CN203479586U - Hard compound material pure I type dynamic fracture specimen - Google Patents

Abstract

The utility model discloses a hard compound material pure I type dynamic fracture specimen, the overall shape is of a disc shaped structure, the upper and lower surfaces are parallel to each other, two platforms are symmetrically arranged on the disc circumferential direction, the two platforms are parallel and uniform in size, a through straight flute type crack is arranged along the diameter direction between the two platforms on the disc, the through straight flute type crack is symmetrical in regard to the center position of the disc, and the platforms are vertical to the through straight flute type crack; according to the hard compound material pure I type dynamic fracture specimen, the through straight flute type crack is arranged on a specimen, the through straight flute type crack can be directly guided to expand so as to obtain a pure mode I crack, the parallel loading platforms are arranged on the disc circumferential direction, direct contact with an incident rod and a transmission rod is convenient, the stress wave propagation is convenient, the stress concentration can be effectively reduced, and the test reliability requirements can be achieved by simple clamping without the need of a new processing clamp and a pressing rod.

Description

Pure Mode I Dynamic Fracture Specimens of Hard Composite Materials

technical field

The utility model belongs to the field of dynamic fracture mechanics, in particular to a pure type I dynamic fracture test piece of hard composite material. the

Background technique

Dynamic fracture mechanics is a branch of solid mechanics and has been a research hotspot in the past ten years. Compared with other branches of fracture theory, dynamic fracture mechanics is the most immature branch, and the basic concept was gradually established in the late 1970s. So far, dynamic fracture mechanics is still not a mature discipline. Compared with static fracture mechanics, dynamic fracture mechanics not only has certain difficulties in dealing with mathematical problems, but also the complexity of physics makes experimental research more difficult. In addition, the complexity and limitations of relevant testing techniques for dynamic fracture mechanics research at this stage also restrict the development speed of this discipline. At present, scholars from various countries in the world have widely used the Hopkinson pressure bar device (SHPB) to conduct dynamic fracture experiments on different materials. The basic principle is based on the one-dimensional stress wave, and the strain rate of the material in the range of 101 to 103 is obtained by measuring and converting the signal. This requires the material to meet the stress balance requirements under the action of one-dimensional stress wave during the dynamic loading process, and then fracture instability occurs, instead of simply using the SHPB experimental system to obtain the impact load. In addition, it is difficult to guarantee whether the specimen can meet the pure mode I fracture under impact load. For this reason, relevant scholars at home and abroad have successively proposed short rod type, semicircular type, and disk herringbone type specimens. The structures of these specimens have not been unified and standardized, and there are some differences in the experimental results measured for the same material. The article "Effect of Thermal Treatment on the Dynamic Fracture Toughness of Laurentian Granite" uses semicircular specimens to carry out impact loading in the SHPB system. Although the experimental results meet the I-type fracture surface, the stress concentration caused by linear loading cannot be avoided. Due to the experimental error brought about by this method, there is some controversy: when the loading rate reaches a certain level, the stress concentration caused by linear loading will cause the fracture failure to occur in the loading area before the prefabricated crack. In addition, if a semicircular specimen is used for loading, the incident rod and the transmission rod need to be reprocessed, and the precision is very high, which undoubtedly increases the experimental cost. In the article "Dynamic cracked chevron notched Brazilian disc method for measuring rock fracture parameters", the central prefabricated herringbone cracked disc specimen was used for experimental analysis. This experimental component does not need to rework the incident rod, and can also obtain a good I-type fracture surface. However, the geometrical surface of the herringbone prefabricated groove is relatively complex, and the theoretical analysis is complex and cumbersome, requiring multiple experiments to calibrate the relevant parameters. At the same time, this kind of specimen cannot avoid the adverse effects of stress concentration under high loading rate, and it is also controversial whether the stress wave can fully propagate. These two types of specimens are models widely used by scholars at home and abroad. The purpose is to obtain the type I fracture surface, without considering the influence of the optimization of the structure on the accuracy and authenticity of the experimental results. The research on dynamic fracture should combine the experimental requirements and meet the requirements of one-dimensional stress wave theory. the

