Brake squeal prediction method based on contact characteristic hierarchical simulation

Abstract

The invention relates to a brake squeal prediction method based on contact characteristic hierarchical simulation. The method comprises the following steps: S1, a brake friction squeal test; s2, carrying out a friction squeal constraint modal test; s3, key dynamic connection and contact rigidity measurement; s4, contact rigidity layering setting: a plurality of thin-layer structures are arranged on the surface of the brake block in a partitioned manner, a contact area is divided into a plurality of sub-contact areas, different material attributes are given to the sub-contact areas, and a disc-block system layering contact physical model is constructed; s5, establishing a friction squeal finite element model considering layered contact rigidity: distributing different rigidity values and friction coefficients for each sub-contact area, and establishing a disc block contact pressure finite element model; s6, chassis angle system constraint modal analysis; and S7, carrying out friction scream complex mode analysis. Compared with the prior art, the method can further improve the prejudgment accuracy of the braking squeal phenomenon.

Description

Technical Field

[0001] The present invention belongs to the technical field of suppressing brake squeal, and in particular relates to a brake squeal prediction method based on hierarchical simulation of contact characteristics. Background Art

[0002] The problems of brake vibration and noise seriously affect the comfort and environmental friendliness of vehicles, directly leading to economic losses and a decline in brand recognition, and have become a key problem that the automotive industry urgently needs to overcome.

[0003] Brake squeal is a dynamic bifurcation behavior, and the friction coefficient plays a central role in the analysis and suppression strategy of brake squeal. The SAE J2521 standard also specifies the requirements for the measurement and analysis of the friction coefficient. However, in the field of exploring the mechanism and predicting brake squeal, most previous studies only focused on the average friction coefficient on the surfaces of the brake disc and brake pad, and few works considered the measurement of the non-uniform characteristics of the friction coefficient and its influence on brake squeal. In terms of the control means of brake squeal, traditional methods mainly start from the perspective of mechanical vibration, and suppress brake squeal by adjusting the modal vibration characteristics of component structures. Such methods to a certain extent restrict the improvement of the prediction accuracy of brake squeal and realize the diversification of control methods based on surface topography adjustment. For example, Patent CN112380615A proposes an optimized design method for the brake disc structure for brake squeal. This method optimizes by establishing an optimized model for brake disc brake squeal and using a multi-island genetic algorithm to reduce the occurrence probability of brake squeal. However, its core still focuses on the structural optimization of the brake disc and the average friction coefficient to carry out the optimized design, without considering the influence of the non-linear surface friction coefficient on brake squeal, nor proposing corresponding suppression strategies. Patent CN117787041A discloses a brake squeal suppression method based on improving the non-uniform characteristics of the friction coefficient. By accurately obtaining the non-uniform friction coefficient between the disc and the pad through experiments and applying it to the complex modal finite element model of the brake, it improves the deficiency that the existing model can only apply a uniform friction coefficient. However, this method ignores the simulation of the hierarchical characteristics of contact characteristics and its influence on brake squeal, affecting the accuracy of analysis and judgment.

[0004] In summary, in the current mechanism analysis and prediction of brake squeal, the consideration of the hierarchical characteristics of contact characteristics is still insufficient; in terms of the control means of brake squeal, there is also a lack of innovative research from the perspective of the hierarchical characteristics of contact characteristics. Therefore, it is urgent to design a new method to achieve accurate prediction of brake squeal phenomena. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above-mentioned defects existing in the prior art and provide a brake squeal prediction method based on hierarchical simulation of contact characteristics, further improving the accuracy of predicting brake squeal phenomena.

