CN108343652B - Method for eliminating hydraulic vibration in brake system test - Google Patents
Method for eliminating hydraulic vibration in brake system test Download PDFInfo
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- CN108343652B CN108343652B CN201711391249.XA CN201711391249A CN108343652B CN 108343652 B CN108343652 B CN 108343652B CN 201711391249 A CN201711391249 A CN 201711391249A CN 108343652 B CN108343652 B CN 108343652B
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B21/00—Common features of fluid actuator systems; Fluid-pressure actuator systems or details thereof, not covered by any other group of this subclass
- F15B21/008—Reduction of noise or vibration
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64F—GROUND OR AIRCRAFT-CARRIER-DECK INSTALLATIONS SPECIALLY ADAPTED FOR USE IN CONNECTION WITH AIRCRAFT; DESIGNING, MANUFACTURING, ASSEMBLING, CLEANING, MAINTAINING OR REPAIRING AIRCRAFT, NOT OTHERWISE PROVIDED FOR; HANDLING, TRANSPORTING, TESTING OR INSPECTING AIRCRAFT COMPONENTS, NOT OTHERWISE PROVIDED FOR
- B64F5/00—Designing, manufacturing, assembling, cleaning, maintaining or repairing aircraft, not otherwise provided for; Handling, transporting, testing or inspecting aircraft components, not otherwise provided for
- B64F5/60—Testing or inspecting aircraft components or systems
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- F16L55/00—Devices or appurtenances for use in, or in connection with, pipes or pipe systems
- F16L55/02—Energy absorbers; Noise absorbers
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- F16L9/00—Rigid pipes
Abstract
The invention belongs to the low-temperature test technology of a civil aircraft brake system, and relates to a method for eliminating hydraulic vibration in a brake system test. The invention relates to a vibration-damping oil conveying pipe, an adjustable framework and a vibration-damping bracket; the vibration-damping oil delivery pipe adopts a coaxial three-layer stainless steel pipe and comprises an outer layer pipe, a middle layer pipe and an inner layer oil delivery pipe, and the rigidity of the vibration-damping oil delivery pipe is adjusted to achieve the purpose of vibration damping; the inner layer pipe and the middle layer pipe are positioned by an adjustable framework, and the middle layer pipe and the outer layer pipe are positioned by an adjustable framework; the vibration-damping oil conveying pipe is laid on the vibration-damping bracket and fixed by the clamp, and the vibration-damping bracket is aligned by the level gauge when a concrete floor is laid and fixed on the concrete floor. The invention eliminates the vibration in the test process of the brake system through the vibration reduction oil pipe and the installation vibration reduction bracket.
Description
Technical Field
The invention belongs to the low-temperature test technology of a civil aircraft brake system, and relates to a method for eliminating hydraulic vibration in a brake system test.
Background
The reliability test standard of the brake system at home and abroad is as follows: the reliability tests in product development, identification and production of the American MIL-STD-781 series standard, the reliability tests in international standard IEC60300-3-5 and the reliability identification and acceptance tests of GJB899 are all carried out under the conditions of temperature, humidity and vibration, and the comprehensive environment tests are equivalent to the comprehensive environment tests under no-load conditions because hydraulic stress and electric stress are absent for a brake system. The low temperature and the main hydraulic stress to which the braking system is subjected in use are:
1) the brake pressure of the flying lead is generally 20 MPa.
2) The landing antiskid braking pressure is generally 10 MPa.
3) Low temperature of the environment: the research requirement is generally-55 ℃, and the oil liquid should reach-55 ℃.
The method does not apply hydraulic stress because the reliability test is carried out at home and abroad according to the existing standard, so that the vibration problem caused by the change of the hydraulic stress in the reliability test process of the brake system is not involved.
To determine the life and reliability of the braking system, operational stresses, including cryogenic hydraulic stresses, must be applied to the braking system. The problem of pipeline vibration caused by pressure change occurs in the test process of applying low-temperature hydraulic stress.
According to the analysis of the 'New edition hydraulic engineering handbook' compiled by Lei Tian Jue of Beijing university of rational engineering, the vibration causes are as follows:
1) when the valve is quickly closed or opened, the original kinetic energy in the pipeline is converted into pressure potential energy, the pressure is quickly increased or reduced in front of the valve, huge vibration is generated and noise is generated, and a pressure reducing spring of a brake valve is broken, a hydraulic pipeline and a hydraulic product are burst to hurt personnel on the test site in serious cases, so that the valve belongs to vibration caused by hydraulic pressure change.
2) During a flying line braking pressure test and a landing anti-skid braking test, pressure overshoot occurs in the process of switching on or switching off a hydraulic valve, the pressure overshoot is a common phenomenon in a braking system test, the rated output pressure of the braking valve is assumed to be 10MPa, the response speed of a pressure reducing spring of the braking valve is slower than the rising speed of hydraulic pressure at the moment of switching on, so that the valve core cannot be pushed to close the valve, the pressure output from the braking valve is greater than 10MPa, and the phenomenon that the output pressure is greater than the rated pressure is called overshoot.
3) When the working frequency of the brake system in the test process is close to the pressure change frequency in the oil pipe, resonance can be caused, and huge noise is sometimes accompanied.
