Split asphalt concrete small beam bending test device especially suitable for high-low temperature box

Abstract

The invention provides a split asphalt concrete small beam bending test device particularly suitable for a high-low temperature box. The device comprises a small beam bending tester, a load sensor, a displacement sensor, a temperature sensor, a control cabinet and a computer data acquisition system, the small beam bending testing machine comprises a testing main machine, a loading assembly and a load bearing assembly. The split type asphalt concrete small beam bending test device particularly suitable for the high-low temperature box is reasonable in design and high in operability, and the result is direct when the split type asphalt concrete small beam bending test device is adopted for carrying out a small beam test. The device has very positive significance in measuring the bending stress, the bending strain and the bending stiffness of the asphalt concrete at different test temperatures and different deformation rates, researching the flexibility and the deformation capability of the asphalt concrete and researching the stress and strain states in a load-bearing bending state.

Description

Technical Field

[0001] The invention belongs to the technical field of asphalt concrete testing devices, and in particular relates to a split asphalt concrete small beam bending testing device which is particularly suitable for high and low temperature boxes. Background Art

[0002] Asphalt concrete is a typical viscoelastic material under normal temperature conditions. At present, the earth-rock dams of the upper reservoir, lower reservoir or conventional reservoir of pumped storage power stations often use anti-seepage panels with the properties of asphalt concrete. The asphalt concrete beam bending test can test the deformation performance of asphalt concrete and effectively evaluate the mechanical properties and structural strength of asphalt concrete, which is of great significance for ensuring the quality and safety of the project.

[0003] At present, there are no mature specific styles and products of smaller split beam bending testing machines suitable for high and low temperature boxes in the prior art. Summary of the invention

[0004] In view of the defects in the prior art, the present invention provides a split asphalt concrete beam bending test device that is particularly suitable for high and low temperature boxes, which can effectively solve the above problems.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] The present invention provides a split type asphalt concrete small beam bending test device which is particularly suitable for a high and low temperature box, comprising: a small beam bending test machine, a load sensor (8), a displacement sensor (13), a temperature sensor (17), a control cabinet (18) and a computer data acquisition system (19);

[0007] An asphalt concrete specimen (11) is placed in the small beam bending test machine; the small beam bending test machine is used to perform a small beam bending test on the asphalt concrete specimen (11), so that the specimen (11) undergoes mid-span deformation at a designed deformation rate;

[0008] The load sensor (8) is located at the center of the upper part of the asphalt concrete specimen (11) and is used to collect the mid-span load of the asphalt concrete specimen (11); the displacement sensor (13) is located at the center of the lower edge of the mid-span of the asphalt concrete specimen (11) and is in contact with the bottom surface of the asphalt concrete specimen (11) and is used to collect the mid-span displacement of the lower edge of the mid-span of the asphalt concrete specimen (11), that is, the mid-span deflection; the temperature sensor (17) is arranged near the asphalt concrete specimen (11) and is used to collect the temperature of the asphalt concrete specimen (11) during the small beam bending test;

[0009] The load sensor (8), the displacement sensor (13) and the temperature sensor (17) are all connected to one end of the control cabinet (18); the other end of the control cabinet (18) is connected to the computer data acquisition system (19).

[0010] Preferably, the beam bending test machine comprises a test host, a loading component and a load-bearing component;

[0011] The test host comprises a horizontally arranged top plate (1), a horizontally arranged bottom plate (2), a vertically arranged cylinder (3) connecting the top plate (1) and the bottom plate (2), and a servo motor screw lift (16); the servo motor screw lift (16) is installed above the bottom plate (2);

[0012] The loading assembly is arranged above the asphalt concrete specimen (11), and comprises an upper connecting member (7), a lower connecting member (9) and a pressure head (10); the upper connecting member (7) is arranged vertically and is located directly above the center of the asphalt concrete specimen (11); the upper part of the upper connecting member (7) passes through the mounting through hole in the center of the top plate (1) and is locked with the top plate (1) through a nut (5) and a metal gasket (6); the bottom end of the upper connecting member (7) is connected to the upper part of the load sensor (8); the lower connecting member (9) and the upper connecting member (7) are arranged coaxially above and below; the upper part of the lower connecting member (9) is connected to the bottom end of the load sensor (8), and the bottom end of the lower connecting member (9) is connected to the pressure head (10); the pressure head (10) is a plate-like structure, and the lower end of the cross section of the pressure head (10) is a semicircular arc and contacts the upper surface of the asphalt concrete specimen (11);

[0013] The load-bearing assembly is arranged below the asphalt concrete specimen (11), and comprises a pressure-bearing support (14) and a pressure-bearing bottom plate (15); the pressure-bearing bottom plate (15) is arranged horizontally and is connected and fixed to the top flange of the servo motor screw lift (16) located below it by bolts; a pair of pressure-bearing supports (14) arranged opposite to each other and used for supporting the asphalt concrete specimen (11) are vertically fixed on the pressure-bearing bottom plate (15);

[0014] Driven by the servo motor screw lift (16), the load-bearing assembly formed by the pressure-bearing support (14) and the pressure-bearing base plate (15) moves upward, and under the joint action of the loading assembly, force is applied to the upper surface of the asphalt concrete specimen (11).

[0015] Preferably, the pressure bearing support (14) is a plate-shaped pressure bearing support, the upper end of the cross section of the pressure bearing support (14) is semicircular, and the distance between the two pressure bearing supports (14) matches the length of the asphalt concrete specimen (11) to be tested.

[0016] Preferably, a magnetic base (12) is placed on the pressure-bearing base plate (15), and the displacement sensor (13) and the temperature sensor (17) are mounted on the magnetic base (12).

[0017] Preferably, the four corners of the top plate (1) and the bottom plate (2) are respectively provided with through holes, and the upper and lower ends of the cylinder (3) are respectively provided with threads, and the top plate (1) and the bottom plate (2) are fixed to the upper and lower ends of the cylinder (3) by means of large nuts (4), thereby assembling the top plate (1), the bottom plate (2) and the cylinder (3) to form a whole.