Contents of the invention

The purpose of this utility model is to provide a kind of hardness that is beneficial to meet the experimental requirements of one-dimensional stress theory, which is convenient to clamp firmly under the impact loading condition of the Hopkinson experimental system, realizes pure I-type fracture surface, and effectively avoids composite cracks. Pure mode I dynamic fracture specimens of quality composite materials. the

The technical solution to realize the purpose of this utility model is:

A pure I-type dynamic fracture test piece of hard composite material, the overall shape is a disk-shaped structure, the upper and lower surfaces are parallel to each other, and two platforms are symmetrically arranged in the circumferential direction of the disk. The two platforms are parallel and have the same size. A through-straight-groove crack is set in the diameter direction between the platforms, and the through-straight-groove crack is symmetrical to the center of the disk; the platform is perpendicular to the through-straight-groove crack. the

Compared with the prior art, the utility model has significant advantages:

(1) The utility model is equipped with a straight-groove through-type crack on the test piece. Compared with the prior art without cracks, it can directly guide the expansion of the straight-groove through-type crack, thereby obtaining a pure I-type crack and avoiding impact When the loading rate is too high, disorder cracks are generated at the loading end. the

(2) The utility model is equipped with a parallel loading platform in the circumferential direction of the test piece, which can increase the contact surface, facilitate direct contact with the incident rod and the transmission rod, facilitate the propagation of stress waves, and effectively reduce stress concentration; at the same time, it can realize symmetrical clamping , to effectively avoid asymmetric loading caused by arc loading. the

(3) The utility model can strictly meet the size regulations of international material institutions, reduce the difference of experimental results, achieve the purpose of structure optimization and experimental results accuracy and authenticity; simplify the structure of components, thereby avoiding cumbersome and complicated theoretical analysis, directly in the fracture process area Perform analysis; save experimental cost and time, no need for new processing fixtures and pressure rods, and simple clamping can meet the experimental reliability requirements. the

Below in conjunction with accompanying drawing, the utility model is described in further detail. the

Description of drawings

Fig. 1 is the structural representation of the utility model. the

Fig. 2 is a structural top view of the utility model. the

Fig. 3 is a structural sectional view of the utility model. the

Detailed ways

Combined with Figure 1:

The utility model is a pure I-type dynamic fracture test piece of hard composite material. The overall shape is a disc-shaped structure. A through-straight-groove crack is set in the diameter direction between the two platforms on the disc, and the through-straight-groove crack is symmetrical to the center of the disc; the platform is perpendicular to the through-straight-groove crack. the

The thickness of the disc is 0.2-0.3 times the diameter. the

The length of the penetrating straight groove crack is 0.5-0.7 times the diameter of the disc. the

The central angle corresponding to the length of the penetrating straight groove crack is 15°-30°. the

Its structure can achieve structural optimization, save experimental cost and time, and is easy to manufacture and has good implementability. It can be directly tested in the Hopkinson compression bar without adding other fixtures and molds. the

The test piece structure of the utility model is simple to process, and the purpose is to obtain pure I-type fracture cracks, effectively avoid compound cracks, can strictly meet the size regulations of international material institutions, reduce the difference of experimental results, and achieve structural optimization and accurate and true experimental results. purpose; to reduce the stress concentration effect in the loading area caused by impact loading, to avoid cracks first forming and expanding on the loading end surface; to realize the full propagation of one-dimensional stress wave, and to provide certain conditions for achieving stress balance in the experimental process; to simplify the structure of components, so as to avoid Complicated and complicated theoretical analysis can be carried out directly in the fracture process area; the cost and time of the experiment can be saved, no need for new processing fixtures and pressure bars, and the experiment can be carried out directly in the Hopkinson pressure bar with simple clamping, which can meet the reliability requirements of the experiment. the

Example 1:

