CN105784520A - Indoor programmable asphalt mixture fatigue simulation test device - Google Patents

Abstract

A programmable asphalt mixture indoor simulation fatigue test device, including a temperature simulation box, a base is arranged at the bottom of the temperature simulation box, an open thermal insulation water tank is arranged on the base, and an open thermal insulation water tank is arranged on the open thermal insulation water tank for placing asphalt The loading platform for the mixture sample is equipped with a hydraulic loading system for loading the asphalt mixture sample; the temperature simulation box is also equipped with a temperature cycle control system connected to the PLC. In the present invention, the test piece base fixing device is equipped with an open thermal insulation water tank to realize the simulation of the temperature gradient of the pavement structure, simulate the temperature field in the real pavement structure with the change of the space in the room, and fully consider the temperature load on the life of the pavement structure. and performance; the hydraulic loading system can accurately control the load imposed by the experimental wheel on the specimen, and at the same time simulate the impact of different axle loads on the pavement structure, and realize the indoor simulation of the impact of overloading and overweight on the life and performance of asphalt pavement.

Description

A programmable asphalt mixture indoor simulation fatigue test device

technical field

The invention belongs to the field of road pavement materials and design and manufacture thereof, and relates to an indoor simulated fatigue test device for asphalt mixture under the coupled action of load and temperature, in particular to a programmable asphalt mixture indoor simulated fatigue test device.

Background technique

Since the 1990s, with the sustained and rapid development of China's economy, the construction of expressways has also advanced rapidly. By the end of 2014, the total mileage of expressways in my country reached 111,900 kilometers, surpassing the United States and ranking first in the world. More than 90% of the highways that have been built use asphalt concrete pavement. In recent years, fatigue cracking in different degrees has occurred in both the asphalt pavement of ordinary roads and the asphalt pavement of expressways, and they have to be overhauled and rebuilt. Asphalt pavement Early fatigue cracking has become a worldwide problem.

Asphalt pavement is subjected to repeated wheel loads during use, and is in a state of overlapping stress and strain for a long time, resulting in a gradual decline in the structural strength of the pavement. When the load is repeated for more than a certain number of times, the stress generated in the pavement under the load will exceed the structural resistance after the strength drops, causing cracks on the pavement and fatigue fracture damage. The main fatigue testing methods can be divided into the following four categories:

(1) The first category is the fatigue test failure of the actual road surface under real vehicle loads, represented by the famous AASHTO test road in the United States;

(2) The second category is the fatigue test research of the full-scale pavement structure under the simulated vehicle load, including the loop test and the accelerated loading test, mainly including the loading equipment (ALF) of the Highway Research Institute of the Ministry of Communications of Australia and my country, and the South African National The Heavy Vehicle Simulation Vehicle (HVS) of the Road Research Institute, the outdoor large-scale loop test of Washington State University in the United States and the indoor large-scale loop test of the Chongqing Highway Research Institute;

(3) The third category is the test plate test method. It is mainly to simulate the role of the wheel on the road surface through the wheel track test to understand the form of crack generation and expansion.

(4) The fourth category is small-scale fatigue test research in the laboratory. First, the asphalt mixture is made into a test piece of a certain shape, and then the stress state of the asphalt pavement is simulated in a certain way to carry out the fatigue test.

The first three types of methods are expensive, take a long time, and are not widely developed. Therefore, the indoor small-scale fatigue test method with short period and low cost is widely used. Indoor small-scale fatigue tests often use simple bending tests, among which there are three test methods: midpoint loading or three-point loading, rotating cantilever beam and trapezoidal cantilever beam. In addition, there are splitting tests, elastic foundation beam bending tests, triaxial pressure tests, etc. Among them, the four-point bending fatigue life test has been included in the test regulations for asphalt and asphalt mixtures in highway engineering (JTGE20-2011). However, the existing indoor small-scale fatigue test method for indoor simulation of the fatigue performance of asphalt mixture can only simulate the effect of load on the asphalt mixture specimen at a constant temperature, and the temperature of each point in the entire specimen is the same as the temperature in the constant temperature box , while ignoring the change of outdoor ambient temperature with time and the influence of the existence of pavement temperature gradient on the fatigue performance of asphalt mixture, it is impossible to simulate the change of asphalt concrete pavement temperature with time and space, and it is impossible to simulate the unique temperature changes in different regions and the pavement The impact of structural temperature gradient on the fatigue performance of asphalt concrete pavement, and there is a big difference between the test process of the small beam specimen in the four-point bending fatigue life test and the actual asphalt pavement bearing the vehicle load. In addition, stress control and There is a big difference in the results of the fatigue test when the strain is controlled by two different loading modes, and there are problems of refinement, integration and low degree of automation.

