Method for testing surface roughness of full section of steel rail

Abstract

The invention discloses a method for testing the surface roughness of the full section of a steel rail. The method comprises the following steps: taking a steel rail sample; cleaning the surface; assembling the sample; parameters are designed to carry out steel rail roughness testing, an X range is designed, coordinate point data measured by a sensor are transmitted to a computer through an electric appliance assembly, mathematical operation processing is carried out on the collected original coordinate data, and the required roughness of the train steel rail is marked; according to the detection method, a surface roughness meter is used in a mechanical measurement method, a test tool bit with a certain length is marked on the surface of the steel rail, and small fluctuation of surface height is recorded; and the Rasd value is obtained through calculation, so that the roughness of the surface of the steel rail is judged. The invention aims to obtain the tolerance degree of the steel rail under the condition of resisting alternating load and corrosion by measuring the roughness of the steel rail, and provides a corresponding assessment value, so that a manufacturer is guided to produce the steel rail with a smooth surface, and the steel rail can be used as a factory inspection requirement of a steel rail product in the future, so that the service life of the steel rail product is prolonged, and the safety of railway operation is improved.

Description

Technical Field

[0001] The invention belongs to a method for testing the surface roughness of the entire cross-section of a rail. Background Art

[0002] Rail roughness refers to the measurement of the unevenness of the rail surface, usually expressed by the Ra value. The Ra value is an important parameter of surface roughness, indicating the average value of the surface morphology deviation per unit length. The larger the Ra value, the rougher the rail surface.

[0003] In summary, roughness has a significant impact on mechanical properties and corrosion: high-roughness surfaces are more susceptible to corrosion than low-roughness surfaces. This is because high-roughness surfaces have more "defects" and "catalytic centers", which promote the occurrence of corrosion. Corrosion characteristics of low-roughness surfaces: Corrosion on low-roughness surfaces mainly occurs at notches, oxides and other rust spots on the surface. Because the surface is relatively flat and has fewer defects, it is more difficult to corrode. Roughness and corrosion rate: The rougher the material, the more likely it is to corrode, because there will be more defects and catalytic centers on the high-roughness surface, forming more oxides, etc., which accelerates the formation of corrosion. Impact on coating properties: Roughness also affects the bonding force between the coating and the substrate, thereby affecting the corrosion resistance of the coating. In order to improve the mechanical properties and corrosion resistance of parts, it is key to control the surface roughness to an appropriate range. During the design and manufacturing process, the appropriate roughness standard should be selected according to specific needs, and the target roughness should be achieved through grinding, polishing and other means.

[0004] The non-working side section of the rail refers to the side of the rail head, the rail waist, the rail bottom and other areas. The evaluation of the roughness of the non-working side can evaluate the resistance to deterioration and corrosion resistance of the mechanical properties of the rail during service. The effect of roughness on the strength of the rail is: the rougher the surface of the part, the more sensitive it is to stress concentration, especially under the action of alternating loads, the greater the impact; the effect of roughness on the corrosion resistance of the rail is: the rougher the material, the more prone to corrosion, because there will be more defects and catalytic centers on the high-roughness surface, forming more oxides, etc., which accelerates the formation of corrosion. In order to improve the mechanical properties and corrosion resistance of parts, it is key to control the surface roughness to an appropriate range. During the design and manufacturing process, the appropriate roughness standard should be selected according to specific needs, and the target roughness should be achieved through grinding, polishing and other means.

[0005] According to the international standard ISO 4287-1998, the surface roughness of the rail should not exceed 0.4μm (arithmetic mean deviation of the profile). The roughness should not exceed 0.2μm (arithmetic mean deviation of the profile) to ensure the smoothness of the contact between the wheel and the rail. Summary of the invention

[0006] The purpose of the present invention is to provide a method for testing the surface roughness of the entire cross-section of a rail, which measures the roughness of the rail to obtain the tolerance of the rail against alternating loads and corrosion conditions, and proposes corresponding assessment values, thereby guiding manufacturers to produce rails with smooth surfaces. In the future, this can be used as an inspection requirement for rail products before leaving the factory to improve their service life and the safety of railway operation.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] The present invention provides a method for testing the surface roughness of a full-section rail, comprising the following steps:

[0009] (1) Rail sampling: Select rails produced within 3 days and keep the surface of the rails free of oxide layer;

[0010] (2) Surface cleaning: Use a brush to clean the sample;

[0011] (3) Assembling the sample: Place the sample on the main table of the test host through a fixing device;

[0012] (4) Design parameters for rail roughness test, design the X range to transmit the coordinate point data measured by the sensor to the computer through the electrical components, perform mathematical operations on the collected raw coordinate data, and mark the required roughness of the train rail;

[0013] (5) Testing method: The mechanical measurement method uses a surface roughness meter to draw a certain length of test blade on the rail surface and record small fluctuations in surface height. The Rasd value is obtained by calculation to determine the roughness of the rail surface.

