CN110542522A - A Dynamic Test Method for Stress Relaxation of Torsion Spring - Google Patents

Abstract

The invention relates to the field of stress testing of torsion springs, in particular to a dynamic testing method for stress relaxation of torsion springs. The computer program is used to control the cyclic load loading mode of the torsion testing machine to simulate the actual working conditions of the torsion spring. Each cycle contains several fretting cycles; according to the working conditions, within the range of the upper and lower torsion angles including the upper and lower limits, At any angle during the loading and/or unloading process, load the required number and amplitude of micro-motion cycles, measure the torque value of the torsion spring after multiple full cycles, and compare it with the initial torque value before the test to determine its stress relaxation behavior. The test method of the invention can accurately reflect the stress relaxation situation of the torsion spring in actual use, accurately predict the service life of the torsion spring, and has practical significance.

Description

A Dynamic Test Method for Stress Relaxation of Torsion Spring

technical field

The invention relates to the field of stress testing of torsion springs, in particular to a dynamic testing method for stress relaxation of torsion springs.

Background technique

For springs or other elastic elements, when they are subjected to static loads or dynamic alternating loads, the phenomenon that the bearing capacity decreases with the extension of the load time will occur, which is called stress relaxation or elastic decline. This is the spring and elastic elements in service. Common failure modes in the process. Therefore, testing and predicting the stress relaxation behavior of the spring is an important means to study the service life of the spring. Although, as early as 1868, J.c. Maxwell conducted relevant research on the law of stress relaxation and its influencing factors, but so far people have not established a unified theory on the mechanism and conditions of stress relaxation, and there is no general stress relaxation test method. my country issued the "Metal Stress Relaxation Test Method" (GB10120-88) in 1988, but it is only a standard for metal materials such as bars for structural parts, and there is no standard for the use of spring products.

For spring products, stress relaxation test methods can be divided into two categories: static test and dynamic test. The former is widely used due to the simplicity of the device, but it is still difficult to evaluate the stress relaxation of various elastic elements or components working under complex stress states. It is not universal and cannot reflect the actual use of spring products. The dynamic test method is a more practical test method, because the test is required to be performed under cyclic load (that is, reciprocating motion within the range of the maximum load and the minimum load of the spring), the experimental device is complicated, time-consuming and troublesome, and is rarely used. use.

Contents of the invention

The purpose of the present invention is to provide a dynamic testing method for stress relaxation of torsion springs, which adopts a cyclic load loading method, simulates the actual working conditions of torsion springs and includes several fretting cycles, and solves the problem of large deviations in current torsion spring stress testing methods .

In order to solve the deficiencies in the prior art, the technical solution of the present invention is:

A dynamic test method for stress relaxation of torsion springs, using computer programs to control the cyclic load loading mode of torsion testing machines, simulating the actual working conditions of torsion springs, and including fretting cycles simulating actual working conditions in one cycle cycle; according to the use Working conditions, within the range of the upper and lower torsion angles including the upper and lower limits, at any angle during the loading and/or unloading process, the number of fretting cycles required for loading and the amplitude are compared with the initial torque value before the test to determine its stress relaxation behavior.

In the dynamic test method for the stress relaxation of the torsion spring, the torsion spring is controlled by a computer program to measure its torque value after each working cycle, and compared with the initial torque value before the test, if the torque value is lower than the minimum tolerance value of the torque value If the torque value is lower than x% of the minimum tolerance value of the torque value, continue the test until the specified working cycle is reached, and the test ends.

The dynamic testing method of described torsion spring stress relaxation, concrete steps are as follows:

(1) Prepare the torsion spring sample, and install the torsion spring on the fixture;

(2) According to the actual working conditions, determine the total cycle number N, the minimum torsion angle α, the maximum torsion angle β of the loading angle, the fretting angle θ, the amplitude △θ and the number of vibrations n, and the minimum tolerance value of the torque value x% ;

(3) According to the actual working conditions, twist the torsion spring to the minimum torsion angle;

(4) According to the actual working conditions, twist the torsion spring to the inching angle;

(5) According to the actual working conditions, do n times of fretting cycles with an amplitude of △θ near the fretting angle;

(6) According to the actual working conditions, if there are more than two fretting cycles, repeat the above steps 4-5;

(7) According to the actual working conditions, load the torsion spring to the maximum torsion angle, measure the torque value, and compare it with the initial torque value before the test. If the torque value decreases by more than x% of the minimum tolerance value of the torque value, the test ends; If the torque value decreases by less than x% of the minimum tolerance value of the torque value, continue the test;

(8) Repeat steps 3 to 7 above until the number of cycles reaches the total number of cycles N, and the test ends.

