阅读说明：本技术 一种基于钢轨模态整体变化测量锁定轨温的方法 (Method for measuring locked rail temperature based on overall change of steel rail mode ) 是由 岳国栋 董京 于 2021-06-25 设计创作，主要内容包括：一种基于钢轨模态整体变化测量锁定轨温的方法,解决现有技术中存在的受人为因素干扰大,无法忽略轨道参数变化对钢轨自振频率影响的问题。该方法通过模态实验建立纵向力与钢轨模态间的映射关系,形成关系数字字典,在服役钢轨上选择任意区域进行模态实验,得到钢轨的多阶振动模态；并把实测钢轨振动模态与数字字典中零纵向力下的钢轨模态进行匹配,进而计算出钢轨纵向力,最终测得钢轨锁定轨温。该测量锁定轨温的方法利用钢轨模态的整体变化可以消除轨道参数的影响,极大限度地降低利用钢轨振动特性测量纵向力的工作量。其操作简单,不受轨道参数影响,无需破坏现有轨道的结构稳定性,高效可行,计算精确,适用范围广。(A method for measuring locked rail temperature based on overall change of rail mode solves the problems that in the prior art, interference by human factors is large, and influence of rail parameter change on rail natural vibration frequency cannot be ignored. The method comprises the steps of establishing a mapping relation between longitudinal force and steel rail modes through a modal experiment, forming a relation digital dictionary, and selecting any region on a service steel rail to perform the modal experiment to obtain multi-stage vibration modes of the steel rail; and matching the actually measured vibration mode of the steel rail with the steel rail mode under the zero longitudinal force in the digital dictionary, further calculating the longitudinal force of the steel rail, and finally measuring the locking rail temperature of the steel rail. The method for measuring the locked rail temperature can eliminate the influence of rail parameters by utilizing the overall change of the rail mode, and greatly reduces the workload of measuring the longitudinal force by utilizing the vibration characteristic of the rail. The method is simple to operate, free of influence of track parameters, free of damage to structural stability of the existing track, efficient, feasible, accurate in calculation and wide in application range.)

1. A method for measuring locked rail temperature based on overall change of rail mode is characterized by comprising the following steps: the method comprises the following steps:

firstly, carrying out modal experiments on the steel rail under different longitudinal forces;

establishing a mapping relation between longitudinal force and steel rail modes to form a relation digital dictionary;

selecting any region of the serving steel rail to perform a modal experiment;

step four, matching the actually measured steel rail mode with the mode in the digital dictionary;

step five, calculating the longitudinal force of the steel rail;

and step six, acquiring the locking rail temperature of the steel rail.

2. The method for measuring the locked rail temperature based on the overall change of the steel rail modal according to claim 1, wherein the method comprises the following steps: the method comprises the following steps that firstly, when a modal experiment is carried out, a vibration sensor is arranged on a steel rail, a vibration signal is obtained through excitation, and the self-vibration frequency above 500Hz is obtained through frequency domain analysis; the mode experiment needs to measure the rail modes of the rail above 500Hz and as many as possible, including frequency, damping and vibration mode.

3. The method for measuring the locked rail temperature based on the overall change of the steel rail modal according to claim 1, wherein the method comprises the following steps: according to the linear relation between the longitudinal force and the change value of the natural frequency, the sensitivity coefficient of each order of frequency to the longitudinal force is obtained through linear fitting, so that the mapping relation between the longitudinal force and the steel rail mode is established, and a relation digital dictionary is formed; and the digital dictionary comprises modal frequency, damping and vibration mode, sensitivity coefficient of each order of frequency to longitudinal force change, sensor layout scheme, steel rail model, track radius and other information.

4. The method for measuring the locked rail temperature based on the overall change of the steel rail modal according to claim 1, wherein the method comprises the following steps: and step three, measuring the mode of the same order as that in the digital dictionary through the mode experiment of any region of the service steel rail, wherein the type, the track radius and the sensor layout scheme of the service steel rail are the same as those in the digital dictionary.