The brake system is one of hydraulic systems, and a series of measures are taken at home and abroad aiming at the vibration problem in the test process of the hydraulic system.
The vibration magnitude in the hydraulic test process is reduced by adopting the following method in foreign countries:
1) the accumulator is arranged in front of the hydraulic vibration part to absorb energy and reduce the vibration impact value.
2) An unloading valve is arranged in front of a position where hydraulic impact is generated, and oil return is communicated for unloading when the pressure rises, so that the hydraulic vibration magnitude is reduced.
3) And the rubber hose is adopted to absorb vibration energy, so that the vibration magnitude is reduced.
Similar to foreign countries, the following methods are adopted in China to reduce the vibration magnitude in the hydraulic system test process:
1) the oil inlet and outlet of the pump are connected by flexible pipes, and the elastic deformation of the flexible pipes is used for absorbing the energy of hydraulic vibration and reducing the vibration magnitude.
2) The rigidity of the hydraulic valve spring is reduced, vibration energy is absorbed by means of deformation of the spring, and the vibration magnitude is reduced.
3) The accumulator is installed in front of the part generating hydraulic vibration to absorb energy and reduce vibration value.
4) The Lei Tian Ju Piao of Beijing university of rational engineering, newly compiled Hydraulic engineering Manual employs a method of reducing the valve opening speed to mitigate the hydraulic vibration.
The above domestic and foreign technologies have the following disadvantages:
1) the pressure accumulator is arranged in front of the part generating the hydraulic vibration to influence the pressure rise time of the brake system.
2) The unloading valve is arranged in front of a part generating hydraulic vibration to reduce the vibration magnitude, but the unloading valve is opened to release pressure when exceeding a certain pressure and is closed when falling below the certain pressure, and vibration exists.
3) The rubber hose is used to influence the response speed of the brake pressure, and the condition that the development requirement cannot be met occurs.
4) The vibration of the hydraulic valve part can be relieved by reducing the rigidity of the spring of the hydraulic valve, but the stroke of the valve core is enlarged.
5) Reducing the valve opening speed can alleviate hydraulic shock, but does not meet the requirement of rapidity of brake pressure rise
Disclosure of Invention
The purpose of the invention is: the method for eliminating the hydraulic vibration in the brake system test is provided, and the vibration in the brake system test process is eliminated through the vibration reduction oil pipe and the installation vibration reduction bracket.
The technical principle of the invention is as follows: when the oil pipe vibrates in the air, the energy absorbed by the air is very little, and the vibration reduction effect cannot be achieved. The damping oil pipe that this application provided comprises three-layer oil pipe, fixes with adjustable skeleton between every two-layer steel pipe, and the rigidity of adjustable skeleton can be tested and confirmed, reaches the purpose of absorption vibration energy through adjusting rigidity. When the vibration damping bracket is implemented, the vibration damping bracket is placed in concrete, and the concrete is fixedly connected with the vibration damping bracket after being solidified. The supporting rigidity and the natural frequency are changed, and part of vibration energy is absorbed by the vibration damping bracket, so that the aim of eliminating the vibration is fulfilled.
The technical scheme of the invention is as follows: a method for eliminating hydraulic vibration in a brake system test relates to a vibration-damping oil conveying pipe, an adjustable framework and a vibration-damping bracket; the vibration-damping oil delivery pipe adopts a coaxial three-layer stainless steel pipe and comprises an outer layer pipe, a middle layer pipe and an inner layer oil delivery pipe, and the rigidity of the vibration-damping oil delivery pipe is adjusted to achieve the purpose of vibration damping; the inner layer pipe and the middle layer pipe are positioned by an adjustable framework, and the middle layer pipe and the outer layer pipe are positioned by an adjustable framework; the vibration-damping oil conveying pipe is laid on the vibration-damping bracket and fixed by the clamp, and the vibration-damping bracket is aligned by the level gauge when a concrete floor is laid and fixed on the concrete floor.
The invention has the beneficial effects that: the invention provides a method for eliminating hydraulic vibration in a brake system test. In the implementation process, the following advantages are specifically provided:
1) by adopting the oil delivery pipe consisting of the three layers of steel pipes, each two layers of oil delivery pipes are fixed by the adjustable framework and finally installed on the vibration reduction bracket, and the vibration in the working process of 10MPa and 20MPa is eliminated when the a size of the adjustable framework is 2.8mm through tests.
2) After the noise is eliminated, the influence on the working environment is avoided, the harm of the noise to workers in the test process is eliminated, and the method has a good human engineering effect. The technology is suitable for the comprehensive stress test of the brake system through testing, and has a good vibration reduction effect.
Drawings
FIG. 1 is an adjustable framework between an outer insulation pipe and an intermediate temperature-regulating pipe.
Fig. 2 is an adjustable framework between a middle temperature adjusting pipe and an inner oil conveying pipe.
FIG. 3 is a damping bracket, in which FIG. 1 is a rubber sheet with a thickness of 70mm Shore A70; 2, supporting of a vibration damping bracket; 3 is a base; and 4 is a guard plate. The damping bracket has the function of adjusting its natural frequency and absorbing a part of the vibration energy.
Fig. 4 shows a clip for fixing an oil delivery pipe to a vibration damping bracket.
