CN115014976A - Device and method for testing III-type fracture toughness of material - Google Patents
Device and method for testing III-type fracture toughness of material Download PDFInfo
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Abstract
The invention discloses a device and a method for testing III-type fracture toughness of a material, wherein the device is used for testing the III-type fracture toughness of a test piece with a cylindrical structure, and a prefabricated crack extending along the radial direction of the test piece is arranged on the outer wall of the peripheral side of the test piece in a surrounding manner; the device comprises a base, an incident rod, a transmission rod, a shaft pressing device and a torque loading device, wherein the incident rod, the transmission rod, the shaft pressing device and the torque loading device are arranged on the base; the transmission rod and the incident rod are coaxial and are arranged at intervals, and when the III-type fracture toughness test is carried out on a test piece, the test piece is positioned between the incident rod and the transmission rod; the axial compression device comprises a first axial compression device and a second axial compression device, wherein the first axial compression device is abutted with the incident rod, the second axial compression device is abutted with the transmission rod, the first axial compression device is used for applying pressure to the incident rod, and the second axial compression device is used for applying pressure to the transmission rod; the torque loading device is used for applying torque to the incident rod. The device can carry out the III type fracture toughness test under the axle load effect to the rock to realize the III type fracture under the test piece axle load effect, and can make the processing of test piece simple.
Description
Technical Field
The application relates to the field of material mechanics, in particular to a device and a method for testing III-type fracture toughness of a material.
Background
The problem of rock fracture can be involved in civil engineering, mining, oil exploitation, traffic, water conservancy and other projects, for example, in blasting and oil and gas exploitation, the rock breaking efficiency needs to be improved by utilizing the fracture phenomenon of the rock, and in order to guarantee the safety and stability of the engineering structure, the rock fracture needs to be prevented. Therefore, understanding of the failure mechanism of the rock is very important, and the method is helpful for improving the rock breaking speed and safety of the engineering.
The fracture toughness is used as a mechanical parameter for representing the crack propagation resistance of the material, and has important value in engineering application and theoretical research. According to the classical fracture mechanics theory, fractures can be divided into three basic types according to the stress condition of a fracture surface: open (type I), slide (type II) and tear (type III). In the I fracture mode, two crack surfaces are mutually opened; in the II-type fracture mode, two crack surfaces can slide relatively, and the sliding direction is vertical to the direction of the front edge of the crack; in the type III fracture mode, the relative sliding direction of the two fracture surfaces is parallel to the crack front direction, i.e., the shear stress and crack propagation directions are perpendicular.
However, since the rock is a brittle material, the processing of the test piece and the fixture has certain difficulty, and the device is difficult to be directly applied to the rock. So the current devices for simply carrying out fracture toughness test on the rock are fewer. Moreover, a large number of experiments prove that the rock can generate I-type fracture under the I-type loading condition, but under the III-type loading condition, the maximum tensile stress of the crack tip often reaches a critical value before the maximum shear stress, so that tensile fracture deviating from the original crack surface direction is generated, and the real III-type fracture is difficult to obtain. Therefore, there is a need for a device and a method for testing type III fracture toughness of rock accurately.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a device and a method for testing III-type fracture toughness of a material, which can be used for testing the III-type fracture toughness of a rock under the action of axial compression so as to realize III-type fracture of a test piece under the action of axial compression, and can ensure that the test piece is simple and easy to process.
In order to achieve the above object, in a first aspect, the present invention discloses an apparatus for testing type III fracture toughness of a material, the apparatus is configured to perform type III fracture toughness testing on a test piece, the test piece is of a cylindrical structure, a prefabricated crack is circumferentially arranged on an outer wall of a peripheral side of the test piece, and the prefabricated crack extends along an axial direction and a radial direction of the test piece;
the device comprises:
a base;
the incident rod is arranged on the base and can move relative to the base;
the transmission rod and the incidence rod are coaxial and are arranged oppositely at intervals, when the III-type fracture toughness test is carried out on the test piece, the test piece is positioned between the incidence rod and the transmission rod, and the axial direction of the test piece is parallel to the axial direction of the incidence rod and the axial direction of the transmission rod;
the axial compression device comprises a first axial compression device and a second axial compression device which are arranged on the base, the first axial compression device is abutted against one end, far away from the transmission rod, of the incident rod and is rotatably connected with the incident rod, and the first axial compression device is used for applying pressure to the incident rod; the second axial pressing device is abutted against one end, far away from the incident rod, of the transmission rod and is used for applying pressure to the transmission rod;
the torque loading device is arranged on the base and connected with the incident rod and used for applying torque to the incident rod.
In this embodiment, when the type III fracture toughness test is performed on the test piece, the test piece is located between the incident rod and the transmission rod, and the axial direction of the test piece is parallel to the axial direction of the incident rod and the axial direction of the transmission rod, so that the torque applied to the incident rod by the torque loading device can be loaded onto the test piece, so as to realize the type III loading on the test piece, and realize the type III fracture of the test piece, so as to measure the type III fracture toughness of the test piece. The axial compression device comprises a first axial compression device and a second axial compression device which are arranged on the base, the first axial compression device is abutted with one end of the incident rod far away from the transmission rod, the second axial pressing device is used for applying pressure to the incident rod, the second axial pressing device is abutted with one end of the transmission rod far away from the incident rod, is used for applying pressure to the transmission rod, so that both sides of the test piece along the axial direction can be pressed, when the device is used for carrying out III-type fracture toughness test on the test piece, the test piece can be subjected to torque loading under the condition that both sides along the axial direction are subjected to pressure, so that the type III fracture of the test piece is closer to the actual type III fracture, thereby further deeply understanding the deformation and III-type fracture mechanism of the test piece under the action of torque loading, so as to accurately predict the type III fracture phenomenon of the material under the combined action of axial pressure (namely, pressure applied along the axial directions of the incident rod and the transmission rod) and torque.
