Device and method for machining V-shaped notch in inner surface of hollow round bar sample

Abstract

The invention discloses a hollow round bar sample inner surface V-shaped notch machining device and method, and belongs to the field of metal performance testing and evaluation.The hollow round bar sample to be machined is horizontally fixed through a clamping and rotating unit and driven to rotate, and a counterweight tool is used for applying vertically-downward acting force to a vernier tool by adjusting the gravity of the counterweight tool to fix the vernier tool; the power device drives the balance weight tool to move in the horizontal direction, so that the vernier tool is provided with notches in the to-be-machined hollow round bar sample and the cavity along the comparison sample piece, the structure is simple, the machining precision is high, a V-shaped notch with a smooth surface can be machined in the workpiece according to the machining requirement of the fracture toughness test sample notch, and the machining efficiency is high. The fracture toughness test becomes possible, the test cost is reduced, the test period is shortened, the test efficiency is improved, the data acquisition is accelerated, the ductility reduction mechanism is found out and the like, and the long-time service reliability of the material in the low-temperature and high-pressure hydrogen environment is greatly improved.

Description

Technical Field

[0001] The present invention belongs to the field of metal performance testing and evaluation, and particularly relates to a device and method for machining a V-notch on the inner surface of a hollow round bar specimen. Background Art

[0002] In recent years, as one of the countermeasures to address the global warming issue, the new energy hydrogen energy industry for carbon dioxide elimination has attracted much attention, promoting the development and popularization of hydrogen fuel cell vehicles and supporting hydrogen refueling stations. To overcome the problem of limited driving range, the filling pressure of on-vehicle hydrogen tanks has been increased from the original 35 MPa to 70 MPa and above, enabling the driving range to be increased from 300 km to 500 km. On the other hand, due to the increase in the pressure of on-vehicle gas cylinders, the outlet pressure of hydrogen refueling stations is bound to increase. Currently, research is underway to obtain high-pressure hydrogen (>70 MPa) through the rapid gasification of liquid hydrogen. This requires obtaining material properties and evaluating hydrogen embrittlement tolerance under high-pressure hydrogen of 70 MPa and above and extremely low-temperature environments, which is difficult to achieve with traditional methods. To ensure the safe and reliable operation of hydrogen fuel cell vehicles and hydrogen refueling stations, key performance evaluation tests of metal materials in ultra-low-temperature and ultra-high-pressure hydrogen environments have become crucial.

[0003] Generally speaking, the more extreme the environment, the larger the devices required to form and maintain the environment, the higher the costs and manpower for operating and maintaining the equipment, and the greater the difficulty of conducting tests. Currently, there are few material testing devices under ultra-low temperatures below 77 K and ultra-high-pressure gas environments above 70 MPa worldwide. Japan has developed testing machines for testing in hydrogen environments in the 70 MPa to 100 MPa range and has started material evaluation, but the number is limited and it is difficult to fully address the urgent material selection situation. Generally, specimens are placed in a high-pressure container and loaded through a pull rod passing through the container. It is difficult to ensure the sealing between the pull rod and the container, and due to measurement errors caused by the internal pressure of the container and sealing friction, it is difficult to obtain the true elongation rate of the test specimen under the load actually borne in the high-pressure hydrogen environment, making it not easy to conduct the test. Additionally, it is very difficult to conduct tests under a high-pressure hydrogen environment, and combined with extremely low-temperature conditions, material performance testing under the coexistence of high-pressure hydrogen and extremely low temperature is a worldwide problem. In recent years, Japan has developed a hollow round bar specimen, filling high-pressure gas such as high-pressure hydrogen of 70 MPa and above inside the specimen. An ultra-low-temperature environment (77 K) is formed outside the specimen. By filling high-pressure gas inside the hollow round bar specimen and providing an ultra-low-temperature environment outside the specimen, low temperature and high pressure can be organically combined to complete the mechanical property testing of metal materials in low-temperature and high-pressure hydrogen environments. This method has the advantages of safety, high efficiency, low cost, and simple operation.

