Universal testing machine-based torsional shear test device for asphalt mixture under normal stress

Abstract

The utility model discloses an asphalt mixture normal stress torsion shear test device based on a universal testing machine, which comprises a mounting seat, a motor, a digital display torque meter, a lower torsion shear disc, an upper torsion shear disc and a pressure sensor, and the mounting seat is used for being arranged on the universal testing machine; the motor is arranged on the mounting seat; the digital display torque meter is arranged on an output shaft of the motor; the lower torsional shear disc is arranged on the digital display torque meter, and the pressure sensor is arranged on the lower torsional shear disc; the upper torsional shear disc is used for being arranged on a pressure head of a universal testing machine, a distance is reserved between the upper torsional shear disc and the lower torsional shear disc so that an asphalt mixture test piece can be arranged, and when the asphalt mixture test piece is arranged, the asphalt mixture test piece is in surface contact with the upper torsional shear disc and the lower torsional shear disc; the lower torsional shear disc can be driven to rotate so as to apply torque to the asphalt mixture test piece. According to the utility model, the problem of stress concentration can be avoided, and the stress condition of the pavement layer in the actual use process can be more accurately simulated.

Description

Technical Field

[0001] The utility model belongs to the field of asphalt material test research, and particularly relates to a torsional shear test device for asphalt mixture under normal stress based on a universal testing machine. Background Technique

[0002] Under the long-term action of vehicle loads, especially in high-temperature environments, insufficient shear resistance of asphalt mixtures may lead to the occurrence of rutting diseases in asphalt pavements. Rutting is mainly manifested as settlement and lateral heaving at the wheel tracks on the surface of the pavement layer, which is particularly obvious in summer high temperatures.

[0003] For long-span steel bridge deck pavements, the stresses, temperature changes, and environmental factors they face during actual use may be more complex. The steel bridge deck pavement not only bears the direct action of vehicle loads but is also affected by various environmental factors such as expansion and contraction caused by temperature changes, wind loads, and rain erosion. These complex stress conditions result in a large difference between the stress distribution in actual use and that under indoor test conditions. Therefore, the test results may not fully reflect the actual situation during actual use.

[0004] Currently, there is no unified standard method for shear resistance test methods in China. Existing test methods have some defects, which make the test results unable to truly simulate the actual stress conditions of the road surface. For example, some test methods may not fully consider the performance changes of asphalt mixtures in high-temperature environments or may not simulate the actual distribution of vehicle loads on steel bridge decks. These factors all affect the accuracy and reliability of the test results.

[0005] To more truly simulate the actual stress conditions of the road surface, it is necessary to improve and perfect the existing test methods. This includes developing test equipment that can simulate complex stress states, formulating more stringent test standards and methods, and considering the influence of actual environmental factors on test results. Through these improvements, the authenticity and reliability of test results can be improved, providing a more accurate basis for the design and maintenance of steel bridge deck pavements.

[0006] In the Technical Specification for the Design and Construction of Highway Steel Bridge Deck Pavement, the 45° inclined shear method is adopted for the shear test method. This test method is achieved by the mutual cooperation of a compression testing machine and a special asphalt mixture fixture. When the testing machine applies an axial pressure to the asphalt mixture, the mixture undergoes shear failure along the inclined section. The inclined shear test device changes the shear angle only indirectly reflects the changes in compressive and shear stresses, and the compressive and shear stresses cannot vary independently and there is stress concentration at the contact part, so there are certain limitations. Moreover, in this test method, there are problems such as excessive deformation of the compression-shear mixture during operation, which affects the stability of the loading shear surface and shear propulsion obstacles. Especially for modified asphalt mixtures, they have low strength and large deformation under high-temperature conditions, and the test operation has problems of low controllability and large variability. At the same time, the normal pressure in the inclined plane shear test is a component of the vertical pressure, and the normal pressure changes with the vertical force, which is not conducive to the control of balance and stability.

[0007] As a test method for studying the shear resistance performance of mixtures, the triaxial compression test has been relatively mature in theory development and has once received extensive attention from scholars at home and abroad. China has also made detailed descriptions of the test conditions and methods in the test regulations. However, this method also has obvious deficiencies. First, since the lateral pressure borne by the asphalt mixture on the road surface cannot be accurately measured, the confining pressure used in the test cannot accurately reflect the actual stress state of the road surface. Second, this test method is developed and introduced from soil mechanics tests, but in fact, the material characteristics of asphalt mixtures are different from the material parameters and test condition assumptions in soil mechanics. Finally, the triaxial compression test instrument is expensive and the operation is relatively complex, so it is less used in engineering.