The device comprises a base, an incident rod, a transmission rod, a shaft pressing device and a torque loading device, and is a Hopkinson torsion bar experimental device. Compared with the existing III-type fracture toughness testing device, the III-type load can be loaded without complex loading, complex loading operation can be avoided, the III-type fracture toughness testing device has the advantages of simple loading mode, easiness in operation and high loading precision, and a reliable testing approach is provided for determining the III-type fracture toughness.
In addition, the test piece is of a cylindrical structure, prefabricated cracks are arranged on the outer wall of the periphery of the test piece in a surrounding mode, and the prefabricated cracks extend along the axial direction and the radial direction of the cylindrical structure. From this, when processing the preparation to the test piece, only need be with the test piece processing for the cylinder structure earlier, then accessible cutting machine rotary cutting on the test piece of cylinder structure, can obtain the annular prefabricated crack that has the predetermined degree of depth promptly, compare in the prefabricated crack of processing several different extending directions of producing on the test piece, the cutting process volume of this test piece is little, the processing degree of difficulty has been reduced, especially to the test piece of materials such as the rock of coarse grain and concrete, can also reduce the test piece damage of adding man-hour, the machining precision is improved. Therefore, the test piece of this embodiment not only preparation mode is simple, the processing degree of difficulty is low, but also can improve the machining precision of test piece.
In a possible implementation manner of the first aspect, a ratio between the length of the specimen and the radius of the specimen is k, where k is L/R, where k is greater than or equal to 2 and less than or equal to 4, L is the length of the specimen, and R is the radius of the specimen.
In a possible implementation manner of the first aspect, the ratio between the depth of the pre-crack and the radius of the test piece is δ, δ being h/R, wherein 0.4 δ 0.6 h the depth of the pre-crack.
In a possible implementation manner of the first aspect, the minimum radius of the test piece is R min ，
Dr is the outer diameter of the incident rod, Dr is more than or equal to 48mm and less than or equal to 52mm, and sigma is max Is the maximum axial pressure value, σ, of the device t Is the compressive strength of the test piece, F s Is the pressure safety factor of the device;
the radius R of the test piece ranges from,
in a possible implementation manner of the first aspect, the width of the pre-crack is not greater than 1 mm.
In a possible implementation manner of the first aspect, the pre-crack is located at an intermediate position of the test piece in the axial direction.
In a possible implementation manner of the first aspect, the device further includes a first clamp and a second clamp which are arranged oppositely, the first clamp is connected to the incident rod, the second clamp is connected to the transmission rod, opposite surfaces of the first clamp and the second clamp are both planes, and when the test piece is subjected to a type III fracture toughness test, the test piece is fixed on the opposite planes of the first clamp and the second clamp.
In a possible implementation manner of the first aspect, the incident rod and the transmission rod are both circular ring-shaped tubular structures;
the first clamp comprises a first mounting piece and a first clamping piece, one end of the first mounting piece is embedded in the incident rod, a first clamping portion is arranged at one end, facing the first mounting piece, of the first clamping piece, and the first clamping piece is detachably connected with the first mounting piece through the first clamping portion;
the second anchor clamps include second installed part and second holder, the one end of second installed part is inlayed and is located in the transmission pole, the second holder orientation one of second installed part is served and is provided with second joint portion, the second holder passes through second joint portion with the connection can be dismantled to the second installed part.
In a second aspect, the present invention also provides a testing method for testing type III fracture toughness of a material, the testing method being applied to the apparatus for testing type III fracture toughness of a material according to the first aspect, the testing method comprising:
connecting a data acquisition system to an incident rod and a transmission rod of the device respectively;
fixing a test piece between the incident rod and the transmission rod;
applying pressure to the incident rod and the transmission rod through an axial compression device of the device to a preset pressure value;
applying torque to the incident rod through a torque loading device of the device until the test piece is broken;
and recording data through the data acquisition system and calculating.
In this embodiment, the test method can be used for loading a test piece by using the device for testing the type III fracture toughness of the material in the first aspect, and the test method is simple in operation process and easy to operate, so that the test method has great advantages in both test equipment and test steps. And the device applied by the testing method is the device for testing the type III fracture toughness of the material in the first aspect, so that the testing method for testing the type III fracture toughness of the material can produce the same or similar beneficial effects as the device in the first aspect.
In a possible implementation manner of the second aspect, the apparatus includes a clamp, the clamp includes a first clamp and a second clamp which are oppositely arranged, the first clamp is fixed on the incident rod, and the second clamp is fixed on the transmission rod;
the fixing the test piece between the incident rod and the transmission rod includes:
and bonding the test piece on the clamp.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a perspective view of an apparatus for type III fracture toughness testing of materials according to an embodiment of the present invention;
FIG. 2 is a schematic structural diagram of an apparatus for type III fracture toughness testing of a material according to an embodiment of the present invention;
FIG. 3 is a schematic structural diagram of an assembled incident rod, transmission rod and test piece according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of a test piece according to an embodiment of the present invention;
FIG. 5 is a right side view of a test piece provided by an embodiment of the present invention;
FIG. 6 is a schematic structural view of the first mounting member being inserted into the shooting rod and the first clamping member not being assembled with the first mounting member according to the embodiment of the present invention;
FIG. 7 is a right side view of a first clamp provided by an embodiment of the present invention;
fig. 8 is a flowchart of a testing method for testing type III fracture toughness of a material according to an embodiment of the present invention.
