Small Road Surface Dynamic Friction Coefficient Evaluation Method

Abstract

The present invention discloses a method for evaluating the dynamic friction coefficient of a small road surface, belonging to the field of dynamic friction coefficient testing. A cross beam is erected at the top between two fixed brackets in the testing device. A four-bearing moving body rolls on the outside of the cross beam. A plurality of hydraulic press telescopic devices are provided at the bottom of the four-bearing moving body. A wheel fixing bracket is fixed to the stroke rod of the hydraulic press telescopic device. A full-scale automobile tire is rotatably connected to the inner side of the wheel fixing bracket. A torque sensor is provided on the inner side of the wheel fixing bracket and directly above the full-scale automobile tire. The method for evaluating the dynamic friction coefficient is to calculate the predicted dynamic friction coefficient μ* of the road surface anti-slip based on the multi-factor coupling characteristics, compare the predicted dynamic friction coefficient μ* with the actual dynamic friction coefficient μ measured by the small road surface friction testing device, and compare the obtained difference with the allowable range value of the difference, so as to complete the evaluation process of the dynamic friction coefficient of the multi-factor coupling road surface.

Description

Technical Field

[0001] The present invention relates to the field of dynamic friction coefficient testing, and particularly to a method for evaluating the dynamic friction coefficient of a small road surface. Background Art

[0002] Good anti-slip performance of the road surface is a prerequisite for ensuring traffic safety. The anti-slip performance of the road surface is jointly affected by various factors such as tire type, road surface type, weather conditions, vehicle driving speed, and tire-road contact medium. The anti-slip performance of the road surface is usually evaluated by the friction coefficient. Therefore, in order to ensure traffic safety, reliable equipment is needed to accurately measure the friction coefficient of the road surface.

[0003] Currently, the equipment for measuring the road surface friction coefficient is mainly used for on-site detection, such as the road surface pendulum friction coefficient tester, dynamic friction coefficient measuring instrument, lateral force detection vehicle, locked-wheel friction tester, etc. Among them, the road surface pendulum friction coefficient tester and the dynamic friction coefficient measuring instrument belong to single-point detection equipment, which can be used for indoor detection in addition to on-site detection. However, such equipment uses a rubber block to measure the friction force of the road surface and cannot truly reflect the friction between the tire and the road surface. The lateral force detection vehicle and the locked-wheel friction tester belong to continuous detection equipment. Compared with single-point detection equipment, such equipment uses real tires to detect the friction force of the road surface, and the detection results are more representative. However, such equipment can only be used for on-site detection and lacks guidance for road surface material design, and has the disadvantages of high detection cost and complex evaluation indexes. In addition, the above two types of equipment mainly detect conventional road surface conditions and are difficult to measure the friction coefficient of the road surface under complex working conditions such as wet, waterlogged, black ice, and snow-covered.

[0004] In summary, the existing road surface friction coefficient measurement equipment has the following problems: First, the single-point detection equipment using rubber blocks cannot reflect the friction relationship between real tires and the road surface; second, the continuous detection equipment using real tires can only be used for large-area on-site detection and is difficult to carry out in a micro-scale experimental environment; third, there is a lack of detection equipment for the change law of the road surface friction coefficient under the coupling action of multiple factors. Summary of the Invention

[0005] Technical Problems to be Solved

[0006] Aiming at the problems existing in the prior art, the purpose of the present invention is to provide a method for evaluating the dynamic friction coefficient of a small road surface, which can test the road use safety performance of various specimens such as asphalt road surface, cement road surface, road markings, and micro-surfacing, and the test result index is the dynamic friction coefficient between the tire and the road surface.

[0007] Technical Solution

[0008] To solve the above problems, the present invention adopts the following technical solutions.

[0009] Small multi - factor coupled road surface dynamic friction coefficient testing device, including two fixed brackets and a roadbed platform. The fixed brackets are arranged on the top of the roadbed platform. A cross beam is erected on the top between the two fixed brackets. A four - bearing moving body rolls on the outside of the cross beam. A plurality of hydraulic press telescopic devices are arranged at the bottom of the four - bearing moving body. A wheel fixing bracket is fixed on the stroke rod of the hydraulic press telescopic device. A full - scale automobile tire is rotatably connected to the inner side of the wheel fixing bracket. A torque sensor is arranged on the inner side of the wheel fixing bracket and directly above the full - scale automobile tire. A flat cement road surface track body is arranged on the upper surface of the roadbed platform. An experimental tank is arranged at the middle section position of the flat cement road surface track body, and the full - scale automobile tire is in contact with the flat cement road surface track body and the rut test die specimen.

[0010] The dynamic friction coefficient evaluation method realized by using the small multi - factor coupled road surface dynamic friction coefficient testing device described in Specific Embodiment 1. The dynamic friction coefficient evaluation method is based on the characteristics of real tires, and an improved real contact area function Pt(q) is proposed; based on the characteristics of tire rolling hysteresis energy dissipation, an improved shear modulus Gr(q) is proposed; based on the characteristics of road surface recession behavior, an improved power spectral density solution model Cdt(q) is proposed; based on the characteristics of multi - condition coupling changes of the road surface, a correction function f(ζ) is proposed. The real contact area function Pt(q), shear modulus Gr(q), power spectral density solution model Cdt(q) and correction function f(ζ) are combined to obtain the predicted dynamic friction coefficient μ* of road surface anti - skid based on multi - factor coupling characteristics. The predicted dynamic friction coefficient μ* is compared with the actual dynamic friction coefficient μ measured by the small road surface friction testing device, and the difference is compared with the allowable range value of the difference, so as to complete the evaluation process of the dynamic friction coefficient of the multi - factor coupled road surface.

