Asphalt mixture fatigue performance testing device and method

Abstract

The invention provides an asphalt mixture fatigue performance test device and method, the asphalt mixture fatigue performance test device and method are applied to fatigue performance test of a test piece, the test piece is arc-shaped or annular, and the device comprises an environmental box, a test mechanism, a power assembly and an image acquisition device; a test cavity is arranged in the environment box, and a plurality of supporting wheels are arranged in the test cavity; the test mechanism comprises a rotating part and a plurality of load applying assemblies, the rotating part is rotationally arranged in the test cavity, and each load applying assembly comprises a radial pressure applying module, a fixed support and two test wheels. Compared with the prior art, the asphalt mixture fatigue performance testing device has the advantages that the uniformly or non-uniformly arranged load applying assemblies repeatedly rotate and act on the inner surface of the annular or arc-shaped testing piece, the moving working condition of a vehicle tire can be simulated, the testing piece is simple to prepare, and the testing efficiency is high. Test environments with different temperatures can be provided for two test pieces made of different materials, different test requirements can be met, and the test efficiency can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of material performance testing, and particularly relates to a fatigue performance test device and method for asphalt mixture. BACKGROUND

[0002] Asphalt mixture is a mixture of mineral aggregate and asphalt binder. Asphalt mixture is a composite material mainly composed of asphalt, coarse aggregate, fine aggregate, and mineral powder, and some also contain polymers and wood cellulose. Different structures are formed by mixing materials of different qualities and quantities, and different mechanical properties are obtained.

[0003] The fatigue performance of asphalt mixture is a core indicator for evaluating the long-term durability of pavement. The four-point bending fatigue test is widely adopted as an industry standard method for asphalt mixture fatigue testing due to its uniform stress distribution. In this method, the beam-shaped test piece is placed between two fixed support points and two load application points. A hydraulic servo system applies a reciprocating sinusoidal load at the two load application points. The number of cycles to failure is measured to determine the fatigue life.

[0004] However, in this method, the load is always applied to the middle fixed position of the test piece, while the real pavement bears dynamic loads generated by moving wheels. The difference between the moving load mode and the simplified fixed position load mode leads to a mismatch between the stress path inside the tested material and the actual situation, which cannot reflect the real mechanism of cumulative damage of asphalt layer under the action of vehicle tire load. Moreover, in the traditional four-point bending fatigue performance test, the load peak value used in a single test is a fixed value, which cannot simulate the working conditions of asphalt pavement under the action of different levels of vehicle tire load in continuous time. SUMMARY

[0005] The present application aims to overcome the shortcomings and deficiencies in the prior art and provide a fatigue performance test device and method for asphalt mixture.

[0006] One embodiment of the present application provides a fatigue performance test device for asphalt mixture, which is applied to fatigue performance test of a test piece. The test piece has an arc or ring shape and comprises:

[0007] An environmental box is provided with a test cavity, and a plurality of support wheels are arranged in the test cavity.

[0008] The test mechanism comprises a rotating member and a plurality of load applying assemblies, the rotating member is rotatably arranged in the test cavity, the load applying assembly comprises a radial pressure module, a fixed bracket and two test wheels, a plurality of radial pressure modules are arranged on the rotating member and are arranged in sequence around the rotating member, the radial pressure module is correspondingly connected to the fixed bracket, the fixed bracket can move along the radial direction of the rotation axis of the rotating member under the drive of the radial pressure module, the two test wheels are arranged in sequence on the fixed bracket along the rotation direction of the rotating member, and the two test wheels are rotatably matched with the fixed bracket; a plurality of support wheels are evenly arranged around the test mechanism, a test space for accommodating a test piece is provided between the support wheels and the test wheels, and the spacing between two adjacent test wheels is smaller than the spacing between two adjacent support wheels;

[0009] a power assembly, the power assembly being drivingly connected to the rotating member and configured to drive the rotating member to rotate;

[0010] An image acquisition device is arranged on one side of the environmental chamber and faces the inside of the environmental chamber, and is used to acquire a test image of the test piece.

[0011] In some optional embodiments, two support frames are detachably provided in the test cavity, respectively located on both sides of the test cavity, and the support frames extend into the test space;

[0012] When the test piece is in an arc shape, both ends of the test piece are connected to the two support frames respectively, and a portion of the test piece extends into the test space for accommodating the test piece.