[0018] Preferably, through holes are provided at the four corners of the base of the servo motor screw lift (16), and through holes are provided at corresponding positions of the base plate (2), and the servo motor screw lift (16) is connected and installed on the base plate (2) by bolts and nuts.

[0019] Preferably, the upper connecting member (7) and the load sensor (8), the load sensor (8) and the lower connecting member (9), and the lower connecting member (9) and the pressure head (10) are respectively connected by threads.

[0020] Preferably, the pressure-bearing support (14) and the pressure-bearing base plate (15), and the pressure-bearing base plate (15) and the flange at the top end of the servo motor screw lift (16) are respectively connected by bolt threads.

[0021] Preferably, the temperature sensor (17) is a low-temperature resistant sensor, which can work for a long time in an environment of -70°C to 100°C, has a measuring range of -150°C to 150°C, and a minimum graduation value of 0.1°C;

[0022] The load sensor (8) is an ultra-low temperature force sensor with internal threads at both ends, which can work for a long time in an environment of -70°C to 100°C, has a measuring range of 10kN, a minimum graduation value of 0.01kN, and can measure tension, pressure, and tension-pressure;

[0023] The displacement sensor (13) is a low-temperature resistant displacement sensor, capable of operating for a long time in an environment of -70°C to 100°C, with a measuring range of 100 mm and a minimum graduation value of 0.01 mm;

[0024] The servo motor used in the servo motor screw lift (16) is a low-temperature resistant servo motor and can work for a long time in an environment of -70°C to 100°C.

[0025] The present invention also provides a method for performing a beam bending test using the aforementioned split asphalt concrete beam bending test device, which is particularly suitable for a high and low temperature box, comprising the following steps:

[0026] Step S1, placing the test main machine of the beam bending test machine into a high and low temperature box, connecting the test main machine, the loading component, and the load-bearing component of the beam bending test machine to obtain the beam bending test machine, and adjusting the bottom plate (2) and the top plate (1) to a horizontal state;

[0027] Step S2, placing the load sensor (8), the displacement sensor (13), and the temperature sensor (17) in a high and low temperature box, and connecting the beam bending tester, the load sensor (8), the displacement sensor (13), the temperature sensor (17), the control cabinet (18), and the computer data acquisition system (19);

[0028] Step S3, placing the asphalt concrete specimen (11) on frosted glass coated with talcum powder in a high and low temperature box, and adjusting the high and low temperature box to the test temperature, and keeping the temperature constant for 3-5 hours, at which time the small beam bending test machine and the interior of the asphalt concrete specimen (11) both reach the specified test temperature;

[0029] Step S4, quickly open the high and low temperature box, and symmetrically place the asphalt concrete specimen (11) on the pressure bearing support (14) of the small beam bending tester, the up and down direction of the asphalt concrete specimen (11) is consistent with the direction when the specimen is prepared and formed; the extended parts of the asphalt concrete specimen (11) remaining outside the two pressure bearing supports (14) are equal in length, and the asphalt concrete specimen (11) is supported by the two pressure bearing supports (14);

[0030] Step S5, adjusting the positions of the displacement sensor (13), the temperature sensor (17) and the load sensor (8) relative to the asphalt concrete specimen (11):

[0031] A displacement sensor (13) is placed between the two pressure bearing supports (14) below the asphalt concrete specimen (11); the displacement sensor (13) is fixed to the pressure bearing base plate (15) by a magnetic table base (12) so that the probe of the displacement sensor (13) is located at the exact center of the lower edge of the cross section in the middle of the specimen; the effective range of the displacement sensor (13) is greater than 1.2 times the maximum deflection of the specimen expected in the test;

[0032] The temperature sensor (17) is arranged near the asphalt concrete test piece (11) and cannot touch the test piece during the test;

[0033] The load sensor (8) is located at the center of the upper part of the asphalt concrete specimen (11), and the pressure head (10) is in contact with the upper surface of the asphalt concrete specimen (11);

[0034] Recording the initial indications of the load sensor (8) and the displacement sensor (13);

[0035] Step S6, close the high and low temperature box door, start the constant temperature device, and maintain the constant temperature at the specified test temperature for 30 minutes;

[0036] Step S7, start the beam bending test machine, control the loading according to the required deformation rate, and transmit the collected signals to the computer data acquisition system (19) by the load sensor (8) and the displacement sensor (13), and draw a load-displacement curve;

[0037] When the specimen is destroyed, the computer prints out the specimen number, temperature, failure load and failure displacement; the failure load is the peak point of the load-displacement curve, and its corresponding displacement coordinate value is the failure displacement value;

[0038] Step S8, assuming that the failure load at the mid-span of the asphalt concrete specimen (11) when it fails is F B , the clear span length is L, the specimen section dimensions are width b, height h, length L′; the failure displacement is d;

[0039] The failure stress σ of the specimen is obtained using the following formula: B 、Failure strain ε B and breaking stiffness S B :

[0040]

[0041] Step S9, a group of asphalt concrete test pieces (11) is a plurality of pieces; the asphalt concrete test pieces (11) in the same group are tested in sequence; the obtained failure stress σ B 、Failure strain ε B and breaking stiffness S B After outlier identification and processing, a set of failure stress σ is finally obtained. B 、Failure strain ε B and breaking stiffness S B , as the final test result.

[0042] The split asphalt concrete beam bending test device provided by the present invention, which is particularly suitable for high and low temperature boxes, has the following advantages: reasonable design, strong operability, and direct results of beam bending test using the device. It has a very positive significance for measuring the bending stress, bending strain, and bending stiffness of asphalt concrete at different test temperatures and deformation rates, studying the flexibility and deformation capacity of asphalt concrete, and the stress and strain state under the loaded bending state. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 A structural diagram of a split asphalt concrete beam bending test device provided by the present invention, which is particularly suitable for a high and low temperature box;

[0044] Figure 2 This is a schematic diagram of the force on the sample provided by the present invention.