[0011] As a preferred solution: The calculation process of proposing the improved real contact area function Pt(q) based on the characteristics of real tires is the process of calculating Pt(q) using Formula 1:

[0012]

[0013] The improved real contact area function Pt(q) based on the characteristics of the full - scale tire and the road surface texture is calculated through Formula 1;

[0014] The calculation process of proposing the improved shear modulus Gr(q) based on the characteristics of tire rolling hysteresis energy dissipation is the process of calculating Gr(q) using Formula 2:

[0015]

[0016] The improved shear modulus Gr(q) based on the characteristics of tire rolling hysteresis energy dissipation is calculated through Formula 2;

[0017] Based on the pavement deterioration behavior characteristics, the calculation process of the improved power spectral density solution model Cdt(q) is the process of calculating Cdt(q) using Equation 3:

[0018]

[0019] The improved power spectral density solution model Cdt(q) based on the pavement deterioration behavior characteristics is calculated through Equation 3;

[0020] Combined with the pavement texture wavelength λ and Equation 4, the spatial angular frequency q is obtained. Equation 4 is as follows:

[0021]

[0022] Combining Equation 1, Equation 2, Equation 3, Equation 4, and the correction function f(ζ) of the pavement multi-condition coupling change characteristics, the predicted dynamic friction coefficient μ * is calculated as follows:

[0023]

[0024] Among Equation 1, Equation 2, Equation 3, Equation 4, Equation 5, and the correction function f(ζ) of the pavement multi-condition coupling change characteristics,

[0025] μ*—is the theoretical multi-factor coupling friction coefficient solved based on the full-scale tire;

[0026] f(ζ)—is the correction function based on the pavement multi-condition coupling change;

[0027] ζ—is a constant greater than 0;

[0028] q1—is the upper limit of integration, corresponding to the short-distance cut-off wavelength;

[0029] q L —is the lower limit of integration, corresponding to the wavelength equivalent to the tread block length;

[0030] q—is the spatial angular frequency, solved through Equation 4;

[0031] q 3 —is the cube power of q;

[0032] dq—is the differential element of q;

[0033] π—is a constant, and 2π is twice that of π;

[0034] —is the angle between the wave trough propagation direction and the tire speed direction;

[0035] —is infinitesimal;

[0036] E(q·f(v)·cosφ) — is the elastic modulus of the rolling tire rubber;

[0037] — is the imaginary part of the complex modulus of rubber;

[0038] — is cosine function of;

[0039] v — is the velocity symbol;

[0040] f(v) — is the full-scale tire velocity function;

[0041] r — is the Poisson's ratio of the rubber material;

[0042] σ0 — is the stress generated by the vertical force applied to the rubber block;

[0043] Pt(q) — is the improved real contact area function of the full-scale tire and the road surface texture features; Sin(x) — is the sine function of the reconstructed texture on the positive x-axis;

[0044] exp(-x 2 G(q)) — is the exponential function with base e of the shear modulus in the x-axis direction;

[0045] dx — infinitesimal of variable x;

[0046] A0 — apparent contact area between the tire and the road surface;

[0047] A — real contact area between the tire and the road surface;

[0048] Gr(q) — is the improved shear modulus based on the tire rolling hysteresis energy dissipation characteristics;

[0049] Cdt(q) — is the improved power spectral density solution model based on the road surface decay behavior characteristics;

[0050] λ — is the road surface texture wavelength;

[0051] e — is the natural constant;

[0052] h(0) — is the surface elevation at the origin;

[0053] h(x) — is the surface elevation relative to the average cross-section;

[0054] e -i·q(t)·x — exponential function with base e of the spatial angular frequency in the positive x-axis direction;

[0055] d 2 x — second partial derivative with respect to x;

[0056] k is a natural number;

[0057] q(t) is a spatial angular frequency function based on the pavement wear time;

[0058] q0 is the reference spatial angular frequency;

[0059] H is the fractal dimension;

[0060] <…> represents the ensemble average.

[0061] As a preferred solution: Compare the predicted dynamic friction coefficient μ* with the actual dynamic friction coefficient measured by the small pavement friction test device. When the difference between the predicted dynamic friction coefficient μ* and the actual dynamic friction coefficient μ measured by the small pavement friction test device is less than 0.01, the actual dynamic friction coefficient μ measured by the small pavement friction test device is an effective and reliable value that can be used subsequently. When the difference between the predicted dynamic friction coefficient μ* and the actual dynamic friction coefficient measured by the small pavement friction test device is greater than 0.05, retesting is required.

[0062] Compared with the prior art, the advantages of the present invention are as follows:

[0063] The small pavement friction test device in the present invention is a real-time test device for the dynamic friction of the pavement that can comprehensively simulate the multi-factor coupled pavement conditions. The full-scale vehicle tire and the rut test mold specimen in the present invention are the main test components for the dynamic friction coefficient. The flat cement pavement track body is the test flat adjustment section. During the test, the full-scale vehicle tire can be rolled on the rut test mold specimen to conduct the test. Based on the "tire-medium-pavement" friction mechanism, the contact mechanism between the tire and the pavement is different under different road surface texture morphologies, different driving speeds, different tire tread patterns, different temperatures, and different water film thicknesses, which will lead to different friction torques shown by the sensor. Based on this, the device can test the road use safety performance of various specimens such as asphalt pavement, cement pavement, pavement markings, and micro-surfacing. The test result index is the dynamic friction coefficient between the tire and the pavement, which is the actual measured value. Compared with the theoretical calculation method of the dynamic friction coefficient in the friction coefficient evaluation method of the present invention, it can not only achieve the accuracy of the theoretical calculation of the dynamic friction coefficient, but also verify the difference when the small pavement friction test device in the present invention is used with different mixed medium materials by combining. By comparing the theoretical value and the actual value, the test sensitivity of the small pavement friction test device can also be verified. The road surface structure of the test device is reasonable and reliable, which is conducive to subsequent promotion and use on the actual road surface, thereby verifying that the present invention can form a reliable and reasonable quantitative reference and guiding role for the safety performance of the actual road surface. Description of the Drawings

