CN105067236B - A kind of dry friction damping shock absorber major error monitoring method - Google Patents

Abstract

The invention provides a main fault monitoring system of a dry friction damping shock absorber, which includes a detection module, a control module, an alarm module and a real-time monitoring module for performing fault detection on the dry friction damping shock absorber; the detection module detects the shock absorption in real time The control module compares the number of uses with the previously set threshold. If the number of uses reaches the previously set threshold, the alarm module sends an alarm. The real-time monitoring module checks the shock absorber to determine whether to replace the shock absorber. device. According to the set threshold, the present invention compares the shock absorber usage threshold with the actually measured shock absorber usage times. If the shock absorber actual usage times reaches the threshold, the control module controls the alarm module to give an alarm to determine whether to replace the shock absorber. Ensure the safety of aviation equipment.

Description

A Main Fault Monitoring Method of Dry Friction Damping Shock Absorber

technical field

The invention relates to the field of avionics equipment, in particular to a main fault monitoring method of a dry friction damping shock absorber.

Background technique

Avionics equipment may be subject to strong vibration during work. In order to isolate and protect electronic equipment from vibration, shock absorbers are generally installed on these equipment. The normal operation of the shock absorber is a powerful guarantee for the continuous and normal operation of electronic equipment in harsh vibration environments. The vibration reduction effect of the shock absorber will directly affect the operation of electronic equipment. If the shock absorber of aviation equipment does not work properly, it will increase the vibration stress on the electronic equipment, accelerate the degradation of the electronic equipment and even cause it to malfunction, resulting in safety problems.

Therefore, it is very important to predict and improve the life of the shock absorber to ensure the safe operation of aviation equipment, but there is no systematic method for life prediction of the dry friction damping shock absorber in the prior art, resulting in the inability to grasp the dry friction damping The life of the shock absorber makes it impossible to replace the shock absorber in time according to the predicted life of the dry friction damping shock absorber to ensure the normal operation of the equipment.

Therefore, the fault monitoring and timely improvement of the shock absorber are very important to ensure the safe and reliable operation of the avionics equipment.

Contents of the invention

In order to solve the determination of the existence of the fault monitoring of the existing dry friction damping shock absorber mentioned above, the present invention provides a main fault monitoring system and method of the dry friction damping shock absorber, by calculating and comparing the dry friction damping shock absorber The life of the dry friction damping shock absorber is determined by the number of damping springs and damping plates in the shock absorber, and the maximum use threshold of the shock absorber is set according to the determined service life of the shock absorber, which is related to the actual use of the shock absorber In comparison, the work of the aviation equipment shock absorber is monitored to ensure the normal operation of the aviation equipment shock absorber.

Specifically, a main fault monitoring system of a dry friction damping shock absorber, the main fault monitoring system includes a detection module, a control module, an alarm module and a real-time monitoring module for performing fault detection on a dry friction damping shock absorber;

Detection module: including the shock absorber usage times measurement unit and the detection result output module, the shock absorber usage times measurement unit detects the actual usage times of the shock absorber, and the detection result output module is based on the detection results of the shock absorber usage times measurement unit Send the actual number of uses of the shock absorber to the control module;

The control module includes a micro-controller and a shock absorber usage threshold setting module. The shock absorber usage threshold setting module measures the shock absorber maximum usage threshold and sends the threshold to the microcontroller. The maximum use times threshold of the shock absorber is stored, and the actual use times of the shock absorber is compared with the maximum use times threshold of the shock absorber. When the actual use times of the shock absorber reaches the maximum use number threshold of the shock absorber, the control module sends The alarm module sends an alarm signal, and the alarm module sends an alarm;

The real-time monitoring module detects the shock absorber according to the alarm signal of the alarm module, judges its failure, and sends out a signal to replace the shock absorber.

Preferably, the shock absorber use times threshold setting module includes a damping plate use count measuring unit for measuring the shock absorber damping plate maximum use counts and a spring use count measuring unit for measuring the shock absorber spring maximum use counts.

Preferably, a method for monitoring main faults of a dry friction damping shock absorber according to the above system, comprising the following steps:

S1. The shock absorber use times threshold setting module measures the service life of the shock absorber to obtain the shock absorber maximum use number threshold, specifically including the following steps:

① The measuring unit for the number of times of use of the damping plate detects the maximum number of times of use of the damping plate of the shock absorber;

②The measuring unit of the number of times of spring use detects the maximum number of times of use of the shock absorber spring;

③The shock absorber use times threshold setting module compares the measured maximum use times of the shock absorber damping plate with the shock absorber spring maximum use times, and determines the shock absorber maximum use number threshold;

S2. The detection module monitors the actual number of times of use of the shock absorber in real time, and uploads the actual number of times of use of the shock absorber to the control module;

S3. The microcontroller compares the actual number of times of use of the shock absorber with the threshold of the maximum number of times of use of the shock absorber. When the actual number of times of use of the shock absorber reaches the threshold of the maximum number of times of use of the shock absorber, the control module sends an alarm signal to the alarm module. , the alarm module sends out an alarm;

S4. The real-time monitoring module detects the shock absorber according to the alarm signal of the alarm module, judges the failure of the shock absorber, and sends a signal to replace the shock absorber.

