CN115326608A - A kind of rail physical fatigue testing device and testing method - Google Patents

Abstract

The invention provides a steel rail physical fatigue testing device and a steel rail physical fatigue testing method, wherein the device comprises: the steel rail support group is used for supporting a steel rail and comprises a first support roller and a second support roller, and the distance between the first support roller and the second support roller is adjustable; the rail head clamping mechanism comprises a vertical loading clamp, a first longitudinal clamp and a second longitudinal clamp which are matched with each other, wherein the first longitudinal clamp and the second longitudinal clamp are used for longitudinally clamping the rail head of the steel rail, and a test connecting mechanism used for connecting the steel rail and the rail head clamping mechanism; the steel rail clamping device is provided with the steel rail supporting group and the rail head clamping mechanism, and the steel rail supporting group and the rail head clamping mechanism work in a matched mode, so that stable clamping and fixing of a steel rail to be tested are achieved, the steel rail clamping device is suitable for steel rails with different specifications, performance testing of the steel rail is facilitated, the service performance of the steel rail can be evaluated more accurately, and the steel rail clamping device is very suitable for researching the service performance of the steel rail.

Description

A rail physical fatigue test device and test method

technical field

The invention relates to the technical field of testing, in particular to the technical field of rail testing, in particular to a rail physical fatigue testing device and testing method.

Background technique

As a key component that directly supports the operation of trains, rails continue to receive dynamic bending stress during service. In this process, the rail bottom is supported by sleepers, and the rail head is repeatedly crushed by wheels; the rail between two sleepers can be simplified as a three-point bending model subject to cyclic loading. In this three-point bending model, the rail bottom is subjected to cyclic tensile stress. Once damage occurs, it is easy to cause the crack initiation and expansion of the rail bottom, causing the rail to break, especially for the weak performance of the rail welded joints. Damage occurs under cyclic loading. Therefore, the physical fatigue performance test of the rail has become an important index to evaluate the safety performance of the rail.

计算，其中F为施加在钢轨上的载荷，单位为N；σ_max为最大疲劳应力，单位为MPa，闪光焊、气压焊接头最大疲劳应力为297MPa，铝热焊接头最大疲劳应力为217MPa；L为试样支距，单位为m；W为钢轨下部断面系数，单位为mm³。According to "TB/T 1632.1-2014 Rail Welding Part 1: General Technical Conditions", rail welded joints must carry out physical fatigue tests in the form of three-point bending; the test load frequency is 5Hz±0.5Hz, the load ratio is 0.2, and the test load by formula

Calculation, where F is the load applied on the rail, the unit is N; σ _max is the maximum fatigue stress, the unit is MPa, the maximum fatigue stress of flash welding and gas pressure welding joints is 297MPa, and the maximum fatigue stress of aluminothermic welding joints is 217MPa; L is the sample support distance, the unit is m; W is the section coefficient of the lower part of the rail, the unit is mm ³ .

However, the above-mentioned test method only simulates the support of the sleeper to the rail and the cyclic loading of the wheel to the rail. In fact, in addition to being constrained and loaded by these two aspects during the service process, the rail is also subjected to temperature forces along the length of the rail, which is caused by thermal expansion and contraction of the rail. For example, the locking temperature of a 60kg/m rail on a line is 20°C. When the winter temperature is -10°C, the rail temperature is equivalent to the air temperature, the rail shrinks, and the temperature stress formed reaches 74.34MPa, and the temperature force of the entire rail section reaches 576kN; When the temperature is 30°C, the rail temperature is 20°C higher than the air temperature, the rail expands, and the temperature stress formed reaches -74.34MPa, and the temperature force of the entire rail section reaches -576kN. It can be seen that the currently used rail physical fatigue test method cannot accurately evaluate the actual service performance of the rail, and the test results have limited reference value for the rail line service.

Therefore, in view of the problem, there is a need for a rail physical fatigue test device and a test method that can more accurately evaluate the service performance of the rail.

