CN113761765A - Brake noise prediction method considering temperature influence - Google Patents
Brake noise prediction method considering temperature influence Download PDFInfo
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Abstract
The invention discloses a brake noise prediction method considering temperature influence, which comprises the following steps: establishing a free mode finite element model of the disc brake; performing modal test under free constraint condition; establishing a complex mode finite element model of the disc brake; performing a braking noise bench test; analyzing the influence of temperature on the contact rigidity and the friction coefficient between the brake disc and the friction lining; correcting the brake complex modal analysis model; simulating and calculating the effective temperature range of the actual braking process by using a finite element model of the disc brake; and analyzing the noise tendency of the brake noise of the same frequency band at different temperatures. Compared with the prior art, the method is beneficial to analyzing the specific characteristics of the brake noise of a certain frequency band in different temperature ranges, improves the prediction precision of the brake noise, enables people to know the brake noise more comprehensively, and can provide guidance ideas for researchers to take measures to reduce the brake noise.
Description
Technical Field
The invention relates to the field of brake noise of an automobile brake, in particular to a brake noise prediction method considering the influence of brake temperature.
Background
As automobiles become one of the essential tools for people to go out, the requirements of people on the safety of automobiles and the driving and riding comfort are higher and higher, and the performance of automobile brakes has an important influence on the safety and the comfort. When the automobile is braked, the noise emitted by the brake can damage the brake system of the automobile, so that the abrasion of the brake system of the automobile is increased, and the safety of the brake system can be damaged in a serious case. Meanwhile, the noise also influences the hearing systems of the driver and passengers, and the long-time noise can make the driver feel nervous, easily cause distraction of the driver and cause traffic accidents. In the quality report of the new automobile, the problem of brake abnormal sound of the brake becomes the quality problem which is complained most, and great trouble is brought to people.
Continuous braking causes friction to generate a large amount of heat, and the process of heat accumulation, transfer, and dissipation causes significant changes in temperature, thereby changing the material properties and mechanical structure of the friction plates and the brake disc, which may have an effect on the noise tendency during braking. The heat to temperature conversion is a complex transient process that is not easily established and verified. The temperature is a comprehensive representation of heat generation, transmission and dissipation of the brake system, and the noise trend of the brake system can be comprehensively evaluated, so that the method can be used for researching the influence on the brake noise trend. In the conventional research, only the influence of temperature on the material performance and the friction coefficient is studied, and the influence of temperature on the brake noise trend is less concerned. In order to more fully analyze the brake noise, there is a need to study the effect of temperature on the brake noise trend.
Disclosure of Invention
The invention aims to provide a brake noise prediction method considering the influence of temperature on brake noise, aiming at overcoming the defects in the prior art.
The technical scheme is as follows: a brake noise prediction method taking into account brake temperature effects, comprising the steps of:
step one, establishing a disk brake free mode analysis finite element model: firstly, establishing a three-dimensional model of key parts of a disc brake by using three-dimensional software, then performing grid division on the established simplified model of the brake by using finite element software, setting material parameters, and performing free modal analysis on a brake disc and a brake pad respectively to obtain the natural modal frequencies of the brake disc and the brake pad;
step two, performing modal test under free constraint conditions: performing free modal test on key parts of the brake, a brake disc and a brake block to obtain the inherent modal frequency of the brake, comparing the inherent modal frequency with a modal result obtained by simulation, setting the finite element model to be effective when the error between the inherent modal frequency and the modal result is less than 5%, and otherwise, returning to the step of modifying the material property parameters of the finite element model for analyzing the free modal of the brake to meet the requirement;
step three, establishing a disc brake complex modal analysis finite element model: setting constraint relations and force boundary conditions among all parts by using finite element software based on the brake free mode finite element model established in the step one, setting brake pressure and brake disc rotating speed, and obtaining modal frequency and instability trend of brake noise through complex eigenvalue analysis;
step four, brake noise test analysis is carried out: performing a noise test by using a 3900-type noise test bench produced by LINK company in America, reserving brake squeal noise data with the frequency within 1-16 kHz and the sound pressure level of 70dB or above, comparing the test data with a simulation result, and setting the coincidence degree of the unstable noise frequency obtained by simulation and the noise generation frequency measured by the test to be more than 75%, wherein the finite element model can effectively predict the brake noise, otherwise, correcting the complex modal analysis finite element model established in the step three;
and step five, analyzing the influence of the temperature on the contact rigidity and the friction coefficient between the brake disc and the friction lining: converting the influence of temperature on contact coupling rigidity into the relation between temperature and material performance, and converting the relation between the temperature and tensile strength of a brake disc into the influence of the temperature on a friction coefficient;
step six, correcting the brake complex modal analysis model: calculating the elastic modulus and the friction coefficient of the friction pair at different temperatures by using a mathematical relation among the temperature, the elastic modulus and the friction coefficient, substituting the mathematical relation into a brake complex modal finite element model to modify the model, and obtaining a brake complex modal analysis model related to the temperature;
step seven, analyzing the noise tendency of the braking noise with different frequencies at different temperatures: and performing complex modal analysis by using the corrected brake complex modal analysis finite element model to obtain complex characteristic values at corresponding temperatures, and sorting the brake noise instability trend data of the same frequency band to obtain a result curve of the change of the brake noise of the frequency along with the temperature, so that the change conditions of the brake noise of different frequencies at different temperatures can be analyzed.
