Device for testing dynamic III-type fracture property of material

Abstract

The utility model relates to a material dynamic III-type fracture property testing device, and relates to the technical field of material dynamic property testing. Comprising a mounting platform, a baffle plate, a transmission rod, an incident rod, a torsion rod, a clamping-releasing device, a hydraulic loading device and a pressure-torque applying device, the pressure-torque applying device is installed on the baffle and connected with the torsion bar, the torsion bar is connected with the incident bar, the transmission bar abuts against the baffle, a sample is clamped between the transmission bar and the incident bar, the sample is in a thin plate shape, and a prefabricated gap is formed in the sample; the pressure-torque applying device is used for applying axial pressure to the torsion bar and applying torque to the torsion bar; the torsion bar penetrates through the clamping-releasing device, the clamping-releasing device is used for limiting rotation displacement of the torsion bar, and the hydraulic loading device is used for driving the clamping-releasing device to relieve rotation limitation on the torsion bar. According to the utility model, the dynamic loading of the material can be realized, and the material is subjected to III-type fracture damage, so that the dynamic III-type fracture property test of the material is completed.

Description

Technical Field

[0001] The utility model relates to the technical field of material dynamic performance testing, in particular to a material dynamic III type fracture property testing device. Background Art

[0002] The destruction of rock materials is caused by the stress concentration at the internal crack tip, which leads to cracking and expansion to penetration. Therefore, the dynamic fracture behavior of rock materials is very common in various rock engineering and geological activities. According to the mechanical properties of the crack, the fracture can be divided into three types: type I (opening type), type II (sliding type), and type III (tearing type). Type III fracture may occur in the fracture of strike-slip faults during earthquakes and in the crack expansion scenarios of circumferential fracture wells in hydraulic fracturing. Therefore, it is of great significance to the development of rock mechanics and geotechnical engineering construction to accurately determine the dynamic characteristics of type III fracture and understand the failure mechanism of type III fracture of rock materials under high loading rates.

[0003] Among the three types of fractures, the crack tip of type I fracture expands in a direction perpendicular to the tensile stress because the tensile stress exceeds the material limit. It is widely studied because it is the most common and the most dangerous to the structure; type II cracks often appear mixed with type I cracks, and its characteristic is that the force direction is parallel to the crack surface and the crack extension direction. Previous studies have studied the dynamic type II fracture properties of rock materials, and there are standard methods to test this property of rock materials. In contrast, the basic characteristics of type III fracture are: the crack tip starts to crack due to reaching the shear limit, the crack surface is parallel to the shear stress direction, and the crack extension direction is perpendicular to the shear stress direction. Therefore, in order to accurately test the type III fracture properties of the material, it is necessary to ensure that the shear stress at the crack tip reaches the material limit first. For rock materials, their tensile strength is generally weaker than the shear strength, so testing the type III fracture behavior of the material under pure shear stress can better guarantee the accuracy of the results. In addition, the consideration of rate effect is another important factor that fits engineering construction scenes such as blasting and transient slip conditions such as earthquakes. The application of Hopkinson torsion bar related technologies can better meet the stress conditions and loading conditions of the dynamic type III fracture properties of the above-mentioned test materials, so there is an urgent need to complete the relevant testing equipment and methods. Utility Model Content

[0004] The purpose of the utility model is to provide a material dynamic type III fracture property testing device to address the gaps in existing test equipment, which can realize dynamic loading of materials and cause type III fracture damage to materials, thereby completing the dynamic type III fracture property testing of materials.

[0005] To achieve the above-mentioned purpose, the utility model provides a material dynamic type III fracture property testing device, comprising: a mounting platform, a baffle, a transmission rod, an incident rod, a torsion bar, a clamping-releasing device, a hydraulic loading device and a pressure-torque applying device; the baffle, the clamping-releasing device, the hydraulic loading device and the pressure-torque applying device are all mounted on the mounting platform; the pressure-torque applying device is fixedly mounted on the baffle, the output end of the pressure-torque applying device is connected to one end of the torsion bar, the other end of the torsion bar is connected to the incident rod, one end of the transmission rod abuts against the baffle, and a sample is clamped between the other end and the incident rod, the sample is in the shape of a thin plate, and a prefabricated gap is provided on the sample; the pressure-torque applying device is used to apply axial pressure and torque to the torsion bar; the torsion bar passes through the clamping-releasing device, the clamping-releasing device is used to limit the rotational displacement of the torsion bar, and the hydraulic loading device is used to drive the clamping-releasing device to release the rotation restriction on the torsion bar.