[0045] in:

[0046] Top plate 1; bottom plate 2; cylinder 3; large nut 4; nut 5; metal gasket 6; upper connecting piece 7; load sensor 8; lower connecting piece 9; pressure head 10; asphalt concrete specimen 11; magnetic table base 12; displacement sensor 13; pressure bearing support 14; pressure bottom plate 15; servo motor screw lift 16; temperature sensor 17; control cabinet 18; computer data acquisition system 19. DETAILED DESCRIPTION

[0047] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0048] The present invention provides a split asphalt concrete small beam bending test device which is particularly suitable for high and low temperature boxes. When the small beam bending test is carried out by using the split asphalt concrete small beam bending test device, at a constant test temperature, a concentrated load is applied to the mid-span of the beam specimen by setting a specified mid-span deformation rate until the specimen is destroyed. During the test, the load and the displacement of the center of the lower edge of the mid-span cross-section of the beam specimen are automatically collected and recorded, and the mid-span deflection of the specimen at different time intervals is calculated, and then the mid-span stress, mid-span deflection, mid-span strain of the specimen and the bending stress, bending strain and bending stiffness of the specimen are calculated to study the flexibility and deformation capacity of asphalt concrete, and the stress and strain state under the loaded bending state.

[0049] The present invention provides a split asphalt concrete beam bending test device, which is particularly suitable for high and low temperature boxes. It has a reasonable design and strong operability. The beam bending test result can be directly obtained by using the device. It has a very positive significance for measuring the bending stress, bending strain and bending stiffness of asphalt concrete at different test temperatures and deformation rates, studying the flexibility and deformation capacity of asphalt concrete, and the stress and strain state under the loaded bending state.

[0050] See also Figure 1 , the present invention provides a split asphalt concrete beam bending test device particularly suitable for high and low temperature boxes, including: a beam bending test machine, a load sensor 8, a displacement sensor 13, a temperature sensor 17, a control cabinet 18 and a computer data acquisition system 19;

[0051] The small beam bending test machine is used in combination with the load sensor 8, the displacement sensor 13, the temperature sensor 17, the control cabinet 18 and the computer data acquisition system 19 to form a small beam bending test device. The small beam bending test is carried out on the beam-type specimen prepared by asphalt concrete material to obtain the mid-span deflection, mid-span stress, mid-span strain, etc. of the specimen.

[0052] An asphalt concrete specimen 11 is placed in the small beam bending test machine; the small beam bending test machine is used to perform a small beam bending test on the asphalt concrete specimen 11, so that it undergoes mid-span deformation at a designed deformation rate;

[0053] The load sensor 8 is located at the center of the upper part of the asphalt concrete specimen 11, and is used to collect the mid-span load of the asphalt concrete specimen 11; the displacement sensor 13 is located at the center of the lower edge of the mid-span of the asphalt concrete specimen 11 and is in contact with the bottom surface of the asphalt concrete specimen 11, and is used to collect the mid-span displacement of the lower edge of the mid-span of the asphalt concrete specimen 11, that is, the mid-span deflection; the temperature sensor 17 is set at a position near the asphalt concrete specimen 11, and is used to collect the temperature of the asphalt concrete specimen 11 during the beam bending test;

[0054] The load sensor 8 , the displacement sensor 13 and the temperature sensor 17 are all connected to one end of the control cabinet 18 ; the other end of the control cabinet 18 is connected to the computer data acquisition system 19 .

[0055] The main components of the present invention are described in detail below:

[0056] (1) Beam bending test machine

[0057] The small beam bending test machine comprises a test main machine, a loading component and a load-bearing component.

[0058] (1.1) Test host

[0059] The test host comprises a horizontally arranged square top plate 1, a horizontally arranged square bottom plate 2, four vertically arranged columns 3 connecting the top plate 1 and the upper and lower four corners of the bottom plate 2, and a servo motor screw lift 16; the servo motor screw lift 16 is installed above the bottom plate 2;

[0060] The specific assembly method of the top plate 1, the bottom plate 2 and the cylinder 3 is as follows: the four corners of the top plate 1 and the bottom plate 2 are respectively provided with through holes, the upper and lower ends of the cylinder 3 are respectively provided with threads, and the top plate 1 and the bottom plate 2 are fixed to the upper and lower ends of the cylinder 3 by large nuts 4, so that the top plate 1, the bottom plate 2 and the cylinder 3 are assembled to form a whole.

[0061] Furthermore, a mounting through hole is provided at the center of the top plate 1 for connecting a loading component;

[0062] The specific installation method of the servo motor screw lift 16 is as follows: through holes are provided at the four corners of the base of the servo motor screw lift 16, and through holes are provided at corresponding positions of the bottom plate 2, and the servo motor screw lift 16 is connected and installed on the bottom plate 2 by bolts and nuts. A flange is provided on the top of the servo motor screw lift 16 for connecting the load-bearing component.

[0063] (1.2) Loading components

[0064] The loading assembly is arranged above the asphalt concrete specimen 11, and includes an upper connecting member 7, a lower connecting member 9 and a pressurizing head 10; the upper connecting member 7 is arranged vertically and is located directly above the center of the asphalt concrete specimen 11; the upper part of the upper connecting member 7 passes through the mounting through hole in the center of the top plate 1 and is locked with the top plate 1 through a nut 5 and a metal gasket 6; the nut 5 adopts an anti-falling metal nut; the bottom end of the upper connecting member 7 is connected to the upper part of the load sensor 8; the lower connecting member 9 is arranged coaxially with the upper connecting member 7 above and below; the upper part of the lower connecting member 9 is connected to the bottom end of the load sensor 8, and the bottom end of the lower connecting member 9 is connected to the pressurizing head 10, the pressurizing head 10 is a plate-like structure, and the lower end of the cross section of the pressurizing head 10 is a semicircular arc and contacts the upper surface of the asphalt concrete specimen 11;

[0065] For the convenience of assembly, the upper connecting member 7 and the load sensor 8, the load sensor 8 and the lower connecting member 9, and the lower connecting member 9 and the pressure head 10 are respectively connected by threads.

