A material fracture toughness testing apparatus and method

Abstract

The embodiment of the application provides a material fracture toughness testing device and method, and relates to the technical field of material fracture toughness testing.The device comprises a support assembly, which comprises a workpiece platform and two support rollers;two mark points P1 and P2 are arranged on the parallel lines along the axes of the two support rollers on the A plane of the workpiece platform;the loading assembly comprises a liftable loading roller;two first light emitters are arranged on the two sides of the bottom of the loading roller, and the projection points of the two first light emitters on the A plane are O1 and O2;an image recognition system is arranged and is used for acquiring the images of P1, P2, O1 and O2;the control system is used for controlling the translation and rotation of the workpiece platform, so that the line segment P1P2 is collinear with the line segment O1O2;the auxiliary positioning structure comprises a limiting element and a second light emitter, and can ensure that the prefabricated notch of the test workpiece is accurately located directly below the axis of the loading roller.The application can ensure that the test workpiece meets the spatial geometric constraint conditions of the fracture toughness test, and improves the accuracy and reliability of the test.

Description

Technical Field

[0001] This invention relates to the field of material fracture toughness testing technology, and in particular to a material fracture toughness testing device and method. Background Technology

[0002] In the field of materials mechanical property evaluation, fracture toughness is a crucial indicator of a material's resistance to crack propagation, playing a key role, especially in engineering structural materials with high safety requirements. To accurately obtain this parameter, standardized fracture toughness testing methods often employ a three-point bending loading mode, which uses a loading device with a specific geometric layout to stably load a pre-cracked specimen. Ideally, the loading system must meet the following geometric constraints: parallelism and symmetry between the loading roller and the support roller, and orthogonality between the specimen axis and the axes of each roller, to ensure uniform load application to the crack tip and avoid introducing unexpected additional stress. However, in practice, due to the lack of precise positioning and adjustment mechanisms, existing testing devices generally rely on the operator's experience to align the specimen and loading components, making it difficult to effectively guarantee the spatial geometric relationship between multiple axes. Existing geometric deviations introduce additional bending moments, significantly affecting the accuracy and reliability of fracture toughness test data. Summary of the Invention

[0003] To address the technical problem in existing technologies where material fracture toughness testing relies on manual visual positioning, leading to sample orientation deviations and introducing additional bending moments that affect the accuracy and reliability of test data, this invention provides a material fracture toughness testing device and method. The technical solution is as follows:

[0004] This invention provides a material fracture toughness testing device, comprising:

[0005] The support assembly includes: a workpiece platform and two support rollers; the two support rollers are arranged in parallel on plane A of the workpiece platform, and the support rollers are used to support the test workpiece; two marking points P1 and P2 are provided on plane A along the symmetry line of the axes of the two support rollers.

[0006] The loading component includes: a liftable loading roller; the loading roller is horizontally arranged above the workpiece platform, and a first light emitter is respectively provided at two points along the axial direction at the bottom of the loading roller;

[0007] The image recognition system acquires images of two marker points P1 and P2, as well as images of the projection points O1 and O2 of the beam emitted by the first emitter onto plane A. A rectangular coordinate system is established on plane A, with the center point of O1 and O2 as the origin O, the direction of the line connecting O1 and O2 as the x-axis, and the direction passing through point O and perpendicular to the x-axis as the y-axis. The system acquires the coordinates of the two marker points P1(x1, y1) and P2(x2, y2) on plane A. Based on the coordinates of P1 and P2, the system calculates the coordinates (x1, y1) of the center point P of line segment P1P2. p ,y p ), and the angle α between line segment P1P2 and line segment O1O2;

[0008] The control system, connected to the image recognition system and workpiece platform, is used to determine the coordinates (x, y) of the center point P. p ,y p The workpiece platform is controlled to translate so that point P coincides with the origin O. The workpiece platform is then controlled to rotate according to the included angle α so that line segment P1P2 is collinear with line segment O1O2.

[0009] Alternatively, the angle α between line segments P1P2 and O1O2 can be obtained using the following formula (1):

[0010]

[0011] Optionally, the image recognition system includes:

[0012] An industrial camera is fixed above the workpiece platform, facing plane A, and is used to acquire images of marker points P1 and P2 and projection points O1 and O2.

