-reinforced epoxy composites in abrasive environment, subjected to designed experimental setup. A mathematical model for damage assessment in three-body abrasion is developed and validated by a well-designed set of experiments. The design of experiment using Taguchi’s orthogonal array is applied to find out minimum specific wear rate. Steady state condition is also applied to find minimum specific wear rate for particular weight fraction keeping other parameters as constant. The experimental results show that the abrasive wear of the composites shows dependence on parameters like applied load, sliding speed, and abrasive particle size. Wear rate of long as well as short glass fiber-reinforced epoxy composites increases with increase in normal load and abrasive particle size, whereas the wear rate decreases up to 40 wt.% of fiber loading and then further increases with increase in sliding speed. The SEM micrograph studies reveal the dynamics of three-body abrasive wear and underlying micro-mechanisms that serve as determinant for wear performance of such composites. The three-body abrasive wear rate in given formulation increases with normal load and abrasive particle size. The mechanical characteristics observed a positive trend with the increase in fiber composition and also help in analyzing the specific wear rate of composites.

Studies on the influence of surface texture on the performance of hydrodynamic journal bearing using power law model

The present study investigates the combined influence of surface texture, using sinusoidal, positive full and half wave roughness (transverse and longitudinal roughness) and non-Newtonian lubricants, obeying power law model on finite journal bearing. The modified Reynolds equation is solved numerically through finite difference approach for analysis of texture and non-Newtonian effects on bearing performance characteristics. It is concluded that the load carrying capacity and friction force is increased with shear thickening fluids in both bearings (smooth and rough bearings). It is also concluded that out of three roughnesses, the transverse positive full wave roughness is best for increasing the load carrying capacity and friction force, whereas the longitudinal sinusoidal roughness is best for decreasing the friction force.

Influence of Solution Temperature on Microstructure and Mechanical Properties of Two Cast Al–Si Alloys

ABSTRACT In the present paper the influence of solution temperature 450–550°C on microstructure and mechanical properties of cast Al-12%-0.3% Mg and Al-16%-0.3% Mg alloys has been reported. It was observed that an increase in solution temperature increased the tensile strength of all alloys under investigation. Ductility was adversely affected. Higher solution temperature produced better refinement and distribution of eutectic silicon crystals than a low temperature. Heat treatment of all alloys showed spheroidization of eutectic silicon crystals. Scanning electron microscopy (SEM) of tensile-fractured surfaces was carried out to investigate the influence of solution temperature on the mode of fracture.

Optimization for Turning of Al-6061-SiC-Gr Hybrid Nanocomposites Using Response Surface Methodologies

Metal matrix composites have cemented their applicability in industrial sector by virtue of their excellent mechanical properties. However, work has largely been done on the studies related to macro/microsize particles. This work has been aimed to evaluate the influence of input parameters in turning of Al-6061-SiC-Gr hybrid nanocomposites. This article evaluates the effect of process parameters on the cutting force and average roughness of the machined surface in turning of Al-6061-SiC-Gr nanocomposites. The experiments were designed using CCD, and cutting force and roughness were evaluated using response surface methodology. Statistical models were generated. The results of the study indicated that feed rate and depth of cut are the major influencing factors in descending order for the cutting force. The analysis of surface roughness revealed that both these factors are having identical effect. The cutting speed had little effect on cutting force and an improvement is seen in surface finish. The experiments also revealed that tool wear is negligible for nanocomposites. The software-predicted values and the experimentally obtained values of the responses were acceptably close to each other with an error percentage of less than 5%. Using response surface optimization, optimal combinations of machining parameters are also obtained.

Stagnation Point Flow of a Micropolar Fluid over a Stretching/Shrinking Sheet with Second-Order Velocity Slip

AbstractThe steady stagnation point flow of a micropolar fluid over a stretching/shrinking sheet with second-order velocity slip is studied. Similarity equations are obtained using similarity transformation, which are then solved numerically using MATLAB routine boundary value problem solver (bvp4c) based on the finite-difference method. Numerical results show that dual solutions exist for a certain range of the shrinking parameter. The dual solutions for velocity and microrotation distribution with first-order, second-order velocity slip parameter and micropolar parameter are shown graphically. It is observed that the range of the stretching/shrinking parameter for which the solution exists increases with the increase of the first-order slip parameter and micropolar parameter, whereas it decreases with the increase of the second-order slip parameter. The linear stability analysis of the obtained results was performed to show that the first solution branch is linearly stable, whereas the other is always u...

Study on shrinkage behaviour of laser sintered PA 3200GF specimens using RSM and ANN

Purpose The purpose of this paper is to provide a better understanding of process parameters that have a significant effect on the shrinkage behaviour of laser-sintered PA 3200GF specimens. Design/methodology/approach A five-factor, three-level and face-centred central composite design was used to collect data, and two methods, namely, response surface methodology (RSM) and artificial neural network (ANN) were used for predicting shrinkage. Sensitivity analysis based on the developed empirical equations has been carried out to determine the most significant parameter, which contributes the most to control shrinkage. In addition, a comparative analysis has also been performed for the results obtained by RSM and ANN. Findings The results revealed that part bed temperature, scan speed and scan spacing are the three dominant parameters, which have a great influence on shrinkage. Strong interactions between laser power-scan spacing, laser power-scan length and scan speed-scan spacing have been observed. Through sensitive analysis, it is observed that shrinkage is more sensitive to the scan speed variations than other four process parameters. Practical implications This study can be used as a guide, and the demonstrated results will provide a good technical database to the different additive manufacturing users of various industries such as automobile, aerospace and medical. Originality/value To the best of the authors’ knowledge, this is the first study to report the shrinkage behaviour of laser-sintered PA 3200GF parts fabricated under different sintering conditions.