Method for testing fatigue strength of back of brake shoe

Abstract

The invention relates to a method for testing the fatigue strength of the back of a brake shoe. The brake shoe comprises a brake shoe back and a friction body, and the brake shoe back comprises an inverted-T-shaped bend named as a brake shoe nose and bending points (a, a ', b and b'). The method comprises the following steps: fixing a brake shoe / brake shoe back; simulating a state that the brake shoe is limited in motion in a shoe holder; when a train is braked, the brake shoe bears thrust of the shoe holder; simulating tangential friction force of a wheel tread borne by the brake shoe by using force parallel to the length direction of the brake shoe, and simulating thrust of the shoe holder borne by the brake shoe by using force perpendicular to the length direction of the brake shoe; the brake-shoe nose reciprocates, and the bending part of the brake-shoe nose deforms repeatedly in a short time, so that fatigue is caused; the fatigue strength testing frequency of the brake shoe back is recorded through the counter, the fatigue condition of the brake shoe back is monitored through the monitor, and then the fatigue strength of the brake shoe back is judged. The inspection tool is simple in structure and easy and convenient to operate.

Description

Technical Field

[0001] The patent of this invention belongs to the technical field of brake shoe back strength detection, and relates to a method for testing the fatigue strength of brake shoe back. Background Art

[0002] With the development of safe, heavy-load and high-speed rail transit, synthetic brake shoes have become an important part of the braking system of rail transit vehicles in my country. When braking, the brake shoes rub against the wheel tread to achieve the purpose of deceleration and braking.

[0003] The composite brake shoe is mainly composed of a friction body and a brake shoe back (steel back), wherein the friction body plays a role of friction, and the brake shoe back plays a role of fixing the friction body. In actual train braking, the brake shoe is subjected to the thrust of the shoe support, and at the same time, the brake shoe is also subjected to the friction of the wheel tread. The friction of braking is very large, and the brake shoe reciprocates, and the brake shoe nose bend will produce repeated deformation. Under the combined effect of long-term alternating loads, working conditions, and road conditions, the deformation of the shoe nose bend of some brake shoe backs reaches a certain degree, causing fatigue, and then reaching the fatigue limit or even breaking, which seriously affects the safety of driving and causes unpredictable losses. In order to eliminate this possibility as much as possible, the fatigue strength of the brake shoe back needs to be tested during the brake shoe production process. The test of the fatigue strength of the brake shoe back is very necessary.

[0004] When the train brakes, the brake shoe is subjected to the thrust of the shoe support. The force parallel to the length direction of the brake shoe is used to simulate the tangential friction force of the wheel tread on the brake shoe, and the force perpendicular to the length direction of the brake shoe is used to simulate the thrust of the shoe support on the brake shoe, causing the brake shoe nose to produce reciprocating motion, and the bending part of the brake shoe nose to produce repeated deformation in a short period of time, which leads to fatigue.

[0005] However, up to now, there is no efficient and simple device and method for testing the fatigue strength of brake shoe back. Summary of the invention

[0006] Based on the above problems existing in the prior art, the present invention aims to provide a method for testing the fatigue strength of brake shoe back.

[0007] Based on the common causes of brake shoe nose fracture, this application designs a tooling imitating the brake shoe support, fixes the brake shoe / brake shoe back, simulates the state of the brake shoe being restricted in the shoe support, and the brake shoe is pushed by the shoe support when the train brakes. The force parallel to the brake shoe length direction is used to simulate the tangential friction force of the wheel tread on the brake shoe, and the force perpendicular to the brake shoe length direction is used to simulate the thrust of the shoe support on the brake shoe, so that the brake shoe nose produces reciprocating motion. In a short period of time, the brake shoe nose bend is repeatedly stressed and repeatedly deformed, and then fatigue occurs. This method is used to inspect the brake shoe back to improve product quality.

