title: Bolt axial stress measurement based on a mode-converted ultrasound method using an electromagnetic acoustic transducer.
abstract: A method is proposed to measure the stress on a tightened bolt using an electromagnetic acoustic transducer (EMAT). A shear wave is generated by the EMAT, and a longitudinal wave is obtained from the reflection of the shear wave due to the mode conversion. The ray paths of the longitudinal and the shear wave are analyzed, and the relationship between the bolt axial stress and the ratio of time of flight between two mode waves is then formulated. Based on the above outcomes, an EMAT is developed to measure the bolt axial stress without loosening the bolt, which is required in the conventional EMAT test method. The experimental results from the measurement of the bolt tension show that the shear and the mode-converted longitudinal waves can be received successfully, and the ratio of the times of flight of the shear and the mode-converted longitudinal waves is linearly proportional to the bolt axial tension. The non-contact characteristic of EMAT eliminates the effect of the couplant and also makes the measurement more convenient than the measurement performed using the piezoelectric transducer. This method provides a promising way to measure the stress on tightened bolts.
authors.affiliation: School of Mechanical Science & Engineering, Huazhong University of Science and Technology, Wuhan 430074, China. Electronic address: dingsugar@163.com.
authors.forename: Xu
authors.initials: X
authors.lastname: Ding
authors.affiliation: School of Mechanical Science & Engineering, Huazhong University of Science and Technology, Wuhan 430074, China. Electronic address: xinjunwu@mail.hust.edu.cn.
authors.forename: Xinjun
authors.initials: X
authors.lastname: Wu
authors.affiliation: School of Mechanical Science & Engineering, Huazhong University of Science and Technology, Wuhan 430074, China. Electronic address: bdxyzwyg@163.com.
authors.forename: Yugang
authors.initials: Y
authors.lastname: Wang
mesh_terms: D055119:Elastic Modulus; D004581:Electronics / Q000295:instrumentation*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D008420:Manufactured Materials / Q000032:analysis*; D055617:Micro-Electrical-Mechanical Systems / Q000295:instrumentation*; D033081:Shear Strength; D013314:Stress, Mechanical; D013718:Tensile Strength; D014159:Transducers; D014463:Ultrasonography / Q000295:instrumentation*
keywords: Acoustoelasticity; Bolt axial stress; Electromagnetic acoustic transducer; Mode conversion; Time of flight