In the above scheme, the parts of the finite element model of the brake established in the first step include a ventilation brake disc, a piston, brake caliper fingers, inner and outer friction linings and a brake pad back plate, and the mesh division adopts hexahedral meshes.
In the above scheme, the contact relationship among the model components in step three is the frictional contact between the brake disc and the inner and outer friction linings, the binding contact between the inner and outer friction linings and the brake pad backing plate, the elastic contact between the inner brake pad backing plate and the piston, and the elastic contact between the outer brake pad backing plate and the brake caliper fingers.
In the above solution, the boundary condition settings in the third step include the setting of the constraint conditions of applying the brake pressure uniformly distributed to the piston and the caliper surface and applying the rotational displacement about the Z-axis to the brake disk cap inner diameter end surface, and the setting of the constraint conditions of only allowing the brake disk to rotate about the axis while constraining the other degrees of freedom and only allowing the other components to move parallel to the brake disk axis Z-axis while constraining the other degrees of freedom.
The invention has the beneficial effects that:
the invention provides a novel method for predicting the brake noise tendency at different temperatures, which is beneficial to analyzing the specific characteristics of brake noise in a certain frequency range in different temperature ranges, improves the prediction precision of the brake noise, enables people to know the brake noise more comprehensively, and provides guidance ideas for researchers to take measures to reduce the occurrence of the brake noise.
Drawings
FIG. 1 is a flow chart of a method of the present invention;
FIG. 2 is a schematic three-dimensional model of a key component of the brake constructed in accordance with the present invention;
FIG. 3 is a grid-divided view of key components of the brake built in accordance with the present invention;
FIG. 4 illustrates dimensional parameters of a brake rotor according to the present invention;
FIG. 5 is a schematic diagram of the arrangement of the brake disc and brake pad measuring points in the free mode test according to the invention;
FIG. 6 is a diagram of the contact relationship between components in a finite element model for complex modal analysis of a brake established by the present invention;
FIG. 7 is a diagram of the application of pressure to the brake and the setting of the corresponding constraint boundary conditions in accordance with the present invention.
Detailed Description
The invention will be further explained with reference to the drawings.