[0064] Figure 1 It is the first three-dimensional structure schematic diagram of the small multi-factor coupled pavement dynamic friction coefficient test device in the present invention;

[0065] Figure 2 It is a front view structural schematic diagram of the connection relationship among the fixed support, the rut test mold specimen, and the full-scale automobile tire;

[0066] Figure 3 It is a side view structural schematic diagram of the connection relationship among the low-temperature refrigeration controller, the high-temperature controller, and the light ultraviolet simulator;

[0067] Figure 4 It is a three-dimensional structural schematic diagram of the connection relationship between two rut test plates and multiple controller components;

[0068] Figure 5 It is a second three-dimensional structural schematic diagram of the small and medium-sized multi-factor coupling road surface dynamic friction coefficient test device of the present invention;

[0069] Figure 6 It is a third three-dimensional structural schematic diagram of the small and medium-sized multi-factor coupling road surface dynamic friction coefficient test device of the present invention;

[0070] Figure 7 It is a first three-dimensional structural schematic diagram of the connection relationship among the four-bearing moving body, the wheel fixing bracket, the full-scale automobile tire, the hydraulic press expander, the reciprocating movement limiter, and the spray sprinkler;

[0071] Figure 8 It is a second three-dimensional structural schematic diagram of the connection relationship among the four-bearing moving body, the wheel fixing bracket, the full-scale automobile tire, the hydraulic press expander, the reciprocating movement limiter, and the spray sprinkler.

[0072] Figure 9 Schematic diagram of the principle of generating dynamic friction coefficient between the tire and the road surface;

[0073] Figure 10 It is a comparison data graph of three groups of 6 measured T0 values in the dynamic friction coefficient evaluation method of the present invention;

[0074] Figure 11 It is a data graph of the measured Ti value of the high-speed real wheel - glass in the dynamic friction coefficient evaluation method of the present invention;

[0075] Figure 12 It is a data graph of the measured Ti value of the high-speed real wheel - AC 13 in the dynamic friction coefficient evaluation method of the present invention;

[0076] Figure 13 It is a data graph of the measured Ti value of the high-speed real wheel - crumb rubber modified asphalt OGFC 13 in the dynamic friction coefficient evaluation method of the present invention

[0077] Figure 14 It is a data graph of the measured Ti value of the high-speed real wheel - polyurethane OGFC 13 in the dynamic friction coefficient evaluation method of the present invention.

[0078] Description of reference numerals in the figure:

[0079] 1. Fixed bracket; 2. Subgrade platform; 3. Four-bearing moving body; 4. Cross beam; 5. Wheel fixing bracket; 6. Full-scale automobile tire; 7. Hydraulic press expander; 8. Reciprocating movement limiter; 9. Spray sprinkler; 10. Polishing medium controller; 11. Rut test die specimen; 11-1. Rut test die plate; 12. Flat cement pavement track body; 13. Low-temperature refrigeration controller; 14. High-temperature controller; 15. Light ultraviolet simulator; 16. Rut track area. Specific implementation mode

[0080] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention; obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0081] Specific implementation mode one: In combination with Figures 1 to 9 To illustrate this implementation mode, this implementation mode includes two fixed brackets 1 and a subgrade platform 2. The fixed bracket 1 is arranged on the top of the subgrade platform 2. A cross beam 4 is erected on the top between the two fixed brackets 1. A four-bearing moving body 3 rolls outside the cross beam 4. A plurality of hydraulic press expanders 7 are arranged at the bottom of the four-bearing moving body 3. A wheel fixing bracket 5 is fixed to the stroke rod of the hydraulic press expander 7. A full-scale automobile tire 6 is rotatably connected to the inner side of the wheel fixing bracket 5. A torque sensor is arranged on the inner side of the wheel fixing bracket 5 and directly above the full-scale automobile tire 6. A flat cement pavement track body 12 is arranged on the upper surface of the subgrade platform 2. A downwardly concave experimental groove is arranged at the middle section of the flat cement pavement track body 12. A rut test die specimen 11 composed of two rut test die plates 11-1 is arranged in the experimental groove. The full-scale automobile tires 6 are respectively in rolling cooperation with the flat cement pavement track body 12 and the rut test die specimen 11.

[0082] One side of the wheel fixing bracket 5 is fixed with a spray sprinkler 9 and a polishing medium controller 10 through a connecting rod.

[0083] The two rut test die plates 11-1 are arranged in parallel. A controller assembly is correspondingly arranged at the end of each rut test die plate 11-1. Each controller assembly includes a low-temperature refrigeration controller 13 and a high-temperature controller 14. The low-temperature refrigeration controller 13 and the high-temperature controller 14 are arranged in parallel on the flat cement pavement track body 12.

[0084] A light ultraviolet simulator 15 is arranged on one side of the subgrade platform 2.

[0085] On one side of each of the two fixed brackets 1 close to the four-bearing moving body 3, a reciprocating movement limiter 8 is provided.

