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ThesisItem Open Access Effect of Pre-Strain on Micro-Structural Behavior and Mechanical Properties of a Medium Carbon Steel(G. B. Pant University of Agriculture & Technology, Pantnagar-263145, 2023-07) Yadav, Shailesh; Chauhan, SakshiThe aim of this experimental work was to investigate the “Effect of Pre-Strain on Micro-Structural Behavior and Mechanical Properties of a Medium Carbon Steel”. The specimens were austenized for soaking time of 4 hours at temperatures 1100°C and 900°C, then quenched in water. Specimens are subjected pre-strain value 0%, 4%, 7% and 10% of elongation for tensile test before tempering. Then specimens were tempered at temperatures 500°C and 300°C for soaking time 2 hours and cooled in air. After cooling tensile test and hardness test were performed. Tempering and cooling rate have been proven to affect and improve the micro-structure and mechanical properties of medium carbon steel (MCS). Thus, tempering is employed to get desirable qualities of MCS such as increased toughness, ductility or removal of residual stresses. The changes in mechanical behavior as compared with untreated specimens are explained in terms of changes in UTS, Yield strength, hardness, elongation, ASTM number and grain size. Results show that the mechanical Characteristics can be changed and improved by tempering for a particular application. It was also found that the Yield strength and UTS decreases as grain size increases with increase in deformation. UTS and hardness increases by increasing pre-strain value while deformation decreases. Hardness of specimen increased after quenching. To reduce this hardness tempering process was applied and specimen became tougher. With the increase in grain size the percentage elongation also increase. MCS changes from ferrite and pearlite structure to austenite structure when heated over critical temperature. Sudden quenching in water changes its structure austenite to martensite structure. Also the structure of steel is changed by tempering. Some of the extra carbon atoms that were bound in the crystal lattice during quenching have been released during tempering. As a result, tiny, finely scattered carbide particles precipitate within the steel matrix. These carbides prevent dislocations from moving, increasing the steel's strength and hardness.ThesisItem Open Access Investigation on Mechanical Behaviour and Fracture Toughness of Dissimilar AA2024 and AA7075 Friction Stir Welded Joints(2023-07) Singh, Jayant; Gope, P. C.The effect of friction stir tool rotational seed, and post-weld heat treatment on the tensile strength, micro-hardness, and fracture toughness of the dissimilar friction stir welded joint between AA2024 and AA7075 aluminium alloys is studied. The characterizations of the results are performed with the help of optical micrographs, scanning electron micrographs, and EDS/FE-SEM mapping. AA2024 was placed on the retreating side and AA7075 was on the advancing side and the joint was made at 1500 and 2000 rpm tool rotational speed. Two temperatures 170 oC and 423 oC and two soaking times of 12 h and 24 h are used for Post weld heat treatments. 96.2 % enhancement in tensile strength was obtained due to post-weld heat treatment at 423 oC for 24 h soaking time and 1500 rpm tool rotational speed. For 2000 rpm tool rotational speed about 94.3% strength enhancement was obtained for post-weld heat treatment at 170 oC and soaking time of 12 h. All tensile failed specimens show a stir zone as the failure zone with crack initiation from the advancing side and propagated towards the retreating side. Two distinct fracture surface conditions consisting of the curvilinear river-like pattern on the advancing side and a brittle type of fracture on the retreating side were seen. The highest fracture toughness of 26.758 MPa√m, 30.013 MPa√m, and 33.487 MPa√m was obtained for notch location at stir zone, heat affected zone of 2024 side and 7075 side and post weld heat treatment at 170 oC and soaking time 24 h respectively. The strength enhancement is due to the formation of Cu-Mn precipitates with some inter-metallic such as Al7Cu2Fe and Mg2Si. The EDS mapping of the SZ shows a dense agglomeration of Al, Mg, Cu, Zn, and Fe for 1500 rpm tool rotational speed and dense agglomeration of Al, Cr, Cu, Zn, and Mg at the stir zone for 2000 rpm rotational speed.ThesisItem Open Access Effects of Fiber Treatment and Humidity on Mechanical and Thermal Behaviour and Characterisation of Grewia