KR102248496B1 - Stress measurment system for railway rail and measurement method using the same - Google Patents

Abstract

A stress measurement system for a railway rail according to an embodiment of the present invention comprises: a bogie capable of running along the rails of the railway; and a stress measuring device mounted on the lower portion of the bogie and measuring the stress of the rail using a fluorescence spectrum generated by irradiating a laser beam to a thermite welding part of the rail.

Description

Railway rail stress measurement system and measurement method using the same {STRESS MEASURMENT SYSTEM FOR RAILWAY RAIL AND MEASUREMENT METHOD USING THE SAME}

The present invention relates to a stress measurement system and a measurement method using the same, and more particularly, to a system for measuring the stress of a railroad rail and a method of measuring the stress of a railroad rail using the same.

Continuous Welded Rail (CWR) is a rail that is continuous for at least 200m and is usually continuous for several kilometers, and vibration is reduced when driving a train compared to the standard length rail, which is interrupted to a length of 20-25m. There is an advantage of excellent maintenance because it is excellent and there is no joint plate. In particular, for high-speed trains of 250 km/h or more, long rails should be applied indispensably to secure driving safety. In the long rail, an immovable zone is formed in which only the stress of the rail changes without displacement of the rail according to the temperature change. In the floating section, free expansion and contraction of the rail is restricted when the temperature changes, so stress may occur in the longitudinal direction of the rail, so when the temperature increases in summer, buckling (elongation) due to compressive stress and fracture due to tensile stress due to temperature drop in winter Must be reviewed.

The stress caused by the temperature change occurring in the long rail does not induce displacement, so it cannot be measured with a general strain meter. Since the strain meter measures only the relative strain that occurs based on the time it is installed, it is not an appropriate measurement method to manage the stress of the long rail. In order to overcome these limitations and to effectively maintain the long rail, a stress measurement method that is not based on strain is required.

An object of the present invention is to provide a railroad rail stress measurement system capable of measuring rail stress at high speed and in a non-contact manner.

An object of the present invention is to provide a method for measuring the stress of a railroad rail in which the stress of the rail is measured at high speed and in a non-contact manner.

The system for measuring the stress of a railroad rail according to an embodiment of the present invention includes a bogie capable of running along a rail of the railroad, and a fluorescent spectrum generated by irradiating a laser beam to a thermite welding portion of the rail and mounted under the bogie. It includes a stress measuring device for measuring the stress of the rail by using.

The stress measurement device includes a laser source generating and emitting a laser beam, a probe for irradiating a laser beam emitted from the laser source to a thermite welding portion of the rail and collecting fluorescence generated from aluminum oxide of the rail, and the probe A spectrometer that measures the spectrum of fluorescence collected by, a signal processing device that measures a peak shift by analyzing the measured spectrum and calculates the stress of the rail, and a non-contact type that measures the temperature of the rail and provides it to the signal processing device. Includes a temperature sensor.

The method for measuring the stress of a rail using the system for measuring the stress of a railroad rail of the present invention comprises the steps of: moving the bogie to a point of the rail to measure the stress, and the stress measuring device applies a laser beam to the thermite weld of the rail Irradiation and collecting a spectrum of fluorescence generated from the aluminum oxide of the rail, the stress measuring device measuring the temperature of the rail, the stress measuring device based on the collected spectrum of fluorescence and the measured temperature And measuring the absolute stress of the rail.

The measuring of the absolute stress of the rail includes the steps of extracting a total peak shift value by measuring and analyzing the fluorescence spectrum collected by the stress measuring device, and extracting the total peak shift value by using the measured temperature by the stress measuring device. And removing the peak shift value according to the temperature change from the peak shift value.

According to the present invention, it is possible to measure the stress of the rail at high speed and in a non-contact manner.

According to the present invention, by measuring the temperature of the rail in real time using a non-contact temperature sensor and reflecting it at the time of stress measurement, it is possible to measure the absolute stress of the rail without the influence of temperature.

