Measurement of stress in bolts using resonant ultrasound spectroscopy

Abstract

Stress affects the resonance properties of materials. A suitable technology and instrumentation for calculating stress in pre-installed oil pipeline bolts is developed and tested. The technology, Resonant Ultrasound Spectroscopy (RUS), relates the change in bolt resonances to bolt stress, using analysis software. A suitable instrumentation that excites the bolt over a band of frequencies through a broad band sweep and measures the response to compute resonances and bolt stress is developed. The instrumentation and the analysis software operate in a loop with minimum operator input to predict stress in the bolts. The project is primarily aimed at the oil and gas industry but has the potential to fit bolt-testing applications in aerospace, defence and manufacturing industries. The proposed testing method is new to Non Destructive Testing (NDT) of oil pipeline bolts and has no peers. A calibration data set is built using the resonance information extracted from a set of bolts. Test results are discussed and areas of future work explored. A stress prediction accuracy of = 20% has been achieved with a group of 10 B7 bolts. This project is a Knowledge Transfer Partnership (KTP) project and was done at Hedley Purvis Ltd., in association with Durham University.