CN108225895A - A kind of uniaxial rigidity stretched is with drawing device - Google Patents

Abstract

The present invention discloses a kind of uniaxial rigidity stretched with drawing device, including lower rigid plate, it is fixedly connected with more rigidity thereon with component is drawn, rigidity companion draws and is fixedly connected with rigid plate above component, is respectively fixed in upper rigid plate and lower rigid plate and stretches clamping bar and lower stretching clamping bar；Test specimen upper junction plate and test specimen lower connecting plate are further included, test specimen lower connecting plate is fixed in lower rigid plate, and test specimen upper junction plate is connected with lower transmission rod, pull pressure sensor and upper force transferring part and is fixed in upper rigid plate；Wherein, every rigidity companion draws component to include two be fixedly connected respectively with upper rigid plate, lower rigid plate rigidity with pull rod and connect the two rigid replaceable tensile parts with pull rods；Testing machine is clamped the upper and lower clamping bar that stretches and is stretched, the rigidity that single shaft stretches is with drawing device stress deformation together with test specimen, after test piece deformation is more than peak strain, because rigidity is with the presence for drawing component, the stiffness variation of single unit system is faint, at this time the release very little of testing machine elasticity energy.

Description

A Rigid Accompanying Device for Uniaxial Stretching

technical field

The invention relates to a rigid loading device, in particular to a uniaxial stretching rigid accompanying tension device, which belongs to the technical field of civil engineering.

Background technique

When performing uniaxial tensile tests on brittle materials such as concrete and rocks, due to the deformation of the steel frame of the testing machine and the compression deformation of the pressure oil in the hydraulic cylinder in the ordinary testing machine, a large elastic energy is stored, which will cause the test piece to After reaching the ultimate strength, brittle fracture occurs, and it is impossible to carry out test research on cracks in the subsequent softening stage.

At present, the ways to solve this kind of problems mainly adopt (1) rigid testing machine (2) rigid testing frame (3) closed-loop electro-hydraulic servo testing machine. Among them, the rigid test frame is widely used because it is suitable for most mechanical testing machines and the test cost is low, but there are also the following problems in use: (1) The test results of the softening stage after the peak stress of the brittle test piece are affected by The stiffness of the test device has a great influence; (2) the ultimate tensile strain of brittle specimens such as concrete and rock is very small, and whether the tension is centered or not has a great influence on the results, so the installation of the specimen before stretching has a great influence on the test results. The device has higher requirements.

Contents of the invention

Purpose of the invention: In order to overcome the problem that the existing common testing machine is easy to cause brittle fracture of the test piece and cannot perform the test on the descending section of the stress-strain curve of the test piece, the present invention provides a rigid accompanying tension device for uniaxial tension. components, greatly reducing the release of the elastic energy of the testing machine.

Technical solution: A uniaxially stretched rigid companion pull device according to the present invention includes a lower rigid plate on which a plurality of rigid companion pull components are fixedly connected, and an upper rigid plate is fixedly connected above the rigid companion pull components, and the upper rigid plate The rigid plate and the lower rigid plate are respectively fixed with an upper tensile clamp bar and a lower tensile clamp bar; it also includes an upper connecting plate and a lower connecting plate of the test piece, the lower connecting plate of the test piece is fixed on the lower rigid plate, and the upper connecting plate of the test piece is fixed on the lower rigid plate. The connecting plate, the lower dowel bar, the tension pressure sensor and the upper force component are fixed in series on the upper rigid plate; wherein, each companion pull component includes two rigid tie rods fixedly connected to the upper rigid plate and the lower rigid plate respectively and the connection The replaceable tensile parts of the two rigid accompanying pull rods; the testing machine clamps the upper and lower tensile clamping rods for stretching, and the rigid accompanying pulling device of uniaxial stretching of the present invention is deformed under force together with the test piece. After the deformation exceeds the peak strain, the stiffness of the overall device changes slightly due to the existence of rigid accompanying tension components, and the release of elastic energy is very small at this time.

Preferably, the surface of the rigid accompanying tie rod is threaded, the upper rigid plate and the lower rigid plate are provided with holes matching the size of the rigid accompanying tie rod, and the rigid accompanying tie rod and the upper rigid plate and the lower rigid plate are fixed by pre-tightening bolts. On the one hand, it can facilitate the centering and fixed installation of the rigid accompanying tie rod. On the other hand, this fixing method can realize the rough adjustment of the gap of the device to adapt to different specimen sizes.