[0006] Furthermore, the slit of the sample is in the form of a surface groove or a center through slit; the ratio between the length L and the width W of the sample is k, that is, k=L / W, wherein 1≤k≤2, the width W of the sample is less than the diameter D of the incident rod; the thickness of the sample is T, T≤10mm; the diagonal length of the side of the sample is less than or equal to the diameter D of the incident rod and the transmission rod, that is,

[0007] Furthermore, for specimens with surface grooves, the grooves extend vertically from the center of the specimen surface to the edges of both sides of the thin plate, the groove width d≤1mm, and the single-side groove depth p≤0.3T; for specimens with center-through slits, the slits penetrate the thickness direction of the thin plate and extend from the center of the specimen surface perpendicular to the edge, the slit length s≥3T, and the slit width d≤1mm.

[0008] Furthermore, the clamping-releasing device includes a first clamp body, a second clamp body, a first guide shaft, a second guide shaft and a fastener, the first guide shaft and the second guide shaft are symmetrically installed on the mounting platform along the axial direction of the torsion bar, and the first guide shaft passes through the first clamp body and is connected to the first clamp body bearing, the second guide shaft passes through the second clamp body and is connected to the second clamp body bearing; the first clamp body and the second clamp body are respectively provided with semicircular depressions in the inner centers, and protrusions are provided inside the semicircular depressions, and the protrusions match the grooves provided on the surface of the torsion bar; the first clamp body and the second clamp body are connected above by a fastener, and the fastener is fastened to the upper surfaces of the first clamp body and the second clamp body by bolts, and a slot is provided in the center of the fastener, which is a weak band of the fastener.

[0009] Furthermore, it also includes a tension rod, and both ends of the tension rod are respectively connected to baffles installed at both ends of the installation platform.

[0010] Furthermore, it also includes a first connecting sleeve, and the torsion bar is connected to the incident rod through the first connecting sleeve.

[0011] Furthermore, it also includes a second connecting sleeve, and the torsion bar is connected to the output end of the pressure-torque applying device through the second connecting sleeve.

[0012] Furthermore, it also includes a limiting plate, which is installed on the baffle, and one end of the transmission rod abuts against the limiting plate.

[0013] Furthermore, it also includes a bracket, a plurality of brackets are installed on the mounting platform, and the transmission rod, the incident rod and the torsion rod are all rotatably connected to the bracket.

[0014] Furthermore, the hydraulic loading device is divided into a first hydraulic loading device and a second hydraulic loading device; the first hydraulic loading device is located on one side of the first caliper body and is used to drive the first caliper body; the second hydraulic loading device is located on one side of the second caliper body and is used to drive the second caliper body.

[0015] The beneficial effects of the utility model are:

[0016] The utility model can realize dynamic loading of materials and cause type III fracture failure of materials by optimizing the design of rods and specimen configurations. Based on the stress wave information obtained from the Hopkinson torsion bar, type III fracture properties of materials such as fracture toughness can be calculated, thereby completing the dynamic type III fracture property test of materials, providing important support for evaluating the mechanical properties of materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a top view of the utility model;

[0018] Figure 2 It is the front view of the utility model;

[0019] Figure 3 This is a schematic diagram of the structure of the clamp-release device of the utility model;

[0020] Figure 4 This is a schematic diagram of the structure of an incident rod and a transmission rod clamping a sample according to the utility model;

[0021] Figure 5 This is another schematic diagram of the structure of the incident rod and the transmission rod clamping the sample of the utility model;

[0022] Figure 6 It is a structural schematic diagram of a sample of the utility model;