5. The method for measuring the locked rail temperature based on the overall change of the steel rail modal according to claim 1, wherein the method comprises the following steps: step four, comparing the measured steel rail mode with the mode in the digital dictionary to realize the same mode matching; the successfully matched modes are regarded as the same-order modes; the differences are caused only by rail parameters, longitudinal forces, etc.

6. The method for measuring the locked rail temperature based on the overall change of the steel rail modal according to claim 1, wherein the method comprises the following steps: step five, after the mode matching is successful, solving the change value of the mode frequency of each order, calculating the average sensitivity coefficient of the mode to the locking rail temperature and force, and calculating the longitudinal force of the steel rail by using a longitudinal force formula;

the longitudinal force formula is:

F_{longitudinal direction}Represents the longitudinal force, and the specified pull is positive and has a unit kN; f. of_iThe measured ith order modal frequency is expressed in Hz after the matching is successful; f. of_{Logo i}Representing the corresponding order modal frequency in the digital dictionary after successful matching, wherein the frequency is the frequency of the steel rail with zero tension and is in Hz; n represents the number of successfully matched modes, the value is not less than 12, and the larger the value of the number is, the more the result isThe accuracy is high;representing the average sensitivity coefficient of the mode to longitudinal force after successful matching, unit Hz/kN, determined by equation (2); in formula (2), K_iAnd the sensitivity coefficient of the ith-order mode after the matching is successful to the longitudinal force is expressed in Hz/kN.

7. The method for measuring the locked rail temperature based on the overall change of the steel rail modal according to claim 1, wherein the method comprises the following steps: step six, calculating temperature rise according to the longitudinal force of the steel rail, and calculating the temperature of the locked rail by combining the current temperature of the steel rail;

the formula for calculating the locked rail temperature is as follows:

T_{lock with a locking mechanism}The locking rail temperature of the steel rail is measured in units; t is_{Temperature of rail}The current steel rail temperature is expressed in unit; e is the elastic modulus of the steel rail, unit MPa; alpha is the thermal expansion coefficient of the steel rail, and the unit is 1/DEG C; a is the cross-sectional area of the rail in m²。

Technical Field

The invention belongs to the technical field of steel rail health detection, and particularly relates to a method for measuring locked rail temperature based on steel rail modal integral change, which is simple to operate, free from the influence of rail parameters, free from damaging the structural stability of the conventional rail, efficient, feasible, accurate in calculation and wide in application range.

Background

Along with the improvement of the running speed, the train is required to have better stability and safety, and the seamless track steel rail becomes the main track form of the current track line. However, because the steel rails are laid in the field all the year round, the temperature difference all the year round is large, and under the impact force of the wheel rails, large longitudinal force can be gathered inside the steel rails. If the longitudinal tension is too large, rail breakage can be caused; and the longitudinal pressure is too large, so that the rail expansion runway is caused. The conversion relation between the locking rail temperature and the longitudinal force is an important index for measuring the safety of the steel rail.

The method for measuring the longitudinal force of the steel rail mainly comprises two methods, namely destructive detection and nondestructive detection. Destructive testing, including saw-track, drilling, and transverse stressing, can compromise the stability of existing tracks. Nondestructive testing includes pile observation, rail length calibration, Barkhausen, X-ray, ultrasonic guided wave, strain, rail temperature measurement, and vibration. The observation pile method and the rail length calibration method are greatly influenced by human factors and cannot measure longitudinal force in a short interval; the Barkhausen method, the X-ray method and the ultrasonic guided wave method are greatly influenced by the grain size of the steel rail material, surface rusty spots, the environmental temperature and the like, only the surface or shallow surface stress of the steel rail can be measured, and the longitudinal force of the steel rail cannot be accurately measured due to the uneven stress of the cross section of the steel rail; the strain method can only measure the relative value of the surface stress of the steel rail; the rail temperature measurement method can only measure the relative value of the longitudinal force of the steel rail, and the error is larger and larger along with the time. In addition, the vibration method firstly measures the change of the natural vibration frequency by utilizing the linear relation between the longitudinal force of the steel rail and the natural vibration frequency, and then calculates the longitudinal force of the steel rail; however, the natural frequency of rail vibration is also affected by boundary conditions including clip spacing, clip stiffness, etc.