[0013] In some optional embodiments, a flexible supporting layer is formed on the outer circumference of the support wheel.

[0014] In some optional embodiments, fixed slots are provided on both sides of the fixed bracket, the radial pressure module is located between the fixed slots on both sides of the fixed bracket, and part of the test wheel is provided in the fixed slot and rotatably cooperates with the fixed slot.

[0015] In some optional embodiments, the asphalt mixture fatigue performance testing device also includes an upper temperature regulating device and a lower temperature regulating device, the support frame is a supporting partition, and the supporting partition divides the test chamber into an upper chamber and a lower chamber. The upper temperature regulating device is arranged on the environmental box and is connected to the upper chamber for regulating the temperature inside the upper chamber. The lower temperature regulating device is arranged under the environmental box and is connected to the lower chamber for regulating the temperature inside the lower chamber.

[0016] In some alternative embodiments, the radial pressing module comprises a hydraulic cylinder arranged on the rotating member, an output shaft of the hydraulic cylinder is connected with the fixed support, and a hydraulic control valve and a hydraulic gauge are arranged on the hydraulic cylinder.

[0017] In some alternative embodiments, the environmental box is provided with an opening and a box door, a sealing member is arranged at the opening or the box door, the sealing member is arranged around the opening, the box door is movably connected with the environmental box and can open and close the opening, and when the box door closes the opening, the box door presses the sealing member against the environmental box.

[0018] In some alternative embodiments, the power assembly comprises a motor and a gear transmission module, and an output shaft of the motor is drivingly connected with the rotating member through the gear transmission module.

[0019] Another embodiment of the present application provides a test method for the fatigue performance of asphalt mixture, which is applied to the test device for the fatigue performance of asphalt mixture as described above and comprises the following steps of:

[0020] The test piece is placed in the test cavity, arranged along the direction of the load applying assembly and located in the test space between the support wheels and the test wheel.

[0021] The radial pressing module drives the fixed support to move towards the test piece so that the test wheel presses against the test piece and the test wheel applies the preset load to the test piece.

[0022] The power assembly drives the rotating member to rotate so that the entire load applying assembly rotates and the test wheel rolls along the test piece, the middle points of the test piece located between any two adjacent support wheels are selected as observation points, the number of rotations of the rotating member and the change of the outer contour line of the test piece around the observation points are recorded until the test piece is damaged due to fatigue.

[0023] The fatigue life of the asphalt mixture is determined based on the preset load, the number of rotations of the rotating member and the change of the outer contour line of the test piece around the observation points.

[0024] In some alternative embodiments, when the test piece is in an arc shape,

[0025] The step of placing the test piece in the test cavity, arranging the test piece along the direction of the load applying assembly and locating the test piece in the test space between the support wheels and the test wheel comprises the following steps of:

[0026] The two test pieces are placed in the test cavity, arranged along the direction of the load applying assembly and located in the test space between the support wheels and the test wheel, and the two test pieces are made of different materials.

[0027] In the asphalt mixture fatigue performance test device of the present application, the load applying assembly can be arranged uniformly or non-uniformly to apply repeated rotation to the inner surface of the ring-shaped or arc-shaped test piece, so as to simulate the moving condition of the vehicle tire.

[0028] The load applied to the test piece by the different load applying assemblies can be the same or different, so that the load peak of the different load applying assemblies can be different, thereby forming a random and complex load condition, which is more in line with the actual use condition.

[0029] In addition, the test piece is simple to prepare. Since the cylindrical workpiece is simple to produce, the ring-shaped test piece can be obtained after the cylindrical workpiece is turned, without the need to roll and form a thick plate test piece. The arc-shaped test piece can be obtained by cutting the ring-shaped test piece along the radial direction, which is simple to prepare.

[0030] The support wheel can adopt a flexible support layer, which is beneficial to simulate the flexible base layer (such as granular material, asphalt stabilized macadam) or semi-rigid base layer laid at the bottom of the real pavement asphalt layer, so as to be more in line with the real condition and avoid the rigid support structure from restricting the deformation freedom of the bottom of the test piece, thereby causing the stress response to be distorted.

