Waveform characteristics When the spring has no defects, the ultrasonic wave is reflected inside the spring to form an ultrasonic channel in the spring. The ultrasonic wave will always propagate to the lower end face and be received by the probe. There are only the initial wave and the lower end face angle wave on the instrument. If there is a defect, part of the sound wave is reflected back by the defect during the propagation process of the ultrasonic wave and is received by the probe to form a defect wave, and the other part of the sound wave continues to propagate forward to the lower end of the spring, forming an end angle wave at the lower end. If there is a serious defect in the spring or If the material is poor, the sound waves are all reflected or scattered by the defects during the propagation of the ultrasonic wave, and the sound waves cannot continue to propagate to the lower end of the spring, and the initial wave and defect wave are displayed on the instrument.
The following issues should be paid attention to when using ultrasonic testing springs: ①Because the length of the locomotive’s secondary spring is 7.8m, the ultrasonic flaw detector’s transverse wave flaw detection range must be adjusted to be greater than or equal to 7.8m, so the analog instrument cannot be used for testing. For the spring, a digital ultrasonic flaw detector with a transverse wave flaw detection range greater than 8m must be used. ②The quality of the spring detected by this method is high in accuracy and the miss rate is small. However, in the detection, the ultrasonic wave forms an ultrasonic channel after multiple reflections, and there are both transverse waves and surface waves in the spring, so there is a certain error in defect location. .
Improvement measures ① To ensure that the branch circuits of the locomotive rectifier cabinet have good dynamic current sharing, the forward characteristics of the thyristors of each branch must be as consistent as possible. For this reason, the components of the locomotive rectifier cabinet must be strictly selected when getting off the train. , Detect the positive and negative characteristics of the components, pipe pressure drop and other parameters, and assemble according to the detection results, so that components with basically the same characteristics are assembled on the same bridge arm. At the same time, carry out the current sharing test of each bridge arm. The maximum and minimum current sharing coefficients must be greater than 0.85. For bridge arms that do not meet this requirement, replace the silicon components and adjust them until they meet the requirements. During minor repairs of the locomotive, use a portable current sharing tester to test the current sharing coefficient of each bridge arm of the full control bridge of the on-board rectifier cabinet, and adjust the replacement components less than 0.85. ②Add pulse connections to the thyristors of each bridge arm to eliminate the failure of individual thyristors to trigger when the original wiring is badly crimped. ③During the daily minor and auxiliary repairs of the locomotive, detect the resistance status of the traction winding RC overvoltage protection components, surge absorbers and each pulse box, and deal with the defective components in time. ④Flush the side wall filters of the locomotive regularly, and use a vacuum cleaner to remove dust from the ventilation ducts of the rectifier cabinet to ensure that the rectifier cabinet is well ventilated. In hot weather, the locomotive crew is required to put the silicon fan into use when there are less than 3 people in the driver controller, and must not be turned off to ensure good ventilation and heat dissipation of the rectifier cabinet.
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