Material III-type fracture toughness testing device based on Hopkinson torsion bar

Abstract

The utility model relates to a material III-type fracture toughness testing device based on a Hopkinson torsion bar, and relates to the technical field of material dynamic performance testing. Comprising a base, a baffle, an emergent rod, an incident rod, a torsion rod, a torsion limiting device, a hydraulic loading device, a torque loading device and an axial pressure loading device, the axial pressure loading device is mounted on the baffle and connected with the torsion bar, the torsion bar is connected with the incident bar, the emergent bar is mounted on the baffle, and a sample is clamped between the emergent bar and the incident bar; the sample is of a cylindrical structure, and a gap vertically extending towards the outer surface is formed in the center in the sample; the torsion bar penetrates through the torsion limiting device to limit rotation displacement of the torsion bar, and the hydraulic loading device drives the torsion limiting device to relieve rotation limitation on the torsion bar; the torque loading device is in transmission connection with the torsion bar and applies torque to the torsion bar. According to the utility model, the Hopkinson torsion bar loading technology is used, so that the sample is in a pure shear stress state and is subjected to III-type fracture damage, and the accurate test of the III-type fracture toughness of the material can be realized.

Description

Technical Field

[0001] The utility model relates to the technical field of material dynamic performance testing, in particular to a material type III fracture toughness testing device based on a Hopkinson torsion bar. Background Art

[0002] The fracture behavior of materials is widely present in various application scenarios and is highly valued: fully understanding the fracture properties of materials has important theoretical significance and engineering value for ensuring the integrity of components and structural stability.

[0003] According to the mechanical properties of cracks, fractures can be divided into three types: type I (opening type), type II (sliding type), and type III (tearing type). At present, the academic community has developed a variety of test methods to study the properties of type I and type II fractures of rock materials. Based on certain loading equipment, such as hydraulic presses, split Hopkinson pressure bars (SHPBs), etc., specially designed specimen configurations, including straight groove semi-circular disc specimens (NSCBs), center herringbone grooved Brazilian disc specimens (CCNBDs), short core compression specimens (SCCs), through shear specimens (PTSs), etc., can be used to load materials such as rocks and concrete and cause them to undergo type I or type II fracture failure, so that the relevant properties of the material can be calculated based on the load information. However, there are currently few test methods for type III fracture. On the one hand, the characteristics of type III fracture require a pure shear stress field to be distributed near the crack of the specimen, which poses a challenge to the loading method; on the other hand, the tensile strength of some materials is weaker than the shear strength, and the tensile limit of the material is reached first, which makes it difficult to ensure the accuracy of the test results. Therefore, there is an urgent need to develop a testing device that meets the loading requirements and fits the rock characteristics. Utility Model Content

[0004] The utility model aims to address the gaps in existing test equipment and provides a material type III fracture toughness testing device based on a Hopkinson torsion bar. The Hopkinson torsion bar loading technology is used to put the sample in a pure shear stress state, thereby realizing the type III fracture toughness test of the sample.

[0005] To achieve the above-mentioned purpose, the utility model provides a material type III fracture toughness testing device based on a Hopkinson torsion bar, comprising: a base, a baffle, an exit rod, an incident rod, a torsion bar, a torque limiting device, a hydraulic loading device, a torque loading device and an axial pressure loading device; the baffle, the torque limiting device, the hydraulic loading device and the torque loading device are all installed on the base, the axial pressure loading device is fixedly installed on the baffle, the output end of the axial pressure loading device abuts against one end of the torsion bar, the other end of the torsion bar is connected to the incident rod, one end of the exit rod abuts against the baffle, and a sample is clamped between the other end and the incident rod; the sample is a cylindrical structure, and a gap extending vertically to the outer surface is provided in the center of the interior; the torsion bar passes through the torque limiting device, the torque limiting device is used to limit the rotational displacement of the torsion bar, and the hydraulic loading device is used to drive the torque limiting device to apply and release the rotation restriction on the torsion bar; the torque loading device is located between the torque limiting device and the axial pressure loading device, and the output end of the torque loading device is transmission-connected with the torsion bar to apply torque to the torsion bar.