In the prior art, a model with the same structure as a serving steel rail is expected to be established, a theoretical value of the natural frequency under zero longitudinal force is obtained, and the natural frequency change value only related to the longitudinal force is obtained by measuring the natural frequency of the serving steel rail. However, even if the model identical to the service track structure is technically feasible to establish, the track structures in different sections are different, and the workload of the established model is huge in order to measure the longitudinal force of the steel rail in any section, so that the theoretical method is not feasible to project. Therefore, there is a need for an improved method of measuring the longitudinal force of a steel rail.

Disclosure of Invention

Aiming at the problems, the invention provides the method for measuring the locked rail temperature based on the overall change of the rail mode, which is simple to operate, free from the influence of rail parameters, free from damaging the structural stability of the conventional rail, efficient, feasible, accurate in calculation and wide in application range.

The technical scheme adopted by the invention is as follows: the method for measuring the locked rail temperature based on the overall change of the steel rail mode comprises the following steps:

firstly, carrying out modal experiments on the steel rail under different longitudinal forces;

establishing a mapping relation between longitudinal force and steel rail modes to form a relation digital dictionary;

selecting any region of the serving steel rail to perform a modal experiment;

step four, matching the actually measured steel rail mode with the mode in the digital dictionary;

step five, calculating the longitudinal force of the steel rail;

and step six, acquiring the locking rail temperature of the steel rail.

The method comprises the following steps that firstly, when a modal experiment is carried out, a vibration sensor is arranged on a steel rail, a vibration signal is obtained through excitation, and the self-vibration frequency above 500Hz is obtained through frequency domain analysis; the mode experiment needs to measure the rail modes of the rail above 500Hz and as many as possible, including frequency, damping and vibration mode.

According to the linear relation between the longitudinal force and the change value of the natural frequency, the sensitivity coefficient of each order of frequency to the longitudinal force is obtained through linear fitting, so that the mapping relation between the longitudinal force and the steel rail mode is established, and a relation digital dictionary is formed; and the digital dictionary comprises modal frequency, damping and vibration mode, sensitivity coefficient of each order of frequency to longitudinal force change, sensor layout scheme, steel rail model, track radius and other information.

And step three, measuring the mode of the same order as that in the digital dictionary through the mode experiment of any region of the service steel rail, wherein the type, the track radius and the sensor layout scheme of the service steel rail are the same as those in the digital dictionary.

Step four, comparing the measured steel rail mode with the mode in the digital dictionary to realize the same mode matching; the successfully matched modes are regarded as the same-order modes; the differences are caused only by rail parameters, longitudinal forces, etc.

Step five, after the mode matching is successful, solving the change value of the mode frequency of each order, calculating the average sensitivity coefficient of the mode to the locking rail temperature and force, and calculating the longitudinal force of the steel rail by using a longitudinal force formula;

the longitudinal force formula is:

F_{longitudinal direction}Represents the longitudinal force, and the specified pull is positive and has a unit kN; f. of_iThe measured ith order modal frequency is expressed in Hz after the matching is successful; f. of_{Logo i}Representing the corresponding order modal frequency in the digital dictionary after successful matching, wherein the frequency is the frequency of the steel rail with zero tension and is in Hz; n represents the number of successfully matched modes, the value is not less than 12, and the larger the number value is, the more accurate the result is; k represents the average sensitivity coefficient of the mode to longitudinal force after successful matching, unit Hz/kN, and is determined by formula (2); in formula (2), K_iAnd the sensitivity coefficient of the ith-order mode after the matching is successful to the longitudinal force is expressed in Hz/kN.