Preferably, the method for detecting the maximum number of times of use of the shock absorber damping sheet by the measuring unit for the number of times of use of the damping sheet includes the following steps:

Step 1: Calculate the tangential relative slip distance between the shock absorber damping plate and the shock absorber shell: the shock absorber damping plate and the inner wall of the shock absorber shell form a pair of friction pairs, using the Archard adhesive wear model, the damping The tangential relative slip distance between the damping plate of the shock absorber and the shock absorber shell, the calculation formula is as follows:

In the formula, L is the tangential relative sliding distance between the damping plate of the shock absorber and the shock absorber shell, h is the wear depth index of the damping plate, A _a is the contact area between the damping plate of the shock absorber and the shock absorber shell, H is the HRC hardness of the inner wall of the shock absorber shell, K is the wear factor, and P is the normal pressure between the damping plate of the shock absorber and the inner wall of the shock absorber;

Step 2: Calculate the single slip distance of the damping plate of the shock absorber: the single slip distance of the damping plate of the shock absorber is l, the maximum compression amount of the shock absorber spring is C _max and the minimum compression amount is C _min , then The single slip distance of the shock absorber damping plate is as follows:

l=2( _Cmax - _Cmin );

Step 3: Calculate the maximum usage times of the friction shock absorber damping plate:

Divide the tangential relative slip distance between the shock absorber damping plate and the shock absorber shell calculated in step 1 by the single slip distance of the shock absorber damping plate calculated in step 2 to obtain the maximum value of the shock absorber damping plate The calculation formula is as follows:

In the formula, N ₁ is the maximum number of times of use of the damping plate of the shock absorber.

Preferably, the determination process of each parameter in step 1 is as follows:

①Define the index of the wear depth of the damping plate of the shock absorber as h;

②Calculate the contact area between the damping sheet of the shock absorber and the shock absorber shell, A _a = πd·t

In the formula, A _a is the contact area between the shock absorber damping plate and the shock absorber shell, d is the inner diameter of the shock absorber shell, and t is the thickness of the damping plate;

③Measure the HRC hardness of the inner wall of the shock absorber shell: fix the shock absorber shell, then use a ring cutter to rotate the shock absorber shell to cut and sample, and use a friction and wear instrument to measure the HRC hardness of the inner wall of the shock absorber shell ;

④Measure the normal pressure between the damping plate of the shock absorber and the inner wall of the shock absorber shell: fix the sample of the shock absorber shell on the friction and wear tester, and press the damping plate of the shock absorber to the inner wall of the shock absorber shell. Put the indenter in contact with the shock absorber shell to be measured, set the expected displacement and its falling time, make the indenter drop very slowly, simulate the effect of static load, and determine the damping of the shock absorber from multiple test results The normal pressure between the plate and the inner wall of the shock absorber shell when they are in full contact;

⑤ Calculation of wear coefficient K, the calculation formula of wear coefficient K is as follows:

lgK＝5lgμ-2.27

In the formula, μ is the friction coefficient between the damping sheet of the shock absorber and the inner wall of the shock absorber shell.

Preferably, the method for detecting the maximum number of uses of the shock absorber spring by the measuring unit of the number of times of use of the spring includes the following steps:

Step 1: Determine the static load of the shock absorber spring: the static load of the shock absorber spring includes the prestress and load pressure of the shock absorber installation, where: the calculation method of the load pressure is as follows:

F ₁ ＝m×g÷n, where F ₁ is the load pressure, m is the load mass, and n is the number of shock absorber springs;

The calculation method for the prestress of the shock absorber installation is as follows:

First measure the compression length of the shock absorber spring in the assembly, and then use the wear tester to obtain the force-displacement curve of the spring. According to the force-displacement curve of the spring, the pressure on the spring when compressed is obtained, which is recorded as F ₂ .

The calculation method of spring static load is as follows:

F _s =F ₁ +F ₂ ;

Step 2: Perform finite element modeling on the shock absorber spring: the specific steps are as follows:

①Static modeling of dry friction damping shock absorber:

The dry friction damping shock absorber is modeled statically, the structural relationship diagram of the dry friction damping shock absorber is obtained, and the modal model with static load and boundary conditions as prestress is obtained.

② Prestressed modal modeling of the shock absorber spring:

Provide prestress for the modal model, and obtain the first six modal frequencies and mode shapes of the shock absorber spring through prestress modal modeling;

③Random vibration modeling of the shock absorber spring:

Apply the power spectral density map for the first six modal frequencies and mode shapes of the shock absorber spring, and set the output to obtain the equivalent stress cloud map of the shock absorber spring under prestress 1σ, 2σ and 3σ and the Stress values S _1σ , S _2σ and S _3σ ;

Step 3: Use the random fatigue three-interval method to calculate the maximum number of uses of the shock absorber spring.

Preferably, the method for calculating the maximum number of times of use of the shock absorber spring using the random fatigue three-interval method is as follows:

The shock absorber spring stress distribution range of -1σ～1σ vibration time accounts for 68.3% of the total time, the vibration time distribution range of -2σ～2σ accounts for 27.1% of the total time, and the vibration time distribution range of -3σ～3σ accounts for 68.3% of the total time. 4.33% of the total time,

Then the fatigue time of the shock absorber spring is:

N ₂ is the fatigue time of the shock absorber spring, N _1σ , N _2σ and N _3σ are the fatigue cycle numbers corresponding to the three stress level intervals of the spring, combined with the S _1σ , S _2σ and S _3σ obtained in step 2, Further, specific numerical values of N _1σ , N _2σ and N _3σ are obtained.

Preferably, the steps of obtaining the force-displacement curve of the shock absorber spring are as follows: controlling the movement of the wear tester, preloading it, bringing the indenter of the wear tester into contact with the spring, and then setting the Z axis of the indenter Slowly move down for a certain distance, use the displacement sensor and force sensor set on the indenter of the wear tester to simultaneously collect the displacement and the force in each direction of the indenter, and fit the output-displacement curve.