Description of reference numerals:
1-a base; 2-a first axial compression device; 3-a torque loading device; 4-an incident rod; 5-testing the sample; 51-preparing a crack; 6-a transmission rod; 7-second axial means; 8-a first clamp; 81-a first mount; 811-a first card slot; 812-a first boss; 82-a first clamp; 821-a first clamping part; 9-a second clamp; 100-device.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the present invention, the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "vertical", "horizontal", "lateral", "longitudinal", and the like indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings. These terms are used primarily to better describe the invention and its embodiments and are not intended to limit the indicated devices, elements or components to a particular orientation or to be constructed and operated in a particular orientation.
Moreover, some of the above terms may be used in other meanings besides orientation or positional relationship, for example, the term "upper" may also be used in some cases to indicate a certain attaching or connecting relationship. The specific meanings of these terms in the present invention can be understood by those skilled in the art as appropriate.
Furthermore, the terms "mounted," "disposed," "provided," "connected," and "connected" are to be construed broadly. For example, it may be a fixed connection, a removable connection, or a unitary construction; can be a mechanical connection, or an electrical connection; may be directly connected, or indirectly connected through intervening media, or may be in internal communication between two devices, elements or components. The specific meanings of the above terms in the present invention can be understood by those of ordinary skill in the art according to specific situations.
Furthermore, the terms "first," "second," and the like, are used primarily to distinguish one device, element, or component from another (the specific nature and configuration may be the same or different), and are not used to indicate or imply the relative importance or number of the indicated devices, elements, or components. "plurality" means two or more unless otherwise specified.
The embodiment of the invention provides a device and a method for testing III-type fracture toughness of a material, which can be used for testing the III-type fracture toughness of a rock under the action of axial pressure so as to realize III-type fracture of a test piece under the action of axial pressure, and can enable the processing of the test piece to be simple and easy to realize.
The apparatus and method for testing type III fracture toughness of a material are described in detail below by way of specific examples:
example one
The embodiment of the application provides a device for testing type III fracture toughness of a material, and as shown in fig. 1 to fig. 3, the device 100 is used for testing type III fracture toughness of a test piece 5, the test piece 5 is of a cylindrical structure, a preformed crack 51 is arranged on the peripheral side outer wall of the test piece 5 in a surrounding manner, and the preformed crack 51 extends along the radial direction of the cylindrical structure.
The device 100 comprises a base 1, an incident rod 4, a transmission rod 6, an axial compression device and a torque loading device 3, wherein the incident rod 4 is arranged on the base 1 and can move relative to the base 1; the transmission rod 6 and the incident rod 4 are coaxial and are arranged oppositely at intervals, when the III-type fracture toughness test is carried out on the test piece 5, the test piece 5 is positioned between the incident rod 4 and the transmission rod 6, and the axial direction of the test piece 5 is parallel to the axial directions of the incident rod 4 and the transmission rod 6; the axial compression device comprises a first axial compression device 2 and a second axial compression device 7 which are arranged on the base 1, the first axial compression device 2 is abutted against one end, far away from the transmission rod 6, of the incident rod 4 and is rotatably connected with the incident rod 4, and the first axial compression device 2 is used for applying pressure to the incident rod 4; the second axial pressing device 7 is abutted with one end of the transmission rod 6 far away from the incident rod 4 and is used for applying pressure to the transmission rod 6; the torque loading device 3 is disposed on the base 1 and connected to the incident rod 4, and is configured to apply a torque to the incident rod 4.
In this embodiment, when a type III fracture toughness test is performed on a test piece 5, the test piece 5 is located between the incident rod 4 and the transmission rod 6, and an axial direction of the test piece 5 is parallel to axial directions of the incident rod 4 and the transmission rod 6, so that a torque applied to the incident rod 4 by the torque loading device 3 can be loaded on the test piece 5 to realize type III loading on the test piece 5, and the test piece 5 is subjected to type III fracture to measure the type III fracture toughness of the test piece 5. The axial compression device comprises a first axial compression device 2 and a second axial compression device 7 which are arranged on the base 1, the first axial compression device 2 is abutted with one end of the incident rod 4 far away from the transmission rod 6, for applying pressure to the incident rod 4, the second axial pressing device 7 is abutted with one end of the transmission rod 6 far away from the incident rod 4, for applying pressure to the transmission rod 6, so that both sides of the test piece 5 in the axial direction can be subjected to the pressure, so that when the device 100 is used for testing the III-type fracture toughness of the test piece 5, the test piece 5 can be subjected to torque loading under the condition that both sides along the axial direction are subjected to pressure, the III-type fracture of the test piece 5 is closer to the actual III-type fracture, thereby further deeply understanding the deformation and type III fracture mechanism of the test piece 5 under the action of torque loading, so as to accurately predict the type III fracture phenomenon of the material under the combined action of axial pressure (namely, pressure applied along the axial directions of the incident rod and the transmission rod) and torque.
The device 100 includes a base 1, an incident rod 4, a transmission rod 6, an axial compression device, and a torque loading device 3, and is a hopkinson torsion bar experimental device. Compared with the existing III-type fracture toughness testing device 100, the III-type load can be loaded without complex loading, complex loading operation can be avoided, the III-type fracture toughness testing device has the advantages of simple loading mode, easiness in operation and high loading precision for the III-type fracture toughness testing of the test piece 5, and a reliable testing approach is provided for determining the III-type fracture toughness.