Further, the surface of the replaceable tensile part is threaded, and the rigid accompanying tie rod is provided with a screw hole matching the size of the replaceable tensile part, and the two are fixed by pre-tightening bolts. It is also convenient for the centering and fixed installation of the replaceable tensile parts, and further fine-tuning of the device gap can be realized to reduce the impact of the size deviation of the test piece.

In addition, in order to facilitate the centering of the test piece, the upper connecting plate and the lower connecting plate of the test piece can be respectively provided with grooves adapted to the upper and lower ends of the test piece. , the groove can ensure that the structural adhesive is fully bonded to the specimen.

In order to reduce the impact of stiffness degradation in the softening stage of the test piece on the overall stiffness of the system, the stiffness _K of the rigid accompanying tension device of uniaxial tension of the present invention should meet the following conditions:

And K _T ≥ 5K _C ;

In the formula, K _A1 represents the total stiffness of multiple rigid companion tension components, and K _A2 represents the total stiffness of replaceable tensile parts in multiple rigid companion tension components, both of which can be expressed by the formula To calculate, E _A is the elastic modulus of the material, A _A is the corresponding cross-sectional area of the rigid tie rod or the replaceable tensile part, l _A is the corresponding effective load-bearing length of the rigid tie rod or the replaceable tensile part; K _B represents the converted stiffness obtained after considering the stiffness loss at the connection position of each component on the basis of the series stiffness of the tension pressure sensor and the upper connecting plate, upper force component, and lower force bar of the test piece connected to it; K _C represents the stiffness to be The stiffness of the tensile specimen.

Further, the ratio of _KB to _KC should be at least greater than 5, so as to reduce the influence of the release of this part of elastic energy on the test piece.

Beneficial effects: Compared with the prior art, the remarkable advantages of the present invention are: (1) The uniaxially stretched rigid companion device of the present invention adopts a rigid companion composed of a rigid companion rod and a replaceable stretch rod. Pull assembly, during the rigid loading test, can greatly reduce the release of the elastic energy of the testing machine; moreover, the tensile stiffness of the device can be changed to adapt to different tensile test pieces and different stiffness change requirements; (2) the present invention The rigid accompanying tension device for uniaxial tension considers the need for gap adjustment, can adapt to different specimen sizes, and at the same time reduces the influence of specimen size deviation on the test; (3) the rigid accompanying tension device for uniaxial tension The connection position of each component is designed with suitable grooves or holes, which facilitates the installation of the system, facilitates the centering of the tensile test piece, and reduces the possibility of the system loading the test piece eccentrically.

Description of drawings

Fig. 1 is the perspective view of the rigid accompanying pull device of uniaxial stretching of the present invention;

Fig. 2 is the side view of the rigid accompanying pull device of uniaxial stretching of the present invention;

Fig. 3 is the plan view of the rigid accompanying pull device of uniaxial stretching of the present invention;

Fig. 4 is A-A sectional view;

Fig. 5 is a schematic diagram of a simplified stiffness model of the uniaxially stretched rigid accompanying tension device of the present invention.

Detailed ways

The technical solution of the present invention will be further described below in conjunction with the accompanying drawings.

As shown in Figures 1 to 4, a uniaxially stretched rigid accompanying pull device of the present invention includes a lower rigid plate 1, on which a plurality of rigid accompanying pull components are fixedly connected, and an upper rigid plate 10 is fixedly connected above the rigid accompanying pull components; Wherein, each set of rigid accompanying tie rods 3 includes two rigid accompanying tie rods 3 and a replaceable tensile member 4 connecting the two rigid accompanying tie rods 3, wherein the two rigid accompanying tie rods 3 are connected with the upper rigid plate 10 and the lower rigid plate 1 respectively. Fixed connection.

The rigid accompanying tension device for uniaxial tension also includes a specimen fixing part for fixing the tensile specimen 5, which includes an upper connecting plate 6 and a lower connecting plate 2 of the test piece, and the lower connecting plate 2 of the test piece can be obtained by the method The blue blind plate is processed, and the bolts are fixed on the lower rigid plate 1; the upper connecting plate 6 of the test piece, the lower dowel bar 7, the tension pressure sensor 8 and the upper force component 9 are fixed in series on the upper rigid plate 10 in sequence, so that the The tensile test piece 5 is fixed in the load-bearing frame defined by the upper and lower rigid plates.