Fig. 5 is a flow chart of an implementation of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made with reference to the accompanying drawings.
The embodiment is a vibration reduction method in the civil aircraft brake system test process. The method relates to a vibration-damping oil conveying pipe, an adjustable framework and a vibration-damping bracket. The vibration-damping oil delivery pipe is a coaxial three-layer stainless steel pipe and comprises an outer layer pipe, a middle layer pipe and an inner layer oil delivery pipe, and the rigidity of the vibration-damping oil delivery pipe is adjusted to achieve the purpose of vibration damping. The inner layer pipe and the middle layer pipe are positioned by using an adjustable framework in figure 1, and the middle layer pipe and the outer layer pipe are positioned by using an adjustable framework in figure 2. The vibration-damping oil conveying pipe is laid on the vibration-damping bracket and fixed by the clamp, and the vibration-damping bracket is aligned by the level gauge when a concrete floor is laid and fixed on the concrete floor. Other functions of the outer pipe, the middle pipe and the inner oil conveying pipe are specifically stated in the invention xxx.
Firstly, listing the low-temperature test requirements of the brake system
The low-temperature test requirements of the brake system are as follows:
1) temperature of the test oil: the room temperature is controllable at minus 55 +/-3 ℃.
2) Flying line braking pressure: 20 MPa; landing brake pressure: 10 MPa.
3) Brake pressure response speed: the time for the electromagnetic valve to rise from zero to 20MPa is not more than 0.2s, and the brake pressure overshoot convergence time is not more than 1.5 s; the time for the servo valve to rise from zero to 10MPa is not more than 0.15s, and the overshoot convergence time is not more than 1 s.
Secondly, listing the vibration reduction design requirements of the low-temperature test of the brake system
The brake system is arranged in the comprehensive environment test box, and when the pressure change frequency is close to the natural frequency of the pipeline in the processes of rising and falling in the pressure response speed range of the brake system, the vibration phenomenon occurs. Therefore, the damping design requirements for the low-temperature test of the braking system are as follows:
the natural vibration frequency of the oil pipeline of the low-temperature test equipment is adjusted, so that resonance does not occur in the working process of the 20MPa and 10MPa pressure rise and fall of the brake system.
The vibration-damping oil delivery pipe consists of three layers of steel pipes, namely an inner oil delivery pipe layer, a middle pipe layer and an outer pipe layer,
Firstly, selecting the specifications and materials of an inner oil delivery pipe, a middle layer pipe and an outer layer pipe
The inner diameter of a hydraulic pipeline of the brake system is 12mm, and in order to ensure oil supply, the inner diameter of an inner layer oil pipe is more than or equal to 12 mm.
Manufacturing a coaxial three-layer stainless steel oil delivery pipe, wherein the three-layer steel pipe is made of 0Cr18Ni9, and an outer layer pipe is selected according to GJB2296 stainless steel seamless steel pipe Specification for aviation: the outer diameter × wall thickness was 50mm × 1.25mm, and the inner diameter was 47.5 mm. Selecting a middle layer pipe: the outer diameter × wall thickness was 32mm × 1mm, and the inner diameter was 30 mm. Selecting an inner oil conveying pipe: the outer diameter × wall thickness was 16mm × 1.5mm, and the inner diameter was 13 mm.
So far, the selected 3 steel pipe specifications are:
1) the specification of the inner oil delivery pipe is as follows: the outer diameter × wall thickness was 16mm × 1.5mm, and the inner diameter was 13 mm.
2) The specification of the middle layer pipe is as follows: the outer diameter × wall thickness was 32mm × 1mm, and the inner diameter was 30 mm.
3) The specification of the outer layer pipe is as follows: the outer diameter × wall thickness was 50mm × 1.25mm, and the inner diameter was 47.5 mm.
Secondly, calculating the strength of the inner oil pipeline
The middle layer pipe and the outer layer pipe are not affected by oil pressure, but the inner layer oil conveying pipe bears high pressure, so that the strength calculation is only carried out on the inner layer oil conveying pipe.
According to GTensile strength sigma of JB2296, 0Cr18Ni9 Steel pipeb520MPa or more, and the standard also stipulates that the allowable stress is 40 percent of the tensile strength, namely sigmaAllowable use＝σb×40％＝208MPa。
According to a calculation method provided by 'Material mechanics' book 258 of the first edition 1979 of the Main edition of Liu hong text of Zhejiang university, stress sigma under the working condition of an oil pipeline is calculatedWork by：
In the formula: p: hydraulic pressure; r: the outer radius of the tubing; r: the inner radius of the tubing.
The maximum working pressure is 20MPa, but overshoot generated when the pressure rapidly rises reaches 30MPa, and the overshoot is used as the basis for intensity calculation, and p is 30MPa, R is 0.8cm, and R is 0.65cm, and the following formula (1) is substituted to obtain:
Vibration energy of the vibration-damping oil conveying pipe is absorbed through the design and installation of the adjustable framework, the vibration-damping bracket and the clamp.
In order to improve the vibration reduction effect of the vibration reduction oil conveying pipe, the adjustable frameworks are used for fixing steel pipes of all layers, the purpose of changing the rigidity of the adjustable frameworks is achieved by processing the size a in the figures 1 and 2, the natural frequency of the vibration reduction oil conveying pipe is changed by adopting a method of gradually reducing the rigidity, and meanwhile, the capacity of absorbing vibration energy is improved.