[0086] The working principle of the small and medium-sized multi-factor coupling road surface dynamic friction coefficient testing device of the present invention:

[0087] When the user uses the device, the cross beam 4 provides a guide rail for the reciprocating movement of the whole body; the four-bearing moving body 3 maintains the fixed speed movement of the body by the action of inertia force, the wheel fixing bracket 5 and the hydraulic press telescopic device 7 provide a vertical load for the full-scale automobile tire 6, the reciprocating movement limiter 8 controls the reciprocating movement position of the body, the full-scale automobile tire 6 and the rut test die specimen 11 are the main test components for the dynamic friction coefficient, and the flat cement road surface track body 12 is the test flat adjustment section. In the test stage of the present invention, the acquisition method of the actual dynamic friction coefficient μ can be selected from any one of the following two methods for testing:

[0088] Method 1: During the test, the full-scale automobile tire 6 rolls on the rut test die specimen 11, and the torque generated by rolling friction is recorded in real time by a sensor. The test dynamic friction coefficient μ is calculated by the following formula from the obtained torque.

[0089]

[0090] Method 2: During the test, the full-scale automobile tire 6 can roll on the rut test die specimen 11, and the torque generated by rolling friction is recorded in real time by a sensor. The torque value is transmitted to the computer terminal in real time, and the computer terminal passes through After calculation, the tested dynamic friction coefficient μ is displayed on the display.

[0091] This test device provides a front and rear moving sliding frame by a four-bearing moving vehicle, and provides a moving path by a fixed track at the lower end, so that the present invention simulates the ABS braking action of a vehicle in a small space in the laboratory. At present, the main problems of the devices for simulating vehicle braking in the laboratory are that there is only angular velocity without linear velocity, or the road surface structure is an arc structure, resulting in distortion of the tire-road contact force, while the large-scale full-scale test track occupies a huge area and the investment in the laying materials of the test track is large.

[0092] Specific Embodiment 2: Combining Figures 1 to 14 This embodiment is described. This embodiment is a process of combining the data measured by the small multi-factor coupling road surface dynamic friction coefficient testing device in Specific Embodiment 1 with the dynamic friction coefficient calculation method, and comparing and calculating the theoretical data with the actual experimental data to obtain the relevant guiding results of the dynamic friction coefficient of the actual road surface. The dynamic friction coefficient evaluation method is a multi-factor coupling road surface dynamic friction coefficient mechanism analysis and evaluation method, specifically:

[0093] The dynamic friction coefficient evaluation method is based on the characteristics of real tires, and an improved real contact area function Pt(q) is proposed; based on the tire rolling hysteresis energy dissipation characteristics, an improved shear modulus Gr(q) is proposed; based on the pavement degradation behavior characteristics, an improved power spectral density solution model Cdt(q) is proposed; based on the multi-condition coupling change characteristics of the pavement, a correction function f(ζ) is proposed. The real contact area function Pt(q), shear modulus Gr(q), power spectral density solution model Cdt(q) and correction function f(ζ) are combined to obtain the predicted dynamic friction coefficient μ* of pavement anti-skid based on multi-factor coupling characteristics. The predicted dynamic friction coefficient μ* is compared with the actual dynamic friction coefficient measured by a small pavement friction test device, and the difference is compared with the allowable range value of the difference, so as to complete the process of guiding the mechanism analysis of the dynamic friction coefficient of the multi-factor coupling pavement and the actual measurement correction.

[0094] Based on the characteristics of real tires, the calculation process of the improved real contact area function Pt(q) is the process of calculating Pt(q) using formula one:

[0095]

[0096] The improved real contact area function Pt(q) based on the full-scale tire and road surface texture morphology characteristics is calculated through formula one;

[0097] Based on the tire rolling hysteresis energy dissipation characteristics, the calculation process of the improved shear modulus Gr(q) is the process of calculating Gr(q) using formula two:

[0098]

[0099] The improved shear modulus Gr(q) based on the tire rolling hysteresis energy dissipation characteristics is calculated through formula two;

[0100] Based on the pavement degradation behavior characteristics, the calculation process of the improved power spectral density solution model Cdt(q) is the process of calculating Cdt(q) using formula three:

[0101]

[0102] The improved power spectral density solution model Cdt(q) based on the pavement degradation behavior characteristics is calculated through formula three;

[0103] Combined with the pavement texture wavelength λ and formula four, the spatial angular frequency q is obtained. Formula four is as follows:

[0104]

[0105] Combining Formula One, Formula Two, Formula Three, Formula Four and the correction function f(ζ) of the multi-condition coupling change characteristics of the road surface, the predicted dynamic friction coefficient μ is obtained. * The calculation process is as follows:

[0106]

[0107] Among Formula One, Formula Two, Formula Three, Formula Four, Formula Five and the correction function f(ζ) of the multi-condition coupling change characteristics of the road surface,

[0108] μ*—is the theoretical multi-factor coupling friction coefficient solved based on full-scale tires;

[0109] f(ζ)—is the correction function based on the multi-condition coupling change of the road surface;

[0110] ζ—is a constant greater than 0;

[0111] q1—is the upper limit of integration, corresponding to the short-distance cut-off wavelength;

[0112] q L —is the lower limit of integration, corresponding to the wavelength equivalent to the tread block length;

[0113] q—is the spatial angular frequency, solved by Formula Four;

[0114] q 3 —is the cube power of q;

[0115] dq—is the differential element of q;

[0116] π—is a constant, and 2π is twice that of π;

[0117] —is the angle between the direction of wave trough propagation and the tire speed direction;

[0118] —is the differential element of;

