A test method for fatigue strength of brake shoe back

Abstract

The present application relates to a method for testing the fatigue strength of a brake shoe back. The brake shoe includes a brake shoe back and a friction body. The brake shoe back includes a "convex"-shaped bend called a brake shoe nose, and the bend points are (a, a', b, b'); the method comprises the following steps: fixing the brake shoe / brake shoe back to simulate the state in which the brake shoe is restricted in movement within the shoe support. When the train brakes, the brake shoe is subjected to the thrust of the shoe support. A force parallel to the brake shoe length direction is used to simulate the tangential friction force of the wheel tread on the brake shoe. A force perpendicular to the brake shoe length direction is used to simulate the thrust of the shoe support on the brake shoe, causing the brake shoe nose to produce reciprocating motion. In a short period of time, the brake shoe nose bend undergoes repeated deformation, thereby causing fatigue; a counter is used to record the number of fatigue strength tests on the brake shoe back, and a monitor is used to monitor the fatigue condition of the brake shoe back, thereby determining the fatigue strength of the brake shoe back. The inspection tooling of the present application has a simple structure and is 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] Composite brake shoes are mainly composed of friction bodies and brake shoe backs (steel backs), in which the friction bodies play a role of friction, and the brake shoe backs play the role of fixing the friction bodies. In actual train braking, the brake shoes are pushed by the shoe support, and at the same time, the brake shoes are also subject to the friction of the wheel tread. The friction of braking is very large, and the brake shoes move back and forth. The bend of the brake shoe nose will produce repeated deformation. Under the combined effect of long-term alternating loads, working conditions and road conditions, the deformation of the bend of the shoe nose of individual 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 backs needs to be tested during the brake shoe production process. The test of the fatigue strength of the brake shoe backs is very necessary.

[0004] When the train brakes, the brake shoe is pushed by 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. In a short period of time, the bending part of the brake shoe nose will produce repeated deformation, and then fatigue will occur.

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

[0007] Based on the common causes of brake shoe nose fracture, this application designs a tooling that mimics the brake shoe support. This fixes the brake shoe / brake shoe back and simulates the state of the brake shoe's restricted movement within the shoe support. When the train brakes, the brake shoe is pushed by the shoe support. A force parallel to the brake shoe's length simulates the tangential friction force on the wheel tread on the brake shoe, and a force perpendicular to the brake shoe's length simulates the thrust of the shoe on the brake shoe. This causes the brake shoe nose to reciprocate, and the bend of the brake shoe nose is repeatedly stressed and deformed in a short period of time, leading to fatigue. This method is used to inspect the brake shoe back and 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 as follows:

[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 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 the workbench, and repeated force perpendicular to the length direction of the brake shoe is applied to the 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 in which metal materials gradually develop localized, permanent, and cumulative damage under alternating stress or strain, ultimately leading to cracks or complete fracture after a certain number of cycles. When the brake shoe or shoe back is subjected to repeated forces parallel or perpendicular to the shoe's length, the repeated stress on the shoe nose bend can easily cause repeated deformation and fatigue.

[0017] Furthermore, the reciprocating force is applied by an existing tensile and compressive fatigue testing machine, which can be commercially available or homemade, without excessive restrictions on brand and model.

[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 reading of the counter 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 number of fatigue strength tests on the back of a qualified brake shoe that has been verified by vehicle installation is used as a reference. The number of times the back of a qualified brake shoe is tested for fatigue strength is generally around 20,000 to 30,000 times. If the number of fatigue strength tests on the back of a brake shoe is not less than 20,000 to 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 to 30,000 times, while others will break after less than 20,000 to 30,000 times. Therefore, this indicator should be set according to actual conditions. The innovation and beneficial effects of the present invention are as follows:

[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 conducted on newly designed, purchased, or produced brake shoe backs. If the fatigue strength test number does not meet the fatigue strength test number required by the user or the number of fatigue strength tests required by the user, the brake shoe backs do not meet the standard. This method is used to test the fatigue strength of brake shoe backs to ensure product quality control.

[0023] (2) Simulating the thrust of the brake shoe during the train braking process, a greater force than the existing working condition is used to repeatedly stress the bend of the brake shoe nose, resulting in repeated deformation and reaching the fatigue limit. For brake shoe backs with low fatigue strength, the brake shoe backs will break quickly and cannot withstand 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 fatigue 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 testing 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, thereby achieving the purpose of real-time monitoring of brake shoe nose fatigue.

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

[0026] Figure 1 It is a schematic diagram of brake shoe force;

[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 Schematic diagram of the brake shoe back fatigue strength test device in Example 1, in which the brake shoe nose fixed pull frame is inserted into the brake shoe;

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

[0030] Figure 5 Schematic diagram of the brake shoe back fatigue strength unilateral fixation test 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 with reference to specific embodiments. It should be noted that the following embodiments will help those skilled in the art to further understand the present invention, but are not intended to 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 be made without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0034] In the description of this 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, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended only to facilitate the description of this application and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this application. Those skilled in the art will understand the specific meanings of the above terms in this application based on 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 a brake shoe fixing frame 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 , specific steps:

[0040] (1) Place the brake shoe fixing frame 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 frame 4.