Step six, calculating temperature rise according to the longitudinal force of the steel rail, and calculating the temperature of the locked rail by combining the current temperature of the steel rail;

the formula for calculating the locked rail temperature is as follows:

T_{lock with a locking mechanism}The locking rail temperature of the steel rail is measured in units; t is_{Temperature of rail}The current steel rail temperature is expressed in unit;e is the elastic modulus of the steel rail, unit MPa; alpha is the thermal expansion coefficient of the steel rail, and the unit is 1/DEG C; a is the cross-sectional area of the rail in m²。

The invention has the beneficial effects that: the method for measuring the locked rail temperature based on the overall change of the rail modes comprises the steps of establishing a mapping relation between longitudinal force and rail modes through a mode experiment to form a relation digital dictionary, and selecting any region on a service steel rail to perform the mode experiment to obtain multi-stage vibration modes of the steel rail; and matching the actually measured vibration mode of the steel rail with the steel rail mode under the zero longitudinal force in the digital dictionary, further calculating the longitudinal force of the steel rail, and finally measuring the locking rail temperature of the steel rail. The method for measuring the locked rail temperature can eliminate the influence of rail parameters by utilizing the integral change of the rail mode, and the influence of longitudinal force is only reflected by the mean value of multi-stage modes by the linear relation between the longitudinal force of the rail and the natural vibration frequency; and, greatly reduce the work load of utilizing rail vibration characteristic to measure longitudinal force. The method is simple to operate, free of influence of track parameters, high in efficiency and feasible, free of damage to structural stability of the existing track, capable of accurately measuring longitudinal force of the steel rail in the local section based on overall change of the steel rail mode, suitable for detection of locking rail temperature of ballasted and ballastless track steel rails, and wide in application range.

Drawings

FIG. 1 is a schematic flow diagram of the process of the present invention.

FIG. 2 is a diagram of a test protocol for the method of the present invention.

FIG. 3 is a graph of the variation of a characteristic modal component of a certain order of an experimental platform with temperature.

FIG. 4(a) is a characteristic modal change value at a certain measurement; fig. 4(b) is a mean and a variance of the corresponding characteristic frequencies.

FIG. 5 is a lock-out rail temperature map as a function of temperature.

FIG. 6(a) is the modal change value at a certain measurement; fig. 6(b) is the mean and variance of the corresponding frequencies.

FIG. 7 is a predicted lock-out rail temperature map.

Detailed Description

The specific steps of the present invention are explained in detail. The method for measuring the locked rail temperature based on the overall change of the steel rail mode comprises the following steps:

firstly, carrying out modal experiments on the steel rail under different longitudinal forces. During modal experiments, arranging a vibration sensor on a steel rail, exciting by a vibration exciter or a force hammer to obtain a vibration signal, and obtaining the self-vibration frequency above 500Hz by utilizing frequency domain analysis; the mode experiment needs to measure the rail modes of the rail above 500Hz and as many as possible, including frequency, damping and vibration mode.

And step two, establishing a mapping relation between the longitudinal force and the steel rail mode to form a relation digital dictionary. And according to the linear relation between the longitudinal force and the change value of the natural frequency, obtaining the sensitivity coefficient of each order of frequency to the longitudinal force by linear fitting, thereby establishing a mapping relation between the longitudinal force and the steel rail mode and forming a relation digital dictionary. And the digital dictionary comprises modal frequency, damping and vibration mode, sensitivity coefficient of each order of frequency to longitudinal force change, sensor layout scheme, steel rail model, track radius and other information.

And step three, selecting any region of the service steel rail to perform modal experiments. The model, the track radius and the sensor layout scheme of the service steel rail are the same as those in the digital dictionary.

And step four, matching the actually measured steel rail mode with the mode in the digital dictionary. The measured steel rail mode is compared with the mode in the digital dictionary, so that the same mode matching is realized; the modalities that match successfully are considered to be of the same order. The differences are caused only by rail parameters, longitudinal forces, etc. The number of successfully matched modes is not less than 12, and the calculation result is accurate.

And step five, calculating the longitudinal force of the steel rail. After the mode matching is successful, the change value of each order of mode frequency is solved, the average sensitivity coefficient of the mode to the locking rail temperature force is calculated, and the longitudinal force of the steel rail is calculated by using a longitudinal force formula.