[0004] However, at present, during the high-pressure hydrogen tensile test, under the same hydrogen pressure conditions, there are large differences in the test results. As we all know, it takes three steps for high-pressure hydrogen to enter the interior of the metal sample, namely, the surface adsorption of hydrogen molecules, the dissociation of hydrogen molecules into hydrogen atoms and entering the metal surface, and the diffusion of hydrogen atoms into the metal. The different states of the metal surface have significant differences in the hydrogen adsorption process, resulting in differences in the hydrogen atoms entering the metal, which ultimately leads to large deviations in the test results of the sample. Therefore, a V-notch is machined on the surface of the sample to cause local stress concentration on the surface, making it easy for hydrogen atoms to adsorb, ensuring the accuracy and repeatability of the test results under high-pressure hydrogen environment. On the other hand, at present, hollow round rod specimens can only be used for simple material performance tests such as tensile tests and fatigue tests. For the fracture toughness test, which is closely related to the service performance of the material, it is still powerless. The reason is that it is impossible to accurately machine a V-notch at a specific position on the cylindrical cavity surface of the hollow round rod specimen. Summary of the invention

[0005] In order to overcome the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a device and method for processing a V-shaped notch on the inner surface of the cavity of a hollow round rod specimen, so as to solve the technical problem that the prior art cannot accurately process a V-shaped notch at a specific position on the cylindrical cavity surface of a hollow round rod specimen.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A V-notch processing device for the inner surface of a hollow round rod sample, comprising a clamping and rotating unit, a vernier tool, a counterweight tool and a power device;

[0008] The clamping and rotating unit fixes the clamping end of the hollow round rod sample to be processed, and the other end is provided with a vernier tool and a comparison sample. The comparison sample is arranged below the movable end of the vernier tool. The movable end of the vernier tool extends into the notch position inside the cavity of the hollow round rod sample to be processed, and contacts with the comparison sample, and is fixed by a counterweight fixture, and the power device is fixedly connected to the counterweight fixture to provide power for reciprocating circulation in the horizontal direction.

[0009] Preferably, the clamping and rotating unit comprises a motor, the motor is connected to a mechanical arm via a rotating shaft, and the mechanical arm clamps and fixes one end of the hollow round rod sample to be processed.

[0010] Preferably, the power device is connected to the vernier tool via a transmission shaft; and is fixedly connected to the counterweight tooling via bolts.

[0011] Preferably, the counterweight fixture is provided with a first knob and a second knob for adjusting the pressure applied to the vernier tool.

[0012] Preferably, the vernier tool includes a support rod and a scale. The support rod is telescopically arranged inside the scale and the telescopic length is fixed by a scale fixing screw. A processing cutting edge is arranged at the end of the support rod, and a thimble contacting the comparison sample is arranged in the middle thereof. One end of the processing cutting edge of the support rod extends into the position where a notch is to be formed inside the cavity of the to-be-processed hollow round bar sample. A scale is arranged on the scale for determining the extending length of the processing cutting edge.

[0013] Preferably, a cylindrical cavity with a length of 15 mm is extendedly arranged at the clamping end of the to-be-processed hollow round bar sample.

[0014] Preferably, the comparison sample is made from the cylindrical cavity at the clamping end of the to-be-processed hollow round bar sample. After the to-be-processed hollow round bar sample is processed, it is cut off and split into two along the axis. According to the processing requirements of the notch of the fracture toughness test sample, a circumferential notch is processed on the inner surface at the central position of the axis to form a V-notch.

[0015] The present invention also discloses a method for processing a V-notch on the inner surface of a hollow round bar sample, including the following steps:

[0016] Fix the clamping end of the to-be-processed hollow round bar sample on the clamping and rotating unit, arrange the comparison sample below the movable end of the vernier tool, and adjust the vernier tool according to the length of the comparison sample;

[0017] After the movable end of the vernier tool extends into the position where a notch is to be formed inside the cavity of the to-be-processed hollow round bar sample, fix the vernier tool by using a counterweight tooling and connect the power device;

[0018] After starting the clamping and rotating unit to drive the to-be-processed hollow round bar sample to a stable state, start the power device to drive the vernier tool to advance - retreat along the comparison sample towards one end of the to-be-processed hollow round bar sample;

[0019] After advancing - retreating for several cycles, the power device drives the vernier tool to withdraw from the cavity of the to-be-processed hollow round bar sample, and the processing is completed.

[0020] Preferably, the rotation speed of the clamping and rotating unit is greater than 5 - 20 rad / s; the advancing speed of the power device is 5 - 10 mm / min.