[0008] The technical solution of the present application provides a method for testing the fatigue strength of a brake shoe back, wherein the brake shoe comprises a brake shoe back and a friction body, and a "convex"-shaped bend on the brake shoe back is called a brake shoe nose; the steps of the method are:

[0009] Fix the brake shoe / brake shoe back on the workbench, apply reciprocating force parallel or perpendicular to the length direction of the brake shoe to the brake shoe / brake shoe back, so that the brake shoe nose bend is repeatedly stressed and deformed until fatigue occurs; record the number of fatigue strength tests of the brake shoe back through a counter, monitor the fatigue condition of the brake shoe back through a monitor, and then judge the fatigue strength of the brake shoe back.

[0010] This method simulates the state in which the movement of the brake shoe is restricted in the shoe support. When the train brakes, the brake shoe is subjected to the thrust of the shoe support. The force parallel to the length direction of the brake shoe is used to simulate the tangential friction force of the wheel tread on the brake shoe. The force perpendicular to the length direction of the brake shoe is used to simulate the thrust of the shoe support on the brake shoe. The brake shoe nose produces reciprocating motion, and the bending part of the brake shoe nose produces repeated deformation in a short period of time until fatigue occurs. The number of fatigue strength tests of the brake shoe back is recorded by a counter, and the fatigue condition of the brake shoe back is monitored by a monitor, so as to judge the fatigue strength of the brake shoe back.

[0011] Furthermore, the force parallel to the length direction of the brake shoe is used to simulate the tangential friction force of the wheel tread on the brake shoe, and the force perpendicular to the length direction of the brake shoe is used to simulate the thrust of the brake shoe on the brake shoe.

[0012] Furthermore, the brake shoe is fixed on a workbench, and repeated force is applied to the brake shoe in parallel to the length direction of the brake shoe, so that the bending part of the brake shoe nose is repeatedly stressed and deformed until fatigue occurs.

[0013] Furthermore, the two ends of the brake shoe / brake shoe back are fixed on a workbench, and repeated forces perpendicular to the length direction of the brake shoe are applied to the shoe nose of the brake shoe / brake shoe back, so that the bending part of the brake shoe nose is repeatedly stressed and deformed until fatigue occurs;

[0014] Fix one end of the brake shoe back on the workbench, and apply repeated force parallel to the length direction of the brake shoe back to the unfixed end, so that the bend of the brake shoe nose is repeatedly stressed and deformed until fatigue occurs.

[0015] Furthermore, the occurrence of fatigue refers to the occurrence of cracks or complete breakage of the brake shoe nose.

[0016] Fatigue refers to the phenomenon that metal materials gradually produce local permanent cumulative damage under the action of alternating stress or strain, and eventually lead to cracks or complete fractures after a certain number of cycles. When the brake shoe / brake shoe back is subjected to repeated forces parallel or perpendicular to the length of the brake shoe, the brake shoe nose bend is repeatedly subjected to repeated forces and is prone to repeated deformation, resulting in fatigue.

[0017] Furthermore, the reciprocating force is applied by an existing tension and compression fatigue testing machine, which can be commercially available or homemade, without too many restrictions on brands and models.

[0018] Furthermore, the counter is connected to the tension and compression fatigue testing machine to display the number of reciprocating cycles of force applied.

[0019] Furthermore, the monitor is installed at a position that ensures that the counter reading and the fatigue condition of the brake shoe nose can be seen.

[0020] Furthermore, the number of fatigue strength tests is an indicator of fatigue strength. When fatigue occurs on the brake shoe nose, the number displayed on the counter is read out, which is the number of fatigue strength tests on the brake shoe back.

[0021] In some embodiments of the present application, the qualified brake shoe verified by vehicle installation is used as a reference. The number of fatigue strength tests on the back of the qualified brake shoe is generally about 20,000-30,000 times. If the number of fatigue strength tests on the back of the brake shoe is not less than 20,000-30,000 times, it is considered qualified. In other embodiments not shown, the number of fatigue strength tests on different brake shoes is different. Some brake shoes will not break after more than 20,000-30,000 times, and some will break after less than 20,000-30,000 times. Therefore, this indicator should be set according to the actual situation. The innovation and beneficial effects of the patent of this invention:

[0022] (1) This application proposes for the first time a method for testing the fatigue strength of brake shoe backs. A fatigue strength test is performed on newly designed, purchased or produced brake shoe backs. If the number of fatigue strength tests does not meet the requirements of the number of fatigue strength tests of qualified brake shoe backs verified by vehicle installation or the number of fatigue strength tests required by the user, the brake shoe backs do not meet the standards. This method is used to perform fatigue strength tests on brake shoe backs to ensure that product quality is controlled.