[0031] The arc-shaped test piece only needs to cut the ring-shaped test piece in half. Two arc-shaped test pieces of different asphalt mixtures are prepared, and then the arc-shaped test pieces of the two different materials can be tested at the same time, thereby accelerating the test efficiency. In addition, the test environment of different temperatures can be provided for the two test pieces of different materials, so as to meet different test needs.

[0032] In order to enable a clearer understanding of the present application, the specific embodiments of the present application will be described below in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 The figure is a structural schematic view of the asphalt mixture fatigue performance test device of one embodiment of the present application.

[0034] Figure 2 The figure is a sectional view of the asphalt mixture fatigue performance test device of one embodiment of the present application.

[0035] Figure 3 The figure is a sectional view of the asphalt mixture fatigue performance test device and the test piece of one embodiment of the present application.

[0036] Figure 4 The figure is a structural schematic view of the load applying assembly of one embodiment of the present application when the test wheel is hidden.

[0037] Figure 5 The figure is an exploded view of part of the environmental box of one embodiment of the present application.

[0038] Figure 6 An exploded view of a support wheel and a distribution fixing rod according to an embodiment of the present invention;

[0039] Figure 7 FIG1 is a diagram illustrating the installation process of a curved test piece according to an embodiment of the present invention;

[0040] Figure 8 A schematic structural diagram of one side of a curved test piece according to one embodiment;

[0041] Figure 9 A broken view of an asphalt mixture fatigue performance testing device and a test piece during testing according to one embodiment of the present invention;

[0042] Figure 10 Each load applying assembly according to an embodiment of the present invention applies a load F to the test piece. i and Δt relationship diagram;

[0043] Figure 11 This is a diagram of a four-point bending fatigue test model obtained by converting partial models of two adjacent support wheels and two test wheels on the left and right sides of observation point A during a test of one embodiment of the present invention;

[0044] Figure 12 A cross-sectional view of a test piece near observation point A during a test of an embodiment of the present invention;

[0045] Figure 13 FIG. 4 is a relationship diagram between the strain ε(t) and t at observation point A according to an embodiment of the present invention.

[0046] Description of reference numerals:

[0047] 10. Environmental chamber; 11. Test chamber; 12. Support wheel; 121. Flexible support layer; 13. Support frame; 14. Bearing; 15. Opening; 16. Chamber door; 17. Seal; 18. Distribution fixing rod; 20. Test mechanism; 21. Rotating part; 211. Power transmission shaft; 212. Polygonal component; 22. Load application assembly; 221. Radial pressure module; 2211. Hydraulic control valve; 2212. Hydraulic gauge; 222. Fixed bracket; 2221. Fixed slot; 223. Test wheel; 30. Power assembly; 31. Motor; 32. Gear transmission module; 40. Image acquisition device; 50. Upper temperature regulation device; 51. Lower temperature regulation device; 60. Test piece. DETAILED DESCRIPTION

[0048] With reference to the accompanying drawings, the technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of the present application. In the description of the present application, unless otherwise specified, the meaning of "multiple" is 2 or more than 2, and the meaning of "several" is 1 or more than 1. In addition, unless otherwise specified, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features.

[0049] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "straight", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, which are only for the convenience of describing the present application and simplifying the description, and cannot be understood as indicating or implying that the devices or elements indicated must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0050] In the description of the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connecting", "fixing" should be understood broadly, for example, can be fixed connection, or can be detachable connection, or can be integrated; can be mechanical connection, or can be electrical connection; can be directly connected, or can be indirectly connected through an intermediate medium; can be the internal communication of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0051] In the description of the present application, the description of the terms "one embodiment", "some optional embodiments" or "some optional embodiments" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0052] Please refer to Figures 1 to 3 An embodiment of the present application provides an asphalt mixture fatigue performance test device, which is applied to fatigue performance test of a test piece 60. The test piece 60 is arc-shaped or ring-shaped, and comprises:

[0053] An environmental box 10 is provided with a test cavity 11, and a plurality of support wheels 12 are arranged in the test cavity 11;

[0054] A test mechanism 20 is arranged in the test cavity 11 and includes a rotating member 21 and a plurality of load applying assemblies 22. The load applying assemblies 22 each include a radial pressing module 221, a fixed support 222, and two test wheels 223. The radial pressing modules 221 are arranged on the rotating member 21 in sequence around the rotating member 21. The two adjacent load applying assemblies 22 can have the same or different spacing. The radial pressing module 221 is connected to the fixed support 222, and the fixed support 222 is movable along the radial direction of the rotating axis of the rotating member 21 under the drive of the radial pressing module 221. The two test wheels 223 are arranged on the fixed support 222 in sequence along the rotating direction of the rotating member 21, and the two test wheels 223 are rotationally connected to the fixed support 222. The support wheels 12 are arranged around the test mechanism 20 in a uniform manner, and the test space for accommodating the test piece 60 is formed between the support wheels 12 and the test wheels 223. The spacing between the two adjacent test wheels 223 is smaller than the spacing between the two adjacent support wheels 12.