[0021] Preferably, a V-notch is formed on the comparison sample; the vernier tool includes a support rod, a processing cutting edge, a thimble, a scale and a scale fixing screw; the vernier tool advancing - retreating along the comparison sample towards one end of the to-be-processed hollow round bar sample specifically includes:

[0022] The thimble on the vernier tool walks along the right side of the V-notch from a position 5 mm to the right of the V-notch to the bottom of the V-notch and then goes up along the left side of the V-notch to the left surface of the V-notch.

[0023] The ejector pin moves in the opposite direction along the left side of the V-shaped notch to the bottom of the V-shaped notch, and then moves up along the right side of the V-shaped notch to the right surface of the V-shaped notch.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present application discloses a device for processing the V-notch on the inner surface of a hollow round rod sample, which adopts a clamping and rotating unit to horizontally fix and drive the hollow round rod sample to be processed to rotate, adopts a counterweight fixture to adjust its own gravity to apply a vertical downward force to the vernier tool to fix the vernier tool, and a power device drives the counterweight fixture to move in the horizontal direction, so that the vernier tool is moved along the comparison sample to the hollow round rod sample to be processed, and a notch is made inside the cavity. The device has a simple structure and high processing accuracy, and can process a V-notch with a smooth surface on the workpiece according to the processing requirements of the notch of the fracture toughness test sample, so that fracture toughness testing becomes possible, which is beneficial to reducing testing costs, shortening testing cycles, improving testing efficiency, accelerating data acquisition, and identifying the mechanism of ductility reduction, etc., and greatly improving the reliability of materials in long-term service in a low-temperature and high-pressure hydrogen environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural schematic diagram of the processing device of the present invention;

[0027] Figure 2 It is a structural schematic diagram of the vernier tool of the present invention.

[0028] Among them: 1-motor; 2-rotating axis; 3-mechanical arm; 4-hollow round rod sample to be processed; 5-comparison sample; 6-vernier tool; 601-support rod; 602-processing blade; 603-thimble; 604-ruler; 605-ruler fixing knob; 7-counterweight tooling; 701-first knob; 702-second knob. DETAILED DESCRIPTION

[0029] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not 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 should fall within the scope of protection of the present invention.

[0030] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0031] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0032] As is known to all, in order to reduce the cost of equipment for high-pressure gas environment, evaluate the fracture toughness performance of materials in high-pressure gas and ultra-low temperature environment, reduce testing costs, shorten the testing cycle, improve testing efficiency, speed up data acquisition, and identify the mechanism of ductility reduction. The present application can realize the processing of V-notch on the cylindrical cavity surface of hollow round rod specimens. In order to promote the construction of a society that utilizes hydrogen energy, the accuracy and repeatability of the test results must be guaranteed. More importantly, it is necessary to obtain the fracture toughness of materials under high-pressure and low-temperature conditions and obtain a large amount of material data as soon as possible. This is crucial for the reliability of materials in long-term service under low-temperature and high-pressure hydrogen environments. It is conducive to the realization of the infrastructure construction of a "hydrogen energy society" to promote diversified technological development and low cost, and reduce equipment costs, operating costs and even hydrogen procurement costs. The present invention provides a device and method for processing notches on the cylindrical cavity surface of a hollow round rod specimen, with simple steps and high processing accuracy, making it possible to test the fracture toughness of hollow round rod specimens in a high-pressure gas environment.

[0033] The present invention is achieved through the following technical solutions:

[0034] See also Figure 1The present application discloses a device for processing a V-shaped notch on the inner surface of a hollow round rod sample, comprising a clamping and rotating unit, a vernier tool 6, a counterweight fixture 7 and a power device 8; the clamping and rotating unit fixes the clamping end of the hollow round rod sample 4 to be processed, and the other end is provided with a vernier tool 6 and a comparison sample 5, the comparison sample 5 is arranged below the movable end of the vernier tool 6, the movable end of the vernier tool 6 extends to the notch position inside the cavity of the hollow round rod sample 4 to be processed, and contacts with the comparison sample 5, and is fixed by the counterweight fixture 7, and the power device 8 is fixedly connected to the counterweight fixture 7 to provide power for reciprocating circulation in the horizontal direction. A clamping rotation unit is used to horizontally fix and drive the hollow round rod sample to be processed to rotate, a counterweight fixture is used to adjust its own gravity to apply a vertical downward force to the vernier tool to fix the vernier tool, and a power device drives the counterweight fixture to move in the horizontal direction, so that the vernier tool is moved along the comparison sample to the hollow round rod sample to be processed, and a notch is opened inside the cavity. The structure is simple and the processing accuracy is high. A V-shaped notch with a smooth surface can be processed on the workpiece according to the processing requirements of the fracture toughness test sample notch, making fracture toughness testing possible, which is beneficial to reducing testing costs, shortening testing cycles, improving testing efficiency, accelerating data acquisition, and identifying the ductility reduction mechanism, etc., greatly improving the reliability of materials in long-term service in low-temperature and high-pressure hydrogen environments.

