Device and method for testing fracture toughness of Charpy-like impact sample in low-temperature environment

Abstract

The invention provides a device and method for testing the fracture toughness of a Charpy-like impact sample in a low-temperature environment, and the device comprises an environment box system which is used for providing a low-temperature test environment; the frame system is located in the environment box system, the sample is located in the frame system, a boss is arranged at the bottom of the frame system, and the bottom end of the boss is an arc surface; the loading system comprises a pressure head and a lower guide rod, the lower guide rod is upwards inserted into the environment box system, the pressure head is downwards inserted into the frame system, the boss is located above the lower guide rod, the sample is located below the pressure head, and a notch of the sample is located on a connecting line of the pressure head and the center of the bottom end of the boss; and the measuring system is used for measuring test data. A low-temperature test environment is provided through the low-temperature test box, the purpose of testing the fracture toughness of the Charpy-like impact sample in the low-temperature environment can be achieved, and the device has the advantages that clamping is convenient in the test process, automatic centering is achieved, and the test error is small; meanwhile, test material consumption is reduced, and cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of sample fracture toughness testing, and in particular to a device and method for testing the fracture toughness of a Charpy-like impact sample under a low temperature environment. Background Art

[0002] With the development of modern economy, environmental pollution and energy crisis have prompted "energy saving, energy storage, environmental protection, and sustainability" to become the consensus of development in countries around the world. At the same time, it has also prompted industries such as petrochemicals, power generation, and steel to develop towards high parameters, high production capacity, and extreme service environments. The dangers are also more significant, bringing huge pressure and challenges to the safe operation of equipment.

[0003] Fracture toughness refers to the ability of a material to resist crack propagation, and is a very important indicator for the safety assessment of pressure-bearing equipment with defects. Common traditional fracture toughness test specimens are compact tension (CT) specimens and three-point bending (SEB) specimens, but these conventional mechanical testing methods require large metal specimens, consume a lot of test materials, and are costly.

[0004] Similar to the Charpy impact specimen, the Charpy-like impact specimen is a metal specimen with a U-shaped notch or a V-shaped notch. It can meet the fracture toughness test requirements with a smaller volume and has a low material cost.

[0005] However, conventional three-point bending fixtures require a larger clamping area; and for Charpy-like impact specimens, the loading end needs to be aligned with the material notch when clamping the specimen to reduce the error, and the conventional three-point bending fixture alignment process is cumbersome, so it is not suitable for Charpy-like impact specimens. It is necessary to develop a low-temperature three-point bending loading device suitable for Charpy-like impact specimens. Summary of the invention

[0006] The purpose of the present invention is to provide a device and method for testing the fracture toughness of a Charpy-like impact specimen in a low temperature environment, which can be easily clamped, automatically aligned, and reduce the consumption of test materials and the cost;

[0007] The present invention provides a fracture toughness testing device for a Charpy-like impact specimen in a low-temperature environment, comprising: an environmental chamber system, for providing a low-temperature test environment; a frame system, wherein the frame system is located in the environmental chamber system, the specimen is located in the frame system, a boss is provided at the bottom of the frame system, and the bottom end of the boss is an arc surface; a loading system, wherein the loading system comprises a pressure head and a lower guide rod, wherein the lower guide rod is inserted upward into the environmental chamber system, and the pressure head is inserted downward into the frame system, the boss is located above the lower guide rod, the specimen is located below the pressure head, and a notch of the specimen is located on a line connecting the pressure head and the center of the bottom end of the boss; and a measuring system, wherein the measuring system is used to measure test data.

[0008] Furthermore, the loading system also includes an upper guide rod, which is inserted downward into the environmental chamber system, the frame system is located between the upper guide rod and the lower guide rod, and the pressure head is detachably connected to the upper guide rod.

[0009] Furthermore, it also includes a heat preservation system, which includes an external constant temperature water tank. The upper guide rod and the lower guide rod are provided with heat preservation channels, and the heat preservation channels are connected to the constant temperature water tank through pipelines.

[0010] Furthermore, it also includes a flexible lifting system, which is connected to the frame system and is used to control the lifting of the frame system.