According to the present invention, by directly measuring the stress of aluminum oxide, there is no need for a separate calibration due to steel grade, corrosion, cross-sectional loss, etc. of the rail, and stress can be measured by a simple method through laser irradiation and spectrum analysis. .

According to the present invention, it is possible to monitor the stress state of the rail at all times by measuring the stress at points of interest including the thermite welds of the rail while traveling along the train track.

1 is a diagram illustrating aluminum oxide particles distributed in a thermite weld of a rail.
2 is a graph showing intrinsic peaks of a fluorescence spectrum for aluminum oxide.
3 is a diagram schematically showing a non-contact stress measurement system according to an embodiment of the present invention.
4 is a diagram schematically showing a non-contact stress measurement apparatus according to an embodiment of the present invention.
5 is a diagram illustrating a signal processing algorithm of a spectrometer included in a stress measurement device.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to indicate the same or similar elements.

Fluorescence Spectrometry is briefly described. When a specific molecule is irradiated with a laser, light is absorbed and the molecular structure becomes excited. When light-absorbing molecules become excited, they become unstable and return to their original state while releasing energy. At this time, the emitted light has a unique wave number according to the characteristics of each molecule, and the presence or absence of a specific molecule can be determined by analyzing this frequency through a spectroscope. When the molecule is stressed, its inherent wavenumber moves finely. This property can be used to determine the stress of the molecule.

Fluorescence spectroscopy is not applicable to general steel and steel structures because there is no reaction in the Fe series. However, the reaction is very good with aluminum oxide (Al ₂ O _{3 ).} Since the rail is made of high carbon steel, fluorescence spectroscopy cannot be applied, but since the thermite weld of the rail uses an exothermic reaction of iron oxide and aluminum during welding, aluminum oxide particles remain as impurities in the thermite weld. The aluminum oxide particles are particularly concentrated at the interface between the weld and the base metal (see Fig. 1).

In the case of aluminum oxide, when the laser is irradiated, fluorescence is generated along with the scattered light. The intensity of the fluorescence spectrum measured from the fluorescence is relatively high compared to the intensity of the Raman spectrum and has excellent sensitivity to stress. Can be analyzed.

Referring to FIG. 2, it has been reported that the fluorescence spectrum of aluminum oxide has two peak values (R1 and R2), and their wavenumbers are 14402 cm ^-1 and 14432 cm ^{-1, respectively.} When compressive stress is applied to aluminum oxide, it moves to the left and to the lower wavenumber, and when tensile stress is applied, it moves to the right and toward the higher wavenumber.

The present invention provides a stress measurement system capable of measuring the stress of a rail at high speed in a non-destructive and non-contact manner using fluorescence spectroscopy.

3 is a diagram schematically showing a non-contact stress measurement system according to an embodiment of the present invention. 4 is a diagram schematically showing a non-contact stress measurement apparatus according to an embodiment of the present invention.

3 and 4, the stress measurement system 10 of the railway rail includes a train bogie 13 capable of running along the rail 11 of the railway, and a stress measuring device 100 installed under the train bogie 13. ) Can be included.

The stress measurement device 100 may include a laser source 110, a spectrometer 120, a probe 130, a signal processing device 140, and a non-contact temperature sensor 160. The laser source 110 and the probe 130, and the spectrometer 120 and the probe 130 may be connected to each other through an optical cable capable of transmitting light.

The stress measurement device 100 may be installed between the wheels and the wheels of the train bogie 13 capable of running along the rail, and by irradiating a laser to the thermite welding portion of the rail and analyzing the fluorescence spectrum reflected from the aluminum oxide, the rail The stress state of (11) can be measured. The stress measurement device 100 measures the temperature of the rail 11 and reflects it in the analysis of the fluorescence spectrum of aluminum oxide, thereby measuring the absolute stress of the rail 11 from which the temperature influence is excluded.

The laser source 110 may generate and emit a laser beam having a wavelength of 532 nm, for example.

The probe 130 may irradiate the laser beam emitted from the laser source 110 to the thermite welding portion 15 of the rail, and collect fluorescence generated in the thermite welding portion 15 of the rail. The probe 130 may irradiate a laser onto a web of a rail, for example. This is because the head of the rail has almost no aluminum oxide because the grinding process is performed to smooth the surface.