Preferably, the shock absorber use times threshold setting module compares the measured maximum use times of the shock absorber damping plate with the maximum use times of the shock absorber spring, selects a value with a smaller maximum use number as a reference, and uses the shock absorber The threshold for the maximum number of uses of the device is determined to be slightly smaller than this value.

Preferably, a method of detecting a main failure mechanism of a dry friction damping shock absorber, comprising the steps of:

S1. Calculate the tangential relative slip distance between the shock absorber damping plate and the shock absorber shell: the shock absorber damping plate and the inner wall of the shock absorber shell form a pair of friction pairs, and use the Archard adhesive wear model to obtain the shock absorber The tangential relative slip distance between the damping plate and the shock absorber shell, the calculation formula is as follows:

In the formula, L is the tangential relative sliding distance between the damping plate of the shock absorber and the shock absorber shell, h is the wear depth index of the damping plate of the shock absorber, A _a is the distance between the damping plate of the shock absorber and the shell of the shock absorber Contact area, H is the HRC hardness of the inner wall of the shock absorber shell, K is the wear factor, and P is the normal pressure between the damping plate of the shock absorber and the inner wall of the shock absorber;

S2. Calculate the single slip distance of the damping plate of the shock absorber: the slip distance of the damping plate of the shock absorber is l, the measured maximum compression amount of the spring is C _max , and the minimum compression amount is C _min , then the single slip of the damping plate The shift distance is as follows:

l=2( _Cmax - _Cmin );

S3. Calculate the maximum number of times of use of the damping plate of the shock absorber:

Divide the tangential relative slip distance between the shock absorber damping plate and the shock absorber shell calculated by S1 and the single slip distance of the shock absorber damping plate calculated by S2 to obtain the maximum number of uses of the shock absorber damping plate , the calculation formula is as follows:

In the formula, N ₁ is the maximum number of times of use of the damping plate of the shock absorber;

S4. Determine the static load of the shock absorber spring: the static load of the shock absorber spring includes the prestress and load pressure of the shock absorber installation, where the calculation method of the load pressure is as follows:

F ₁ ＝m×g÷n, where F ₁ is the load pressure, m is the load mass, and n is the number of shock absorber springs;

The calculation method for the prestress of the shock absorber installation is as follows:

First measure the compression length of the shock absorber spring in the assembly, and then use the wear tester to obtain the force-displacement curve of the shock absorber spring. According to the force-displacement curve of the shock absorber spring, the shock absorber spring is subjected to compression Pressure, denoted as F ₂ ,

The calculation method of the static load of the shock absorber spring is as follows:

F _s =F ₁ +F ₂ ;

S5. Perform finite element modeling on the shock absorber spring: the specific steps are as follows:

①Static modeling of dry friction damping shock absorber:

The dry friction damping shock absorber is modeled statically, and the structural relationship diagram of the friction dry friction damping shock absorber is obtained, and the modal model with static load and boundary conditions as prestress is obtained.

② Prestressed modal modeling of the shock absorber spring:

Provide prestress for the modal model, and obtain the first six modal frequencies and mode shapes of the shock absorber spring through prestress modal modeling;

③Random vibration modeling of the shock absorber spring:

Apply the power spectral density map for the first six modal frequencies and mode shapes of the shock absorber spring, and set the output to obtain the equivalent stress cloud map of the shock absorber spring under prestress 1σ, 2σ and 3σ and the stress value;

S6, using the random fatigue three-interval method to calculate the maximum number of uses of the shock absorber spring;

S7. Compare the wear life of the shock absorber damping plate obtained from S1-S3 with the fatigue life of the spring obtained from S5-S6; adopt the principle of mechanism competition, and use the fatigue life of the shock absorber spring with a shorter life as the shock absorber Primary failure mechanism.

The present invention has the following advantages:

1) Determine the service life of the dry friction damping shock absorber by calculating and comparing the times of the damping spring and the damping plate in the dry friction damping shock absorber, and according to the calculated service life of the damping plate and spring, according to the smaller The number of times of use of the shock absorber is used to set the threshold of the number of times of use of the shock absorber. Compared with the actual number of times of use of the spring and the damper, the work of the shock absorber of the aviation equipment is monitored to ensure the normal operation of the shock absorber of the aviation equipment. Security Monitoring.

2) The present invention compares the shock absorber use times threshold with the actual measured shock absorber use times threshold according to the set threshold, if the shock absorber actual use times reaches the threshold, the control module controls the alarm module to give an alarm, and determines whether the shock absorber is activated. Replacement to ensure the safety of aviation equipment.

3) The wear life test of the damping plate and spring of the shock absorber is carried out to obtain the main failure mechanism and provide a basis for the accelerated test.

