Applied Mechanics and Materials Vols. 592-594

Abstract: In recent years investigation of torsional vibration characteristics of the shaft systems transmitting torque, has become important part of the designer’s responsibility. Satisfactory operation of heavy duty transmission system may depend to a large extent upon the successful handling of the vibration problem. Propeller shaft of most of the vehicles are found to show number of modes of failures. Most destructive failure after thorough study of the system involving Propeller shaft is rupture of tubes & excessive bending caused due to torsional shear stresses that get imposed during running time of propeller shaft. Based upon above problem, new methodology has been devised to come up with new technique for determination of torsional stresses across cross sections of the shafts. TATA LP/LPO 1510 model chosen for the propeller shaft analysis and data provided by M.S.R.T.C. workshop bhandara (M.S.). Frequency response analysis (FRA) that has been worked out in found to show number of failures modes, each mode being representation of operation speed which is equal to excited natural frequency. Predicted frequency range is having excellent with practical results. Stresses that are obtained are of low magnitude (torsional stresses) but effect of this low modal amplitude will be excessive bending of shaft which causes the bending stresses of 72 N/mm2 while permissible is 83.7 N/mm2.

Abstract: Diamond-like-carbon (DLC) coatings provide excellent surface properties on substrate. With novel advanced techniques like modeling and simulation, the performance of these coatings can be predicted under different loading condition. Aim of present study was to developed three dimensional models for calculating first principal stress distribution components in the scratch test contact as the spherical diamond tip is moving with increasing load on a DLC Coated high speed steel substrate. Two different types of coatings (DLC 2, DLC 6) were used and find out the stress distribution on coatings and substrate. The models were developed in HYPERMESH and analyzed in RADIOSS software. The model is comprehensive in the sense that it considers elastic, plastic and fracture behavior of the coating surfaces.

Abstract: An attempt has been made in this research work to develop strong and tough bainitic steels in shorter transformation durations of less than three hours leading to ease of production for steel industries making these steels. High carbon medium alloy steel with high amounts of silicon, cobalt and aluminum was taken up for this study. The steel samples were austempered at 473, 523, 573, and 623K for 30, 45, 60, 90, 120, 150, and 180 minutes and then characterized by optical metallography, scanning electron microscopy, transmission electron microscopy and X-ray diffraction investigations. Microstructure containing plates of bainitic ferrite and substantial amounts of retained austenite placed in between the bainitic ferrite laths was produced. The steel after austempering had hardness in the range 450 – 720 HV at 30 kg load, tensile strength of about 560-620 MPa and room temperature notch impact toughness of about 10J with very less ductility. The details of alloy design and making, metallurgical and mechanical characterizations are discussed.

Abstract: : Optimization is the art of obtaining the best results under given circumstances. In design, construction and maintenance of any engineering system, the ultimate goal is either to minimize the effort required or to maximize the desired benefits. The various processes of optimization come under the subject Operation Research (O.R.). O.R. one of the branch of mathematics which is concerned which the application of scientific methods and techniques to design making problems and establishing optimal situations. In this project we aim to find the optimum design of a hydrodynamics bearing through operations research techniques. The two methods used are stochastic programming and geometric programming. The existing design procedure treats design variables as deterministic ones. In actual practice due to manufacturing tolerances etc. design variables do not remain deterministic but become probabilistic. The probabilistic nature of these should be given proper consideration while designing. This project deals with an approach which takes into account the probabilistic nature of designs variables, as well as probability of satisfying constraint equations. Stochastic signomial geometric programming has been used for optimization.

Abstract: In the present work, a comparative study on the wear behavior of cast aged and forge aged A356 alloy has been investigated without and with the addition of grain refiner and modifier, under dry sliding conditions using a pin-on-disc wear testing machine. The comparison study reveals that tribological properties of A356 materials are highly influenced by T6 heat treatment process. It is found in the present study that, cast aged A356 materials possess higher wear resistance as compared to forge aged materials. Apart from this, the study also reveals that cast aged material is associated with lower frictional forces and coefficient of friction as compared to the forge aged category. It is further observed in the present investigation that abrasive wear mechanism is operative in both the categories of the materials when tested with lower load for lower sliding speed and lower distance of run. At higher values of external parameters the adhesive wear mechanism dominates the wear process. Lower values of wear properties recorded by the forge aged material are an unexpected result in the present studies. It is conceived to be due to the presence of micro cracks while forging.