The longitudinal force formula is:

F_{longitudinal direction}Represents the longitudinal force, and the specified pull is positive and has a unit kN; f. of_iThe measured ith order modal frequency is expressed in Hz after the matching is successful; f. of_{Logo i}Representing the corresponding order modal frequency in the digital dictionary after successful matching, wherein the frequency is the frequency of the steel rail with zero tension and is in Hz; n represents the number of successfully matched modes, the value is not less than 12, and the larger the number value is, the more accurate the result is;representing the average sensitivity coefficient of the mode to longitudinal force after successful matching, unit Hz/kN, determined by equation (2); in formula (2), K_iAnd the sensitivity coefficient of the ith-order mode after the matching is successful to the longitudinal force is expressed in Hz/kN.

And step six, acquiring the locking rail temperature of the steel rail. And calculating the temperature rise according to the longitudinal force of the steel rail, and calculating the temperature of the locking rail by combining the current temperature of the steel rail.

The formula for calculating the locked rail temperature is as follows:

T_{lock with a locking mechanism}The locking rail temperature of the steel rail is measured in units; t is_{Temperature of rail}The current steel rail temperature is expressed in unit; e is the elastic modulus of the steel rail, unit MPa; alpha is the thermal expansion coefficient of the steel rail, and the unit is 1/DEG C; a is the cross-sectional area of the rail in m²。

Example (b):

3 vibration sensors, 1 railway special temperature sensor, 1 force hammer and 1 set of signal test and analysis system are used. Firstly, vibration sensors are arranged at equal intervals at the position of a neutral layer of the same cross-rail web of the steel rail, and transverse vibration is measured. The excitation points are distributed at equal intervals on adjacent spans, and the number of the excitation points is 5; hammering point by point and multiple times. The temperature sensor is arranged on the steel rail and used for measuring the temperature of the steel rail in real time. The test protocol is shown in figure 2.

Then, rail tensile tests were carried out using the following details: the model is 60 rails, the length is 35 meters, one end is fixed, the other end is free, and the free end can be stretched; the fastener torque was 120N · m. And applying different pulling forces by using a stretching machine to simulate the change of the rail temperature, attaching a strain gauge to the rail web of the steel rail, and reading the internal stress. The simulated rail temperature changes for different tensile stresses are shown in table 1.

TABLE 1 simulation of rail temp. variation table for different tensile stresses

And establishing a mapping relation between the longitudinal force and the steel rail mode to form a relation digital dictionary.

Then, the experiment is carried out on a steel rail experiment platform, and the details of the used steel rail are as follows: the model is 60 rails, the length is 35 meters, and two ends are fixed; the rail temperature was locked at 0 ℃. During testing, the temperature change range of the steel rail is 2-19 ℃ from 8 am to 12 am, and 7 groups are provided. Fig. 3 shows the change rule of the characteristic modal component of a certain order with temperature, the characteristic modal component and the temperature are in a linear relationship, and the linear correlation coefficient is 0.95. Fig. 4(a) shows the characteristic modal variation value at a certain measurement, and 15 pairs of characteristic modal components are successfully matched. Fig. 4(b) is the mean and variance of the corresponding characteristic frequencies, and from the 10 th pair, the mean has no longer changed significantly.

Calculating the locked rail temperature, wherein the measured value of the locked rail temperature is changed within the range of-4.6-3.2 ℃, the mean value is 0.3 ℃, and the variance is 3 ℃ (as shown in figure 5); the true lock rail temperature is 0 ℃. Within the single measurement error of +/-5 ℃, the average value obtained by multiple measurements is closer to the real locked rail temperature.

And then, carrying out a locking rail temperature measurement experiment on the service steel rail. The service steel rail conditions are as follows: the model 60 rail comprises a ballast track bed and a straight track; the rail temperature was locked at 10 ℃. The left rail and the right rail are respectively made into two groups, each group comprises two measuring points corresponding to the left rail and the right rail, and the distance between the front measuring point and the rear measuring point of the two groups is 15 meters. Fig. 6(a) shows the modal change value at a certain measurement, and there are 13 pairs of mode matching successes. Fig. 6(b) is the mean and variance of the corresponding frequencies, from pair 10, the mean has no longer changed significantly. FIG. 7 is a predicted lock-out rail temperature; locking the rail temperature measurement value, wherein the left rail is at 7.76-8.04 ℃ and the right rail is at 6.9-13.04 ℃; the rail temperature is actually locked at 10 ℃, and the measurement error is +/-3 ℃.