[0006] The object of the present invention can be achieved by the following technical solutions:

[0007] The present invention provides a method for predicting brake squeal based on hierarchical simulation of contact characteristics, comprising the following steps:

[0008] S1: Brake friction squeal test: Simulate the actual braking condition based on the brake test specimen. The brake includes a brake disc and brake pads; Collect the sound pressure level and the acoustic and vibration characteristic information of key components during braking, including acceleration; At the same time, record the working condition information of the brake disc, including rotational speed, braking pressure and braking torque; After the data acquisition is completed, perform time-domain analysis, frequency-domain analysis and phase diagram analysis to extract the key information of brake squeal, including characteristic frequency, amplitude and the change law over time;

[0009] S2: Friction squeal constrained mode test: Apply the same braking pressure and braking torque as those when squeal occurs in step S1 to excite the vibration of the brake, and use the modal analysis algorithm to extract the constrained mode frequencies and modal vibration modes of the brake;

[0010] S3: Measurement of key dynamic connections and contact stiffness: Obtain the non-uniform friction coefficients and contact stiffness between various components of the brake;

[0011] S4: Hierarchical setting of contact stiffness: Set multiple thin-layer structures on the surface of the brake pads in a partitioned manner, divide the contact area into multiple sub-contact areas, and assign different material properties to each sub-contact area to construct a hierarchical contact physical model of the disc-block system;

[0012] S5: Establishment of a friction squeal finite element model considering hierarchical contact stiffness: Assign different stiffness values and friction coefficients to each sub-contact area to establish a finite element model of the disc-block contact pressure;

[0013] S6: Constrained mode analysis of the chassis corner system: Apply the braking pressure and braking torque obtained in step S1 to the finite element model of the disc-block contact pressure established in step S5, carry out the constrained mode simulation of the brake, and obtain the constrained mode and constrained mode frequencies of the brake, making them close to the test results in step S2;

[0014] S7: Friction squeal complex mode analysis: Based on the constrained mode of the chassis corner system analyzed in step S6, apply the rotational effect of the brake disc and the non-linear friction contact condition, and use the finite element method to carry out the complex mode simulation and analysis of the chassis braking corner system.

[0015] Further, in step S1, a high-precision acoustic and vibration test device is used to collect the acoustic and vibration characteristic information, and the high-precision acoustic and vibration test device includes a microphone array and an acceleration sensor.

[0016] Further, in step S2, the modal analysis algorithm includes the least squares complex frequency domain method, the frequency domain decomposition method, and their improved algorithms.

[0017] Further, in steps S2 and S1, a brake pad test specimen with the same parameters is used. The braking pressure obtained in step S1 is applied through a hydraulic device, and the braking torque obtained in step S1 is applied through a motor, so that the brake disc does not rotate under the condition of applying the braking torque. Then, the contact pressure distribution characteristics between the brake disc and the brake pad are obtained through pressure-sensitive paper.

[0018] Further, the specific process of step S3 is as follows:

[0019] S31: Install the brake using a stiffness test bench and ensure that it is in the same constraint conditions as an actual vehicle;

[0020] S32: Load or excite the brake and measure the connection stiffness and contact stiffness between components;

[0021] S33: Adopt a step-by-step contact method to obtain the non-uniform friction coefficient and contact stiffness value between the brake disc and the brake pad.

[0022] Further, in step S32, the connection stiffness and contact stiffness between components are measured by contact or non-contact measurement means. The contact measurement means includes a stiffness measurement sensor, and the non-contact measurement means includes a laser rangefinder.

[0023] Further, the specific process of step S33 is as follows:

[0024] Under the condition of contact in a certain sub-region, adjust the applied braking pressure until it is close to the contact pressure level obtained in step S2; conduct a friction coefficient test and record the disc-pad friction coefficient of a single sub-region when brake squeal occurs;

[0025] Measure and record the disc-pad friction coefficients of each sub-region one by one, integrate and analyze the data of the friction coefficients and contact stiffness of all sub-regions, and obtain a non-uniform friction coefficient distribution map between the disc and the pad.

[0026] Further, the specific process of establishing the finite element model of the disc-pad contact pressure is as follows:

[0027] According to the concept of hierarchical contact stiffness, divide multiple sub-contact regions and assign different stiffness values and friction coefficients to each sub-contact region;

[0028] Based on the data obtained from steps S1 to S3, use CAD software to construct a three-dimensional geometric model of the brake and its components;

[0029] Import the geometric model into the finite element software, and set the material properties, stiffness values, and friction characteristics of the contact surface according to the contact stiffness and non-uniform friction coefficient obtained in step S3.