[0008] The direct shear test of asphalt mixture, compared with the triaxial compression test, has the characteristics of simple theory and easy to understand, and the operation is convenient, and the equipment is simple and practical. However, this method also has obvious defects: one is that the position where the material fails in the test is usually not the weakest part, resulting in a difference between the result and the actual road condition; the second is that the change in the failure surface area needs to be corrected and calculated; the third is that the granularity affects the accuracy. Therefore, although the direct shear test is convenient to operate and promote, the direct shear test is only suitable for initially determining the shear strength and is not suitable for accurately evaluating the shear performance.

[0009] Li Zuzhong et al. disclosed "A torsional shear test device for asphalt pavement materials and structures" in the Chinese invention open patent CN102297812A, which includes a machine base, a reaction frame arranged on the machine base, a worm and worm gear mechanism arranged at the bottom of the reaction frame, the worm input end of the worm and worm gear mechanism is connected to a pressure motor, the worm gear output end is connected to a lower support plate for clamping a specimen, and a pressure sensor is arranged on the lower support plate; a torque motor is arranged at the top of the reaction frame, the output shaft of the torque motor is sequentially connected with a disk torque sensor and an upper support plate for clamping the specimen downward, and clamping rings are respectively fixed on the upper and lower support plates, and rubber pads are arranged on the inner walls of the clamping rings. The method of clamping the specimen by using the clamping ring in the existing scheme has certain limitations. Due to the action of the clamping ring, the side surface of the specimen will be subjected to pressure, and this lateral pressure may cause uneven deformation of the specimen. This uneven deformation will not only affect the structural integrity of the specimen, but also may lead to deviation of the test results. In addition, the clamping ring clamping method may also cause stress concentration problems. Stress concentration will make the stress state of the specimen complex, thus having a great impact on the accuracy of the results during the mechanical test. On the other hand, rubber pads are used in the fixture of the existing scheme. Although the rubber pads can play a certain buffering role, when the test is carried out under high temperature conditions, the rubber may soften. This softening phenomenon may affect the stability of the specimen, and further affect the accuracy and reliability of the test results.

[0010] In summary, the existing asphalt mixture shear tests cannot meet the requirements. Utility Model Content

[0011] In order to solve at least one of the problems existing in the prior art, the present utility model provides a torsional shear test device for asphalt mixture under normal stress based on a universal testing machine, which can more conform to the actual stress condition between layers of a steel bridge deck pavement, can more accurately simulate the stress situation of the pavement during actual use, so as to more accurately evaluate the shear strength and fatigue performance of the pavement. Through the device of the present utility model, the on-site construction and maintenance work can be more effectively guided, the durability and service life of the steel bridge deck pavement can be improved, thereby ensuring traffic safety and smoothness.

[0012] To achieve the purpose of the present utility model, the torsional shear test device for asphalt mixture under normal stress based on a universal testing machine provided by the present utility model includes a mounting base, a motor, a digital display torque meter, a lower torsion shear disc, an upper torsion shear disc and a pressure sensor,

[0013] The mounting base is used to be arranged on a universal testing machine;

[0014] The motor is arranged on the mounting base;

[0015] The digital display torque meter is arranged on the output shaft of the motor;

[0016] The lower torsion shear disc is arranged on the digital display torque meter, and the pressure sensor is arranged on the lower torsion shear disc;

[0017] The upper torsion shear disc is used to be arranged on the pressure head of the universal testing machine, and the upper torsion shear disc is located above the lower torsion shear disc relatively. A distance is left between the upper torsion shear disc and the lower torsion shear disc to arrange the asphalt mixture specimen. When the asphalt mixture specimen is arranged, the asphalt mixture specimen is in surface contact with the upper torsion shear disc and the lower torsion shear disc. When the motor works, it can drive the lower torsion shear disc to rotate to apply torque to the asphalt mixture specimen.

[0018] Further, the pressure sensor is arranged on one side of the lower torsion shear disc opposite to the upper torsion shear disc.

[0019] Further, the mounting seat includes a bottom plate, a mounting plate and a top plate. The bottom plate is arranged on the universal testing machine, the mounting plate is arranged on the bottom plate, the top plate is located above the mounting plate, the bottom of the motor is located on the mounting plate, and the outer wall of the motor near one end of the output shaft is connected to the top plate.

[0020] Further, a sleeve is arranged at the bottom of the bottom plate, and the sleeve is connected to the universal testing machine through a pin.

[0021] Further, the bottom plate is pressed on the universal testing machine through bolts. The bolts can be disassembled. By tightening the bolts, the height can be adjusted so that the bolts contact the universal testing machine, and then by tightening further, the bottom plate can be firmly pressed on the universal testing machine. The bottom plate is stably pressed on the testing machine through the bolts.