In order to improve the vibration damping effect, 1 vibration damping bracket is paved on the concrete ground every 1500mm, and a vibration damping oil conveying pipe is paved on the vibration damping bracket and then fixed by a clamp.
Firstly, determining the strength of the adjustable framework and the steel pipe and the matching size of the adjustable framework and the steel pipe
1Cr13 stainless steel is selected to manufacture the adjustable skeleton, and in order to improve the vibration damping performance, the strength of the adjustable skeleton is lowIn terms of the strength of the steel pipe, the sigma of the steel pipe is knownbMore than or equal to 520MPa, the sigma of the framework can be adjustedbSelecting 430MPa, adopting a treatment method of heating at 770-780 ℃, and calculating an empirical formula of the heat preservation time length in a salt furnace as follows:
t＝φ×17s/mm×1.5 (2)
in the formula: phi is the diameter of the bar, mm.
17s/mm means that the incubation time is extended by 17s for every 1mm increase in diameter.
1.5 is the coefficient.
The heat preservation duration of the adjustable framework of fig. 1 is calculated according to equation (2):
47.5mm × 17s/mm × 1.5 ═ 1211.25s ═ 20.1875min, 20 min.
FIG. 2 the length of time the adjustable scaffold is held is calculated according to equation (2) as:
30mm × 17s/mm × 1.5 ═ 765s ═ 12.75min, and 13min was taken.
To avoid deformation, machining is performed after heat treatment. The design pattern of the adjustable framework is shown in the attached figures 1 and 2. Fig. 1 is an adjustable framework between an intermediate layer pipe and an outer layer pipe, and fig. 2 is an adjustable framework between an inner layer oil pipeline and an intermediate layer pipe. The mounting dimension of the adjustable framework is determined as follows:
i, determining two matching sizes of the adjustable framework in figure 1
1) The diameter of the steel pipe is actually measured to be
The fitting dimension of the adjustable skeleton in the attached figure 1 is
2) The diameter of the steel pipe is actually measured to be
The fitting dimension of the adjustable skeleton in the attached figure 1 is
II, determining two installation sizes of the adjustable framework in the figure 2
1) The diameter of the steel pipe is actually measured to be
The fitting dimension of the adjustable skeleton of figure 2 is
2) The diameter of the steel pipe is actually measured to be
The fitting dimension of the adjustable skeleton in the attached figure 1 is
Second, designing an adjustable skeleton
I, 1 Adjustable skeleton structure design
1) Firstly, the matching length of the adjustable framework and the steel pipe is determined, the pipe with the diameter of 32mm in the figure 1 and the pipe at the middle layer are in excessive matching, the installation is influenced by large friction force when the size of the matching length is too large, and the matching effect is influenced by small size of the matching length. The actual measurement is carried out according to the matching length equal to the matching diameter of 32mm, if the assembly difficulty is high under the condition that the assembly surface is coated with lubricating oil, the matching length is symmetrically processed by 0.25mm from 32mm each time, namely the front surface and the back surface are respectively processed by 0.25mm, and the installation work on the middle layer pipe is carried out after each processing. The assembly test is performed iteratively, when the fit length is processed to 21mm, the difficulty is avoided in the assembly process, the fit length is not loosened after assembly, and the fit length of the adjustable framework shown in the figure 1 is determined to be 21 mm.
2) Secondly, determining a vibration reduction rigidity structure of the adjustable framework, wherein the rigidity structure has the following purposes: a) the natural frequency of the oil conveying pipe is changed by processing the dimension a and punching 12 phi 4 holes on the thickness a, so that the aim of vibration reduction is achieved; b) the vibration energy of the oil delivery pipe is absorbed to achieve the aim of vibration reduction; c) the rigidity structure is to ensure air circulation, and in order to reduce air resistance, the dimension a is as small as possible under the condition of ensuring the vibration damping effect and the positioning rigidity.
3) The wall thickness of the matched part of the adjustable framework and the middle-layer pipe is determined, the size is too large, the rigidity is large, the rigidity adjusting range of the size a is influenced, and the size is too small, the deformation is easy, and the matching is influenced. A steel bar with the diameter of phi 32 and the length of 500mm, which is made of 1Cr13 material, is used as a tool, the wall thickness dimension of the adjustable framework is determined through testing, and the sigma of the steel bar after heat treatment isbThe initial wall thickness of the matched part of the framework and the intermediate layer pipe is adjusted to be 2mm, the roughness of the matched surface is Ra0.2, if the rigidity meets the requirement, the wall thickness is continuously processed and reduced, and the processing amount of each time is 0.2 mm. The test work is carried out iteratively according to the method. After each iterative assembly, the 100-time magnifier is used for checking whether deformation occurs. When the wall thickness is processed to be 0.2mm, obvious deformation occurs, the safety factors related to the service life, the strength and the rigidity are generally between 1.5 and 2.5, and the deformation size of 2.5 times of the wall thickness is determined, namely the wall thickness is 0.5 mm.
4) And determining the wall thickness of the matched part of the adjustable framework and the outer layer pipe, wherein the wall thickness is the same as the wall thickness of the matched part of the adjustable framework and the temperature adjusting pipe, and the determined wall thickness is 0.5 mm.