[0030] Furthermore, during the modeling process, comprehensively consider the thermo-elastic behavior of the material and the factors of non-linear deformation.

[0031] Furthermore, in step S6, introduce modal contribution analysis, calculate the energy proportion or vibration amplitude contribution of each mode in the response of the braking system, and then identify the key modes that dominate brake squeal.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. The present invention proposes a brake squeal prediction method based on hierarchical simulation of contact characteristics. By carefully conducting experiments, accurately capture the hierarchical contact characteristics and non-uniform friction coefficient distribution between the disc and the pad, and incorporate these precise data into the complex modal finite element model of the brake, and carry out complex modal simulation and analysis of the chassis braking angle system; this method breaks through the limitation of traditional models that only consider uniform friction coefficients and uniform contact conditions, and can achieve accurate prediction of brake squeal phenomena.

[0034] 2. Aiming at the surface hierarchical contact characteristics of the friction pair, the present invention innovatively proposes a method of adjusting the surface contact characteristics by hierarchical modeling and analyzing the influencing factors on brake squeal; this method focuses on optimizing the hierarchical contact state between the brake disc and the brake pad, and combines with considering the distribution characteristics of non-uniform friction coefficients, effectively controls the problem of brake squeal; this strategy not only promotes the R & D process of low-noise brakes, but also greatly enhances the ride comfort of the vehicle.

[0035] 3. In addition to the basic constraint modal analysis, the present invention also introduces modal contribution analysis to comprehensively evaluate the importance of each mode during braking and its influence on brake squeal phenomena; by calculating the energy proportion or vibration amplitude contribution of each mode in the response of the braking system, the key modes that dominate brake squeal can be identified, and the physical mechanism behind it can be deeply understood; this in-depth analysis not only helps to more accurately predict the occurrence of brake squeal, but also provides a targeted optimization direction for subsequent noise control strategies. Brief Description of the Drawings

[0036] Figure 1 is a flow chart of the method of the present invention;

[0037] Figure 2 is a schematic diagram of the brake friction squeal bench system carried out in the embodiment;

[0038] Figure 3 is a time-frequency analysis diagram of the bench test noise data carried out in the embodiment,

[0039] Among them, (3a) is the time-frequency diagram of the microphone sound pressure under typical braking squeal conditions, and (3b) is the frequency spectrum diagram of the microphone sound pressure under typical braking squeal conditions;

[0040] Figure 4 It is the schematic diagram of the contact parameter bench test carried out for the embodiment,

[0041] Among them, (4a) is the tangential schematic diagram, and (4b) is the normal schematic diagram;

[0042] Figure 5 It is the schematic diagram of the finite element model of the hub angle system for the embodiment;

[0043] Figure 6 It is the schematic diagram of the contact setting of the finite element model for the embodiment;

[0044] Figure 7 It is the schematic diagram of the simulation setting of the hierarchical contact stiffness for the embodiment;

[0045] Figure 8 It is the schematic diagram of the finite element simulation result of the brake constraint mode for the embodiment;

[0046] Figure 9 It is the schematic diagram of the finite element simulation result of the complex eigenvalue for the embodiment;

[0047] Figure 10 It is the schematic diagram of the finite element simulation result of the unstable mode for the embodiment. Detailed implementation manners

[0048] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and the detailed implementation manners and specific operation processes are given, but the protection scope of the present invention is not limited to the following embodiments.

[0049] Embodiment:

[0050] This embodiment provides a braking squeal prediction method based on hierarchical simulation of contact characteristics, as Figure 1 shown, including the following steps:

[0051] S1: Brake friction squeal test.