[0022] Further, heat dissipation holes are arranged on the mounting plate.

[0023] Further, the top plate is connected to the bottom plate through connecting columns.

[0024] Further, the asphalt mixture specimen is fixedly adhered between the upper torsion shear disc and the lower torsion shear disc.

[0025] Further, the asphalt mixture specimen is fixedly adhered between the upper torsion shear disc and the lower torsion shear disc through AB glue. Using AB glue can firmly bond the asphalt mixture specimen to the upper torsion shear disc and the lower torsion shear disc.

[0026] Compared with the prior art, the utility model has at least the following beneficial effects:

[0027] (1) For the device provided by the utility model, when conducting the test, the upper torsion shear disc and the lower torsion shear disc are in surface contact with the asphalt mixture specimen. This contact method can distribute the force more evenly, thus avoiding the problem of stress concentration.

[0028] (2) In this utility model, the asphalt mixture specimen is firmly bonded between the upper torsion shear disc and the lower torsion shear disc, which not only ensures the stability of the asphalt mixture specimen but also avoids the specimen deformation or damage caused by excessive or uneven clamping force. Abandoning the traditional method of clamping and fixing with fixtures can avoid the stress concentration problems brought by the fixtures, especially at the edges or specific points of the asphalt mixture specimen, thus effectively avoiding excessive deformation. This method can not only improve the accuracy and reliability of the test but also simplify the test operation process and improve the test efficiency.

[0029] (3) Under the combined action of various factors such as vehicle loads and the environment, the steel bridge deck pavement is subjected to complex loads such as tensile stress, shear stress, and compressive stress, and the stress is relatively complex. The torsional shear test under normal stress can simulate the complex stress state experienced by the pavement when bearing vehicle loads. By changing the magnitude of the normal stress, the stress state of the pavement under different load conditions can be simulated, and adjusting the motor speed can simulate the influence of the vehicle traveling at different speeds on the pavement, which can more accurately simulate the stress situation of the pavement during actual use. Description of the Drawings

[0030] Figure 1 is a schematic structural diagram of the torsional shear test device for asphalt mixture under normal stress based on a universal testing machine provided by an embodiment of this utility model.

[0031] Figure 2 is a schematic structural diagram of the mounting seat in an embodiment of this utility model.

[0032] Figure 3 is a schematic installation diagram of the upper torsion shear disc in an embodiment of this utility model.

[0033] In the figure, the upper torsion shear disc 1, the asphalt mixture specimen 2, the lower torsion shear disc 3, the pressure sensor 4, the digital display torque meter 5, the top plate 6, the motor 7, the connecting column 8, the mounting plate 9, the bottom plate 10, the bolt 11, the sleeve 12. Detailed Embodiment

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present utility model clearer, the technical solutions in the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model. Apparently, the described embodiments are some, but not all, of the embodiments of the present utility model. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without creative efforts are within the scope of protection of the present utility model. During the daily use of the steel bridge deck pavement layer, due to the repeated action of vehicle loads and the influence of environmental factors, fatigue damage failures such as delamination, cracking, and rutting often occur. The existence of these problems will not only shorten the service life of the bridge, but also seriously affect the safety and efficiency of traffic passing if timely detection and maintenance are not carried out. At present, the tests on the shear strength and fatigue performance of the steel bridge deck pavement are mainly carried out in an indoor environment. Although this test method can provide certain data support, its limitations are obvious. Indoor tests often have difficulty simulating actual on-site construction conditions, including changes in temperature and humidity, and the actual distribution of vehicle loads. Therefore, it is not conducive to accurately evaluating the performance of the pavement layer during on-site construction. There are significant differences between the existing test evaluation methods and the stress conditions of the pavement layer during actual use. These methods often cannot accurately reflect the stress state of the pavement layer during actual use. In addition, these test methods are usually relatively complex, require professional equipment and personnel for operation, are difficult to control, time-consuming and laborious, and have high costs.

[0035] Please refer to Figures 1 to 3 , the torsional shear test device for asphalt mixture under normal stress based on a universal testing machine provided by the present utility model includes a mounting base, a motor 7, an upper torsional shear disc 1, a lower torsional shear disc 3, a digital display torque meter 5, and a pressure sensor 4.