In addition, as shown in fig. 3 to 5, the test piece 5 has a cylindrical structure, and the peripheral outer wall of the test piece 5 is provided with a pre-fabricated crack 51 in a surrounding manner, and the pre-fabricated crack 51 extends in a radial direction of the cylindrical structure. From this, when processing the preparation to test piece 5, only need process test piece 5 earlier for the cylinder structure, then accessible cutting machine rotary cutting on the test piece 5 of cylinder structure, can obtain the annular prefabricated crack 51 that has the predetermined degree of depth promptly, compare in processing on test piece 5 and produce the prefabricated crack 51 of several different extending directions, this test piece 5's cutting process volume is little, the processing degree of difficulty has been reduced, especially to the test piece 5 of materials such as the rock of coarse grain and concrete, test piece 5 damage during processing can also be reduced, the machining precision is improved. Therefore, the test piece 5 described in this embodiment not only has a simple manufacturing method and low processing difficulty, but also can improve the processing precision of the test piece 5.
Foretell base 1 still can be provided with the supporting seat, and the pole 4 and the pole 6 that transmit can set up on base 1 through the supporting seat respectively, wherein seted up the through-hole on the supporting seat, and the pole 4 and the pole 6 that transmit wear to locate in the through-hole of incidence, and the pole 4 and the pole 6 that transmit all can remove for the supporting seat.
The test piece 5 may be a test piece 5 made of a brittle material such as rock, concrete, ceramic, or graphite, but is not limited thereto. And, when the test piece 5 is a rock material, the rock is usually obtained by drilling core at the engineering site, generally, the obtained rock is cylindrical, and then the cylindrical rock is processed into the test piece 5 for testing. And the test piece 5 described in this embodiment is a cylindrical structure for the rock material obtained through the core drilling mode can be obtained through polishing the required test piece 5, thereby the processing of the test piece 5 can be simpler.
In the embodiment, the ratio between the length of the specimen 5 and the radius of the specimen 5 may be k, where k is L/R, where k is greater than or equal to 2 and less than or equal to 4, L is the length of the specimen 5, and R is the radius of the specimen 5. Therefore, the radius of the test piece 5 can be properly selected through the obtained length of the test piece 5, so that the depth of the prefabricated crack 51 can be conveniently determined by the test piece 5 according to the radius of the test piece 5, and the III-type fracture can be more easily obtained when the III-type fracture toughness test is carried out on the test piece 5.
Specifically, when the ratio k between the length of the test piece 5 and the radius of the test piece 5 is smaller than 2, the diameter of the test piece 5 is large, so that the fractured surface can be fractured easily along the prefabricated crack 51, the depth of the prefabricated crack 51 needs to be deep, the prefabricated crack 51 is not favorable for processing, the processing difficulty of the test piece 5 is improved, or the test piece 5 can be fractured only by applying a large torque. When the ratio k between the length of the test piece 5 and the radius of the test piece 5 is greater than 4, the diameter of the test piece 5 is smaller, so that the depth of the prefabricated crack 51 is not easy to process to the preset depth or can be processed to the preset depth, but the test piece 5 can be fractured only by applying smaller torque when the III-type fracture toughness test is performed on the test piece 5, so that larger errors occur in the mechanical properties such as the fracture law and the fracture toughness of the obtained test piece 5, and further intensive research and understanding on the deformation and fracture mechanism of the test piece 5 under the torque loading effect are not facilitated. Therefore, when the ratio between the length of the test piece 5 and the radius of the test piece 5 is greater than or equal to 2 and less than or equal to 4, the processing difficulty of the test piece 5 is not increased, and the test piece 5 can be fractured when a small torque is applied, so that the obtained mechanical properties of the test piece 5, such as the fracture law, the fracture toughness and the like, have large errors. Namely k is more than or equal to 2 and less than or equal to 4, so that the processing difficulty of the test piece 5 can be reduced, and the test precision of the test piece 5 can be improved.
Alternatively, the ratio between the depth of the pre-crack 51 and the radius of the test piece 5 may be δ, δ being h/R, where 0.4 ≦ δ ≦ 0.6, and h being the depth of the pre-crack 51. Therefore, the depth of the pre-crack 51 can be effectively controlled according to the radius of the test piece 5, so that the pre-crack 51 is easy to process, and the test piece 5 can generate type III fracture along the fracture surface of the pre-crack 51 when being applied to a preset torque value.
Specifically, when the ratio between the depth of the prefabricated crack 51 and the radius of the test piece 5 is greater than 0.6, the depth of the prefabricated crack 51 is deep, the processing difficulty of the prefabricated crack 51 is increased, the test piece 5 can be fractured only by applying smaller torque when the III-type fracture toughness test is carried out on the test piece 5, and the obtained mechanical properties of the test piece 5, such as fracture regularity, fracture toughness and the like, have larger errors. When the ratio of the depth of the pre-crack 51 to the radius of the test piece 5 is less than 0.4, the depth of the pre-crack 51 is shallow, so that the test piece 5 can be fractured only by applying a large torque when the type III fracture toughness test is performed on the test piece 5, or the test piece 5 cannot be fractured in a type III manner along the fracture surface of the pre-crack 51 after the device 100 applies the maximum torque to the test piece 5. Therefore, when δ is 0.4 ≦ δ ≦ 0.6, not only the processing difficulty of the pre-crack 51 can be reduced, but also the apparatus 100 can generate type III fracture that fractures along the fracture surface of the pre-crack 51 when the preset torque value is applied to the test piece 5.
The radius of the test piece 5 is not easily larger than the maximum radius value of the incident rod 4 and the transmission rod 6 in the device 100, so that the problem that the test operation on the test piece 5 is inconvenient due to the fact that the test piece 5 is not easily fixed due to the large radius of the test piece 5 is avoided, and the test precision is reduced. Of course, the radius of the test piece 5 is not too small, so that the test piece 5 is not easy to fix due to the small radius of the test piece 5, and the test operation of the test piece 5 is not convenient.
