Rail bolt frame damage elements and pre-police
The basic principles and assumptions "vehicle-orbital vibrancy dynamics" have given P; and ar numerical calculation methods, but must rely on electronic computers, and can not theoretically reflect the impact of P; and From the point of view of maintenance and repair, as long as the factors affecting P and ar can be eliminated, the generation of screw hole cracks can be reduced without considering the size of Pl and ar. Therefore, it is necessary to make the following assumptions for the orbital system: (1) Assumption The track is rigidly supported and the wheels act as "exciting points".
(2) The track is only subjected to the vertical impact (because Pl and ar are mainly affected by the vertical impact), and the wheel is the impact load orbit as the impacted member, which satisfies the following assumptions: First, the impacted member is under the impact load Still obeying Hooke's law; second, the quality of the impacted components is small and negligible; third, no other energy losses are considered.
When two conditions (1) and (2) are satisfied, then P; and ar are simplified to the calculation of the impact force according to the energy method and the conservation of energy and the conversion principle, and the calculation of the vibration acceleration of the rail under the impact force. Pl and a, the calculation (l)P, the calculation of the rail joint is subject to the vertical impact of the wheel, the weight of the wheel is Q (including self-weight and load), and the impact velocity when the contact with the rail is Ur is calculated. For the object, the rail is subjected to the vertical impact force PI and the sleeper reaction force Frs. The vibration equation of the rail is: mrar=PI-Frs where mr is the rail mass, and the calculation principle of Frs is the same as P, then am is the wheel Self weight and load mass, Kp is the underlay cushion fastener and sleeper stiffness.
According to the "Vehicle-Axis Coordination Dynamics", the joint of the ordinary line is the most important source of the disturbance of the wheel-rail system. When the wheel passes the joint rail joint, the joint is budded, and the joint is low, the sudden change of the center of the wheel is instantaneously changed. , causing the wheel to produce a vertical downward impact velocity to the track, and when the wheel leaves these parts, the impact speed disappears immediately, and the impact speed is. 0, the calculation of the joint part u. uses the formula listed in "Vehicle-Operational Occurrence Dynamics".
Factors affecting p, and al can be found in the following equations (l) and (2): (1) P, and ar with axle weight, velocity and disturbance (such as joint rail joints, The growth of erroneous buds, low buckles, peeling off blocks, etc.) is almost unconditional. The increase in P: and ar increases the probability of occurrence of screw hole cracks in the rails. This can be confirmed from the statistics of the above lines.
(2) P, and ar increase linearly with the speed of the vehicle, which is consistent with the conclusion of "Vehicle-Track Accidental Dynamics". (3) The disturbances in the orbit (such as rail joints, low joints, wrong buds, peeling off blocks, etc.) are the fundamental factors that cause P, and ar. P, and ar are linearly increasing with the value of the disturbance. There is no shock and vibration without disturbance, and the source of the disturbance of the control track is the key to controlling P and ar.
(4) P. The steel mass increases slightly with the increase of the rail, while ar decreases slightly. This is consistent with the relevant conclusions. From the above statistics, it can be confirmed that the number of P60 rail screw crack rails is larger than the number of P50 rails. (5) The rigidity of the track system K has a great influence on P. The larger K is, the smaller the 6j is, the larger the impact force is, and the smaller the impact force is. K is related to the stiffness of the pad, the stiffness of the track bed and the stiffness of the subgrade. Affected by temperature changes, K will change. The overall stiffness of the track in winter is greater than the track stiffness in summer. In winter, the joint P: is greater than the summer. Therefore, the probability of screw hole cracking in winter rails is higher than that in summer. The above statistics can confirm this. a little.
(6) The rigidity of the under-slab pad KP has a great influence on a. If the track has a dynamic type, the joint fastener is loose, broken, and the sleeper is invalid. At this time, the KP is increased by 0, ar, and the vibration of the rail is intensified. The probability of occurrence of screw hole crack increases, such as the existence of dark pits or empty cranes in different states, p, ar value joint state P-ar remarks joint rail joint L. + (1 + r. sleeper vibration is intensified, can cause fastener loose Detachment, breakage, sleeper crack failure, etc., will aggravate the vibration of the rail and cause the same consequences.
(7) The volume and wheel radius have a great influence on P and ar. The traffic volume is large, the wheel radius (the truck wheel is smaller than the passenger car wheel), Pl and a. are larger, and the probability of the screw hole crack appearing in the rail is high. If the downstream traffic volume of the Beijing-Kowloon Railway is greater than the uplink, the number of spiral-hole cracked rails is larger than the upward trend. Although the loop-to-line speed is not high, the number of trucks is large, the traffic volume is large, and the probability of the screw hole crack appearing on the rail is higher than that of the Huaihuai line and the green line.阜 line. Based on the above analysis, in terms of the track structure, the factors of the screw hole crack of the rail can be attributed.
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