Contents of the invention

In view of this, the object of the present invention is to propose an improved rail physical fatigue testing device and testing method to more effectively evaluate the service performance of the rail.

Based on the above purpose, on the one hand, the present invention provides a rail physical fatigue testing device, wherein the rail physical fatigue testing device includes:

A rail support group for supporting the rail, the rail support group includes a first support roller and a second support roller, and the distance between the first support roller and the second support roller is adjustable;

The rail head clamping mechanism for clamping the rail head, the rail head clamping mechanism includes a vertical loading clamp, a first longitudinal clamp and a second longitudinal clamp that cooperate with each other, the first longitudinal clamp and the second longitudinal clamp are used for the rail longitudinal clamping of the rail head, and

Test connection mechanism for connecting rails and rail head clamping mechanisms.

In some embodiments of the rail physical fatigue testing device according to the present invention, the test connection mechanism further includes:

The first connecting rod is used for connecting the first longitudinal clamp and the rail head;

The second connecting rod arranged on one side of the first connecting rod, the first connecting rod and the second connecting rod cooperate to clamp and fix the rail head on one side of the rail.

In some embodiments of the rail physical fatigue testing device according to the present invention, the test connection mechanism further includes:

The third connecting rod is used for connecting the second longitudinal clamp and the rail head;

A fourth connecting rod cooperating with the third connecting rod is also used for connecting the second longitudinal clamp and the rail head.

In some embodiments of the rail physical fatigue testing device according to the present invention, multiple sets of first clamp holes are provided on the first longitudinal clamp, and the first clamp holes are used to assist the first longitudinal clamp to clamp the rail head and the rail waist , and the first rail head bolts and the first rail waist bolts are respectively connected to multiple sets of first clamp holes.

In some embodiments of the rail fatigue testing device according to the present invention, multiple sets of second clamp holes are provided on the second longitudinal clamp, and the second clamp holes are used to assist the second longitudinal clamp to clamp the rail head and the rail waist , and the multiple sets of second fixture holes are respectively connected with second rail head bolts and second rail waist bolts.

In some embodiments of the rail fatigue testing device according to the present invention, both the first fixture hole and the second fixture hole are threaded holes, and the diameter of the threaded holes is 30mm.

Another aspect of the present invention also provides a kind of rail physical fatigue testing method, and the rail physical fatigue testing method comprises:

Step S1: preparing the test rail object;

Step S2: Assembling the actual rail: place the actual rail prepared in Step 1 on the first roller and the second roller, the centerline of the rail object, the centerline of the vertical loading fixture, the centerline of the distance between the two rollers, and the three lines coincide ;

Step S3: connecting the first longitudinal fixture and the second longitudinal fixture to the rail: calculating the test temperature force;

When the simulated rail temperature decreases, the rail shrinks, and the temperature force is tension, use the first connecting rod to connect a set of first clamp holes with the first rail head bolts, and use the second connecting rod to connect the other set of first clamp holes with the first rail head bolts. The first rail waist bolt is connected, the first clamp hole is connected with the second rail head bolt by the third connecting rod, and the first clamp hole of another group is connected with the second rail waist bolt by the fourth connecting rod.

When simulating rail temperature rise, rail expansion, and temperature force as pressure, there is no need to use connecting rods to connect the rail with the first longitudinal clamp and the second longitudinal clamp, and only need to attach the first longitudinal clamp and the second longitudinal clamp to the rail ends.

When the temperature of the simulated rail is constant, the rail has no deformation, and the temperature force is 0, the first longitudinal clamp, the second longitudinal clamp, the first connecting rod, the second connecting rod, the third connecting rod, and the fourth connecting rod do not need to be used.