Optiva Fiber Reinforced Composites(G. B. Pant University of Agriculture & Technology, Pantnagar-263145, 2023-05) Chauhan, Sonika; Gope, P. C.The ecological pressure due to growing population and need of structural materials have triggered the need for new materials which can perform equivalently to the conventional structural materials, and are cost effective, easily available and sustainable. This thesis is an investigation of the properties of Grewia Optiva natural fiber reinforced composites (G.O. NFRC). Grewia Optiva is a natural fiber extracted from a wild tree abundantly available in Uttarakhand. It was concluded by Taguchi method that 30 fiber weight %, 45mm fiber length, and fiber orientated normal to the loading axis are optimum for fabricating G.O. NFRC. The mode-I fracture toughness at optimum condition was found as 2.122±0.094 MPa√m . The tensile, flexural, and impact strength corresponding to optimum fiber, and composite processing conditions are 336.32%, 136.93%, and 308.28% higher as compared to pure epoxy. Scanning electron micrographs of the fractured surfaces indicate good bonding of fiber and matrix and show the major fracture mechanisms such as fiber pull-out and fiber-matrix debonding. The effect of humidity, NaOH, and Benzoyl Peroxide (BP) treatment on the mechanical preperties of G.O. NFRC was also studied using Response Surface Methodology (RSM) and ANOVA. The results revealed that the fibre treatment with BP on NaOH pretreated fiber shows optimum results at 90% relative humidity. The corresponding experimental results of the tensile strength (MPa), % elongation, flexural strength (MPa), impact strength (kJ/m2), and fracture toughness (MPa√m) are 260.895±3.619, 5.230±0.221, 52.572±2.550, 33.226±1.838, and 2.565±0.355 respectively. The RSM yielded the optimum tensile strength, % elongation, flexural strength, impact strength, and fracture toughness as 271.42 MPa, 5.163 %, 52.76 MPa, 32.96 kJ/m2, and 2.408 MPa√m respectively. The D-optimal value is 0.768. The mechanical properties indicate that G.O. NFRC can have potential applications like wallboard, window frames, doors, flooring, cubicle walls, ceiling panels.ThesisItem Open Access Application of RSM in design improvement of honeycomb sandwich panel(G. B. Pant University of Agriculture and Technology, Pantnagar, 2022-10) Nagendra Kumar; Misra, AnadiThe geometry and dimensions of honeycomb structure affects the energy absorption characteristics of sandwich structure. It is essential to investigate the dimensional parameters of honeycomb structure on core under impact loading conditions. The combined and individual effect of each design parameter can be studied using response surface method (RSM).The objective of current research is to investigate the effect of various design variables on energy absorption characteristics of sandwich honeycomb structure. The CAD modelling and FEA simulation is conducted on honeycomb structure using ANSYS simulation package. The design of honeycomb sandwich structure is optimized using response surface method (RSM) to determine dimensions for maximum and minimum deformation and stresses. The honeycomb sandwich structure has shown good energy absorption characteristics. The internal energy of sandwich honeycomb structure changes abruptly as the bullet pierces through honeycomb structure. The force reaction by honeycomb structure in optimized design is found to increase by nearly 26.7%. The optimized design is able to further reduce kinetic energy of bullet during exit from sandwich structure by 23%.ThesisItem Open Access Modelling and analysis of hierarchical honeycomb structure using finite element method(G. B. Pant University of Agriculture and Technology, Pantnagar, 2022-10) Shah, Amit Kumar; Misra, AnadiHoneycomb structures are strong and light composite structures with a high load bearing capability. A hierarchical honeycomb is a bio-inspired novel honeycomb shape that is employed for structural applications. The stiffness behaviour of hierarchical honeycombs is influenced by superstructure geometry. The deformation of a superstructure-based hierarchical honeycomb with varying cell lengths (4.36 mm, 5.32 mm, 6.28 mm, and 7.14 mm) was investigated in this research. For out of plane directed crushing, a numerical approach using the ANSYS static structure module was applied. The effects of various superstructure geometries were investigated. The boundary condition of a three point bend test configuration was performed on the structure. A deformation force of 