The spectrometer 120 may measure the fluorescence spectrum collected through the probe 130 and output it to the signal processing device 140 to be described later.

The spectrometer 120 includes an entrance slit for adjusting the bandwidth of light collected through the probe 130, a collimating lens for collimating the light passing through the slit, and the A diffraction grating that diffracts the light passing through the collimating lens, a mirror that reflects the light diffracted from the diffraction grating, and a detector that converts and outputs the light reflected from the mirror into a digital signal ( detector).

By disposing the mirror between the diffraction grating and the detector to increase the optical path, the resolution of the spectrometer 120 may be improved.

In addition, since a filter is additionally disposed between the diffraction grating and the mirror to block light outside the desired wavelength range, noise can be reduced and the imaging depth in the pixel of the detector can be increased. 120) can be improved. In addition, in order to further increase the optical path, two or more mirrors may be disposed between the diffraction grating and the detector. The resolution of the spectrometer 120 ^{may be improved to 4 cm -1} or less, for example, 1 cm ^-1 .

The signal processing apparatus 140 may receive a digital signal output from the detector of the spectrometer 120, analyze a spectrum of fluorescence of aluminum oxide, measure a peak shift, and calculate the stress of the rail.

The signal processing apparatus 140 processes the digital signal according to the following algorithm in order to accurately determine the wave numbers of the R1 and R2 peaks of aluminum oxide from the fluorescence spectrum.

Referring to FIG. 5, the signal processing apparatus 140 collects raw data of a fluorescence spectrum of aluminum oxide. The raw data is expressed as the intensity of the total wave number. Since the area for acquiring the peak of aluminum oxide among the raw data corresponds to a very small area, it is necessary to set a boundary, that is, an upper bound and a lower bound, in order to acquire valid data. For example, the upper limit may ^{be set to 14550 cm -1} , and the lower limit may be set to ^{14300 cm -1.}

Only valid data is extracted (trimming) according to the upper and lower limits set in this way. Then, the baseline of the spectral data must be removed. Since both ends of the basis function to be used for deconvolution of the R1 and R2 peaks from the spectrum are based on 0, it is necessary to perform a task of removing the baseline so that both ends of the spectrum intensity are also set to 0.

Thereafter, in order to separate the R1 and R2 peaks from the spectrum, a boundary to which each basis function is applied must be set. It is advantageous that the boundary is symmetric about the peak, and different values are applied for the R1 and R2 peaks. When each boundary is set in this way, a process of directly separating the R1 peak and the R2 peak is performed. At this time, various basis functions can be used, but it is advantageous to use the Gaussian function or the Lorentzian function mainly to find the peaks of the aluminum oxide spectrum. R1 and R2 curves are obtained by finding coefficients that can minimize the error between the assumed basis function and the actual spectrum.

After actually separating the R1 and R2 peaks, values such as peak position, FWHM, area, and error can be found and output by applying interpolation to the separated signals respectively.

From the wave number of the peak extracted through analysis of the collected fluorescence spectrum (eg, the wave number of the R1 peak), the total peak shift value can be derived through (Equation 1) below.

(식 1)

(Equation 1)

: 측정된 전체 파수 쉬프트 값 [cm^-1]

: Measured total wavenumber shift value [cm ^-1 ]

: 측정된 스펙트럼의 피크 파수 값

: Peak wave number value of the measured spectrum

: 응력이 없는 상태에서의 피크 파수 값

: Peak wavenumber value in the absence of stress

)을 얻는다. 이때 온도 효과를 상쇄하기 위하여 기준 온도 298.8K에서 측정한다. Since the thermite welding part of the rail has accumulated stress inside during welding, in order to solve this, the peak wavenumber value of the spectrum in the state where there is no stress from the thermite powder or aluminum oxide powder obtained by pulverizing the thermite welding part of the rail (

). At this time, it is measured at a reference temperature of 298.8K to offset the temperature effect.