Description of drawings

Fig. 1 is the structural representation of main failure monitoring system of the present invention;

Fig. 2 is a schematic flow chart of the method of the present invention;

Figure 3 is a diagram of the hardness measurement results of the inner wall of the shock absorber;

Fig. 4 is positive pressure test result graph;

Fig. 5 is a spring force-displacement curve;

Figure 6a is a schematic cross-sectional view of the shell after cutting;

Fig. 6b is a schematic cross-sectional view of the housing in another embodiment after cutting;

Figure 7 is a diagram of the pressure exerted on the spring

Fig. 8 is a random vibration power spectral density diagram.

detailed description

Below in conjunction with accompanying drawing, structure of the present invention is further explained:

The present invention provides a dry friction damping shock absorber main fault monitoring system, which includes a shock absorber and a main fault monitoring system, which includes a dry friction damping shock absorber 1 and a main fault monitoring system 2, as shown in Figure 6a, dry The frictional damping shock absorber comprises a housing 10, a base 11, a shaft 12, a spring 13, a gasket 14 and a damping sheet 15, the housing 10 is arranged on the base 11, and the shaft 12, the spring 13, the gasket 14 and the damping sheet 15 are arranged Inside the housing 10 , the damping sheet 15 is disposed in the middle of the housing 10 . The damping plate 15 divides the spring 13 into upper and lower parts, and the washer 14 is arranged on the upper part of the housing 10 . Figure 6b shows a schematic structural view of another embodiment of the shock absorber, which includes 10, a base 11, a shaft 12, a spring 13, a gasket 14 and a damping plate 15, the spring 13 is arranged inside the housing, and the damping plate is arranged on Near the inner wall of the housing 10.

The main fault monitoring system 2 includes a detection module 21 , a control module 22 , an alarm module 23 and a real-time monitoring module 24 for detecting a dry friction damping shock absorber. The detection module 21 is equipped with a sensor to monitor the actual use times of the shock absorber, and the control module 22 compares the actual use times of the damping plate and the spring with the previously set threshold of the maximum use times of the shock absorber to determine whether the threshold is reached. If the threshold is reached, the alarm module 23 issues an alarm.

The detection module 21 includes a shock absorber usage times measurement unit 211 and a detection result output module 213, the shock absorber usage times measurement unit 211 detects the actual usage times of the shock absorber and the detection result output module 213 according to the shock absorber usage times measurement unit The detection result at 211 sends the actual usage times of the shock absorber to the control module 22 .

The control module 22 includes a micro-controller 221 and a shock absorber use times threshold setting module 222, the shock absorber use times threshold setting module 222 measures the shock absorber maximum use times threshold, and sends the threshold to the microcontroller 221, Microcontroller 221 stores the threshold value of the maximum number of times of use of the shock absorber, and compares the actual number of times of use of the damper plate and the spring with the threshold value of the maximum number of times of use of the shock absorber. When the actual number of times of use of the damper plate or the actual number of times of use of the spring reaches When the shock absorber reaches the threshold of the maximum number of times of use, the control module 22 sends an alarm signal to the alarm module 23, and the alarm module 23 issues an alarm.

The real-time monitoring module 24 detects the shock absorber according to the alarm signal of the alarm module, judges the fault of the shock absorber, and sends a signal to replace the shock absorber. The staff replace the shock absorber, damping plate or spring according to the failure of the shock absorber.

Preferably, a method for monitoring main faults of shock absorbers according to the above system, as shown in Figure 2, includes the following steps:

S1. The shock absorber use times threshold setting module 222 measures the service life of the shock absorber to obtain the shock absorber maximum use number threshold, which specifically includes the following steps:

① The measuring unit for the number of times of use of the damping sheet detects the maximum number of times of use of the damping sheet;

② The measuring unit of the number of times of spring use detects the maximum number of times of use of the spring;

③ Shock absorber usage times threshold setting module 222 compares the measured maximum usage times of the damping plate with the maximum usage times of the spring, and determines the maximum usage times threshold of the shock absorber;

S2. The detection module 21 monitors the actual number of times of use of the shock absorber in real time, and uploads the actual number of times of use of the shock absorber to the control module;

S3. The microcontroller 221 compares the actual number of times of use of the shock absorber with the threshold of the maximum number of times of use of the shock absorber. When the actual number of times of use of the shock absorber reaches the threshold of the maximum number of times of use of the shock absorber, the control module 22 reports to the alarm module 23 Send an alarm signal, and the alarm module 23 issues an alarm;

S4. The real-time monitoring module 24 detects the shock absorber according to the alarm signal of the alarm module 23, judges the failure of the shock absorber, and sends a signal to replace the shock absorber.

The calculation method of the wear life of the damping plate in the dry friction damping shock absorber, that is, the maximum number of times of use of the damping plate, the specific steps are as follows:

Step 1: Calculation of the tangential relative slip distance L between the damping plate and the shock absorber housing 1 . The damping plate and the inner wall of the shell of the dry friction damping shock absorber constitute a pair of friction pairs. Using the Archard adhesive wear model, the calculation formula of the tangential relative slip distance between the damping plate and the shock absorber shell is obtained. The basic forms of wear can be divided into: adhesive wear, abrasive wear, fatigue wear, corrosion wear, scratches, fretting wear, etc. Adhesive wear is the phenomenon that when the surface of the friction pair slides relative to each other, the adhesive nodes formed due to the adhesive effect shear and break, and the sheared material falls off into wear debris, or migrates from one surface to another, which is called adhesive wear. .

The wear form between the shock absorber shell (steel) and the damping sheet (PTFE) involved in this patent is mainly adhesive wear. Therefore, it is most accurate to use the Archard adhesive wear model to measure the tangential relative slip distance between the damping plate and the shock absorber housing.

The calculation formula is as follows:

In the formula, L is the tangential relative sliding distance between the damping plate and the shock absorber shell, h is the wear depth index of the damping plate, A _a is the contact area between the damping plate and the shock absorber shell, and H is the shock absorber shell HRC hardness of the inner wall, K is the wear factor, and P is the normal pressure of the damping sheet and the inner wall of the shock absorber.

The determination process of each parameter in the formula is as follows:

a. Define the wear depth index h of the damping sheet, and define h=3mm in this embodiment.

b. Calculate the contact area A _a between the damping plate and the shock absorber shell, as shown in the following formula

A _a = πd·t

In the formula, d is the inner diameter of the shock absorber shell, and t is the thickness of the damping plate.