[0023] Figure 7 for Figure 6 A front view of

[0024] Figure 8 for Figure 6 A top view of

[0025] Fig. 9 for Figure 6 Side view of

[0026] Fig.10 It is a structural schematic diagram of another sample of the utility model;

[0027] Fig.11 for Fig.10 A front view of

[0028] Fig.12 for Fig.10 A top view of

[0029] Fig.13 for Fig.10 Side view of

[0030] Fig.14 This is a schematic diagram of the structure of another sample of the utility model;

[0031] Fig.15 for Fig.14 A front view of

[0032] Fig.16 for Fig.14 A top view of

[0033] Fig.17 for Fig.14 Side view of.

[0034] Among them, in the figure:

[0035] 1-mounting platform, 2-baffle, 3-pull rod, 4-bracket, 5-sample, 6-first connecting sleeve, 7-first hydraulic loading device, 8-torsion bar, 9-pressure-torque applying device, 10-second connecting sleeve, 11-clamping-releasing device, 12-second hydraulic loading device, 13-incident rod, 14-transmission rod, 15-limiting plate, 111-bolt, 112-fastener, 113-first clamp body, 114-second clamp body, 115-first guide shaft, 116-second guide shaft. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the utility model are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of them. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0037] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0038] In the present application, the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation.

[0039] In addition, some of the above terms may be used to express other meanings in addition to indicating orientation or positional relationship. For example, the term "on" may also be used to express a certain dependency or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to specific circumstances.

[0040] In addition, the terms "installed", "set", "provided with", "connected", "connected", and "socketed" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection, or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, elements, or components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0041] like Figure 1-5As shown, the utility model provides a material dynamic type III fracture property testing device, comprising: a mounting platform 1, a baffle 2, a transmission rod 14, an incident rod 13, a torsion bar 8, a clamping-releasing device 11, a hydraulic loading device and a pressure-torque applying device 9; the baffle 2, the clamping-releasing device 11, the hydraulic loading device and the pressure-torque applying device 9 are all mounted on the mounting platform 1; the pressure-torque applying device 9 is fixedly mounted on the baffle 2, the output end of the pressure-torque applying device 9 is connected to one end of the torsion bar 8, and the torsion bar 8 The other end is connected to the incident rod 13, one end of the transmission rod 14 abuts against the baffle 2, and a sample 5 is clamped between the other end and the incident rod 13. The sample 5 is in the shape of a thin plate and is provided with a prefabricated gap. The pressure-torque applying device 9 is used to apply axial pressure to the torsion bar 8 and torque to the torsion bar 8. The torsion bar 8 passes through the clamping-releasing device 11, and the clamping-releasing device 11 is used to limit the rotational displacement of the torsion bar 8. The hydraulic loading device is used to drive the clamping-releasing device 11 to apply and release the rotation restriction on the torsion bar 8. The mounting platform 1 is flat and placed on a horizontal plane. It is provided with threaded holes to facilitate the installation of the bracket 4. The baffle 2 is welded to the mounting platform 1 and is perpendicular to the mounting platform 1. The axial pressure-torque loading device can take the form of hydraulic or electromagnetic loading.

[0042] The utility model can realize dynamic loading of materials and cause type III fracture failure of materials by optimizing the design of the rod configuration. Based on the stress wave information obtained by the Hopkinson torsion bar 8, the type III fracture properties of the material such as the fracture toughness of the material can be calculated, thereby completing the dynamic type III fracture property test of the material, providing important support for evaluating the mechanical properties of the material.