[0119] E(q·f(v)·cosφ)—is the elastic modulus of the rolling tire rubber;

[0120] —is the imaginary part of the complex modulus of rubber;

[0121] —is the cosine function of;

[0122] v—is the velocity symbol;

[0123] f(v)—is the full-scale tire speed function;

[0124] r—is the Poisson's ratio of the rubber material;

[0125] σ0—the stress generated by the vertical force applied to the rubber block;

[0126] Pt(q)—the improved true contact area function of the base-footprint tire and the road surface texture features;

[0127] Sin(x)—the sine function on the x-axis of the reconstructed texture;

[0128] exp(-x 2 G(q))—the exponential function with base e of the shear modulus in the x-axis direction;

[0129] dx—the differential element of the variable x;

[0130] A0—the apparent contact area between the tire and the road surface;

[0131] A—the true contact area between the tire and the road surface;

[0132] Gr(q)—the improved shear modulus based on the tire rolling hysteresis energy dissipation characteristics;

[0133] Cdt(q)—the improved power spectral density solution model based on the road surface decay behavior characteristics;

[0134] λ—the road surface texture wavelength;

[0135] e—the natural constant;

[0136] h(0)—the surface elevation at the origin;

[0137] h(x)—the surface elevation relative to the average cross-section;

[0138] e -i·q(t)·x —the exponential function with base e of the spatial angular frequency in the x-axis upward direction;

[0139] d 2 x—the second partial derivative of x;

[0140] k—a natural number;

[0141] q(t)—the spatial angular frequency function based on the road surface wear time;

[0142] q0—the reference spatial angular frequency;

[0143] H—the fractal dimension;

[0144] <…>—the ensemble average.

[0145] The predicted dynamic friction coefficient μ* is compared with the actual dynamic friction coefficient μ measured by a small-scale road surface friction testing device, specifically by comparing the actual numerical values. After the comparison, evaluation and analysis are carried out. When the difference between the predicted dynamic friction coefficient μ* and the actual dynamic friction coefficient μ measured by the small-scale road surface friction testing device is less than 0.01, it indicates that the actual dynamic friction coefficient μ measured by the small-scale road surface friction testing device is an effective and reliable value that can be used subsequently. This value can be used for subsequent tests and analyses. When the difference between the predicted dynamic friction coefficient μ* and the actual dynamic friction coefficient μ measured by the small-scale road surface friction testing device is greater than 0.05, it is necessary to retest or adjust the connection relationship between relevant components in the small-scale road surface friction testing device and the material composition of the top surface of the flat cement road track body 12, and then conduct a new comparison, analysis, or further adjustment until the specification difference is met, and then the test operation can be stopped.

[0146] Furthermore, when retesting, the set thickness of the rut test mold specimen 11 and the form of the relevant material composition can also be adjusted.

[0147] The establishment process of the dynamic friction evaluation method in the present invention is as follows:

[0148] Persson's contact theory simplifies the tire-road contact problem into the elastic contact behavior between a smooth rubber plane and a rough surface with fractal characteristics. By summing at different wavelength scales (L / ζ), the actual contact area ratio P(q) under macroscopic contact action can be further solved, as shown in Equations (6)-(8).

[0149]

[0150] In the above formula: P(q) — is the true contact area function; G(q) — is the shear modulus; C(q) — is the two-dimensional power spectral density; q L — is the lower limit of integration, corresponding to the wavelength equivalent to the tread block length; q1 — is the upper limit of integration, corresponding to the short-distance cut-off wavelength; q — is the spatial angular frequency; σ0 — is the stress generated by the vertical force applied to the rubber block; v — is the rubber sliding speed; r — is the Poisson's ratio of the rubber material; — is the angle between the direction of propagation of the wave trough and the rubber sliding direction; λ — is the road surface texture wavelength; e — is the natural constant; h(0) — is the surface elevation at the origin; h(x) — is the surface elevation relative to the average cross-section; E(qvcosφ) is the complex modulus of the rubber; <…> — is the ensemble average calculation).

[0151] Specific Embodiment 3: This embodiment is a further limitation of Specific Embodiment 2. In this embodiment, the predicted dynamic friction coefficient μ* is proposed, and the corresponding construction and correction of the predicted dynamic friction coefficient μ* can be carried out. Specifically:

[0152] After Persson et al. established the fractal contact theory, they further proposed a theoretical mechanical model of the Persson friction coefficient based on the elastic characteristics of rubber blocks, as shown in Equation (9). Through in-depth research on the Persson fractal contact theory, it can be found that the true contact area between the tire and the road surface is smaller than the apparent contact area, and the size of the true contact area is affected by factors such as load, tread rubber, road surface texture, medium, and temperature, which in turn leads to changes in the friction coefficient between the rubber and the fractal road surface. The specific effects and resulting corrections are as follows: (a) Influence of vehicle driving speed (v). Different vehicle driving speeds lead to changes in the rubber sliding speed at the tire-road contact interface, which in turn leads to changes in the rubber composite modulus E(qvcosφ); (b) Influence of water film thickness. When the road surface is dry, the short-distance cut-off wavelength of the road surface is related to the road surface dust and the wear particles of the tire rubber. When the road surface is wet, the short-distance cut-off wavelength of the road surface is related to the rough texture penetrating upward through the water film and the scale of the small puddles on the road surface. Specifically, it can be calculated by q1 = 2π / λ1 (λ1 is the short-distance cut-off wavelength), which in turn leads to changes in the rubber shear modulus G(q); (c) Influence of vehicle load. The vehicle load mainly affects the magnitude of the macroscopic contact stress σ0, which in turn leads to changes in the rubber shear modulus G(q); (d) Influence of environmental temperature. At temperature T, the complex modulus of the tread rubber under the load with angular frequency ω = qvscosφ is E(qvscosφ,T), which in turn leads to changes in the rubber composite modulus; (e) Influence of road surface texture degradation. Road surface texture degradation leads to changes in the relative average cross-section elevation h(x), which in turn leads to changes in the road surface power spectrum.