5) Determining the roughness of the matching surface of the adjustable framework and the middle-layer pipe and the roughness of the matching surface of the adjustable framework and the outer-layer pipe: according to the existing processing capacity and cost, the roughness of the matching surface of the adjustable framework and the middle layer pipe and the roughness of the matching surface of the adjustable framework and the outer layer pipe are all Ra0.2.
II, 2 design of adjustable skeleton structure
1) The method for determining the matching length of the adjustable framework and the steel pipe in the figure 2 is the same as that in the figure 1, and the size of the matching length of the adjustable framework and the steel pipe in the figure 2 is determined to be 12mm by adopting an iterative test method.
2) Determining a damping rigidity structure of the adjustable skeleton in the figure 2, wherein the rigidity structure has the following purposes: a) the rigidity is adjusted through the processing size a, the natural frequency of the oil delivery pipe is changed, and the purpose of vibration reduction is achieved; b) the vibration energy of the oil delivery pipe is absorbed to achieve the aim of vibration reduction; c) the rigidity structure is to ensure air circulation, and in order to reduce air resistance, the dimension a is as small as possible under the condition of ensuring the vibration damping effect and the positioning rigidity.
3) The method for determining the wall thickness of the matched part of the adjustable framework and the middle layer pipe in the figure 2 is the same as the method in the figure 1, and the wall thickness is determined to be 0.5mm by adopting a method of iterative processing of the wall thickness and assembling and testing with a phi 16 steel bar.
4) The wall thickness of the adjustable framework and the wall thickness of the outer layer pipe in the figure 2 are determined, the same method is used for determining the wall thickness of the matched part of the adjustable framework and the middle layer pipe, and the determined wall thickness is 0.5 mm.
5) Determining the roughness of the matching surface of the adjustable framework and the temperature adjusting pipe and the matching surface of the adjustable framework and the inner oil conveying pipe in the figure 2: according to the existing processing capacity and cost, the roughness of the matching surface of the adjustable framework and the temperature adjusting pipe and the roughness of the matching surface of the adjustable framework and the inner oil conveying pipe are all Ra0.2.
III, determination method of adjustable framework size a
The initial value of the size a in the figures 1 and 2 is 10mm, then the oil pipe is installed between an inner oil pipe and an outer oil pipe for vibration test, a layer of lubricating oil is uniformly coated on a matching surface when an adjustable framework is installed, the value of the symmetrical machining size a is 0.1mm respectively when vibration occurs in the test process, namely, each surface is machined by 0.1mm, and the value of the size a in the figures 1 and 2 is machined symmetrically on two sides simultaneously until the size which does not generate resonance is determined to be the final size of a. The testing pressure is 20MPa and 10 MPa. The test conditions were:
1) temperature of the test oil: the room temperature is minus 55 plus or minus 4 ℃, the viscosity influences the flow speed and thus the resonant frequency due to different oil viscosities under different temperature conditions, and the resonance is not required to occur within the range of the room temperature to minus 55 plus or minus 4 ℃, so the test is carried out under different temperature conditions. Starting from-55 ℃, the step length is 5 ℃, namely the oil temperature of the second test is-45 ℃, the oil temperature of the third test is-40 ℃ until the oil temperature is 25 ℃. And (3) testing whether the dimension a in the images 1 and 2 generates resonance or not at each oil temperature point, and if the dimension a generates resonance, symmetrically processing the value a on two sides, wherein the processing value is 0.1 mm.
2) And (3) switching on the electromagnetic valve to the brake system under the pressure of 20MPa, wherein the switching-on/off frequency of the electromagnetic valve is 10 times/min, continuously working for 3min, and if no resonance occurs within 3min, finishing the test of the temperature point a and testing the value a under the next temperature condition. If resonance occurs, the a-value size is not available, and all the a-value sizes at which resonance occurs are recorded.
3) Then, the pressure of 10MPa is switched on by the servo valve, the working frequency of the servo valve is 10 times/min, the continuous working is carried out for 3min, if no resonance occurs in 3min, the temperature point and the test of a are finished, and the test of the next a value is carried out. If resonance occurs, the a-value size is not available, and all the a-value sizes at which resonance occurs are recorded.
4) All the a-value sizes of 20MPa and 10MPa in which resonance occurs are summarized, and the a-value sizes are all unusable sizes.
Thirdly, designing a vibration damping bracket
The damping bracket is an assembly made of 1Cr13 stainless steel and rubber, and is shown in an assembly drawing in figure 3.
In fig. 3, 1 is rubber adhered with a low-temperature glue with the thickness of 7mm of Shore A70, the rubber is used for reducing the vibration of an oil delivery pipe, and the number of 1 is 2.
In FIG. 3, 2 is a support of a vibration damping bracket, the heat treatment hardness is HB 220-240, and a through groove with the thickness of 5mm is processed on the support to adjust the rigidity, so that the vibration of an oil delivery pipe is reduced.
In fig. 3, 3 is a base installed in concrete to transmit vibration energy to the concrete ground, and the upper surface of the base is at the same level with the concrete ground, and a layer of rubber 1 with a thickness of 7mm shore a70 is filled between the base and the support of the vibration damping bracket to reduce the vibration magnitude. During installation, the level gauge is used for measuring that each vibration reduction bracket is arranged on the same horizontal plane.