[0043] The clamp-release device 11 comprises a first clamp body 113, a second clamp body 114, a first guide shaft 115, a second guide shaft 116 and a fastener 112. The first guide shaft 115 and the second guide shaft 116 are symmetrically mounted on the mounting platform 1 along the axial direction of the torsion bar 8, and the first guide shaft 115 passes through the first clamp body 113 and is connected to the first clamp body 113 by a bearing, and the second guide shaft 116 passes through the second clamp body 114 and is connected to the second clamp body 114 by a bearing; the first The inner centers of the caliper body 113 and the second caliper body 114 are respectively provided with semicircular depressions, and there are protrusions inside the semicircular depressions, and the protrusions match the grooves provided on the surface of the torsion bar 8, so as to facilitate the coupling of the torsion bar 8 with the clamp-release device 11; the first caliper body 113 and the second caliper body 114 are connected above by a fastener 112, and the fastener 112 is fastened to the upper surfaces of the first caliper body 113 and the second caliper body 114 by bolts 111, and a slot is provided in the center of the fastener 112, which is a weak zone of the fastener 112. The clamp-release device 11 is symmetrically arranged along the torsion bar 8, and an annular protrusion is provided in the center thereof, which can bite with the torsion bar 8 under pressure to limit the rotation of the torsion bar 8, and the fastener 112 is anchored above, and the fastener 112 breaks under the loading pressure of the hydraulic loading device, and the torque in the torsion bar 8 is released. The clamp-release device 11 can move along the axial direction of the torsion bar 8, and is used to limit the rotational displacement of different length parts of the torsion bar 8. The surface of the torsion bar 8 is provided with a groove extending in the axial direction, and the rotation is restricted by passing through the clamp-release device 11, so that the torque is stored in the part between the fixed position of the clamp-release device 11 and the axial pressure-torque applying device within the axial range of the torsion bar 8, and the torque is released when the clamp-release device 11 is released. The fastener 112 is in the shape of a flat plate, and a slot is provided at the center along the Y direction, and the slot extends to the edge in the X direction. In order to ensure the storage and sudden release of the torque of the torsion bar 8, the clamp-release device 11 can also adopt other forms.

[0044] The first hydraulic loading device 7 and the second hydraulic loading device 12 are symmetrically distributed along the axis of the rod and fixed on the mounting platform 1, and the movement direction of the pistons is parallel to the axis. The first hydraulic loading device 7 and the second hydraulic loading device 12 apply pressure to the first caliper body 113 and the second caliper body 114, and cooperate with the fastener 112 to limit the torsion displacement of the torsion bar 8. When the axial pressure and torque are applied to the preset value, the pressure of the first hydraulic loading device 7 and the second hydraulic loading device 12 on the first caliper body 113 and the second caliper body 114 is increased, and the center of the fastener 112 has a large tensile stress due to the slot hole. When the tensile limit of the fastener 112 is exceeded, it breaks, and the torque stored in the torsion bar 8 is released.

[0045] In the utility model, the sample can be made of brittle materials such as rock, concrete, ceramic or graphite. Sample 5 adopts a special configuration. Sample 5 is a thin plate structure with a prefabricated gap at the center of the thin plate. The prefabricated gap can be in various forms. The ratio between the length of sample 5 and the radius of sample 5 is k, k = L / W, where 1≤k≤2, L is the length of sample 5, W is the width of sample 5, and the width of sample 5 is less than the diameter D of the incident rod 13; the thickness of sample 5 is T, T≤10mm. At the same time, the diagonal length of the side of sample 5 is less than or equal to the diameter D of the incident rod 13 and the transmission rod 14, that is,

[0046] Among them, in order to ensure that the Type III fracture failure occurs in Sample 5, the prefabricated gaps have the following two forms:

[0047] First, cut grooves symmetrically on both sides of the thin plate (surfaces with normal lines parallel to the Y axis) (such as Figure 6 , Figure 7 , Figure 8 and Fig. 9 As shown in the figure, the gap is perpendicular to the thickness direction and extends to the side edge of the thin plate sample 5. The groove is located in the center of the sample 5, perpendicular to the length direction, and symmetrically distributed along the central axis of the sample 5. The groove width d≤1mm. In order to ensure the processing accuracy, reduce the processing difficulty, and prevent the sample 5 from being damaged under too small a load and causing inaccurate data, the single-side groove depth p≤0.3T. The cross-sectional shape of the groove of this form of sample 5 can be a variety of shapes symmetrical along the central axis of the sample 5, including rectangular or V-shaped (such as Fig.10 , Fig.11 , Fig.12 and Fig.13 As shown), that is, the gap width decreases linearly from the surface of sample 5 (the surface whose normal direction is parallel to the y-axis) to the inside of sample 5, and the minimum gap width d≤1mm.