[0023] (2) Simulate the thrust of the brake shoe during the train braking process, use a greater force than the existing working condition to repeatedly stress the brake shoe nose bend, produce repeated deformation, and reach the fatigue limit. For brake shoe backs with low fatigue strength resistance, the brake shoe backs will break quickly and cannot last for the required number of cycles. The present invention can test the fatigue strength of the brake shoe backs in a relatively short period of time (about 2-5 days, unqualified brake shoes will become fatigued in less than 2-5 days).

[0024] (3) The number of brake shoe back fatigue strength tests is recorded by a counter in the brake shoe back fatigue strength test device. The brake shoe nose fatigue condition and the number of brake shoe nose fatigue strength tests can be observed at any time through the monitoring device, so as to achieve the purpose of real-time monitoring of brake shoe nose fatigue.

[0025] (4) The brake shoe back fatigue strength test device in the present application has a simple structure, simple and convenient operation, easy processing, energy-saving and safe, and low cost. It can be completed without a 1:1 test bench with a wheel diameter of 700 to 1200 mm and a mass of several tons. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is the brake shoe force diagram;

[0027] Figure 2 Schematic diagram of the brake shoe nose fixing test device for brake shoe back fatigue strength in Example 1;

[0028] Figure 3 It is a schematic diagram of the brake shoe back fatigue strength brake shoe nose fixed pull frame sleeved into the brake shoe testing device in Example 1;

[0029] Figure 4 Schematic diagram of the brake shoe / brake shoe back end fixing inspection device for brake shoe / brake shoe back end fatigue strength in Example 2;

[0030] Figure 5 Schematic diagram of the brake shoe back fatigue strength brake shoe back unilateral fixing testing device in Example 3;

[0031] The marks in the figure indicate:

[0032] 1 friction body; 2 brake shoe back; 3 brake shoe nose; 4 brake shoe fixing frame; 5 centering rod; 6 pull frame; 7 first cross bar; 8 second cross bar; 9 third cross bar; 10 monitor; 11 counter. DETAILED DESCRIPTION

[0033] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is described in detail below in conjunction with specific embodiments. It should be noted that the following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, several variations and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0034] In the description of the present application, it should be noted that the terms "upper", "lower", "inner", "outer", "front end", "rear end", "two ends", "one end", "the other end" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as a limitation on the present application. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0035] Figure 1 This is a schematic diagram of the force on the brake shoe in this embodiment. The forces parallel and perpendicular to the length direction of the brake shoe are shown as reciprocating arrows in the figure. a, a' and b, b' are two pairs of symmetric bending points on the brake shoe nose, which are prone to breakage when stressed.

[0036] The present invention can be implemented by three methods, and the following specific embodiments are provided:

[0037] Embodiment 1: Fix the brake shoe nose and move the pull frame

[0038] The brake shoe includes a brake shoe back 2 and a friction body 1. The brake shoe is fixed on the brake shoe fixing bracket 4, and a tangential frictional force of the wheel tread during braking is simulated by a force parallel to the length direction of the brake shoe. The bending part of the brake shoe nose 3 is repeatedly stressed, resulting in repeated deformation until fatigue.

[0039] Reference Figure 2 、 Figure 3 , the specific steps are as follows:

[0040] (1) Place the brake shoe fixing bracket 4 on the workbench.

[0041] (2) Pass the centering rod 5 through the brake shoe pin hole on the brake shoe nose 3, and fix both ends of the centering rod 5 on the brake shoe fixing bracket 4.

[0042] (3) Put the pull frame 6 on the friction body 1 of the brake shoe. The shape of the pull frame 6 is "day" - shaped ( Figure 2 ), which just fits the friction body 1 of the brake shoe.