[0006] Furthermore, the torque limiting device includes a first caliper body, a second caliper body, a fixed guide shaft and a limit plate, the fixed guide shaft is installed on the base, and the fixed guide shaft passes through the first caliper body and is connected to the first caliper body bearing; the second caliper body is fixed on the base, and the first caliper body and the second caliper body are arranged on both sides of the axis of the torsion bar, and the inner centers of the first caliper body and the second caliper body are respectively provided with semi-depressions, and the semi-depressions have protrusions inside, and the protrusions match the grooves provided on the surface of the torsion bar; the first caliper body and the second caliper body are connected above by a limit plate, and the limit plate is fastened to the upper surfaces of the first caliper body and the second caliper body by fastening bolts, and a slot is provided in the center of the limit plate, which is a weak zone of the limit plate.

[0007] Furthermore, the ratio between the length and diameter of the sample is k, k=L / R, wherein 1≤k≤2, L is the length of the sample, R is the diameter of the sample, and the sample diameter R is smaller than the incident rod diameter D; a gap is prefabricated in the center of the sample, the gap extends vertically to the outer surface of the sample, the gap width is d, d≤1mm, and the gap diameter is s, s≤0.6R.

[0008] Furthermore, the torque loading device includes a hydraulic jacking device, a back plate, a rack and a height limiting plate. The back plate is installed on the base, and a directional slide groove is provided on the side of the back plate close to the torsion bar. The rack is slidably set in the directional slide groove. The hydraulic jacking device is fixed on the back plate, and the output end is connected to the rack. The top of the back plate is connected to the height limiting plate, and the outer surface of the torsion bar is provided with a toothed protrusion that cooperates with the rack.

[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 base.

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

[0011] Furthermore, it also includes a limiting plate, which is installed on the baffle, and one end of the emission rod abuts against the limiting plate.

[0012] Furthermore, it also includes a bracket, a plurality of brackets are installed on the base, and the emission rod, the incident rod and the torsion rod are all rotatably connected to the bracket.

[0013] The beneficial effects of the utility model are:

[0014] The utility model uses the Hopkinson torsion bar loading technology to put the sample in a pure shear stress state, optimizes the sample configuration, and can achieve type III (tearing type) fracture damage of the sample; by collecting stress information on the torsion bar, the material's fracture toughness and other type III fracture properties of the material can be calculated, providing important support for evaluating the mechanical properties of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a top view of the utility model;

[0016] Figure 2 It is the front view of the utility model;

[0017] Figure 3 This is a schematic diagram of the structure of the torque limiting device of the utility model;

[0018] Figure 4 It is a structural schematic diagram of the torque loading device of the utility model;

[0019] Figure 5 This is a schematic diagram of the structure of the incident rod and the exit rod clamping the sample of the utility model;

[0020] Figure 6 It is a schematic diagram of the structure of the sample of the utility model;

[0021] Figure 7 It is a front view of a sample of the utility model.

[0022] Among them, in the figure:

[0023] 1-base, 2-baffle, 3-limiting plate, 4-tension rod, 5-bracket, 6-exit rod, 7-sample, 8-incident rod, 9-sleeve, 10-torsion bar, 11-hydraulic loading device, 12-torque limiting device, 13-torque loading device, 14-axial pressure loading device; 121-fastening bolt, 122-limiting plate, 123-fixed guide shaft, 124-first clamp body, 125-second clamp body, 131-height limiting plate, 132-rack, 133-hydraulic jacking device, 134-back plate. DETAILED DESCRIPTION

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] like Figure 1-7 As shown, the utility model provides a material type III fracture toughness testing device based on the Hopkinson torsion bar, comprising: a base 1, a baffle 2, an exit rod 6, an incident rod 8, a torsion bar 10, a torque limiting device 12, a hydraulic loading device 11, a torque loading device 13 and an axial pressure loading device 14; the baffle 2, the torque limiting device 12, the hydraulic loading device 11 and the torque loading device 13 are all installed on the base 1, the axial pressure loading device 14 is fixedly installed on the baffle 2, the output end of the axial pressure loading device 14 is in contact with one end of the torsion bar 10, and the torsion bar 10 is The other end is connected to the incident rod 8, one end of the emission rod 6 abuts against the baffle 2, and the sample 7 is clamped between the other end and the incident rod 8; the torsion bar 10 passes through the torque limiting device 12, the torque limiting device 12 is used to limit the rotational displacement of the torsion bar 10, and the hydraulic loading device 11 is used to drive the torque limiting device 12 to apply and release the rotation restriction on the torsion bar 10; the torque loading device 13 is located between the torque limiting device 12 and the axial pressure loading device 14, and the output end of the torque loading device 13 is connected to the torsion bar 10 for applying torque to the torsion bar 10. Among them, the emission rod 6 and the incident rod 8 have the same material and diameter and are coaxially arranged. The torsion bar 10 is coaxially arranged with the incident rod 8 and the transmission rod, and its surface is provided with grooves and raised threads, which are convenient for being limited by the torque limiting device 12 and applying torque by the torque loading device 13. The piston of the axial pressure loading device 14 is coaxial with the torsion bar 10 and in vertical contact with the torsion bar 10 so as to apply an axial load to the torsion bar 10 , which may take the form of hydraulic loading or electromagnetic loading.