The dynamic testing method of described torsion spring stress relaxation, the composition and structure of fixture are as follows:

The fixture consists of three parts: collet A, collet B and core rod. The outer end of collet A is connected to the driven collet end of the torsion testing machine. The size and shape of the outer end of collet A are determined by the driven collet of the torsion testing machine The size and shape of the end are determined; the inner end of the chuck A is connected to the end of the torsion spring, and the size and shape of the inner end of the chuck A are determined by the size and shape of the end of the torsion spring; the outer end of the chuck B is connected to the active clamp of the torsion testing machine The head end is connected, and the size and shape of the outer end of chuck B are determined by the active chuck end of the torsion testing machine; the inner end of chuck B is connected with the end of the torsion spring, and the size and shape of the inner end of chuck B are determined by the size of the end of the torsion spring and the shape is determined; the two ends of the core rod are respectively connected with the collet A and the collet B, and the torsion spring is sleeved on the core rod and connected with the inner sides of the collet A and the collet B respectively.

In the dynamic test method for stress relaxation of torsion springs, the total number of cycles N is ≥ 10, the minimum torsion angle α of the loading angle is 1° to 36000°, and the maximum torsion angle β of the loading angle is 1° to 36000°. The dynamic angle θ is α≤θ≤β, the amplitude Δθ is ≤0.4(β-α), the number of vibrations n is ≥2, and the minimum tolerance value x% of the torque value is ≤50%.

In the dynamic test method for the stress relaxation of the torsion spring, the material and shape of the torsion spring are not limited.

In the dynamic test method for the stress relaxation of the torsion spring, the size of the torsion spring sample and the size of the fixture are adjusted according to needs, and are not limited by each other.

The dynamic test method for the stress relaxation of the torsion spring can measure and record the torque value corresponding to the torsion angle in real time, and can reflect the stress relaxation situation of the torsion spring in real time when it is used.

Design idea of the present invention is:

Torsion springs (torsion springs) are used in various mechanisms to withstand torsional moments, and are one of the commonly used spring types. It has a wide range of uses, ranging from aircraft and warships to mobile phones and cameras and other products that use torsion springs. In actual use, the working condition of the torsion spring is to make a reciprocating motion between the minimum torsion angle and the maximum torsion angle. In a cycle of reciprocating motion, it often includes in the process of loading and (or) unloading, in the minimum Small vibrations at some or a specific twist angle between the twist angle and the maximum twist angle. Therefore, in order to test the stress relaxation behavior of the torsion spring under actual use conditions and accurately predict the service life of the torsion spring, the present invention proposes a dynamic test method for stress relaxation of the torsion spring, which can simulate the actual use conditions of the torsion spring. During the test, the torsion spring not only makes periodic reciprocating rotations between the minimum torsion angle and the maximum torsion angle, but also includes a small torsion at some or a specific torsion angle during the loading and (or) unloading process. vibration behavior.

The torsion spring is installed on the torsion testing machine through a special installation fixture. The special installation fixture is designed and manufactured according to the shape and size of the end of the torsion spring. This test method can simulate the stress relaxation of a torsion spring of any size and shape under actual working conditions. Behavior. The test process adopts the computer program to control the torsion testing machine for cyclic load loading. The test parameters are determined according to the actual use conditions of the torsion spring, including the loading cycle of the full cyclic load, the minimum torsion angle, the maximum torsion angle, the fretting angle and Its amplitude and frequency of vibration, as well as the minimum tolerance value of torsion spring torque value, etc.

Advantage of the present invention and beneficial effect are:

1. The cyclic load loading of the present invention includes several fretting cycles, and its function and effect are: to simulate the actual working conditions of the torsion spring, to perform periodic reciprocating rotation between the minimum torsion angle and the maximum torsion angle, and also included in the loading And (or) multiple small-angle vibration behaviors at some or a specific torsion angle during the unloading process.

2. The present invention can accurately measure and record the torque value corresponding to the torsion angle in real time.

3. The test method of the present invention can accurately reflect the stress relaxation situation of the torsion spring with any size and shape during actual use, and accurately predict the service life of the torsion spring.