As shown in fig. 1, a method for predicting brake noise considering the influence of brake temperature according to the present invention includes the following steps:
step one, establishing a disk brake free mode analysis finite element model: as shown in fig. 2, a three-dimensional model of key parts of the disc brake is established by using three-dimensional modeling software, the model comprises a ventilation brake disc, inner and outer friction linings, a brake back plate, a piston and a brake caliper finger, and fine structure designs such as a tool withdrawal groove, a small boss and a chamfer angle are omitted in the modeling process. And then, using finite element software to set material properties of the model and adopting hexahedral meshes to perform meshing, wherein the meshing of each part is shown in figure 3. Respectively carrying out free modal analysis on a single component on a brake disc and a brake block model, and extracting modal analysis results of the former 20-order modal orders of the components and the frequencies within 16000 Hz;
step two, performing modal test under free constraint conditions: the test platform mainly comprises a brake disc, a brake block, an exciting device, a sensor, a data acquisition system and a computer measurement and analysis system. The brake disc and the brake block are tested parts, the sensors are arranged on the brake disc and the brake block, the tested parts are excited by adopting the exciting device, the data acquisition system is connected with the other end of the sensor to collect frequency response signals of the tested parts, and the collected data are subjected to transfer function curve fitting and vibration mode order determination through the computer measurement and analysis system. Wherein the exciting device is a force hammer which can make the tested part vibrate in a selected frequency range, and the frequency response function of the tested part is determined by the ratio of the response to the cross power spectrum of the exciting force and the self power spectrum of the exciting force. For the brake disc, the coordinate system takes the working surface as the xy plane, and the direction perpendicular to the working surface through the center of the circle is the positive direction of the z axis, as shown in fig. 4. The brake disc to be tested is suspended and installed by adopting a rubber rope, 16 measuring points are uniformly arranged on the disc surface of the brake disc along a concentric circle, a sensor is installed at the appointed position of the brake disc surface, a force hammer is used for sequentially exciting each measuring point to be vertical to the disc surface, vibration is picked up at the 2 nd measuring point on the outer circle, each measuring point is knocked for 3 times by the force hammer, and a frequency response signal is obtained through a data acquisition system and an average value is obtained. For the brake block, a coordinate system also takes a working surface as an xy surface, the brake block is installed in a rubber rope suspension mode which is the same as that of the brake disc, 4 measuring points are uniformly arranged on the circumferential direction of the surface of a back plate of the brake block, each measuring point is knocked for 3 times by a force hammer, and a frequency response signal is obtained through a data acquisition system and an average value is obtained. The schematic diagram of the arrangement of the brake disc and the brake block measuring points is shown in figure 5. Then, according to the FFT principle, accurate numerical calculation is carried out on the frequency of the brake disc and the brake block, the modal parameters such as the modal vibration mode and the like among the data with equal intervals, namely, the fitting of a transfer function curve is carried out, and the modal order is determined from low frequency to high frequency during the fitting. Lab software is adopted for modal analysis and processing, the frequency is selected to perform modal order setting within 16000Hz according to the finite element analysis result, the inherent modal frequency of the brake disc and the brake pad is obtained, the inherent modal frequency is compared with the simulation result of the free modal analysis of the brake disc and the brake pad in the step I, the error between the inherent modal frequency and the brake pad is controlled within 5%, otherwise, the material properties of each part of the finite element model, including the density, the elastic modulus, the Poisson ratio and other parameters, are returned to the step I to be continuously corrected, and the simulation result is controlled within the error.
Step three, establishing a disc brake complex modal analysis finite element model: and setting contact relations among the parts based on the finite element model of the free mode of the brake established in the step one, wherein the contact relations comprise the friction contact between a brake disc and inner and outer friction linings, the binding contact between the inner and outer friction linings and a brake pad back plate, the elastic contact between the inner brake pad back plate and a piston, and the elastic contact between the outer brake pad back plate and a brake caliper finger, as shown in fig. 6. At the same time, boundary conditions are set, as shown in fig. 7, including adding evenly distributed braking forces to the piston and caliper surfaces, imparting rotational displacement about the Z-axis to the brake disk cap inner diameter end face, and limiting other degrees of freedom of the components to only retain freedom of movement along the Z-axis. Then, carrying out complex eigenvalue analysis to obtain the modal frequency and the instability trend of the brake noise.