Step S4: Rail physical fatigue test: When the temperature of the simulated rail decreases, the rail shrinks, and the temperature force is a tensile force, the first longitudinal fixture and the second longitudinal fixture move away from the rail respectively, passing through the first connecting rod and the second connecting rod , the third connecting rod and the fourth connecting rod realize the application of tension f2 and f3 to the rail, wherein f2 and f3 are equal in size and opposite in direction, and the vertical loading fixture applies a cyclic pressure f1 to the rail head;

When the simulated rail temperature rises, the rail expands, and the temperature force is pressure, the first longitudinal fixture and the second longitudinal fixture move in the direction pointing to the rail respectively, applying pressure f2 and f3 to the rail, where f2 and f3 are equal in magnitude and opposite in direction. The vertical loading fixture exerts cyclic pressure f1 on the rail head;

When the simulated rail temperature is constant, the rail has no deformation, and the temperature force is 0, the vertical loading fixture applies a cyclic pressure f1 to the rail head.

In some embodiments of the physical rail fatigue testing method according to the present invention, in step S1, the method for preparing the physical rail for testing specifically includes:

According to actual needs, intercept the 450-1800mm long steel rail as the test object. The length of the rail should be at least 200mm longer than the distance between the first roller and the second roller; 30mm diameter bolt holes.

In some embodiments of the rail physical fatigue testing method according to the present invention, in step S3, the test temperature force calculation formula is:

Temperature force = linear expansion coefficient of rail × elastic modulus of rail × temperature change of rail × cross-sectional area of rail.

In some embodiments of the rail physical fatigue testing method according to the present invention, the method also includes step S5:

End of test and record of test results: When the actual rail breaks, stop the test and record the number of cycles that the vertical loading fixture exerts cyclic pressure on the rail head when the rail breaks. After the number of weeks, when the actual rail is still not broken, stop the test.

The present invention has at least the following beneficial technical effects: the embodiment of the present invention is provided with a rail support group and a rail head clamping mechanism, and the rail support group and the rail head clamping mechanism work together to realize stable clamping and fixing of the rail to be tested, and It is suitable for rails of different specifications, which is beneficial to the performance test of the rails, and can more accurately evaluate the service performance of the rails, and is very suitable for carrying out research on the service performance of the rails.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention, and those skilled in the art can obtain other embodiments according to these drawings without any creative effort.

In the picture:

Fig. 1 shows the schematic diagram of the physical fatigue testing device of rail according to the present invention;

Fig. 2 shows the schematic flow chart of the embodiment of the rail physical fatigue testing method according to the present invention;

Fig. 3 shows the schematic diagram of the rail physical fatigue test method of the present invention when the temperature of the simulated rail is reduced;

Fig. 4 shows the schematic diagram of the rail physical fatigue test method of the present invention when the simulated rail temperature rises;

Fig. 5 shows a schematic diagram of the actual rail fatigue testing method of the present invention when the simulated rail temperature is constant.

In the figure: 1-rail support group, 11-first support roller, 12-second support roller, 2-rail head clamping mechanism, 21-first longitudinal clamp, 211-first clamp hole, 22-second longitudinal Fixture, 221-second fixture hole, 23-vertical loading fixture, 3-test connection mechanism, 31-first connecting rod, 32-second connecting rod, 33-third connecting rod, 34-fourth connecting rod.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

It should be noted that all expressions using "first" and "second" in the embodiments of the present invention are used to distinguish two entities with the same name or different parameters. It can be seen that "first" and "second" " is only for the convenience of expression, and should not be understood as limiting the embodiment of the present invention. Furthermore, the terms "comprising" and "having", as well as any variations thereof, are intended to cover a non-exclusive inclusion, for example, of a process, method, system, product or other steps or elements inherent in a process, method, system, product, or device comprising a series of steps or elements.