The utility model is a pure I-type dynamic fracture test piece of hard composite material. The overall shape is a disk-shaped structure, the upper and lower surfaces are parallel to each other, the thickness of the disk is 0.2 times the diameter, and two platforms are symmetrically arranged on the circumference of the disk. , the two platforms are parallel and have the same size, and a through-straight-groove crack is set in the diameter direction between the two platforms on the disc. The length of the through-straight-groove crack is 0.6 times the diameter of the disc. The center of the circle is symmetrical; the platform is perpendicular to the through-straight-groove crack, and the center angle corresponding to the length of the through-straight-groove crack is 15°. the

Example 2:

The utility model is a pure I-type dynamic fracture test piece of hard composite material. The overall shape is a disc-shaped structure, the upper and lower surfaces are parallel to each other, the thickness of the disc is 0.3 times the diameter, and two platforms are symmetrically arranged on the circumference of the disc. , the two platforms are parallel and have the same size. A through-straight-groove crack is set in the diameter direction between the two platforms on the disc. The length of the through-straight-groove crack is 0.7 times the diameter of the disc. The position of the center of the circle is symmetrical; the platform is perpendicular to the through-straight-groove crack, and the center angle corresponding to the length of the through-straight-groove crack is 30°. the

Example 3:

As shown in Figures 1, 2, and 3:

The utility model is a pure I-type dynamic fracture test piece of hard composite material. The overall shape is a disk-shaped structure, the upper and lower surfaces are parallel to each other, the thickness of the disk is 0.25 times the diameter, and two platforms are symmetrically arranged on the circumference of the disk. , the two platforms are parallel and have the same size. A through-straight-groove crack is set in the diameter direction between the two platforms on the disc. The length of the through-straight-groove crack is 0.5 times the diameter of the disc. The center of the circle is symmetrical; the platform is perpendicular to the through-straight-groove crack, and the center angle corresponding to the length of the through-straight-groove crack is 20°. the

Combined with Figure 1, the structural feature is disc-shaped, and the central angle corresponding to the platform is 20°, which can effectively transform the axial impact force into the tensile stress perpendicular to the direction of impact load, so it can directly guide the cracks of the straight groove type penetrating crack. To obtain pure I-type cracks and avoid disordered cracks at the loading end when the impact loading rate is too high. the

In combination with Figure 2, a through-straight crack is prefabricated directly at the center, which can guide pure I-type cracks. the

Combined with Figure 3, the loading end surface is designed as a loading platform, which can increase the contact surface, facilitate direct contact with the incident rod and the transmission rod, facilitate the propagation of stress waves, and effectively reduce stress concentration; at the same time, it can achieve symmetrical clamping and effectively avoid arcs. Asymmetric loading brought about by loading. the

Through this structural design, the experimental requirements can be met, and pure I-type cracks can be obtained under dynamic impact conditions. And it can be used in quasi-static and dynamic tests of metal, rock and soil, glass and hard composite materials. the

Claims (4)

1. the pure I type of a rigid composite material Dynamic Fracture test specimen, it is characterized in that: global shape is disc-shape structure, upper and lower surface is parallel to each other, week at disk is upwards symmetrical arranged two platforms, parallel and the consistent size of two platforms, in diametric(al) on disk between two platforms, arrange and run through straight trough type crackle, run through straight trough type crackle symmetrical about the home position of disk; Platform is with to run through straight trough type crackle vertical.

2. the pure I type of a kind of rigid composite material according to claim 1 Dynamic Fracture test specimen, is characterized in that :-0.3 times of 0.2 times that the thickness of described disk is diameter.

3. the pure I type of a kind of rigid composite material according to claim 1 Dynamic Fracture test specimen, is characterized in that: the described length that runs through straight trough type crackle is disk diameter 0.5 times-0.7 times.

4. the pure I type of a kind of rigid composite material according to claim 1 Dynamic Fracture test specimen, is characterized in that: described to run through the central angle that straight trough type crack length is corresponding be 15 °-30 °.

Images