Step four, brake noise test analysis is carried out: a LINK 3900 test bench is adopted for carrying out noise tests, thermocouples are implanted into holes drilled in the surface of the brake disc to monitor the braking temperature, the range of the braking temperature is controlled within a reasonable range of being lower than 400 ℃, and the thermocouples are arranged at the positions with the depth of 0.5mm +/-0.1 mm from the outer surface of the brake disc. The microphone is installed at a position 10cm away from the brake disc in the horizontal direction and 50cm away from the brake disc in the vertical direction, and sound measurement is performed by a frequency analyzer and a digital data collection system. And selecting the brake noise test as a deceleration brake working condition, wherein the initial brake speed is 50km/h, the final brake speed is 0.5km/h, the initial temperature of the brake is 50 ℃, the brake pressure is 25bar, and the brake is carried out for 108 times in a circulating manner. The brake squeal noise frequency of the brake assembly is within 1-16 kHz, the sound pressure level is 70dB or above, and brake noise data of the frequency band are extracted. Then comparing the brake noise occurrence frequency result obtained by the test with the brake noise occurrence frequency result obtained by the complex modal simulation in the third step, if the coincidence degree of the brake noise unstable frequency obtained by the simulation and the noise occurrence frequency obtained by the test reaches more than 75%, determining that the finite element model can effectively predict the brake noise, and if not, returning to the third step to correct the complex modal analysis finite element model;
and step five, analyzing the influence of the temperature on the contact rigidity and the friction coefficient between the brake disc and the friction lining:
the influence of temperature on contact rigidity is converted into a relation between temperature and material performance, the microscopic performance of the material in the braking process is difficult to measure, and the microscopic performance of the material is represented by using a macroscopic parameter of elastic modulus, wherein the elastic modulus is influenced by the chemical property and the temperature of the material.
Establishing a relational expression of rigidity and elastic modulus as follows:
wherein the content of the first and second substances,
in the above formula, k is stiffness, N/m; e is the elastic modulus, Pa; a is the contact area, m2(ii) a h is the thickness of the brake disc, m; phi is the central angle of the brake disc, rad; r isi(i ═ 1,2) are the inner and outer diameter, m, of the friction plate, respectively.
The elastic modulus versus temperature can be expressed as:
E＝E0(1-25αT)λ
where λ is a function determined by the natural properties of the material:
in the above formula, C is a constant related to the microscopic physical structure of the material, and is determined by the strain rate, the slip plane orientation factor, the Burgers vector, the sound velocity in the crystal, the Helmholtz free energy, and the like, and for low-carbon steel, C is 79.853; Δ F is the energy required for dislocation crossing barriers; κ is Boltzmann constant; α is a thermal expansion coefficient; e0Is the modulus of elasticity of the material at zero temperature; e is an index; t is the temperature.
When finite element analysis is performed, the contact stiffness is not the direct material property of the object, but is defined during the contact process. Therefore, the variation of the contact stiffness with temperature is characterized by the variation of the elastic modulus with temperature. The contact rigidity between the friction pairs can be changed by changing the elastic modulus of the friction pairs, so the influence of the temperature on the contact rigidity can be expressed by the relation between the temperature and the elastic modulus, and the corresponding values of the elastic modulus and the temperature of the brake disc and the brake pad can be calculated by the above formula.
The relationship between the temperature and the tensile strength of the brake disc is converted into the influence of the temperature on the friction coefficient, and the elastic modulus has a large influence on the relationship between the temperature and the tensile strength, so that the elastic modulus changing along with the temperature needs to be considered when the friction coefficient is calculated, and the accuracy of estimating the friction coefficient is improved.
First, an expression for the improved friction coefficient μ is established as follows:
wherein the content of the first and second substances,
in the above formula, ∈i(i ═ 1,2) is a dimensionless function that affects the coefficient of friction; ρ is the material density; p is the normal stress; sigma0Is the tensile strength; ν is the poisson ratio; mu.s0,μ1,μ2And b and c are constants. From the above equation, it can be seen that the friction coefficient is a function related to the elastic modulus and the tensile strength, and the temperature-to-friction coefficient relationship can be obtained by considering the temperature-to-elastic modulus and tensile strength relationship.
Since the tensile strength of structural steel is substantially constant at temperatures below 300 ℃, the relationship between the tensile strength of a brake disc and temperature can be fit to a polynomial equation, taking into account the actual material properties of the brake disc:
in the formula, beta0,β1,β2,β3,β4,β5The constant value can be determined by fitting according to the corresponding numerical value of the tensile strength and the temperature of the structural steel within the temperature range of 0-500 ℃.
The relationship between the friction coefficient and the temperature can be obtained by substituting the above formulas into an improved friction coefficient expression:
the coefficient of friction values mu (T) corresponding to different temperatures can be obtained according to the above formula.
Step six, correcting the brake complex modal analysis model: and (4) correspondingly inputting the values of the elastic modulus and the friction coefficient at different temperatures obtained by calculation into the brake complex modal analysis finite element model established in the step three one by one, so as to obtain the brake complex modal analysis model considering the temperature influence.
