Influence of Material Coating on Stress Measurement by Ultrasonic Surface Wave (Part 1)

Ultrasonic surface wave have been implemented to measure or predict the existing stress on material. Surface wave velocity shows linearly increase with stress applied in material. However, various applications were coated their surfaces with high corrode resistance material for example paint or aluminum thermal sprays. It may cause the change of the velocity of surface wave and lead to miss prediction. This paper presents the effect of material coating on surface wave velocity and its attenuations. Paint and Aluminum thermal spray coated on low carbon steel graded S420 (EN 10025 Standard) in the range of 100-500 micron. Through transmission ultrasonic surface wave was applied to measure the velocities change. Their frequencies are 2.25 and 5 MHz respectively. It was found that coating thickness show effect on sound velocity and sound wave attenuation. The benefit is to know the effect of coating and to approve the accuracy of stress measurement by ultrasonic wave.