The vehicle that loosens the wire and replaces the bolts accounts for 63% of the minor repairs and 76% of the temporary repairs. The lower core bolts are broken or loose, which may cause horizontal displacement of the vehicles or even a traffic accident. Therefore, to prevent the vehicle's lower core bolt from breaking or loosening should be one of the key prevention contents of vehicle safety.
Reason analysis (1) In the vehicle maintenance, there is no standard maintenance. Use <20mm bolt instead of <22mm bolt, the strength is not enough and there is gap, and it is easy to break under the impact of horizontal force.
(2) During the locomotive marshalling process of the cargo train, due to the improper handling of the driver, the impact force caused by the hanging is large, causing the bolt of the core plate to break; when the heavy truck slips into the empty car during the hump grouping, the empty car body is affected by the impact force. Causes the heart bolt to break.
(3) With the increase of the weight and speed of the train, the increase of the vehicle's length change and the poor quality of the line or the small curve radius are easy to cause the core bolt to break.
(4) The degree of tightness of the bolts of the lower core bolts during maintenance or operation is different, and the bolts that are too tight are easily broken.
(5) There is no fixed upper cap, nut anti-loose piece and open end pin on the core bolt hole. Looseness of the locknut during long-term operation can also cause the core plate bolt to break.
(6) Due to the high center of gravity of the boxcar, the swing is large during operation, and the horizontal impact force is large, resulting in a higher proportion of the bolts of the box heart bolt.
Suggestions for improvement (1) The clearance of each component in the design and manufacture of the truck should be strictly controlled to reduce the shearing force of the lower core bolt.
(2) In the process of vehicle overhaul, strictly follow the standard maintenance, and use standard bolts to strengthen the acceptance.
(3) Reduce the gap between the core pin and the center pin hole of the core plate, so that the heart pin round pin only bears the horizontal impact force and reduces the horizontal shear force of the core plate bolt.
(4) Use a torque wrench to control the tightening force of the bolt so that the core plate bolt is evenly stressed. In order to solve the problem of the looseness of the core plate bolt, the upper and lower fixing manners can be adopted to ensure that the lower core bolt does not loosen during long-term use of the vehicle.
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