Study On Ultrasonic Flaw Detection Technology Of Large Load Bearing Bolt

Heavy load bearing bolts are often used as key fasteners for systems such as wind turbines,bridges,and steam turbines.In the operation of equipment for a long time,due to temperature changes and the role of high stress,the bolt prone to creep,fatigue and other problems;then lead to local cracks in the bolt,will produce serious fracture,seriously endangering equipment and personnel safety,therefore It is of great significance to strengthen the nondestructive testing of large load bearing bolts.Ultrasonic testing has strong penetrating power,good direction,high energy,harmless to human body and so on,it is feasible to detect the defects of bolts.This paper mainly focuses on the key technology of ultrasonic testing for large load bearing bolts.Summarizes the common defects of the bolt and the causes of the defects,determinedthe testing method of large load bearing bolts,and designed the digital ultrasonic flaw detection system.A common problem with bolts is that the internal cracks and breaks of the bolts occur after a certain period of operation.The cracks or fractures are mainly caused by the long-term effects of transverse forces and longitudinal forces of different sizes and angles.The bolt defect detection method for the use of direct probe,oblique probe pulse reflection method.Bolt digital ultrasonic flaw detection system consists of upper computer and lower computer.The upper computer achieves the man-machine interface dialogue through the VB6.0 operation contact surface,to complete the bolt flaw detection and treatment;The lower machine contains the ultrasonic flaw detection system transmitting module,receiving module,6MHz data acquisition module,ultrasonic waves are produced by the transmitting module,ultrasonic waves emitted to the bolt internal echo signal,receiving module processes the echo signal,after processing the signal will be transmitted into the data acquisition module,converted to digital signals,the signal storage time-sharing and sent to the host computer;Using USB communication protocol between the host computer and the next machine data transmission.In this paper,a large load bearing bolt is used as the object,during the experiment,the experiment,such as system calibration,resolution detection and blind spot detection,were carried out to test block and bolt.Accurately qualitative and detecting artificial defects of test blocks and bolts,The feasibility of ultrasonic flaw detection system for the detection of internal defects of bolts is verified.