In this embodiment, the calculation result of the contact area between the damping plate and the shock absorber housing is

A _a ＝π5·35≈550mm ²

C. Measure the HRC hardness H of the inner wall of the shock absorber housing.

Since the inner wall of the shock absorber is a closed structure, it is impossible to directly measure the HRC surface hardness of the inner wall, so it is cut. The shock absorber shell is fixed by bolts and slots, and then the shell is cut by rotating the ring cutter, and then a certain part of the shell is selected for hardness measurement test.

Replace the corresponding module on the UMT friction and wear tester and select a suitable indenter to measure the hardness. Figure 3 is the measurement results.

In this embodiment, the HRC surface hardness of the inner wall of the shock absorber was measured to be 30, that is, H=30GPa

d. Measure the normal pressure between the damping sheet and the inner wall of the shock absorber. Fix a part of the cut shock absorber shell on the UMT test bench, and then press the damping sheet to fit the inner wall of the shell.

To set the loading steps, first manually operate the indenter in contact with the sample, then set the expected displacement to 3mm and the falling time to 5min, so that the indenter drops very slowly to simulate the effect of static load. The result is shown in Figure 6:

The results show that the positive pressure value remains basically unchanged at 7.33N between the displacement of 1.85mm and 2.67mm, and then the pressure increases rapidly in the smaller displacement range. This shows that the damping sheet is in full contact with the inner wall of the shock absorber at a displacement of 2.7mm, which means that the positive pressure between the damping sheet and the inner wall of the housing is 7.33N during operation, that is, P=7.33N.

e. Calculate wear coefficient K

The calculation formula of wear coefficient K is shown in the following formula:

lgK＝5lgμ-2.27

where μ is the coefficient of friction between the damping plate and the inner wall of the shock absorber shell. The material of the damping plate is polytetrafluoroethylene, the material of the shock absorber shell is steel, and the friction coefficient between them is μ=0.05. Then K=1.68×10 ^-9

The calculation result of the tangential relative slip distance between the damping plate and the shock absorber shell is:

Step 2: Calculate the slip distance of the damping plate in a single cycle.

The sliding distance of the damping plate is related to the compression amount of the spring in the shock absorber. Assuming the sliding distance of the damping plate is l, the maximum compression amount of the spring is C _max , and the minimum compression amount is C _min . Then the single slip distance is as follows:

l=2(C _max -C _min )

In this embodiment, by measuring the traces of contact between the inner wall of the shock absorber housing and the damping plate, the calculation result of the slip distance of the damping plate in a single cycle is l=2×(7-1.5)=11mm

Step 3: Calculate the maximum use times of the damping plate in the dry friction damping shock absorber,

Combining the tangential relative slip distance L between the damping plate and the shock absorber shell calculated in step 1 and the slip distance l of the damping plate in a single cycle calculated in step 2, the calculation formula for the wear life of the damping plate is as follows The formula shows:

In the formula, N1 is the number _of times the damping plate is used in the dry friction damping shock absorber. Calculated as

The wear tester adopts UMT friction and wear tester to test the bonding strength, surface roughness, fracture toughness, creep, lubrication/wear resistance, impact resistance, and wear resistance of various films/coatings by pressing/scratching/grinding. Scratch ability, corrosion resistance, failure and fatigue, etc. It can evaluate the lubrication and stick-slip characteristics of solid or liquid lubricating oil; it can evaluate the electrical contact of various materials. At the same time, it can also provide various ideal detection modes, such as simulation tests of various actual working conditions in classical tribology: for disk, ball-to-disk, four-ball, ring-to-block, disk-to-disk, etc.

The method of measuring the maximum number of uses of the spring is as follows:

Step 1: Determine Spring Static Load

The spring of the dry friction damping shock absorber bears the action of two parts of static load, one part is the prestress installed with the shock absorber, and the other part is the pressure from the load. It is known that the mass of the load is m=5kg, and there are n=4 shock absorbers in total, and they are regularly distributed around the load, then the pressure F ₁ of the load on the shock absorber is: (g is the acceleration of gravity)

F ₁ =m×g÷n=5×9.8÷4=12.25N

In order to calculate the prestress installed with the shock absorber, firstly measure the compressed length of the spring l ₀ =1.7mm in the assembly, and then use the UMT friction and wear tester to measure the force-displacement curve of the spring.

The movement of the tester is controlled by the controller, and it is preloaded so that the pressure head of the tester touches the spring, and then the Z-axis of the pressure head is set to slowly move downward by 7 mm, and the loading time is 20 minutes. The displacement sensor and force sensor of the indenter of the tester can simultaneously collect the displacement and the force of the indenter in all directions. Using its supporting UMT software, the output force-displacement curve can be automatically fitted through the collected data, as shown in Figure 5.

According to the curve in Fig. 5, when the spring is compressed by 1.7mm, the pressure it receives is F ₂ =11N.

Combining the two parts of pressure, the static load on the spring is obtained as F _s =F ₁ +F ₂ =12.25+11=23.25N.

Step 2: Finite element modeling of the spring

a. Static modeling

First, use Solidworks to model the dry friction damping shock absorber, including the shell, base, shaft, spring, gasket and damping plate, and obtain the assembly drawing of the dry friction damping shock absorber by setting the matching relationship between the parts .