[0013] The image processing unit is used to establish a rectangular coordinate system on plane A based on the images of P1, P2, O1, and O2, with the center point of O1 and O2 as the origin O, the direction of the line connecting O1 and O2 as the x-axis, and the direction passing through point O and perpendicular to the x-axis as the y-axis, and to obtain the coordinates of P1 and P2 in the rectangular coordinate system; and to calculate the coordinates (x1, y1) of the center point P of line segment P1P2 based on the coordinates (x2, y2) of P1 and (x1, y1) of P2. p ,y p ), and the included angle α between line segment P1P2 and line segment O1O2, so that the axes of the two support rollers and the loading roller are parallel to each other;

[0014] The auxiliary positioning structure includes a limiting element that abuts against the end of the test workpiece. The tangent direction of the abutment surface is perpendicular to the axis direction of the two support rollers, so that the axis of the test workpiece is orthogonal to the axes of the two support rollers and the loading roller.

[0015] Optionally, the control system includes: a central control module and a drive module; the central control module is used to determine the coordinates (x, y) of the center point P. p ,y p The angle α controls the movement of the drive module;

[0016] The driving module includes:

[0017] The first translation mechanism is used to drive the workpiece platform to translate a distance x along the x-axis. p To adjust the position of the center point P on the x-axis;

[0018] The second translation mechanism is used to drive the workpiece platform to translate a distance y along the y-axis. p To adjust the position of the center point P on the y-axis;

[0019] An angle adjustment mechanism is used to drive the workpiece platform to rotate by an angle α around an axis perpendicular to plane A, so as to adjust the angle and posture of line segment P1P2.

[0020] Optionally, the device further includes: a support platform; the workpiece platform is fixed on the support platform;

[0021] The second translation mechanism is mounted on the moving end of the first translation mechanism, and the support platform is mounted on the moving end of the second translation mechanism; or,

[0022] The first translation mechanism is mounted on the moving end of the second translation mechanism, and the support platform is mounted on the moving end of the first translation mechanism.

[0023] Optionally, the angle adjustment mechanism includes: a drive motor and a transmission mechanism; the transmission mechanism connects the drive motor and the support platform, and is used to transmit the rotational motion of the drive motor to the support platform, driving the support platform to rotate around an axis perpendicular to plane A, so as to adjust the rotation angle of the workpiece platform; the transmission mechanism is a gear pair or a worm gear assembly.

[0024] Optionally, the auxiliary positioning structure further includes a third translation mechanism, which is used to drive the limiting element to move along the axial direction of the support roller.

[0025] Optionally, a thrust member is slidably disposed on the abutment surface of the limiting element along the tangential direction. The thrust member is used to limit the displacement perpendicular to the axis of the test workpiece and is locked onto the limiting element by a locking member.

[0026] Optionally, the device further includes a light-emitting component, which is disposed on a support platform;

[0027] The light-emitting component includes a second light emitter and a light receiver; the light beam emitted by the second light emitter extends along the direction of line segment P1P2, and the light receiver is used to receive the light beam emitted by the second light emitter.

[0028] This invention also provides a method for testing the fracture toughness of materials, utilizing the aforementioned material fracture toughness testing device; the method includes:

[0029] Acquire images of two marker points P1 and P2, as well as images of the projection points O1 and O2 of the beam emitted by the first emitter onto plane A;

[0030] Establish a rectangular coordinate system on plane A, with the center point of O1 and O2 as the origin O, the direction of the line connecting O1 and O2 as the x-axis, and the direction passing through point O and perpendicular to the x-axis as the y-axis. Obtain the coordinates of two marked points on plane A: P1(x1, y1) and P2(x2, y2). Calculate the coordinates (x1, y1) of the center point P of line segment P1P2 based on the coordinates of P1 and P2. p ,y p ), and the angle α between line segment P1P2 and line segment O1O2;

[0031] Based on the coordinates (x) of the center point P p ,y p The workpiece platform is controlled to translate so that point P coincides with the origin O. The workpiece platform is then controlled to rotate according to the included angle α so that line segment P1P2 is collinear with line segment O1O2.

