Study on the Influencing Factors of Ultrasonic Measurement of Cable Clamp Bolt Preload

This paper addresses the problem of ultrasonic wave velocity being affected by many factors during tests of cable clamp bolt preload in suspension bridge cable clamps. A refined finite element model of the bolt was established based on acoustoelasticity theory. Finite element software was used to run steady-state and transient simulations. These simulations study how stress level, clamping length, and stress non-uniformity length affect ultrasonic measurements. Full-scale experiments were also conducted to validate the finite element simulations. The study shows that stress levels do not affect ultrasonic wave velocity. For materials with high elastic modulus, the effects of stress levels on ultrasonic waveforms, vibrations, and displacements can be ignored. Increasing the bolt’s clamping length and the stress non-uniformity length both reduce wave velocity. When the relative ratio of stress non-uniformity length is between 0.08 and 0.087, the change in wave velocity is very small. Full-scale bolt stress-wave velocity experiments confirm that within a stress range of 0–243 MPa, the change in wave velocity is only 0.18% of the average, and its direct impact can be ignored in practice.