Description of drawings

Figure 1 is the working cycle curve of each cycle. In the figure, the abscissa N represents the cycle number (Cycle), and the ordinate Torsion angle represents the torsion angle (°).

Figure 2 is the 188° torque value curve of the 1st to 20000th cycle. In the figure, the abscissa N represents the number of cycles (Cycle), and the ordinate Torque represents the torsion spring torque (Nm).

Figure 3 is the working cycle curve of each cycle.

Figure 4 is the 142° torque value curve of the 1st to 15,000 cycles.

Figure 5 is a schematic diagram of the structure of the torsion spring clamp. In the figure, 1. Chuck A, 2. Chuck B, 3. Core rod.

Detailed ways

In the specific implementation process, the dynamic testing method for the stress relaxation of the torsion spring of the present invention uses a computer program to control the cyclic load loading mode of the torsion testing machine to simulate the actual working conditions of the torsion spring. A cycle cycle includes several fretting cycles simulating actual working conditions, the specific steps are as follows:

1. Prepare the torsion spring sample and the special installation fixture as shown in Figure 5. The composition and structure of the fixture are as follows:

The fixture is composed of chuck A1, chuck B2, and core rod 3. The outer end of chuck A1 is connected to the driven chuck end of the torsion testing machine. The size and shape of the outer end of chuck A1 are determined by the driven chuck of the torsion testing machine. The size and shape of the head end is determined. The inner end of the chuck A1 is connected to the end of the torsion spring, and the size and shape of the inner end of the chuck A1 are determined by the size and shape of the end of the torsion spring. The outer end of the chuck B2 is connected to the active chuck end of the torsion testing machine, and the size and shape of the outer end of the chuck B2 are determined by the active chuck end of the torsion testing machine. The inner end of the chuck B2 is connected to the end of the torsion spring, and the size and shape of the inner end of the chuck B2 are determined by the size and shape of the end of the torsion spring. The two ends of the core rod 3 are respectively connected with the collet A1 and the collet B2, and the torsion spring is sleeved on the core rod 3 and respectively connected with the inner sides of the collet A1 and the collet B2, and the height of the core rod 3 is determined by the working height of the torsion spring.

The effect that special-purpose mounting fixture of the present invention plays and the effect that reaches are as follows:

The inner end of the collet A1 is connected with the end of the torsion spring, and the end of the torsion spring is fixed inside the collet A1. After eliminating the assembly gap, the synchronous rotation of the end of the torsion spring and the collet A1 can be realized. The outer end of the chuck A1 is connected with the driven chuck end of the torsion testing machine, and the outer end of the chuck A1 is fixed inside the driven chuck end of the torsion testing machine. After eliminating the assembly gap, the connection between the chuck A1 and the torsion testing machine can be realized. The synchronous rotation of the driven chuck is to realize the synchronous rotation of the end of the torsion spring and the driven chuck of the torsion testing machine. The inner end of the collet B2 is connected with the end of the torsion spring, and the end of the torsion spring is fixed inside the collet B2. After eliminating the assembly gap, the synchronous rotation of the end of the torsion spring and the collet B2 can be realized. The outer end of the chuck B2 is connected with the active chuck end of the torsion testing machine, and the outer end of the chuck B2 is fixed inside the active chuck end of the torsion testing machine. After eliminating the assembly gap, the chuck B2 and the active chuck of the torsion testing machine can be realized. The synchronous rotation of the head, that is, the synchronous rotation of the end of the torsion spring and the active chuck of the torsion testing machine. Put the torsion spring on the core rod 3, and install it on the inner side of the chuck A1 and the chuck B2 at the same time, so that the installation height of the torsion spring is the working height of the torsion spring. The two ends of the core rod 3 are respectively connected with the collet A1 and the collet B2 to ensure the coaxiality of the collet A1 and the collet B2. The special installation fixture can realize the synchronous rotation of the torsion spring and the torsion testing machine, and ensure the coaxiality of the torsion spring and the torsion testing machine.

