Browsing by Author "Rajpal, R."

Now showing 1 - 9 of 9

An experimental study to evaluate the warpage and cracking issues in fused deposition modeling
(Pleiades journals, 2019) Suhas, A.; Rajpal, R.; Gangadharan, K.V.; Umesh, U.
Research in 3D printing technology is growing immensely because of the advantage of manufacturing complex shapes in less time as compared to conventional manufacturing processes. However, warpage and cracking are the critical issues in fused deposition modeling technique which results in a reduction in the strength of the component. This paper aims to address the root causes for reducing the warpage and cracking in a 3D printed component. Fused-deposition-modeling-based 3D printer is used in this study to manufacture the samples. The behavior of warpage and cracking in the specimens are studied by altering bed temperature and extrusion width of the filament. The experimental results revealed that printing a component at 100 °C and 0.75 mm extrusion width led to minimum warpage and no crack condition. © Springer Nature Singapore Pte Ltd. 2019.
Experimental investigation of 3D-printed polymer-based MR sandwich beam under discretized magnetic field
(Springer Verlag service@springer.de, 2018) Rajpal, R.; Lijesh, K.P.; Gangadharan, K.V.
Smart materials are being employed in dynamic systems to tune the stiffness and damping of the structure by using external stimuli. Magnetorheological elastomers (MREs) are considered to be as one of the smart materials because of their characteristics of altering the dynamic properties under the external magnetic field. So far, MRE sandwich beams have been developed by embedding them between two parent structures. In the present work, a novel technique of embedding MR materials is presented to create complex sandwich structures. This technique will replace the conventional embedding technique which uses adhesives to bind the MR materials with the parent structure. The vibration characteristics of the developed sandwich beams are estimated by conducting harmonic analysis to a predefined band of frequency range under the different directions of magnetic field. Sinusoidal signals of desired frequency and amplitude were proffered using NI educational laboratory virtual instrumentation suite to an amplified piezoactuator for exciting the MR sandwich beam. A non-contact-type laser displacement sensor is used in this study to avoid the additional mass of the sensor on the beam. The results indicate that the smart materials can be efficiently embedded with the sandwich beam without using the adhesives. It is also found that by changing the direction of magnetic field, the range of the variation in stiffness of MR sandwich beam can be increased to enhance the isolation effect at fundamental natural frequency. © 2018, The Brazilian Society of Mechanical Sciences and Engineering.
Experimental study on the dynamic properties of magneto-rheological materials
(2018) Rajpal, R.; Lijesh, K.P.; Kant, M.; Gangadharan, K.V.
Magneto-rheological elastomer (MRE), is considered to be a smart material, which transFigure their rheological properties with the external applied magnetic field. Due to this novel property, MREs are extensively employed to control the vibration of a system at resonant frequency. Presently, MREs are integrated in a structure through a layer by layer technique and the bigger drawback of this technology is that, in the presence of high transverse shear stresses, de-lamination occurs which may result in failure of the system. To overcome the aforementioned problem, a novel method is proposed to merge the MREs with Fused Deposition Method (FDM). FDM is used to develop the primary structure with cavities using a FDM compatible material and MRE i.e. secondary material is filled in the cavities. It is postulated that the proposed methodology has the capability of reducing the possibility of de-lamination. Now, to investigate the dynamic performance of the developed structure, an experimental test setup was developed by fixing one end of the beam and supplying the desired magnetic field to the beam using an electromagnet. From the test results, It was concluded that, with the increase in the applied magnetic field, the isolation effect of the structure enhanced and it reduced with the shift of electromagnet from the free end to fixed end of the beam. Further, in the case of MRE, high magnetic field is required for achieving satisfactory performance, which results in increase of the electromagnet weight, in turn making the system bulkier. Therefore, the present work endeavours to replace the MRE with MR Fluid (MRF) in the same primary structure and perform a comparison study between MRE and MRF, for the same applied magnetic field. From the experimental results it was envisaged that the MRF depicted better isolation capability than MRE. � Published under licence by IOP Publishing Ltd.
Experimental study on the dynamic properties of magneto-rheological materials
(Institute of Physics Publishing helen.craven@iop.org, 2018) Rajpal, R.; Lijesh, K.P.; Kant, M.; Gangadharan, K.V.
Magneto-rheological elastomer (MRE), is considered to be a smart material, which transFigure their rheological properties with the external applied magnetic field. Due to this novel property, MREs are extensively employed to control the vibration of a system at resonant frequency. Presently, MREs are integrated in a structure through a layer by layer technique and the bigger drawback of this technology is that, in the presence of high transverse shear stresses, de-lamination occurs which may result in failure of the system. To overcome the aforementioned problem, a novel method is proposed to merge the MREs with Fused Deposition Method (FDM). FDM is used to develop the primary structure with cavities using a FDM compatible material and MRE i.e. secondary material is filled in the cavities. It is postulated that the proposed methodology has the capability of reducing the possibility of de-lamination. Now, to investigate the dynamic performance of the developed structure, an experimental test setup was developed by fixing one end of the beam and supplying the desired magnetic field to the beam using an electromagnet. From the test results, It was concluded that, with the increase in the applied magnetic field, the isolation effect of the structure enhanced and it reduced with the shift of electromagnet from the free end to fixed end of the beam. Further, in the case of MRE, high magnetic field is required for achieving satisfactory performance, which results in increase of the electromagnet weight, in turn making the system bulkier. Therefore, the present work endeavours to replace the MRE with MR Fluid (MRF) in the same primary structure and perform a comparison study between MRE and MRF, for the same applied magnetic field. From the experimental results it was envisaged that the MRF depicted better isolation capability than MRE. Â© Published under licence by IOP Publishing Ltd.