The fluorescence spectrum is affected by the stress of the object, but is also sensitively affected by temperature. Therefore, when measuring the stress of an object using fluorescence spectroscopy, it is necessary to measure the temperature of the object together to eliminate the effect of temperature.

The non-contact temperature sensor 150 may measure the temperature of the rail 11 and transmit it to the signal processing device 140. The signal processing apparatus 140 may exclude a peak shift value according to a temperature change from the total peak shift value by using the measured temperature of the rail.

The signal processing apparatus 140 may derive only the peak shift due to the stress through (Equation 2) below. The signal processing apparatus 140 may remove the peak shift value according to the temperature change from the total peak shift value according to (Equation 2).

(식 2)

(Equation 2)

: 응력에 의한 피크 쉬프트 값 [cm^-1]

: Peak shift value due to stress [cm ^-1 ]

: 온도 변화에 의한 피크 쉬프트 계수 [cm^-1/K]

: Peak shift coefficient due to temperature change [cm ^-1 /K]

T: The temperature of the rail during measurement [K]

T _ref : Reference temperature [298.8K]

(온도 변화에 의한 피크 쉬프트 계수)는 온도와 피크 쉬프트 사이의 선형 관계를 나타내는 계수로서, 미리 온도 변화 실험으로부터 얻어질 수 있다.

(Peak shift coefficient due to temperature change) is a coefficient representing a linear relationship between temperature and peak shift, and can be obtained from a temperature change experiment in advance.

(온도 변화에 의한 피크 쉬프트 계수)는 결정될 수 있다.From thermite powder or aluminum oxide powder obtained by pulverizing the weld of the rail, the fluorescence spectrum is analyzed using a spectrometer while changing the temperature to measure the peak shift value. Using linear regression on the measured data

(Peak shift coefficient due to temperature change) can be determined.

Since the peak shift value of the fluorescence spectrum has a linear relationship with the stress generated in the rail, the absolute stress of the rail can be derived from (Equation 3) below from the peak shift value due to the stress obtained from (Equation 2).

(식 3)

(Equation 3)

: 측정된 레일의 절대 응력 [MPa]

: Measured absolute stress of rail [MPa]

: 압전 분광 계수(piezospectroscopic coefficient) [cm^-1/GPa]

: Piezospectroscopic coefficient [cm ^-1 /GPa]

(압전 분광 계수)는 응력과 피크 쉬프트 사이의 선형적 관계를 나타내는 계수로서, 미리 레일 용접부에 대한 하중 재하 실험으로부터 얻어질 수 있다. 별도로 마련된 레일 용접부에 압축 응력을 증가시키면서 응력 측정 장치를 이용하여 산화알루미늄으로부터 발생한 형광의 피크 쉬프트 값을 측정한다. 측정된 데이터에 선형 회귀(linear regression)을 사용해

(압전 분광 계수)가 결정될 수 있다. here,

(Piezoelectric spectral coefficient) is a coefficient representing a linear relationship between stress and peak shift, and can be obtained from a load loading experiment on a rail weld in advance. While increasing the compressive stress on the separately provided rail weld, the peak shift value of the fluorescence generated from aluminum oxide is measured using a stress measuring device. Using linear regression on the measured data

(Piezoelectric spectral coefficient) can be determined.

By analyzing the spectrum of fluorescence generated in the thermite weld using the stress measurement system 10 of a railroad rail according to an embodiment of the present invention, extracting a peak shift value, removing the temperature effect, and dividing by a piezoelectric spectral coefficient, the rail The absolute stress of can be measured non-destructively, non-contact, and quickly.

In the above, the measurement of the stress on the terminator weld 15 of the rail using the stress measurement system 10 of a railroad rail according to an embodiment of the present invention has been described above, but the stress of the railroad rail according to an embodiment of the present invention The measurement system 10 can also be used to measure the stress of the rail at specific points of interest other than the weld. To this end, it is necessary to weld the aluminum patches in advance to specific points of interest other than the weld. Since the aluminum patches are oxidized in air to form aluminum oxide, which is a natural oxide film, the stress of the rail can be measured at specific points of interest using the stress measurement system of the present invention using fluorescence spectroscopy.