In fig. 3, 4 is a 1Cr13 shield adhered by low temperature glue to prevent concrete from entering the threaded hole.
Thirdly, designing a clamp
The clamp material is made of 1Cr13 steel strip with thickness of 1mm and width of 20mm, as shown in figure 4.
The damping effect of damping bracket is better than the air, from damping bracket installation interval 1000mm, adopt the method of reducing the installation interval step by step and test whether take place the vibration, the step length that reduces at every turn is 50mm, when the installation interval is reduced to 550mm from 1000mm step by step, the vibration is eliminated, confirm that every 500mm is on same circular cross section, install the adjustable skeleton 1 of figure 1 between outer layer pipe and intermediate layer pipe, install the adjustable skeleton 1 of figure 2 between intermediate layer pipe and inner layer defeated oil pipe, install each 20 of the adjustable skeleton of figure 1, figure 2 altogether.
Step 5, test procedure for determining dimension a
The brake system is installed in the low-temperature box, and the temperature control of the low-temperature box is the same as the oil temperature, so that the test error caused by air temperature fluctuation is avoided.
After the oil delivery pipe is placed on the damping bracket rubber, the oil delivery pipe is fixed on the damping bracket by using a hoop and 2M 8 multiplied by 1 screws, a torque wrench for screwing the screws is screwed, threads are cleaned by using gasoline, the friction force between the threads is ensured to be stable, and then the oil delivery pipe is screwed by using 20Nm torque. The shore A38 rubber is filled between the hoop and the oil delivery pipe, the thickness of the rubber is 1mm, and the oil delivery pipe is connected with a low-temperature hydraulic pump station and a brake system.
The resonance of system and system installation overall arrangement are relevant, and this application changes the rigidity of adjustable skeleton through the iteration to adopt the damping bracket to adjust the rigidity of oil pipeline, reach the purpose of avoiding resonant frequency.
Testing whether the oil pipeline has resonance under the working conditions of input pressure of 20MPa and 10 MPa.
1) Firstly, testing and determining the a size without resonance under the condition of 20MPa of input pressure
The initial value of the dimension a in the figures 1 and 2 is 10mm, the step length of each processing is 0.2mm, namely the value of the dimension a tested for the second time is 9.8mm, the value of the dimension a tested for the third time is 9.6mm, and the like. The machining is performed simultaneously in the dimension a in fig. 1 and 2. The test is performed until no resonance occurs. The thickness of the a is changed by processing, so that the natural frequency of the oil conveying pipe is adjusted by changing the rigidity of the adjustable framework, and the aim of preventing resonance is fulfilled.
And II, in the test process of I, the pressure of 20MPa is switched on to continuously work for 3min, the working frequency is 10 times/min, and if no resonance occurs within 3min, no processing is carried out. When the resonance is actually measured, the dimension a of fig. 1 and 2 is simultaneously processed to 9.8mm, and the front and back surfaces are respectively processed to 0.1 mm. When the a is 9.8mm, the pressure of 20MPa is switched on to continuously work for 3min, the resonance occurs in the process of working frequency of 10 times/min, and two-side symmetrical processing and testing are carried out. When the test was carried out until a was 3mm, the resonance was weakened. The two-sided symmetrical processing and testing are continued, when a is 2.8mm, the resonance is eliminated,
2) then testing and determining the a size without resonance under the condition of 10MPa of input pressure
The initial value of the dimension a in the figures 1 and 2 is 10mm, the step size of each processing is 0.2mm, and the smaller the step size is, the more accurate the step size is, namely the value of the dimension a in the second test is 9.8mm, the value of the dimension a in the third test is 9.6mm, and the like. The machining is performed simultaneously in the dimension a in fig. 1 and 2. The test is performed until no resonance occurs. The thickness of the a is changed by processing, so that the natural frequency of the oil conveying pipe is adjusted by changing the rigidity of the adjustable framework, and the aim of preventing resonance is fulfilled.
II, switching on 10MPa pressure to continuously work for 3min, wherein the working frequency is 10 times/min, and if no resonance occurs within 3min, no processing is carried out. When the resonance is actually measured, the dimension a of fig. 1 and 2 is simultaneously processed to 9.8mm, and the front and back surfaces are respectively processed to 0.1 mm. When the a is 9.8mm, the pressure of 10MPa is switched on to continuously work for 3min, the resonance occurs in the process of working frequency of 10 times/min, and two-side symmetrical processing and testing are carried out. When the test was run to a of 5.8mm, the resonance decreased. The two-sided symmetrical processing and testing are continued, when a is 5mm, the vibration is eliminated,
in the process of testing the a size at 10MPa and 20MPa, the minimum value of the a size is 2.8mm, and the a size is determined to be 2.7 +/-0.1 mm.
Thus, a test procedure for eliminating vibration of the hydraulic line is determined.