[0066] (1.3) Load-bearing components

[0067] The load-bearing assembly is arranged below the asphalt concrete specimen 11, and includes two pressure bearings 14 and a pressure bearing bottom plate 15; the pressure bearing bottom plate 15 is arranged horizontally, and may be an octagonal pressure bearing bottom plate, and is connected and fixed to the top flange of the servo motor screw lift 16 located below it by bolts; a pair of pressure bearings 14 arranged opposite to each other for supporting the asphalt concrete specimen 11 are vertically fixed on the pressure bearing bottom plate 15; as a preferred embodiment, the pressure bearing 14 is a plate-shaped pressure bearing, and the upper end of the cross section of the pressure bearing 14 is semicircular, and the distance between the two pressure bearings 14 matches the length of the asphalt concrete specimen 11 to be measured. A magnetic meter base 12 is placed on the pressure bearing bottom plate 15, and the displacement sensor 13 and the temperature sensor 17 are installed on the magnetic meter base 12.

[0068] For the convenience of assembly, the pressure bearing support 14 and the pressure bearing bottom plate 15, and the pressure bearing bottom plate 15 and the flange at the top end of the servo motor lead screw lift 16 are respectively connected by bolt threads.

[0069] During the test, the displacement sensor 13 is in contact with the bottom surface of the asphalt concrete specimen 11. Driven by the servo motor screw lift 16, the load-bearing assembly formed by the pressure bearing support 14 and the pressure bottom plate 15 moves upward, so that the screw of the servo motor screw lift 16, the pressure bottom plate 15 and the pressure bearing support 14 move upward together, and under the joint action of the pressure bearing support 14 and the pressure head 10 of the loading assembly, force is applied to the upper surface of the asphalt concrete specimen 11.

[0070] (ii) Performance of load sensor 8, displacement sensor 13, temperature sensor 17 and servo motor screw lift 16

[0071] In the present invention, the temperature sensor 17 is a low-temperature resistant sensor, which can work for a long time in an environment of -70℃~100℃, has stable and reliable performance, a measuring range of -150℃~150℃, a minimum division value of 0.1℃, and can be connected to a control cabinet 18 and a computer data acquisition system 19 for use.

[0072] The load sensor 8 is an ultra-low temperature force sensor with internal threads at both ends. It can work for a long time in an environment of -70℃ ~ 100℃, has stable and reliable performance, a measuring range of 10kN, and a minimum division value of 0.01kN. It can measure tension, pressure, and tension-pressure, and can be connected to the control cabinet 18 and the computer data acquisition system 19 for use.

[0073] The displacement sensor 13 is a low-temperature resistant displacement sensor, which can work for a long time in an environment of -70°C to 100°C, has stable and reliable performance, a measuring range of 100mm, and a minimum division value of 0.01mm. It can be connected to a control cabinet 18 and a computer data acquisition system 19 for use.

[0074] The servo motor used in the servo motor screw lift 16 is a low-temperature resistant servo motor, which can work for a long time in an environment of -70°C to 100°C, has stable and reliable performance, and can be connected to a control cabinet 18 and a computer data acquisition system 19 for use.

[0075] The length, width and height of the space inside the high and low temperature box are all more than 1m, and the volume is about 1m 3 Above, the temperature control range is -100℃~100℃, and the temperature difference is controlled within ±1℃.

[0076] The following is a specific example of a split asphalt concrete beam bending test device that is particularly suitable for high and low temperature boxes:

[0077] This embodiment provides a split asphalt concrete small beam bending test device particularly suitable for high and low temperature boxes, including: a small beam bending test machine, a load sensor 8, a displacement sensor 13, a temperature sensor 17, a control cabinet 18 and a computer data acquisition system 19;

[0078] The small beam bending test machine comprises a test host, a loading component and a load-bearing component.

[0079] The test host is composed of a top plate 1, a bottom plate 2, 4 cylinders 3, 16 large nuts 4, and a set of servo motor screw lift 16. The servo motor screw lift 16 is connected to the bottom plate 2 through 4 standard external hexagonal M10 cap bolts and 4 standard external hexagonal M10mm nuts and installed on the bottom plate 2.

[0080] The top plate 1 is provided with through holes at the four corners and the center respectively; specifically, the top plate 1 is made of stainless steel, 500mm long, 500mm wide, 30mm thick, with a circular hole with a diameter of 20mm in the center, and circular holes with a diameter of 30mm in the four corners 12mm away from the edge.

[0081] The bottom plate 2 is provided with through holes at four corners 12 mm away from the edge and at the center, and through holes are also provided at the four corners 120 mm away from the edge; specifically, the bottom plate 2 is made of stainless steel, 500 mm long, 500 mm wide, and 30 mm thick, with a circular hole of 40 mm in diameter in the center, circular holes of 30 mm in diameter at the four corners 12 mm away from the edge, and circular holes of 10 mm in diameter at the four corners 120 mm away from the edge.

[0082] The upper and lower ends of the cylinder 3 are respectively provided with threads, and through holes are provided at the upper and lower corners of the top plate 1 and the bottom plate 2. The top plate 1 and the bottom plate 2 are fixed to the cylinder 3 by large nuts 4. Specifically, the cylinder 3 is made of stainless steel, with a diameter of 30mm and a length of 700mm. The surface of the 500mm long middle part is smooth; the 100mm long parts at both ends are provided with threads with a spacing of 1mm, which can be fastened to the top plate 1 and the bottom plate 2 by large nuts 4.

[0083] The 16 large nuts 4 in the test host are standard M30 hexagonal nuts.