[0030] The utility model uses a split Hopkinson torsion bar to apply a torsional load to the sample 7, so that the sample 7 is in a pure shear stress state; the sample 7 is a cylindrical structure as a whole, and the ratio between the length and the diameter of the sample 7 is k, k = L / R, wherein 1≤k≤2, L is the length of the sample, R is the diameter of the sample, and the sample diameter R is smaller than the incident rod diameter D; a crack is prefabricated in the center of the sample, that is, it extends vertically from the center of the sample to the outer surface, the gap width is d, d≤1mm, and the gap diameter is s, s≤0.6R to prevent the sample from being damaged under a smaller load, resulting in inaccurate results. The sample can be made of metal or resin and processed by 3D printing or other methods, which is not limited here.

[0031] The torque limiting device 12 includes a first caliper body 124, a first caliper body 125, a fixed guide shaft 123 and a limit plate 122. The fixed guide shaft 123 is installed on the base 1, and the fixed guide shaft 123 passes through the first caliper body 124 and is connected to the first caliper body 124 bearing. The first caliper body 124 can rotate around the fixed guide shaft 123 and move along the X direction; the first caliper body 125 is fixed on the base 1, and the first caliper body 124 and the first caliper body 125 are arranged on both sides of the axis of the torsion bar 10. The inner centers of the first caliper body 124 and the first caliper body 125 are respectively provided with a semi-depression, and the inner centers of the semi-depressions have protrusions, and the protrusions match the grooves provided on the surface of the torsion bar 10; in order to exert the clamping effect on the torsion bar 10, the first caliper body 124 and the first caliper body 125 are connected above by a limit plate 122, and the limit plate 122 is fastened to the upper surfaces of the first caliper body 124 and the first caliper body 125 by fastening bolts 121, and a slot is provided in the center of the limit plate 122, which is a weak zone of the limit plate 122. The hydraulic loading device 11 is fixed on the base 1 and is located on the same side of the first caliper body 124, and its piston moves along the Y direction and can push the first caliper body 124 to rotate around the fixed guide shaft 123. When the axial pressure and torque are applied to the preset value, the pressure of the hydraulic loading device 11 on the first clamp body 124 is increased, and the first clamp body 124 rotates around the fixed guide shaft 123 so that the center of the limit plate 122 is pulled. When the internal stress exceeds the tensile limit, the central slot hole breaks, the rotation restriction of the torsion bar 10 is released, and the torque stored inside is released. In addition, other methods can also be used to limit the torsional displacement of the torsion bar 10. The torque limiting device 12 can move along the axial direction of the torsion bar 10 to limit the rotational displacement of different length parts of the torsion bar 10.

[0032] The torque loading device 13 includes a hydraulic jacking device 133, a back plate 134, a rack 132 and a height limiting plate 131. The back plate 134 is installed on the base 1. A directional slide groove is provided on the side of the back plate 134 close to the torsion bar 10. The rack 132 is slidably arranged in the directional slide groove. The hydraulic jacking device 133 is fixed on the back plate 134, and the output end is connected to the rack 132. The top of the back plate 134 is connected to the height limiting plate 131. The outer surface of the torsion bar 10 is provided with a toothed protrusion that matches the rack 132. Under the thrust of the hydraulic jacking device 133, the rack 132 can move along the Z direction, and at the same time drive the torsion bar 10 to rotate to achieve the purpose of applying torque. At the same time, a height limiting plate 131 is provided above the back plate 134 to limit the movement of the rack 132. In addition, other methods can also be used to apply torque to the torsion bar 10.

[0033] The utility model also includes a tension rod 4, the two ends of which are respectively connected to the baffles 2 installed at the two ends of the base 1 and fixed with bolts, and are used to provide a reaction force when axial pressure is applied to the rod system composed of the exit rod 6, the incident rod 8, and the torsion rod 10, and prevent the baffle 2 from tipping over.