[0043] (4) The pull frame 6 moves up and down ( Figures 2-3 the arrow direction in the figure), the brake shoe nose 3 is repeatedly stressed, and repeated deformation occurs at the bending part of the brake shoe nose 3, resulting in fatigue.

[0044] (5) Through the counter 11, record the number of fatigue strength tests of the brake shoe back 2; through the monitor 10, the fatigue condition of the brake shoe nose 3 and the number of fatigue strength tests of the brake shoe nose 3 can be observed at any time, achieving the purpose of real - time monitoring of the fatigue of the brake shoe nose 3.

[0045] The brake shoe fixing bracket 4 plays a role in fixing the brake shoe; the appearance of the brake shoe fixing bracket 4 can adopt various forms as long as the brake shoe nose 3 can be fixed. The centering rod 5 plays a role in fixing the brake shoe nose 3. The pull frame 6 plays a role in fitting onto the brake shoe. The pull frame 6 moves up and down, causing the brake shoe nose 3 to be repeatedly stressed; the appearance of the pull frame 6 can adopt various forms. The inside of the pull frame can be "day" - shaped or "mouth" - shaped, not limited to the shape in the embodiment, as long as it can apply a reciprocating force to the brake shoe.

[0046] When the inside of the pull frame is "day" - shaped ( Figure 2 ) Specifically as follows:

[0047] The pulling frame moves upward:

[0048] (1) When the second crossbar 8 hits the B surface, deformations occur at points a and b.

[0049] (2) When the third crossbar 9 hits the D surface, deformations occur at points a' and b'.

[0050] The pulling frame moves downward:

[0051] (1) When the first crossbar 7 hits the A surface, deformations occur at points a and b.

[0052] (2) When the second crossbar 8 hits the C surface, deformations occur at points a' and b'.

[0053] When the inside of the pulling frame is in a "square" shape, it is equivalent to half of a "day" shape. If it is the upper half, specifically as follows:

[0054] The pulling frame moves upward: When the second crossbar 8 hits the B surface, deformations occur at points a and b.

[0055] The pulling frame moves downward: When the first crossbar 7 hits the A surface, deformations occur at points a and b.

[0056] When the pulling frame is placed in the lower half, it is the same principle.

[0057] Embodiment 2 Fix both ends of the fixed brake shoe / brake shoe back, and stretch / squeeze the brake shoe nose up and down

[0058] Fix both ends of the brake shoe or the brake shoe back 2 on the workbench, and apply a force perpendicular to the length direction of the brake shoe on the brake shoe nose 3. The bent part of the brake shoe nose 3 is repeatedly stressed, resulting in repeated deformations (such as Figure 4 , points a and a', points b and b' are both stressed and deformed), until fatigue.

[0059] Specific steps:

[0060] (1) Fix the brake shoe or the brake shoe back 2 on the workbench, and fix both ends of the brake shoe or the brake shoe back 2.

[0061] (2) Apply a force perpendicular to the length direction of the brake shoe on the brake shoe nose 3, so that the brake shoe nose 3 is subjected to a force perpendicular to the length direction of the brake shoe. The bent part of the brake shoe nose 3 is repeatedly stressed and deformed until fatigue.

[0062] (3) Through the counter 11, record the number of fatigue strength tests of the brake shoe back 2; through the monitor 10, the fatigue condition of the brake shoe nose 3 and the number of fatigue strength tests of the brake shoe nose 3 can be observed at any time, achieving the purpose of real-time monitoring of the fatigue of the brake shoe nose 3.

[0063] Example 3: Fix one end of the brake shoe back and stretch / extrude the other end

[0064] Fix one end of the brake shoe back 2 on the workbench, apply a force parallel to the length direction of the brake shoe back 2 to the unfixed end to stretch / extrude the brake shoe back 2, and the brake shoe nose 3 is repeatedly stressed and deformed (such as Figure 5 , points a and a′, points b and b′ are all subjected to force and deform) until fatigue.

[0065] Specific steps:

[0066] (1) Fix one end of the brake shoe back 2 on the workbench.