2. According to the actual working conditions, determine the total cycle times N, the minimum torsion angle α, the maximum torsion angle β of the loading angle, the fretting angle θ, the amplitude △θ and the number of vibrations n, and the minimum tolerance value of the torque value x%; Among them, the total number of cycles N is ≥ 10, the minimum torsion angle α of the loading angle is 1° to 36000°, the maximum torsion angle β of the loading angle is 1° to 36000°, and the fretting angle θ is α≤θ≤β, The amplitude △θ is ≤0.4(β-α), the number of vibrations n is ≥2, and the minimum tolerance value x% of the torque value is ≤50%;

3. According to the actual working conditions, twist the torsion spring to the minimum torsion angle;

4. According to the actual working conditions, twist the torsion spring to the inching angle;

5. According to the actual working conditions, do n times of fretting cycles with an amplitude of △θ near the fretting angle. Do n times of vibration behavior at △θ angle nearby;

6. According to the actual working conditions, if there are multiple fretting cycles, repeat the above steps 4-5;

7. According to the actual working conditions, load the torsion spring to the maximum torsion angle, measure the torque value, and compare it with the initial torque value before the test. If the torque value decreases by more than x%, the test ends; if the torque value decreases by less than x% , to continue the test;

8. Repeat steps 3 to 7 above until the number of cycles reaches the total number of cycles N, and the test ends.

The above scheme will be further described below in conjunction with specific examples. It should be noted that these examples are only for illustrating the present invention and do not limit the scope of the present invention. All research schemes carried out based on the present invention (behaviors of making equivalent changes and improvements) should belong to the protection scope of the present invention.

Example 1:

In this embodiment, the actual working condition parameters of the torsion spring are shown in Table 1 below. The torsion spring has completed 20,000 working cycle stress relaxation tests in total, and the working cycle curve of each cycle is shown in Figure 1. As can be seen from Table 1 and Figure 1, The actual working condition of the torsion spring is: first load the torsion spring to the minimum torsion angle of 97° → vibrate 7 times near (97°±15°), and finally stop at 97° → continue to load the torsion spring to 143°, and There are (143±10)°vibrations for 5 times, and finally stop at the fretting angle of 143°→continue to load to the maximum torsion angle of 188°→unload to the minimum torsion angle of 97°. After each working cycle of the torsion spring, measure the torque value of its maximum torsion angle of 188°, and compare it with the initial torque value before the test. If the torque value decreases by more than 5%, the test ends; if the torque value decreases by less than 5%, continue The test ends after 20,000 working cycles are completed.

Table 1 Actual working condition parameters of torsion spring

1 to 20,000 working cycles, the torque value curve of 188° in each cycle is shown in Figure 2, and the torque test results before and after the stress relaxation test of the torsion spring are shown in Table 2. It can be seen from Figure 2 and Table 2 that the torsion spring has passed through 20,000 The torque value changes +0.1% after one cycle of working cycle, indicating that the torsion spring has no stress relaxation after 20,000 cycles of full cycle test, meets the requirement of the minimum tolerance of torque value <5%, and the torsion spring has not failed.

Table 2 Test results of torque before and after torsion spring stress relaxation test

Example 2:

In this embodiment, the parameters of the actual operating conditions of the torsion spring are shown in Table 3 below. The torsion spring has completed 15,000 working cycle stress relaxation tests in total. The working cycle curve of each cycle is shown in Figure 3. As can be seen from Table 3 and Figure 3, The actual working condition of the torsion spring is: first load the torsion spring to the minimum torsion angle of 82°→continue to load to the micro-motion angle of 107°→vibrate 14 times around (107°±10°), and finally stop at the micro-motion angle 107°→continue to load to the maximum torsion angle of 142°→unload to the minimum torsion angle of 82°. After each working cycle of the torsion spring, measure the torque value of its maximum torsion angle of 142°, and compare it with the initial torque value before the test. If the torque value decreases by more than 10%, the test ends; if the torque value decreases by less than 10%, continue The test ends after 15,000 working cycles are completed.

Table 3 Actual working condition parameters of torsion spring

The torque value curve of 142° in each cycle from 1 to 15,000 times is shown in Figure 4, and the test results of the torque before and after the torsion spring stress relaxation test are shown in Table 4. It can be seen from Figure 4 and Table 4 that the torsion spring has worked 15,000 times After the cycle, the torque value changes by +0.4%, indicating that the torsion spring has no stress relaxation after 15,000 cycles of the full cycle test, and the torsion spring has not failed.

Table 4 Torque inspection results before and after torsion spring stress relaxation test

The result of the embodiment shows that the present invention adopts the computer program to control the cyclic load loading mode of the torsion testing machine to simulate the actual working conditions of the torsion spring. Each cycle includes several micro-movement cycles, and the torsion spring passes through multiple rounds of full cycles. Measure the torque value and compare it with the initial torque value before the test to determine its stress relaxation behavior. The test method of the invention can accurately reflect the stress relaxation situation of the torsion spring in actual use, accurately predict the service life of the torsion spring, and has practical significance.