[0084] The four corners of the base of the servo motor screw lift 16 are respectively provided with through holes, through which bolts are respectively passed downward through the through holes at the four corners of the bottom plate 2 at a distance of 120 mm from the edge, and then the servo motor screw lift 16 is fixed to the bottom plate 2 with nuts. Specifically, in the servo motor screw lift 16, the servo motor and the trapezoidal screw screw lift are mechatronically combined, the lifting is automatically controlled, the lifting speed is adjustable, and the servo motor has a constant torque output with speed regulation; the servo motor is a vacuum high and low temperature servo motor, the working environment is -70~100℃, the voltage is 220V, the power is 750W, and the speed is 1500RPM; the screw lift has an overall height of less than 350mm, a stroke of 200mm, a screw length of 270mm, a diameter of 20mm, and a thread pitch of 1mm; the flange at the top of the screw has a diameter of 200mm and a thickness of 10mm, and there are 4 through holes with a diameter of 8mm evenly distributed around the center at 75mm, which are used to be connected to the pressure base through bolt threads, with a load of 2T, a speed of 0.005~2mm / s, and a self-locking function. The base of the servo motor screw lift 16 is 300 mm long, 300 mm wide, and 10 mm thick. A through hole with a diameter of 10 mm is provided at each of the four corners 20 mm away from the edge of the base for bolt connection with the bottom plate 2 of the beam bending test machine.

[0085] The loading assembly includes two anti-falling metal nuts, two metal washers 6, an upper connecting piece 7, a lower connecting piece 9, a pressurizing head 10, and is used in conjunction with a load sensor 8;

[0086] The anti-fall metal nut is a standard M18 hexagonal nut, which is used to prevent the upper connecting piece 7, load sensor 8, lower connecting piece 9, and pressure head 10 from falling when the sample is compressed and fractured, thereby damaging the pressure support 14, displacement sensor 13, magnetic table base 12, etc., and preventing itself from being deformed due to falling and collision.

[0087] The metal gasket 6 is a standard flat gasket with a nominal specification of 18, an inner diameter of 19 mm, an outer diameter of 34 mm, and a thickness of 3 mm.

[0088] The upper connecting piece 7 is made of stainless steel, with an upper end having a diameter of 18 mm and a length of 118 mm; a lower end having a length of 12 mm and a diameter of 8 mm; both upper and lower ends are provided with threads with a spacing of 1 mm, the upper end can pass through the top plate 1 of the main frame, the gasket and the anti-fall metal nut to be connected, and the lower end can pass through the gasket, the anti-fall metal nut and the center screw hole of the load sensor 8 to be connected to each other.

[0089] The load sensor 8 uses an ultra-low temperature force sensor with internal threads at both ends, which can work for a long time in an environment of -70℃~100℃ with stable and reliable performance. The overall height is 35mm. The outer diameter of the threaded connection part between the upper end and the upper connecting piece 7 is 14mm, the aperture is 8mm, the thread pitch is 1mm, and the depth is 12mm; the middle part has a diameter of 28mm and a height of 15mm; the outer diameter of the threaded connection part between the bottom end and the lower connecting piece 9 is 14mm, the aperture is 8mm, the thread pitch is 1mm, and the depth is 8mm. The measuring range is 10kN, and the minimum division value is 0.01kN. It can measure tension, pressure, and tension pressure. The load sensor 8 can be used in conjunction with a display transmitter and a control cabinet 18 and a computer data acquisition system 19.

[0090] The lower connecting piece 9 is made of stainless steel and is 40 mm long. The upper end is provided with a thread with a pitch of 1 mm, a diameter of 8 mm, and a length of 8 mm, which can be interconnected with the center screw hole at the bottom of the load sensor 8. The middle part has a smooth surface, a diameter of 16 mm, and a length of 20 mm. The lower end is provided with a thread with a pitch of 1 mm, a diameter of 16 mm, and a length of 16 mm, which can be interconnected with the center screw hole of the pressure head.

[0091] The pressure head 10 is made of stainless steel. The main body of the pressure head 10 is 20 mm high, 60 mm long, and 20 mm thick. The lower end surface is a semicircular arc with a radius of 8 mm and a smooth surface. A central circular hole is provided at the top center of the pressure head 10, with a diameter of 10 mm and a depth of 16 mm. The inner wall surface is provided with threads with a thread pitch of 1 mm for interconnection with the lower connecting piece 9. The smooth contact surface between the pressure head 10 and the test piece is an arc with a radius of 8 mm.

[0092] The test specimens prepared from asphalt concrete materials are prismatic in shape, with dimensions of 250±2mm, 30±2mm in width, and 35±2mm in height.

[0093] The load-bearing assembly includes two pressure-bearing supports 14, one pressure-bearing base plate 15, and ten flat-head M8 hexagon socket full-length designated bolts.

[0094] The pressure bearing 14 is made of stainless steel, with a main body height of 188mm, a length of 120mm, and a thickness of 16mm. The uppermost surface is a semicircular arc with a radius of 8mm and a smooth surface. Three holes with a diameter of 8mm are arranged along the length centerline direction at the bottom of the pressure bearing 14. The thread pitch on the inner surface of the hole is 1mm and the depth is 15mm. The bottom of the pressure bearing 14 and the pressure base plate 15 can be embedded and connected by a flat head M8 hexagon socket full-length designated bolt.

[0095] The longitudinal centerline distance between the two pressure bearings 14 is 200mm, and the smooth contact surface between the pressure bearing 14 and the specimen is an arc with a radius of 8mm. The two pressure bearings 14 are symmetrically fixed to the pressure bearing base plate 15 with three flat-head M8 hexagon socket full-length designated bolts with the base plate as the center;

[0096] The pressure base plate 15 is octagonal and is fixed to the flange at the top of the servo motor screw lift 16 with the center of the pressure base plate 15 as the center by four flat-head M8 hexagon socket full-length designated bolts.