[0153]

[0154] Although the theoretical mechanical model of the Persson friction coefficient plays a crucial role in theoretical derivation, tire-road contact, third-party software modeling, rubber material research, and other fields, the current theoretical analysis model still cannot be directly applied to the tire-road anti-slip research under the coupling action of multiple factors. Because its construction basis is the contact behavior between rubber sliders and fractal road surfaces, and the convergence conditions such as water film, temperature, and medium in the model are idealized, there are certain differences from the true tire-road friction behavior. Based on this, an improved multi-factor coupling anti-slip model based on the true contact characteristics of tires and road surfaces is proposed. Specifically, based on the true tire characteristics of tire pressure, tread pattern, and material, an improved true contact area function Pt(q) is proposed; based on the tire rolling hysteresis energy dissipation characteristics, an improved shear modulus Gr(q) is proposed; based on the road surface degradation behavior characteristics, an improved power spectrum density solution model Cdt(q) is proposed; based on the multi-condition coupling change characteristics of the road surface, a correction function f(ζ) is proposed. Finally, a road surface anti-slip prediction model, μ*, based on multi-factor coupling characteristics is obtained, as shown in Equation (19).

[0155]

[0156] Combined with Figure 10 , the calculation process of the dynamic friction coefficient between the tire and the road surface under the multi-factor coupling action is finally determined as follows:

[0157]

[0158] The improved real contact area function Pt(q) of the full-scale tire and the road surface texture morphology characteristics is calculated through Formula 1;

[0159] Based on the tire rolling hysteresis energy dissipation characteristics, the calculation process of the improved shear modulus Gr(q) is the process of calculating Gr(q) using Formula 2:

[0160]

[0161] The improved shear modulus Gr(q) based on the tire rolling hysteresis energy dissipation characteristics is calculated through Formula 2;

[0162] Based on the pavement deterioration behavior characteristics, the calculation process of the improved power spectral density solution model Cdt(q) is the process of calculating Cdt(q) using Formula 3:

[0163]

[0164] The improved power spectral density solution model Cdt(q) based on the pavement deterioration behavior characteristics is calculated through Formula 3;

[0165] Combined with the pavement texture wavelength λ and Formula 4, the spatial angular frequency q is obtained. Formula 4 is as follows:

[0166]

[0167] Combined Formula 1, Formula 2, Formula 3, Formula 4 and the correction function f(ζ) of the multi-condition coupling change characteristics of the road surface, the predicted dynamic friction coefficient μ * is calculated as follows:

[0168]

[0169] Specific Embodiment 4: This embodiment is a further limitation of Specific Embodiment 1, 2 or 3. In the dynamic friction coefficient evaluation method of the present invention, the conversion formula between the torque test value and the dynamic friction coefficient can also be carried out, as shown in Equation (6):

[0170]

[0171] In the formula: μ—dynamic friction coefficient; Ff—rolling friction force;

[0172] FN - Contact load (measured by contact force sensor);

[0173] Ffi - Rolling friction force during the i-th second of tire-specimen contact (including interfering forces such as air resistance);

[0174] Ti - Torque value during tire-specimen contact;

[0175] F0 - Air resistance when suspended without contact and stable, i.e., the total interfering force;

[0176] T0 - Torque value when suspended and stable; R - Tire radius.

[0177] The differences in the tire-road dynamic friction coefficient caused by different road surface texture morphologies, different driving speeds, different loads, different water film thicknesses, etc. in the present invention are shown in Table 1.

[0178] Table 1. Test results of dynamic friction coefficient of small-scale road surface friction test device under the coupling action of multiple factors

[0179]

[0180]

[0181] Combined with Figures 1 to 14 The present invention also conducts relevant comparative experimental tests and calculations. The specific process is as follows:

[0182] The present invention can obtain reasonable measurement values through the torque conversion method, which are close to BPN / 100. The measurement results are stable for multiple times and are more sensitive to material differences.

[0183] The common SFC dynamic friction coefficient calculation formula is selected for this calculation of the dynamic friction coefficient, and it is:

[0184]

[0185] μ - Dynamic friction coefficient;

[0186] F f - Rolling friction force;

[0187] F N - Contact load (measured by contact force sensor).

[0188] In this device, F f = F fi - F0

[0189] (F fi—Rolling friction force when the tire contacts the specimen at the i-th second (including interference forces such as air resistance); Ti—Torque value when the tire contacts the specimen; R—Tire radius);

[0190] (F0—Air resistance when suspended without contact and stable, that is, the sum of other interference forces, named: Total interference force; T0—Torque value when suspended and stable; R—Tire radius).

[0191] Through actual measurement, it can be obtained that: F N = 240 kg. The total load for this test is 240 kg and can be exchanged.

[0192] The test tire radius is r = 0.28 m

[0193] Combined with Figure 10 As shown, through six actual measurements of T0 values in three groups, it can be obtained that: F0 = 3.93 N (T0—1.1 Nm)

[0194] The actual output normal torque of this hydraulic press is 550 N*m, and the torque display data table needs to be expanded by 10 times.

[0195] (1) Combined with Figure 11 As shown, glass - dry (actual measurement of Ti value)

[0196] (1)

[0197] (2)

[0198]

[0199] The average value of (1) and (2) in the above calculation results is 0.2587.

