Journal of Pure and Applied Ultrasonics

A. Ravi Gopal ¹, M. R. Jeyan ², C. Asokane ², Anish Kumar ¹, B. Purnachandra Rao ¹

Affiliations
1 NDE Division, Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam-603102, IN
2 Instrumentation Development and Services Division, Fast Reactor Technology Group, Indira Gandhi Centre for Atomic Research, Kalpakkam-603102, IN

Abstract

Ultrasonic technique is useful for viewing the internals of sodium cooled fast reactors. Ultrasonic transducer is the key element to carry out ultrasonic viewing and inspection. Sodium compatible high temperature ultrasonic transducers are being developed for this application. Lead zirconate titanate (PZT) crystal is used as active element. Nickel (Ni) face plate is used to facilitate sodium wetting at low temperatures. Bonding of the PZT crystal to the nickel faceplate is carried out by soldering/diffusion bonding techniques. Bond quality is important as it influences the performance of the transducer. Ascertaining the bond quality would help in fabricating high quality transducers. We have used under water ultrasonic C-scan imaging technique to assess the bond quality. In order to develop the technique, studies have been performed on a few transducers using reference defects introduced at the interface. Bond quality of the diffusion bonded high temperature transducers has been checked before and after exposure to high temperatures and the results are discussed in this paper.

Keywords

Ultrasonic Transducer, C-Scan Imaging, Beam Profile.

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A. Joseph ¹, Govind K. Sharma ¹, B. Purnachandra Rao ¹, K. Nataraj ²

Affiliations
1 Nondestructive Evaluation Division, Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam-603102, IN
2 Department of Physics, National Institute of Technology, Trichy-620015, IN

Abstract

Low carbon steel is the most commonly used material for various applications because its cost is relatively low. Different methods are employed to reduce residual stresses in carbon steel weld joints. Post weld heat treatment (PWHT) is the most commonly used method to relieve/reduce the residual stresses. Use of different sequential weld passes during welding is one of the alternate methods used to get minimum residual stresses in higher thickness double 'V' carbon steel weld joints. A study was undertaken to nondestructively quantify the residual stresses present in carbon steel weld joints made using three different weld pass sequences. For this study, three sets of 20.0 mm thick low carbon steel double 'V' weld joints were fabricated with three different weld pass sequences using the Manual Metal Arc Welding (MMAW) process. Ultrasonic based residual stress measurements offer estimation of surface, sub-surface and bulk residual stresses. Details of critically refracted longitudinal (L_cr ) ultrasonic wave technique employed for residual stress measurements are discussed in this paper. The residual stress values of carbon steel weld joints obtained using the ultrasonic L_cr technique showed minimum longitudinal tensile residual stresses in the weld joints made by alternate weld pass sequence as compared to the other two weld pass sequences. The ultrasonic L_cr technique used is nondestructive, portable and low cost technique for residual stress measurements. This technique can also be used for in-situ measurement of residual stresses in operating components.

Keywords

Residual Stress, Ultrasonic Technique, Carbon Steel, Sequential Welding Passes.

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