Simply put, the present invention proposes a rail physical fatigue testing device, as shown in Figure 1, the rail physical fatigue testing device comprises:

A rail support group 1 for supporting rails, the rail support group 1 includes a first support roller 11 and a second support roller 12, and the distance between the first support roller 11 and the second support roller 12 is adjustable;

The rail head clamping mechanism 2 for clamping the rail head, the rail head clamping mechanism 2 includes a vertical loading clamp 23, a first longitudinal clamp 21 and a second longitudinal clamp 22 that cooperate with each other, the first longitudinal clamp 21 and the second longitudinal clamp Two longitudinal clamps 22 are used for the longitudinal clamping of the rail head, and

Test connection mechanism 3 for connecting rails and rail head clamping mechanism 2.

In this embodiment, the rail support group 1 and the rail head clamping mechanism 2 are provided. The rail support group 1 and the rail head clamping mechanism 2 cooperate to realize the stable clamping and fixing of the rail to be tested, and are suitable for different The standard rail is conducive to the performance test of the rail, and can more accurately evaluate the service performance of the rail, which is very suitable for the research on the service performance of the rail.

Specifically, the distance between the first branch roller 11 and the second branch roller 12 is adjustable, and the distance between the first branch roller 11 and the second branch roller 12 is set to 250-1600 mm, and the vertical loading fixture 23 can realize 0 -2000kN cyclic loading.

In a preferred embodiment, the first longitudinal clamp 21 and the second longitudinal clamp 22 can realize a load of 0-±1000 kN.

In a preferred embodiment, the test connection mechanism 3 further includes:

The first connecting rod 31 is used to connect the first longitudinal clamp 21 and the rail head;

The second connecting rod 32 arranged on one side of the first connecting rod 31, the first connecting rod 31 and the second connecting rod 32 cooperate to clamp and fix the rail head on one side of the rail.

At the same time, as a setting for cooperating work, the test connection mechanism 3 also includes:

The third connecting rod 33 is used to connect the second longitudinal clamp 22 and the rail head;

The fourth connecting rod 34 cooperating with the third connecting rod 33 is also used to connect the second longitudinal clamp 22 and the rail head.

In this embodiment, the first connecting rod 31, the second connecting rod 32, the third connecting rod 33 and the fourth connecting rod 34 are specifically round rods or square rods, and the first connecting rod 31, the second connecting rod 32, The third connecting rod 33 and the fourth connecting rod 34 are made of stainless steel or iron-titanium alloy, thereby ensuring the strength and hardness of the testing device and ensuring the smooth progress of the testing work.

In a preferred embodiment, multiple sets of first clamp holes 211 are provided on the first longitudinal clamp 21, and the first clamp holes 211 are used to assist the first longitudinal clamp 21 to clamp the rail head and the rail waist, and the multiple sets of first The clamp holes 211 are respectively connected with the first rail head bolts and the first rail web bolts.

Exemplarily, a plurality of sets of first clamp holes 211 are arranged longitudinally, and the first clamp holes 211 are respectively set at the rail head and the rail waist position of the rail, and the first clamp holes 211 are threaded holes, and the diameter of the threaded holes is 30mm.

In a preferred embodiment, multiple sets of second clamp holes 221 are provided on the second longitudinal clamp 22, and the second clamp holes 221 are used to assist the second vertical clamp 22 to clamp the rail head and the rail waist, and multiple sets of second clamp holes The clamp holes 221 are respectively connected with second rail head bolts and second rail waist bolts.

Exemplarily, multiple sets of second clamp holes 221 are arranged longitudinally, and the second clamp holes 221 are threaded holes, and the diameter of the threaded holes is 30 mm.

In order to test the performance of the rail, another aspect of the present invention provides a physical fatigue test method for the rail. Fig. 2 shows a schematic flow chart of the implementation of the rail physical fatigue testing method according to the present invention. In the embodiment shown in Figure 2, the method includes:

Step S1: preparing the actual test rail, and the method for preparing the actual test rail, specifically including:

According to actual needs, intercept the 450-1800mm long steel rail as the test object. The length of the rail should be at least 200mm longer than the distance between the first roller 11 and the second roller 12; Make a bolt hole with a diameter of 30mm at the position;

Step S2: Assembling the actual rail: place the actual rail prepared in step 1 on the first roller 11 and the second roller 12, the centerline of the rail object, the centerline of the vertical loading fixture 23, and the centerline of the distance between the two rollers , the three lines overlap;

Step S3: connecting the first longitudinal fixture 21 and the second longitudinal fixture 22 to the rail: calculating the test temperature force;

In step S3, the test temperature force calculation formula is:

Temperature force = linear expansion coefficient of rail × elastic modulus of rail × temperature change of rail × cross-sectional area of rail.