Step seven, analyzing the noise tendency of the braking noise with different frequencies at different temperatures: the corrected brake complex mode finite element model is used for carrying out complex characteristic value analysis at the temperatures of 50 ℃, 100 ℃, 150 ℃, 200 ℃, 250 ℃, 300 ℃, 350 ℃ and 400 ℃ respectively, so that the noise instability tendency of different frequencies at corresponding temperatures can be obtained, the noise instability tendency data of the same frequency is sorted to obtain the brake noise instability tendency change curve of the frequency at different temperatures, and the observation of the condition that the brake noise of a certain frequency changes along with the temperature can be facilitated. The instability trend of the brake noise at a certain frequency is estimated to be gradually increased and then decreased along with the increase of the temperature or gradually decreased along with the increase of the temperature.
The above-listed series of detailed descriptions are merely specific illustrations of possible embodiments of the present invention, and they are not intended to limit the scope of the present invention, and all equivalent means or modifications that do not depart from the technical spirit of the present invention are intended to be included within the scope of the present invention.
Claims (10)
1. A method for predicting brake noise in consideration of temperature influence, comprising the steps of:
step S1, establishing a disk brake free mode analysis finite element model: firstly, establishing a three-dimensional model of key parts of a disc brake, then using finite element software to perform meshing on the established simplified model of the brake and set material parameters, and performing free modal analysis on a brake disc and a brake pad respectively to obtain the natural modal frequencies of the brake disc and the brake pad;
step S2, performing modal test under free constraint conditions: performing free modal test on key parts of the brake, a brake disc and a brake block to obtain the natural modal frequency of the brake, comparing the natural modal frequency with a modal result obtained by simulation, setting the finite element model to be effective when the error between the two is less than 5%, and otherwise returning to the step S1 to modify the material property parameters of the finite element model for analyzing the free modal of the brake so as to meet the requirements;
step S3, establishing a disk brake complex modal analysis finite element model: based on the brake free mode finite element model established in the step S1, using finite element software to set constraint relations and boundary conditions among all parts, setting operation parameters in the braking process, and obtaining the modal frequency and the instability trend of the braking noise through complex eigenvalue analysis;
step S4, brake noise test analysis is carried out: performing a noise test by using a noise test bench, reserving brake squeal noise data with frequency within 1-16 kHz and sound pressure level of 70dB or above, comparing the test data with a simulation result, and setting the coincidence degree of noise instability frequency obtained by simulation and noise generation frequency measured by the test to be more than 75%, wherein the finite element model can effectively predict brake noise, otherwise, correcting the complex modal analysis finite element model established in the step S3;
step S5, analyzing the influence of temperature on the contact rigidity and friction coefficient between the brake disc and the friction lining: converting the influence of temperature on contact coupling rigidity into the relation between temperature and material performance, and converting the relation between the temperature and tensile strength of a brake disc into the influence of the temperature on a friction coefficient;
step S6, correcting the brake complex modal analysis model: calculating the elastic modulus and the friction coefficient of the friction pair at different temperatures by using a relational expression between the temperature and the elastic modulus and the friction coefficient, substituting the elastic modulus and the friction coefficient into a brake complex modal finite element model to modify the model, and obtaining a brake complex modal analysis model related to the temperature;
step S7, analyzing the noise tendency of the brake noise with different frequencies at different temperatures: and performing complex modal analysis by using the corrected brake complex modal analysis finite element model to obtain complex characteristic values at corresponding temperatures, sorting brake noise instability trend data of the same frequency band to obtain a result curve of the brake noise of the frequency changing along with the temperature, and analyzing the change conditions of the brake noise of different frequencies at different temperatures.
2. The method for predicting brake noise considering temperature influence according to claim 1, wherein the components of the brake finite element model established in the step S1 include a ventilated brake disc, a piston, brake caliper fingers, inner and outer friction linings and a brake pad backing plate, and the meshing adopts hexahedral mesh.
