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Pulak M. Pandey - One of the best experts on this subject based on the ideXlab platform.
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fabrication and characterization of open cell porous regular interconnected Metallic Structure with solid core
Proceedings of the Institution of Mechanical Engineers Part B: Journal of Engineering Manufacture, 2018Co-Authors: Jatender Pal Singh, Pulak M. PandeyAbstract:Metallic parts having open cell porous regular interconnected Metallic Structure of predetermined unit cell are being fabricated using metal powder–based rapid prototyping machines. These machines are capital intensive. All porous Structures including open cell porous regular interconnected Metallic Structure have less density, so they lack in strength problems as compared to the solid Structure. The strength of open cell porous regular interconnected Metallic Structure can be enhanced by providing solid inner core. In this study, a cost-effective technique has been developed to fabricate open cell porous regular interconnected Metallic Structure with solid core using ceramic powder–based three-dimensional printing machine and pressureless sintering. In this work, two approaches of fabrication were developed. In the first approach, only spherical metal powder was used, while in the second approach, a solid Metallic rod along with spherical metal powder was utilized. Interconnected porosity and sinter dens...
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fabrication and assessment of mechanical properties of open cell porous regular interconnected Metallic Structure through rapid manufacturing route
Rapid Prototyping Journal, 2017Co-Authors: Jatender Pal Singh, Pulak M. PandeyAbstract:Purpose The requirements of open cell porous regular interconnected Metallic Structure (OCPRIMS) in applications such as heat exchangers, sound absorption, fluid flow control, spark arresters and biocompatible inserts have been increased. As per available technology in the present scenario, only the Metallic-based rapid prototyping (RP) machines can guarantee fabrication of OCPRIMS. Metal-based RP machines are capital-intensive. So, this study aims to develop a technique for fabrication of OCPRIMS economically using three-dimensional printing (3 DP) and pressureless sintering. Design/methodology/approach Three computer-aided design (CAD) models of varying designed interconnected porosity 73, 70 and 60 per cent were modeled to target Metallic porosity 27, 30 and 40 per cent. The same were fabricated with ceramic-based powder using 3 DP. Thereafter, spherical bronze powder with average size of 200 µm was filled and sintered in pressureless manner under inert atmosphere of argon. After sintering, the specimens were cleaned with the help of pricking needles and high-pressure water. It flushed the burnt ceramic powder and allowed Metallic portion to remain intact. The obtained specimens were inverse of CAD/3 DP models. The dimensional measurement at different stages of fabrication was carried out to find shrinkage. Sintered density and interconnected porosity were measured using Archimedes’ principle. The characterization of the fabricated specimens was done with the help of microStructure analysis, scanning electron microscopy and energy dispersive x-ray analysis. Mechanical properties were assessed using compressive, tensile and Charpy tests. Findings The feasibility has been explored successfully to fabricate OCPRIMS of phosphor bronze using 3 DP and pressureless sintering process. Interconnected porosity of 51.45, 56.45, 64.09 per cent of final Metallic specimens has been observed against the targeted 27, 30 and 40 per cent. The increase in pore dimensions up to 19.13 per cent and shrinkage up to 5.44 per cent of outer dimensions were found to be the main causes of increase in interconnected porosity level. The characterization results exhibit the behavior of pressureless sintering process and stability of the fabricated specimens. Mechanical properties of fabricated Structures are found to be dependent on porosity and strut diameter. Compressive and tensile strength decrease with the increase in porosity for strut diameter less than 1 mm, whereas they increase with the increase in strut diameter of 1 mm or more. A similar trend has been observed for impact strength also. Originality/value This paper explores the feasibility to fabricate OCPRIMS economically using 3 DP and pressureless sintering process.
Jatender Pal Singh - One of the best experts on this subject based on the ideXlab platform.
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fabrication and characterization of open cell porous regular interconnected Metallic Structure with solid core
Proceedings of the Institution of Mechanical Engineers Part B: Journal of Engineering Manufacture, 2018Co-Authors: Jatender Pal Singh, Pulak M. PandeyAbstract:Metallic parts having open cell porous regular interconnected Metallic Structure of predetermined unit cell are being fabricated using metal powder–based rapid prototyping machines. These machines are capital intensive. All porous Structures including open cell porous regular interconnected Metallic Structure have less density, so they lack in strength problems as compared to the solid Structure. The strength of open cell porous regular interconnected Metallic Structure can be enhanced by providing solid inner core. In this study, a cost-effective technique has been developed to fabricate open cell porous regular interconnected Metallic Structure with solid core using ceramic powder–based three-dimensional printing machine and pressureless sintering. In this work, two approaches of fabrication were developed. In the first approach, only spherical metal powder was used, while in the second approach, a solid Metallic rod along with spherical metal powder was utilized. Interconnected porosity and sinter dens...
