Interaction of fundamental torsional ultrasonic pipe guided mode T(0, 1) from defects caused by induction pressure welding (IPW) process is studied using three-dimensional (3D) finite element (FE) analysis validated by experiments. Defects are assumed as cross-sectional notches along the weld bond-line, and both surface-breaking and embedded features are considered. Results show that T(0, 1) mode reflection from weld defects is strongly influenced by features of the weld itself. However, with supplementary results such as the mode-converted flexural F(1, 3) and F(1, 2) modes and circumferential variation of T(0, 1) reflection, there is potential for an effective screening solution. © 2017 by ASME.

Krishnan Balasubramaniam

Department of Mechanical Engineering

Prabhu Rajagopal

Guided electromagnetic wave propagation

PRESSURE WELDING

Reflection

Surface defects

Tubing

Welding

Welds

BOND LINE

CIRCUMFERENTIAL VARIATION

GUIDED MODES

MODE CONVERSIONS

SURFACE BREAKING

THREE-DIMENSIONAL (3D) FINITE ELEMENT ANALYSIS

TORSIONAL GUIDED WAVES

WELD DEFECTS

finite element method

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

Reflection and Mode Conversion of Fundamental Torsional Guided Wave Mode From Lack of Bonding in Induction Pressure Welding

Journal of Pressure Vessel Technology, Transactions of the ASME

The authors have recently reported on the attractive properties of shear-horizontal type feature guided (SHB) waves for the inspection of 90° plate bends. Further to this, here the interaction of the SHB mode with transverse and longitudinal defects in the bend region is studied using 3D finite element simulations validated by experiments. Trends are discussed in light of the underlying wave mechanics principles. The results show that the SHB mode yields improved through-thickness defect resolution capabilities as compared to regular plate guided SH waves in view of mode confinement and higher frequencies used. © 2015 Elsevier Ltd. Allrightsreserved.

NDT and E International

Interaction of shear horizontal bend (SHB) guided mode with defects

The use of ultrasonic guided waves for the inspection of pipes with elbow and U-type bends has received much attention in recent years, but studies for more general bend angles which may also occur commonly, for example in cross-country pipes, are limited. Here, we address this topic considering a general bend angle φ, a more general mean bend radius R in terms of the wavelength of the mode studied and pipe thickness b. We use 3D Finite Element (FE) simulation to understand the propagation of fundamental axisymmetric L(0, 2) mode across bends of different angles φ. The effect of the ratio of the mean bend radius to the wavelength of the mode studied, on the transmission and reflection of incident wave is also considered. The studies show that as the bend angle is reduced, a progressively larger extent of mode-conversion affects the transmission and velocity characteristics of the L(0, 2) mode. However the overall message on the potential of guided waves for inspection and monitoring of bent pipes remains positive, as bends seem to impact mode transmission only to the extent of 20% even at low bend angles. The conclusions seem to be valid for different typical pipe thicknesses b and bend radii. The modeling approach is validated by experiments and discussed in light of physics of guided waves. © 2013 Elsevier B.V. All rights reserved.

Ultrasonics

Interaction of low-frequency axisymmetric ultrasonic guided waves with bends in pipes of arbitrary bend angle and general bend radius

This paper studies the feasibility of using ultrasonic guided waves to rapidly inspect tubes and pipes for possible eccentricity. While guided waves are well established in the long range inspection of structures such as pipes and plates, studies for more complex cross sections are limited and analytical solutions are often difficult to obtain. Recent developments have made the Semi Analytical Finite Element (SAFE) method widely accessible for researchers to study guided wave properties in complex structures. Here the SAFE method is used to study the effect of eccentricity on the modal structures and velocities of lower order guided wave modes in thin pipes of diameters typically of interest to the industry. Results are validated using experiments. The paper demonstrates that even a small eccentricity in the pipe can strongly affect guided wave mode structures and velocities and hence shows potential for pipe eccentricity inspection. © 2014 AIP Publishing LLC.

AIP Conference Proceedings

Ultrasonic guided waves in eccentric annular pipes

This paper reports on a new means of generating higher-order mode clusters of guided waves (HOMC-GW) using a meander-coil (MC) electromagnetic acoustic transducer (EMAT) in plates at frequencies significantly higher than the lower-order plate modes. These wave modes are considerably less dispersive and they occur at much higher frequency¿thickness (f x d) products. Our studies cover the f x d range of 13 to 20 MHzmm. Experimental measurements were carried out on Al plate samples of different thicknesses using three different EMAT coil periods. To understand the generation and propagation characteristics of HOMC-GW with EMATs, several simulations were carried out using 2-D finite element models at different f x d products. These simulations captured all features observed in the experiments. The time¿frequency smoothed pseudo Wigner-Ville distribution (SPWVD) was used to analyze the HOMC-GW modes. Defect detection measurements using HOMC-GW generated using EMATs were made on Al plates with machined defects. © 2012 IEEE.

IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control

Generation and detection of higher-order mode clusters of guided waves (HOMC-GW) using meander-coil EMATs

Corrosion detection in the annular plate region of above- ground storage tanks is a critical needfor tank farm operators in the oil and gas industry. The critical zone between the tank shell wall and the first few inches of the annular plate is difficult to inspect with conventional floor scanning methods due to the presence of coatings, uneven surfaces and a lack of access due to the presence of the weld toe. This region, however, is prone to accelerated corrosion due to the additional stresses caused by the weight of the tank wall and the increased possibility of water entrapment under the annular plate. Repairs in this region demand replacement of the entire annular plate and this leads to long shutdown of the tank, and often failures occur without any warning. A new method using the Higher Order Modes Cluster Guided Waves (HOMC*) to detect and screen defects in the critical inaccessible zones in the annular plate is discussed. This testing can be carried out online while the tank is in operation using HOMC guided waves generated on the outer exposed region of the annular plate. Robotic scanners allow for the inspection to be carried out in relatively short periods of time. Data collected in the laboratory as well as from the field trials are presented. The HOMC technique has potential for non-destructive inspection of inaccessible regions in structures for medium-range applications (2 to 3 m).

Insight: Non-Destructive Testing and Condition Monitoring

Higher order modes cluster (HOMC) guided waves for online defect detection in annular plate region of above-ground storage tanks

Reflection and Mode Conversion of Fundamental Torsional Guided Wave Mode from Lack of Bonding in Induction Pressure Welding

Journal	Journal of Pressure Vessel Technology, Transactions of the ASME
Publisher	American Society of Mechanical Engineers (ASME)
ISSN	00949930
Open Access	No