Inspection of practical plate assemblies is challenging due to the presence of complex features such as bends and corners. The objective is to investigate the influence of bends or curvature in the transverse direction on the propagation of guided waves in plates. A 3D finite element (FE) simulation shows that bends in plates can concentrate and guide ultrasonic energy along the direction of wave propagation. An interesting feature-guided mode that is surprisingly similar to the A0 (fundamental antisymmetric) Lamb mode in normal plates was identified when the bent plate is subjected to 'in-plane' excitation as the generation of this type of mode for a thicknesswise symmetric excitation is unexpected. These results are validated with experiments and discussed using Semi Analytical Finite Element (SAFE) models. © 2013 American Institute of Physics.

Krishnan Balasubramaniam

Department of Mechanical Engineering

Prabhu Rajagopal

Abilasha Ramadhas

P. Sreedhar

Roson Kumar Pattanayak

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Ultrasonic waves guided by transverse bends in plates subjected to symmetric axial excitation

AIP Conference Proceedings

Recent research by the authors shows that bends in plates can act as features that can concentrate and guide ultrasonic energy along their axis. At low frequencies, two feature-guided modes are identified when the bent plate is subjected to 'in-plane' or axial excitation applied uniformly along a through-thickness line bisecting the bent edge. Of these, the slower mode has properties similar to the A0 (fundamental antisymmetric) Lamb mode in flat plates. This paper focuses on the faster bend-guided mode that is similar to the S0 (fundamental symmetric) Lamb mode in flat plates. Using 3D finite element (FE) simulation validated with experiments, this mode is shown to be more strongly generated in smaller angle bends. Features of the mode including velocity, attenuation and modal structure are considered in detailed studies. Results are discussed in light of simple modal studies using the Semi Analytical Finite Element (SAFE) method, suggesting a relationship of bend-guided waves to modes of curved bars. © 2014 Elsevier B.V. All rights reserved.

Ultrasonics

Symmetric low-frequency feature-guided ultrasonic waves in thin plates with transverse bends

The non-dispersive propagation of ultrasonic guided wave higher order modes cluster (HOMC) traveling along the circumferential direction in a hollow cylinder and its interaction with defects in pipe support regions is reported. These circumferential guided waves were generated in mild steel (MS) pipe specimens containing artificially created axial notches (simulating axial cracks) and pinholes (simulating pinhole-like defects) of different sizes in order to simulate conditions such as cracking and corrosion under pipe supports. The characteristics of these guided waves were also studied as a function of parameters related to how they were generated; namely, using: (a) 2.25 MHz linear phased array transducer, (b) 2.25 MHz conventional circular transducer and (c) 1 MHz conventional circular transducer. These higher frequency modes were explored for their ability to detect and size defects. Because of access limitations to the pipe support region in actual field testing, the transducer was always placed at a fixed circumferential position and moved axially along the length of the pipe. The defect position along the circumference was ascertained from the time of flight while the defect size was estimated using the amplitude data. The signals obtained for all three transducer configurations are compared for their ability to locate, detect and size the above-mentioned defects. It was shown that at these relatively higher frequencies, the guided wave modes exhibit small dispersion and have the ability to provide improved imaging of small size defects throughout the cross-section of the pipe. © 2007 Elsevier Ltd. All rights reserved.

NDT and E International

Circumferential higher order guided wave modes for the detection and sizing of cracks and pinholes in pipe support regions

PNRPU Mechanics Bulletin

COMPUTATIONAL SIMULATION OF THE DAMAGE ACCUMULATION PROCESSES IN CRACKED SOLIDS BY THE USER PROCEDURE UMAT OF SIMULIA ABAQUS

Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences

Elastic waves guided by a welded joint in a plate

The Journal of the Acoustical Society of America

Finite element model for waves guided along solid systems of arbitrary section coupled to infinite solid media

Wave Motion

Trapped modes in topographically varying elastic waveguides

Journal	Data powered by TypesetAIP Conference Proceedings
Publisher	Data powered by TypesetAmerican Institute of Physics Inc.
ISSN	0094243X
Open Access	No