200N, 400N, 600N, 800N, and 1000 N was applied at the midpoint of the honeycomb structure's span. The deformation caused in the member reduces as the superstructure cell length rises. The structure gets stiffer and exhibits less deformation as the core height increases. The honeycomb sandwich structure becomes stiffer as the thickness of the face sheet increases. Where weight is not an important structural criterion, a super-structure honeycomb sandwich structure may be the best solution.ThesisItem Open Access Numerical investigations on phase change materials in a horizontal shell and tube thermal energy storage system using different fin configuration(G. B. Pant University of Agriculture and Technology, Pantnagar, 2022-09) Mallik, Shubham; Mallik, Shubham; Mallik, Shubham; Bhandari, S.S.; Bhandari, S.S.; Bhandari, S.S.In order to improve the melting performance of phase change materials (PCM) in latent heat thermal energy storage unit (LHTES), the Angled rectangular with U-shaped tip fin design is proposed in this work. A two-dimensional numerical model based on enthalpy porosity method and Boussinesq approximation were used to model PCMs phase change transformation and the Buoyancy effect. The melting behavior of PCM is investigated by melt front evolution, temperature variation, effect of natural convection and variation of Stefan and Fourier number respectively. The results conclude that Angled rectangular U-shaped tip fin LHTES design is best suitable to enhances melting performance of PCM. The melting time decreases by 80.60 %, 74.42 % and 79.69 % as compared to Bare pipe for Angled rectangular with U-shped tip fin for PCMs Lauric acid, Paraffin wax and Capric acid respectively. The solidification time also decreases by a factor these PCMs. The melting time also decrease by a factor of 71.13 % due to rotation effect of whole domain for Angled rectangular with U-shaped tip fin latent heat thermal energy storage system.ThesisItem Open Access Investigation on the thermal performance of shell and tube thermal energy storage system using paraffin wax as phase change material(G. B. Pant University of Agriculture and Technology, Pantnagar, 2022-09) Tiwari, Mayank; Verma, PrashantEnergy conversion is an essential aspect of technology advancement, and hence its efficient generation and use are important in today's scenario. In present scenario, there is a large gap between demand and supply, and it is difficult to meet the current energy requirement. Thermal energy storage devices enable us to attain energy demand while simultaneously minimizing pollution. The semi-circular outer shell geometry of the LHTES unit with and without fins on the inner tube using paraffin wax as phase change material has not been investigated yet. Hence it has been decided to investigate the melting performance of paraffin wax numerically and experimentally for circular shell, semi-circular shell without fins and semi-circular shell with finned tube latent heat thermal energy storage (LHTES) systems. Numerical analysis of two-dimensional model of different configurations of the LHTES system has been performed in Ansys fluid fluent to investigate the thermal performance of paraffin wax. Since natural convection plays important role in the melting process so the outer shell geometry is modified to semi-circular so that whole PCM is present in the upper portion and the heat transfer between the solid PCM and liquid PCM improves. In order to further improve the thermal performance fins are added to inner tube of the LHTES unit. Therefore, five different configurations including three different semi-circular with finned tube for different fin angles ( = 60º, 90º, 120º), semi-circular without fin, circular configuration have been investigated for the melting performance of the PCM. The results for a semi-circular shell with a fin angle of 90º for the LHTES system are found better as the thermal energy storage rate of finned tube LHTES system is 0.11 kW, which is 110% higher as compared to circular and 88% higher as compared to the semi-circular LHTES system. The semi-circular shell with finned tube LHTES melts the PCM completely in 66 minutes which is 54.98% less than the circular LHTES system and 32.65 % less in comparison to semi-circular without fin configuration. Thermal energy stored in the circular and semi-circular without fins arrangement of LHTES unit is 275.7 KJ and 290.37 KJ respectively. The thermal energy stored in the semi-circular LHTES unit with fins on the inner tube is 297 