[0035] In some embodiments, see Figure 2 The vernier tool 6 includes a support rod 601 and a ruler 604. The support rod 601 is telescopically arranged in the ruler 604 and the telescopic length is fixed by the ruler fixing twist 605; a processing blade 602 is arranged at the end of the support rod 601, and a pin 603 in contact with the comparison sample 5 is arranged in the middle. One end of the processing blade 602 of the support rod 601 extends into the position of the notch inside the cavity of the hollow round rod sample 4 to be processed, and a scale is arranged on the ruler 604 for determining the extension length of the processing blade 602.

[0036] Preferably, the distance between the machining blade 602 and the right ejector pin 603 can be adjusted according to the length of the hollow round rod sample 4 to be machined.

[0037] In some embodiments, the clamping and rotating unit includes a motor 1, which is connected to a robotic arm 3 via a rotating shaft 2, and the robotic arm 3 clamps and fixes one end of a hollow round rod sample 4 to be processed.

[0038] In some embodiments, the power device 8 is connected to the vernier tool 6 via a transmission shaft 801 and is fixedly connected to the counterweight tool 7 via bolts.

[0039] In some embodiments, the counterweight fixture 7 is provided with a first knob 701 and a second knob 702 for adjusting the pressure applied to the vernier tool 6 .

[0040] In some embodiments, a cylindrical cavity with a length of 15 mm is provided at the clamping end of the hollow round bar specimen 4 to be processed.

[0041] Preferably, the comparison specimen 5 is made from the cylindrical cavity at the clamping end of the hollow round bar specimen 4 to be processed. After the hollow round bar specimen 4 to be processed is completed, it is cut off and split into two along the axis. According to the processing requirements of the notch of the fracture toughness test specimen, a circumferential notch is processed on the inner surface at the center position of the axis to form a V-notch.

[0042] The specific processing method is as follows:

[0043] 1. After the hollow round bar specimen is processed, cut off the extended 15-mm clamping end with a cylindrical cavity.

[0044] 2. Split the cut-off 15-mm clamping end with a cylindrical cavity into two along the axis to process it into a comparison specimen.

[0045] 3. According to the processing requirements of the notch of the fracture toughness test specimen, process a circumferential notch on the inner surface at the center position of the axis of the comparison specimen.

[0046] Figure 1 The motor 1 on the left drives the robotic arm 3 to rotate at high speed through the rotating shaft 2, and the robotic arm 3 fixes the hollow round bar specimen 4 to be processed in the horizontal position. Figure 1 On the right, the power device 8 provides power for the counterweight tooling 7 to move back and forth. The counterweight tooling 7 exerts a vertically downward force on the vernier tool 6 by adjusting its own gravity. The support rod 601 of the vernier tool 6 extends out, and the extension distance of the cutting edge 602 is determined by the scale 604 and fixed with the vernier fixing screw 605. The support rod 601 is inserted into the cavity of the hollow round bar specimen 4 to be processed, and the ejector pin 603 is placed at the right side position of the V-notch of the comparison specimen 5.

[0047] Preferably, the distance from the ejector pin 603 to the cutting edge 602 is not less than the distance from the V-notch of the comparison specimen 5 to the processing position inside the cavity of the hollow round bar specimen 4 to be processed, ensuring the effectiveness of the processing device.

[0048] Start the left motor 1, drive the robotic arm 3 to rotate at high speed through the rotating shaft 2, drive the hollow round bar specimen 4 to be processed to rotate at high speed in the horizontal position, and wait until its rotation is stable. Then start the right power device 8, drive the counterweight fixture 7 to move to the left, drive the cursor tool 6 to move to the left, and the thimble 603 moves slowly to the left along the surface of the comparison specimen 4. When it moves to the V-shaped edge of the comparison specimen, due to the vertical force provided by the counterweight fixture 7, the thimble 603 starts to walk along the V-shaped notch. When the thimble 603 completes one walk and reaches the left horizontal plane of the comparison specimen 5, stop walking further. At this time, start to move in the reverse direction. When the thimble 603 walks to the right horizontal plane of the comparison specimen 5, it completes a round trip. Walk back and forth 3 times in total to ensure that the V-shaped notch has a smooth surface.