Claims (8)

1. a dynamic testing method of torsion spring stress relaxation, it is characterized in that, adopt computer program control torsion testing machine cyclic load loading mode, simulate the actual working condition of torsion spring, comprise the simulation of actual working condition in the cycle of a cycle Micro-movement cycle; according to the working conditions, within the range of the upper and lower limit torsion angles including the upper and lower limits, at any angle during the loading and/or unloading process, load the required number of times and amplitude of the fretting cycle, and compare with the initial test before the test Torque values were compared to determine its stress relaxation behavior. 2. the dynamic testing method of torsion spring stress relaxation according to claim 1, is characterized in that, after torsion spring every working cycle, all is measured its torque value by computer program control, and compares with the initial torque value before test, If the torque value decreases by more than x% of the minimum tolerance value of the torque value, the test ends; if the torque value decreases by less than x% of the minimum tolerance value of the torque value, the test continues until the specified working cycle is reached, and the test ends. 3. the dynamic testing method of torsion spring stress relaxation according to claim 1, is characterized in that, concrete steps are as follows: (1) Prepare the torsion spring sample, and install the torsion spring on the fixture; (2) According to the actual working conditions, determine the total cycle number N, the minimum torsion angle α, the maximum torsion angle β of the loading angle, the fretting angle θ, the amplitude △θ and the number of vibrations n, and the minimum tolerance value of the torque value x% ; (3) According to the actual working conditions, twist the torsion spring to the minimum torsion angle; (4) According to the actual working conditions, twist the torsion spring to the inching angle; (5) According to the actual working conditions, do n times of fretting cycles with an amplitude of △θ near the fretting angle; (6) According to the actual working conditions, if there are more than two fretting cycles, repeat the above steps 4-5; (7) According to the actual working conditions, load the torsion spring to the maximum torsion angle, measure the torque value, and compare it with the initial torque value before the test. If the torque value decreases by more than x% of the minimum tolerance value of the torque value, the test ends; If the torque value decreases by less than x% of the minimum tolerance value of the torque value, continue the test; (8) Repeat steps 3 to 7 above until the number of cycles reaches the total number of cycles N, and the test ends. 4. the dynamic testing method of torsion spring stress relaxation according to claim 3, is characterized in that, the composition and structure of fixture are as follows: The fixture consists of three parts: collet A, collet B and core rod. The outer end of collet A is connected to the driven collet end of the torsion testing machine. The size and shape of the outer end of collet A are determined by the driven collet of the torsion testing machine The size and shape of the end are determined; the inner end of the chuck A is connected to the end of the torsion spring, and the size and shape of the inner end of the chuck A are determined by the size and shape of the end of the torsion spring; the outer end of the chuck B is connected to the active clamp of the torsion testing machine The head end is connected, and the size and shape of the outer end of chuck B are determined by the active chuck end of the torsion testing machine; the inner end of chuck B is connected with the end of the torsion spring, and the size and shape of the inner end of chuck B are determined by the size of the end of the torsion spring and the shape is determined; the two ends of the core rod are respectively connected with the collet A and the collet B, and the torsion spring is sleeved on the core rod and connected with the inner sides of the collet A and the collet B respectively. 5. The dynamic testing method of torsion spring stress relaxation according to claim 3, characterized in that the total cycle times N is ≥ 10, the minimum torsion angle α of the loading angle is 1°～36000°, and the maximum torsion angle of the loading angle is 1°～36000°. The angle β is 1°～36000°, the fretting angle θ is α≤θ≤β, the amplitude △θ is ≤0.4(β-α), the number of vibrations n is ≥2, and the minimum tolerance value x% of the torque value is ≤50 %. 6. The dynamic testing method for stress relaxation of a torsion spring according to any one of claims 1 to 5, wherein the material and shape of the torsion spring are not limited. 7. The dynamic test method for stress relaxation of torsion spring according to any one of claims 1 to 5, characterized in that the size of the torsion spring sample and the size of the fixture are adjusted as required and are not limited to each other. 8. The dynamic testing method for stress relaxation of a torsion spring according to any one of claims 1 to 5, characterized in that the torque value corresponding to the torsion angle can be measured and recorded in real time, and the stress relaxation situation when the torsion spring is used can be reflected in real time.