The architectural structure placed in the natural environment is subject to the influence of various natural environment changes at any time, so that its overall temperature state is changing every moment. The so-called temperature field refers to the temperature of each point in the structure at each time point. The change of temperature with time and the existence of temperature gradient inside the material not only cause the deformation of the structure, but also cause large temperature stress. Domestic and foreign studies have shown that temperature stress has a great influence on the service life and mechanical properties of highway engineering, especially high-grade highway engineering. Therefore, it is necessary to improve the existing indoor simulation fatigue test device to realize the coupling effect of temperature stress and vehicle load.

Contents of the invention

The present invention aims to solve the shortcomings of the existing indoor simulators for testing and evaluating the fatigue performance of asphalt mixtures that the simulation of the real environment is insufficient, and the accuracy of the simulation test method is too low. A programmable asphalt mixture indoor simulation fatigue test device that is small in size and can be coupled with temperature and load at the same time.

To achieve the above object, the technical solution adopted in the present invention is:

A programmable asphalt mixture indoor simulation fatigue test device, including a temperature simulation box, the bottom of the temperature simulation box is provided with a base, the base is provided with an open thermal insulation water tank, and the open thermal insulation water tank is provided for The loading table for asphalt mixture samples is placed, and a hydraulic loading system for loading asphalt mixture samples is installed on the top of the loading table; a temperature cycle control system is also installed in the temperature simulation box, and the temperature cycle control system includes silicone oil. Low temperature circulation device, electric heating device, compressor and temperature sensor, silicone oil high and low temperature circulation device are connected with electric heating device, compressor and temperature sensor, compressor, electric heating device and temperature sensor are all connected with PLC set outside the temperature simulation box Connected, PLC is connected to a computer.

The hydraulic loading system includes a piston rod and a horizontally movable loading cylinder, the loading cylinder is connected to the piston rod, and the piston rod is vertically arranged, the lower end of the piston rod is provided with a pressure sensor, and the lower end of the pressure sensor is provided with a hinged wheel shaft. A loading wheel for loading the asphalt mixture sample is arranged on the supporting wheel shaft.

The hydraulic loading system also includes a driving motor, and the output shaft of the driving motor is connected with the hinged wheel shaft.

A track for the horizontal movement of the hydraulic loading system is arranged in the temperature simulation box, and the loading oil cylinder is arranged on the guide rail.

The base is a pull-out base; a circular hole is opened on the loading platform, and a strain sensor is arranged in the circular hole.

The diameter of the circular hole is 50mm.

The strain sensor is set at the center of the bottom of the asphalt mixture sample.

The temperature sensor is a thermistor temperature sensor.

The electric heating device is connected with the PLC through the first relay, the compressor is connected with the PLC through the second relay, and the temperature sensor is connected with the PLC through the A/D converter.

An intake fan is arranged under one side of the temperature simulation box, and an exhaust fan is arranged under the other side; heating lamps are arranged on both sides of the temperature simulation box.

The heating lamp is symmetrically fixed on both sides of the simulation box by bolts, and the heating lamp is one of a xenon lamp, a halogen lamp, a dysprosium lamp, and an iodine-tungsten lamp.

Compared with the prior art, the beneficial effect of the present invention is that the present invention is a programmable asphalt mixture indoor simulation fatigue test device. By setting a temperature simulation box, the temperature cycle control system is located above the temperature simulation box. A hydraulic loading system for loading the asphalt mixture sample 17 is installed, a temperature sensor is installed on the support at the bottom of the temperature simulation box, a programmable logic controller PLC and a computer are installed outside the temperature simulation box, and the temperature cycle control system is located at The top of the simulation box, the temperature cycle control system is used to heat and cool the silicone oil circulation temperature control system to control the temperature in the simulation box, so that the simulation box can realize the temperature change characteristics and trends in specific areas, so that it can simulate the temperature of the real pavement structure over time The temperature stress caused by the change. A certain volume of distilled water can be injected into the bottom of the open heat insulation water tank, and the bottom of the mold of the test piece is just in contact with water or a small amount enters the water but the test piece is not in contact with water. Since the specific heat capacity of distilled water is larger than that of the asphalt mixture test piece and it is below the test piece, the temperature change in the lower part has a certain hysteresis, and the temperature change range is smaller than that of the test piece surface, so this can simulate the real pavement structure The temperature stress caused by the difference in temperature distribution in space. The silicone oil heating circulation device is connected with the electric heating device and the refrigeration compressor through the liquid circulation device, and the silicone oil circulation temperature adjustment system is controlled by a programmable logic controller to realize the simulation of a given temperature field.