Specifically, the outer diameters of the incident rod 4 and the transmission rod 6 may be set to be the same to facilitate determination of the radius value of the test piece 5, and the incident rod 4 and the transmission rod 6 may be processed conveniently. Then, the minimum radius of the test piece 5 may be R min ，
Dr is more than or equal to 48mm and less than or equal to 52mm, sigma is the outer diameter of the incident rod 4 max Is the maximum axial pressure value, σ, of the device 100 t Uniaxial compressive strength of test piece 5, F s Is the pressure safety factor of the device 100; thus, the radius R of the test piece 5 is in the range,
the maximum axial pressure value of the device 100 is a determined value, the compressive strength of the test piece 5 is related to the material of the test piece 5, and the maximum axial pressure value can be obtained by inquiring the mechanical properties of the material, and the pressure safety coefficient of the device 100 can be obtained by the ratio of the maximum axial pressure value which can be applied by the device 100 to the preset axial pressure value applied by the device 100.
The test piece 5 generates type III fracture along the fracture surface of the prefabricated crack 51, so that the minimum radius of the fracture surface of the test piece 5, namely the minimum radius of the fracture surface of the prefabricated crack 51, can be calculated, and the minimum radius which can be processed by the test piece 5 can be calculated by using the minimum radius, so that the test piece 5 with the proper radius can be conveniently processed to test the type III fracture toughness.
In particular, the outer diameter Dr of the incident rod 4 may take 50mm, the maximum axial pressure σ that the device 100 may apply max 10Mpa, and when the test piece 5 is a rock test piece, the uniaxial compressive strength σ of the test piece 5 t The pressure safety factor of the apparatus 100 may be 1.2 Fs, which is a value that varies according to the type of rock, and in this case, the minimum radius R of the fracture surface of the test piece 5 min As shown in table one.
In addition, the incident rod 4 may be made of a metal material, and the material of the incident rod 4 may be a metal such as stainless steel, carbon steel, or a copper alloy, which is not limited herein. The outer diameter Dr of the incident rod 4 can be within a range of 48mm to 52mm, so that the incident rod 4 can bear larger axial pressure value and torque value, and the type III fracture toughness test of the test piece 5 is guaranteed.
The width b of the prefabricated crack 51 is not more than 1 mm. Therefore, the prefabricated crack 51 is close to the crack of the test piece 5 in the actual engineering environment, the influence of the prefabricated crack 51 on the test piece 5 on the mechanical properties of the test piece 5 such as the fracture rule, the fracture toughness and the like obtained in the fracture toughness test can be reduced, and the test precision of the test piece 5 is improved.
The pre-crack 51 is located at an intermediate position of the test piece 5 in the axial direction. Thus, the portions of the test piece 5 on both sides of the pre-crack 51 that are subjected to the load can be made substantially the same to facilitate loading of the test piece 5.
The above-described prepared crack 51 located at the middle position of the specimen 5 in the axial direction means that the prepared crack 51 is located at a position substantially in the middle of the specimen 5 in the axial direction.
The fixing of the test piece 5 between the incident rod 4 and the transmission rod 6 has various implementation manners, for example, the test piece 5 can be fixed on a fixture, the fixture is fixed between the incident rod 4 and the transmission rod 6, and the test piece 5 can be fixed between the incident rod 4 and the transmission rod 6, and meanwhile, the incident rod 4 and the transmission rod 6 can be prevented from being damaged when the III-type fracture toughness test is performed on the test piece 5; or the test piece 5 is firstly supported between the incident rod 4 and the transmission rod 6, then the first axial pressing device 2 applies pressure to the incident rod 4, and the second axial pressing device 7 applies pressure to the transmission rod 6, and then the support of the test piece 5 is removed, so that the test piece 5 is extruded and fixed between the first clamp 8 and the second clamp 9, and the test piece 5 is not required to be fixed by additionally manufacturing a clamp, so that the cost is saved; of course, the test piece 5 is fixed between the incident rod 4 and the transmission rod 6, and other implementations are possible, and are not limited herein. The following description will be made in detail taking as an example a case where the test piece 5 is fixed between the incident rod 4 and the transmission rod 6 by a jig.
As shown in fig. 3, the apparatus 100 further includes a first clamp 8 and a second clamp 9 disposed opposite to each other, the first clamp 8 is connected to the incident rod 4, the second clamp 9 is connected to the transmission rod 6, and opposite surfaces of the first clamp 8 and the second clamp 9 are both flat surfaces, and when the test piece 5 is subjected to the type III fracture toughness test, the test piece 5 is fixed on the opposite surfaces of the first clamp 8 and the second clamp 9.
Therefore, the test piece 5 is fixed on the plane opposite to the first clamp 8 and the second clamp 9, the test piece 5 is in surface contact with the first clamp 8 and the second clamp 9, the stress of the test piece 5 is uniform, compared with the situation that the pressure head is arranged on the test piece 5, the incident rod 4 and the transmission rod 6 fix the test piece 5 between the incident rod 4 and the transmission rod 6 through the pressure head, the test piece 5 is in surface contact with the clamps and the clamps, the incident rod 4 and the transmission rod 6 are prevented, the test piece 5 is prevented from cracking in advance of the prefabricated crack 51 at the loading position due to point contact loading when being loaded, and test failure due to the fact that the test piece 5 cracks in advance of the prefabricated crack 51 at the loading position is avoided.