[0034] The utility model further comprises a sleeve 9 , through which the torsion bar 10 is connected to the incident rod 8 .

[0035] The utility model further comprises a limit plate 3, wherein the limit plate 3 is mounted on the baffle 2, one end of the ejection rod 6 abuts against the limit plate 3, and the surface of the limit plate 3 is flat and smooth, and is in vertical contact with one end of the ejection rod 6.

[0036] The utility model further comprises a bracket 5 . A plurality of brackets 5 are mounted on the base 1 . The emission rod 6 , the incident rod 8 and the torsion bar 10 are all rotatably connected to the bracket 5 .

[0037] At the beginning of the test, the sample 7 is coaxially fixed between the incident rod 8 and the exit rod 6, and the torque limiting device 12 is moved to the preset position along the X direction. The hydraulic loading device 11 is used to load the torque limiting device 12 to limit the rotational displacement of the torsion bar 10. The axial pressure loading device 14 and the torque loading device are used to apply axial pressure and torque to the torsion bar 10 to the set values ​​respectively. After the system is stable, the pressure of the hydraulic loading device 11 is increased to cause the torque limiting device 12 to release the restriction on the torsion bar 10, and the torque stored in the torsion bar 10 is released. After the sample 7 is subjected to the torsion load, a type III fracture failure occurs. The clamping method of the sample 7 is as follows: Figure 5 As shown, ensure that the sample 7 is coaxial with the incident rod 8 and the exit rod 6. The sample 7 can be fixed with glue. After pasting, it should be left for a period of time to ensure that the bonding is firm and the glue is dry. The sample 7 can be made by 3D printing technology, and there is no restriction on the material. Among them, X represents the length direction, Y represents the width direction, and Z represents the height direction.

[0038] The utility model uses the Hopkinson torsion bar loading technology to put the sample in a pure shear stress state. By optimizing the sample configuration, the type III (tearing type) fracture damage of the sample can be achieved. By collecting the stress information on the torsion bar, the type III fracture properties of the material such as the fracture toughness of the material can be calculated, providing important support for evaluating the mechanical properties of the material.

[0039] The testing method of the utility model comprises the following steps:

[0040] 1) Connect the data acquisition system to the incident rod and the exit rod respectively;

[0041] 2) The sample is coaxially fixed between the incident rod and the exit rod; wherein the sample adopts a special configuration, the sample is cylindrical as a whole, the ratio between the length and the diameter of the sample is k, k = L / R, wherein 1≤k≤2, L is the length of the sample, R is the diameter of the sample, and the sample diameter R is smaller than the incident rod diameter D; a crack is prefabricated in the center of the sample, that is, the crack extends from the center of the sample to the periphery, the gap width is d, d≤1mm, and the gap diameter is s, s≤0.6R to prevent the sample from being damaged under a smaller load, resulting in inaccurate results.

[0042] 3) Fix the torque limiting device to the specified position, slightly rotate the torsion bar so that it is stuck by the torque limiting device, install the limit plate, increase the pressure of the hydraulic loading device, and limit the rotation of the torsion bar;

[0043] 4) Apply axial pressure to the torsion bar, incident bar, sample, and exit bar through the axial pressure loading device, and apply torque to the torsion bar to a set value through the torque loading device;

[0044] 5) After the pressure torque is stable, the limit plate is pulled off by increasing the pressure of the hydraulic loading device to release the torque of the torsion bar, and the specimen is broken by the torsional load;

[0045] 6) Record data and perform calculation and analysis through the data acquisition system. By setting the torque limit or not, the type III fracture of the sample under dynamic and quasi-static loading conditions can be achieved, and its type III fracture toughness can be calculated based on the stress wave information or loading information in the rod.

[0046] Specifically, in step 1), the data acquisition system may include a strain gauge, a Wheatstone bridge box, a strain amplifier, an oscilloscope and a computer, wherein two sets of strain gauges are pasted on the surface of the incident rod and the exit rod at an angle of 45° to the X direction to collect stress wave information in the rod, the strain gauge is connected to the Wheatstone bridge box, then connected to the strain amplifier, and finally connected to the oscilloscope, the oscilloscope records the electrical signal during dynamic loading, and finally the computer is used to process the data.

[0047] Specifically, in step 3), the torque limiting device is moved to a set position to obtain an incident wave of a specific width, and the pressure of the hydraulic loading device can be increased synchronously during the torque application process to ensure that the torque limiting device limits the torsion displacement of the torsion bar and the limit plate is broken.

