| Flange fasteners are common interceptor sealing devices in transportation pipelines.Due to their service environment and long service life,defects such as corrosion and contact interface separation will occur inside the flange fastening device with silicone gaskets,so health inspection of flange fasteners is necessary to ensure the safety of pipeline transportation.Ultrasonic phased array inspection technology has several advantageous technologies such as focusing,deflection,high energy and multiple display modes,and has been widely used in the field of nondestructive testing of pipeline engineering in recent years.Phased-array ultrasound is used regularly in engineering applications to monitor the health of service flange fastening status,and is dedicated to improving the stability and safety of oil and gas pipelines.Using the high sensitivity and high signal-to-noise ratio of ultrasonic phased array for detecting defects in complex components,we analyze the influence of silicone gasket defect size and its contact state on the ultrasonic echo signal of phased array in flange fastening device,and thus carry out finite element simulation and experimental verification,based on which the following three aspects of research work are carried out.(1)The ultrasonic phased-array transducer array parameters design,through Matlab numerical simulation to compare and analyze the array frequency,number of elements,array spacing and focal distance and other parameters on the phased-array ultrasonic field deflection and focusing performance,combined with the flange fastening device material properties and size structure to finally determine the selection of the detection probe model.(2)We analyzed the defect form of seal gasket during the service of flange fastening device and established finite element model.With the help of COMSOL finite element simulation software,the trend of the phased array ultrasonic time domain echo signal changes under different degrees of corrosion size and contact interface separation were investigated,and the delayed superposition of the echo signal of each array element was processed to greatly improve the defect detection rate and accuracy,and the inspection platform was combined to verify.(3)The ultrasonic phased-array experimental testing platform was built to guide the detection of defects in the flange fastening device according to the finite element simulation.The experimental results show that when the bolts in the flange fastening device are clamped,there is an obvious relationship between the defect size in the silicone gasket and the amplitude of the phased-array ultrasonic echo signal;when the flange fastening device is clamped and unclamped,the echo signal of the contact interface between the flange cover and the intact silicone gasket is measured,considering that under the clamped condition,the acoustoelastic effect caused by the deformation of the silicone gasket leads to the change of the echo amplitude.(4)To further evaluate the contact interface(4)To further evaluate the separation state of the contact interface,the relationship curves between different air thicknesses and their first-order resonant frequencies under vertical incidence conditions are derived with reference to theoretical equations of acoustic properties such as ultrasonic reflection coefficients of the contact interface,and the relationship equations of the first-order resonant frequencies with air layer thickness under multi-angle incidence conditions are further resolved. |
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