[0014] Furthermore, in the step (1), a 60 mm sample is cut along the height direction of the rail.

[0015] Furthermore, a roughness test was conducted with one set of data measured every 20 mm.

[0016] Further, rough

[0017] The roughness test parameter settings are shown in the following table:

[0018]

[0019] Furthermore, in actual operation, the roughness of all rail grinding surfaces must be maintained below 12 μm.

[0020] Furthermore, the Wasd value is used to characterize the roughness. The standard deviation of the Wasd roughness is used to describe the discrete degree of the roughness value. The specific method is as follows:

[0021] Calculate the average value of the roughness data set, denoted as Wa;

[0022] Calculate the difference between each data point and the mean, denoted as W(x);

[0023] Calculate the difference between it and the average value H (i.e. W(x)-Wa);

[0024] Calculate the square of the difference: square each difference obtained above, add all the squared differences to get a sum, and divide it by the number of data points n to get the average square error;

[0025] Calculate the standard deviation: Take the square root of the average variance to get the standard deviation of roughness Wsd. Expressed in mathematical formula, the calculation formula for the standard deviation of roughness Wsd is:

[0026] Wsd=sqrt((1 / n)*Σ((W(x)-Wa) 2 ))

[0027] Where sqrt represents square root, Σ represents summation, n is the number of data points, W(x) is each roughness data point in the data set, and Wa is the average value of the data set.

[0028] Compared with the prior art, the beneficial technical effects of the present invention are:

[0029] The present invention proposes a new idea, that is, by measuring the roughness of the rails, the tolerance of the rails against alternating loads and corrosion conditions is obtained, and corresponding assessment values ​​are proposed, so as to guide manufacturers to produce rails with smooth surfaces. In the future, this can be used as an inspection requirement for rail products before leaving the factory to improve their service life and the safety of railway operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will be further described below in conjunction with the accompanying drawings.

[0031] Figure 1 Sampling dimension diagram for rails;

[0032] Figure 2 is a schematic diagram of a sample fixing device 1;

[0033] Figure 3 is a schematic diagram of a sample fixing device 2;

[0034] Figure 4 is a schematic diagram of the gasket;

[0035] Figure 5 Assemble schematic diagrams for fixtures;

[0036] Figure 6 Schematic diagram of the roughness test. DETAILED DESCRIPTION

[0037] A method for testing the surface roughness of a full section of a rail, comprising the following steps:

[0038] (1) Rail sampling: Select rails produced within 3 days. At this time, the rails can maintain their surface condition. Rails produced more than 3 days ago may undergo electrochemical reactions and form an oxide layer on the surface, which will affect the authenticity of the test. Cut a 60mm sample along the height direction of the rail. Figure 1 .

[0039] (2) Surface cleaning: Use a brush to clean the sample.

[0040] (3) Design of the fixing device:

[0041] The function of the fixing device is to fix the rail sample while ensuring: Two devices are designed to fix the two sides of the sample respectively:

[0042] The specific dimensions of the fixture 1 are shown in Figure 2 Drill two holes of 30×10mm in length on the bottom surface of the device, and drill Ø8mm bolt holes on the corrugation profiler table to fix the device.

[0043] The function of the fixture 2 is to fix the rail head to ensure the accuracy of the test data. The dimensions are shown in Figure 3 .

[0044] According to different rail types, different thicknesses of rail head clamping mechanisms are designed to keep the rails level. For specific dimensions, see Figure 4 and Table 2.

[0045] The thickness L of the gasket is as follows according to different rail types:

[0046] Table 1 Thickness of gaskets of different rail types

[0047] Rail type (kg / m) L(mm) 43 - 50 9 60 18 75 17

[0048] (4) Installation of the fixture: Install the fixture on the main machine table. See the installation diagram for details. Figure 5 .

[0049] (5) Design parameters for rail roughness test, design the X range, transmit the coordinate point data measured by the sensor to the computer through the electrical components, perform mathematical operations on the collected original coordinate data, and mark the required train rail roughness.

[0050] (6) Testing method Mechanical measurement method uses a surface roughness meter to draw a certain length of test blade on the rail surface and record the small fluctuations in surface height. The Rasd value is obtained by calculation to determine the roughness of the rail surface.

[0051] Specifically, during the test:

[0052] 1. First, fix the sample on the table of the roughness profiler, such as Figure 6 As shown;

[0053] 2. Set the equipment parameters and conduct roughness test, measuring a set of data every 20 mm. See Table 2 for specific parameters.

