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ThesisItem Open Access Effect of stress ratio on fatigue crack growth behaviour of friction stir welding between AA6061 and AA7075 alloys(G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2019-09) Kandwal, Abhishek; Gope, P.C.In the present work, fatigue crack growth in friction stir welded dissimilar AA6061 and AA7075 is performed under different stress ratio and maximum load condition. Crack is a damage that often occurs in members of structures and may cause sudden serious failure of the structures. In a structure generally weld is the weakest section and therefore more prone to failure due to crack propagation. Therefore the study of mechanism of crack growth and its parameters is of paramount importance. The effects of presence of crack on fracture parameters like crack opening stress (Sop) and stress intensity factor (K) of specimen has been the subject of various investigations. However, the parametric studies like effect of stress ratio and amplitude; on the fracture parameters of specimen for friction stir welded joints has gaps in the literature and therefore needs further investigation. Aluminium alloys AA6061 and AA7075 have been chosen for the present study as they are both used in conjunction in many areas of engineering such as marine and aircraft structures. The crack growth rate data for the weld shows that with the increase in stress ratio, fatigue life of the joint decreases. The fatigue life obtained for constant maximum load and varying stress ratio condition shows that the highest Fatigue life is obtained for stress ratio R= -0.5 (48200 cycles) and lowest for R=0.8 (22200 cycles). The curve obtained using Newman equations is closer to plain strain condition. For the constant stress ratio and varying maximum load, it was observed that the fatigue life of joint decreases with the increase in applied maximum load (Pmax) with the highest fatigue life observed for Pmax=4kN (28908 cycles) and lowest for Pmax=6kN (21635 cycles).ThesisItem Open Access Effects of randomly oriented secondary cracks on the fracture parameters in a rectangular plate under static loading(G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2019-08) Ansari, Gulfam Akhtar; Bisht, NeerajIn the present work, a numerical study using finite element is performed to investigate the effects of randomly oriented secondary cracks on the fracture parameters in a rectangular plate under static loading. Crack is damage that often occurs in members of structures and may cause the sudden serious failure of the structures. The effects of the presence of crack on fracture parameters like stress intensity factor and T-stress of specimen has been the subject of various investigations. However, the parametric studies like the effect of crack offset distance, crack size, orientation and number of crack present on the fracture parameters of the specimen are scarce in the literature. The finite element software ANSYS is used to simulate the fracture parameters. Numbers of studies were conducted to study the accuracy of ANSYS and the meshing parameters on which the accuracy depends. Two types of crack geometries were considered viz. parallel cracks and inclined cracks with different crack ratios. Also, the effect of several secondary cracks was studied. The presence of secondary cracks induced a shielding effect on the primary crack. The presence of secondary crack results in the development of mode II SIF. The mode mixing, however, was minimal and the mode II SIF was insignificant compared to mode I SIF. It is observed that when the cracks are closer to each other the shielding effect is high and as the cracks move away the shielding effect decreases. With the increase in inclination angle intensification effect is decreases. The shielding was also higher for a greater number of neighbouring cracks. Higher length of secondary cracks also increased the shielding effect. A correlation between SIF and T stress was also developed and it was seen that they are highly correlated. T stress can also be an important alternative fracture parameter to study crack interaction problems. Statistical analysis was performed to study the impact of various parameters in comparison to each other for all the geometries it was seen that the crack offset distance has a major influence on SIF compared to the crack ratios. Also, inclined cracks were seen to have a profound impact on SIF compared to parallel cracks. Multi-site damage is a common occurrence in aircraft and nuclear industries and the results of the study can contribute to accessing the structural integrity of the structure and estimate the in-service life of the component.ThesisItem Open Access Dynamic analysis of honeycomb sandwich laminated composite plate(G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2019-08) Adlakha, Prash; Mishra, AnadiA structural sandwich is a peculiar form of a laminated composite comprising of a