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fabrication and assessment of mechanical properties of open cell porous regular interconnected Metallic Structure through rapid manufacturing route
Rapid Prototyping Journal, 2017Co-Authors: Jatender Pal Singh, Pulak M. PandeyAbstract:Purpose The requirements of open cell porous regular interconnected Metallic Structure (OCPRIMS) in applications such as heat exchangers, sound absorption, fluid flow control, spark arresters and biocompatible inserts have been increased. As per available technology in the present scenario, only the Metallic-based rapid prototyping (RP) machines can guarantee fabrication of OCPRIMS. Metal-based RP machines are capital-intensive. So, this study aims to develop a technique for fabrication of OCPRIMS economically using three-dimensional printing (3 DP) and pressureless sintering. Design/methodology/approach Three computer-aided design (CAD) models of varying designed interconnected porosity 73, 70 and 60 per cent were modeled to target Metallic porosity 27, 30 and 40 per cent. The same were fabricated with ceramic-based powder using 3 DP. Thereafter, spherical bronze powder with average size of 200 µm was filled and sintered in pressureless manner under inert atmosphere of argon. After sintering, the specimens were cleaned with the help of pricking needles and high-pressure water. It flushed the burnt ceramic powder and allowed Metallic portion to remain intact. The obtained specimens were inverse of CAD/3 DP models. The dimensional measurement at different stages of fabrication was carried out to find shrinkage. Sintered density and interconnected porosity were measured using Archimedes’ principle. The characterization of the fabricated specimens was done with the help of microStructure analysis, scanning electron microscopy and energy dispersive x-ray analysis. Mechanical properties were assessed using compressive, tensile and Charpy tests. Findings The feasibility has been explored successfully to fabricate OCPRIMS of phosphor bronze using 3 DP and pressureless sintering process. Interconnected porosity of 51.45, 56.45, 64.09 per cent of final Metallic specimens has been observed against the targeted 27, 30 and 40 per cent. The increase in pore dimensions up to 19.13 per cent and shrinkage up to 5.44 per cent of outer dimensions were found to be the main causes of increase in interconnected porosity level. The characterization results exhibit the behavior of pressureless sintering process and stability of the fabricated specimens. Mechanical properties of fabricated Structures are found to be dependent on porosity and strut diameter. Compressive and tensile strength decrease with the increase in porosity for strut diameter less than 1 mm, whereas they increase with the increase in strut diameter of 1 mm or more. A similar trend has been observed for impact strength also. Originality/value This paper explores the feasibility to fabricate OCPRIMS economically using 3 DP and pressureless sintering process.
Shankar Mall - One of the best experts on this subject based on the ideXlab platform.
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modeling of cracked thick Metallic Structure with bonded composite patch repair using three layer technique
Composite Structures, 1999Co-Authors: J J Schubbe, Shankar MallAbstract:A finite element analysis involving three-layers of two-dimensional Mindlin plate elements, to model cracked plate, adhesive, and composite patch, was developed to characterize fatigue crack growth behavior of a thick Metallic panel repaired with an adhesively bonded composite patch. Also, fatigue experiments were conducted with 6.35 mm thick specimens with a pre-crack repaired asymmetrically with adhesively bonded unidirectional boron/epoxy patch. Fatigue crack growth rates on the unpatched and patched faces (PF) were measured along with debond of the composite patch. Stress intensity factors obtained from the analysis were combined with the fatigue crack growth relationship for the unrepaired cracked material to obtain the analytical fatigue crack growth rates. The experimental and analytical fatigue crack growth rates on the unpatched face (UPF) were in a good agreement with each other when the proper consideration of the effective crack length and debond were incorporated in the analysis. Thus, the three-layer technique was found to be capable of characterizing the fatigue crack growth behavior of the repaired thick panels as in the case of repaired thin panels shown in the previous studies.