[0055] A power assembly 30 is drivingly connected to the rotating member 21 for driving the rotating member 21 to rotate.

[0056] An image acquisition device 40 is arranged on one side of the environmental box 10 and faces the environmental box 10, and is used for acquiring the test image of the test piece 60. The environmental box 10 can be transparent, so as to facilitate the image acquisition device 40 to acquire the test image of the test piece 60. The profile change of the test piece 60 is determined by the test image.

[0057] The load applying assemblies 22 apply the load to the test piece 60 through the test wheels 223. The fixed support 222 is driven to move by the radial pressing module 221, and the test wheels 223 are pressed against the test piece 60 by the fixed support 222. Therefore, the size of the load applied to the test piece 60 by the test wheels 223 can be adjusted by adjusting the pressure applied to the fixed support 222 by the radial pressing module 221.

[0058] The test piece 60 can be annular or arc-shaped. When the test piece 60 is annular, the test piece 60 is arranged around the test mechanism 20, the test wheel 223 abuts the inner side of the test piece 60, and the support wheel 12 abuts the outer side of the test piece 60. When the test piece 60 is arc-shaped, in some optional embodiments, two support frames 13 are detachably arranged in the test cavity 11 and extend into the test space. When the test piece 60 is arc-shaped, the two ends of the test piece 60 are connected to the two support frames 13 respectively, and part of the test piece 60 extends into the test space for accommodating the test piece 60. At this time, two test pieces 60 can be arranged, and the two test pieces 60 are arranged above and below the support frames 13 respectively. The two ends of the upper test piece 60 are connected to the top of the support frames 13 respectively, and the two ends of the lower test piece 60 are connected to the bottom of the support frames 13 respectively. In this way, the two test pieces 60 can be tested at the same time, and the asphalt mixtures prepared by the two test pieces 60 can be different, so that the fatigue performance of two kinds of asphalt mixtures can be tested at the same time.

[0059] The support frame 13 can be mounted on the environmental box 10 by screws or other structures, so that the support frame 13 can be removed when the test piece 60 is annular. The ends of the test piece 60 can be adhered to the support frame 13 by water-based epoxy or other adhesive materials, so as to fix the test piece 60. Other suitable fixing structures can also be used for installation and fixation, which are not limited to this example.

[0060] The real pavement asphalt layer is laid on the flexible base layer (such as granular material, asphalt stabilized macadam) or semi-rigid base layer. The flexible base layer will deform elastically under load, so the rigid support restricts the deformation freedom of the test piece 60, resulting in distortion of the stress response. Therefore, in some optional embodiments, a flexible support layer 121 is formed on the outer periphery of the support wheel 12, which simulates the flexible base layer of the real pavement, thereby facilitating the simulation of the actual pavement condition and improving the accuracy of the test.

[0061] Please refer to Figure 4 In some optional embodiments, the two sides of the fixed bracket 222 are provided with fixed clamping grooves 2221, the radial pressing module 221 is located between the fixed clamping grooves 2221 on the two sides of the fixed bracket 222, part of the test wheel 223 is arranged in the fixed clamping grooves 2221 and rotationally matched with the fixed clamping grooves 2221, thereby improving the fixing stability of the test wheel 223. In the embodiment, the test wheel 223 is rotationally connected to the fixed clamping grooves 2221 through the rotating shaft, so as to be rotationally arranged in the fixed clamping grooves 2221.

[0062] The rotating member 21 can adopt a power transmission shaft 211 and a polygonal component 212, the power assembly 30 is connected with the polygonal component 212 through the power transmission shaft 211, and the outer circumferential surface of the polygonal component 212 is provided with a plurality of side planes, each of which can be provided with a radial pressure die set 221, and the planes facilitate the installation of the polygonal component 212. In order to improve the stability of the power transmission shaft 211, the environmental box 10 is further provided with a bearing 14, and the power transmission shaft 211 penetrates the bearing 14.