[0200] (2) Combined with Figure 12 As shown, AC 13 (Liaohe 70) - dry (actual measurement of Ti value)

[0201] (1)

[0202] (2)

[0203]

[0204] The average value of (1) and (2) in the above calculation results is 0.616.

[0205] (3) Combined with Figure 13 As shown, crumb rubber modified asphalt OGFC 13 - dry (actual measurement of Ti value)

[0206] (1)

[0207] (2)

[0208]

[0209] The average value of (1) and (2) in the above calculation results is 0.555.

[0210] (IV) Combination Figure 14 As shown, polyurethane OGFC 13 - dry (measured Ti value)

[0211] (1)

[0212] (2)

[0213]

[0214] The average value of (1) and (2) in the above polyurethane calculation results is 0.651.

[0215] From the above data and calculations, the following conclusions can be drawn:

[0216] (1) Since the real tire of the anti - skid integrated machine carries a larger load and has a larger contact area, therefore:

[0217] μ 玻璃-抗滑一体机测试 (0.2587) > μ 玻璃-BPN (0.212)

[0218] (2) Since the rutting plate in this test has been polished for 150 minutes, thus:

[0219] μ BPN-AC13 (0.668) > μ BPN - 聚氨酯OGFC13 (0.648) > μ BPN-胶粉改性AC13 (0.622);

[0220] μ 一体机-聚氨酯OGFC13 (0.651) > μ 一体机-AC13 (0.616) > μ 一体机-胶粉改性AC13 (0.555)

[0221] (3) The test values of each group in this test are relatively stable and reliable. Through this test, it can be known that the structure and connection relationship of the small - scale road surface friction test device used in this test are set reasonably and reliably, and further test can be carried out on a larger area.

[0222] Combined with the beneficial effects of the present invention, the following embodiments are described:

[0223] Embodiment 1: Please refer to Figures 1-14, A small-scale road surface dynamic friction coefficient evaluation method, including two fixed brackets 1 and a roadbed platform 2. On one side of the roadbed platform 2, there is a light ultraviolet simulator 15. The light ultraviolet simulator 15 provides a certain ultraviolet simulation environment for the test site and device, and can simulate the light aging state of asphalt mixture. Around the roadbed platform 2, there are a low-temperature refrigeration controller 13 and a high-temperature controller 14. The low-temperature refrigeration controller 13 and the high-temperature controller 14 provide a specified temperature for the entire test device and site, and the low-temperature refrigeration controller 13 and the high-temperature controller 14 can be set in two groups on both sides of the roadbed platform 2 respectively, and are located on both sides of the specimen respectively, which is convenient for measurement and control;

[0224] The fixed brackets 1 are arranged on the top of the roadbed platform 2. A cross beam 4 is erected on the top between the two fixed brackets 1. A four-bearing moving body 3 rolls on the outside of the cross beam 4. On one side of the two fixed brackets 1 close to the four-bearing moving body 3, there are reciprocating movement limiters 8. The reciprocating movement limiter 8 can block the advancing position of the four-bearing moving body 3, thereby controlling the reciprocating movement position of the machine body. A plurality of hydraulic machine telescopic devices 7 are arranged at the bottom of the four-bearing moving body 3. The load application power system is provided by the hydraulic machine telescopic device 7. The load application preservation system is implemented by the reaction force weight structure fixed to the upper end of the fixed connection wheel frame. Based on such a structural design, the contact force can be maintained unchanged with an accuracy level of ±10N during the reciprocating movement of the tire. The stroke rod of the hydraulic machine telescopic device 7 is fixed with a wheel fixing frame 5. On one side of the wheel fixing frame 5, a spray sprinkler 9 and a polishing medium controller 10 are fixed through a connecting rod. The spray sprinkler 9 and the polishing medium controller 10 are located in front of the tire and the road surface to provide contact interface medium;

[0225] A full-scale vehicle tire 6 is rotatably connected to the inner side of the wheel fixing frame 5. A torque sensor is arranged above the full-scale vehicle tire 6 on the inner side of the wheel fixing frame 5. The torque sensor is arranged inside the fixed connection wheel frame, directly above the tire. Due to the arc structure and the telescopic touch structure, it can sensitively sense the different frictional resistances generated between different friction pairs, and the torque test accuracy level reaches 0.01 level. On the upper surface of the roadbed platform 2, there is a flat cement pavement track body 12. An experimental groove is arranged at the middle section of the flat cement pavement track body 12. The experimental groove is for the rut test die specimen 11, providing the setting of the rut test die specimen 11, so that the rut test die specimen 11 provides frictional force for the full-scale vehicle tire 6, and thus can test the full-scale vehicle tire 6, and the full-scale vehicle tire 6 is in contact with the flat cement pavement track body 12 and the rut test die specimen 11. The cross beam 4 provides a guide rail for the reciprocating movement of the entire machine body;

[0226] The four-bearing moving body 3 moves at a fixed speed of the tire to maintain the body under the action of inertial force; the wheel fixing bracket 5 and the hydraulic telescopic device 7 provide vertical loads for the full-scale automobile tire 6; the reciprocating movement limiter 8 controls the reciprocating movement position of the body, the full-scale automobile tire 6 and the rut test die specimen 11 are the main test components for the dynamic friction coefficient, and the flat cement pavement track body 12 is the test flat adjustment section.