3. The method for predicting brake noise considering temperature influence according to claim 1, wherein the contact relationship between the mold parts in step 3 is determined as frictional contact between the brake disc and the inner and outer side friction linings, binding contact between the inner and outer side friction linings and the brake pad backing plate, elastic contact between the inner side brake pad backing plate and the piston, and elastic contact between the outer side brake pad backing plate and the brake caliper fingers.
4. The method of claim 1, wherein the boundary condition setting in step S3 includes applying uniformly distributed braking pressure to the piston and caliper surfaces and rotational displacement about the Z-axis to the brake disk cap inner diameter end surface, and a constraint condition setting that only allows rotation of the brake disk about the axis while constraining other degrees of freedom and only allows movement of other components parallel to the Z-axis of the brake disk while constraining other degrees of freedom.
5. The method for predicting braking noise considering temperature influence according to claim 1, wherein the specific implementation method of the step S2 includes:
the exciting device uses a force hammer to make the tested part vibrate in a selected frequency range, and determines the frequency response function of the tested part through the ratio of the response and the cross power spectrum of the exciting force and the self power spectrum of the exciting force; for the brake disc, a coordinate system is established by taking the working surface as an xy plane and taking the direction perpendicular to the working surface through the center of a circle as the positive direction of a z axis; the brake disc to be tested is suspended and installed by adopting a rubber rope, 16 measuring points are uniformly distributed on the disc surface of the brake disc along a concentric circle, a sensor is installed at a specified position of the disc surface of the brake disc, the measuring points are sequentially excited by a force hammer perpendicular to the disc surface, the vibration is picked up at the 2 nd measuring point on the outer circle, each measuring point is knocked by the force hammer for 3 times, and a frequency response signal is obtained through a data acquisition system and an average value is obtained; for the brake block, a coordinate system is established by taking the working surface as an xy surface and the direction perpendicular to the working surface through the center of a circle as the positive direction of a z axis, the brake block is installed in the same rubber rope suspension mode as the brake disc, 4 measuring points are uniformly arranged on the circumferential direction of the surface of a back plate of the brake block, each measuring point is knocked by a force hammer for 3 times, and a frequency response signal is obtained through a data acquisition system and an average value is obtained; then, according to the FFT principle, carrying out accurate numerical calculation on the frequency of the brake disc and the brake block, the modal parameters such as the modal vibration mode and the like between the data with equal intervals, namely fitting a transfer function curve, and firstly determining the modal order from low frequency to high frequency during fitting; lab software is adopted for modal analysis and processing, the frequency is selected to carry out modal order setting within 16000Hz according to the finite element analysis result, the inherent modal frequencies of the brake disc and the brake block are obtained, the inherent modal frequencies are compared with the simulation result, the error between the two is controlled within 5%, otherwise, the step S1 is returned to continuously correct the material properties of each component of the finite element model, including the parameters such as density, elastic modulus, Poisson ratio and the like, and the simulation result is controlled within the error.
6. The method for predicting braking noise considering temperature influence according to claim 1, wherein in the step S3, the constraint relationship among the components specifically includes: the brake disc is in frictional contact with the inner and outer friction linings, the inner and outer friction linings are in binding contact with the brake pad back plate, the inner brake pad back plate is in elastic contact with the piston, and the outer brake pad back plate is in elastic contact with the brake caliper fingers;
the boundary conditions include: the addition of evenly distributed braking forces on the piston and caliper surfaces, the application of rotational displacement about the Z-axis to the brake disk cap inner diameter end face, and the restriction of other degrees of freedom of the components only preserve the freedom of movement along the Z-axis.
7. The method for predicting braking noise considering temperature influence according to claim 1, wherein the specific implementation method of the step S4 includes:
a LINK 3900 test stand is adopted for carrying out a noise test, a thermocouple is implanted in a hole drilled in the surface of the brake disc to monitor and control the range of the braking temperature within a reasonable range of being lower than 400 ℃, and the thermocouple is arranged at a position with the depth of 0.5mm +/-0.1 mm from the outer surface of the brake disc; the microphone is arranged at a position which is 10cm away from the brake disc in the horizontal direction and 50cm away from the brake disc in the vertical direction for noise collection, and a frequency analyzer and a digital data collection system are used for sound measurement; selecting the brake noise test as a deceleration brake working condition, wherein the initial brake speed is 50km/h, the final brake speed is 0.5km/h, the initial brake temperature is 50 ℃, the brake pressure is 25bar, and the brake is carried out for 108 times in a circulating manner; the brake squeal noise frequency of the brake assembly is within 1-16 kHz, the sound pressure level is 70dB or above, and brake noise data of the frequency band are extracted; and then comparing the test data with the simulation result, if the coincidence degree of the unstable frequency of the brake noise obtained by simulation and the noise generation frequency measured by the test reaches more than 75%, considering that the finite element model can effectively predict the brake noise, and if not, returning to the step S3 to correct the complex modal analysis finite element model.