The rigid accompanying pull device of uniaxial stretching of the present invention also comprises two upper and lower stretch clamp rods 11, which are respectively fixed on the upper rigid board 10 and the lower rigid board 1, and the testing machine is clamping the upper and lower stretch clamp rods 11. Finally, stretch it, the uniaxially stretched rigid accompanying tension device is stretched together with the specimen, and after the deformation of the specimen exceeds the peak strain, the stiffness of the overall device changes slightly due to the existence of the rigid accompanying tension component. When the release of elastic energy is very small, it can avoid the brittle fracture of the specimen due to the large elastic energy. Moreover, since the rigid accompanying tension device of the present invention is designed with a replaceable tensile member 4, for tensile test pieces with different rigidities, replaceable pull rod members 4 with different rigidities can be used, thereby changing the tensile stiffness of the overall device, Make it adapt to the stiffness change requirements of tensile specimens.

In order to make the rigid accompanying tension device of uniaxial stretching of the present invention adaptable to test pieces of different sizes, threads can be set on the surface of the rigid accompanying tension rod 3 , and the upper rigid plate 10 and the lower rigid plate 1 are provided with rigid accompanying tension rods. 3 threaded holes with matching sizes, and the rigid accompanying tie rod 3 is fixed on the upper rigid plate 10 and the lower rigid plate 1 by pre-tightening bolts. This fixing method makes the distance between the upper rigid plate 10 and the lower rigid plate 1 adjustable, so as to realize the rough adjustment of the gap of the device, so as to adapt to different specimen sizes.

Simultaneously, the side that is connected with the replaceable tensile part 4 on the rigid companion tie rod 3 also can offer screw holes, and thread is set on the surface of the replaceable tensile part 4, and it is fixed on a pair of rigid companion by pre-tightening bolts. On the tie rod 3, the clearance of the device can be further fine-tuned, and the influence of the size deviation of the test piece can be reduced.

In order to facilitate the installation of the test piece 5, grooves can be arranged on the upper connecting plate 6 and the lower connecting plate 2 of the test piece, and the grooves are adapted to the size of the upper and lower ends of the test piece 5; in addition, the force uploading member 9 and The lower connecting plate 2 of the test piece is provided with threaded holes that can be fixed on the upper and lower rigid plates. After the test piece is fixed, the groove cores on the upper connecting plate 6 and the lower connecting plate 2 of the test piece are on the symmetrical axis of the tensile clamp rod, and the threaded holes on the force uploading member 9 and the lower connecting plate 2 of the test piece are evenly distributed Around the axis of symmetry of the tension clamp rod. This operation can facilitate the centering of the test piece and reduce the possibility of eccentric loading on the test piece. Moreover, when using structural glue to fix the test piece, it can ensure that the structural glue and the test piece are fully bonded.

Among them, the rigid tie rod 3, as the main component to improve the rigidity of the system, should adopt metal materials such as alloy steel with high elastic modulus. Within the range allowed by the test space and the weight of the test frame, according to the material of the tensile test piece, a large cross-section should be selected as much as possible. Rigid tie rods to improve system rigidity.

The replaceable tensile part 4 on the rigid tie rod 3 is generally cylindrical, and its diameter is selected according to the stiffness of the test piece, and is used as the main part to adjust the gap of the test device and the stiffness of the system. During the stretching process, it is necessary to ensure that the part is in a linear elastic working state for repeated use.

The upper and lower tensile clamping rods 11 should be made of high-strength materials to ensure that the diameter of the tensile clamping rods does not exceed the allowable range of the testing machine fixture, and the stress is in the elastic range during the stretching process.

The schematic diagram of the simplified rigidity model of the rigid accompanying tension device of uniaxial stretching of the present invention is shown in Fig. 5, wherein:

K _A1 represents the stiffness of the four sets of rigid accompanying tie rods 3, K _A2 represents the stiffness of the replaceable tensile member 4 connected to the four sets of rigid accompanying tie rods 3, both of which can be expressed by the formula To calculate, where, E _A is the elastic modulus of the material, A _A is the corresponding cross-sectional area of the rigid tie rod 3 or the replaceable tensile part 4, l _A is the corresponding rigid tie rod 3 or the replaceable tensile part 4 The effective load-carrying length; K _B represents the series rigidity of the tension-pressure sensor 8 and its connection plates such as the upper connecting plate 6 of the test piece, the upper force component 9, and the lower force bar 7, and the bolt connection and tensile force at the connection position of each component are considered. The converted stiffness obtained after the stiffness loss caused by the position of the specimen and the upper connecting plate of the specimen, and the structural glue bonded at the lower connecting plate of the specimen; K _C represents the stiffness of tensile specimen 5, so the entire uniaxial tension Stiffness of stretched rigid companion tension device Its value should be much greater than K _C (K _T ≥ 5K _C ), so that the influence of stiffness degradation in the softening stage of the specimen on the overall stiffness of the system can be ignored. At the same time, attention should also be paid to the ratio of K _B to K _C , K _B to K _C The ratio of should be greater than 5 at least to reduce the impact of the release of this part of the elastic energy on the specimen.