[0063] In some optional embodiments, the asphalt mixture fatigue performance test device further comprises an upper temperature adjusting device 50 and a lower temperature adjusting device 51, the support frame 13 is a support partition plate, the support partition plate divides the test cavity 11 into an upper cavity and a lower cavity, the upper temperature adjusting device 50 is arranged on the environmental box 10 and communicates with the upper cavity, and is used for adjusting the temperature inside the upper cavity. The lower temperature adjusting device 51 is arranged below the environmental box 10 and communicates with the lower cavity, and is used for adjusting the temperature inside the lower cavity. The two arc-shaped test pieces 60 are arranged in the upper cavity and the lower cavity respectively, the two ends of the test piece 60 located in the upper cavity are connected with the top of the two support frames 13 respectively, and the two ends of the test piece 60 located in the lower cavity are connected with the bottom of the two support frames 13 respectively. After the test piece 60 is installed, since the support partition plate and the test piece can cooperate to block the gas flow between the upper cavity and the lower cavity, the gas flow between the left and right of the upper cavity and the lower cavity is achieved. The upper temperature adjusting device 50 is above the test piece, and the lower temperature adjusting device 50 is below the test piece. The gas in the upper cavity above the test piece 50 cannot reach the lower part of the test piece in the lower cavity, so the heat exchange speed of the upper cavity and the lower cavity is relatively slow. As long as the power of the upper temperature adjusting device 50 and the lower temperature adjusting device 51 is sufficient, the upper cavity and the lower cavity can be kept at different temperatures respectively, so that the fatigue performance test of the two test pieces 60 under different temperature environments at the same time can be met. The upper temperature adjusting device 50 and the lower temperature adjusting device 51 can all adopt air conditioning equipment, which is not limited to this example.

[0064] In some optional embodiments, the radial pressure die set 221 comprises a hydraulic cylinder, the hydraulic cylinder is arranged on the rotating member 21, the output shaft of the hydraulic cylinder is connected with the fixed support 222, the hydraulic cylinder is provided with a hydraulic control valve 2211 and a hydraulic gauge 2212, the load applied by the output shaft of the hydraulic cylinder to the fixed support 222 is adjusted through the hydraulic control valve 2211, and the current load applied by the output shaft of the hydraulic cylinder to the fixed support 222 is observed through the hydraulic gauge 2212. Of course, the radial pressure die set 221 can also adopt other suitable structures, such as a gas cylinder or other structures.

[0065] Please refer to Figure 5In some optional embodiments, the environmental box 10 is provided with an opening 15 and a box door 16, and a sealing member 17 is arranged at the opening 15 or the box door 16. The sealing member 17 is arranged around the opening 15, and the box door 16 is movably connected to the environmental box 10 and can open and close the opening 15. When the opening 15 is opened by the box door 16, the test piece 60 is conveniently loaded. When the opening 15 is closed by the box door 16, the box door 16 presses the sealing member 17 against the environmental box 10, thereby improving the sealing performance of the test cavity 11. The box door 16 can be rotatably connected to the environmental box 10 by a hinge.

[0066] In some optional embodiments, the power assembly 30 comprises a motor 31 and a gear transmission module 32. The output shaft of the motor 31 is drivingly connected to the rotating member 21 through the gear transmission module 32. The motor 31 drives the power transmission shaft 211 of the rotating member 21 to rotate through the gear transmission module 32.

[0067] For the asphalt mixture fatigue performance test device, another embodiment of the present application provides an asphalt mixture fatigue performance test method applied to the asphalt mixture fatigue performance test device. The method comprises the following steps:

[0068] S1: The test piece 60 is placed in the test cavity 11, and the test piece 60 is arranged along the direction of the load applying assembly 22 and is located in the test space between the support wheel 12 and the test wheel 223. In this embodiment, two arc-shaped test pieces 60 are taken as an example for description. When the test piece 60 is arc-shaped, two test pieces 60 are placed in the test cavity 11, and the two test pieces 60 are arranged along the direction of the load applying assembly 22 and are located in the test space between the support wheel 12 and the test wheel 223.