Specifically, the test piece 5 is fixed on the plane where the first clamp 8 and the second clamp 9 are opposite to each other in various ways, for example, the test piece 5 may be adhered to the first clamp 8 and the second clamp 9 by glue; or a clamping groove is arranged on the plane opposite to the first clamp 8 and the second clamp 9, and two ends of the test piece 5 can be respectively clamped in the clamping grooves on the first clamp 8 and the second clamp 9; of course, other fixing methods are also possible as long as the test piece 5 can be fixed between the incident rod 4 and the transmission rod 6, and the fixing method is not limited herein.
In some embodiments, as shown in fig. 3 and 6, the incident rod 4 and the transmission rod 6 are both circular ring-shaped tubular structures; first anchor clamps 8 include first installed part 81 and first holder 82, and the one end of first installed part 81 is inlayed and is located the incidence pole 4 in, and first holder 82 is served towards one of first installed part 81 and is provided with first joint portion 821, and first installed part 81 is served towards one of first installed part 82 and has been seted up first draw-in groove 811, and first installed part 81 can be dismantled with first holder 82 in first draw-in groove 811 through first joint portion 821 joint and be connected. In the torque application process, the first clamping piece 82 is clamped in the first clamping groove 811 through the first clamping part 821 and tightly clamped with the first mounting piece 81, and relative torsion cannot occur; the second anchor clamps 9 include second installed part and second holder, and the one end of second installed part is inlayed and is located in transmission pole 6, and one of second holder orientation second installed part is served and is provided with second joint portion, and the second installed part is served towards one of second holder and has been seted up the second draw-in groove, and the second installed part passes through second joint portion joint and can dismantle with the second holder in the second draw-in groove and be connected. During the torque application process, the second clamping piece can be clamped with the second mounting piece and relative torsion cannot occur.
Therefore, the first clamping piece 82 can be detached from the first mounting piece 81 through the detachable connection of the first clamping piece 82, so that the first clamping piece 82 can be cleaned and maintained conveniently. Similarly, can dismantle with the second installed part through the second holder and be connected, can dismantle the second holder to conveniently wash the maintenance to the second holder.
Specifically, the one end of first installed part 81 is set up to be provided with first screw on the outer wall that first installed part 81 is close to incident pole 4 in inlaying and locating incident pole 4, and incident pole 4 is provided with the second screw on the inside wall towards first installed part 81 one end, and first screw and second screw phase-match, so, can make incident pole 4 and first installed part 81 pass through threaded connection to make the installation of incident pole 4 and first installed part 81 firm. Similarly, the second installation part is provided with a third thread on the outer wall close to the transmission rod 6, the transmission rod 6 is provided with a fourth thread on the inner side wall towards one end of the second installation part, and the third thread is matched with the fourth thread, so that the transmission rod 6 is in threaded connection with the second installation part, and the transmission rod 6 and the second installation part are firmly installed.
In addition, the first mounting member 81 is detachably connected to the first clamping member 82 in the first clamping groove 811 through the first clamping portion 821. Specifically, first joint portion 821 can set up to cuboid joint portion, and first draw-in groove 811 can be for the cuboid recess that matches, and cuboid joint portion can inlay and locate in the cuboid recess, and applys the in-process at the moment of torsion, and cuboid joint portion can not twist reverse for the cuboid recess takes place to make first holder 82 and first installed part 81 can the chucking be connected, and can not take place to twist reverse relatively. The second joint portion and the second draw-in groove can set up to be the same structure with foretell first joint portion 821 and first draw-in groove 811 to in-process is applyed to the moment of torsion, the second holder can the chucking with the second installed part be connected, and can not take place to twist relatively and no longer describe here.
Foretell first installed part 81 can set up first boss 812 towards one end of first holder 82, the lateral surface of first boss 812 and the outer wall parallel and level of incidence pole 4, one side that first boss 812 deviates from first holder 82 is the plane and with the terminal surface looks butt of incidence pole 4, from this, can prevent that first installed part 81 from removing to incidence pole 4 when carrying out the loading test to test piece 5, avoided leading to the fact the influence because of first installed part 81 removes to incidence pole 4 and to the test of test piece 5. At least one pair of flat surfaces may be disposed on the outer circumferential wall of the first boss 812 along the radial direction to facilitate clamping when the first mounting member 81 is assembled and disassembled.
Similarly, the second installed part can be provided with the second boss on the one end towards the second holder, the lateral surface of second boss and the outer wall parallel and level that transmit pole 6, and the second boss deviates from one side of second holder for the plane and with the terminal surface butt that transmits pole 6, from this, can prevent to transmit pole 6 removal to the second installed part when carrying out the loading test to test piece 5, has avoided causing the influence to the test of test piece 5 because of the second installed part removes to transmitting pole 6. At least one pair of planes can be oppositely arranged on the peripheral wall of the second boss along the radial direction, so that the second mounting part can be conveniently clamped during dismounting.
Optionally, the first clamping member 82 and the second clamping member are both of a cylindrical structure, and the outer diameters of the first clamping member 82 and the second clamping member are the same as the outer diameters of the incident rod 4 and the transmission rod 6, so that the load transmitted by the incident rod 4 and the transmission rod 6 can be uniformly transmitted to the first clamping member 82 and the second clamping member, and the stress of the test piece 5 is uniform. In addition, as shown in fig. 7, at least one pair of flat surfaces may be disposed on the outer circumferential wall of the end of the first clamping member 82 facing the first mounting member 81 in a radial direction to be opposite to each other, so as to facilitate clamping when the first clamping member 82 and the first mounting member 81 are disassembled and assembled. Similarly, at least one pair of planes can be oppositely arranged on the outer peripheral wall of one end of the second clamping piece facing the second installation piece along the radial direction, so that the second clamping piece and the second installation piece can be conveniently clamped when being disassembled and assembled.