[0097] Specifically, the pressure-bearing bottom plate 15 is made of stainless steel, 16 mm thick, with a regular octagon on the top and bottom surfaces and a width of 400 mm. At 100 mm from the left and right edges of the pressure-bearing bottom plate 15, there are three circular holes with a diameter of 8 mm, and the distance between the centers of the circular holes is 40 mm. The center of the central circular hole in the row is 200 mm away from the upper and lower edges of the bottom plate. The inner wall of the circular hole is provided with a thread with a thread spacing of 1 mm, and is connected to the pressure-bearing support 14 through a flat-head M8 hexagonal full-length designated bolt. At 75 mm above, below, left and right from the center of the pressure-bearing bottom plate 15, there is a circular hole with a diameter of 8 mm, and the distance between the center of each circular hole and the center of the pressure-bearing bottom plate 15 is 75 mm. The inner wall of the circular hole is provided with a thread with a thread spacing of 1 mm, and is threadedly connected to the flange at the top of the servo motor screw lift 16 through a flat-head M8 hexagonal full-length designated bolt.

[0098] During the test, the displacement sensor 13 is placed and fixed between the two pressure-bearing supports 14 on the bottom plate using a magnetic stand 12. The probe is vertically upward and in contact with the center of the lower edge of the cross section in the middle of the vertical length direction of the specimen. The mid-span deflection of the specimen at different time intervals is obtained by measuring and recording the readings of the displacement sensor, and then the mid-span stress, mid-span strain, bending stress, bending strain and bending stiffness of the specimen at different specimen intervals and at failure are calculated.

[0099] The present invention also provides a method for performing a beam bending test using the split asphalt concrete beam bending test device that is particularly suitable for a high and low temperature box, comprising the following steps:

[0100] Step S1, placing the test host of the beam bending test machine into a high and low temperature box, connecting the test host, the loading component, and the load-bearing component of the beam bending test machine to obtain the beam bending test machine, and adjusting the bottom plate 2 and the top plate 1 to a horizontal state;

[0101] Step S2, placing the load sensor 8, the displacement sensor 13, and the temperature sensor 17 in a high and low temperature box, and connecting the beam bending tester, the load sensor 8, the displacement sensor 13, the temperature sensor 17, the control cabinet 18, and the computer data acquisition system 19;

[0102] Step S3, placing the asphalt concrete specimen 11 on frosted glass coated with talcum powder in a high and low temperature box, the specimen size is, for example, 250±2mm, 30±2mm wide, 35±2mm high, and is prismatic, and the high and low temperature box is adjusted to a test temperature such as -35°C, and the constant temperature is maintained for 3-5h, at which time the small beam bending tester and the interior of the asphalt concrete specimen 11 reach the specified test temperature;

[0103] Step S4, quickly open the high and low temperature box, and symmetrically place the asphalt concrete specimen 11 on the pressure bearing support 14 of the beam bending tester, the up and down direction of the asphalt concrete specimen 11 is consistent with the direction when the specimen is prepared and formed; the extended part of the asphalt concrete specimen 11 remaining outside the two pressure bearing supports 14 is equal in length, and the asphalt concrete specimen 11 is supported by the two pressure bearing supports 14;

[0104] Step S5, adjusting the positions of the displacement sensor 13, the temperature sensor 17 and the load sensor 8 relative to the asphalt concrete specimen 11:

[0105] A displacement sensor 13 is placed between the two pressure bearing supports 14 below the asphalt concrete specimen 11. The displacement sensor 13 is fixed to the pressure bearing base plate 15 by a magnetic table base 12, so that the probe of the displacement sensor 13 is located at the exact center of the lower edge of the cross section in the middle of the specimen. The effective range of the displacement sensor 13 is greater than 1.2 times the maximum deflection of the specimen expected in the test.

[0106] The temperature sensor 17 is arranged near the asphalt concrete specimen 11 and cannot touch the specimen during the test;

[0107] The load sensor 8 is located at the center of the upper part of the asphalt concrete specimen 11, and the pressure head 10 is in contact with the upper surface of the asphalt concrete specimen 11;

[0108] Recording the initial indications of the load sensor 8 and the displacement sensor 13;

[0109] Step S6, close the high and low temperature box door, start the constant temperature device, and maintain the constant temperature at the specified test temperature for 30 minutes;

[0110] Step S7, start the beam bending tester, control the loading according to the required deformation (mid-span displacement) rate (such as 0.01 mm / s, 0.1 mm / s, 1 mm / s), and transmit the collected signals by the load sensor 8 and the displacement sensor 13 to the computer data acquisition system 19 to draw a load-displacement curve;

[0111] When the specimen is destroyed, the computer prints out the specimen number, temperature, failure load and failure displacement; the failure load is the peak point of the load-displacement curve, and its corresponding displacement coordinate value is the failure displacement value;

[0112] Step S8, assuming that the failure load at the mid-span of the asphalt concrete specimen 11 when it fails is F B (N), the clear span length is L (mm), the specimen section dimensions are width b (mm), height h (mm), length L′ (mm); the failure displacement is d; the specimen force diagram is shown in Figure 2 .

[0113] The failure stress σ of the specimen is obtained using the following formula: B 、Failure strain ε B and breaking stiffness S B :

[0114]

[0115] Step S9: a group of asphalt concrete test pieces 11 has a plurality of, for example, three; the asphalt concrete test pieces 11 in the same group are tested in sequence; and the obtained failure stress σ B 、Failure strain ε B and breaking stiffness S B Identify and process outliers, and make selections and additions based on the deviation of the test data, and finally obtain a set of failure stress σ B 、Failure strain ε B and breaking stiffness S B , as the final test result.

[0116] The present invention can measure the bending stress, bending strain and bending stiffness of asphalt concrete specimens at different constant temperatures of -70°C to 100°C and different deformation rates, and is used to study the flexibility and deformation capacity of asphalt concrete specimens, and the stress and strain states under loaded bending conditions.