Parametric Modeling and Real Time Remote Experimentation of a Reconfigurable Coupled Pendulum
(2018) Rajpal, R.; Kant, M.; Kuchibhatla, S.A.R.; Gangadharan, K.V.
This paper presents parametric modeling and real time remote experimentation of a reconfigurable coupled pendulum on a data flow visual programming platform - G Programming. The motivation behind creating the experiment was to make it virtually available for e-learning in the field of vibration analysis & diagnostics. The derived math models replicated the low frequency system dynamics and were used in simulations to highlight inherent system behaviour. Finally, experiment was conducted for various system configuration settings characterized by pre-set discrete lengths of the pendulums. Sensors and actuators used for the experimentation were integrated using LabVIEW. Smartphone and Cross-Platform Communication Toolkit (SCCT) was employed to establish communication between remote user and Master computer. The experiment highlighted bimodal dynamic behaviour of the system in individual and combined modes of vibration through an Internet based remote experimentation platform. � 2018 Elsevier Ltd.
Parametric Modeling and Real Time Remote Experimentation of a Reconfigurable Coupled Pendulum
(Elsevier Ltd, 2018) Rajpal, R.; Kant, M.; Kuchibhatla, S.A.R.; Gangadharan, K.V.
This paper presents parametric modeling and real time remote experimentation of a reconfigurable coupled pendulum on a data flow visual programming platform - G Programming. The motivation behind creating the experiment was to make it virtually available for e-learning in the field of vibration analysis & diagnostics. The derived math models replicated the low frequency system dynamics and were used in simulations to highlight inherent system behaviour. Finally, experiment was conducted for various system configuration settings characterized by pre-set discrete lengths of the pendulums. Sensors and actuators used for the experimentation were integrated using LabVIEW. Smartphone and Cross-Platform Communication Toolkit (SCCT) was employed to establish communication between remote user and Master computer. The experiment highlighted bimodal dynamic behaviour of the system in individual and combined modes of vibration through an Internet based remote experimentation platform. Â© 2018 Elsevier Ltd.
Parametric studies on bending stiffness and damping ratio of Sandwich structures
(Elsevier B.V., 2018) Rajpal, R.; Lijesh, L.; Gangadharan, K.V.
Sandwich structures are extensively used in aviation industries to reduce the overall weight of the system. Although the mechanical behavior of these structures has been widely studied, the performance of core shape in vibration response has been minimally explored. This study focuses on understanding the various influences of sandwich structures considering the following parameters: (i) nature of core shape, (ii) number of infill shapes, and (iii) orientation of cores, which affect the dynamic behavior of sandwich structures. Nine sandwich structures comprising three different core shapes, hexagon, triangle, and square shapes, in three different orientations, namely 0° 45° and 90° were considered for the present study. These structures in the beginning were put by modal analysis using finite element method (FEM). All the nine structures were printed using the fused deposition method to validate the FEM findings, while the DEWE soft data acquisition system was used to estimate the modal parameters (i) natural frequency and (ii) damping ratio. Natural frequency and damping ratio were estimated using FRF and Nyquist circle plot, respectively. This study demonstrates that although the square core orientated at 0° exhibited superior stiffness in bending loads, the hexagonal core orientated at 0° displayed an admirable combination of both stiffness and damping properties. © 2018 Elsevier B.V.
Sensor Fusion for Operational Mode Shape Analysis of Multi DoF Systems
(2018) Rahul, R.; Rajpal, R.; Aditya, Raman, Kuchibhatla, S.; Gangadharan, K.V.
This paper presents an experimental approach to study the dynamic behavior of a multi DOF system by sensor fusion technique. An experimental model is designed and developed to simulate real dynamic problem. Frequency response function (FRF) is obtained by conducting impact hammer test from which natural frequencies of the system are identified. Mode shapes are analyzed using forced vibration test at selected frequency zones. This study illustrates the benefits of using sensor fusion for the study of behavior of complex dynamic systems. � 2018 Elsevier Ltd.
Sensor Fusion for Operational Mode Shape Analysis of Multi DoF Systems
(Elsevier Ltd, 2018) Rahul, R.; Rajpal, R.; Kuchibhatla, S.A.R.; Gangadharan, K.V.
This paper presents an experimental approach to study the dynamic behavior of a multi DOF system by sensor fusion technique. An experimental model is designed and developed to simulate real dynamic problem. Frequency response function (FRF) is obtained by conducting impact hammer test from which natural frequencies of the system are identified. Mode shapes are analyzed using forced vibration test at selected frequency zones. This study illustrates the benefits of using sensor fusion for the study of behavior of complex dynamic systems. Â© 2018 Elsevier Ltd.