The hydraulic loading system can move on the guide rail with the movement of the lower loading wheel, and can apply pressure according to the set load size, and can simulate the influence of overload and other factors on the life of the road surface indoors. The temperature control range of the temperature simulation box in the invention is -20°C to 60°C and can be accurate to 0.1°C, which can meet the actual requirements of highway engineering in most areas.

The electric heating device of the programmable asphalt mixture indoor simulation fatigue test device of the present invention can simulate the change of the temperature field in different regions with time, not only can realize the simulation of high temperature and harsh environment, but also can use the refrigeration compressor and the silicone oil temperature cycle control system to simulate low temperature Harsh environment; the test piece base fixing device is equipped with an open thermal insulation water tank to realize the simulation of the temperature gradient of the pavement structure, and simulate the temperature field in the real pavement structure with the change of the space indoors, fully considering the temperature load on the life of the pavement structure and performance; the hydraulic loading system can accurately control the load applied by the experimental wheel to the specimen, and at the same time simulate the impact of different axle loads on the pavement structure, and realize the indoor simulation of the impact of overloading and overweight on the life and performance of asphalt pavement.

Furthermore, there are heating lamps on both sides of the simulation box, and the power of the heating lamps is adjustable, which can simulate the intensity of sunlight in different regions;

Further, the first relay, the second relay and the drive motor are connected to the programmable logic controller through wires, and the programmable logic controller is connected to the computer through wires.

Description of drawings

Figure 1 is a schematic diagram of the structure of the programmable asphalt mixture indoor simulation fatigue test device.

Figure 2 is a schematic diagram of the connection of the circulation heating device.

In the figure, 1 is the temperature simulation box, 2 is the thermistor temperature sensor, 3 is the A/D converter, 4 is the electric heating device, 5 is the first relay, 6 is the compressor, 7 is the second relay, 8 is Silicon oil high and low temperature circulation device, 9 is PLC, 10 is guide rail, 11 is hydraulic cylinder, 12 is driving motor, 13 is pressure sensor, 14 is hinged wheel shaft, 15 is loading wheel, 16 is loading table, 17 is asphalt mixture Test piece, 18 is a strain sensor, 19 is a base, 20 is an open thermal insulation water tank, 21 is a water outlet, 22 is a fluorescent lamp, 23 is an intake fan, 24 is an exhaust fan, and 25 is a computer.

detailed description

The present invention will be further described below with reference to the drawings and examples, but the present invention is not limited to the following embodiments.

Referring to Fig. 1 and Fig. 2, programmable asphalt mixture indoor simulation fatigue test device of the present invention comprises temperature simulation box 1, thermistor temperature sensor 2, A/D converter 3, electric heating device 4, first relay 5, Compressor 6, second relay 7, silicone oil high and low temperature circulation device 8, PLC9, guide rail 10, hydraulic cylinder 11, drive motor 12, pressure sensor 13, hinged wheel shaft 14, loading wheel 15, loading platform 16, asphalt mixture test Part 17, strain sensor 18, base 19, open heat insulation tank 20, drain 21, fluorescent lamp 22, intake fan 23, exhaust fan 24 and computer 25.