When the temperature of the simulated rail decreases, the rail shrinks, and the temperature force is a tensile force, use the first connecting rod 31 to connect one group of first clamp holes 211 with the first rail head bolts, and use the second connecting rod 32 to connect the first clamp holes 211 of the other group. The clamp hole 211 is connected with the first rail waist bolt, the first clamp hole 211 is connected with the second rail head bolt with the third connecting rod 33, and the fourth connecting rod 34 connects the first clamp hole 211 of another group with the second rail. Waist bolt connection.

When simulating rail temperature rise, rail expansion, and temperature force as pressure, there is no need to use connecting rods to connect the rail with the first longitudinal fixture 21 and the second longitudinal fixture 22, and only need to connect the first longitudinal fixture 21 and the second longitudinal fixture 22 Attached to both ends of the rail.

When the simulated rail temperature is constant, the rail has no deformation, and the temperature force is 0, the first longitudinal fixture 21, the second longitudinal fixture 22, the first connecting rod 31, the second connecting rod 32, the third connecting rod 33, and the fourth connecting rod Neither rod 34 needs to be used.

Step S4: Rail physical fatigue test: When the temperature of the simulated rail decreases, the rail shrinks, and the temperature force is a tensile force, the first longitudinal fixture 21 and the second longitudinal fixture 22 move in a direction away from the rail respectively, and pass through the first connecting rod 31 and the second longitudinal fixture. The second connecting rod 32, the third connecting rod 33, and the fourth connecting rod 34 realize the application of tension f2 and f3 to the rail, wherein f2 and f3 are equal in size and opposite in direction, f2+f3=temperature force vertical loading fixture 23 pairs of rail heads apply a cyclic pressure f1;

When the temperature of the simulated rail rises, the rail expands, and the temperature force is pressure, the first longitudinal fixture 21 and the second longitudinal fixture 22 move in the direction pointing to the rail respectively, and apply pressure f2 and f3 to the rail. The magnitudes of f2 and f3 are equal and the direction On the contrary, f2+f3=temperature force vertical loading fixture 23 applies cyclic pressure f1 to the rail head;

When the simulated rail temperature is constant, the rail has no deformation, and the temperature force is 0, the vertical loading fixture 23 applies a cyclic pressure f1 to the rail head.

Step S5: End of test and record of test results: when the rail is broken, stop the test and record the number of cycles that the vertical loading fixture 23 exerts cyclic pressure on the rail head when the rail breaks. After the cyclic pressure reaches the specified number of times, the test is stopped when the actual rail is still not broken.

Exemplarily, five 60kg/m and five 75kg/m rails with artificial prefabricated defects at the bottom of the rail are selected for testing according to the actual rail fatigue test method provided by the present invention; at the same time, one rail with artificial prefabricated defects at the bottom of the rail is selected 60kg/m and one 75kg/m rail, according to the method specified in "TB/T 1632.1-2014 Rail Welding Part 1: General Technical Conditions", the test was carried out on the traditional test device as a comparison.

Example and comparative example test parameters are shown in Table 1.