[0032] The beneficial effects of the technical solutions provided by the embodiments of the present invention include at least the following:

[0033] This invention provides a material fracture toughness testing device and method. A light beam emitted from a light emitter on a loading roller is projected onto two reference points O1 and O2 on plane A. An industrial vision camera captures an image of this plane (plane A). A rectangular coordinate system is established with the midpoint O of the line segment O1O2 as the origin, the direction of O1O2 as the x-axis, and the direction passing through point O and perpendicular to the x-axis as the y-axis. Two marker points P1 and P2 are set on plane A along the symmetrical direction of the axes of the two support rollers, with the midpoint of line segment P1P2 as P. A central control module drives the first and second translation mechanisms to adjust the forward and backward and left and right displacements of the workpiece platform on plane A in the horizontal plane, so that point P precisely coincides with the origin O. The loading roller is aligned with the center of the two support rollers. Then, the workpiece platform is rotated by the angle adjustment mechanism so that line segments P1P2 and O1O2 are visually completely collinear, thus ensuring that the axis of the loading roller is parallel and symmetrically distributed with the axes of the two support rollers. When the test workpiece is placed on the support roller and its end face is in contact with the contact surface of the limiting element, since the tangent direction of the contact part of the contact surface is perpendicular to the axis of the support roller and the loading roller, the axis of the test workpiece is naturally orthogonal to the axis of the three rollers. This satisfies the geometric constraint conditions required for fracture toughness testing, effectively eliminates the span variation and additional bending moment caused by the position deviation of the sample or loading system, and significantly improves the centering accuracy and reliability of the test results. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a schematic diagram of the structure of a material fracture toughness testing device according to some embodiments of the present invention;

[0036] Figure 2 This is a schematic diagram of the structure of a material fracture toughness testing device according to other embodiments of the present invention;

[0037] Figure 3 This is a partial structural schematic diagram of a material fracture toughness testing device provided in some embodiments of the present invention;

[0038] Figure 4 These are schematic diagrams of the angle adjustment mechanism provided in some embodiments of the present invention;

[0039] Figure 5 These are schematic flowcharts of some embodiments of the image recognition system and control system provided by the present invention;

[0040] Figure 6 This is a diagram illustrating the orthogonal relationship between the test workpiece and the axis of the three rollers, provided by some embodiments of the present invention.

[0041] Figure 7 This is a schematic diagram of the rectangular coordinate system established by the image recognition system of some embodiments provided by the present invention.

[0042] Figure label:

[0043] 1-Support assembly; 11-Workpiece platform; 12-Support roller;

[0044] 2-Loading component; 21-Loading roller; 22-First light emitter;

[0045] 3-Image recognition system; 31-Industrial camera; 32-Image processing unit;

[0046] 4-Control system; 41-Central control module; 42-Drive module; 421-First translation mechanism; 422-Second translation mechanism; 423-Angle adjustment mechanism;

[0047] 5-Support platform;

[0048] 6-Auxiliary positioning structure; 61-Limiting element; 62-Third translation mechanism; 63-Thrust member;

[0049] 7-Light-emitting component; 71-Secondary light emitter; 72-Light receiver;

[0050] 100 - Test workpiece. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0052] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms “first,” “second,” and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms “an,” “a,” or “the,” and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms “comprising,” “including,” or “including,” and similar terms mean that the element or object preceding the word encompasses the element or object listed following the word and its equivalents, without excluding other elements or objects. The terms “connected,” “linked,” or “connected,” and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect.

[0053] It should be noted that the terms "up", "down", "left", "right", "front" and "back" used in this invention are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0054] like Figures 1 to 5 As shown, the material fracture toughness testing device provided in this embodiment of the invention is used to automatically achieve high-precision spatial geometric alignment between the loading system and the specimen during three-point bending fracture toughness testing (e.g., conforming to ASTM E399 or ISO 12135 standards), ensuring that the three core geometric constraints required for the test are met (e.g., ...). Figure 6 As shown): The loading roller 21 is parallel to the axis of the support roller 12, the double support rollers 12 are symmetrically distributed relative to the loading roller 21, and the long axis of the test workpiece 100 is orthogonal to the axis of each roller.

[0055] The device includes: a support component 1, a loading component 2, an image recognition system 3, a control system 4, and an auxiliary positioning structure 6.