[0048] Second, a slit is made through the center of the thin plate surface (the surface whose normal direction is parallel to the Y axis) (e.g. Fig.14 , Fig.15 , Fig.16 and Fig.17 As shown), the slits are symmetrically distributed along the axis of the sample 5, the slits run through the thickness direction of the sample 5 and extend along the z-axis direction, the slit width d≤1mm, and the slit length s≥3T.

[0049] When the sample 5 is grooved symmetrically on both sides or slitted through the center, the groove or slit is located at the center of the sample 5, perpendicular to the length direction (X direction), and symmetrically distributed along the central axis of the sample 5. The sample 5 is clamped between the incident rod 13 and the transmission rod 14. There are many ways to clamp and fix the sample 5. Figure 4As shown, in order to facilitate the installation of the sample 5, the incident rod 13 and the transmission rod 14 are grooved at the ends, and the sample 5 is clamped therein. In order to ensure the stability of the sample 5 and the occurrence of type III fracture failure of the sample 5, the groove width is required to be the same as the thickness T of the sample 5, the incident rod 13 and the transmission rod 14 have the same groove depth M, and to ensure that the preset gap of the sample 5 is not covered by the incident rod 13 or the transmission rod 14, then the groove depth M is less than (Ld) / 2. Figure 5 As shown, the sample 5 can be pasted on the ends of the incident rod 13 and the transmission rod 14. When pasting, ensure that the length direction of the sample 5 is parallel to the axis of the rod, and the pasting position of the sample 5 is symmetrical about the axis of the incident rod 13 to ensure firm pasting.

[0050] The utility model further comprises a tension rod 3, the two ends of which are respectively connected to the baffles 2 mounted at the two ends of the mounting platform. The tension rod 3 passes through the hole of the baffle 2 and is fixed with a fastening bolt, and is used to provide a reaction force when an axial pressure is applied to the rod system composed of the incident rod 13, the transmission rod 14 and the torsion rod 8, and prevent the baffle 2 from tipping over.

[0051] The utility model further comprises a first connecting sleeve 6, through which the torsion bar 8 is connected to the incident rod 13. The utility model further comprises a second connecting sleeve 10, through which the torsion bar 8 is connected to the output end of the pressure-torque applying device 9.

[0052] The utility model further comprises a limiting plate 15 , which is mounted on the baffle 2 , one end of the transmission rod 14 abuts against the limiting plate 15 , and the surface of the limiting plate 15 is smooth and flat.

[0053] The utility model also includes a bracket 4, and a plurality of brackets 4 are installed on the mounting platform, and the transmission rod 14, the incident rod 13 and the torsion bar 8 are all rotatably connected to the bracket 4. Among them, the bracket 4 provides a Z-direction support force perpendicular to the mounting platform 1 for the incident rod 13 and the transmission rod 14. The incident rod 13 can move in a single direction relative to the mounting platform; the transmission rod 14 has the same material and diameter as the incident rod 13 and is coaxially arranged. When the dynamic III-type fracture property test is performed on the sample 5, the sample 5 is clamped between the incident rod 13 and the transmission rod 14, and the crack of the sample 5 is symmetrical about the axis of the incident rod 13 and the transmission rod 14. The torsion bar 8 is coaxially arranged with the incident rod 13 and the transmission rod 14, one side of which is connected to the incident rod 13, and the other side is connected to the axial pressure-torque loading device, and is passed through the clamping-releasing device 11, and a groove is provided on its surface to facilitate being limited by the clamping-releasing device 11.

[0054] The hydraulic loading device is divided into a first hydraulic loading device 7 and a second hydraulic loading device 12 ; the first hydraulic loading device 7 is located at one side of the first caliper body 113 and is used to drive the first caliper body 113 ; the second hydraulic loading device 12 is located at one side of the second caliper body 114 and is used to drive the second caliper body 114 .

