CN115200973A - Bituminous mixture two-way tension-compression equal proportion loading intensity experimental apparatus - Google Patents

Abstract

The invention discloses a bidirectional tension-compression equal-proportion loading strength experimental device for an asphalt mixture, which comprises a bottom plate, wherein a groove is formed in the bottom plate, an asphalt mixture test piece is arranged in the groove, and a lifting device is arranged at the lower end of the groove; an upper cover plate is arranged above the bituminous mixture trial-made piece, and when the upper cover plate is used for pressing the bituminous mixture trial-made piece, the upper cover plate moves downwards to be under the action of the linkage piece and on the pull rod so as to transversely pull the bituminous mixture trial-made piece; the pull rod is arranged on the slide rail, the support rod is inserted in the upper cover plate, and the middle of the upper end of the upper cover plate is provided with a pressing force application part. The device is ingenious in design, the asphalt mixture test piece can be simultaneously pulled and pressed, and vertical force application enables the asphalt mixture test piece to be transversely pulled through the linkage piece, namely the asphalt mixture test piece is simultaneously subjected to loads in two different directions, and is vertically pressed and transversely pulled; and the size of the linkage piece is changed, so that the transverse tension is changed, and the effect of changing the compression-tension stress ratio is achieved.

Description

An experimental device for bidirectional tensile and compressive equal-proportional loading strength of asphalt mixture

technical field

The invention relates to the relevant technical field of asphalt mixtures, in particular to an experimental device for bidirectional tension-compression equal-proportion loading strength of asphalt mixtures.

Background technique

Most of the high-grade highways in our country use asphalt pavement. Asphalt pavement is exposed to the external environment for a long time and is subjected to the repeated action of wheel loads. It is in a complex stress state for a long time. The structural strength of the pavement will also decrease with the increase of the number of repeated loads. Because the asphalt pavement is under the action of the wheel load, the road surface presents a stress state in which the two-way tension-compression acts simultaneously. In the existing asphalt mixture strength test method, the asphalt mixture specimen for splitting strength test is in a two-dimensional stress state. However, the traditional splitting strength test has the following deficiencies: First, the edge of the fixture that applies pressure will definitely crack first, which is inconsistent with the assumption of the splitting strength calculation formula (it assumes that the center of the specimen will crack first); second, the asphalt mixture The bidirectional stress ratio at the center of the specimen is fixed, which cannot reflect the actual changeable bidirectional stress ratio of the road surface.

Patent No. 1 publication (announcement): CN201110404400.5, applicant (patent right): South China University of Technology. The abstract of this patent is as follows: The present invention provides a fixture and a test method for a bidirectional alternate splitting test of a cylindrical specimen of road materials. The fixture includes a front-end surface unit and a rear-end surface unit with the same structure and spaced apart, and a gap between the two end surface units. The front-end surface unit and the rear-end surface unit each include an upper wing plate, a lower wing plate, and eight connecting plates; the connecting parts include an upper pressure strip, a lower pressure strip, a side pressure strip, a top plate and a bottom plate. After the fixture is fixed, it is connected to the loading device; then the cylindrical specimen is placed in the fixture, so that both ends of the specimen are vacated by equal distances; compressive and tensile loads are cyclically applied in the vertical direction of the fixture top plate, The specimen is deformed in tension and compression, and the results of the bidirectional splitting fatigue test with alternating tension and compression are obtained. The fixture realizes the alternate compression-tensile loading of the specimen in the vertical and horizontal directions, obtains the actual fatigue resistance of the pavement material under the loading condition, and can be used to study the propagation and healing laws of internal cracks in the material.

The patent in the comparison document is the alternate compressive-tensile loading in the vertical and horizontal directions of the specimen (at any time, only one direction is loaded), and the compressive-tensile stress ratio is fixed, which belongs to a kind of fatigue test equipment, which cannot be achieved. The asphalt mixture specimen is subjected to bidirectional tensile and compressive loads at the same time, and it cannot guarantee that the center of the specimen will crack first. The reference documents do not disclose the technical solution of the patent, which cannot destroy the novelty of the patent, and the combination of the above reference documents cannot destroy the inventiveness of the patent.