[0056] The support assembly 1 includes a workpiece platform 11 and two parallel support rollers 12. The two support rollers 12 are mounted on the upper surface (plane A) of the workpiece platform 11 to support the test workpiece 100. Two marking points P1 and P2 are provided on plane A along the central symmetry line of the axes of the two support rollers 12. Two boss structures 13 with receiving grooves can be provided on the workpiece platform 11. The support rollers 12 are placed in the receiving grooves, and the boss structures 13 can be slidably mounted on the upper surface of the workpiece platform 11 via a screw and nut pair, thereby adjusting the span between the two support rollers 12.

[0057] The loading assembly 2 includes a liftable loading roller 21, which is driven by a lifting mechanism to apply a cyclic load in the vertical direction. At the bottom of the loading roller 21, at both ends along its axial direction (i.e., the projection area facing plane A), a first emitter 22 is installed. The first emitter 22 is preferably a visible light laser diode or an infrared point light source, emitting light vertically downwards. When the loading roller 21 is in the initial test position, the beams emitted by the two first emitters 22 form two clear light spots on plane A, denoted as projection points O1(x1,y1) and O2(x2,y2), respectively. These two light spots represent the spatial projection of the axis of the loading roller 21 onto plane A.

[0058] like Figure 3 , Figure 5 and Figure 7 As shown, the image recognition system 3 includes an industrial camera 31 and an image processing unit 32. The industrial camera 31 is fixed to a bracket above the workpiece platform 11, with its lens facing plane A. It has sufficient resolution and frame rate to clearly capture images of marker points P1 and P2, as well as projection points O1 and O2. The image processing unit 32 is built into the control system 4 and implemented using an embedded processor or industrial computer. Its functions include: First, based on the position information of O1 and O2, taking the midpoint O of the line connecting them as the origin, defining the direction of O1O2 as the x-axis, and the direction passing through point O and perpendicular to the x-axis as the y-axis, establishing a two-dimensional rectangular coordinate system on plane A; Second, identifying the pixel coordinates of P1 and P2 through image edge detection and centroid extraction algorithms, and converting them into actual physical coordinates; Finally, calculating the coordinates (x, y) of the midpoint P of line segment P1P2. p ,y p The angle α between line segments P1P2 and O1O2 is calculated according to formula (1). This angle α reflects the deflection error of the axis of the loading roller 21 relative to the axes of the two support rollers 12.

[0059]

[0060] like Figure 4 and Figure 5 As shown, the control system 4 includes a central control module 41 and a drive module 42. The central control module 41 receives the coordinates (x, y, x) of point P from the image processing unit 32. p ,y p ) and α data, and generate corresponding adjustment instructions.

[0061] The drive module 42 includes: a first translation mechanism 421, a second translation mechanism 422, and an angle adjustment mechanism 423. The first translation mechanism 421 drives the workpiece platform 11 to move a distance x along the x-axis. pTo eliminate the offset of the loading roller 21 in the support span direction; the second translation mechanism 422 drives the workpiece platform 11 to move a distance y along the y-axis direction. p The first translation mechanism 421, the second translation mechanism 422, and the angle adjustment mechanism 423 all operate by rotating the entire workpiece platform 11 around the z-axis perpendicular to plane A by an angle α until line segments P1P2 and O1O2 are completely collinear, thereby ensuring that the axis of the loading roller 21 is parallel and symmetrical to the axes of the two support rollers 12. The first translation mechanism 421, the second translation mechanism 422, and the angle adjustment mechanism 423 all operate by receiving adjustment commands from the central control module 41.

[0062] It should be noted that both the image processing unit 32 and the central control module 41 include a memory, a processor, and a computer program stored in the memory and capable of running on the processor. When the computer program is executed by the processor, it causes the processor to perform the aforementioned image processing functions or adjustment instructions.

[0063] In some embodiments, the device further includes a support platform 5. The workpiece platform 11 is fixed to the support platform 5. The first translation mechanism 421 and the second translation mechanism 422 are servo motor driven lead screw mechanisms or linear motors. The two translation mechanisms can be arranged in an "XY" or "YX" stacked layout, that is: the moving end of the first translation mechanism 421 is connected to the base of the second translation mechanism 422, and the moving end of the second translation mechanism 422 is connected to the support platform 5; or conversely, the moving end of the second translation mechanism 422 is connected to the base of the first translation mechanism 421, and the moving end of the first translation mechanism 421 is connected to the support platform 5. This structure enables the workpiece platform 11 to achieve four degrees of freedom of translation in the horizontal plane: forward, backward, left, and right.