[0055] like Figure 1 and Figure 2 As shown, before the test starts, the sample 5 is clamped between the incident rod 13 and the transmission rod 14, the clamp-release device 11 moves to the set position along the X direction, the first hydraulic loading device 7 and the second hydraulic loading device 12 provide pressure, and cooperate with the clamp-release device 11 to limit the rotational displacement of the torsion bar 8, the axial pressure-torque loading device 9 applies axial pressure to the rod system composed of the torsion bar 8, the incident rod 13, and the transmission rod 14, and applies torque to the clamping section of the torsion bar 8 (from the clamp-release device 11 point to the connecting end of the axial pressure-torque applying device), and when the axial pressure and torque are loaded to the set value, the first hydraulic loading device 7 and the second hydraulic loading device 12 apply pressure, the clamp-release device 11 releases the rotational displacement restriction on the torsion bar 8, and the torque stored in the clamping section of the torsion bar 8 is released, and the torsion wave propagates in the direction of the incident rod-sample-transmission rod, and the test is loaded and destroyed.

[0056] The utility model can realize dynamic loading of materials and make materials undergo type III (tearing type) fracture damage by optimizing the rod configuration and the shape of the sample. The fracture toughness of the material can be calculated based on the stress wave information obtained by the Hopkinson torsion bar. Combined with non-contact measurement techniques such as high-speed photography and digital image correlation (DIC), the whole process of dynamic type III fracture damage of materials can be captured, and the type III fracture properties of materials can be further analyzed.

[0057] The utility model also provides a material dynamic type III fracture property testing method, comprising the following steps:

[0058] 1) Connect the data acquisition system to the incident rod and the transmission rod respectively;

[0059] 2) Place the sample between the incident rod and the transmission rod;

[0060] 3) Fix the clamp-release device to the specified position, install the fasteners and apply pressure to limit the rotation of the torsion bar;

[0061] 4) applying axial pressure to the torsion bar through a pressure-torque applying device, and applying torque to the torsion bar to a set value;

[0062] 5) applying lateral pressure to the first jaw body and the second jaw body to break the fastener so that the torque of the torsion bar is released, and the specimen is subjected to torsional load and breaks;

[0063] 6) Recording data through the data acquisition system and performing computational analysis.

[0064] The utility model uses an optimized configuration of the Hopkinson torsion bar to load a special configuration of the sample, combines the data acquisition system to collect the loading and sample response information, and calculates the material's dynamic type III fracture toughness and other parameters. The method proposed in the utility model provides a pure shear load for the sample based on the Hopkinson torsion bar device, which can ensure the accuracy of the test results; the sample used has a simple structure, is easy to process, and is easy to obtain a high processing accuracy; the method can be combined with non-contact strain measurement and other technical means to further test the material's dynamic type III fracture characteristics.

[0065] Example 1

[0066] Test of dynamic mode III fracture toughness of materials:

[0067] This embodiment involves using the above method to test the dynamic mode III fracture toughness of the material. The test method involves using existing instruments and equipment. The main operating steps are as follows:

[0068] 1) Connect the data acquisition system to the incident rod 13 and the transmission rod 14 respectively;

[0069] 2) sandwiching the thin plate sample 5 between the incident rod 13 and the transmission rod 14;

[0070] 3) Fixing the clamp-release device 11 to a specified position, installing the fastener 111 and applying pressure to limit the rotation of the torsion bar 8;

[0071] 4) applying axial pressure to the torsion rod 8-incident rod 13-sample 5-transmission rod 14 through the torque loading device 10, and applying torque to the torsion rod 8 to a set value;

[0072] 5) applying lateral pressure to the first pliers 113 and the second pliers 114 to break the fastener 112 so that the torque of the torsion bar is released, and the specimen is fractured under the torsional load;

[0073] 6) Recording data through the data acquisition system and performing computational analysis.