In some embodiments, the first axial compression device 2 may be an axial compression servo hydraulic cylinder, a piston rod of the axial compression servo hydraulic cylinder abuts against one end of the incident rod 4 away from the transmission rod 6, so that the axial compression servo hydraulic cylinder can apply pressure to the transmission rod 6 or remove the pressure applied to the transmission rod 6 by extending and retracting the piston rod; and the incident rod 4 can set up the bearing on the end far away from the transmission pole 6, so that the incident rod 4 can also rotate relative to the axle pressure servo hydraulic cylinder while lying in the butt joint of axle pressure servo hydraulic cylinder, so that the moment of torsion loading device 3 can not produce the damage to axle pressure servo hydraulic cylinder when exerting the moment of torsion to the incident rod 4.
Similarly, the second axial-pressure device 7 may also be an axial-pressure servo hydraulic cylinder, a piston rod of which is in contact with one end of the transmission rod 6 away from the incident rod 4, so that the axial-pressure servo hydraulic cylinder can apply pressure to the transmission rod 6 or remove the pressure applied to the transmission rod 6 by extending and retracting the piston rod.
In some embodiments, the torque loading device 3 may include a torque servo hydraulic cylinder, a rack and a gear engaged with each other, the rack is fixed on the base 1, and the gear is fixedly connected with the incident rod 4. Through setting up intermeshing's rack and gear for gear when rotating for the rack on fixedly connected to incident pole 4, the torque can be applyed to incident pole 4 to the gear. The rotation rate of the gear can be regulated and controlled, the control is convenient, the safety and the high efficiency of torque application are guaranteed, and the structure is simple and easy to realize. And the piston rod of the torque servo hydraulic cylinder is connected with the rack, and the piston rod of the torque servo hydraulic cylinder can be adjusted by controlling the pressure change in the torque servo hydraulic cylinder so as to enable the rack to move in a reciprocating manner, so that the gear is driven to rotate to apply torque to the incident rod 4.
Example two
The present embodiment further provides a testing method for testing type III fracture toughness of a material, which is applied to the apparatus 100 for testing type III fracture toughness of a material described in the first embodiment, as shown in fig. 8, and the testing method includes the following steps:
and S10, respectively connecting the data acquisition system to the incident rod and the transmission rod of the device.
And S20, fixing the test piece between the incident rod and the transmission rod.
And S30, applying pressure to the incident rod and the transmission rod through an axial compression device of the device to a preset pressure value.
And S40, applying torque to the incident rod through a torque loading device of the device until the test piece is broken.
And S50, recording data through the data acquisition system and calculating.
In this embodiment, the test method can be used for loading the test piece 5 by using the apparatus 100 for testing the type III fracture toughness of the material in the first embodiment, and the operation process of the test method is simple and easy to operate, so that the test method has great advantages in both the test equipment and the test steps. Moreover, the apparatus 100 applied in the testing method is the apparatus 100 for testing the type III fracture toughness of the material in the first embodiment, so that the testing method for testing the type III fracture toughness of the material can produce the same or similar beneficial effects as the apparatus 100 in the first embodiment, and further description thereof is omitted.
Specifically, in step S10, the data acquisition system may include a strain gauge, a bridge box, a strain amplifier, an oscilloscope, and a computer, wherein the strain gauge is attached to the incident rod 4 and the transmission rod 6 at an angle of 45 ° to the axial direction of the incident rod 4 and the transmission rod 6, so as to facilitate subsequent data processing, and then the strain gauge is electrically connected to the strain amplifier through the bridge box, the strain amplifier is electrically connected to the oscilloscope, and the oscilloscope is electrically connected to the computer, so as to analyze, calculate, and store the measured data at the computer end through software. In addition, in order to improve the testing precision, the upper side and the lower side of the same position of the incident rod 4 can be respectively pasted with a strain gauge, and the strain gauges are required to be air-dried for 1-2 days after being pasted on the incident rod 4, so that the strain gauges are better coupled with the pulse signals.
In step S20, the test piece 5 may be directly attached to the end of the incident rod 4 facing the transmission rod 6 by glue so that the test piece 5 can be fixed between the incident rod 4 and the transmission rod 6. A jig may be provided between the incident rod 4 and the transmission rod 6 to fix the test piece 5 to the jig, and the jig may include a first jig 8 and a second jig 9 which are oppositely provided. That is, one end of the first clamp 8 is fixed to the incident rod 4, and one end of the second clamp 9 is fixed to the transmission rod 6. At this time, fixing the test piece 5 between the incident rod 4 and the transmission rod 6 may include the steps of: the test piece 5 is glued to the first clamp 8 and/or to the second clamp 9. The test piece 5 can be prevented from damaging the incident rod 4 and the transmission rod 6 during the test while the test piece 5 is fixed between the incident rod 4 and the transmission rod 6.
In step S30, the power supply is turned on, the first axial pressing device 2 and the second axial pressing device 7 are set to the preset pressure values, and then the first axial pressing device 2 and the second axial pressing device 7 are started, so that the piston rod of the first axial pressing device 2 pushes the incident rod 4 to move under the action of the oil pressure, and the piston rod of the second axial pressing device 7 pushes the transmission rod 6 to move under the action of the oil pressure until the test piece 5 is in close contact with the fixture. At this time, the axial pressures of the first and second axial- pressure devices 2 and 7 continue to gradually increase up to the preset pressure value and are maintained at that value.