[0069] Please refer to Figure 6 and Figure 7 In addition, in this embodiment, a plurality of distribution fixing rods 18 are arranged in the environmental box 10, and the support wheel 12 is rotatably arranged on the fixing rod and is locked by a fixing screw, so that the support wheel 12 is detachably mounted on the fixing rod, and the test piece 60 is conveniently mounted. Taking the installation of two arc-shaped test pieces 60 as an example, the corresponding support wheel 12 is first detached from the fixing rod, then one of the arc-shaped test pieces 60 is mounted on the support frame 13, and then the support wheel 12 is mounted on the fixing rod. The other arc-shaped test piece 60 is also mounted in the above-mentioned manner.

[0070] S2: Then, the temperature of the upper cavity and the lower cavity is adjusted by the upper temperature adjusting device 50 and the lower temperature adjusting device 51, so that the upper cavity reaches a first set temperature and the lower cavity reaches a second set temperature. The first set temperature and the second set temperature can be the same or different.

[0071] S3: The radial pressure module 221 moves the fixed support towards the test piece 60 to make the test wheel 223 press against the test piece 60 and apply a preset load on the test piece 60 through the test wheel 223. It should be noted that the pressure applied by different radial pressure modules 221 on the corresponding fixed supports can be different or the same, and thus the load applied by the test wheel 223 of the different load applying assembly 22 on the test piece 60 can also be different, so as to simulate different traffic load conditions and improve the accuracy of the test.

[0072] Referring to Figure 8 and Figure 9 , the radius of the inner contour of the test piece 60 is R1, the radius of the outer contour of the test piece 60 is R2, the width of the test piece 60 is h, the thickness of the test piece 60 is d, and the included angle between two adjacent load applying assemblies is θ, then the inner side arc length l of the corresponding arc-shaped test piece 60 is:

[0073]

[0074] The linear speed of the load applying assembly is ωR1, where ω is the rotational speed of the rotating member. Then the time interval Δt of the adjacent two load applying assemblies passing through the same point on the inner side of the test piece 60 can be calculated:

[0075]

[0076] Referring to Figure 10 , the middle point of the test piece 60 between any two adjacent support wheels is selected as the observation point, and the load F i applied by the test wheel of each load applying assembly on the inner side of the observation point of the test piece 60 changes as shown in the figure.

[0077] S4: The power assembly drives the rotating member to rotate to make the entire load applying assembly rotate, and the test wheel rolls along the test piece 60. Referring to Figure 11 , when rolling, the part between the left and right two adjacent support wheels of the observation point A can be modeled as a four-point bending fatigue test model, and the two support wheels are approximately two support points of the traditional four-point bending fatigue test, and the two test wheels in contact with the inner side of the test piece 60 are approximately two load applying points of the traditional four-point bending fatigue performance test. The distance between the centers of the two support wheels is L, the distance between the centers of the two test wheels is a, and the load applied by the test wheel on the test piece 60 is F i , where i is the number of the load applying assembly, i = 1, 2, 3, 4, 5,..., and the maximum value of i is equal to the number of the load applying assembly.

[0078] The maximum tensile stress of the observation point A in the model four-point bending fatigue performance test is:

[0079]

[0080] The stiffness modulus of the asphalt mixture is:

[0081]

[0082] The applied load mode of the asphalt mixture fatigue performance test is a constant stress level mode. During the application of the load, the stress level of the test wheel of each load application assembly applied to the test piece 60 is taken as SR = 0.2 ~ 0.7σ according to engineering experience. max Randomly determined, the load applied by each load application assembly through the test wheel is kept unchanged after setting, forming a group of load application assemblies with the same or different load peak levels. The load applied by each load application assembly in the group to the test piece 60 through the test wheel can be the same or different. Since the angular velocity, radius and linear velocity of the load application assembly are the same, the time of each load application assembly acting on the observation point A is very short and the same, so the frequency of the half-sine moving load formed by each load application assembly is the same.

[0083] S5: Record the number of rotations of the rotating member and the change of the outer contour line of the test piece 60 around the observation point, until the test piece 60 reaches fatigue failure.