[0074] Specifically, in step 1), the data acquisition system may include strain gauges, a Wheatstone bridge box, a strain amplifier, an oscilloscope, and a computer, wherein two groups of strain gauges are attached to the surface of the incident rod 13 and the transmission rod 14 at an angle of 45° to the x-direction, for collecting stress wave information in the rod, wherein each group of strain gauges has two, which are attached to the same axial position and different circumferential positions of the incident rod 13 or the transmission rod 14. The strain gauge is connected to the Wheatstone bridge box to convert the stress wave signal into an electrical signal, which is then connected to the strain amplifier and finally connected to the oscilloscope, which records the electrical signal during dynamic loading, and finally uses a computer to process the data.

[0075] Specifically, the sample clamping method in step 2) can be the above two methods. One method is to open grooves at the ends of the incident rod 13 and the transmission rod 14 to clamp the thin plate sample; the other method is to use glue to stick the sample between the incident rod 13 and the transmission rod 14, ensuring that the sticking position is symmetrical about the axial direction of the incident rod 13 and the transmission rod 14, and the sticking is firm.

[0076] Specifically, in step 3), the clamping-releasing device 11 is moved to a set position to obtain an incident wave of a specific width, the torsion bar 8 is rotated so that the groove on the torsion bar 8 matches the protrusion of the clamp body in the clamping-releasing device 11, and the fastener 111 is installed on the two clamp bodies. The first hydraulic loading device 7 and the second hydraulic loading device 12 are used to apply opposite pressure to the two clamp bodies to limit the rotation of the torsion bar 8.

[0077] Specifically, in step 4), an axial pressure-torque loading device is used to apply axial pressure and torque. During the application process, the pressure of the hydraulic loading device can be increased in a timely manner to prevent the torsion bar from rotating while ensuring that the fastener does not break.

[0078] Specifically, the collected stress wave data in step 6) can reflect the mechanical response of the sample during the load-bearing failure process, and parameters such as the dynamic mode III fracture toughness of the material can be calculated according to relevant formulas.

[0079] Example 2

[0080] Calculation of material dynamic type III fracture energy:

[0081] This embodiment can be based on the embodiment 1, combined with the non-contact strain measurement method, measure the displacement field and strain field of the sample surface during the destruction process, calculate the kinetic energy of the sample at the moment of rupture, and further obtain the dynamic type III fracture energy of the sample. The specific operation steps are as follows:

[0082] 1) Connect the data acquisition system to the incident rod 13 and the transmission rod 14 respectively;

[0083] 2) Testing the quality of the thin plate sample 5 and treating the surface of the sample;

[0084] 3) The sample 5 is clamped between the incident rod 13 and the transmission rod 14, and the position of the shooting camera is fixed;

[0085] 4) Fixing the clamp-release device 11 to a specified position, installing the fastener 111 and applying pressure to limit the rotation of the torsion bar 8;

[0086] 5) applying axial pressure to the torsion rod 8-incident rod 13-sample 5-transmission rod 14 through the axial pressure-torque loading device 10, and applying torque to the torsion rod 8 to a set value;

[0087] 6) applying lateral pressure to the first pliers 113 and the second pliers 114 to break the fastener 112 so that the torque of the torsion bar is released, and the specimen is fractured under the torsional load;

[0088] 7) Recording data through the data acquisition system and performing computational analysis.

[0089] Specifically, in step 2), the mass of the sample is weighed to facilitate the subsequent calculation of the kinetic energy of the sample when it breaks; the surface of the sample is treated, including polishing, pasting or drawing speckles on the sample, to facilitate the subsequent capture of the surface movement of the sample;

[0090] Specifically, in step 3), the camera shooting direction is set to be perpendicular to the axial direction of the incident rod 13, and the camera trigger mode, time and other parameters are set to facilitate capturing the sample rupture process;

[0091] Specifically, in step 7), the photographs of the sample rupture process recorded by the camera can be used in combination with technical means such as digital image correlation (DIC) to analyze and calculate the sample crack initiation moment, rupture time, sample speed at rupture, and strain field on the sample surface. The sample kinetic energy can be calculated based on the sample mass, and the energy required for dynamic type III fracture of the sample can be calculated in combination with the stress wave signal collected by the strain gauge.