SUMMARY OF THE INVENTION

The purpose of the present invention is to solve the above problems, to provide a bidirectional tension-compression equal-proportional loading strength test device for asphalt mixture, which is ingeniously designed, can simultaneously tension and compress the asphalt mixture sample, and apply vertical force through the linkage to make the lateral tension , that is, subjected to loads in two different directions at the same time, vertically compressed and laterally stretched; and by changing the size of the linkage, the lateral tensile force is changed, so as to achieve the effect of changing the compression-tension stress ratio.

In order to achieve the above purpose, the technical scheme adopted in the present invention is as follows: it comprises a bottom plate, a groove is arranged on the bottom plate, an asphalt mixture trial piece is arranged in the groove, and a lifting device is arranged at the lower end of the groove; The upper cover is provided with an upper cover, and the lower sides of the upper cover are provided with a tie rod for pressing the asphalt mixture test piece. The pull rod is arranged on the sliding rail, the upper cover plate is interspersed with a second support rod, and the middle part of the upper end of the upper cover plate is provided with a downward pressure applying part.

Further, the linkage member is configured as a connecting rod hingedly connected with the upper cover plate and the pull rod respectively.

Further, one end of the tie rod is connected with the asphalt mixture trial piece through a connecting block, and the other end of the tie rod is provided with a limiting block.

Further, the linkage includes a first rack, the first rack is meshed with the first gear, the side end of the first gear is meshed with the second gear, the lower end of the second gear is meshed with the third gear, the third gear The lower end of the gear is engaged with the second rack.

Further, the upper end of the first rack is arranged on both sides of the lower end of the upper cover plate; the second gear, the third gear and the first gear are respectively arranged on the bottom plate through the first vertical rod, the second vertical rod and the connecting shaft; The two racks are arranged in the groove of the tie rod.

Further, both ends of the upper cover plate are provided with notches to prevent interference with the first gear.

Further, the asphalt mixture trial piece is a cylinder with four sides cut with a knife, and the two sides of the asphalt mixture trial piece are connected with the connecting block by sticking.

Further, the pull rod is composed of a first pull rod main body and a second pull rod main body, and one ends of the first pull rod main body and the second pull rod main body are respectively arranged in a screw sleeve.

Further, the lower end of the slide rail is provided with a first support rod, and the lower end of the first support rod is set on the bottom plate.

Beneficial effects of the present invention:

1. The present invention provides a bidirectional tension-compression equal-proportion loading strength test device for asphalt mixture, which is ingeniously designed, and can simultaneously tension and compress the asphalt mixture sample, and the vertical force is applied through the linkage to make the lateral tension, that is, it is subjected to two simultaneous tensions. Loads in different directions are vertically compressed and laterally stretched; and by changing the size of the linkage, the lateral tension is changed, so as to achieve the effect of changing the compression-tension stress ratio.

2. In the present invention, the lateral tensile force of the test piece of asphalt mixture is derived from the vertical pressure of the test piece (the direction and size are changed by the linkage), and the bidirectional load is loaded in equal proportions; It simulates the scene of the real wheel rolling over the road.

3. In the present invention, by cutting the asphalt mixture sample, four planes for directly bearing the load are obtained, thereby achieving the effect of ensuring that the center of the sample is cracked first.

Description of drawings

FIG. 1 is a front view when the linkage member is a connecting rod in the structure of the present invention.

FIG. 2 is a top view when the linkage member is a connecting rod in the structure of the present invention.

Fig. 3 is a front view of the structure of the present invention when the linkage member is a rack and pinion.

FIG. 4 is a top view when the linkage member is a rack and pinion in the structure of the present invention.

FIG. 5 is a schematic diagram of the upper cover plate when the linkage is a rack and pinion.

FIG. 6 is a schematic diagram of the connection between the tie rod and the screw sleeve in the structure of the present invention.

FIG. 7 is a schematic diagram of the asphalt mixture trial piece in the structure of the present invention after cutting.