[0011] Furthermore, the flexible lifting system includes a lifting rope, the frame system includes a loading frame, and the two lifting ropes are respectively connected to two lifting ears on the top of the loading frame.

[0012] Furthermore, the boss is arranged at the bottom of the loading frame, a pad is connected to the lower guide rod, and the boss is located above the pad.

[0013] Furthermore, it also includes a positioning system, which is located in the frame system and is used to position the sample.

[0014] Furthermore, the positioning system includes a positioning base and a positioning fixture, the positioning base is fixed in the frame system, the positioning fixture is detachably connected to the positioning base, and the test is located on the positioning base and between the positioning fixtures.

[0015] Furthermore, the positioning system also includes a cylindrical rod and grooves opened on the positioning base, the number of the grooves is at least two and the grooves are opened at a distance between each other, a cylindrical rod is placed in each of the grooves, the top of the cylindrical rod is located above the notch of the groove, and the sample is placed on the cylindrical rod.

[0016] The present invention also provides a testing method for a fracture toughness testing device of a Charpy-like impact specimen under a low temperature environment, comprising the following steps: S1, selecting a suitable indenter; S2, placing the specimen into a frame system, and adjusting the position of the specimen so that the end of the indenter is located on the back side of the notch of the specimen, and the indenter is pressed on the specimen; S3, the lower guide rod of the testing machine rises and contacts the bottom arc surface of the bottom boss of the frame system; S4, using an environmental chamber system to cool the specimen, and after reaching the required temperature, keeping the temperature for a period of time, starting the test at a set loading rate, and ending the test when the specimen fractures; S5, using a measurement system to collect data during the test to obtain fracture toughness data.

[0017] The technical solution of the present invention adopts a Charpy-like impact specimen to perform a fracture toughness test, which reduces the material consumption required for the specimen and reduces the cost; the specimen is placed through a frame system, and an arc surface boss is arranged at the bottom of the frame system, so that when the lower guide rod rises for loading, it can first contact the center of the bottom arc surface, thereby forming a loading position, a specimen notch and a pressure head with three points in a straight line, which can achieve the effect of automatic centering and small test error, and at the same time, a low-temperature test environment is provided through an environmental chamber system. Compared with the traditional fracture toughness test, the purpose of the fracture toughness test of the Charpy-like impact specimen in a low-temperature environment can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 It is a schematic diagram of the environmental chamber system, frame system and loading system of the present invention;

[0020] Figure 2 is a schematic diagram of a positioning system of the present invention;

[0021] Figure 3 It is a schematic diagram of the test state of the sample of the present invention;

[0022] Description of reference numerals:

[0023] 1-environmental chamber system; 101-chamber;

[0024] 2-frame system; 201-loading frame; 202-boss; 203-arc surface;

[0025] 3-loading system; 301-upper guide rod; 302-lower guide rod; 303-pressing head; 304-shielding plate;

[0026] 4-Lifting rope;

[0027] 5-positioning system; 501-positioning base; 502-positioning fixture; 503-bolt; 504-groove; 505-cylindrical rod

[0028] 6-sample; 601-notch. DETAILED DESCRIPTION

[0029] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0031] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined. In addition, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0032] Example 1

[0033] like Figure 1-Figure 3 As shown, the present invention provides a fracture toughness testing device for a Charpy-like impact specimen in a low-temperature environment, comprising: an environmental chamber system 1, for providing a low-temperature test environment; a frame system 2, the frame system 2 is located in the environmental chamber system 1, the specimen 6 is located in the frame system 2, a boss 202 is provided at the bottom of the frame system 2, and the bottom end of the boss 202 is an arc surface 203; a loading system 3, the loading system 3 comprises a pressure head 303 and a lower guide rod 302, the lower guide rod 302 is inserted upward into the environmental chamber system 1, the pressure head 303 is inserted downward into the frame system 2, the boss 202 is located above the lower guide rod 302, the specimen 6 is located below the pressure head 303, and the notch 601 of the specimen 6 is located on the line connecting the pressure head 303 and the center of the bottom end of the boss 202; a measuring system (not shown), the measuring system is used to measure test data.