KJ which is 7.72% more as compared to the circular configuration and 2.3% more than the semi-circular without fins arrangement for same time period of 7200 sec. The thermal energy storage efficiency of semi-circular with finned tube LHTES unit has been found 6.72% higher than that of the circular LHTES system and 2% higher than the semi-circular without finned tube LHTES.ThesisItem Open Access Experimental and simulation studies on blanching and its impact on drying rate of carrot(G. B. Pant University of Agriculture and Technology, Pantnagar, 2022-10) Joshi, Ashutosh; Pratihar, A.K.Fruits and vegetables are high in minerals, vitamins, antioxidants and fibers but low in fat and calories, which is beneficial to human health. Because fruits and vegetables are seasonal and do not hold for long, techniques such as drying, freezing and canning are used to extend their shelf life. Blanching is a heat treatment process performed before these processes to improve safety and quality. Carrots are one of the healthiest vegetables because they are high in carbohydrates, minerals like calcium, phosphorus, iron, sodium, zinc, magnesium and vitamin C. Blanching of carrot and its effect on drying rate of carrot has been investigated in this study by experimental and numerical methods. Besides this various thermo-physical properties required in simulation have been determined through experiments and using correlations. The simulation of the blanching process has been carried out using ANSYS Fluent software to determine the temperature distribution in carrot during blanching at optimum combination of temperature and time (95°C for 5 minutes). Carrots have been actually blanched at 4 different temperatures-time combinations; 80°C for 7 minutes, 85°C for 7 minutes, 90°C for 7 minutes and 95°C for 5 minutes. Under these blanching conditions, the effect of separating carrot cortex and core from the slice on their drying rate has also been studied. For various configurations, the Page model has been used to perform regression analysis and estimate the value of the drying constant (k). The hot air has been used for drying carrot samples, where a constant temperature of 70°C±0.1°C and a constant velocity of 0.5 m/s have been maintained. According to the present study, the drying rate of core has been found to be the highest for each blanching combinations followed by cortex and slice. Blanching also improves the drying constant and it can be seen that at optimum blanching conditions, the drying constant for slice, cortex and core is 22.84%, 24.90%, and 36.94%, respectively higher than for similar parts of the unblanched sample.ThesisItem Open Access Optimization of resistance spot welding process parameters for cold rolled mild steel lap joint based on tensile shear strength(G. B. Pant University of Agriculture and Technology, Pantnagar, 2022-10) Pankaj Kumar; Bisht, NeerajOwing to its numerous applications weld characteristics of cold rolled mild steel grade IS 513 CR 1 was investigated. Resistance spot welding, one of the most versatile welding technology was used for the purpose. The three most important parameters of the RSW namely welding current, welding time and electrode pressure were varied and the influence on the Tensile Shear Strength (TSS) was evaluated. The experiments were carried out according to Taguchi's L9 orthogonal array and Taguchi analysis was used in optimization. A lap joint of dimensions 120mm x 30 mm x 1.5mm was welded using a 100 kVA timer, current-controlled CSP-100PR Spot Welder, to create an overlap of 3 mm thickness. According to Taguchi’s L9 OA welding current cycles of 5, 10 and 15 were selected. During the welding process, the welding current was changed by adding 2 kA from 10 to 14 kA and the electrode pressure were taken to be 4, 5 and 6 bar. The Main effects plots revealed the optimal setting for the process parameters as welding current of 14 kA (Level 3), welding time of 15 cycles (Level 3), and electrode pressure of 4 bar (Level 1). The optimized process parameters showed the maximum TSS of the spot weld joint. ANOVA was carried out to identify the significant process parameters affecting the weld strength. Furthermore, the contribution of welding current was found to be 67.38% which had the maximum influence on the TSS of the welded joint. The contour plots showed that on increasing welding current and welding time with decreasing electrode pressure the Tensile Shear Strength of lap joint was increased by 55.78%, 26.27% and 33.65% respectively