[0064] The angle adjustment mechanism 423 includes a drive motor and a transmission mechanism. The transmission mechanism can be a gear pair or a worm gear assembly, used to transmit the rotational motion of the drive motor to the support platform 5, causing it to rotate around the z-axis. The drive motor can be a stepper motor or a servo motor. The angle adjustment mechanism 423 works in conjunction with the first and second translation mechanisms 421 and 422 to complete the spatial attitude calibration.

[0065] In some embodiments, the auxiliary positioning structure 6 is used to constrain the spatial orientation of the test workpiece 100 during placement. The auxiliary positioning structure 6 is mounted on the support platform 5, near one end of the support roller 12. The auxiliary positioning structure 6 includes a limiting element 61 that abuts against the end of the test workpiece 100. The tangent direction of its abutment surface is perpendicular to the axial direction of the two support rollers 12, so that the axis of the test workpiece 100 is orthogonal to the axes of the two support rollers 12, thereby satisfying the geometric constraint requirements of the fracture toughness test. The abutment surface can be a plane or a cylindrical surface extending in the horizontal direction.

[0066] In some embodiments, such as Figure 1 and Figure 2 As shown, the auxiliary positioning structure 6 also includes a third translation mechanism 62, which is used to drive the limiting element 61 to move along the axis of the support roller 12 to accommodate test workpieces 100 of different sizes.

[0067] In some embodiments, a thrust member 63 is slidably disposed on the abutment surface of the limiting element 61 along the tangential direction. The thrust member 63 is used to limit the displacement of the test workpiece 100 in the axial direction and is locked onto the limiting element 61 by a locking member. Scale lines may be provided on the abutment surface to indicate the movement distance of the thrust member 63. The locking member may adopt a bolt and nut mating structure.

[0068] Furthermore, to ensure the accuracy of the pre-crack location in the fracture toughness test, the pre-cut notch at the bottom of the test workpiece 100 is located directly below the loading roller 21, and its projection on plane A falls on the line P1P2 connecting the centers of the two support rollers 12. In some embodiments, such as Figure 2 As shown, the device also includes a light-emitting component 7; the light-emitting component 7 includes a second light emitter 71 and a light receiver 72, wherein the second light emitter 71 is mounted on the support platform 5 and close to one end of the support roller 12, and its emission direction extends along the line connecting P1 and P2 to form a thin and long planar light band; the light receiver 72 is correspondingly disposed at the other end of the support roller 12 and is arranged opposite to the second light emitter 71 to receive the light beam.

[0069] After the loading roller 21 and the support roller 12 complete spatial orientation calibration to form a three-roller orthogonal relationship, the test workpiece 100 is placed on the support roller 12. If its pre-cut notch is not accurately aligned with the symmetry line of the two support rollers 12 (i.e. not on the line connecting P1 and P2), the test workpiece 100 body will block part or all of the light beam, causing the light receiver 72 to be unable to receive a valid signal. The position of the test workpiece 100 is adjusted along the vertical axis of the support roller 12 by manual or automatic adjustment mechanism until the light receiver 72 detects a complete light signal, indicating that the pre-cut notch is accurately located directly below the loading roller 21, thereby meeting the geometric requirements of the crack location in the fracture toughness test.

[0070] The testing procedure is as follows: First, the test workpiece 100 is placed on the two support rollers 12, with one end pressed against the contact surface of the limiting element 61. The image recognition system 3 is activated to collect the position information of O1, O2, P1, and P2. The control system 4 automatically drives the first and second translation mechanisms 421 and 422 and the angle adjustment mechanism 423 according to the calculation results to align the axes of the loading roller 21 and the support rollers 12. Then, the position of the test workpiece 100 is adjusted until the light receiver 72 detects a complete light signal. Finally, a load is applied to perform a fracture toughness test. The entire alignment process requires no manual intervention, significantly improving the consistency and reliability of the test data.