[0034] Specifically, the sample 6 used in the present invention is a Charpy-like impact sample, and a notch 601 is provided on one side (specifically the middle part) of the sample 6 , and the indenter 303 is against the back side of the notch 601 on the sample 6 .

[0035] The environmental chamber system 1 is a closed box 101 structure, which is composed of the box 101, a thermocouple (for temperature measurement) and an external low-temperature supply input device (such as a self-pressurized liquid nitrogen tank) so as to maintain the required low-temperature environment during the test, thereby achieving the purpose of Charpy-like impact specimen fracture toughness testing in a low-temperature environment.

[0036] The frame system 2 is movable up and down in the box 101. Before loading, the frame system 2 is first lowered so that the sample 6 can be placed in the box 101 and under the pressure head 303. Then the frame system 2 is moved upward to adjust the position of the back side of the Charpy impact sample pressure notch 601 to be pressed by the pressure head 303. The arc surface 203 at the bottom end of the boss 202 can facilitate the free centering of the loading frame 201, ensure that the pressure head 303 does not generate additional torque, and ensure the accuracy of the test results.

[0037] The lower guide rod 302 is connected to the loading device (such as a hydraulic system), and is inserted into the box 101 in a sealed manner upward, and can move up and down in the box 101 (or move up and down using a sleeve structure). When the lower guide rod 302 rises to contact the frame system 2, the boss 202 at the bottom of the frame system 2 is similar to a tumbler structure, and the arc surface 203 at its bottom automatically contacts and bears the loading force (the center of the arc) in the process of contacting the lower guide rod 302 and gradually receiving force, and the notch 601 of the sample 6 is located on the line connecting the pressure head 303 and the center of the bottom end of the boss 202, so that indirectly, the loading force applied by the loading system 3 to the sample 6 can be automatically centered, ensuring that the pressure head 303 does not generate additional torque, thereby ensuring the accuracy of the test results.

[0038] The measurement system is composed of sensors, computers, etc., in order to collect real-time data such as force and displacement during the test and convert the measured data into fracture toughness. Alternatively, an electron microscope can be used to observe the cross section of the material. These methods are commonly used in existing test processes and will not be described in detail.

[0039] Example 2

[0040] The loading system 3 further includes an upper guide rod 301, which is inserted downward into the environmental chamber system 1, the frame system 2 is located between the upper guide rod 301 and the lower guide rod 302, and the pressure head 303 is detachably connected to the upper guide rod 301. It also includes a heat preservation system (not shown), which includes an external constant temperature water tank, and heat preservation channels are provided in the upper guide rod 301 and the lower guide rod 302, and the heat preservation channels are connected to the constant temperature water tank through pipes.

[0041] Specifically, the upper guide rod 301 is inserted downward into the box body 101 of the environmental chamber system 1, and the pressure head 303 and the upper guide rod 301 are detachably connected by threads, and different types of pressure heads 303 can be replaced according to different samples 6; the pressure head 303 is inserted downward into the loading frame 201 of the frame system 2; the present invention adopts lower loading, the upper guide rod 301 is connected to the pressure head 303 and is held against the back side of the pressure notch 601 of the Charpy-like impact specimen, and is raised by the lower guide rod 302 through the loading frame 201 system 2 to perform a fracture test.

[0042] The insulation system is composed of an external constant temperature water tank, a rubber hose and a connector. A channel for the flow of insulation water is provided in the upper and lower guide rods 302. The channel penetrates through the end of the upper and lower guide rods 302 away from the sample 6 to form a through hole. The through hole is connected to the constant temperature water tank through a connector and a rubber hose. A circulating pump can also be set to circulate the flow so that the upper guide rod 301 and the lower guide rod 302 can be kept at room temperature during the test to prevent low temperature from being transmitted to the loading mechanism and damaging the equipment.

[0043] Example 3

[0044] It also includes a flexible lifting system, which is connected to the frame system 2 and is used to control the lifting of the frame system 2. The flexible lifting system includes a lifting rope 4, and the frame system 2 includes a loading frame 201. Two lifting ropes 4 are respectively connected to two lifting ears at the top of the loading frame 201. The boss 202 is set at the bottom of the loading frame 201, and the lower guide rod 302 is connected to a pad 304, and the boss 202 is located above the pad 304.