[0117] The working mechanism of the present invention is generally described as follows: the small beam bending test machine is a test machine that uses a servo motor to control the rising speed of the lead screw to control the deformation rate in the mid-span, and uses upper and lower connecting parts to limit the loading direction to vertically downward. During the test, the load borne by the specimen in the mid-span is measured by a load sensor, and the displacement (i.e., deflection) of the center position of the lower edge of the specimen in the mid-span is measured by a displacement sensor fixed on the bottom plate of the test machine. During the test, the load and deflection at different time intervals are automatically collected, and the bending stress, bending strain, and bending stiffness of the specimen at the time of failure are calculated using the load borne by the mid-span when the specimen is destroyed, the displacement of the center position of the lower edge of the mid-span, and the clear span length, width, and height of the specimen, thereby completing the small beam bending test.

[0118] Therefore, the present invention is used in combination with a temperature sensor, a load sensor, a displacement sensor, a magnetic table, a control cabinet and a computer data acquisition system to form a small beam bending test device. At a constant test temperature, a small beam bending test is performed on a beam-type specimen prepared and formed by an asphalt concrete material at a specified deformation rate to obtain the mid-span load, mid-span displacement, bending stress, bending strain, bending stiffness borne by the specimen at different time intervals, and the failure stress, failure strain, and failure stiffness when the specimen is destroyed. The specimen prepared and formed by the asphalt concrete material is prismatic in shape, with dimensions of 250±2mm, 30±2mm in width, and 35±2mm in height. In the test, the deformation (mid-span displacement) rate is controlled by controlling the rising speed of the screw with a servo motor, the load reading is recorded by a load sensor, and the displacement sensor is placed and fixed between the two pressure-bearing supports on the bottom plate using a magnetic base. The probe is vertically upward and in contact with the center of the lower edge of the cross-section in the middle of the vertical length direction of the specimen. The mid-span deflection of the specimen at different time intervals is obtained by measuring and recording the readings of the displacement sensor, and then the bending stress, bending strain, bending stiffness of the specimen and the failure stress, failure deflection and failure stiffness of the specimen when the specimen is destroyed are calculated.

[0119] The embodiments described above are only used to illustrate the technical ideas and features of the present invention, and their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. The patent scope of the present invention cannot be limited only by this embodiment, that is, any equivalent changes or modifications made to the spirit disclosed by the present invention still fall within the patent scope of the present invention.

Claims

1. A split asphalt concrete beam bending test device particularly suitable for high and low temperature boxes, characterized in that: include: A beam bending test machine, a load sensor (8), a displacement sensor (13), a temperature sensor (17), a control cabinet (18) and a computer data acquisition system (19); An asphalt concrete specimen (11) is placed in the small beam bending test machine; the small beam bending test machine is used to perform a small beam bending test on the asphalt concrete specimen (11), so that the specimen (11) undergoes mid-span deformation at a designed deformation rate; The load sensor (8) is located at the center of the upper part of the asphalt concrete specimen (11) and is used to collect the mid-span load of the asphalt concrete specimen (11); the displacement sensor (13) is located at the center of the lower edge of the mid-span of the asphalt concrete specimen (11) and is in contact with the bottom surface of the asphalt concrete specimen (11) and is used to collect the mid-span displacement at the center of the lower edge of the mid-span of the asphalt concrete specimen (11), that is, the mid-span deflection; the temperature sensor (17) is arranged near the asphalt concrete specimen (11) and is used to collect the temperature of the asphalt concrete specimen (11) during the small beam bending test; The load sensor (8), the displacement sensor (13) and the temperature sensor (17) are all connected to one end of the control cabinet (18); the other end of the control cabinet (18) is connected to the computer data acquisition system (19).

2. A split asphalt concrete beam bending test device particularly suitable for a high and low temperature box according to claim 1, characterized in that: The beam bending test machine comprises a test main machine, a loading component and a load-bearing component; The test host comprises a horizontally arranged top plate (1), a horizontally arranged bottom plate (2), a vertically arranged cylinder (3) connecting the top plate (1) and the bottom plate (2), and a servo motor screw lift (16); the servo motor screw lift (16) is installed above the bottom plate (2); The loading assembly is arranged above the asphalt concrete specimen (11), and comprises an upper connecting member (7), a lower connecting member (9) and a pressure head (10); the upper connecting member (7) is arranged vertically and is located directly above the center of the asphalt concrete specimen (11); the upper part of the upper connecting member (7) passes through the mounting through hole in the center of the top plate (1) and is locked with the top plate (1) through a nut (5) and a metal gasket (6); the bottom end of the upper connecting member (7) is connected to the upper part of the load sensor (8); the lower connecting member (9) and the upper connecting member (7) are arranged coaxially above and below; the upper part of the lower connecting member (9) is connected to the bottom end of the load sensor (8), and the bottom end of the lower connecting member (9) is connected to the pressure head (10); the pressure head (10) is a plate-like structure, and the lower end of the cross section of the pressure head (10) is a semicircular arc and contacts the upper surface of the asphalt concrete specimen (11); The load-bearing assembly is arranged below the asphalt concrete specimen (11), and comprises a pressure-bearing support (14) and a pressure-bearing bottom plate (15); the pressure-bearing bottom plate (15) is arranged horizontally and is connected and fixed to the top flange of the servo motor screw lift (16) located below it by bolts; a pair of pressure-bearing supports (14) arranged opposite to each other and used for supporting the asphalt concrete specimen (11) are vertically fixed on the pressure-bearing bottom plate (15); Driven by the servo motor screw lift (16), the load-bearing assembly formed by the pressure-bearing support (14) and the pressure-bearing base plate (15) moves upward, and under the joint action of the loading assembly, force is applied to the upper surface of the asphalt concrete specimen (11).

3. A split asphalt concrete beam bending test device particularly suitable for a high and low temperature box according to claim 2, characterized in that: The pressure bearing support (14) is a plate-shaped pressure bearing support, the upper end of the cross section of the pressure bearing support (14) is semicircular, and the distance between the two pressure bearing supports (14) matches the length of the asphalt concrete specimen (11) to be tested.

4. A split asphalt concrete beam bending test device particularly suitable for a high and low temperature box according to claim 2, characterized in that: A magnetic meter base (12) is placed on the pressure-bearing bottom plate (15), and the displacement sensor (13) and the temperature sensor (17) are installed on the magnetic meter base (12).