Abstract: In this work, abrasive wear performance of multi-walled carbon nanotube (CNT) reinforced polypropylene (PP) has been studied. Various weight percentage of CNT/PP nanocomposites were prepared through melt intercalation with the aid of twin screw extruder. Prepared composites were subjected to sliding wear against silicon carbide abrasive paper with the aid of pin-on-disc configuration. Worn out surface morphology were observed under microscope and non-contact profilometer to understand the wear mechanism. Since the dominant friction mechanism observed to be is ploughing, no lubrication effect of CNT was observed. CNT/PP composite exhibits inferior wear resistance than unfilled PP due to its brittleness. With increased CNT, wear resistance found to decreases.

Abstract: In recent years, Al6061-carbon fiber composites are gaining wide spread popularity as they find scope in certain high-tech applications such as automobile, aerospace, transport, andprocessing industries. Thesecomposites possess high strength to weight ratio, excellent wear resistance in addition to superior mechanical properties. The experimental method of determining wear phenomenon of the developed composites is an expensive as well as a tedious process.As such engineers and scientists are focusing their attention towards developing mathematical modelsfor determining wear phenomenon. The use of mathematical modeling for prediction of wear phenomenon is an evolving research area. Hence, meager information is available as regards the mathematical model to determine wear rate of composites. Mathematical modeling is slowly gaining impetus in industries in order to assess the life of sliding components and establishing the economic loss incurred due to the wear phenomenon. In the light of the above, Al6061 carbon fiber composites were prepared by liquid metallurgical route and then machined to a standard size of pin.On the pins, sliding wear test was conducted on a pin-on-disc apparatus using C-45 steel disc as per ASTM Standard. Data generated was then used in developing AdaptiveNeuro Fuzzy Inference System (ANFIS). The ANFIS logic was created using the fuzzy logic tool box of Matlab 7.10 Version. For simulating, actual working conditions used to establish the sliding wear behaviour of Al6061-xwt%Carbon fiber composites (x=5, 10) including variable parameters such as Varying load (from 10-60N in step of 10N), Sliding distance, Weight fraction (5-10%) keeping other parameters constant such as track diameter 20 mm, Speed 500rpm and Pin diameter 8 mm were used.The adopted fuzzy model employs hybrid learning techniques for updating the premise and consequent parameter. The predicted values of sliding wear rate of Al6061-xwt% carbon fiber are in close agreement with the experimental results.

Abstract: This works presents a study on anti friction properties, of fully formulated SAE 20W 40 grade motor oil dispersed with surface modified WS₂ and MoS₂ nanoparticles. WS₂ and MoS₂ particles of 0.05 wt. % and 0.1 wt. % have been dispersed in SAE 20W 40 motor oil by Sonication and tested for tribological behavior on pin on disc apparatus as per ASTM G99 standards. The friction coefficient values for base oil and oil dispersed with WS₂ and MoS₂ nanoparticles have been evaluated and compared to obtain the performance analysis. Performance graphs have plotted for the base oil and oil dispersed with nanoparticles for comparison. The oils with dispersed nanoparticles have shown enhanced performance in comparison to the base oils in terms of anti friction properties.

Abstract: Nylon 66 is an engineering thermoplastic which has been found to be a suitable alternative material for metal parts in low and medium load bearing applications. Particulate filled polymer composites are preferred in this kind of tribological environment, because of their enhanced wear resistance properties. Fly ash and silica fume are industrial wastes which are now looked as potential fillers to enhance the material properties at low cost. Nylon 66 was reinforced with these filler materials at 15% weight fraction using a twin-screw extruder. The specimens were prepared using an injection molding machine of 60 ton capacity. The tests were carried out under dry sliding conditions in a pin-on-disc type friction and wear monitoring test rig. The tests were conducted at various sliding velocities of 2 m/s, 3 m/s and 4 m/s, at three different normal loads of 20 N, 40 N, 60 N and at a constant sliding distance of 5000 m. SEM observations were made to study the wear mechanisms in the composites. Both types of composites showed enhanced wear properties compared to neat Nylon but fly ash filled Nylon composites were superior to silica fumed filled Nylon composites.

Abstract: The aim of the work was to investigate the wear properties of basalt short fiber reinforced aluminum Metal Matrix Composites (MMCs) using pin-on-disc wear test rig. The Al/basalt MMCs contains basalt short fiber from 2.5 to 10 % in steps of 2.5 wt. % and fabricated using compocasting technique. The influences of the content of basalt short fiber, wear load, sliding distance, sliding velocity and mode of worn-out surface were discussed. The results indicated that Al/basalt short fiber composite had better wear resistance than that of the matrix alloy and it decreases with wt. % of basalt short fiber content. In other direction wear rate of both unreinforced alloy and reinforced composites increased with increasing in wear load and the sliding speed. Surfaces before and after wear tests were characterized using scanning electron microscopy (SEM). Keywords: Metal matrix composite (MMCs), Basalt fibers, sliding wear, wear rate