[0036] The mounting base is fixed on the universal testing machine. The motor 7 is installed on the mounting base. The digital display torque meter 5 is set on the output shaft of the motor 7. The lower torsional shear disc 3 is set on the digital display torque meter 5 and the pressure sensor 4 is set on the lower torsional shear disc 3. The upper torsional shear disc 1 is set on the pressure head of the universal testing machine. The upper torsional shear disc 1 and the lower torsional shear disc 3 are arranged opposite to each other, and there is a position for arranging the asphalt mixture specimen 2 between the upper torsional shear disc 1 and the lower torsional shear disc 3. When the universal testing machine applies pressure, the pressure is transmitted to the asphalt mixture specimen 2 through the upper torsional shear disc 1, and the pressure sensor 4 detects the magnitude of the normal pressure of the asphalt mixture specimen 2. The lower torsional shear disc 3 is connected to the motor 7 through the digital display torque meter 5, and the torque value can be measured.

[0037] Put 5 digital torque meters on the shaft of the motor 7. The lower torsion shear disc 3 is arranged on the digital torque meter 5, and a pressure sensor 4 for detecting the magnitude of the normal pressure of the asphalt mixture specimen 2 is embedded in the lower torsion shear disc 3. The upper torsion shear disc 1 is fixed on the pressure head of the universal testing machine through a pin, and the asphalt mixture specimen 2 is fixedly pasted between the upper torsion shear disc 1 and the lower torsion shear disc 3. At the start of the test, turn on the power supply of the motor 7. The motor 7 rotates to apply torque to the asphalt mixture specimen 2 until the asphalt mixture specimen 2 is damaged, read the maximum torque of the digital torque meter 5, and analyze the shear resistance performance of the asphalt mixture through data analysis.

[0038] Shear propulsion refers to the ability of the shear plane to advance smoothly along a predetermined path during the shearing process. If the deformation is too large, it may cause the shear plane to fail to advance smoothly, forming an obstacle, thus affecting the shear efficiency and quality. The traditional straight-line propulsion shearing method may cause excessive deformation during the shearing process, which not only increases the irregularity of the shear plane but also increases the resistance during the shearing process. Excessive deformation will also lead to uneven stress distribution on the shear plane, forming stress concentration areas. These areas are prone to failure due to excessive stress, thus reducing the stability of the shear plane. To solve these problems, the device of the present utility model proposes a torsional shearing method, which does not require shear propulsion, but realizes shearing by simultaneously applying pressure and torque to the mixture specimen 2 through a universal testing machine and a motor 7. This can make the stress distributed inside the mixture specimen 2 more uniform, thereby improving the shear efficiency. The present utility model can change the magnitude of the pressure through the universal testing machine according to the test requirements, or adjust the rotation speed of the motor 6 (i.e., the loading rate), and can accurately control the pressure and the motor rotation speed. This composite loading method helps to reduce the local stress concentration that may be caused by a single loading method, thereby reducing the risk of excessive deformation.

[0039] In some embodiments of the present utility model, the motor base includes a bottom plate 10, a top plate 6 and a mounting plate 9. A sleeve 12 is provided at the bottom of the bottom plate 10, and a through hole is provided on the sleeve 12. The sleeve 12 is fixed on the universal testing machine through a pin. The top plate 6 is located above the bottom plate 10, the mounting plate 9 is arranged on the bottom plate 10, the bottom of the motor 7 is placed on the mounting plate 9, and the outer wall of the motor 7 at one end of the output shaft is fixedly connected to the top plate 6 through a bolt. A through hole is provided on the top plate 6, and the output shaft of the motor 7 passes through the through hole on the top plate 6 and is connected to the digital torque meter 5.

[0040] In some embodiments of the present utility model, the bottom plate 10 is square and is tightened and pressed on the universal testing machine by 4 bolts 11 at the end corners, thereby strengthening the installation stability of the entire device.

[0041] In some embodiments of the present utility model, heat dissipation holes are provided on the mounting plate 9 for dissipating heat from the motor 7, thereby ensuring the stable output power of the motor 7.

[0042] In some embodiments of the present utility model, the motor 7 is a reduction motor.

[0043] In some embodiments of the present utility model, the top plate 6 is connected to the bottom plate 10 through 4 connecting columns 8, thereby ensuring the stability of the motor 7. Preferably, the connecting columns 8 can be bolts.

[0044] In some embodiments of the present utility model, the cross-sections of the upper torsion shear disc 1 and the lower torsion shear disc 3 are both circular, that is, they are both discs.

[0045] The upper and lower end faces of the asphalt mixture specimen 2 are respectively pasted and fixed on the upper torsion shear disc and the lower torsion shear disc. The asphalt mixture specimen 2 is fixed by pasting instead of a fixture, which can avoid stress concentration in the specimen and improve the accuracy of the test results. At the same time, since the integrity of the specimen is better guaranteed, more accurate and stable test data can be obtained, providing a more reliable reference basis for the design and construction of the steel bridge deck pavement layer.