combination of distinct materials which are bonded together to use effectively the properties of each separate component to the structural advantage of the whole assembly. Two thin, rigid and quite strong faces in the framework are partitioned by a thick, light and weaker core. The faces are attached adhesively to the core to ensure effective load transfer between the components. Owing to the core structure, such composites are differentiated by their stiffness. Despite the thickness of the core, sandwich composites are characterized by their light structure and a good flexural strength. These composites possess unique structure, which provides it a good thermal insulator property. Sandwich composites finds a wide range of application in aeronautics, transportation such as road vehicles, ships, winds, marine and civil engineering. The Laminated sandwiched composite pate is preferred over simple laminated composite plate due to their great ability to essentially decrease weight while maintaining optimum mechanical performance. This weight reduction provides a large number of benefits which includes higher payloads, increased range and comparatively less fuel consumption. The Present study is done to study and investigate the Sandwich composite Panel which is formed by laminating composite sheets with Aluminium Honeycomb core and Dynamic Analysis is done to study its behaviour by computing natural frequency and corresponding deflection. Triangular, Square and Hexagonal cell for the honeycomb will be used to find the best shape under dynamic loading. Further, the effect of hexagonal cell parameter will be studied in order to find optimum parameters in ANSYS 18.1 Software.ThesisItem Open Access Analysis of composite-honeycomb sandwich plate under static loading(G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2019-08) Alam, Firoz; Saxena, RakeshSandwich structures are stiff and are light in weight simultaneously hence they have got a wide range of engineering applications specially in transportation, building materials, aerospace and aviation industry, motor sports etc. In the present investigation a composite-honeycomb sandwich structure is analyzed under static loading using FEM software ANSYS. An epoxy-carbon laminate is bonded to aluminum alloy honeycomb so that the laminate act as the skin and the honeycomb is the core of the sandwich structure. This resulting sandwich structure is analyzed under bending and compressive load with clamped and cantilever boundary conditions. The analysis is done to study the effect of using 3-different basic cell shapes of the honeycomb core viz. triangular honeycomb core, square honeycomb core and hexagonal honeycomb core. Further the effect of varying cell parameter of hexagonal honeycomb core is studied. In clamped-bending and cantilever bending configuration, hexagonal honeycomb core is found to be the strongest among prescribed cores however in compressive load condition square honeycomb is found to be the strongest.ThesisItem Open Access Effect of post heat treatment on crack growth behaviour of friction stir welded butt joint of 7075-T651 aluminium alloys(G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2019-08) Joshi, Ayush; Gope, P.C.Aluminum 7075-T651 is one of the widely used materials for various applications in industry, aerospace, utensils, etc. In the present investigation, fatigue crack growth experiments were performed on both friction stir welded CT specimen and base material CT specimen that are naturally aged, artificially aged at 1900C for 24 h (HT1) and 4230C for 12 h (HT2) with Pmax= 5 kN, Pmin= 0.5 kN and frequency of 6 Hz with R=0.1 under constant amplitude loading and under single overload with an overload ratio of 1.8. The experimental data obtained has been used to plot a-N and da/dN vs. K curve and various fatigue crack growth parameters such as Paris crack growth constants, crack opening stress intensity factor, etc. are determined. The fatigue life is found to be 39000, 36500, 31000 and 41000, 37500, 34000 cycles, respectively for friction stir welded CT specimen and base material CT specimen that are naturally aged, HT1 and HT2.It is observed that there is a significant variation in the variances of crack length increment after the overload. The reduction of crack growth rate is noticed due to the application of overload with an overload ratio of 1.8.The fatigue life after the single overload is found to be 49000, 45000, 40000 and 53000, 46000,41000 cycles, respectively for friction stir welded CT specimen and base material CT specimen that are naturally aged, HT1 and HT2. The values of material constants C and m are calculated through single Paris Curve fit. Scanning electron microscope (SEM)study of fracture surface at different locations is carried out to investigate different modes of fracture occurred to present the effect of different heat treatments such as natural ageing, artificial ageing HT1 and HT2 under constant