Save the established 3D model in STEP format, and import it into ANSYS, set material properties, such as its elastic modulus and density, and select intelligent mesh division during free mesh division. Then define the boundary constraint condition for the dry friction shock absorber as the lower surface of the spring is fixed, and the pressure is 23.25N, as shown in Figure 7.

b. Prestressed modal modeling of the spring

The prestress is provided by the static load and boundary conditions in the static modeling, and the first six frequencies of the spring are obtained through the prestress mode. The first six frequencies of the spring are shown in Table 1.

Table 1 The modal frequencies of each order of the spring

modal Frequency (Hz) level one 248.16 second order 302.35 third order 321.47 fourth order 362.92 fifth order 545.15 Sixth order 569.50

c. Random vibration modeling of springs

As shown in Figure 8, apply the power spectral density map, and then set the output to obtain the equivalent stress cloud map and VonMises stress value of the spring under _1σ , _2σ , and _3σ respectively. MPa.

Step 3: Use the random fatigue three-interval method to calculate the maximum number of times the spring can be used

The stochastic fatigue three-interval method widely used in engineering is based on the Mises stress response of the structure proposed by Steinberg to obey the Gaussian distribution. The vibration time of the task in the stress distribution interval of -1σ～1σ, -2σ～2σ, and -3σ～3σ accounted for 68.3%, 27.1%, and 4.33% of the total time, respectively, and the stress occurrence time outside the 3σ interval only accounted for 0.27%. The damage it causes is negligible. Then the fatigue time of the spring is:

N _1σ , N _2σ , and N _3σ are the fatigue cycle numbers corresponding to the three stress level intervals of the material, and the relationship between the SN of the spring material 304 stainless steel is obtained by consulting the literature:

lgN=84.84-9.563lgS

Combining S _1σ , S _2σ and S _3σ obtained in Step 2, and then obtain N _1σ = 823468, N _2σ = 24915, N _3σ = 517, then

Determine the maximum number of uses threshold for dry friction damping shock absorbers:

In this embodiment, compare the wear life N ₁ ≈ 3.65×10 ¹⁴ of the damping plate obtained in steps 1, 2 and 3 with the fatigue life N ₂ ≈ 10476 of the spring obtained in steps 4, 5 and 6, obviously N ₂ < N ₁ ; Based on the principle of competition, the maximum number of times of use N ₂ with a shorter life—the maximum number of times of use of the spring is determined as the maximum number of times of use of the shock absorber, that is, the threshold of the maximum number of times of use of the shock absorber.

Finally, it should be noted that: the above-described embodiments are only used to illustrate the technical solutions of the present invention, rather than limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand : It is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the various embodiments of the present invention range.

Claims (8)

1. A kind of 1. dry friction damping shock absorber major error monitoring method, it is characterised in that：

   A kind of major error prison of the major error monitoring method of described dry friction damping shock absorber based on dry friction damping shock absorber Examining system, the major error monitoring system include being used for detection module, the control that fault detect is carried out to dry friction damping shock absorber Molding block, alarm module and real-time monitoring modular；

   Detection module：Including damper access times measuring unit and testing result output module, damper access times are surveyed Measure actual use number of the unit to damper to detect, testing result output module measures single according to damper access times The testing result of member sends the actual use number of damper to control module；

   Control module includes microcontroller and damper access times threshold setting module, the setting of damper access times threshold value Module measurement obtains damper maximum access times threshold value, and threshold value is sent to microcontroller, microcontroller to damper most Stored using frequency threshold value greatly, and the actual use number of damper and damper maximum access times threshold value are compared Compared with when the actual use number of damper reaches damper maximum access times threshold value, control module is sent to alarm module Alarm signal, alarm module send alarm；

   Real-time monitoring modular detects to damper according to the alarm signal of alarm module, judges its failure, and send replacing The signal of damper；

   The damping fin that damper access times threshold setting module includes being used to measure damper damping fin maximum access times makes With number measuring unit and the spring access times measuring unit for measuring absorber spring maximum access times；

   The major error monitoring method of described dry friction damping shock absorber comprises the following steps：

   S1, damper access times threshold setting module measure to the service life of damper obtains the maximum use of damper Frequency threshold value, specifically comprise the following steps：

   1. damping fin access times measuring unit detects damper damping fin maximum access times；

   2. spring access times measuring unit detects absorber spring maximum access times；

   3. damper damping fin maximum access times and damper that damper access times threshold setting module obtains to measurement Spring maximum access times are compared, and determine damper maximum access times threshold value；

   S2, detection module monitor the actual use number of damper in real time, and the actual use number of damper is uploaded into control Molding block；

   The actual use number of damper compared with damper maximum access times threshold value, is worked as damping by S3, microcontroller When the actual use number of device reaches damper maximum access times threshold value, control module sends alarm signal to alarm module, Alarm module sends alarm；

   S4, real-time monitoring modular are detected to damper, judge the failure of damper according to the alarm signal of alarm module, And send the signal for changing damper.
2. 2. dry friction damping shock absorber major error monitoring method according to claim 1, it is characterised in that：Damping fin uses The method of number measuring unit detection damper damping fin maximum access times comprises the following steps：

   Step 1：Calculate circumferentially opposite skidding distance between damper damping fin and damper housing：Damper damping fin is with subtracting Shake device inner walls and form friction pair, using Archard adhesive wear models, obtain damper damping fin and damper shell Circumferentially opposite skidding distance, calculation formula are as follows between body：

   <mrow> <mi>L</mi> <mo>=</mo> <mfrac> <mrow> <msub> <mi>hA</mi> <mi>a</mi> </msub> <mi>H</mi> </mrow> <mrow> <mi>K</mi> <mi>P</mi> </mrow> </mfrac> </mrow>