Table 1 embodiment and comparative example test parameter

When the test parameters such as rail type, test frequency, maximum vertical load, and load ratio are the same, the test results of the embodiment are closely related to the simulated temperature change; From low to high, even when the temperature changes to 20°C, the rail has experienced 2 million vertical loads without breaking. The test results are consistent with the actual situation that the line rail is more prone to fracture in winter. And the comparative example that adopts traditional test method can't simulate the temperature change situation, the test result is single, can find simultaneously, the test result of simulated temperature change 0 ℃ in the embodiment is close to the comparative example test result, this shows that adopts the steel rail physical fatigue that the present invention provides The test method can not only accurately simulate the difference in service performance of rails caused by temperature changes, but also completely cover traditional test methods.

Table 2 embodiment and comparative example test result

Through comparison, it is found that selecting the rail physical test method in the present invention can more accurately evaluate the service performance of the rail, and is very suitable for carrying out research on the service performance of the rail.

In this embodiment, the rail support group 1 and the rail head clamping mechanism 2 are provided. The rail support group 1 and the rail head clamping mechanism 2 cooperate to realize the stable clamping and fixing of the rail to be tested, and are suitable for different The standard rail is conducive to the performance test of the rail, and can more accurately evaluate the service performance of the rail, which is very suitable for the research on the service performance of the rail.

The above are the exemplary embodiments disclosed in the present invention, but it should be noted that various changes and modifications can be made without departing from the scope of the disclosed embodiments of the present invention defined in the claims. The functions, steps and/or actions of the method claims in accordance with the disclosed embodiments described herein need not be performed in any particular order. In addition, although the elements disclosed in the embodiments of the present invention may be described or required in an individual form, they may also be understood as a plurality unless explicitly limited to a singular number.

It should be understood that as used herein, the singular form "a" and "an" are intended to include the plural forms as well, unless the context clearly supports an exception. It should also be understood that "and/or" as used herein is meant to include any and all possible combinations of one or more of the associated listed items. The serial numbers of the embodiments disclosed in the above-mentioned embodiments of the present invention are only for description, and do not represent the advantages and disadvantages of the embodiments.

Those of ordinary skill in the art should understand that: the discussion of any of the above embodiments is exemplary only, and is not intended to imply that the scope (including claims) disclosed by the embodiments of the present invention is limited to these examples; under the idea of the embodiments of the present invention , the technical features in the above embodiments or different embodiments can also be combined, and there are many other changes in different aspects of the above embodiments of the present invention, which are not provided in details for the sake of brevity. Therefore, within the spirit and principle of the embodiments of the present invention, any omissions, modifications, equivalent replacements, improvements, etc., shall be included in the protection scope of the embodiments of the present invention.

Claims (10)

1. A kind of physical fatigue testing device of rail, used in physical fatigue test of rail, characterized by that, said physical fatigue testing device of rail includes:

the steel rail support group is used for supporting a steel rail and comprises a first support roller and a second support roller, and the distance between the first support roller and the second support roller is adjustable;

a railhead fixture for centre gripping rail railhead, railhead fixture includes vertical loading anchor clamps, the first vertical anchor clamps and the vertical anchor clamps of second of mutually supporting, the vertical centre gripping that first vertical anchor clamps and second are used for the rail railhead, and

the test connection mechanism is used for connecting the steel rail and the rail head clamping mechanism.

2. The apparatus of claim 1, wherein the test connection mechanism further comprises:

the first connecting rod is used for connecting the first longitudinal clamp and the steel rail head;

and the first connecting rod and the second connecting rod are matched to work and are used for clamping and fixing the railhead on one side of the steel rail.

3. The apparatus of claim 2, wherein the test connection mechanism further comprises:

the third connecting rod is used for connecting the second longitudinal clamp and the steel rail head;

and the fourth connecting rod is matched with the third connecting rod to work, and is also used for connecting the second longitudinal clamp and the steel rail head.

4. The apparatus according to any one of claims 1 to 3, wherein the first longitudinal clamp is provided with a plurality of sets of first clamp holes, the first clamp holes are used for assisting the first longitudinal clamp to clamp the rail head and the rail web, and the plurality of sets of first clamp holes are respectively connected with the first rail head bolt and the first rail web bolt.