The text in the figure is marked as: 1. Bottom plate; 2. First support rod; 3. Limit block; 4. Pull rod; 5. Slide rail; 6. Third gear; 7. Second gear; 8. First a gear; 9, the second support rod; 10, the upper cover plate; 11, the first rack; 12, the asphalt mixture prototype; 13, the connecting block; 14, the screw sleeve; 15, the second rack; 16, 17, connecting rod; 18, second rigid rod; 101, groove; 401, first tie rod main body; 402, second tie rod main body; 1001, incision.

Detailed ways

In order to make those skilled in the art better understand the technical solutions of the present invention, the present invention will be described in detail below with reference to the accompanying drawings. The description in this part is only exemplary and explanatory, and should not have any limiting effect on the protection scope of the present invention. .

As shown in FIG. 1-FIG. 7, the specific structure of the present invention is as follows: it includes a bottom plate 1, a groove 101 is provided on the bottom plate 1, an asphalt mixture trial piece 12 is provided in the groove 101, and the lower end of the groove 101 is provided with a Lifting device; an upper cover plate 10 is arranged above the asphalt mixture trial piece 12, and both sides below the upper cover plate 10 are provided for pressing the asphalt mixture trial piece 12. When the upper cover plate 10 moves down on the linkage Under the action of the tie rod 4, a lateral tension force that realizes the bidirectional load equal-proportion loading is generated on the tie rod 4; The upper cover plate 10 is provided with a downward pressure applying portion in the middle portion of the upper end. The downward pressure applying part is an MTS press.

Working principle: First, fix the tie rods 4 on both sides and the asphalt mixture prototype 12 on the outside, and then install them into the groove 101 on the bottom plate 1 of the experimental device; when pressure is applied to the middle of the upper cover plate 10, the upper cover plate 10 Under the action of the linkage, the pull rod 4 pulls the asphalt mixture test piece 12 laterally; the pull rod 4 slides on the slide rail 5, so that the compression and tension of the asphalt mixture test piece 12 can be detected. pressure ratio.

As shown in FIG. 3-FIG. 4, the linkage includes a first rack 11, the first rack 11 is meshed with the first gear 8, the side end of the first gear 8 is meshed with the second gear 7, and the second gear 7 The lower end of the gear 6 is engaged with the third gear 6 , and the lower end of the third gear 6 is engaged with the second rack 15 . The upper end of the first rack 11 is arranged on both sides of the lower end of the upper cover plate 10; the second gear 7, the third gear 6 and the first gear 8 are respectively arranged on the bottom plate through the first vertical rod 16, the second vertical rod 18 and the connecting shaft. 1; the second rack 15 is arranged in the groove of the pull rod 4. Both ends of the upper cover plate 10 are provided with notches 1001 for preventing interference with the first gear 8 .

As shown in FIGS. 1-2 , the linkage members are provided as connecting rods 17 hingedly connected with the upper cover 10 and the pull rod 4 respectively.

Table 1 below shows the ratio of compressive and tensile stress at the center of the asphalt mixture specimen under different combinations of vertical pressure and transverse tensile force (for ease of expression, the following refers to the absolute value of this ratio):

Table 1

Pressure: Pull 1:1 1:0.75 1:0.5 1:0.25 1: 0.125 Compression and tensile stress ratio at the center of the circle 1:1 1.2:1 1.52:1 2.33:1 2.73:1

When the asphalt mixture specimen of the aforementioned shape (diameter 100mm, thickness 35mm) is only compressed vertically (Y direction) (size is F), the compressive stress at the center of the specimen is obtained through finite element calculation: tensile stress= 4.7; Assuming that its transverse (X-direction) tensile stress is σ, its Y-direction compressive stress is -4.7 σ.

When the above-mentioned specimen is only subjected to tensile force (the size is F) in the X direction, according to the simple analysis of elastic mechanics, its transverse (X direction) tensile stress is 4.7σ, and its Y direction compressive stress is -σ.