[0049] The present invention also discloses a method for processing a V-shaped notch on the inner surface of a hollow round bar specimen, comprising the following steps:

[0050] S1: Fix the clamping end of the hollow round bar specimen 4 to be processed on the clamping and rotating unit, set the comparison specimen 5 below the movable end of the cursor tool 6, and adjust the cursor tool 6 according to the length of the comparison specimen 5;

[0051] S2: After the movable end of the cursor tool 6 extends into the cavity of the hollow round bar specimen 4 to the notch opening position, fix the cursor tool 6 with the counterweight fixture 7 and connect the power device 8;

[0052] S3: After starting the clamping and rotating unit to drive the hollow round bar specimen 4 to a stable state, start the power device 8 to drive the cursor tool 6 to advance - retreat along the comparison specimen 5 towards one end of the hollow round bar specimen 4;

[0053] S4: After advancing - retreating several times in a cycle, the power device 8 drives the cursor tool 6 to withdraw from the cavity of the hollow round bar specimen 4 to complete the processing.

[0054] In some embodiments, the rotation speed of the clamping and rotating unit is greater than 5 - 20 rad / s; the advancing speed of the power device 8 is 5 - 10 mm / min.

[0055] In some embodiments, a V-shaped notch is provided on the comparison specimen 5; the cursor tool 6 includes a support rod 601, a processing blade 602, a thimble 603, a scale 604, and a scale fixing knob 605; the cursor tool 6 advancing - retreating along the comparison specimen 5 towards one end of the hollow round bar specimen 4 specifically includes:

[0056] S301: The thimble 603 on the cursor tool 6 walks along the right side of the V-shaped notch from a position 5 mm to the right of the V-shaped notch to the bottom of the V-shaped notch and then moves upward along the left side of the V-shaped notch to the left surface of the V-shaped notch;

[0057] S302: The ejector pin 603 moves downward along the left side of the V-notch in the reverse direction to the bottom of the V-notch, and then moves upward along the right side of the V-notch to the right surface of the V-notch.

[0058] In some embodiments, a method for machining a V-notch on the inner surface of a hollow round bar specimen includes the following steps:

[0059] Step 1: First, horizontally fix the hollow round bar specimen to be machined on a rotating fixture, place the comparison specimen with a notch on a platform, and adjust the distance between the cutting edge and the ejector pin of the vernier tool according to the lengths of the hollow round bar specimen to be machined and the comparison specimen.

[0060] Step 2: Place the left cutting edge of the vernier tool at the notch position of the hollow round bar specimen to be machined, and place the right ejector pin at a position 5 mm to the right of the notch of the notch comparison specimen. After all positions are fixed, place the counterweight on the ejector pin.

[0061] Step 3: Start the rotating fixture with a rotation speed of 5 - 20 rad / s or more. After the rotation state is stable, start the power device and control the vernier tool to start pushing leftward at a pushing speed of 5 - 10 mm / min.

[0062] Step 4: When the ejector pin on the support rod of the vernier tool walks from the right side of the notch of the comparison specimen to the bottom of the notch, and then moves upward along the left side of the notch to the left surface of the notch. At this time, the ejector pin walks in the reverse direction from the left side position of the notch to the bottom of the notch, and then moves upward along the right side of the notch to the right surface of the notch, continues to push rightward, repeats back and forth 3 times, and finally the vernier tool exits the cylindrical cavity of the hollow round bar specimen to be machined.

[0063] Example 1:

[0064] S1: On the machining drawing of the hollow round bar specimen to be machined, increase the length of one side of the cylindrical cavity clamping end of the hollow round bar specimen to be machined by 15 mm. After the hollow round bar specimen to be machined is completed, cut off the extended 15 - mm section with the cylindrical cavity clamping end. Cut the cut 15 - mm section with the cylindrical cavity clamping end in half along the axis, and machine a circumferential V-notch on the inner surface at the center position of the axis of the comparison specimen according to the machining dimension requirements of the V-notch of the fracture toughness test specimen. Make a V-notch comparison specimen.