[0067] (2) Use a force parallel to the length direction of the brake shoe back 2 to stretch / squeeze the other unfixed end of the brake shoe back 2, causing repeated deformation at the bend of the brake shoe nose 3 until fatigue occurs.

[0068] (3) The counter 11 is used to record the number of fatigue strength tests on the brake shoe back 2; the monitor 10 is used to observe the fatigue condition of the brake shoe nose 3 and the number of fatigue strength tests on the brake shoe nose 3 at any time, thereby achieving the purpose of real-time monitoring of the fatigue of the brake shoe nose 3.

[0069] In the above three methods, the counter 11 is used to record the number of fatigue strength tests of the brake shoe nose 3. The monitor can observe the fatigue condition of the brake shoe nose 3 and the number of fatigue strength tests of the brake shoe nose 3 at any time, so as to achieve the purpose of real-time monitoring of the fatigue of the brake shoe nose 3.

[0070] The number of fatigue strength tests that the brake shoe back can withstand depends on each subway line and working conditions. The brake shoe back tested by the brake shoe back fatigue strength testing device of this patent is considered qualified as long as it can reach the number of fatigue strength tests of the qualified brake shoe back verified by loading.

[0071] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for testing the fatigue strength of brake shoe back, characterized in that: The brake shoe comprises a brake shoe back and a friction body, and a "convex"-shaped bend on the brake shoe back is called a brake shoe nose, and the method is characterized in that the steps are: Fix the brake shoe / brake shoe back on the workbench, apply reciprocating force parallel or perpendicular to the length direction of the brake shoe to the brake shoe / brake shoe back, so that the brake shoe nose bend is repeatedly stressed and deformed until fatigue occurs; record the number of fatigue strength tests of the brake shoe back through a counter, monitor the fatigue condition of the brake shoe back through a monitor, and then judge the fatigue strength of the brake shoe back.

2. A brake shoe back fatigue strength testing method according to claim 1, characterized in that: The force parallel to the length direction of the brake shoe is used to simulate the tangential friction force exerted on the brake shoe by the wheel tread, and the force perpendicular to the length direction of the brake shoe is used to simulate the thrust exerted on the brake shoe by the shoe support.

3. A brake shoe back fatigue strength testing method according to claim 1, characterized in that: The method comprises: fixing the brake shoe on a workbench, applying a reciprocating force parallel to the length direction of the brake shoe to the brake shoe, so that the brake shoe nose bending part is repeatedly stressed and deformed until fatigue occurs.

4. A brake shoe back fatigue strength testing method according to claim 1, characterized in that: The method comprises: fixing the two ends of the brake shoe / brake shoe back on a workbench, applying a reciprocating force perpendicular to the length direction of the brake shoe to the shoe nose of the brake shoe / brake shoe back, so that the bending part of the brake shoe nose is repeatedly stressed and deformed until fatigue occurs.

5. The method for testing the fatigue strength of brake shoe back according to claim 1, characterized in that: The method comprises: fixing one end of the brake shoe back on a workbench, applying a reciprocating force parallel to the length direction of the brake shoe back to the unfixed end, so that the brake shoe nose bending part is repeatedly stressed and deformed until fatigue occurs.

6. A brake shoe back fatigue strength testing method according to claim 1, characterized in that: in, The occurrence of fatigue refers to the occurrence of cracks or complete breakage of the brake shoe nose.

7. A brake shoe back fatigue strength testing method according to claim 1, characterized in that: in, The reciprocating force is achieved by a tension and compression fatigue testing machine.

8. A brake shoe back fatigue strength testing method according to claim 1, characterized in that: The counter is connected to the tension and compression fatigue testing machine to display the number of reciprocating cycle forces applied.

9. A brake shoe back fatigue strength testing method according to claim 1, characterized in that: The monitor is installed in a position that ensures that the reading of the counter and the fatigue condition of the brake shoe nose can be seen.

10. A brake shoe back fatigue strength testing method according to claim 1, characterized in that: The number of fatigue strength tests is an indicator of fatigue strength. When fatigue occurs to the brake shoe nose, the number displayed on the counter is read out, which is the number of fatigue strength tests on the brake shoe back.

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