A Study on the Failure Analysis of M10 Bolt Caused by Prefabricated Cracks Based on Ultrasonic Method

Petroleum bolts are important connection points for various key parts of oil wellhead blowout preventers. Bolted connections are prone to loosening, deformation, defects, and even fractures in the oil well environment, which can cause adverse consequences to the wellhead blowout preventer. Ultrasonic testing is a nondestructive testing method widely used in metal material testing. This experiment uses M10 bolts as test samples, then will use wire cutting equipment to simulate the damage of bolts in a cutting form, simulate the prefabricated cracks of bolts, and then use piezoelectric chips pasted on the bolt head to collect ultrasonic signals. Three different devices, including ordinary ultrasonic emission and reception equipment, nonlinear ultrasonic, and UA-360 ultrasonic wave detection equipment, will be used, and different load forces will be applied to the bolts using an electronic universal tensile testing machine, By collecting ultrasonic signals before and after prefabricated bolt cracks, as well as under different axial stresses, the relationship between external load and prefabricated bolt cracks on accelerating bolt failure can be identified. And at the same time, the macroscopic morphology and microstructure of the bolt fracture were analyzed. Through the analysis of the bolt cross-section image, it can be concluded that the failure of the bolt is all affected by the prefabricated cracks.