Investigation Of Ultrasonic Water Immersion Flaw Testing Of 25 Mm In Diamater TC4 Alloy Bars

III Ultrasonic nondestructive testing technology was a very important and widely used nondestructive testing technology,it combined closely with modern computer technology,automation technology and information technology,which greatly improves the accuracy and reliability.Ultrasonic water immersion testing was one of the methods of ultrasonic testing,which had many advantages,such as reliable test result,high sensitivity and strong ability to test small defects.Recently,with the development of ultrasonic testing instruments manufacturing technology,the improvement of the bandwidth of instruments,the speed of data obtaining and the manufacture process of probe,high frequency probe and high-resolution probe were widely used in the testing process.However,the relevant standards at home and abroad had failed to meet the requirements of higher sensitivity for small size bars.The testing parameters of ultrasonic water immersion testing for TC4 alloy 25 mm in diameter bars were investigated,the defect testing ability was improved,which guaranteed the authenticity and stability of the testing results.Cylindrical and spherical focusing probes with different frequencies,chip diameters and focal length dimensions were used to test TC4 alloy 25 mm in diameter contrast samples,and the relations of sensitivity,water path and signal-to-noise ratio(SNR)of cylindrical focusing probes were analyzed systematically,the best parameters of probes and contrast samples in ultrasonic water immersion testing of TC4 alloy 25 mm in diameter bars were determined.The ultrasonic water immersion flaw testing system of JL-LBCS4 small size bars was designed and manufactured with determined probe and sample parameters,and the matching of the water path,repetition frequency(RPF)and probe speed of TC4 alloy 25 mm in diameter bars was investigated with this system.The main conclusions are as follows:(1)For TC4 alloy 25 mm in diamater bars,the best probe is a cylindrical focusing probe with a frequency of 15 MHz,a wafer diameter of 0.25 ",and a focus of 1.0".(2)Materials of the samples for ultrasonic testing of TC4 alloy 25 mm in diamater bars should be homogeneous or similar,and the minimum diameter of the contrast samples is 22 mm in diamater,the maximum diameter is 28 mm in diamater.(3)Under the water path of 11 to 13.5 mm,with the JL-LBCS4 small size bars ultrasonic immersion testing system and the 15MHz/0.25 "/1.0" cylindrical focusing probe,the best parameters are: the testing speed is 1 500 mm/min,the probe speed is greater than 1000 RPM,and the repetition frequency is not less than 1 800 Hz,the testing sensitivity is moderate and the signal-to-noise ratio is the best.