[0065] S2: Horizontally fix the hollow round bar specimen to be processed on the rotating robotic arm, fix the V-notch comparison specimen on the platform, measure the distance between the V-notch of the hollow round bar specimen to be processed and the V-notch of the comparison specimen, and accurately obtain the distance between the left cutting edge and the right thimble on the vernier tool according to the measured distance using the scale on the vernier tool. Place the left cutting edge of the vernier tool inside the cylindrical cavity of the hollow round bar specimen to be processed, and place the right thimble at a position 5 mm to the right of the V-notch of the notch comparison specimen. After all positions are determined, place the weight device on the vernier tool and perform gravity transfer using Knob 1 and Knob 2.

[0066] S3: Start the motor on the left side of the schematic diagram. The rotating shaft drives the robotic arm to rotate at a speed of more than 5 rad / s. After the rotating state is stable, start the power device on the right side. The rotating shaft drives the weight device and the vernier tool to move forward to the left together at a speed of 10 mm / min.

[0067] S4: When the right thimble of the vernier tool walks from the right side of the V-notch of the comparison specimen to the bottom of the V-notch, and then ascends along the left side of the V-notch to the left surface of the V-notch. At this time, the thimble walks from the left position of the V-notch to the bottom of the V-notch in the reverse direction, and then ascends along the right side of the V-notch to the right surface of the V-notch, and continues to move forward to the right, repeating back and forth 3 times. Finally, the vernier tool exits the cylindrical cavity of the hollow round bar specimen to be processed.

[0068] Example 2:

[0069] S1: On the processing drawing of the hollow round bar specimen to be processed, increase the length of one side of the cylindrical cavity clamping end of the hollow round bar specimen to be processed by 15 mm. After the hollow round bar specimen to be processed is completed, cut off the extended 15 mm with the cylindrical cavity clamping end. Cut the cut 15 mm long with the cylindrical cavity clamping end in half along the axis, and process a circumferential V-notch on the inner surface at the center position of the axis of the comparison specimen according to the processing dimension requirements of the V-notch of the fracture toughness test specimen. Make a V-notch comparison specimen.

[0070] S2: Horizontally fix the hollow round bar specimen to be processed on the rotating robotic arm, fix the V-notch comparison specimen on the platform, measure the distance between the V-notch of the hollow round bar specimen to be processed and the V-notch of the comparison specimen, and accurately obtain the distance between the left cutting edge and the right thimble on the vernier tool according to the measured distance using the scale on the vernier tool. Place the left cutting edge of the vernier tool inside the cylindrical cavity of the hollow round bar specimen to be processed, and place the right thimble at a position 5 mm to the right of the V-notch of the notch comparison specimen. After all positions are determined, place the weight device on the vernier tool and perform gravity transfer using Knob 1 and Knob 2.

[0071] S3: Start the motor on the left side of the schematic diagram. The rotating shaft drives the robotic arm to rotate at a speed of more than 20 rad / s. After the rotation state stabilizes, start the power device on the right side. The rotating shaft drives the counterweight tooling and the cursor tool to push leftward at a speed of 5 mm / min.

[0072] S4: When the right thimble of the cursor tool walks from the right side of the V-notch of the comparison sample to the bottom of the V-notch, and then ascends along the left side of the V-notch to the left surface of the V-notch. At this time, the thimble walks from the left position of the V-notch to the bottom of the V-notch in the reverse direction, and then ascends along the right side of the V-notch to the right surface of the V-notch, and continues to push rightward, repeating this process 3 times. Finally, the cursor tool withdraws from the cylindrical cavity of the hollow round bar sample to be machined.

[0073] The above content is only to illustrate the technical idea of the present invention, and the protection scope of the present invention cannot be limited thereby. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the claims of the present invention.

Claims

1. A device for machining a V-notch on the inner surface of a hollow round bar specimen, characterized in that, it includes a clamping and rotating unit, a vernier cutter (6), a counterweight tooling (7) and a power device (8); The clamping and rotating unit fixes the clamping end of the hollow round bar specimen (4) to be machined, and a vernier cutter (6) and a reference specimen (5) are arranged at the other end. The reference specimen (5) is arranged below the movable end of the vernier cutter (6). The movable end of the vernier cutter (6) extends into the position where the notch is to be machined inside the cavity of the hollow round bar specimen (4) to be machined, and contacts the reference specimen (5), and is fixed by the counterweight tooling (7), and the power device (8) is fixedly connected to the counterweight tooling (7) to provide power for reciprocating circulation in the horizontal direction.

