Determination of connecting rod bolt comparison test block table and coupling agent In the test, we found surface wave interference due to copper plating. For this purpose, a soft foam capable of sucking oil was added to the box workbench to place the inspected workpiece. On the soft foam, not only the surface wave interference disappears, but also the coupling agent is evenly spread. The couplant is selected for normal engine oil. The first phase of the implementation of the program: the choice of instrument selection TZ-2 digital ultrasonic flaw detector. The main performance of the instrument is as follows: (1) Full Chinese display, scrolling operation, friendly man-machine interface, easy to learn and use. (2) It has automatic gain adjustment, automatic memory and automatic search for maximum echo function, which is convenient and practical. (3) With local widening function, the range in the gate can be enlarged to full screen at any time, and the sensitivity is adjustable, which greatly improves the resolution and is convenient for observation and analysis. (4) The long-term storage capacity of 400 echo waveforms and flaw detection reports makes field operations more convenient. (5) Wide temperature environment of -20 ° C ~ +40 ° C. The second stage: the production of the physical test block is made with the same new connecting rod bolt as the locomotive. (1) The threaded portion is made to have a 0.2 mm deep artificial injury in the second buckle. (2) The shaft part is not buckled to make a 0.2mm deep artificial injury. The third stage: the production of the workbench and the coupling agent and the determination of the workbench. Make a rectangular work box with non-metallic materials, put the corresponding size of the foam into the box, and then pour the clean ordinary oil into the box to make the foam. Filled with oil, place the bolt on the oil tank and let the screw contact the foam for a quarter of a week. In the case of flaw detection, one hand turns the bolt and the other hand holds the probe for the flaw detection. Determination of Coupling Agent The choice of oil as a coupling agent is due to the fact that the oil is easily attached to the surface of the test piece and has sufficient wettability to eliminate the thin layer of air between the probe and the test surface due to the surface roughness of the test piece. The price of oil is low and economical compared to other coupling agents. The fourth stage: the selection of the probe selects the straight probe (1) to test the physical test block with a 2.5MHz, D14 straight probe. In the actual measurement, it is found that the straight probe detects 0.2mm crack at the end of the bolt, and the crack wave pattern and the thread shape The contrast between high and low is not obvious, and the judgment is too difficult. (2) The straight probe blind area is large. Because the geometry of the bolt end is not standardized, the ultrasonic wave is easy to generate irregular reflection here, and the waveform is complicated, so it is not easy to make accurate judgment on the defect. Selecting the oblique probe (1) calculates the transverse wave refraction angle of 64° according to the geometry of the connecting rod bolt thread portion. Since the bolt surface is plated with copper, the refraction angle becomes smaller by 2° to 4°. (2) The non-deducting probe angle of the bolt is smaller, and the refraction angle is better than 50°; (3) the sound field is diverged by the ordinary oblique probe, and the resolution is low. Focusing on the sound field of the focusing probe, the ability to find defects is strong, and the signal-to-noise ratio is good. The fifth stage: the test part of the threaded part: select the oblique probe (1) to select the angle probe of the 64° refraction angle, and adjust the instrument to make the instrument parameter selection consistent with the probe. The shear wave scanning speed is adjusted by the horizontal adjustment method. (2) Select A sweep during the test and adjust the gate to the narrowest. Hold the first wave of the thread and press the partial zoom button. The 18 thread waveforms are clearly visible. Press the Enter key to exit, press the up arrow key to calibrate. The function enters the scan, raises the first wave of the thread to 30% of the full screen, finds the maximum wave, and presses the Enter key to automatically remember the instrument. (3) According to the statistical result of the broken part of the connecting rod bolt for several years, the general broken area is between the first buckle and the fourth buckle. The bolt thread has a total of 18 buckles. No ultrasonic flaw detection will cause leakage. The probe wire does not need a test block. As long as the thread is adjusted to 30% of the full screen, there is a crack of 0.2mm. The signal-to-noise ratio will be More than 9dB. If the second buckle is injured, the third buckle wave disappears, and so on, we put the oblique probe on the connecting rod shaft to detect the second buckle 0.2mm artificial injury, use the above method for flaw detection, and find the third thread buckle The wave disappears. After repeated trials and tests, this method is accurate. Therefore, in daily inspection, thread fasteners can be used for flaw detection sensitivity, that is, all the bolts 18 are buckled out, which buckle is injured, and the reflected wave of the latter buckle disappears or the wave height is reduced to more than 50% of the set wave height. It is best to test the 64° probe. The non-buckle part of the non-buckle end is debugged on the non-threaded side of the test piece by 0.2mm, that is, the wave height is adjusted to 80%, and then 3dB is released as the detection sensitivity. Because the bolt is fixed in size and position, it is within the set range. The wave is the wave of injury. Crack and non-crack analysis of connecting rod bolts (1) There is no damage at the end of the thread, and the waveform is as shown. (2) There is injury at the end of the thread, and the waveform is as shown. (3) Non-deductible without damage, the waveform is as shown. Conclusion Through several years of practice, it is shown that the use of new ultrasonic technology and new methods to detect cracks in connecting rod bolts is a very practical and effective method. The implementation of this project prevented the locomotive failure and the resulting economic loss caused by the fatigue fracture of the connecting rod bolt. It provides a reliable guarantee for the safe operation of locomotives, and at the same time creates safety, social and economic benefits for railway transportation. Auto Led Headlight,Led Headlights For Cars,Led Headlamp For Car,Automotive Led Headlights CHANGZHOU CLD AUTO ELECTRICAL CO.,LTD , https://www.cld-leds.com
Use new procedures, new techniques to inspect bar bolts
Determination of connecting rod bolt comparison test block table and coupling agent In the test, we found surface wave interference due to copper plating. For this purpose, a soft foam capable of sucking oil was added to the box workbench to place the inspected workpiece. On the soft foam, not only the surface wave interference disappears, but also the coupling agent is evenly spread. Coupling agent selection