[0071] This invention also provides a method for testing the fracture toughness of materials, utilizing the aforementioned material fracture toughness testing device; the method includes:

[0072] Acquire images of two marker points P1 and P2, as well as images of the projection points O1 and O2 of the beam emitted by the first emitter onto plane A;

[0073] Establish a rectangular coordinate system on plane A, with the center point of O1 and O2 as the origin O, the direction of the line connecting O1 and O2 as the x-axis, and the direction passing through point O and perpendicular to the x-axis as the y-axis. Obtain the coordinates of two marked points on plane A: P1(x1, y1) and P2(x2, y2). Calculate the coordinates (x, y) of the center point P of line segment P1P2 based on the coordinates of P1 and P2. p ,y p ), and the angle α between line segment P1P2 and line segment O1O2;

[0074] Based on the coordinates (x) of the center point P p ,y p The workpiece platform is controlled to translate so that point P coincides with the origin O. The workpiece platform is then controlled to rotate according to the included angle α so that line segment P1P2 is collinear with line segment O1O2.

[0075] This invention provides a material fracture toughness testing device and method. A light beam emitted from a light emitter on a loading roller 21 is projected onto two reference points O1 and O2 on plane A. An industrial vision camera captures an image of this plane (plane A). A rectangular coordinate system is established with the midpoint O of the line segment O1O2 as the origin, the direction of O1O2 as the x-axis, and the direction passing through point O and perpendicular to the x-axis as the y-axis. Two marker points P1 and P2 are provided on plane A along the symmetrical direction of the axes of the two support rollers 12, with the midpoint of line segment P1P2 as P. The central control module 41 drives the first and second translation mechanisms 412 and 422 to adjust the forward and backward and left and right displacements of the workpiece platform 11 on plane A in the horizontal plane, ensuring that point P precisely coincides with the origin O, thus achieving the loading roller... The loading roller 21 is aligned with the center of the double support roller 12. Subsequently, the workpiece platform 11 is rotated by the angle adjustment mechanism 423 so that line segments P1P2 and O1O2 are visually completely collinear, thereby ensuring that the axis of the loading roller 21 is parallel and symmetrically distributed with the axes of the two support rollers 12. When the test workpiece 100 is placed on the support roller 12 and its end face is in contact with the contact surface of the limiting element 61, since the tangent direction of the contact part of the contact surface is perpendicular to the axis direction of the support roller 12 and the loading roller 21, the axis of the test workpiece 100 naturally remains orthogonal to the axis of the three rollers. This satisfies the geometric constraint conditions required for fracture toughness testing, effectively eliminates the span variation and additional bending moment caused by the position deviation of the sample or loading system, and significantly improves the centering accuracy and reliability of the test results.

[0076] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A material fracture toughness testing device, characterized in that, include: The support assembly includes: a workpiece platform and two support rollers; the two support rollers are arranged in parallel on plane A of the workpiece platform, and the support rollers are used to support the test workpiece; two marking points P1 and P2 are provided on plane A along the symmetry line of the axes of the two support rollers. The loading component includes: a liftable loading roller; the loading roller is horizontally arranged above the workpiece platform, and a first light emitter is respectively provided at two points along the axial direction at the bottom of the loading roller; The image recognition system acquires images of two marker points P1 and P2, as well as images of the projection points O1 and O2 of the beam emitted by the first emitter onto plane A. A rectangular coordinate system is established on plane A, with the center point of O1 and O2 as the origin O, the direction of the line connecting O1 and O2 as the x-axis, and the direction passing through point O and perpendicular to the x-axis as the y-axis. The system acquires the coordinates of the two marker points P1(x1, y1) and P2(x2, y2) on plane A. Based on the coordinates of P1 and P2, the system calculates the coordinates (x1, y1) of the center point P of line segment P1P2. p ,y p ), and the angle α between line segment P1P2 and line segment O1O2; The control system, connected to the image recognition system and workpiece platform, is used to determine the coordinates (x, y) of the center point P. p ,y p The workpiece platform is controlled to translate so that point P coincides with the origin O. The workpiece platform is then controlled to rotate according to the included angle α so that line segment P1P2 is collinear with line segment O1O2, thereby making the axes of the two support rollers and the loading roller parallel to each other. The auxiliary positioning structure includes a limiting element that abuts against the end of the test workpiece. The tangent direction of the abutment surface is perpendicular to the axis direction of the two support rollers, so that the axis of the test workpiece is orthogonal to the axes of the two support rollers and the loading roller.