When the specimen is subjected to both vertical compression and lateral tension, if the magnitude of the load in the two directions is equal, according to the superposition principle of elastic mechanics, the compressive stress at the center of the specimen can be obtained: tensile stress=5.7σ: 5.7σ=1

In the same way, when the ratio of the vertical pressure on the specimen to the lateral tensile force is k, according to the superposition principle of elastic mechanics, the compressive stress at the center of the specimen can be obtained: tensile stress = (4.7+k)σ: (1+4.7k)σ=(4.7+k)/(1+4.7k)

The present invention obtains different k values through the linkage. When a gear is used as the linkage, for example, when the radius of the first gear 8: the radius of the second gear 7: the radius of the third gear 6 is 1:1:1, The value of k is 1; when the connecting rod is used as the linkage, for example, when the angle of the connecting rod 17 is 30°, the value of k is 0.5.

As shown in Figures 1 and 3, one end of the tie rod 4 is connected to the asphalt mixture trial product 12 through a connecting block 13, and the other end of the tie rod 4 is provided with a limiting block 3. The asphalt mixture test piece 12 and the connecting block 13 are bonded and connected.

As shown in FIG. 5 , the pull rod 4 is composed of a first pull rod body 401 and a second pull rod body 402 . One ends of the first pull rod body 401 and the second pull rod body 402 are respectively disposed in the screw sleeve 14 . In specific use, firstly, the two side tie rods 4 and the asphalt mixture prototype 12 are fixed on the outside and then mounted on the experimental device. Therefore, in order to connect it with the two side tie rods, a screw sleeve 14 is designed for connection.

As shown in FIG. 1 and FIG. 3 , the lower end of the slide rail 5 is provided with a first support rod 2 , and the lower end of the first support rod 2 is provided on the bottom plate 1 .

The lower end of the groove 101 is provided with a lifting device. This structural design is due to the fact that the production of the test piece cannot be guaranteed to be accurate to 1mm, so a lifting device is set at the bottom for fine-tuning to ensure that the test piece is in the center of the entire device and the tension on both sides is guaranteed. in the center of the specimen.

Among them, the asphalt mixture trial piece 12 is not cylindrical, as shown in Figure 7, the included angle α is 60 degrees when cutting, and it is a cylinder with four sides cut with a knife, and the thickness is 35mm.

Example 1:

(1) Test object: Modified asphalt AC-13 mixture with a diameter of 100 mm and a thickness of 35 mm, and cut it into the shape shown in Figure 7.

(2) Loading equipment: hydraulic servo material testing system MTS

(3) Test conditions: the temperature is 15 °C, the vertical loading rate is 4 kN/s, the connecting rod linkage is used for transmission, and the angle between the connecting rod and the horizontal plane is 30 °C.

(4) Test phenomenon: The strain gauge pasted at the center of the end face of the specimen fails first, and there is no stress concentration failure on the edge of the loading fixture at this time.

(5) Failure load: 13.47kN.

Example 2:

(1) Test object: Modified asphalt AC-13 mixture with a diameter of 100 mm and a thickness of 35 mm, and cut it into the shape shown in Figure 7.

(2) Loading equipment: hydraulic servo material testing system MTS

(3) Test conditions: the temperature is 15 °C, the vertical loading rate is 2 kN/s, the connecting rod linkage is used for transmission, and the angle between the connecting rod and the horizontal plane is 30 °C.

(4) Test phenomenon: The strain gauge pasted at the center of the end face of the specimen fails first, and there is no stress concentration failure on the edge of the loading fixture at this time.

(5) Failure load: 12.65kN.

Example 3:

(1) Test object: Modified asphalt AC-13 mixture with a diameter of 100 mm and a thickness of 35 mm, and cut it into the shape shown in Figure 7.

(2) Loading equipment: hydraulic servo material testing system MTS

(3) Test conditions: the temperature is 15°C, the vertical loading rate is 1kN/s, the connecting rod linkage is used for transmission, and the angle between the connecting rod and the horizontal plane is 45°C.

(4) Test phenomenon: The strain gauge pasted at the center of the end face of the specimen fails first, and there is no stress concentration failure on the edge of the loading fixture at this time.

(5) Failure load: 9.83kN.

It should be noted that, herein, the terms "comprising", "comprising" or any other variation thereof are intended to encompass non-exclusive inclusion, such that a process, method, article or device comprising a series of elements includes not only those elements, It also includes other elements not expressly listed or inherent to such a process, method, article or apparatus.