   L circumferentially opposite skidding distances between damper damping fin and damper housing in formula, h are damping fin wearing depth index, A_a For the contact area between damper damping fin and damper housing, H is the HRC hardness of damper inner walls, K for abrasion because Son, P are the normal pressure of damper damping fin and damper inwall；

   Step 2：Calculate damper damping fin single skidding distance：Damper damping fin single skidding distance is l, and measurement obtains The maximum compressibility of absorber spring is C_max, minimal compression amount is C_min, then the following institute of damper damping fin single skidding distance Show：

   L=2 (C_max-C_min)；

   Step 3：Calculate friction damper damping fin maximum access times：

   Circumferentially opposite skidding distance and step 2 calculate between damper damping fin and damper housing that step 1 is calculated Obtained damper damping fin single skidding distance is divided by, and it is maximum using secondary to obtain damper damping fin

   N in formula₁For damper damping fin maximum access times.
3. 3. dry friction damping shock absorber major error monitoring method according to claim 2, it is characterised in that：It is each in step 1 The determination process of parameter is as follows：

   1. it is h to define damper damping fin wearing depth index；

   2. calculate the contact area between damper damping fin and damper housing, A_a=π dt

   A in formula_aFor the contact area between damper damping fin and damper housing, d is damper housing interior diameter, and t is damping fin Thickness；

   3. measure the HRC hardness of damper inner walls：Damper housing is fixed, then rotated using annular cutter to damping Device housing carries out cutting sampling, and the HRC hardness of damper inner walls is measured using fretting wear instrument；

   4. measure damper damping fin and the normal pressure of damper inner walls：Damper shell specimens are fixed on friction mill Damage on instrument, and damper damping fin is depressed into and is bonded with damper inner walls, pressure head and damper housing to be measured are connect Touch, expected displacement and its fall time are set, pressure head is very slowly declined, simulate dead weight effect, from multiple Test result determines normal pressure when damper damping fin completely attaches to damper inner walls between the two；

   5. calculating coefficient of waste K, coefficient of waste K calculation formula is as follows：

   LgK=5lg μ -2.27

   μ is damper damping fin and the coefficient of friction of damper inner walls in formula.
4. 4. dry friction damping shock absorber major error monitoring method according to claim 1, it is characterised in that：Spring uses secondary The method of number measuring unit detection absorber spring maximum access times comprises the following steps：

   Step 1：Determine absorber spring dead load：Absorber spring dead load includes prestressing force and the load of damper installation Pressure, wherein：The computational methods of load pressure are as follows：

   F₁=m × g ÷ n, wherein F₁For load pressure, m is load quality, and n is absorber spring quantity；

   The prestressed computational methods of damper installation are as follows：

   Reduction length of the absorber spring in assembling is measured first, recycles abrasion meter to obtain power-displacement song of spring Line, according to the force-displacement curve of spring, the pressure that spring is subject in compression is obtained, is designated as F₂,

   The computational methods of spring dead load are as follows：

   F_s=F₁+F₂；

   Step 2：Finite element modeling is carried out to absorber spring：Comprise the following steps that described：

   1. statics modeling is carried out to dry friction damping shock absorber：

   Statics modeling is carried out to dry friction damping shock absorber, obtains the structural relation figure of dry friction damping shock absorber, and obtain Using dead load and boundary condition as prestressed modal model；

   2. pre-stressed mode modeling is carried out to absorber spring：

   Prestressing force is provided for modal model, is modeled by pre-stressed mode, the first six rank modal frequency of absorber spring is obtained and shakes Type；

   3. random vibration modeling is carried out to absorber spring：

   Apply power spectral density plot for the first six rank modal frequency of absorber spring and the vibration shape, set output to respectively obtain damper bullet Stress value S under equivalent stress cloud atlas and 1 σ of the spring under the σ of prestressing force 1,2 σ and 3 σ, 2 σ and 3 σ_1σ、S_2σAnd S_3σ；

   Step 3：Absorber spring maximum access times are calculated using the interval method of random fatigue three.
5. 5. dry friction damping shock absorber major error monitoring method according to claim 4, it is characterised in that：Using random tired The method that the interval method of labor three calculates absorber spring maximum access times is as described below：

   Absorber spring stress distribution section is that the σ of -1 σ~1 time of vibration accounts for the 68.3% of total time, distributed area be -2 σ~ 2 σ time of vibration accounts for the 27.1% of total time, and distributed area is that the σ of -3 σ~3 time of vibration accounts for the 4.33% of total time,

   Then the tired time of absorber spring is：

   <mrow> <msub> <mi>N</mi> <mn>2</mn> </msub> <mo>=</mo> <mn>1</mn> <mo>/</mo> <mrow> <mo>(</mo> <mfrac> <mn>0.683</mn> <msub> <mi>N</mi> <mrow> <mn>1</mn> <mi>&amp;sigma;</mi> </mrow> </msub> </mfrac> <mo>+</mo> <mfrac> <mn>0.271</mn> <msub> <mi>N</mi> <mrow> <mn>2</mn> <mi>&amp;sigma;</mi> </mrow> </msub> </mfrac> <mo>+</mo> <mfrac> <mn>0.0433</mn> <msub> <mi>N</mi> <mrow> <mn>3</mn> <mi>&amp;sigma;</mi> </mrow> </msub> </mfrac> <mo>)</mo> </mrow> </mrow>

