An Ultrasonic Method for Determining Axial Stress in Bolts

An ultrasonic technique for determining the axial stress within a bolt was developed and experimentally verified. The technique uses time-of-flight measurements of both shear and longitudinal waves propagating along the axis of a bolt along with the material parameters to calculate the stress acting on the bolt. One significant advantage of the technique is that an independent measurement of neither the original nor present length is required. Experimental results suggest that the method may be usable for fasteners which have experienced a small amount of plastic deformation.