[0046] In some embodiments of the present utility model, the asphalt mixture specimen 2 is pasted and fixed between the upper torsion shear disc 1 and the lower torsion shear disc 3 by glue. Preferably, the glue can be epoxy resin glue or polyurethane glue.

[0047] The device provided in the foregoing embodiments of the present utility model can apply a normal stress to the asphalt mixture specimen 2 by using a universal testing machine. The magnitude of the normal stress can be set by the universal testing machine according to actual needs, and the magnitude and its loading rate can be precisely controlled, which can better simulate the actual road surface load pressure. At the same time, the asphalt mixture specimen 2 is subjected to torsional shear by the rotation of the motor shaft of the motor 7. The rotation speed of the motor 7 can also be adjusted by a frequency converter to adapt to different loading rate requirements. After the asphalt mixture specimen 2 is subjected to torsional shear, the reading of the maximum torque of the digital display torque meter 5 set on the motor shaft can be directly read out, which is the failure torque. Thus, the shear strength of the asphalt mixture can be calculated. The greater the failure torque, the stronger the shear strength of the asphalt mixture, and thus the shear performance of the asphalt mixture can be evaluated.

[0048] The shear strength can be calculated according to the following formula:

[0049]

[0050] In the formula, T max is the failure torque, which is the maximum torque value measured by the digital display torque meter during the shear process, R is the radius of the asphalt mixture specimen, I p is the polar moment of inertia, and σ is the normal stress.

[0051] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present utility model. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present utility model. Therefore, the present utility model will not be limited to the embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features disclosed herein.

Claims

1. The asphalt mixture torsion shear test device under normal stress based on a universal testing machine is characterized by: It includes a mounting base, a motor, a digital torque meter, a lower shear plate, an upper shear plate and a pressure sensor. The mounting base is used to be set on the universal testing machine; The motor is arranged on a mounting seat; The digital torque meter is set on the output shaft of the motor; The lower torsion shear plate is arranged on a digital torque meter, and the pressure sensor is arranged on the lower torsion shear plate; The upper torsion shear disc is used to be set on the pressure head of the universal testing machine, and the upper torsion shear disc is relatively located above the lower torsion shear disc. A distance is left between the upper torsion shear disc and the lower torsion shear disc to set the asphalt mixture specimen. When the asphalt mixture specimen is set, the asphalt mixture specimen is in surface contact with the upper torsion shear disc and the lower torsion shear disc. When the motor is working, it can drive the lower torsion shear disc to rotate to apply torque to the asphalt mixture specimen.

2. The asphalt mixture torsional shear test device under normal stress based on a universal testing machine according to claim 1 is characterized in that: The pressure sensor is arranged on a side of the lower torsion shear disc opposite to the upper torsion shear disc.

3. The asphalt mixture torsional shear test device under normal stress based on a universal testing machine according to claim 1, characterized in that: The mounting seat includes a bottom plate, a mounting plate and a top plate. The bottom plate is arranged on the universal testing machine, the mounting plate is arranged on the bottom plate, the top plate is located above the mounting plate, the bottom of the motor is located on the mounting plate, and the outer wall of the motor near one end of the output shaft is connected to the top plate.

4. The asphalt mixture torsional shear test device under normal stress based on a universal testing machine according to claim 3 is characterized in that: A sleeve is arranged at the bottom of the bottom plate, and the sleeve is connected with the universal testing machine through a latch.

5. The asphalt mixture torsional shear test device under normal stress based on a universal testing machine according to claim 3 is characterized in that: The bottom plate is pressed on the universal testing machine by bolts.

6. The asphalt mixture torsional shear test device under normal stress based on a universal testing machine according to claim 3 is characterized in that: The mounting plate is provided with heat dissipation holes.

7. The asphalt mixture torsional shear test device under normal stress based on a universal testing machine according to claim 3 is characterized in that: The top plate is connected to the bottom plate through connecting columns.

8. The asphalt mixture torsional shear test device under normal stress based on a universal testing machine according to claim 1, characterized in that: The motor is a reduction motor.

9. The asphalt mixture torsional shear test device under normal stress based on a universal testing machine according to any one of claims 1 to 8, characterized in that: The asphalt mixture specimen is fixed to the upper torsion shear disc and the lower torsion shear disc by bonding.

10. The asphalt mixture torsion shear test device under normal stress based on a universal testing machine according to claim 9, characterized in that the asphalt The mixture specimen is fixed between the upper torsion shear disk and the lower torsion shear disk by gluing with epoxy resin glue or polyurethane glue.

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