Characterization of contact condition in a flange connection by longitudinal waves

Mechanical Engineering Journal

Kanami YAMAMOTO¹  Hideo CHO¹  Kojiro NISHIMIYA¹  Hiroaki ITO² 

[1] Collage of Science and Engineering, Aoyama Gakuin University;Faculty of Engineering, Kindai University;

关键词: contact condition;    instantaneous frequency;    ultrasonic measurement;    numerical calculation;   

DOI  :  10.1299/mej.17-00568

来源: DOAJ

【 摘 要 】

The integrity of flange joints is critical in all pipe systems. To test this integrity, an ultrasonic method characterizing the condition of the flange joint would be a vital tool. In this study, we analyzed the contact conditions on a metal/gasket/metal connection. The instantaneous frequency profile, i.e., the phase change of the wave with time for longitudinal waves transmitted in an Al alloy/gasket/Al alloy system, was evaluated under various contact pressures. The instantaneous frequency (IF) was calculated with a complex continuous wavelet transform with a modified Morlet function as a mother wavelet. The maximum IF of the waves monotonically increased with contact pressure, showing similar properties as the amplitude of the waves. A one-dimensional numerical calculation with a finite difference time domain method with a spring condition for expressing various contact conditions or contact stiffness revealed that a large phase delay of the transmission wave was generated at a low contact stiffness interface, and the amount of delay was correlated with the contact stiffness. On the other hand, the delay in the reflected wave was very small.

【 授权许可】

Unknown