5. The apparatus of claim 4, wherein the second longitudinal clamp has a plurality of second clamp holes formed therein, the second clamp holes being adapted to assist the second longitudinal clamp in clamping the rail head and the rail web, and the plurality of second clamp holes being adapted to receive respective second head bolts and second web bolts.

6. The apparatus of claim 5, wherein the first and second clamp holes are threaded holes having a diameter of 30mm.

7. A steel rail physical fatigue testing method is used for steel rail physical fatigue testing, and is characterized by comprising the following steps:

step S1: preparing a test steel rail object;

step S2: assembling steel rails in a real object: placing the steel rail object prepared in the step 1 on a first support roller and a second support roller, wherein the center line of the steel rail object, the center line of a vertical loading clamp, the center line of the distance between the two support rollers are superposed by three lines;

and step S3: the first longitudinal clamp and the second longitudinal clamp are connected with the steel rail: calculating a test temperature force;

when the temperature reduction, the shrinkage and the temperature force of the simulated steel rail are tensile forces, one group of first clamp holes are connected with a first rail head bolt by a first connecting rod, the other group of first clamp holes are connected with a first rail web bolt by a second connecting rod, the first clamp holes are connected with a second rail head bolt by a third connecting rod, and the other group of first clamp holes are connected with a second rail web bolt by a fourth connecting rod;

when the temperature rise, the expansion and the temperature force of the simulated steel rail are pressure, the steel rail is connected with the first longitudinal clamp and the second longitudinal clamp without using a connecting rod, and only the first longitudinal clamp and the second longitudinal clamp are attached to two ends of the steel rail;

when the simulated steel rail temperature is unchanged, the steel rail has no deformation, and the temperature force is 0, the first longitudinal clamp, the second longitudinal clamp, the first connecting rod, the second connecting rod, the third connecting rod and the fourth connecting rod are not needed to be used;

and step S4: physical fatigue test of steel rails: when the temperature reduction, steel rail contraction and temperature force of the simulated steel rail are tensile forces, the first longitudinal clamp and the second longitudinal clamp respectively move towards the direction far away from the steel rail, the tensile forces f2 and f3 are applied to the steel rail through the first connecting rod, the second connecting rod, the third connecting rod and the fourth connecting rod, wherein the magnitudes of f2 and f3 are equal, the directions are opposite, and the vertical loading clamp applies the circulating pressure f1 to the rail head of the steel rail;

when the simulated temperature rise, expansion and temperature force of the steel rail are pressures, the first longitudinal clamp and the second longitudinal clamp respectively move towards the direction pointing to the steel rail, the pressures f2 and f3 are applied to the steel rail, the magnitudes of the pressures f2 and f3 are equal, the directions are opposite, and the vertical loading clamp applies the circulating pressure f1 to the rail head of the steel rail;

and when the simulated steel rail temperature is unchanged, the steel rail is not deformed, and the temperature force is 0, applying the circulating pressure f1 to the steel rail head by the vertical loading clamp.

8. The method according to claim 7, wherein in step S1, the method for preparing the test rail object specifically comprises:

a long steel rail object with the length of 450-1800mm is intercepted and used as a test object, and the length of the steel rail is at least 200mm longer than the distance between the first support roller and the second support roller; bolt holes with the diameter of 30mm are manufactured in the middle of the rail head and the rail web of the steel rail.

9. The method of claim 8, wherein in step S3, the test temperature force calculation formula is:

temperature force = linear expansion coefficient of rail x elastic modulus of rail x temperature change of rail x cross-sectional area of rail.

10. The method according to any of claims 7 to 9, characterized in that the method further comprises a step S5:

end of test and recording of test results: when the steel rail object is broken, stopping the test and recording the cycle of applying the circulating pressure to the steel rail head by the vertical loading fixture when the steel rail is broken, and stopping the test when the steel rail object is not broken after the circulating pressure applied to the steel rail head by the vertical loading fixture reaches the specified cycle.

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