[0092] The above description is only a preferred embodiment of the present invention and does not limit the technical scope of the present invention. Therefore, any minor modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A material dynamic type III fracture property testing device, characterized in that: include: mounting platforms, baffles, transmission rods, incident rods, torsion bars, clamping-releasing devices, hydraulic loading devices, and pressure-torque applying devices; The baffle, clamping-releasing device, hydraulic loading device and pressure-torque applying device are all installed on the mounting platform; the pressure-torque applying device is fixedly installed on the baffle, the output end of the pressure-torque applying device is connected to one end of the torsion bar, the other end of the torsion bar is connected to the incident rod, one end of the transmission rod abuts against the baffle, and a sample is clamped between the other end and the incident rod, the sample is in the shape of a thin plate, and a prefabricated gap is provided on the sample; the pressure-torque applying device is used to apply axial pressure and torque to the torsion bar; the torsion bar passes through the clamping-releasing device, the clamping-releasing device is used to limit the rotational displacement of the torsion bar, and the hydraulic loading device is used to drive the clamping-releasing device to release the rotation restriction on the torsion bar.

2. A material dynamic type III fracture property testing device as claimed in claim 1, characterized in that: The slit form of the sample is a surface groove or a center through slit; the ratio between the length L and the width W of the sample is k, that is, k = L / W, where 1≤k≤2, the sample width W is less than the incident rod diameter D; the sample thickness is T, T≤10mm; the diagonal length of the side of the sample is less than or equal to the incident rod and the transmission rod diameter D, that is 3. A material dynamic type III fracture property testing device as claimed in claim 2, characterized in that: For the specimen with surface grooves, the grooves extend vertically from the center of the specimen surface to the edges on both sides of the thin plate, the groove width d≤1mm, and the single-side groove depth p≤0.3T. For the specimen with center-through slits, the slits penetrate the thickness direction of the thin plate and extend from the center of the specimen surface perpendicular to the edge. The slit length s≥3T and the slit width d≤1mm.

4. A material dynamic type III fracture property testing device as claimed in claim 3, characterized in that: The clamping-releasing device includes a first clamp body, a second clamp body, a first guide shaft, a second guide shaft and a fastener. The first guide shaft and the second guide shaft are symmetrically installed on the mounting platform along the axial direction of the torsion bar, and the first guide shaft passes through the first clamp body and is connected to the first clamp body bearing, and the second guide shaft passes through the second clamp body and is connected to the second clamp body bearing; the first clamp body and the second clamp body are respectively provided with semicircular depressions in the inner centers, and protrusions are provided inside the semicircular depressions, and the protrusions match the grooves provided on the surface of the torsion bar; the first clamp body and the second clamp body are connected above by a fastener, and the fastener is fastened to the upper surfaces of the first clamp body and the second clamp body by bolts, and a slot is provided in the center of the fastener, which is a weak zone of the fastener.

5. A material dynamic type III fracture property testing device as claimed in claim 3, characterized in that: It also includes a tension rod, and both ends of the tension rod are respectively connected to baffles installed at both ends of the installation platform.

6. A material dynamic type III fracture property testing device as claimed in claim 3, characterized in that: It also includes a first connecting sleeve, and the torsion bar is connected to the incident rod through the first connecting sleeve.

7. A material dynamic type III fracture property testing device as claimed in claim 3 or 6, characterized in that: It also includes a second connecting sleeve, through which the torsion bar is connected to the output end of the pressure-torque applying device.

8. A material dynamic type III fracture property testing device as claimed in claim 3, characterized in that: It also includes a limiting plate, which is mounted on the baffle plate, and one end of the transmission rod abuts against the limiting plate.

9. A material dynamic type III fracture property testing device as claimed in claim 3, characterized in that: It also includes a bracket, a plurality of brackets are installed on the mounting platform, and the transmission rod, the incident rod and the torsion rod are all rotatably connected to the bracket.

10. A material dynamic type III fracture property testing device as claimed in claim 4, characterized in that: The hydraulic loading device is divided into a first hydraulic loading device and a second hydraulic loading device; the first hydraulic loading device is located at one side of the first caliper body and is used to drive the first caliper body; the second hydraulic loading device is located at one side of the second caliper body and is used to drive the second caliper body.

Images