   N₂For the tired time of absorber spring, N_1σ、N_2σAnd N_3σIt is that spring is corresponding on three stress level sections respectively Fatigue life cycle, the S tried to achieve with reference to step 2_1σ、S_2σAnd S_3σ, and then obtain N_1σ、N_2σAnd N_3σConcrete numerical value.
6. 6. dry friction damping shock absorber major error monitoring method according to claim 5, it is characterised in that：Obtain damper The step of force-displacement curve of spring, is as described below：The motion of abrasion meter is controlled, it is preloaded, surveys abrasion The pressure head of examination instrument touches spring, then sets the Z axis of pressure head to slowly move downward certain distance, utilizes abrasion meter pressure head The displacement transducer of setting and the displacement of force snesor synchronous acquisition and pressure head all directions stress, and fit force-displacement curve.
7. 7. dry friction damping shock absorber major error monitoring method according to claim 6, it is characterised in that：Damper uses Frequency threshold value setting module is to the damper damping fin maximum access times that measurement obtains and absorber spring maximum access times It is compared, selects the less numerical value of maximum access times as reference, damper maximum access times threshold value is defined as omiting Less than the numerical value.
8. 8. a kind of method that main failure mechanism to dry friction damping shock absorber is detected, it is characterised in that：It includes following Step：

   S1, calculate circumferentially opposite skidding distance between damper damping fin and damper housing：Damper damping fin and damper shell Internal wall forms friction pair, using Archard adhesive wear models, obtains cutting between damper damping fin and damper housing It is as follows to Relative sliding distance, calculation formula：

   <mrow> <mi>L</mi> <mo>=</mo> <mfrac> <mrow> <msub> <mi>hA</mi> <mi>a</mi> </msub> <mi>H</mi> </mrow> <mrow> <mi>K</mi> <mi>P</mi> </mrow> </mfrac> </mrow>

   L circumferentially opposite skidding distances between damper damping fin and damper housing in formula, h are damper damping fin wearing depth Index, A_aFor the contact area between damper damping fin and damper housing, H is the HRC hardness of damper inner walls, and K is Wear factor, P are the normal pressure of damper damping fin and damper inwall；

   S2, calculate damper damping fin single skidding distance：The skidding distance of damper damping fin is l, and measurement obtains spring Maximum compressibility is C_max, minimal compression amount is C_min, then damping fin single skidding distance is as follows：

   L=2 (C_max-C_min)；

   S3, calculate damper damping fin maximum access times：

   Subtract what circumferentially opposite skidding distance and S2 between damper damping fin and damper housing that S1 is calculated were calculated Shake device damping fin single skidding distance is divided by, and obtains damper damping fin maximum access times, calculation formula is as follows：

   <mrow> <msub> <mi>N</mi> <mn>1</mn> </msub> <mo>=</mo> <mfrac> <mi>L</mi> <mi>l</mi> </mfrac> <mo>=</mo> <mfrac> <mrow> <msub> <mi>hA</mi> <mi>a</mi> </msub> <mi>H</mi> </mrow> <mrow> <mi>K</mi> <mi>P</mi> <mo>&amp;CenterDot;</mo> <mi>l</mi> </mrow> </mfrac> <mo>=</mo> <mfrac> <mrow> <mi>h</mi> <mo>&amp;CenterDot;</mo> <mi>&amp;pi;</mi> <mi>d</mi> <mi>t</mi> <mo>&amp;CenterDot;</mo> <mi>H</mi> </mrow> <mrow> <mi>K</mi> <mi>P</mi> <mo>&amp;CenterDot;</mo> <mn>2</mn> <mrow> <mo>(</mo> <msub> <mi>C</mi> <mi>max</mi> </msub> <mo>-</mo> <msub> <mi>C</mi> <mi>min</mi> </msub> <mo>)</mo> </mrow> </mrow> </mfrac> </mrow>

   N in formula₁For damper damping fin maximum access times；

   S4, determine absorber spring dead load：Absorber spring dead load includes the prestressing force and load pressure of damper installation, Wherein：The computational methods of load pressure are as follows：

   F₁=m × g ÷ n, wherein F₁For load pressure, m is load quality, and n is absorber spring quantity；

   The prestressed computational methods of damper installation are as follows：

   Measure reduction length of the absorber spring in assembling first, recycle abrasion meter obtain the power of absorber spring- Displacement curve, according to the force-displacement curve of absorber spring, the pressure that absorber spring is subject in compression is obtained, is designated as F₂,

   The computational methods of absorber spring dead load are as follows：

   F_s=F₁+F₂；

   S5, finite element modeling is carried out to absorber spring：Comprise the following steps that described：

   1. statics modeling is carried out to dry friction damping shock absorber：

   Statics modeling is carried out to dry friction damping shock absorber, obtains the structural relation figure of friction dry friction damping shock absorber, and Obtain using dead load and boundary condition as prestressed modal model；

   2. pre-stressed mode modeling is carried out to absorber spring：

   Prestressing force is provided for modal model, is modeled by pre-stressed mode, the first six rank modal frequency of absorber spring is obtained and shakes Type；

   3. random vibration modeling is carried out to absorber spring：

   Apply power spectral density plot for the first six rank modal frequency of absorber spring and the vibration shape, set output to respectively obtain damper bullet Stress value under equivalent stress cloud atlas and 1 σ of the spring under the σ of prestressing force 1,2 σ and 3 σ, 2 σ and 3 σ；

   S6, using the interval method of random fatigue three absorber spring maximum access times are calculated；

   The fatigue life for the spring that S7, the wear-out life for comparing the damper damping fin that S1-S3 is obtained and S5-S6 are obtained；Using The principle of mechanism competition, the main failure mechanism using the fatigue life of life-span shorter absorber spring as damper.