amplitude loading and due to single overload.ThesisItem Open Access Thermal and mechanical characterization of Functionalized Silicon Carbide (f-SiC) particle reinforced Polyvinyl Alcohol based cross-linked composite(G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2019-08) Bisht, Nitesh; Chauhan, SakshiComposites are applying themselves in almost every engineering field because of their cost-effectiveness and biodegradable behaviour. Polyvinyl alcohol is one of the important biodegradable polymers which gains worldwide consideration from the last decade for the development of biodegradable composite. Green plastic and composites based on polyvinyl alcohol show potential applications therefore polyvinyl alcohol is used as a matrix in the field of material science. In the present study, a modest attempt has been made to functionalized silicon carbide using acidic oxidation with nitric acid to obtain homogeneous stabilized distribution of activated SiC particles within a polymer matrix and develop functionalized silicon carbide (f-SiC) particle reinforced polyvinyl alcohol based cross-linked composite. After fabrication of functionalized silicon carbide (f-SiC) particle reinforced polyvinyl alcohol based cross-linked composite with varying f-SiC weight percentages of PVA (0%, 1%, 2%, 3%, 4%) were put to the investigation. Fabricated samples are firstly examined based on physical tests which consisted of the water absorption tests. Microstructural tests included the Scanning electron microscope (SEM), mechanical tests comprised of the tensile test. Finally, the thermal tests were also done which involved the Thermo gravimetric analysis (TGA), Differential thermal analysis (DTA) and Dynamic mechanical analysis (DMA). The polyvinyl alcohol-based cross-linked composite with 2 weight % of f-SiC content is confirmed to be the best of all compositions under this scrutiny which was authenticated by the microstructural and mechanical tests.ThesisItem Open Access Simulation studies on thermal regenerator for space heating(G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2019-08) Joshi, Anupam; Murthy, D.S.Solar energy available in nature has enough potential to satisfy the energy demands of human, but due to its dilute and intermittent nature, an energy storage medium is necessary to store this energy. Thermal regenerator with the gravels bed as a storage media is one such way to store and utilize the solar energy. In the present work, the simulation study on thermal regenerator having porous solid bed made of gravels is done for the purpose of space heating of room. Parabolic partial differential equations describing the heat transfer between the air and the solid bed are solved by using the Finite Difference Method (FDM) with the help of a program code developed in a MATLAB software. Heating load calculations for a considered room are done in order to determine the mass flow rate of air and the supply air temperature to the room. The program code is developed for charging as well as for the discharge cycle of the bed, where the bed is heated or charged during the day time by the hot air coming out of solar air heater. The temperature of charging air is varying with the time of the day as per the intensity of solar radiation. The same heated bed is discharged by passing the cold ambient air during night. Simulation study has been carried out for beds of different diameter with different particle sizes, and then the optimum number of beds and other parameters are decided accordingly, so as to get the suitable number of heating hours, thus maintaining the required conditions inside the considered space. The results shows that with the decrease in solid particle size, the number of heating hours increases, as with small solid particles, the area of contact between air and solid increases, thereby enhancing the heat transfer process.ThesisItem Open Access Numerical and experimental study of melting performance of a finned tube in a shell latent heat thermal energy storage system(G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2019-08) Rishav Kumar; Verma, PrashantLatent heat thermal energy storage (LHTES) technique helps to reduce the problems related to discrepancy between supply and demand of energy in every aspects of time, space and severity hence it has acquired a great deal of research mainly focussing on the conservation of energy and environment. In the present work, melting characteristics of a lauric acid in a horizontal shell and finned tube type storage unit is studied numerically and experimentally. The low thermal conductive nature of phase change materials (PCMs) have pre-eminently constricted the advantage of this storage system for its various applications hence an attempt has been made to provide the finned tube in the storage container to enhance the heat transfer rate between heat transfer fluid (HTF) and PCM. It has been observed that not much research is carried out to investigate