5. The split asphalt concrete beam bending test device particularly suitable for a high and low temperature box according to claim 2, characterized in that: The top plate (1) and the bottom plate (2) are respectively provided with through holes at their four corners, and the upper and lower ends of the cylinder (3) are respectively provided with threads. The top plate (1) and the bottom plate (2) are fixed to the upper and lower ends of the cylinder (3) by means of large nuts (4), thereby assembling the top plate (1), the bottom plate (2) and the cylinder (3) to form a whole.

6. The split asphalt concrete beam bending test device particularly suitable for a high and low temperature box according to claim 2, characterized in that: The four corners of the base of the servo motor screw lift (16) are provided with through holes, and the corresponding positions of the base plate (2) are provided with through holes, and the servo motor screw lift (16) is connected and installed on the base plate (2) by bolts and nuts.

7. The split asphalt concrete beam bending test device particularly suitable for a high and low temperature box according to claim 2, characterized in that: The upper connecting member (7) and the load sensor (8), the load sensor (8) and the lower connecting member (9), and the lower connecting member (9) and the pressure head (10) are respectively connected by threads.

8. The split asphalt concrete beam bending test device particularly suitable for a high and low temperature box according to claim 2, characterized in that: The pressure bearing support (14) and the pressure bearing base plate (15), and the pressure bearing base plate (15) and the flange at the top end of the servo motor screw lift (16) are respectively connected by bolt threads.

9. The split asphalt concrete beam bending test device particularly suitable for a high and low temperature box according to claim 1, characterized in that: The temperature sensor (17) is a low-temperature resistant sensor, which can work for a long time in an environment of -70°C to 100°C, has a measuring range of -150°C to 150°C, and a minimum graduation value of 0.1°C; The load sensor (8) is an ultra-low temperature force sensor with internal threads at both ends, which can work for a long time in an environment of -70°C to 100°C, has a measuring range of 10kN, a minimum graduation value of 0.01kN, and can measure tension, pressure, and tension-pressure; The displacement sensor (13) is a low-temperature resistant displacement sensor, capable of operating for a long time in an environment of -70°C to 100°C, with a measuring range of 100 mm and a minimum graduation value of 0.01 mm; The servo motor used in the servo motor screw lift (16) is a low-temperature resistant servo motor and can work for a long time in an environment of -70°C to 100°C.

10. A method for performing a beam bending test using a split asphalt concrete beam bending test device particularly suitable for a high and low temperature chamber as described in any one of claims 1 to 9, characterized in that: The following steps are involved: Step S1, placing the test main machine of the beam bending test machine into a high and low temperature box, connecting the test main machine, the loading component, and the load-bearing component of the beam bending test machine to obtain the beam bending test machine, and adjusting the bottom plate (2) and the top plate (1) to a horizontal state; Step S2, placing the load sensor (8), the displacement sensor (13), and the temperature sensor (17) in a high and low temperature box, and connecting the beam bending tester, the load sensor (8), the displacement sensor (13), the temperature sensor (17), the control cabinet (18), and the computer data acquisition system (19); Step S3, placing the asphalt concrete specimen (11) on frosted glass coated with talcum powder in a high and low temperature box, and adjusting the high and low temperature box to the test temperature, and keeping the temperature constant for 3-5 hours, at which time the small beam bending test machine and the interior of the asphalt concrete specimen (11) both reach the specified test temperature; Step S4, quickly open the high and low temperature box, and symmetrically place the asphalt concrete specimen (11) on the pressure bearing support (14) of the small beam bending tester, the up and down direction of the asphalt concrete specimen (11) is consistent with the direction when the specimen is prepared and formed; the extended parts of the asphalt concrete specimen (11) remaining outside the two pressure bearing supports (14) are equal in length, and the asphalt concrete specimen (11) is supported by the two pressure bearing supports (14); Step S5, adjusting the positions of the displacement sensor (13), the temperature sensor (17) and the load sensor (8) relative to the asphalt concrete specimen (11): A displacement sensor (13) is placed between the two pressure bearing supports (14) below the asphalt concrete specimen (11); the displacement sensor (13) is fixed to the pressure bearing base plate (15) by a magnetic table base (12) so that the probe of the displacement sensor (13) is located at the exact center of the lower edge of the cross section in the middle of the specimen; the effective range of the displacement sensor (13) is greater than 1.2 times the maximum deflection of the specimen expected in the test; The temperature sensor (17) is arranged near the asphalt concrete test piece (11) and cannot touch the test piece during the test; The load sensor (8) is located at the center of the upper part of the asphalt concrete specimen (11), and the pressure head (10) is in contact with the upper surface of the asphalt concrete specimen (11); Recording the initial indications of the load sensor (8) and the displacement sensor (13); Step S6, close the high and low temperature box door, start the constant temperature device, and maintain the constant temperature at the specified test temperature for 30 minutes; Step S7, start the beam bending test machine, control the loading according to the required deformation rate, and transmit the collected signals to the computer data acquisition system (19) by the load sensor (8) and the displacement sensor (13), and draw a load-displacement curve; When the specimen is destroyed, the computer prints out the specimen number, temperature, failure load and failure displacement; the failure load is the peak point of the load-displacement curve, and its corresponding displacement coordinate value is the failure displacement value; Step S8, assuming that the failure load at the mid-span of the asphalt concrete specimen (11) when it fails is F B , the clear span length is L, the specimen section dimensions are width b, height h, length L′; the failure displacement is d; The failure stress σ of the specimen is obtained using the following formula: B 、Failure strain ε B and breaking stiffness S B : Step S9, a group of asphalt concrete test pieces (11) is a plurality of pieces; the asphalt concrete test pieces (11) in the same group are tested in sequence; the obtained failure stress σ B 、Failure strain ε B and breaking stiffness S B After outlier identification and processing, a set of failure stress σ is finally obtained. B 、Failure strain ε B and breaking stiffness S B , as the final test result.

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