Claims (1)
1. A method for eliminating hydraulic vibration in a braking system test is characterized in that: the method relates to a vibration-damping oil conveying pipe, an adjustable framework and a vibration-damping bracket; the vibration-damping oil delivery pipe adopts a coaxial three-layer stainless steel pipe and comprises an outer layer pipe, a middle layer pipe and an inner layer oil delivery pipe, and the rigidity of the vibration-damping oil delivery pipe is adjusted to achieve the purpose of vibration damping; the inner layer pipe and the middle layer pipe are positioned by an adjustable framework, and the middle layer pipe and the outer layer pipe are positioned by an adjustable framework; laying the vibration reduction oil delivery pipe on a vibration reduction bracket, fixing the vibration reduction oil delivery pipe by using a hoop, aligning the vibration reduction bracket by using a level gauge when a concrete floor is laid, and fixing the vibration reduction bracket on the concrete floor, wherein the concrete steps are as follows:
step one, listing vibration reduction requirements in a low-temperature test process of a brake system:
1.1) Low temperature test requirements for brake systems
The low-temperature test requirements of the brake system are as follows:
a) temperature of the test oil: the room temperature is controllable at minus 55 +/-3 ℃;
b) flying line braking pressure: 20 MPa; landing brake pressure: 10 MPa;
c) brake pressure response speed: the time for the electromagnetic valve to rise from zero to 20MPa is not more than 0.2s, and the brake pressure overshoot convergence time is not more than 1.5 s; the time for the servo valve to rise from zero to 10MPa is not more than 0.15s, and the overshoot convergence time is not more than 1 s;
1.2) listing the damping design requirements of low-temperature test of a braking system
The brake system is arranged in the comprehensive environment test box, and when the pressure change frequency is close to the natural frequency of the pipeline in the processes of rising and falling in the pressure response speed range of the brake system, the vibration phenomenon occurs; therefore, the damping design requirements for the low-temperature test of the braking system are as follows:
the natural vibration frequency of an oil pipeline of low-temperature test equipment is adjusted, so that resonance does not occur in the working process of 20MPa and 10MPa pressure rise and fall of a brake system;
step two, designing a vibration reduction oil delivery pipe:
2.1) selecting the specification and the material of the inner oil conveying pipe, the middle pipe and the outer pipe
The inner diameter of a hydraulic pipeline of the brake system is 12mm, and in order to ensure oil supply, the inner diameter of an inner oil pipeline is more than or equal to 12 mm;
manufacturing a coaxial three-layer stainless steel oil delivery pipe, wherein the three-layer steel pipe is made of 0Cr18Ni 9; selecting an outer layer pipe: the outer diameter and the wall thickness are 50mm multiplied by 1.25mm, and the inner diameter is 47.5 mm; selecting a middle layer pipe: the outer diameter and the wall thickness are 32mm and 1mm respectively, and the inner diameter is 30 mm; selecting an inner oil conveying pipe: the outer diameter and the wall thickness are 16mm multiplied by 1.5mm, and the inner diameter is 13 mm;
2.2) calculating the strength of the inner oil pipeline
The middle-layer pipe and the outer-layer pipe are not affected by oil pressure, but the inner-layer oil conveying pipe bears high pressure, so that the strength of the inner-layer oil conveying pipe is only calculated;
tensile strength sigma of 0Cr18Ni9 steel pipebNot less than 520MPa, and allowable stress is 40 percent of tensile strength, namely sigmaAllowable use＝σb×40％＝208MPa；
According to the following calculation method, the stress sigma under the working condition of the oil pipeline is calculatedWork by：
In the formula: p: hydraulic pressure; r: the outer radius of the tubing; r: the inner radius of the oil pipe;
the maximum working pressure is 20MPa, but overshoot generated when the pressure rapidly rises reaches 30MPa, and the overshoot is used as the basis for intensity calculation, and p is 30MPa, R is 0.8cm, and R is 0.65cm, and the following formula (1) is substituted to obtain:
step three, designing an adjustable framework, a vibration reduction bracket and a hoop:
the vibration energy of the vibration-damping oil conveying pipe is absorbed by designing and installing an adjustable framework, a vibration-damping bracket and a clamp;
in order to improve the vibration reduction effect of the vibration reduction oil conveying pipe, the steel pipes of all layers are fixed by adjustable frameworks, the natural frequency of the vibration reduction oil conveying pipe is changed by adopting a method of gradually reducing the rigidity, and meanwhile, the capacity of absorbing vibration energy is improved;
in order to improve the vibration reduction effect, 1 vibration reduction bracket is laid on the concrete ground every 1500mm, a vibration reduction oil pipeline is laid on the vibration reduction bracket, and then the vibration reduction oil pipeline is fixed by a clamp;
3.1) determining the strength of the adjustable framework and the steel pipe and the matching size of the adjustable framework and the steel pipe
1Cr13 stainless steel is selected to manufacture the adjustable skeleton, in order to improve the vibration damping performance, the strength of the adjustable skeleton is lower than that of a steel pipe, and the sigma of the steel pipe is knownbMore than or equal to 520MPa, the sigma of the framework can be adjustedbSelecting 430MPa, adopting a treatment method of heating at 770-780 ℃, and calculating an empirical formula of the heat preservation time length in a salt furnace as follows:
t＝φ×17s/mm×1.5 (2)
in the formula: phi is the diameter of the bar, mm;