[0084] The change of the outer contour line of the test piece 60 around the observation point can determine the stiffness modulus, and the asphalt mixture can be judged to reach fatigue failure by the stiffness modulus or whether there is a macroscopic observation of fracture of the test piece 60. Among them, the change of the outer contour line of the test piece 60 around the observation point is mainly realized by the image acquisition device. The image acquisition device obtains the test image of the test piece 60 near the observation point A, observes the displacement change D(t) of the observation point A and calculates the strain change ε(t) of the observation point A;

[0085] The determination method of D(t) is as follows: Figure 12 The dashed line in the figure is the outer contour line of the test piece 60 in the test image collected in the initial state. The outer contour line of the test line in the initial state is marked as the reference line, and then the current image of the test piece 60 at each unit time t after the load is obtained. Based on the current image, the current outer contour line of the test piece 60 is calculated, and the deviation between the current outer contour line of the observation point A at each unit time t and the reference line is calculated, which is denoted as D(t). The length of the unit time t is less than the length of one rotation of the rotating member.

[0086] Please refer to Figure 13The determination of ε(t) is as follows: according to the relationship between displacement and strain, the strain ε(t) of point A at any time is obtained as D(t) / d.

[0087] Wherein, one rotation of the rotating member represents that all load applying assemblies pass through the observation point A once, i.e. all test wheels of the load applying assemblies pass through the observation point A once, and one rotation of the rotating member is regarded as one load cycle. When the 50th load cycle is loaded, D 50 When the ith load cycle is loaded, D i The D i of any load cycle is equal to the average value of all D(t) in the time period corresponding to the load cycle.

[0088] The calculation method of the initial stiffness modulus is as follows:

[0089]

[0090] The stiffness modulus of the ith load cycle is as follows:

[0091]

[0092] The stiffness modulus ratio is as follows:

[0093]

[0094] When Damage≥50% or macroscopic fracture of the test piece 60 occurs, it is considered that the asphalt mixture reaches fatigue failure, and the number of load cycles and / or the length of load cycles at this time are recorded, and are recorded as one fatigue performance test is completed.

[0095] S6: Based on the preset load, the number of rotations of the rotating member, and the change of the outer contour line of the test piece 60 around the observation point, the fatigue life of the asphalt mixture is determined. The specific fatigue life calculation method needs to be adjusted according to whether the load applied by the load applying assembly is the same.

[0096] (1) When the load applied by the load applying assembly is the same, i.e. under the repeated cyclic load of multiple observation points A in a single fatigue performance test, the stress level acting on the observation point A is the same, i.e.

[0097] σ = σ i = σ j , i = 1, 2, 3, 4, 5,..., i≠j);

[0098] At this time, the fatigue life N f of the test piece 60 corresponding to the set stress level σ under multiple fatigue performance tests needs to be counted, i.e. the regression method can be used to obtain the fatigue life equation N f ~ Nf (σ). Fatigue life calculation method is a known technology, which will not be described here.

[0099] (2) When the load applied by the load applying assembly is not the same, i.e. under the repeated cyclic load of multiple observation points A in a single fatigue performance test, the stress level acting on the observation point A is not the same, i.e.

[0100] σ i ≠σ j , i = 1, 2, 3, 4, 5,..., i≠j);

[0101] At this time, it is necessary to count the fatigue life N eq of the asphalt mixture corresponding to the set mixed stress level σ f in multiple fatigue performance tests. eq σ eq is the equivalent stress, σ i is calculated according to the following formula:

[0102]

[0103] Wherein, m is the number of load applying assemblies, σ i is the load applied by each load applying assembly to the test piece 60, δ i is the weight of each σ i .

[0104] According to the equivalent stress level σ eq under the mixed stress level in different fatigue tests and the corresponding fatigue life N f , the fatigue life equation N f ~ N f (σ eq ) of the asphalt mixture corresponding to the test piece 60 is obtained by using the regression method.