The aluminum patches may be linearly welded to the web or bottom of the rail in the longitudinal direction of the rail. The aluminum patches may be welded to the web or bottom of the rail in a square or circular shape.

The stress measurement method according to an embodiment of the present invention is performed using the stress measurement system 10 mounted on the train bogie 13 capable of running along the rail 11.

In the method for measuring stress according to an embodiment of the present invention, the step of moving the bogie 13 to a point of the rail 11 to measure the stress, and the stress measuring device 100 applies the laser beam to the rail 11, eg For example, irradiating the thermite weld 15 of the rail 11 and collecting the spectrum of fluorescence generated from the aluminum oxide of the rail 11, the stress measuring device 100 measures the temperature of the rail 11 And measuring the absolute stress of the rail 11 based on the collected fluorescence spectrum and the measured temperature by the stress measuring device 100.

Measuring the absolute stress of the rail 11, the stress measuring device 100 measuring the collected fluorescence spectrum, analyzing the step of extracting the total peak shift value, and the stress measuring device 100 is measured And removing a peak shift value according to a temperature change from the total peak shift value using temperature.

The spectrometer 120 of the stress measurement device 100 measures the collected fluorescence spectrum, and the signal processing device 140 analyzes the fluorescence spectrum to extract the total peak shift value according to the above-described (Equation 1). I can.

The signal processing device 140 of the stress measuring device 100 receives the temperature of the rail 11 measured by the non-contact temperature sensor 150, and according to the above-described (Equation 2), The resulting peak shift value can be removed. In addition, the signal processing device 140 may calculate the absolute stress of the rail 11 according to the above-described (Equation 3).

In the above, the embodiments of the present invention have been mainly described, but various changes or modifications may be made at the level of the person skilled in the art. Accordingly, it will be understood that such changes and modifications are included within the scope of the present invention as long as they do not depart from the scope of the present invention.

Claims (4)

A bogie capable of running along the rails of the railway; And
Includes; a stress measuring device mounted on the lower part of the bogie and measuring the stress of the rail using a fluorescence spectrum generated by irradiating a laser beam to the thermite welding portion of the rail
The stress measurement device,
A laser source generating and emitting a laser beam;
Located adjacent to the web of the rail, the laser beam emitted from the laser source is irradiated to the thermite welding portion of the rail located on the web of the rail, and the fluorescence spectrum generated from the aluminum oxide of the thermite welding portion is collected. Including;
The laser source and the probe are a stress measurement system of a railroad rail connected by an optical cable. The method of claim 1,
The stress measurement device,
A spectrometer measuring a fluorescence spectrum collected by the probe;
A signal processing device that analyzes the measured spectrum, measures a peak shift, and calculates a stress of the rail; And
A non-contact type temperature sensor that measures the temperature of the rail and provides it to the signal processing device; further comprising,
The probe and the spectrometer are a stress measurement system of a railroad rail connected by an optical cable. As a method for measuring the stress of a rail using the system for measuring the stress of a railroad rail of claim 1 or 2,
Moving the bogie to a point of the rail where the stress is to be measured;
Irradiating, by the stress measuring device, a laser beam to a thermite welding portion of the rail located on the web of the rail using a probe located adjacent to the web of the rail, and collecting a fluorescence spectrum generated from aluminum oxide of the thermite welding portion;
Measuring, by the stress measuring device, a temperature of the rail using a non-contact temperature sensor;
Measuring the absolute stress of the rail on the basis of the fluorescence spectrum and the measured temperature collected by the stress measuring device using a signal processing device; A method for measuring the stress of a railroad rail comprising a. The method of claim 3,
Measuring the absolute stress of the rail,
Measuring and analyzing the collected fluorescence spectrum by the stress measuring device to extract a total peak shift value; And
The stress measurement method of a railroad rail including; removing a peak shift value according to a temperature change from the total peak shift value by using the measured temperature by the stress measuring device.

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