[0042] (3) Slip the pull frame 6 over 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 in 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 frame 4 serves to fix the brake shoe; the appearance of the brake shoe fixing frame 4 can take various forms as long as the brake shoe nose 3 is fixed. The centering rod 5 serves to fix the brake shoe nose 3. The pull frame 6 serves to slip over the brake shoe, and the pull frame 6 moves up and down to repeatedly stress the brake shoe nose 3; the appearance of the pull frame 6 can take various forms, and the inside of the pull frame can be "day" shaped or "mouth" shaped, not limited to the shape in the embodiment, as long as a reciprocating force can be applied 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 impacts the B surface, deformations occur at point a and point b.

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

[0050] The pulling frame moves downward:

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

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

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

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

[0057] Example 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 , both point a and point a', point b and point b' are stressed and deformed), until fatigue. [[ID=4l]]

[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 test times 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 test times 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. [[ID=SI]]

[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 deformed) 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 / extrude 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 number of fatigue strength tests of the brake shoe back 2 is recorded through the counter 11; 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 through the monitor 10, so as to achieve 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 fatigue strength testing device of this patent is considered qualified as long as the brake shoe back can reach the number of fatigue strength tests of the qualified brake shoe back verified by installation.

[0071] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. 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 (2) and a friction body (1), wherein a convex bend on the brake shoe back (2) is called a brake shoe nose (3), and the method comprises the following steps: Fix the brake shoe or the brake shoe back (2) on a workbench, apply a reciprocating force parallel to or perpendicular to the length direction of the brake shoe to the brake shoe or the brake shoe back (2), so that the brake shoe nose (3) is repeatedly stressed and deformed until fatigue occurs; record the number of fatigue strength tests of the brake shoe back (2) by a counter (11), monitor the fatigue condition of the brake shoe back (2) by a monitor (10), and then judge the fatigue strength of the brake shoe back (2); The fatigue mentioned above refers to the occurrence of cracks or complete fracture of the brake shoe nose (3); Depending on the direction of the applied force, the method selects any one of the following three methods: (1) Fix the brake shoe on a workbench and apply a reciprocating force parallel to the length of the brake shoe to the brake shoe so that the brake shoe nose (3) is repeatedly stressed and deformed until fatigue occurs; Specifically, the brake shoe nose (3) is fixed and the pull frame (6) is moved: the brake shoe fixing frame (4) is placed on the workbench, and then the centering rod (5) is passed through the brake drill hole on the brake shoe nose (3), and the two ends of the centering rod (5) are fixed on the brake shoe fixing frame (4); the pull frame (6) is put on the friction body (1) of the brake shoe; the pull frame (6) moves up and down, the brake shoe nose (3) is repeatedly stressed, and the bending part of the brake shoe nose (3) is repeatedly deformed, causing fatigue; (2) Fixing both ends of the brake shoe or the brake shoe back (2) on a workbench, applying a reciprocating force perpendicular to the length direction of the brake shoe to the brake shoe nose (3), so that the bend of the brake shoe nose (3) is repeatedly stressed and deformed until fatigue occurs; Specifically, the brake shoe or the brake shoe back (2) is fixed at both ends, and the brake shoe nose (3) is stretched or squeezed up and down: the brake shoe or the brake shoe back (2) is fixed on the workbench, and the brake shoe or the brake shoe back (2) is fixed at both ends; a force perpendicular to the length direction of the brake shoe is applied to the brake shoe nose (3), so that the brake shoe nose (3) is subjected to the force perpendicular to the length direction of the brake shoe, and the bending part of the brake shoe nose (3) is repeatedly subjected to the force to produce repeated deformation until fatigue occurs; (3) Fixing one end of the brake shoe back (2) on a workbench, and applying a reciprocating force parallel to the length direction of the brake shoe back (2) to the unfixed end, so that the bend of the brake shoe nose (3) is repeatedly stressed and deformed until fatigue occurs; Specifically, one end of the brake shoe back (2) is fixed, and the other end is stretched or squeezed: one end of the brake shoe back (2) is fixed on a workbench, and a force parallel to the length direction of the brake shoe back (2) is used to stretch or squeeze the other end of the brake shoe back (2) that is not fixed, so that the bending part of the brake shoe nose (3) is repeatedly deformed until fatigue occurs.

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

4. The method for testing the fatigue strength of the brake shoe back according to claim 1, characterized in that: The counter (11) is connected to the tension and compression fatigue testing machine and is used to display the number of reciprocating cycle forces applied.

5. The method for testing the fatigue strength of the brake shoe back according to claim 1, characterized in that: The monitor (10) is installed in a position that ensures that the reading of the counter (11) and the fatigue condition of the brake shoe nose (3) can be seen.

6. The method for testing the fatigue strength of the brake shoe back according to claim 1, characterized in that: The number of fatigue strength tests is an indicator of fatigue strength. When fatigue occurs on the brake shoe nose (3), the number displayed on the counter (11) is read out, and this number is the number of fatigue strength tests on the brake shoe back (2).

Images