[0227] In the present invention, the method for evaluating the dynamic friction coefficient is a reliable method that can more accurately obtain the accuracy of the theoretical dynamic friction coefficient. The small road surface friction testing device in the present invention can verify the accuracy of its test data through the method for evaluating the dynamic friction coefficient, so that the present invention has the effect of self-verification. When the data obtained by comparing and verifying the small road surface friction testing device is accurate and reliable, the small road surface friction testing device in the present invention can also be used in an enlarged proportion, realizing an orderly process of further expanding and popularizing after self-verification with low cost and stability.

[0228] The above is only a preferred specific embodiment of the present invention; however, the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution of the present invention and its improved concept, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A method for evaluating the dynamic friction coefficient of a small road surface, characterized in that: The small-scale road surface dynamic friction coefficient evaluation method is based on the characteristics of real tires, and an improved real contact area function Pt(q) is proposed; Based on the tire rolling hysteresis energy dissipation characteristics, an improved shear modulus Gr(q) is proposed; Based on the road surface degradation behavior characteristics, an improved power spectral density solution model Cdt(q) is proposed; Based on the characteristics of multi-condition coupling changes of the road surface, a correction function f(ζ) is proposed. The real contact area function Pt(q), the shear modulus Gr(q), the power spectral density solution model Cdt(q), and the correction function f(ζ) are combined to obtain the predicted dynamic friction coefficient μ* of road surface anti-slip based on the multi-factor coupling characteristics of full-scale wheels. The predicted dynamic friction coefficient μ* is compared with the actual dynamic friction coefficient measured by the small-scale road surface friction test device, and the difference is compared with the allowable range value of the difference, so as to complete the evaluation process of the dynamic friction coefficient of the multi-factor coupling road surface; The calculation process of the predicted dynamic friction coefficient μ* is as follows: In the above formula, μ*—is the theoretical multi-factor coupling friction coefficient solved based on full-scale tires; f(ζ)—is the correction function based on the multi-condition coupling changes of the road surface; — is the imaginary part of the complex modulus of rubber; Pt(q)—is the improved real contact area function based on the full-scale tire and road surface texture morphology characteristics; Cdt(q)—is the improved power spectral density solution model based on the road surface degradation behavior characteristics.

2. The small-scale road surface dynamic friction coefficient evaluation method according to claim 1, characterized in that: Based on the characteristics of real tires, the calculation process of proposing the improved real contact area function Pt(q) is the process of calculating Pt(q) using formula one: The improved real contact area function Pt(q) based on the full-scale tire and road surface texture morphology characteristics is calculated through formula one; Based on the tire rolling hysteresis energy dissipation characteristics, the calculation process of proposing the improved shear modulus Gr(q) is the process of calculating Gr(q) using formula two: The improved shear modulus Gr(q) based on the tire rolling hysteresis energy dissipation characteristics is calculated through formula two; Based on the road surface degradation behavior characteristics, the calculation process of proposing the improved power spectral density solution model Cdt(q) is the process of calculating Cdt(q) using formula three: The improved power spectral density solution model Cdt(q) based on the road surface degradation behavior characteristics is calculated through formula three; Combining the road surface texture wavelength λ with formula four to obtain the spatial angular frequency q. Formula four is as follows: Combining formula one, formula two, formula three, formula four, and the correction function f(ζ) of the multi-condition coupling changes of the road surface to obtain the predicted dynamic friction coefficient μ*; In formula one, formula two, formula three, formula four, formula five, and the correction function f(ζ) of the multi-condition coupling changes of the road surface, ζ—is a constant greater than 0; q1—is the upper limit of integration, corresponding to the short-distance cut-off wavelength; q L — is the lower integration limit, corresponding to the wavelength equivalent to the tread block length; q—is the spatial angular frequency, solved through formula four; q 3 — the cube power of q; dq—is the differential element of q; π—is a constant, and 2π is twice that of π; — is the angle between the wave fall amount propagation direction and the tire speed direction; — is a microelement of; E(q·f(v)·cosφ)—is the elastic modulus of the rolling tire rubber; — is the cosine function of; v—is the velocity symbol; f(v)—is the full-scale tire velocity function; r—is the Poisson's ratio of the rubber material; σ0—the stress generated by the vertical force applied to the rubber block; Sin(x)—the sine function of the reconstructed texture x-axis; exp(-x 2 G(q)) — Shear modulus x-axis exponential function with base e; dx—the differential element of the variable x; A0—the apparent contact area between the tire and the road surface; A—the actual contact area between the tire and the road surface; Gr(q)—the improved shear modulus based on the tire rolling hysteresis energy dissipation characteristics; λ—the wavelength of the road surface texture; e—the natural constant; h(0)—the surface elevation at the origin; h(x)—the surface elevation relative to the average cross-section; e -i·q(t)·x — The exponential function with base e of the spatial angular frequency in the x-axis upward direction; d 2 The second partial derivative of x with respect to x; k—a natural number; q(t)—the spatial angular frequency function based on the road surface wear time; q0—the reference spatial angular frequency; H—the fractal dimension; <…>—the ensemble average.

3. The small pavement dynamic friction coefficient evaluation method according to claim 1 or 2, characterized in that: Compare the predicted dynamic friction coefficient μ* with the actual dynamic friction coefficient μ measured by the small-scale road surface friction test device. When the difference between the predicted dynamic friction coefficient μ* and the actual dynamic friction coefficient μ measured by the small-scale road surface friction test device is less than 0.01, the actual dynamic friction coefficient μ measured by the small-scale road surface friction test device is an effective and reliable value for subsequent use. When the difference between the predicted dynamic friction coefficient μ* and the actual dynamic friction coefficient measured by the small-scale road surface friction test device is greater than 0.05, re-testing is required.

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