2. The material fracture toughness testing device according to claim 1, characterized in that, The angle α between line segments P1P2 and O1O2 can be obtained using the following formula (1):

3. The material fracture toughness testing device according to claim 1, characterized in that, The image recognition system includes: An industrial camera is fixed above the workpiece platform, facing plane A, and is used to acquire images of marker points P1 and P2 and projection points O1 and O2. The image processing unit is used to establish a rectangular coordinate system on plane A based on the images of P1, P2, O1, and O2, with the center point of O1 and O2 as the origin O, the direction of the line connecting O1 and O2 as the x-axis, and the direction passing through point O and perpendicular to the x-axis as the y-axis, and to obtain the coordinates of P1 and P2 in the rectangular coordinate system; and to calculate the coordinates (x1, y1) of the center point P of line segment P1P2 based on the coordinates (x2, y2) of P1 and (x1, y1) of P2. p ,y p ), and the angle α between line segment P1P2 and line segment O1O2.

4. The material fracture toughness testing device according to claim 1, characterized in that, The control system includes a central control module and a drive module; the central control module is used to determine the coordinates (x, y) of the center point P. p ,y p The angle α controls the movement of the drive module; The driving module includes: The first translation mechanism is used to drive the workpiece platform to translate a distance x along the x-axis. p To adjust the position of the center point P on the x-axis; The second translation mechanism is used to drive the workpiece platform to translate a distance y along the y-axis. p To adjust the position of the center point P on the y-axis; An angle adjustment mechanism is used to drive the workpiece platform to rotate by an angle α around an axis perpendicular to plane A, so as to adjust the angle and posture of line segment P1P2.

5. The material fracture toughness testing device according to claim 4, characterized in that, Also includes: Support platform; The workpiece platform is fixed on the support platform; The second translation mechanism is mounted on the moving end of the first translation mechanism, and the support platform is mounted on the moving end of the second translation mechanism; or, The first translation mechanism is mounted on the moving end of the second translation mechanism, and the support platform is mounted on the moving end of the first translation mechanism.

6. The material fracture toughness testing device according to claim 5, characterized in that, The angle adjustment mechanism includes a drive motor and a transmission mechanism; the transmission mechanism connects the drive motor and the support platform, and is used to transmit the rotational motion of the drive motor to the support platform, driving the support platform to rotate around an axis perpendicular to plane A, so as to adjust the rotation angle of the workpiece platform; the transmission mechanism is a gear pair or a worm gear assembly.

7. The material fracture toughness testing device according to claim 1, characterized in that, The auxiliary positioning structure also includes a third translation mechanism, which is used to drive the limiting element to move along the axial direction of the support roller.

8. The material fracture toughness testing device according to claim 1, characterized in that, A thrust member is slidably disposed on the contact surface of the limiting element along the tangential direction. The thrust member is used to limit the displacement perpendicular to the axis of the test workpiece and is locked onto the limiting element by a locking member.

9. The material fracture toughness testing device according to claim 5, characterized in that, Also includes: A light-emitting component, which is mounted on a support platform; The light-emitting component includes: a second light emitter and a light receiver; The light beam emitted by the second emitter extends along the direction of line segment P1P2, and the light receiver is used to receive the light beam emitted by the second emitter.

10. A method for testing the fracture toughness of a material, characterized in that, The method utilizes the material fracture toughness testing apparatus according to claims 1-9; the method includes: Acquire images of two marker points P1 and P2, as well as images of the projection points O1 and O2 of the beam emitted by the first emitter onto plane A; Establish a rectangular coordinate system on plane A, with the center point of O1 and O2 as the origin O, the direction of the line connecting O1 and O2 as the x-axis, and the direction passing through point O and perpendicular to the x-axis as the y-axis. Obtain the coordinates of two marked points on plane A: P1(x1, y1) and P2(x2, y2). Calculate the coordinates (x1, y1) of the center point P of line segment P1P2 based on the coordinates of P1 and P2. p ,y p ), and the angle α between line segment P1P2 and line segment O1O2; Based on the coordinates (x) of the center point P p ,y p The workpiece platform is controlled to translate so that point P coincides with the origin O. The workpiece platform is then controlled to rotate according to the included angle α so that line segment P1P2 is collinear with line segment O1O2.

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