[0045] Specifically, the flexible lifting system is used to fix the loading frame 201 when installing and removing the sample 6. The frame system 2 is suspended in the box 101 by the suspension rope 4, and is moved up and down in the box 101 by pulling up or down the suspension rope 4, and when the pressure head 303 is connected to the upper guide rod 301 and passes downward through the loading frame 201, the suspension rope 4 pulls the loading frame 201 to slide up and down in the direction of the pressure head 303 / upper guide rod 301. The other end of the suspension rope 4 can be connected to the pulley and the hoisting mechanism.

[0046] The pad 304 is connected to the lower guide rod 302 by threads to apply load to the arc surface 203 at the bottom end of the boss 202, which can protect the lower guide rod 302. When the pad 304 is worn out with the number of tests, the pad 304 can be replaced to ensure the accuracy of the test data.

[0047] Example 4

[0048] It also includes a positioning system 5, which is located in the frame system 2 and is used to position the sample 6. The positioning system 5 includes a positioning base 501 and a positioning fixture 502. The positioning base 501 is fixed in the frame system 2, and the positioning fixture 502 is detachably connected to the positioning base 501. The test is located on the positioning base 501 and between the positioning fixtures 502. The positioning system 5 also includes a cylindrical rod 505 and grooves 504 opened on the positioning base 501. The number of the grooves 504 is at least two and the spacing between them is opened. A cylindrical rod 505 is placed in each groove 504, and the top of the cylindrical rod 505 is located above the notch of the groove 504. The sample 6 is placed on the cylindrical rod 505.

[0049] Specifically, the positioning base 501 is a block structure, and at least two of them are provided, and are fixed on the inner bottom plate of the loading frame 201 at intervals, so that the sample 6 placed thereon is suspended at a certain height. On each positioning base 501, a positioning fixture 502 is fixed by two bolts 503, and the positioning fixture 502 is a U-shaped structure with a groove formed in the middle, which is used to clamp the two ends of the sample 6.

[0050] The groove 504 is a V-shaped groove, which has an automatic centering effect, and can also adjust the support height of the sample 6 according to the cylindrical rod 505 of different diameters placed in the V-shaped groove 504. After the cylindrical rod 505 is placed in the V-shaped groove 504, part of it is located in the V-shaped groove 504, and part of it extends upward from the V-shaped groove 504 to support the sample 6 suspended in the air. In addition, there is only a linear contact area between the top of the cylindrical rod 505 and the bottom of the sample 6. Compared with the surface contact area formed by placing the sample 6 on a plane, because the contact area is very small, the present invention can generate no additional torque on the sample 6 during the loading process, thereby improving the accuracy of the test results.

[0051] Example 5

[0052] The present invention also provides a testing method for a fracture toughness testing device of a Charpy-like impact specimen under a low temperature environment, comprising the following steps: S1, selecting a suitable pressure head 303 to be connected to an upper guide rod 301; S2, placing a specimen 6 into a frame system 2, and adjusting the position of the specimen 6 so that the end of the pressure head 303 is located on the back side of a notch 601 of the specimen 6, and the pressure head 303 is pressed on the specimen 6; S3, the lower guide rod 302 of the testing machine rises and contacts the bottom arc surface 203 of the bottom boss 202 of the frame system 2; S4, cooling the specimen 6 by using the environmental chamber system 1, and after reaching the required temperature, keeping the temperature for a period of time, starting the test at a set loading rate, and ending the test by causing the specimen 6 to fracture; S5, collecting data during the test by using a measurement system to obtain fracture toughness data.

