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Prabhu Rajagopal

Bio: Prabhu Rajagopal is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Ultrasonic sensor & Guided wave testing. The author has an hindex of 18, co-authored 129 publications receiving 1035 citations. Previous affiliations of Prabhu Rajagopal include Imperial College London & Indian Institutes of Technology.


Papers
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Proceedings ArticleDOI
TL;DR: In this article, a bend-guided wave was used for inspection and monitoring structural bends using a special ultrasonic bend guided wave, which concentrates the energy in and around the bend.
Abstract: This paper investigates the inspection and monitoring structural bends using a special ultrasonic bend-guided wave, which concentrates the energy in and around the bend. Modal studies are carried out using the Semi-Analytical Finite Element (SAFE) method, while 3D finite element (FE) simulations are used to gain visualization of results and also obtain cross-validation. Our studies reveal, perhaps for the first time, the possibility of bend-guided modes of the shear-horizontal (SH) family, in addition those of the Rayleigh-Lamb family reported earlier in the literature. This mode has attractive properties including low attenuation and limited dispersion. We investigate effects of plate thickness and bend radius on the physics of FGW in bends, arguing the strong role of geometry and curvature effects in causing mode confinement. Experiments have also been carried out to validate the existence of such bend-guided mode. doi: 10.12783/SHM2015/83

1 citations

Journal ArticleDOI
TL;DR: In this article , the performance of laser spot thermography (LST) in defect detection on a mild steel sample at different temperatures (30 −600°C) was investigated.
Abstract: This paper studies the performance of laser spot thermography (LST) in defect detection on a mild steel sample at different temperatures (30–600 °C). In laser spot thermography, a laser spot is used to scan over the surface of the sample and the thermal profile is monitored using a thermal camera. For checking the feasibility/capability of laser spot thermography in defect detection under higher temperatures, a three-dimensional numerical model is developed using a commercial FE software package. This FE model is used to understand the heat transfer phenomenon during defect detection at higher temperatures, even after oxidation temperature. The influence of the oxide layer formation (scale) at higher temperatures (above 500 °C) in defect detection is established using the validated model. The thermal properties and optical properties of this oxide layer are different from those of the base metal; this will lead to a drastic variation in the thermal profile after the oxidation temperature. An oxide layer at 600 °C is introduced in the improved numerical model as a thin resistive layer at the top surface with a thickness of 50 μm. The thermal properties of the layer are assigned as the scale properties. FE modeling results show better agreement with experimental results even at 600 °C. Thus, the applicability of LST in high temperatures is experimentally proved.

1 citations

Proceedings ArticleDOI
01 May 2017
TL;DR: In this article, the authors demonstrate the application of a holey-structured metamaterial lens for sub-wavelength imaging of defects in a metallic sample, in the ultrasonic regime.
Abstract: In this paper we demonstrate the application of a holey-structured metamaterial lens for sub-wavelength imaging of defects in a metallic sample, in the ultrasonic regime. This type of lens, operating on the Fabry-Perot resonance principle, has earlier been demonstrated for super-resolution in the acoustic regime, and by the authors for nominal sub-wavelength resolution in the ultrasonic regime. Here we experimentally demonstrate a subwavelength imaging of an artificially created crack of size λ/15 in the aluminium sample: to our knowledge this is the highest resolution achieved in the ultrasonic regime. The subwavelength image obtained with the ultrasonic system incorporated with the holey-structured metamaterial is shown to compare favourably with corresponding results obtained using X-ray Computed Tomography (CT).

1 citations

Proceedings ArticleDOI
18 May 2012
TL;DR: This work uses CUDA to develop parallel finite difference schemes as applicable to two problems of interest to NDE community, namely heat diffusion and elastic wave propagation.
Abstract: Advances in parallel processing in recent years are helping to improve the cost of numerical simulation. Breakthroughs in Graphical Processing Unit (GPU) based computation now offer the prospect of further drastic improvements. The introduction of 'compute unified device architecture' (CUDA) by NVIDIA (the global technology company based in Santa Clara, California, USA) has made programming GPUs for general purpose computing accessible to the average programmer. Here we use CUDA to develop parallel finite difference schemes as applicable to two problems of interest to NDE community, namely heat diffusion and elastic wave propagation. The implementations are for two-dimensions. Performance improvement of the GPU implementation against serial CPU implementation is then discussed.

1 citations

Proceedings ArticleDOI
02 Jul 2019
TL;DR: In this article, a screw conveyor based sludge cleaning mechanism is proposed to clean the sticky sludge from the floor of aboveground oil storage tanks and interface effectively with tank inspection robots to perform cleaning and inspection synchronously.
Abstract: Oily sludge on the floor of the tank is a significant problem for petrochemical industries and floor inspection robots. Oily sludge is a hazardous material containing a complex mixture of hydrocarbon, water, sand, and minerals deposited on the floor of the oil storage tanks. Sludge accelerates corrosion, reduces storage capacity, sticks to floor inspection robots and disrupts further tank operations Industries have started deploying robots in a tank to automate and replace the hazardous manual tank tasks. This paper presents the design of a screw conveyor based sludge cleaning mechanism to clean the sticky sludge from the floor of aboveground oil storage tanks and interface effectively with tank inspection robots to perform cleaning and inspection synchronously. The cleaning mechanism consists of a screw conveyor mounted on a 'C' shaped case with a bearing on both sides, a waterproof motor connected to the screw conveyor with a worm-wheel gear. A Rheometer is used for measuring sludge properties to understand its flow behavior. Computational fluid dynamics (CFD) based numerical simulation is performed to visualize the flow of oily sludge through the proposed cleaning mechanism.

1 citations


Cited by
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Journal ArticleDOI
01 Apr 1956-Nature
TL;DR: The Foundations of Statistics By Prof. Leonard J. Savage as mentioned in this paper, p. 48s. (Wiley Publications in Statistics.) Pp. xv + 294. (New York; John Wiley and Sons, Inc., London: Chapman and Hall, Ltd., 1954).
Abstract: The Foundations of Statistics By Prof. Leonard J. Savage. (Wiley Publications in Statistics.) Pp. xv + 294. (New York; John Wiley and Sons, Inc.; London: Chapman and Hall, Ltd., 1954.) 48s. net.

844 citations

Journal ArticleDOI
TL;DR: In this article, the use of X-ray computed tomography (XCT) is examined, identifying the requirement for volumetric dimensional measurements in industrial verification of additively manufactured (AM) parts.
Abstract: In this review, the use of x-ray computed tomography (XCT) is examined, identifying the requirement for volumetric dimensional measurements in industrial verification of additively manufactured (AM) parts. The XCT technology and AM processes are summarised, and their historical use is documented. The use of XCT and AM as tools for medical reverse engineering is discussed, and the transition of XCT from a tool used solely for imaging to a vital metrological instrument is documented. The current states of the combined technologies are then examined in detail, separated into porosity measurements and general dimensional measurements. In the conclusions of this review, the limitation of resolution on improvement of porosity measurements and the lack of research regarding the measurement of surface texture are identified as the primary barriers to ongoing adoption of XCT in AM. The limitations of both AM and XCT regarding slow speeds and high costs, when compared to other manufacturing and measurement techniques, are also noted as general barriers to continued adoption of XCT and AM.

330 citations