2. The device for machining a V-notch on the inner surface of a hollow round bar specimen according to claim 1, characterized in that, the clamping and rotating unit includes a motor (1), the motor (1) is connected with a robotic arm (3) through a rotating shaft (2), and the robotic arm (3) clamps and fixes one end of the hollow round bar specimen (4) to be machined.

3. The device for machining a V-notch on the inner surface of a hollow round bar specimen according to claim 1, characterized in that, the power device (8) is connected with the vernier cutter (6) through a transmission shaft (801); and is fixedly connected to the counterweight tooling (7) through bolts.

4. The device for machining a V-notch on the inner surface of a hollow round bar specimen according to claim 1, characterized in that, the counterweight tooling (7) is provided with a first knob (701) and a second knob (702) for adjusting the magnitude of the pressure exerted on the vernier cutter (6).

5. The device for machining a V-notch on the inner surface of a hollow round bar specimen according to claim 1, characterized in that, the vernier cutter (6) includes a support rod (601) and a scale (604), the support rod (601) is telescopically arranged in the scale (604) and the telescopic length is fixed by a scale fixing twist (605); a machining cutting edge (602) is arranged at the end of the support rod (601), and a thimble (603) in contact with the reference specimen (5) is arranged in the middle thereof. One end of the machining cutting edge (602) of the support rod (601) extends into the position where the notch is to be machined inside the cavity of the hollow round bar specimen (4) to be machined, and the scale (604) is provided with scales for determining the extending length of the machining cutting edge (602).

6. The device for machining a V-notch on the inner surface of a hollow round bar specimen according to claim 1, characterized in that, a cylindrical cavity with a length of 15 mm is extended at the clamping end of the hollow round bar specimen (4) to be machined.

7. The device for machining a V-notch on the inner surface of a hollow round bar specimen according to claim 6, characterized in that, the reference specimen (5) is made from the cylindrical cavity at the clamping end of the hollow round bar specimen (4) to be machined. After the hollow round bar specimen (4) to be machined is processed, it is cut off and split in half along the axis. According to the machining requirements of the notch of the fracture toughness test specimen, a circumferential notch is machined on the inner surface at the central position of the axis to form a V-notch.

8. A method for machining a V-notch on the inner surface of a hollow round bar specimen, characterized in that, Adopt the inner surface V-notch processing device for the hollow round bar specimen described in any one of claims 1 to 7, including the following steps: Fix the clamping end of the hollow round bar specimen (4) to be processed on the clamping and rotating unit, set the comparison specimen (5) below the movable end of the vernier tool (6), and adjust the vernier tool (6) according to the length of the comparison specimen (5); After the movable end of the vernier tool (6) extends into the cavity of the hollow round bar specimen (4) to be processed at the notch opening position, fix the vernier tool (6) with the weight-bearing tooling (7), and connect the power device (8); After starting the clamping and rotating unit to drive the hollow round bar specimen (4) to be processed to a stable state, start the power device (8) to drive the vernier tool (6) to advance - retreat along the comparison specimen (5) towards one end of the hollow round bar specimen (4) to be processed; After cycling the advance - retreat several times, the power device (8) drives the vernier tool (6) to withdraw from the cavity of the hollow round bar specimen (4) to be processed, and the processing is completed.

9. A method for processing an inner surface V-notch of a hollow round bar specimen according to claim 8, characterized in that, the rotation speed of the clamping and rotating unit is greater than 5 - 20 rad / s; the advance speed of the power device (8) is 5 - 10 mm / min.

10. A method for processing an inner surface V-notch of a hollow round bar specimen according to claim 8, characterized in that, a V-notch is provided on the comparison specimen (5); the vernier tool (6) includes a support rod (601), a processing cutting edge (602), a thimble (603), a scale (604) and a scale fixing knob (605); The advance - retreat of the vernier tool (6) along the comparison specimen (5) towards one end of the hollow round bar specimen (4) to be processed specifically includes: The thimble (603) on the vernier tool (6) walks along the right side of the V-notch from a position 5 mm to the right of the V-notch to the bottom of the V-notch, and then ascends along the left side of the V-notch to the left surface of the V-notch; The thimble (603) descends along the left side of the V-notch in the reverse direction to the bottom of the V-notch, and then ascends along the right side of the V-notch to the right surface of the V-notch.

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