[0048] 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.

[0049] The utility model proposes a material type III fracture property testing method based on the Hopkinson torsion bar. By using reasonable loading means and designing optimized sample configuration, a sample with a special configuration is loaded. The loading and sample response information is collected in combination with a data acquisition system, and parameters such as the type III fracture toughness of the material are calculated. The type III fracture of the sample under a pure shear stress state can be realized, providing an effective means for exploring the mechanical properties of the material.

[0050] 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 type III fracture toughness testing device based on a Hopkinson torsion bar, characterized in that: include: Base, baffle, exit rod, entrance rod, torsion bar, torsion limiting device, hydraulic loading device, torque loading device and axial pressure loading device; The baffle, torque limiting device, hydraulic loading device and torque loading device are all installed on the base, the axial pressure loading device is fixedly installed on the baffle, the output end of the axial pressure loading device is abutted against one end of the torsion bar, the other end of the torsion bar is connected to the incident rod, one end of the exit rod is abutted against the baffle, and a sample is clamped between the other end and the incident rod; the sample is a cylindrical structure, and a gap extending vertically to the outer surface is provided in the inner center; the torsion bar passes through the torque limiting device, the torque limiting device is used to limit the rotational displacement of the torsion bar, and the hydraulic loading device is used to drive the torque limiting device to apply and release the rotation restriction on the torsion bar; the torque loading device is located between the torque limiting device and the axial pressure loading device, and the output end of the torque loading device is transmission-connected to the torsion bar for applying torque to the torsion bar.

2. A material type III fracture toughness testing device based on a Hopkinson torsion bar as claimed in claim 1, characterized in that: The ratio between the length and diameter of the sample is k, k=L / R, wherein 1≤k≤2, L is the length of the sample, R is the diameter of the sample, and the sample diameter R is smaller than the incident rod diameter D; a gap is prefabricated in the center of the sample, the gap extends vertically to the outer surface of the sample, the gap width is d, d≤1mm, and the gap diameter is s, s≤0.6R.

3. A material type III fracture toughness testing device based on a Hopkinson torsion bar as claimed in claim 2, characterized in that: The torque limiting device includes a first caliper body, a second caliper body, a fixed guide shaft and a limit plate, the fixed guide shaft is installed on the base, and the fixed guide shaft passes through the first caliper body and is connected to the first caliper body bearing; the second caliper body is fixed to the base, and the first caliper body and the second caliper body are arranged on both sides of the axis of the torsion bar, and the inner centers of the first caliper body and the second caliper body are respectively provided with semi-depressions, and the semi-depressions have protrusions inside, and the protrusions match the grooves arranged on the surface of the torsion bar; the first caliper body and the second caliper body are connected above by a limit plate, and the limit plate is fastened to the upper surfaces of the first caliper body and the second caliper body by fastening bolts, and a slot is provided in the center of the limit plate, which is a weak zone of the limit plate.

4. A material type III fracture toughness testing device based on a Hopkinson torsion bar as claimed in claim 3, characterized in that: The torque loading device includes a hydraulic jacking device, a back plate, a rack and a height limiting plate. The back plate is installed on the base. A directional slide groove is provided on the side of the back plate close to the torsion bar. The rack is slidably arranged in the directional slide groove. The hydraulic jacking device is fixed on the back plate, and the output end is connected to the rack. The top of the back plate is connected to the height limiting plate, and the outer surface of the torsion bar is provided with a toothed protrusion that matches the rack.

5. A material type III fracture toughness testing device based on a Hopkinson torsion bar as claimed in claim 2, characterized in that: It also includes a tension rod, and two ends of the tension rod are respectively connected to baffles installed at two ends of the base.

6. A material type III fracture toughness testing device based on a Hopkinson torsion bar as claimed in claim 2, characterized in that: It also includes a sleeve, through which the torsion bar is connected to the incident rod.

7. A material type III fracture toughness testing device based on a Hopkinson torsion bar as claimed in claim 2, characterized in that: It also includes a limiting plate, which is mounted on the baffle plate, and one end of the ejection rod abuts against the limiting plate.

8. A material type III fracture toughness testing device based on a Hopkinson torsion bar as claimed in claim 2, characterized in that: It also includes a bracket, a plurality of brackets are installed on the base, and the emission rod, the incident rod and the torsion rod are all rotatably connected to the bracket.

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