[0053] Specifically, before the test, select a suitable pressure head 303 to connect to the upper guide rod 301, then use the suspension rope 4 to fix the loading frame 201, then place the cylindrical rod 505 on the V-shaped groove 504, then place the sample 6 on the cylindrical rod 505, and adjust the position of the sample 6 to ensure that the end of the pressure head 303 is located on the back side of the middle notch 601 of the sample 6. Pull up the suspension rope 4 to slowly lift the loading frame 201 so that the pressure head 303 presses on the sample 6, then move the lower guide rod 302 of the test machine to rise, and when the pad 304 and the circular boss 202 at the lower end of the loading frame 201 are in contact (at this time, the test machine measurement system can show that there is a load, but the load value should not exceed 200N), the suspension rope 4 can be loosened, and the entire clamping process of the sample 6 is completed. Then turn on the insulation system, and use the low temperature environment box system 1 to cool down the sample 6. After reaching the required temperature, keep it warm for a period of time, start the test at the set loading rate, and end the test when the sample 6 breaks. The measurement system is used to collect real-time data such as force and displacement during the test, and finally the measured data is converted into fracture toughness.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A Charpy-like impact specimen fracture toughness test device under low temperature environment, characterized in that: include: Environmental chamber system, used to provide low temperature test environment; A frame system, wherein the frame system is located in the environmental chamber system, the sample is located in the frame system, a boss is provided at the bottom of the frame system, and the bottom end of the boss is an arc surface; A loading system, wherein the loading system comprises a pressure head and a lower guide rod, wherein the lower guide rod is inserted upward into the environmental chamber system, and the pressure head is inserted downward into the frame system, wherein the boss is located above the lower guide rod, the sample is located below the pressure head, and the notch of the sample is located on the line connecting the pressure head and the center of the bottom end of the boss; A measuring system is used to measure test data.

2. The device for testing the fracture toughness of Charpy-like impact specimens under low temperature environment according to claim 1, characterized in that: The loading system further comprises an upper guide rod, which is inserted downward into the environmental chamber system, the frame system is located between the upper guide rod and the lower guide rod, and the pressure head is detachably connected to the upper guide rod.

3. The device for testing the fracture toughness of Charpy-like impact specimens under low temperature environment according to claim 2, characterized in that: It also includes a heat preservation system, which includes an external constant temperature water tank. Heat preservation channels are arranged in the upper guide rod and the lower guide rod, and the heat preservation channels are connected to the constant temperature water tank through pipelines.

4. The device for testing the fracture toughness of Charpy-like impact specimens in a low temperature environment according to claim 1, characterized in that: It also includes a flexible lifting system, which is connected to the frame system and is used to control the lifting of the frame system.

5. The device for testing the fracture toughness of Charpy-like impact specimens in a low temperature environment according to claim 4, characterized in that: The flexible lifting system comprises a lifting rope, and the frame system comprises a loading frame. The two lifting ropes are respectively connected to two lifting ears on the top of the loading frame.

6. The device for testing the fracture toughness of Charpy-like impact specimens in a low temperature environment according to claim 5, characterized in that: The boss is arranged at the bottom of the loading frame, a pad is connected to the lower guide rod, and the boss is located above the pad.

7. The device for testing the fracture toughness of Charpy-like impact specimens in a low temperature environment according to claim 1, characterized in that: Also included is a positioning system, which is located in the frame system and is used for positioning the sample.

8. The device for testing the fracture toughness of Charpy-like impact specimens in a low temperature environment according to claim 7, characterized in that: The positioning system comprises a positioning base and positioning fixtures. The positioning base is fixed in the frame system. The positioning fixtures are detachably connected to the positioning base. The sample is located on the positioning base and between the positioning fixtures.

9. The device for testing the fracture toughness of Charpy-like impact specimens in a low temperature environment according to claim 8, characterized in that: The positioning system also includes a cylindrical rod and grooves opened on the positioning base. The number of the grooves is at least two and the grooves are opened at a distance between each other. A cylindrical rod is placed in each groove. The top of the cylindrical rod is located above the notch of the groove, and the sample is placed on the cylindrical rod.

10. A testing method based on the Charpy-like impact specimen fracture toughness testing device under low temperature environment according to any one of claims 1 to 9, characterized in that: The steps include: S1, select a suitable pressure head; S2, place the sample into the frame system, and adjust the position of the sample so that the end of the indenter is located on the back side of the notch of the sample and the indenter is pressed on the sample; S3, the lower guide rod of the testing machine rises and contacts the bottom arc surface of the bottom boss of the frame system; S4, use the environmental chamber system to cool the sample. After reaching the required temperature, keep it warm for a period of time, and start the test at the set loading rate until the sample breaks and ends the test; S5, using the measurement system to collect data during the test and obtain fracture toughness data.

Images