The main steps of installation and implementation of the rigid accompanying tension device of uniaxial stretching of the present invention are as follows:

1) According to the size, stiffness and test strain section of the tensile test piece 5, select a suitable rigid accompanying tie rod 3 and a replaceable tensile member 4, and initially assemble it;

2) Assemble the preliminarily assembled rigid accompanying tie rod member 3 and the replaceable tensile member 4 with the upper rigid plate 10 and the lower rigid plate 1;

3) Fix the tensile test piece 5, the upper connecting plate 6 of the test piece and the lower connecting plate 2 of the test piece together, and then install and fix the lower connecting plate 2 of the test piece on the lower rigid plate 1 through bolts, and at the same time use the bolts to upload the force The component 9 is fixed on the upper rigid plate 10 and connected with the tension pressure sensor 8;

4) Connect the lower dowel 7 with the upper connecting plate 2 of the test piece and the tension pressure sensor 8. During this process, four sets of rigid accompanying tie rods 3 and the replaceable tensile parts 4 connected thereto are simultaneously adjusted to ensure that the upper rigid plate 10 and the lower steel plate 1 have been in a parallel state;

5) Connect the tensile and pressure sensor 8 for data testing, pre-tighten the bolts of each component, first pre-tighten the bolts at the rigid accompanying tie rod 3 and the replaceable tensile component 4 connected to it, and reduce the gap until the pressure appears on the sensor, so as to ensure The tensile test piece is in a state of compression, and then pre-tighten the bolts at the joints of the remaining components to prevent tensile stress;

6) Place the assembled uniaxial tensile rigid accompanying tension device on the testing machine, and the testing machine clamps the upper and lower tensile clamp rods 11 to carry out the tensile test. During the test, note that the tensile force of the testing machine should be less than that of the tensile Yield force of the clamp bar 11 and the yield force of the replaceable tie rod part 4 to protect the test device.

Claims (6)

1. A rigid accompanying pull device for uniaxial stretching, characterized in that it comprises a lower rigid plate, on which a plurality of rigid accompanying pull assemblies are fixedly connected, and an upper rigid plate is fixedly connected above the rigid accompanying pull assembly, and the upper rigid plate and the lower rigid plate are respectively fixed with an upper tension clamp rod and a lower tension clamp rod; it also includes an upper connecting plate of the specimen and a lower connecting plate of the specimen, the lower connecting plate of the specimen is fixed on the lower rigid plate, and the upper connecting plate of the specimen It is fixed on the upper rigid plate in series with the lower transmission dowel, the tension pressure sensor and the upper force component; wherein, each rigid companion tension component includes two rigid companion tension rods fixedly connected to the upper rigid plate and the lower rigid plate respectively and two Replaceable extensions for rigid tie rods. 2. The rigid accompanying pull device of uniaxial stretching according to claim 1, characterized in that, the surface of the rigid accompanying tie rod is threaded, and the upper rigid plate and the lower rigid plate are provided with holes that match the size of the rigid accompanying tie rod. holes, and the rigid tie rod is fixed with the upper rigid plate and the lower rigid plate by pre-tightening bolts. 3. The rigid accompanying tension device for uniaxial tension according to claim 1, characterized in that, the surface of the replaceable tensioning part has threads, and the opening on the rigid accompanying tension rod matches the size of the replaceable tensioning part The screw holes are fixed by pre-tightening bolts. 4. The rigid accompanying pull device of uniaxial stretching according to claim 1, characterized in that, the upper connecting plate of the test piece and the lower connecting plate of the test piece are respectively provided with the upper and lower two ends of the test piece. matching groove. 5. The uniaxially stretched rigid accompanying tension device according to claim 1, characterized in that, the rigidity of the rigid accompanying tension device K _T ≥ 5K _C , wherein, In the formula, K _A1 represents the _total stiffness of multiple rigid companion tension components, K _A2 represents the total stiffness of replaceable tensile parts in multiple rigid companion tension components; Based on the series stiffness of the connecting plate, the upper force component and the lower dowel bar, the converted stiffness is obtained after considering the stiffness loss at the connection position of each component; K _C represents the stiffness of the specimen to be stretched. 6 . The uniaxially stretched rigid accompanying tension device according to claim 5 , wherein the ratio of _KB to K _C is greater than 5. 7 .