17s/mm means that the heat preservation time is prolonged by 17s when the diameter is increased by 1 mm;
1.5 is the coefficient;
the heat preservation duration of the adjustable framework between the middle-layer pipe and the outer-layer pipe is calculated according to the formula (2) as follows:
47.5mm × 17s/mm × 1.5 ═ 1211.25s ═ 20.1875min, 20 min;
the heat preservation time of the adjustable framework between the inner oil delivery pipe and the middle pipe is calculated according to the formula (2):
30mm × 17s/mm × 1.5 ═ 765s ═ 12.75min, take 13 min;
3.2) design of Adjustable skeleton
I, designing an adjustable framework structure between the middle-layer pipe and the outer-layer pipe;
II, designing an adjustable framework structure between the inner oil conveying pipe and the middle layer pipe;
III, determining the size a of the adjustable framework, wherein the rigidity of the adjustable framework is determined through the size a of the adjustable framework:
the adjustable framework between the middle layer pipe and the outer layer pipe, the size a initial value between the inner layer oil pipeline and the middle layer pipe is 10mm, then the adjustable framework is installed between the inner oil pipe and the outer oil pipe for vibration test, a layer of lubricating oil is uniformly coated on a matching surface when the adjustable framework is installed, the value of the symmetrical processing size a is 0.1mm respectively when vibration occurs in the test process, namely each surface is processed by 0.1mm, and the size a value of the adjustable framework between the middle layer pipe and the outer layer pipe, and the size a value of the adjustable framework between the inner layer oil pipeline and the middle layer pipe are symmetrically processed on two sides at the same time until the size without resonance is determined to be the final size of a; the testing pressure is 20MPa and 10 MPa; the test conditions were:
a) temperature of the test oil: the room temperature is minus 55 plus or minus 4 ℃, the viscosity influences the flow speed due to different oil viscosities under different temperature conditions, so that the resonance frequency is influenced, and the resonance is not required to occur within the range of the room temperature to minus 55 plus or minus 4 ℃, so that the test is carried out under different temperature conditions; starting from-55 ℃, the step length is 5 ℃, namely the oil temperature of the second test is-45 ℃, the oil temperature of the third test is-40 ℃ until the oil temperature is 25 ℃; testing whether the dimension a generates resonance at each oil temperature point, and if the dimension a generates resonance, symmetrically processing the value a on two sides, wherein the processing value is 0.1 mm;
b) the electromagnetic valve is connected with the brake system under the pressure of 20MPa, the connection/disconnection frequency of the electromagnetic valve is 10 times/min, the electromagnetic valve continuously works for 3min, if no resonance occurs within 3min, the test of the temperature point a is finished, and the test of the value a under the next temperature condition is carried out; if resonance occurs, the a value size is unavailable, and all the a value sizes which generate resonance are recorded;
c) then, the servo valve is connected with 10MPa pressure, the working frequency of the servo valve is 10 times/min, the servo valve continuously works for 3min, if no resonance occurs within 3min, the temperature point and the test of a are finished, and the next a value is tested; if resonance occurs, the a value size is unavailable, and all the a value sizes which generate resonance are recorded;
d) summarizing all the a value sizes of 20MPa and 10MPa which generate resonance, wherein the a value sizes are all unusable sizes;
3.3) design of damping brackets
The vibration reduction bracket is an assembly and is made of 1Cr13 stainless steel and rubber;
3.4) design of the clamping band
The hoop material is made of a steel strip with the thickness of 1Cr13 being 1mm, and the width of the steel strip is 20 mm;
step four, determining the installation space of the adjustable skeleton on the steel pipe
From damping bracket installation interval 1000mm, adopt the method of reducing the installation interval step by step to test whether take place the vibration, the step length that reduces at every turn is 50mm, when the installation interval is from 1000mm step-by-step reduction to 550mm, the vibration is eliminated, confirm every 500mm on same circle cross-section, install adjustable skeleton between outer layer pipe and intermediate layer pipe, install adjustable skeleton between intermediate layer pipe and inner layer defeated oil pipe, install adjustable skeleton between intermediate layer pipe and outer layer pipe altogether, adjustable skeleton between inner layer defeated oil pipe and the intermediate layer pipe respectively 20.
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| JPH0942201A (en) * | 1995-07-24 | 1997-02-10 | Komatsu Ltd | Leak oil exhausting device for oil hydraulic equipment provided in leading tube |
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| CN104772933A (en) * | 2015-02-27 | 2015-07-15 | 中国建筑股份有限公司 | Double-steel pipe composite member filled with foamed aluminum |
| CN105275905A (en) * | 2014-07-14 | 2016-01-27 | 扬州科进船业有限公司 | Automatic adaptation-connection device for oil-conveying pipeline |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0942201A (en) * | 1995-07-24 | 1997-02-10 | Komatsu Ltd | Leak oil exhausting device for oil hydraulic equipment provided in leading tube |
| CN201835397U (en) * | 2010-08-26 | 2011-05-18 | 北京市建筑设计研究院 | TMD (tuned mass damper) device |
| CN103452964A (en) * | 2013-09-12 | 2013-12-18 | 上海三一重机有限公司 | Independent hydraulic oil grading cooling system and engineering machinery |
| CN105275905A (en) * | 2014-07-14 | 2016-01-27 | 扬州科进船业有限公司 | Automatic adaptation-connection device for oil-conveying pipeline |
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