[0052] First, prepare standard brake test specimens to simulate actual braking conditions. The brake includes a brake disc and brake pads. Then, use high-precision acoustic and vibration test equipment, such as microphone arrays and acceleration sensors, to collect acoustic and vibration characteristic information such as sound pressure level and acceleration of key components during braking. Among them, the acceleration information of key components refers to: three-directional vibration acceleration of measuring points on the surface of the brake caliper and three-directional vibration acceleration of measuring points on the surface of the steering knuckle. In addition, it is also necessary to record operating condition information such as brake disc speed, braking pressure, and braking torque to provide basic data for subsequent analysis. After data collection is completed, time-domain analysis, frequency-domain analysis, and phase diagram analysis are carried out to extract key information such as the characteristic frequency, amplitude, and variation law over time of brake squeal for use in the verification and optimization of subsequent finite element models.

[0053] S2: Frictional squeal constrained mode test.

[0054] Apply the same braking pressure as when squealing occurred in step S1 through a hydraulic device, and apply the braking torque obtained in step S1 through a motor to excite the vibration of the brake, so that the brake disc does not rotate under the condition of applying the braking torque. Then, obtain the contact pressure distribution characteristics between the brake disc and the brake pads through pressure-sensitive paper, and use the modal analysis algorithm to extract the constrained mode frequencies and modal shapes of the brake.

[0055] To obtain the modal parameters of the brake under specific constraint conditions, the same batch of brake system specimens as in step S1 should be used in step S2. In addition to strict control of parameters such as size, weight, and material composition, unified management of the surface roughness, hardness, and heat treatment process of the brake pads should also be increased. Minor differences in these parameters may affect the friction performance and vibration characteristics during braking, thus affecting the prediction accuracy of brake squeal. At the same time, a strict batch inspection process should be established to ensure that each batch of brake pad specimens can meet the preset test standards.

[0056] Modal analysis algorithms include time-domain analysis methods, such as the Ibrahim Time Domain (ITD) method and the State-Space Time Domain (STD) method. These methods extract modal parameters by directly analyzing the time-domain response of the system and have unique advantages in dealing with non-stationary signals and transient responses. Among them, the frequency-domain decomposition method and its improved algorithms extract modal parameters by decomposing the power spectral function or correlation function and combining peak picking or logarithmic decrement methods, and have the characteristics of strong anti-noise performance and flexible operation. The least-squares complex frequency-domain method uses the global characteristics of system poles and the same-denominator model to achieve high-precision identification of modal parameters, and is particularly suitable for the analysis of dense modes and small-damping modes. Combining the frequency-domain decomposition method and the least-squares complex frequency-domain method can form a complete set of modal parameter identification systems to improve the comprehensiveness and accuracy of brake squeal prediction.

[0057] S3: Key dynamic connection and contact stiffness measurement.

[0058] This step aims to obtain the connection stiffness and contact stiffness between various components of the brake, providing accurate physical parameter inputs for subsequent friction squeal prediction and suppression. First, install the brake using a stiffness test bench and ensure that it is under the same constraint conditions as in an actual vehicle. In this embodiment, a specially developed contact parameter test bench is used, and its principle is as Figure 4 shown.

[0059] Then, measure the dynamic stiffness and friction coefficient of the brake pads in step S1. Install stiffness measurement sensors at the key connection parts of the brake (including the connection part between the brake pad bottom plate and the brake retainer, and the contact part between the brake disc and the brake pad) and on the contact surface, and load or excite the brake to measure the connection stiffness and contact stiffness between various components. At the same time, to obtain the non-uniform friction coefficient, the step-by-step contact method is adopted: under the condition that only a certain area is in contact, by comparing with the contact pressure obtained in S2, finely adjust the applied braking pressure until a similar contact pressure level is reached, and then conduct a friction coefficient test, accurately record the disc-pad friction coefficient of a single segmented area when brake squeal occurs; subsequently, change different contact areas and measure and record the disc-pad friction coefficients of each segmented area one by one. Finally, collect and record the measurement data, including the loading force, displacement, and stiffness values, etc.

[0060] When measuring the contact stiffness, in addition to using stiffness measurement sensors, in a preferred embodiment, non-contact measurement means such as a laser rangefinder can also be introduced to improve the measurement accuracy and stability. At the same time, to more accurately simulate the dynamic changes during the actual braking process, the applied braking pressure and braking torque can be adjusted in real time during the loading or excitation of the brake to obtain the contact stiffness data under different working conditions.

