Browsing by Author "Vinayak, V."

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Finite element simulation of exit hole filling for friction stir spot welding - A modified technique to apply practically
(Elsevier Ltd, 2014) Vinayak, V.; Sanjeev, N.K.; Hebbar, H.S.; Kailas, S.V.
Friction Stir Spot Welding (FSSW) is a solid state joining process which uses a rotating tool consisting of a shoulder and/or a probe. Though it has proven its potential in joining difficult to weld materials, one of the drawbacks of process is prevalence of exit hole at the end of the process. In the recent past new techniques have been developed to eliminate this draw back by filling this unwanted hole. Determining the appropriate tool design and parameters to fill a hole for given situation is a challenge. The article demonstrates the effective method of obtaining these desired parameters a priory. A three dimensional (3D) model is developed in finite element (FE) commercial code DEFORM 3D/Implicit. It was found that internally filleted shoulders help in filling of holes. The obtained optimized process parameter (tool rotation speed of 900rpm, plunge velocity of 30mm/sec and plunge depth of 0.2 mm) for AA2024 plate (5mm thick) have potential to reduce number of experiments. Â© 2014 The Authors.
Investigations on the effect of various tool pin profiles in friction stir welding using finite element simulations
(Elsevier Ltd, 2014) Vinayak, V.; Sanjeev, N.K.; Hebbar, H.S.; Kailas, S.V.
Friction stir welding (FSW) is a solid state joining process which uses a rotating tool consisting of a shoulder and a pin/probe. The shoulder applies a downward pressure to the work piece surface, generates heat through the friction and leads to plasticization of materials in the vicinity of pin. During traverse the rotating tool mixes the adjacent material in the stir zone, creating a joint without fusion. The welding tool pin profile plays a major role in obtaining desirable weld. At present, research efforts are being made to gain a better understanding of the process, to explore different tool configurations, to optimize the set of process parameters and to widen the applicability of FSW and it variants. In this regard, having reliable finite element model that is capable of simulating FSW with minimal possible simulation time can turn out handy to reduce the number of physical experiments required in such studies and applications. The current work investigates a model based approach in knowing the effect of various tool pin profiles on temperature, stir zone and power consumed for welding. A three-dimensional (3-D) model is developed in finite element (FE) commercial code ABAQUS/Explicit using the Coupled Eulerian-Lagrangian (CEL) formulation, the Johnson-Cook material law and Coulomb's law of friction. The obtained results help in arriving at better tool designs. Â© 2014 Published by Elsevier Ltd.
Prediction of transient temperature at bit-rock interface using numerical modelling approach and optimization
(Springer-Verlag Italia s.r.l., 2024) Vijay Kumar, V.K.; Avinash, A.; Pon Selvan, C.P.; Girish, B.M.; Kunar, B.M.; Flores Cuautle, J.; Ramakrishna, V.K.; Vinayak, V.
One of the major factors impacting on drill bit performance during rock drilling is interface temperature. The performance of the drill bit during drilling operations not only depends on operations parameters but also the properties of rock during drilling in laboratory and field investigations. Hence the present study focused on interface of bit-rock, the temperature had been determined by developing a specially grounded thermocouple. Over 500 different test conditions were performed in each rock sample's case during experimental drilling on a cylindrical block of UCS of 17.83 MPa (fine-grained sandstone grey-FG), 13.70 MPa (medium-grained sandstone-MG), and 51.67 MPa (fine-grained sandstone pink-FGP). The results revealed that the average increase in interface temperature for MG is about 53.74%, FG is about 93.26%, and FGP is about 165.22%. The significant parameters such as uniaxial compressive strength (26%), depth (33%), rate of penetration (15.2%), diameter of the bit (5.26%), and thrust (5.04%) are the most influenced parameters on temperature, followed by spindle speed (1.04%), and torque (0.23%) respectively. The proposed regression models successfully predict the temperature with an R2 value of 91.74%, 90.30%, and 90.95% for MG, FG, and FGP, respectively. Finally overall regression model is developed by considered operational parameters with rock properties to predict temperature and R2 value of 80.8% for all three types of rock samples considered. © The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature 2023.
Unidirectional flipped multiple-pass friction stir process: an innovative step in the fabrication of in situ Al-Cu composites
(Springer Science and Business Media Deutschland GmbH, 2024) Bajakke, P.A.; Vinayak, V.; Jambagi, S.C.; Bhajantri, V.; Deshpande, A.S.
The in situ Al-Cu composites were manufactured by powder metallurgy with state-of-the-art microwave sintering tailed by friction stir process in two different ways: unidirectional overlapped two-pass and unidirectional flipped two-pass. Novelty is claimed in the flipped process. An attempt was made to investigate the addition of copper beyond the solubility limit and the critical composition of an Al-Cu alloy (4.6 wt.%). The overlapped process enforced higher temperature, cumulative strain, and strain rate. Since Al and Cu are high-stacking fault energy metals, both dynamic recrystallization and dynamic recovery occurred and resulted in grain refinement and higher fractions of Al2Cu. The self-hard and brittle nature of Cu and Al2Cu improved strength (Al-3wt.%Cu, 231.23 MPa), hardness (Al-6wt.%Cu, 82.5 HV), and deteriorated ductility (Al-7wt.%Cu, 5.2%). The formed Al2Cu at the interface were surrounded by Al particles and formed passive films Al2O3 and Cu2O enhanced corrosion resistance (Al-5wt.%Cu, 0.00717191 mpy). The process densely compacted the material, minimized porosity, decreased dislocation density, and increased strain aided in better electrical conductivity (Al-5wt.%Cu, 145.92%IACS). The flipped process circumvented excessive heating and embrittlement of the material thereby improving strength without loss of ductility (Al-7wt.%Cu, 235.85 MPa and 25.53%). Al-3wt.%Cu with minimum corrosion current (5.681 µA/cm2) exhibited maximum resistance to corrosion (0.169852 mpy). The highest electrical conductivity was noticed for (Al-5wt.%Cu, 104.17%IACS). © The Author(s), under exclusive licence to Springer-Verlag London Ltd., part of Springer Nature 2024.