8. The method for predicting the braking noise considering the temperature influence according to claim 1, wherein the analyzing method for converting the influence of the temperature on the contact coupling stiffness into the relation between the temperature and the material performance in the step S5 comprises the following steps:
aiming at the difficulty in measuring the microscopic properties of the material in the braking process, the macroscopic parameter of the elastic modulus is used for representing the microscopic properties of the material, and the elastic modulus is influenced by the chemical properties and the temperature of the material; specifically, the method comprises the following steps:
establishing a relational expression of rigidity and elastic modulus as follows:
wherein the content of the first and second substances,
in the above formula, k is stiffness, N/m; e is the elastic modulus, Pa; a is the contact area, m2(ii) a h is the thickness of the brake disc, m; phi is the central angle of the brake disc, rad; r isi(i ═ 1,2) are the inner and outer diameter of the friction plate, m, respectively;
the elastic modulus versus temperature can be expressed as:
E＝E0(1-25αT)λ
where λ is a function determined by the natural properties of the material:
in the above formula, C is a constant related to the microscopic physical structure of the material, and is determined by the strain rate, the slip plane orientation factor, the Burgers vector, the sound velocity in the crystal, the Helmholtz free energy, and the like, and for low-carbon steel, C is 79.853; Δ F is the energy required for dislocation crossing barriers; κ is Boltzmann constant; α is a thermal expansion coefficient; e0Is the modulus of elasticity of the material at zero temperature; e is an index; t is the temperature.
9. The method for predicting braking noise considering temperature influence according to claim 1, wherein in the step S5, the analysis method for converting the relationship between temperature and brake disc tensile strength into the influence of temperature on the friction coefficient comprises the following steps:
first, an expression for the improved coefficient of friction is established as follows:
wherein the content of the first and second substances,
in the above formula, ∈i(i ═ 1,2) is a dimensionless function that affects the coefficient of friction; ρ is the material density; p is the normal stress; sigma0Is the tensile strength; ν is the poisson ratio; mu.s0，μ1，μ2And b and c are constants. From the above formula, it can be seen that the friction coefficient is a function related to the elastic modulus and the tensile strength, and the relationship between the temperature and the friction coefficient can be obtained by considering the relationship between the temperature and the elastic modulus and the tensile strength;
since the tensile strength of structural steel is substantially constant at temperatures below 300 ℃, the relationship between the tensile strength of a brake disc and temperature can be fit to a polynomial equation, taking into account the actual material properties of the brake disc:
in the formula, beta0，β1，β2，β3，β4，β5The constant value is a constant, and can be determined by fitting according to the corresponding numerical value of the tensile strength and the temperature of the structural steel within the temperature range of 0-500 ℃;
the relationship between the friction coefficient and the temperature can be obtained by substituting the above formulas into an improved friction coefficient expression:
the coefficient of friction values mu (T) corresponding to different temperatures can be obtained according to the above formula.
10. The method for predicting brake noise considering temperature influence according to claim 1, wherein in step S6, the elastic modulus and the friction coefficient of the friction pair at different temperatures are calculated and substituted into the finite element model of the multiple modes of the brake to modify the model, and the process includes the following steps:
and respectively calculating corresponding values of the friction coefficient and the elastic modulus of the friction pair at the temperatures of 50 ℃, 100 ℃, 150 ℃, 200 ℃, 250 ℃, 300 ℃, 350 ℃ and 400 ℃, then inputting the values of the friction coefficient, the elastic modulus and the temperature in one-to-one correspondence into the brake complex modal analysis finite element model established in the step S3, and obtaining the corresponding values of the friction coefficient and the elastic modulus of the finite element model at different temperatures in the simulation process.
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