Performance Comparison of Ultrasonic Focusing Techniques for Phased Array Ultrasonic Inspection of Dissimilar Metal Welds

  • Young-In Hwang
  • Jinhyun Park
  • Hak-Joon KimEmail author
  • Sung-Jin Song
  • Yong-Sang Cho
  • Sung-Sik Kang
Regular Paper


Dissimilar metal welding that is the joining of two different metals which would not be welded together has been used in nuclear power plants so that the probability of occurrence of cracks that can cause serious accidents is high. Therefore, it is necessary to diagnose and investigate structures with dissimilar metal welds through nondestructive testing techniques. Among them, nondestructive evaluation techniques using phased array ultrasonic waves have been widely used and studied. However, transmitted ultrasound into dissimilar metal welds is split, skewed and distorted due to course grained anisotropy and inhomogeneity. Therefore, there are many limitations in tests using the conventional phased array ultrasonic technique. In this study, the phased array ultrasonic focusing methods such as phase matching method, adaptive focusing method and time reversal method were applied to the nondestructive ultrasonic testing of dissimilar metal welds for detecting internal cracks, and the performance and efficiency of each technique were compared through numerical simulations and experiments.


Dissimilar metal welds Focusing ultrasound Phased array ultrasonic testing 

List of Symbols


Index of the array element


Time delay for the \({\text{n}}\)-th phased array element


Focal length from the center of the array


Sound velocity of material


The number of elements


Center-to-center spacing between elements


Steering angle from the center of the array






First received signal


\({\text{n}}\)-th Received signal



\({\text{K}}\left( \omega \right)\)

Transfer matrix


Eigenvectors of \({\text{K}}\left( \omega \right){\text{K}}\left( \omega \right)^{*}\)


Diagonal positive semi-definite matrix


Eigenvectors of \({\text{K}}\left( \omega \right)^{*} {\text{K}}\left( \omega \right)\)



This research was supported by Korea Electric Power Corporation (Grant Number R15GA12).


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Copyright information

© Korean Society for Precision Engineering 2019

Authors and Affiliations

  • Young-In Hwang
    • 1
  • Jinhyun Park
    • 1
  • Hak-Joon Kim
    • 1
    Email author
  • Sung-Jin Song
    • 1
  • Yong-Sang Cho
    • 2
  • Sung-Sik Kang
    • 3
  1. 1.School of Mechanical EngineeringSungkyunkwan UniversitySuwonSouth Korea
  2. 2.Korea Electric Power Research InstituteDaejeonSouth Korea
  3. 3.Korea Institute of Nuclear SafetyDaejeonSouth Korea

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