[0061] The high-precision brake test bench and vibro-acoustic test equipment used in this embodiment, as Figure 2 shown, can comprehensively collect vibro-acoustic characteristic information such as the sound pressure level during the braking process and the acceleration of key components. After the data acquisition is completed, extract key information such as the characteristic frequency, amplitude, and the change law over time of the brake squeal. Typical results are as Figure 3 shown, where (3a) is the time-frequency diagram of the microphone sound pressure in a typical working condition of brake squeal, and (3b) is the frequency spectrum diagram of the microphone sound pressure in a typical working condition of brake squeal.

[0062] S4: Hierarchical setting of contact stiffness.

[0063] Considering the non-uniformity and anisotropy of contact conditions in actual tests, a hierarchical contact physical model of the disc-block system is constructed. The contact area is divided into multiple sub-contact areas and different material properties are assigned to the contact areas, such as Figure 7 As shown, the contact area is evenly divided on the surface of the brake block according to the radius and angle. The purpose is to discretize the contact setting on the surface of the brake block and simulate the influence of the contact characteristics of different regions on the tendency of brake squeal according to the test results. The construction of the hierarchical contact stiffness is achieved by setting multiple thin-layer structures on the surface of the brake block in a partitioned manner and setting different friction and stiffness characteristic parameters. This setting method has the following advantages: (1) greater redundancy in adjusting contact parameters; (2) anisotropic contact settings in multiple directions; (3) better simulation of distributed contact in test data. Compared with the setting of a single contact area, this method can more accurately simulate the influence of contact characteristics on brake squeal.

[0064] S5: Establishment of a finite element model of friction squeal considering hierarchical contact stiffness.

[0065] Establish a finite element model of the disc-block contact pressure. In the contact area, according to the concept of hierarchical contact stiffness, different levels of stiffness values are set; this operation can be achieved by dividing multiple areas on the contact surface and assigning different stiffness values to each area to more accurately simulate the actual contact behavior between the brake disc and the brake block.

[0066] The establishment process of the finite element model of friction squeal considering hierarchical contact stiffness is as follows: First, based on the key data collected in steps S1 to S3, use advanced CAD software to accurately construct the three-dimensional geometric models of the brake and its components, such as Figure 5 As shown. Subsequently, import the geometric model into the finite element software and carefully set the material properties, stiffness values, and friction characteristics of the contact surface according to the contact stiffness and non-uniform friction coefficient measured in step S3. The setting method is as Figure 6 shown, and the simulation setting of hierarchical contact stiffness is as Figure 7 shown. This process aims to accurately simulate the actual non-linear contact behavior between the brake disc and the brake block, thereby establishing a highly accurate finite element model.

[0067] Specifically, in the contact area, according to the concept of layered contact stiffness, multiple sub-regions are divided and different stiffness values and friction coefficients are assigned to each sub-region to accurately simulate the actual non-linear contact behavior between the brake disc and the brake pad. In addition, when establishing a finite element model of friction squeal considering layered contact stiffness, in addition to considering contact stiffness and non-uniform friction coefficients, the influence of the temperature field should also be incorporated to ensure the comprehensiveness and accuracy of the model. The heat generated during the braking process will cause changes in material properties, which in turn affect the contact characteristics and vibration behavior. Therefore, a heat conduction and thermal stress analysis module can be introduced into the model to more comprehensively simulate the physical phenomena during the braking process.

[0068] S6: Chassis corner system constraint modal analysis.

[0069] Apply the same braking pressure and braking torque obtained in step S1 to the finite element model established in step S5, conduct a brake constraint modal simulation, and obtain the brake constraint modes and constraint modal frequencies, as Figure 8 shown. By comparing with the test results in S2, ensure that the simulation results are close to the test results, thereby verifying the accuracy of the finite element model.