[0054] Table 2 Roughness test parameters

[0055]

[0056]

[0057] 3. Testing

[0058] The system mainly includes: host table, computer, fixture, sample, probe and rod, motion device. First, hold the sample, start the machine, put the probe in the initial position, run the X-axis from left to right, and perform roughness test on the Y-axis. At the same time, the computer displays the current operation prompts, the coordinates of the cursor in the graphic display area and other information.

[0059] 4. Data processing

[0060] The roughness of the rail is a key indicator for evaluating the surface quality of the rail, usually expressed by the Ra value. The Ra value is an important parameter of surface roughness, which indicates the average value of the surface morphology deviation per unit length. The larger the Ra value, the rougher the rail surface. According to the international standard ISO 4287-1998, the surface roughness of the rail should not be greater than 0.4μm (arithmetic mean deviation of the profile). In actual operation, the roughness of all rail grinding surfaces must be kept below 12μm.

[0061] The Wasd value is used to characterize the roughness. The standard deviation of the Wasd roughness is used to describe the discrete degree of the roughness value. The specific method is as follows:

[0062] Calculate the average value of the roughness data set, denoted as Wa;

[0063] Calculate the difference between each data point and the mean, denoted as W(x);

[0064] Calculate the difference between it and the average value H (i.e. W(x)-Wa);

[0065] Calculate the square of the difference: square each difference obtained above, add all the squared differences to get a sum, and divide it by the number of data points n to get the average square error;

[0066] Calculate the standard deviation: Take the square root of the average variance to get the standard deviation of roughness Wsd. Expressed in mathematical formula, the calculation formula for the standard deviation of roughness Wsd is:

[0067] Wsd=sqrt((1 / n)*Σ((W(x)-Wa) 2 ))

[0068] Where sqrt represents square root, Σ represents summation, n is the number of data points, W(x) is each roughness data point in the data set, and Wa is the average value of the data set.

[0069] Case 1

[0070] CL60 rails were selected for roughness testing. A total of 5 sets of data were obtained and the arithmetic mean of the roughness was taken. According to international standards and a large amount of experimental data, it was concluded that the surface roughness of the rails should not be greater than 0.2μm (arithmetic mean deviation of the profile). After the parts measurement, marking and parameter evaluation are completed, the test results can be printed out.

[0071]

[0072] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for testing the surface roughness of a full section of a rail, characterized by: The steps include: (1) Rail sampling: Select rails produced within 3 days and keep the surface of the rails free of oxide layer; (2) Surface cleaning: Use a brush to clean the sample; (3) Assembling the sample: Place the sample on the main table of the test host through a fixing device; (4) Design parameters for rail roughness test, design the X range to transmit the coordinate point data measured by the sensor to the computer through the electrical components, perform mathematical operations on the collected raw coordinate data, and mark the required roughness of the train rail; (5) Testing method: The mechanical measurement method uses a surface roughness meter to draw a certain length of test blade on the rail surface and record small fluctuations in surface height. The Rasd value is obtained by calculation to determine the roughness of the rail surface.

2. The rail full-section surface roughness testing method according to claim 1, characterized in that: In the step (1), a 60 mm sample is cut along the height direction of the rail.

3. The rail full-section surface roughness testing method according to claim 1, characterized in that: The roughness test is carried out with one set of data measured every 20 mm.

4. The rail full-section surface roughness testing method according to claim 1, characterized in that: The roughness test parameter settings are shown in the following table:

5. The rail full-section surface roughness testing method according to claim 1, characterized in that: In actual operation, the roughness of all rail grinding surfaces must be kept below 12μm.

6. The rail full-section surface roughness testing method according to claim 1, characterized in that: The Wasd value is used to characterize the roughness. The standard deviation of the Wasd roughness is used to describe the discrete degree of the roughness value. The specific method is as follows: Calculate the average value of the roughness data set, denoted as Wa; Calculate the difference between each data point and the mean, denoted as W(x); Calculate the difference between it and the average value H, that is, W(x)-Wa; Calculate the square of the difference: square each difference obtained above, add all the squared differences to get a sum, and divide it by the number of data points n to get the average square error; Calculate the standard deviation: Take the square root of the average variance to get the standard deviation of roughness Wsd. Expressed in mathematical formula, the calculation formula for the standard deviation of roughness Wsd is: Wsd=sqrt((1 / n)*Σ((W(x)-Wa) 2 )) Where sqrt represents square root, Σ represents summation, n is the number of data points, W(x) is each roughness data point in the data set, and Wa is the average value of the data set.

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