Specifically, a base 19 is set at the bottom of the temperature simulation box 1, the base 19 is a pull-out base, an open thermal insulation water tank 20 is fixed on the base 19, and a drain 21 is set on one side of the open thermal insulation water tank 20, and the open thermal insulation A loading platform 16 is set on the insulated water tank 20, and an asphalt mixture test piece 17 is placed on the loading platform 16. A circular hole with a diameter of 50 mm is arranged in the middle of the loading platform 16, and the circular hole is used for loading the asphalt mixture test piece. A strain sensor 18 is installed at the bottom of 17, and the strain sensor 18 is arranged at the center of the bottom of the asphalt mixture test piece 17, which avoids the influence of other factors on the strain sensor 18 when measuring the strain at the center of the bottom surface of the asphalt mixture test piece 17, and the temperature simulation box 1 Guide rails 10 are provided on both sides for the horizontal movement of the hydraulic loading system, wherein the hydraulic loading system includes a piston rod and a loading cylinder 11 capable of horizontal movement, the loading cylinder 11 is connected to the piston rod, and the piston rod is vertically arranged, the hydraulic loading system The loading cylinder 11 is fixed on the guide rail 10 with bolts, the hydraulic loading system can perform horizontal reciprocating loading movement along the guide rail 10, the lower end of the piston rod of the hydraulic loading system is fixedly connected with a pressure sensor 13, and the lower end of the pressure sensor 13 is fixed with a spiral gasket Connected with a hinged wheel shaft 14, the hinged wheel shaft 14 is connected with a loading wheel 15 for loading the asphalt mixture sample 17, and one side of the hinged wheel shaft 14 is fixed with a drive motor 12, and the output shaft of the drive motor 12 is connected to the Hinged axle 14 is connected. The upper part of the temperature simulation box 1 is provided with an electric heating device 4 and a compressor 6, the compressor 6 is arranged below the electric heating device 4, the electric heating device 4 is connected with the PLC9 through the first relay 5, and the compressor 6 is connected with the PLC9 through the second relay 7 connection, the silicone oil high and low temperature circulation device 8 realizes temperature control on the temperature simulation box 1 through pipelines, an intake fan 23 is set under one side of the temperature simulation box 1, an exhaust fan 24 is set under the other side, and both sides of the temperature simulation box 1 A fluorescent lamp 22 is arranged, and the heating lamp 22 is symmetrically fixed on both sides of the simulation box by bolts, and the heating lamp 22 is one of a xenon lamp, a halogen lamp, a dysprosium lamp, and an iodine-tungsten lamp. The temperature sensor 2 that is arranged in the temperature simulation box 1 is connected with PLC9 through A/D converter 3, and described temperature sensor 2 is photoresistor temperature sensor; Temperature sensor 2 converts the temperature signal that receives into voltage signal, A/D Converter 3 converts the input voltage signal into a digital quantity recognizable by PLC9, and then PLC9 compares the temperature value set by the system with the temperature value fed back, and then sends a The control signal controls whether the output end is turned on or not, and the first relay 5 and the second relay 7 respectively control the operation of the electric heating device 4 and the compressor 6 to realize the adjustment of the temperature in the temperature simulation box 1 . PLC9 is connected with computer 25 through data connection line.

The working process of the present invention is as follows: during the experiment, the pull-out base 19 is opened, the asphalt mixture sample 17 is fixed on the loading table 16 above the open-mouth insulating water tank 20 by bolts, and the pull-out base 19 is pushed into the In the temperature simulation box 1, the fluorescent lamp 22 is kept as a constant light source for illumination, and the air intake fan 23 and the exhaust fan 24 are operated to maintain air circulation inside the temperature simulation box 1. The computer 25 is connected to the PLC9 according to the starting point of the set temperature, controls the temperature simulation box 1 to heat or cool down to the specified temperature, and keeps at a constant temperature for 2 hours to stabilize the temperature in the asphalt mixture test piece 17 and the temperature simulation box 1 at the starting point temperature, then set The parameters of the hydraulic loading system are such that the loading wheel 15 is lowered to be in close contact with the asphalt mixture specimen 17 and loaded with a set pressure, and the driving speed of the drive motor 12 is set so that the loading wheel 15 is mixed with the asphalt at the set speed. The surface of 17 pieces of material was tested to and fro. According to the set temperature data curve, the computer 25 gives a control signal to the input terminals of the first relay 5 and the second relay 7 through the PLC9 to control whether the output terminals are turned on or not, and the first relay 5 and the second relay 7 respectively control the electric heating device 4 and the compressor 6 work to realize the adjustment of the temperature in the temperature simulation box 1. The temperature sensor 2 in the simulation box converts the temperature change signal in the temperature simulation box 1 into a voltage signal, and the A/D converter 3 converts the input voltage signal into a digital quantity recognizable by PLC9, and then PLC9 converts the temperature set by the system After the temperature value is compared with the feedback temperature value, a control signal is given to the input terminals of the first relay 5 and the second relay 7 to control whether the output terminal is turned on or not, and the first relay 5 and the second relay 7 respectively control the electric heating device 4 Work with the compressor 6 to realize the adjustment of the temperature in the temperature simulation box 1. The computer 25 draws a stress-strain curve according to the strain sensor 18 at the bottom center of the asphalt mixture test piece 17 and the pressure sensor 13 fixedly connected to the lower end of the piston rod of the hydraulic cylinder 11, and analyzes the asphalt according to the strain change curve of the asphalt mixture test piece during the loading process. Fatigue performance decay process of mixture specimens.