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Modeling of a cracked Metallic Structure with bonded composite patch using the three layer technique
Composite Structures, 1996Co-Authors: Sam Naboulsi, Shankar MallAbstract:Abstract Due to the high computational cost of three-dimensional finite element analysis, the two-dimensional finite element analysis involving the three layer technique is introduced to investigate the repair of cracked Metallic Structures using an adhesively bonded composite patch. In the three layer technique, two-dimensional Mindlin plate elements with transverse shear deformation capability are used for all three layers; cracked plate, adhesive and composite patch. The accuracy of the three layer technique to compute the stress intensity factor for the Metallic crack is demonstrated by a comparison with available two- and three-dimensional models. The strain energy release rates of the debond at the adhesive interfaces are also examined and compared with the previous studies. The three layer technique provides an efficient and accurate alternative model which is capable of investigating in depth the adhesive effects on the bonded patch repair of cracked Metallic Structures.
M.r. Bhat - One of the best experts on this subject based on the ideXlab platform.
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time reversal technique for health monitoring of Metallic Structure using lamb waves
Ultrasonics, 2009Co-Authors: R Gangadharan, Crl Murthy, S Gopalakrishnan, M.r. BhatAbstract:Abstract Time reversal active sensing using Lamb waves is investigated for health monitoring of a Metallic Structure. Experiments were conducted on an aluminum plate to study the time reversal behavior of A 0 and S 0 Lamb wave modes under narrow band and broad band pulse excitation. Damage in the form of a notch was introduced in the plate to study the changes in the characteristics of the time reversed Lamb wave modes experimentally. Time–frequency analysis of the time reversed signal was carried out to extract the damage information. A measure of damage based on wavelet transform was derived to quantify the hidden damage information in the time reversed signal. It has been shown that time reversal can be used to achieve temporal recompression of Lamb waves under broadband signal excitation. Further, the broad band excitation can also improve the resolution of the technique in detecting closely located defects. This is demonstrated by picking up the reflection of waves from the edge of the plate, from a defect close to the edge of the plate and from defects located near to each other. This study shows the effectiveness of Lamb wave time reversal for temporal recompression of dispersive Lamb waves for damage detection in health monitoring applications.
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Acoustic emission source location and damage detection in a Metallic Structure using a graph-theory-based geodesic approach
Smart Materials and Structures, 2009Co-Authors: Renju Gangadharan, Ganesh Prasanna, Crl Murthy, M.r. Bhat, Srinivasan GopalakrishnanAbstract:A geodesic-based approach using Lamb waves is proposed to locate the acoustic emission (AE) source and damage in an isotropic Metallic Structure. In the case of the AE (passive) technique, the elastic waves take the shortest path from the source to the sensor array distributed in the Structure. The geodesics are computed on the meshed surface of the Structure using graph theory based on Dijkstra's algorithm. By propagating the waves in reverse virtually from these sensors along the geodesic path and by locating the first intersection point of these waves, one can get the AE source location. The same approach is extended for detection of damage in a Structure. The wave response matrix of the given sensor configuration for the healthy and the damaged Structure is obtained experimentally. The healthy and damage response matrix is compared and their difference gives the information about the reflection of waves from the damage. These waves are backpropagated from the sensors and the above method is used to locate the damage by finding the point where intersection of geodesics occurs. In this work, the geodesic approach is shown to be suitable to obtain a practicable source location solution in a more general set-up on any arbitrary surface containing finite discontinuities. Experiments were conducted on aluminum specimens of simple and complex geometry to validate this new method.
Thomas W Ebbesen - One of the best experts on this subject based on the ideXlab platform.
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strong coupling between surface plasmon polaritons and organic molecules in subwavelength hole arrays
Physical Review B, 2005Co-Authors: Jose Dintinger, Stephane Klein, F Bustos, W L Barnes, Thomas W EbbesenAbstract:The interaction of a $J$-aggregate and surface plasmon polariton modes of a subwavelength hole array have been studied in detail. By measuring the effects of hole array period, angular dispersion and concentration of the $J$-aggregate on the transmission of the array, the existence of a strong coupling regime is demonstrated with a Rabi splitting of 250 meV. This large splitting is explained not only by the high oscillator strength of the dye but also by the high local field amplitudes generated by surface plasmons of the Metallic Structure.