[0105] Although embodiments of the present application have been shown and described, it is to be understood that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An asphalt mixture fatigue performance test device, used for fatigue performance test of test pieces, wherein the shape of the test piece is arc or ring, characterized in that: include: An environmental chamber, wherein a test chamber is provided in the environmental chamber, and a plurality of support wheels are provided in the test chamber; The test mechanism comprises a rotating member and a plurality of load applying assemblies, the rotating member is rotatably arranged in the test cavity, the load applying assembly comprises a radial pressure module, a fixed bracket and two test wheels, a plurality of radial pressure modules are arranged on the rotating member and are arranged in sequence around the rotating member, the radial pressure module is correspondingly connected to the fixed bracket, the fixed bracket can move along the radial direction of the rotation axis of the rotating member under the drive of the radial pressure module, the two test wheels are arranged in sequence on the fixed bracket along the rotation direction of the rotating member, and the two test wheels are rotatably matched with the fixed bracket; a plurality of support wheels are evenly arranged around the test mechanism, a test space for accommodating a test piece is provided between the support wheels and the test wheels, and the spacing between two adjacent test wheels is smaller than the spacing between two adjacent support wheels; a power assembly, the power assembly being drivingly connected to the rotating member and configured to drive the rotating member to rotate; An image acquisition device is arranged on one side of the environmental chamber and faces the inside of the environmental chamber, and is used to acquire a test image of the test piece.

2. The asphalt mixture fatigue performance testing device according to claim 1, characterized in that: Two support frames are detachably provided in the test chamber and are located on both sides of the test chamber, and the support frames extend into the test space; When the test piece is in an arc shape, both ends of the test piece are connected to the two support frames respectively, and a portion of the test piece extends into the test space for accommodating the test piece.

3. The asphalt mixture fatigue performance testing device according to claim 1, characterized in that: A flexible supporting layer is formed on the outer peripheral surface of the supporting wheel.

4. The asphalt mixture fatigue performance testing device according to claim 1, characterized in that: Both sides of the fixing bracket are provided with fixing slots, the radial pressure module is located between the fixing slots on both sides of the fixing bracket, and part of the test wheel is arranged in the fixing slots and rotatably cooperates with the fixing slots.

5. The asphalt mixture fatigue performance testing device according to claim 2, characterized in that: It also includes an upper temperature regulating device and a lower temperature regulating device. The support frame is a supporting partition, and the supporting partition divides the test chamber into an upper chamber and a lower chamber. The upper temperature regulating device is arranged on the environmental box and is connected to the upper chamber for regulating the temperature inside the upper chamber. The lower temperature regulating device is arranged under the environmental box and is connected to the lower chamber for regulating the temperature inside the lower chamber.

6. The asphalt mixture fatigue performance testing device according to claim 1, characterized in that: The radial pressure module includes a hydraulic cylinder, which is arranged on the rotating member. The output shaft of the hydraulic cylinder is connected to the fixed bracket. The hydraulic cylinder is provided with a hydraulic control valve and a hydraulic gauge.

7. The asphalt mixture fatigue performance testing device according to any one of claims 1 to 6, characterized in that: The environmental chamber is provided with an opening and a door, and a sealing member is provided at the opening or the door. The sealing member is arranged around the opening. The door is movably connected to the environmental chamber and can open and close the opening. When the door closes the opening, the door presses the sealing member against the environmental chamber.

8. The asphalt mixture fatigue performance testing device according to any one of claims 1 to 6, characterized in that: The power assembly includes a motor and a gear transmission module, and the output shaft of the motor is drivingly connected to the rotating member through the gear transmission module.

9. A method for testing fatigue performance of asphalt mixture, applied to an asphalt mixture fatigue performance testing device as claimed in any one of claims 1 to 8, characterized in that: include: Place the test piece into the test chamber, arrange the test piece in a direction surrounding the load application assembly, and place the test piece in the test space between the support wheel and the test wheel; The radial pressure module drives the fixed bracket to move toward the test piece so that the test wheel presses against the test piece and applies a preset load to the test piece through the test wheel; The power assembly rotates the rotating member to rotate the entire load application assembly, and the test wheel rolls along the test piece. The midpoint between any two adjacent support wheels on the test piece is selected as the observation point. The number of revolutions of the rotating member and the change in the outer contour of the test piece around the observation point are recorded until the test piece reaches fatigue failure. The fatigue life of the asphalt mixture is determined based on the preset load, the number of revolutions of the rotating part and the change of the outer contour line of the test piece around the observation point.

10. The asphalt mixture fatigue performance test method according to claim 9, characterized in that: When the test piece is in an arc shape; The step of placing the test piece into the test chamber, arranging the test piece in a direction surrounding the load applying assembly, and placing the test piece in the test space between the support wheel and the test wheel includes: Two test pieces are placed in the test chamber. The two test pieces are arranged in a direction surrounding the load applying assembly and are located in the test space between the support wheel and the test wheel. The two test pieces are made of different materials.

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