Specific examples are used herein to illustrate the principles and implementations of the present invention, and the descriptions of the above examples are only used to help understand the method and the core idea of the present invention. The above are only the preferred embodiments of the present invention. It should be pointed out that due to the limited expression of words, there are objectively unlimited specific structures. For those of ordinary skill in the art, without departing from the principles of the present invention However, some improvements, modifications or changes can also be made, and the above-mentioned technical features can also be combined in an appropriate manner; these improvements, modifications, or combinations, or the concept and technical solutions of the invention are directly applied to other occasions without improvement. should be regarded as the protection scope of the present invention.

Claims (9)

1. A two-way tension-compression equal-proportional loading strength experimental device for asphalt mixture, characterized in that it comprises a bottom plate (1), the bottom plate (1) is provided with a groove (101), and the groove (101) is provided with asphalt The mixture trial piece (12) is provided with a lifting device at the lower end of the groove (101); an upper cover plate (10) is arranged above the asphalt mixture trial piece (12), and the lower sides of the upper cover plate (10) are arranged on both sides When the asphalt mixture trial product (12) is subjected to vertical pressure, the downward movement of the upper cover plate (10) is on the tie rod (4) under the action of the linkage, so as to realize the realization of the asphalt mixture trial product (12). Two-way load equal-proportional lateral tension; the tie rod (4) is arranged on the slide rail (5), the upper cover plate (10) is interspersed with a second support rod (9), and the upper cover plate (10) is arranged in the middle of the upper end There is a pressing force section. 2. A kind of asphalt mixture bidirectional tension-compression equal-proportional loading strength test device according to claim 1, characterized in that, the linkage is arranged as a connecting rod hingedly connected with the upper cover plate (10) and the pull rod (4) respectively (17). 3 . The bidirectional tensile-compression equal-proportional loading strength test device for asphalt mixture according to claim 1 , wherein the linkage comprises a first rack (11), a first rack (11) and a first gear. 4 . (8) Mesh connection, the side end of the first gear (8) is meshed with the second gear (7), the lower end of the second gear (7) is meshed with the third gear (6), the third gear (6) The lower end is engaged with the second rack (15). 4. A kind of asphalt mixture bidirectional tension-compression equal-proportional loading strength test device according to claim 3, wherein the upper end of the first rack (11) is arranged on both sides of the lower end of the upper cover plate (10); The second gear (7), the third gear (6) and the first gear (8) are respectively arranged on the bottom plate (1) through the first vertical rod (16), the second vertical rod (18) and the connecting shaft; The rack (15) is arranged in the groove of the tie rod (4). 5. A kind of double-way tension-compression equal-proportional loading strength test device for asphalt mixture according to claim 4, characterized in that, both ends of the upper cover plate (10) are provided with notches to prevent interference with the first gear (8) (1001). 6. A kind of asphalt mixture bidirectional tension-compression equal-proportional loading strength test device according to claim 1, characterized in that, one end of the tie rod (4) is connected with the asphalt mixture trial piece (12) through a connecting block (13) , the other end of the pull rod (4) is provided with a limiting block (3). 7. A kind of asphalt mixture bidirectional tensile and compressive equal-proportional loading strength experimental device according to claim 6, characterized in that, the asphalt mixture trial piece (12) is a cylinder, and it is necessary to cut a knife on each of its four sides, and the asphalt mixture The two sides of the trial product (12) are connected with the connecting block (13) by adhesive bonding. 8 . The bidirectional tension-compression equal-proportional loading strength test device for asphalt mixture according to claim 1 , wherein the tie rod (4) is composed of a first tie rod main body (401) and a second tie rod main body (402), 9 . One ends of the first pull rod body (401) and the second pull rod body (402) are respectively disposed in the screw sleeve (14). 9. A kind of asphalt mixture bidirectional tension-compression equal-proportional loading strength test device according to claim 1, characterized in that, the lower end of the slide rail (5) is provided with a first support rod (2), and the first support rod ( The lower end of 2) is arranged on the bottom plate (1).

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