In step S40, the power supply is turned on, the torque servo hydraulic cylinder is started, the rack is controlled to gradually rise, and the gear is driven to rotate, because the gear is fixedly connected to the incident rod 4, the test piece 5 is fixed between the incident rod 4 and the transmission rod 6, that is, before the test piece 5 is not broken, the incident rod 4 is in a static state, at this time, one end of the incident rod 4, which is abutted to the first axial compression device 2, can rotate relative to the first axial compression device 2, that is, one end of the incident rod 4, which is abutted to the first axial compression device 2, belongs to a free end, and therefore, the torque energy applied to the incident rod 4 is stored on the incident rod 4 first. After the test piece 5 is broken, the incident rod 4 rotates until the torque energy stored on the incident rod 4 is released, and the incident rod 4 stops rotating. Meanwhile, the torque-adjustable servo hydraulic cylinder starts to release pressure until the oil pressure value of the torque-adjustable servo hydraulic rod is zero.
In step S50, incident waves, reflected waves and transmitted waves are measured by the strain gauge attached to the incident rod 4 and the transmitted rod 6, and the corresponding type iii fracture toughness is calculated by substituting the measured incident waves, reflected waves and transmitted waves into corresponding formulas.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. The device for testing the III-type fracture toughness of the material is characterized by being used for testing the III-type fracture toughness of a test piece, wherein the test piece is of a cylindrical structure, prefabricated cracks are arranged on the outer wall of the peripheral side of the test piece in a surrounding mode, and the prefabricated cracks extend along the axial direction and the radial direction of the test piece;
the device comprises:
a base;
the incident rod is arranged on the base and can move relative to the base;
the transmission rod and the incidence rod are coaxial and are arranged oppositely at intervals, when the III-type fracture toughness test is carried out on the test piece, the test piece is positioned between the incidence rod and the transmission rod, and the axial direction of the test piece is parallel to the axial direction of the incidence rod and the axial direction of the transmission rod;
the axial compression device comprises a first axial compression device and a second axial compression device which are arranged on the base, the first axial compression device is abutted against one end, far away from the transmission rod, of the incident rod and is in rotary connection with the incident rod, and the first axial compression device is used for applying pressure to the incident rod; the second axial pressing device is abutted against one end, far away from the incident rod, of the transmission rod and is used for applying pressure to the transmission rod;
the torque loading device is arranged on the base and connected with the incident rod and used for applying torque to the incident rod.
2. The apparatus of claim 1, wherein the ratio between the length of the specimen and the radius of the specimen is k, k L/R, wherein k is 2 ≦ 4, L is the length of the specimen, and R is the radius of the specimen.
3. The apparatus of claim 2, wherein the ratio of the depth of the pre-crack to the radius of the specimen is δ, δ h/R, where 0.4 δ 0.6 h the depth of the pre-crack.
4. The apparatus of claim 3, wherein the minimum radius of the test piece is R min ，
Dr is the outer diameter of the incident rod, Dr is more than or equal to 48mm and less than or equal to 52mm, and sigma is max Is the maximum axial pressure value, σ, of the device t Is the compressive strength of the test piece, F s Is the pressure safety factor of the device;
the radius R of the test piece ranges from,
5. the apparatus of claim 4, wherein the width of the pre-crack is no greater than 1 mm.
6. The apparatus for type III fracture toughness testing of materials of any of claims 1-5, wherein the pre-crack is located at an axially intermediate position of the test piece.
7. The apparatus according to any one of claims 1 to 5, further comprising a first clamp and a second clamp, wherein the first clamp and the second clamp are oppositely arranged, the first clamp is connected with the incident rod, the second clamp is connected with the transmission rod, the opposite surfaces of the first clamp and the second clamp are both flat, and when the test piece is subjected to the type III fracture toughness test, the test piece is fixed on the opposite surfaces of the first clamp and the second clamp.
8. The apparatus of claim 7, wherein the incident rod and the transmission rod are both circular ring tubular structures;
the first clamp comprises a first mounting piece and a first clamping piece, one end of the first mounting piece is embedded in the incident rod, a first clamping portion is arranged at one end, facing the first mounting piece, of the first clamping piece, and the first clamping piece is detachably connected with the first mounting piece through the first clamping portion;
the second anchor clamps include second installed part and second holder, the one end of second installed part is inlayed and is located in the transmission pole, the second holder orientation one of second installed part is served and is provided with second joint portion, the second holder passes through second joint portion with the connection can be dismantled to the second installed part.
9. A test method for testing type III fracture toughness of a material, wherein the test method is applied to the apparatus for testing type III fracture toughness of a material according to any one of claims 1 to 8, the test method comprising:
respectively connecting a data acquisition system to an incident rod and a transmission rod of the device;
fixing a test piece between the incident rod and the transmission rod;
applying pressure to the incident rod and the transmission rod through an axial compression device of the device to a preset pressure value;
applying torque to the incident rod through a torque loading device of the device until the test piece is broken;
and recording data through the data acquisition system and calculating.
10. The method of claim 9, wherein the apparatus comprises a fixture, the fixture comprises a first fixture and a second fixture, the first fixture and the second fixture are oppositely disposed, the first fixture is fixed on the incident rod, and the second fixture is fixed on the transmission rod;
the fixing the test piece between the incident rod and the transmission rod includes:
and bonding the test piece on the clamp.
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| CN202210627481.3A CN115014976A (en) | 2022-06-02 | 2022-06-02 | Device and method for testing III-type fracture toughness of material |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116625848A (en) * | 2023-05-18 | 2023-08-22 | 天津大学 | Composite loading device |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116625848A (en) * | 2023-05-18 | 2023-08-22 | 天津大学 | Composite loading device |
| CN116625848B (en) * | 2023-05-18 | 2024-01-09 | 天津大学 | Composite loading device |
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