the effect of eccentric arrangement of a finned HTF tube on the melting performance of the PCM experimentally hence different eccentric finned tube position is also considered. The smaller length of fins are considered which covers 33 % of an annulus region for determining the enhancement due to the natural convection effects in the eccentric annulus of storage unit. To investigate the effect of finned tube installed at different eccentric distances on the rate of heat transfer, the melting rate of PCM in an annular is analysed with different angles between fins in bottom annulus of storage unit at different eccentric positions of inner tube through experimental and enthalpy- porosity based numerical two dimensional model in Ansys Fluent software. The results obtained through numerical calculations have been found in agreement with experimental results. The enhancement in the melting rate of PCM at three different eccentric values for inner tube from the centre of outer tube is examined i.e. for e= 12 mm, 18 mm and 24 mm apart from concentric configuration (e= 0 mm) and the effect of inlet temperature of HTF for maximum eccentric and concentric annulus is also explored. Results shows that the melting rate is 21 % higher at the maximum eccentric annulus as compared to those in concentric configuration due to enhanced domination area for natural convection effects, which also increases the uniformity in temperature distribution in PCM and this eccentric behaviour for the enhancement of melting performance is effectively achieved in the fin configuration having angle 60° between the fins in the bottom annulus. It has been also concluded that the increase in Stefan number, enhances the melting rate of PCM irrespective to the eccentric position of inner tube, besides the rate of enhanced natural convection effects due to increase in eccentric distance of inner tube in vertically downward direction is further augmented by 10°C rise in temperature of HTF during the melting process. It is also found that heat storage rate in an eccentric annulus is 18.7 % higher in comparison to concentric annulus.ThesisItem Open Access Performance and emission characteristics of diesel engine using Lemongrass oil, Jatropha biodiesel and diesel oil blends(G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2019-08) Mohd Irshad; Tewari, P.C.Due to the sudden rise in prices and increased awareness of the harmful effects of crude oil on the environment, biodiesel, considered an environmentally friendly source of energy, has become too important as an alternative fuel in recent years. Energy resource demand is rising at a very rapid rate and demand for liquid fuel in the transport sector is very high. Biodiesel is therefore considered seriously as an alternative fuel for the diesel engine. Lemongrass oil is used as an alternative fuel for the diesel engine in the present study, the Jatropha biodiesel. Jatropha oil is first converted to biodiesel using reaction esterification and transesterification to enhance its different properties. In the presence of H2SO4 (1%) and KOH (1% by weight) as a catalyst, methanol (13% by weight) is used as alcohol. Using esterification and transesterification reactions, 94% of biodiesel yield is obtained. The performance, combustion and emission characteristics of a 4.4 kW, single cylinder, four stroke diesel engine, when fuelled with Jatropha biodiesel, Lemongrass oil and its 10-10%, 20-20%, 30-30%, 40-40%, 5-5%, 15-15%, 25-25%, 50-50%, 20-40%, 40-30%, 60-20% and 80-10% blends (on a volume basis) with diesel are investigated and compared with that of the standard diesel. Various experiments have been conducted at a fixed engine speed of 1500 rpm and at 25%, 50%, 75%, and 100% load. The main study is conducted with the aim of increasing the different parameters and characteristics of engine performance by using different selected blends of Jatropha biodiesel, Lemongrass oil with diesel. The parameters of engine performance such as brake power, brake-specific fuel consumption, brake thermal efficiency, smoke density, absorption coefficient, and exhaust temperature were measured and the optimum blends that gave these parameters the best results were investigated. The diesel engine blends L30J30D40 and L40J40D20 are obtained as the best blended fuel. The results of the experiment have been analyzed and compared with standard diesel. It is observed that there is a slight improvement in the combustion and emission characteristics of the engine by using some blends. It is also concluded that biodiesel and it's all blends show approximately similar properties to that of diesel fuel, thus they provided satisfactory results on the engine. The exhaust gas emissions of biodiesel and its all blended fuel types are also found better than that of diesel fuel except at 100% load. Therefore, all these blends can be effectively and efficiently used as an engine fuel without any modifications in the engine.