[0070] In addition to the basic constraint modal analysis, in a preferred embodiment, modal contribution analysis can also be introduced to comprehensively evaluate the importance of each mode during the braking process and its influence on the brake squeal phenomenon. By calculating the energy proportion or vibration amplitude contribution of each mode in the brake system response, the key modes leading to brake squeal can be identified, and the physical mechanism behind them can be deeply understood. This in-depth analysis not only helps to more accurately predict the occurrence of brake squeal, but also provides a targeted optimization direction for subsequent noise control strategies.

[0071] S7: Friction squeal complex modal analysis.

[0072] Based on the chassis corner system constraint modes analyzed in step S6, apply the rotational effect of the brake disc and the non-linear friction contact conditions, and use the finite element method to conduct a complex modal simulation and analysis of the chassis brake corner system.

[0073] The specific processes of finite element simulation and analysis in step S6 and step S7 are as follows: First, import the three-dimensional nonlinear contact characteristic model established in S4 into the finite element software. Then, according to the braking condition information obtained in S1, such as braking pressure, braking torque, etc., accurately set the loads and boundary conditions of the simulation model. In particular, it is necessary to simulate the rotational effect of the brake disc and the nonlinear friction contact conditions measured in S3 to ensure the authenticity of the simulation environment. Subsequently, run the finite element simulation, conduct a detailed analysis of the constrained modes and unstable complex modes of the brake, extract the modal frequencies and modal vibration modes of the brake, and compare and verify them with the test results in step S2 to ensure the accuracy and reliability of the simulation results.

[0074] In a preferred embodiment, in addition to comparing with the test results, sensitivity analysis and uncertainty analysis methods can also be used to evaluate the influence degree of model parameters on the simulation results. This helps to identify key parameters and optimize the model structure, improving the accuracy and reliability of brake squeal prediction. At the same time, a database management system for simulation results can also be established to facilitate subsequent data analysis and knowledge mining.

[0075] This embodiment uses advanced simulation software to simulate and analyze the dynamic response of the brake during the braking process. The results of the complex eigenvalue analysis are as Figure 9 shown. Through the above process, the vibration characteristics, energy transfer and dissipation mechanisms of the brake during the braking process, and the interaction relationships between various components can be deeply understood. At the same time, this embodiment can also extract information such as the characteristic frequency of brake squeal and the vibration modes of key components, as shown in the appendix Figure 10 , providing strong support for subsequent brake squeal suppression strategies.

[0076] This embodiment establishes a brake squeal prediction method with hierarchical contact characteristics, which can comprehensively and deeply understand the vibration characteristics of the brake and the brake squeal problem, providing strong technical support for subsequent structural optimization design and improvement.

[0077] The above description of the embodiments is for those of ordinary skill in the art to understand and use the invention. Obviously, those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative labor. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention should be within the protection scope of the present invention.

Claims

1. A braking squeal prediction method based on hierarchical simulation of contact characteristics, characterized in that It includes the following steps: S1: Brake friction squeal test: Based on the brake test sample, simulate the actual braking condition. The brake includes a brake disc and brake pads; collect the sound pressure level during braking and the acoustic and vibration characteristic information of key components, including acceleration; meanwhile, record the working condition information of the brake disc, including rotational speed, braking pressure and braking torque; After the data collection is completed, perform time-domain analysis, frequency-domain analysis and phase diagram analysis to extract the key information of brake squeal, including characteristic frequency, amplitude and the variation law with time; S2: Friction squeal constrained mode test: Apply the same braking pressure and braking torque as those when squeal occurs in step S1 to excite the vibration of the brake, and use the modal analysis algorithm to extract the constrained mode frequency and modal vibration mode of the brake; S3: Measurement of key dynamic connections and contact stiffness: Obtain the non-uniform friction coefficient and contact stiffness between various components of the brake; S4: Layered setting of contact stiffness: Set multiple thin-layer structures on the surface of the brake pads in a zoned manner, divide the contact area into multiple sub-contact areas, and assign different material properties to each sub-contact area to construct a layered contact physical model of the disc-pad system; S5: Establishment of a friction squeal finite element model considering layered contact stiffness: Assign different stiffness values and friction coefficients to each sub-contact area to establish a finite element model of the disc-pad contact pressure; S6: Constrained mode analysis of the chassis corner system: Apply the braking pressure and braking torque obtained in step S1 to the finite element model of the disc-pad contact pressure established in step S5, conduct brake constrained mode simulation, obtain the brake constrained mode and constrained mode frequency, and make it close to the test results of step S2; S7: Friction squeal complex mode analysis: Based on the constrained mode of the chassis corner system analyzed in step S6, apply the rotational effect of the brake disc and the non-linear friction contact condition, and use the finite element method to conduct complex mode simulation and analysis of the chassis braking corner system.