The electric heating device in the present invention can make the temperature changes in different positions inside the device more uniform, and can accurately simulate the influence of sunlight in the area where the asphalt concrete pavement is located and the temperature of the pavement changing with time and space on the temperature of the asphalt pavement, improving the experimental simulation The accuracy of the real temperature environment. Its loading device can also adjust the reciprocating speed of the test wheel and the pressure of the test wheel on the test piece to simulate the damage effect of the vehicle load on the asphalt pavement.

Claims (10)

1. a programmable asphalt lab simulation fatigue experimental device, it is characterized in that, including temperature simulation case (1), described temperature simulation case (1) inner bottom part is provided with base (19), base (19) is provided with uncovered insulation tank (20), uncovered insulation tank (20) is arranged to place the loading bench (16) of asphalt sample (17), in loading bench (16), is provided above the hydraulic loading system for asphalt sample (17) is loaded；Temperature simulation case is additionally provided with temperature circulation control system in (1), wherein temperature circulation control system includes silicone oil high temperature and low temperature circulating device (8), electric heater unit (4), compressor (6) and temperature sensor (2), silicone oil high temperature and low temperature circulating device (8) and electric heater unit (4), compressor (6) is connected with temperature sensor (2), compressor (6), electric heater unit (4) is all connected with the PLC (9) being arranged on temperature simulation case (1) outside with temperature sensor (2), PLC (9) is connected to computer (25).

2. a kind of programmable asphalt lab simulation fatigue experimental device according to claim 1, it is characterized in that, described hydraulic loading system includes piston rod and the load cylinder (11) that can move horizontally, load cylinder (11) is connected with piston rod, and piston rod is vertically arranged, the lower end of piston rod is provided with pressure transducer (13), the lower end of pressure transducer (13) is provided with hinged wheel shaft (14), and hinged wheel shaft (14) is provided with loading wheel (15) for asphalt sample (17) is loaded.

3. a kind of programmable asphalt lab simulation fatigue experimental device according to claim 2, it is characterized in that, described hydraulic loading system also includes drive motor (12), and the output shaft of drive motor (12) is connected with hinged wheel shaft (14).

4. a kind of programmable asphalt lab simulation fatigue experimental device according to claim 2, it is characterized in that, being provided with the track (10) moved horizontally for hydraulic loading system in described temperature simulation case (1), load cylinder (11) is arranged on guide rail (10).

5. a kind of programmable asphalt lab simulation fatigue experimental device according to claim 1, it is characterised in that described base (19) is drawing type base；Loading bench offers circular port on (16), is provided with strain transducer (18) in circular port.

6. a kind of programmable asphalt lab simulation fatigue experimental device according to claim 5, it is characterised in that the diameter of described circular port is 50mm.

7. a kind of programmable asphalt lab simulation fatigue experimental device according to claim 5, it is characterised in that described strain transducer (18) is arranged on asphalt sample (17) bottom centre position.

8. a kind of programmable asphalt lab simulation fatigue experimental device according to claim 1, it is characterised in that described temperature sensor (2) is thermistor temperature sensor.

9. a kind of programmable asphalt lab simulation fatigue experimental device according to claim 1, it is characterized in that, described electric heater unit (4) is connected with PLC (9) by the first relay (5), compressor (6) is connected with PLC (9) by the second relay (7), and temperature sensor (2) is connected with PLC (9) by A/D interpreter (3).

10. a kind of programmable asphalt lab simulation fatigue experimental device according to claim 1, it is characterized in that, described temperature simulation case (1) side is arranged below supply fan (23), and opposite side is arranged below scavenger fan (24)；In described temperature simulation case, (1) both sides are provided with heating lamp (22).