2. The braking squeal prediction method based on contact characteristic hierarchical simulation according to claim 1, wherein In step S1, a high-precision acoustic and vibration test device is used to collect the acoustic and vibration characteristic information. The high-precision acoustic and vibration test device includes a microphone array and an acceleration sensor.

3. A brake squeal prediction method based on hierarchical simulation of contact characteristics according to claim 1, characterized in that, In step S2, the modal analysis algorithm includes the least squares complex frequency domain method, the frequency domain decomposition method and their improved algorithms.

4. A braking squeal prediction method based on contact characteristic hierarchical simulation according to claim 1, characterized in that In steps S2 and S1, the same brake pad test sample is used. The braking pressure obtained in step S1 is applied through a hydraulic device, and the braking torque obtained in step S1 is applied through a motor, so that the brake disc does not rotate under the condition of applying the braking torque, and then the contact pressure distribution characteristic between the brake disc and the brake pads is obtained through pressure-sensitive paper.

5. A method for predicting brake squeal based on hierarchical simulation of contact characteristics according to claim 1, characterized in that The specific process of step S3 is as follows: S31: Install the brake using a stiffness test bench and ensure that it is in the same constraint condition as the actual vehicle; S32: Load or excite the brake and measure the connection stiffness and contact stiffness between various components; S33: Adopt the step-by-step contact method to obtain the non-uniform friction coefficient and contact stiffness value between the brake disc and the brake pads.

6. The braking squeal prediction method based on contact characteristic hierarchical simulation according to claim 5, wherein, In step S32, the connection stiffness and contact stiffness between components are measured by contact or non-contact measurement means. The contact measurement means includes a stiffness measurement sensor, and the non-contact measurement means includes a laser rangefinder.

7. A brake squeal prediction method based on hierarchical simulation of contact characteristics according to claim 5, characterized in that The specific process of step S33 is as follows: Under the condition of contact in a certain segmented area, adjust the applied braking pressure until the braking pressure is close to the contact pressure level obtained in step S2; conduct a friction coefficient test and record the disc-block friction coefficient of a single segmented area when brake squeal occurs. Measure and record the disc-block friction coefficients of each segmented area one by one, integrate and analyze the friction coefficient data of all segmented areas and the contact stiffness data to obtain a non-uniform friction coefficient distribution map between the disc and the block.

8. A braking squeal prediction method based on hierarchical simulation of contact characteristics according to claim 1, characterized in that The specific process of establishing the finite element model of the disc-block contact pressure is as follows: According to the concept of hierarchical contact stiffness, divide multiple sub-contact areas and assign different stiffness values and friction coefficients to each sub-contact area. Based on the data obtained from steps S1 to S3, use CAD software to construct a three-dimensional geometric model of the brake and its components. Import the geometric model into finite element software, and set the material properties, stiffness values and friction characteristics of the contact surface according to the contact stiffness and non-uniform friction coefficient obtained in step S3.

9. The braking squeal prediction method based on contact characteristic hierarchical simulation according to claim 8, wherein During the modeling process, comprehensively consider the thermo-elastic behavior of the material and the factors of non-linear deformation.

10. A braking squeal prediction method based on contact characteristic hierarchical simulation according to claim 1, characterized in that, In step S6, introduce modal contribution analysis, calculate the energy proportion or vibration amplitude contribution of each mode in the brake system response, and then identify the key modes that dominate brake squeal.

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