Method for monitoring crack propagation of plastic specimen and monitoring device

Abstract

The present invention belongs to the field of plastic pipeline monitoring, and discloses a method and a monitoring device for monitoring the crack propagation of a plastic specimen. The method for monitoring the crack propagation of a plastic specimen includes the following steps: multiple monitoring angles are set, and the ligament radius data at each angle is recorded once; the monitored data is compared to obtain whether the ligament radius sizes at each angle are the same; if they are the same, the above two steps are repeated; if they are different, the angle where the minimum ligament radius is located is found; facing the angle where the minimum ligament radius is located, the change of the ligament radius at this angle is continuously recorded. The crack propagation situation can be directly recorded.

Description

Technical Field

[0001] The present invention belongs to the field of plastic pipeline monitoring, and particularly relates to a method and a device for monitoring crack propagation of a polyethylene pipe sample. Background Art

[0002] The service life of polyethylene pipes is related to factors such as materials, environment, and loads, where materials include resins, additives, manufacturing processes, etc.; the environment includes gases, liquids, ultraviolet radiation, radioactive radiation, temperature, termites, microorganisms, etc.; loads include internal pressure, external static / dynamic loads, notches, scratches, etc. In existing test methods for fatigue crack propagation, such as using a contact extensometer method to indirectly measure the crack propagation rate by measuring the opening displacement, or using the average rate of crack propagation. The former has a relatively high cost and a small amount of data collected, and the latter has low accuracy, and neither can directly and real-time monitor the fatigue crack propagation at low cost. Summary of the Invention

[0003] The purpose of the present invention is to improve the disadvantages of the existing technology and provide a method and a device for monitoring crack propagation of a plastic sample, which can directly record the crack propagation situation.

[0004] Achieving the above purpose includes the following technical solutions.

[0005] A method for monitoring crack propagation of a plastic sample includes the following steps:

[0006] There are multiple monitoring angles, and for each angle, the ligament radius data and / or crack propagation length at this angle are recorded once;

[0007] Compare the data monitored at each angle;

[0008] Determine whether the ligament radius and / or crack propagation length sizes at each angle are the same;

[0009] If they are the same, repeat the above two steps;

[0010] If they are different, find the minimum value of the ligament radius, and record the value and time change of the ligament radius at the angle corresponding to the minimum value of the ligament radius; or find the maximum value of the crack propagation length, and record the value and time change of the crack propagation at the angle corresponding to the maximum value of the crack propagation.

[0011] In some embodiments, where the sample radius is R0, the ligament radius is R n , and the crack propagation length is a n ; it satisfies R0 = R n + a n + X, where X is a constant;

[0012] After the crack propagates, it is recorded as T+1 monitoring. At this time, at least two crack propagation lengths with different angles and sizes are recorded, which are respectively recorded as a A and a B ;

[0013] Rotate the monitoring angle and perform T+2 monitoring. At this time, record at least two different angles, and at least one angle is different from the T+1 monitoring angle, and one angle is the same as the T+1 monitoring angle. Record the crack extension length of T+2 monitoring, which is recorded as a B and a C ;

[0014] Among them, A, B, and C represent angles;

[0015] If the measured crack extension length satisfies, a A B And a B >a C When the angle is B, the crack extension value and time change at angle B are continuously recorded.

[0016] In some embodiments, the specimen radius R0 and the ligament radius R n , crack extension length a n ; satisfy R0=R n +a n +X, X is a constant;

[0017] When the ligament radius is different, it is recorded as T+1 monitoring. At this time, at least two different angles and ligament radii of different sizes are recorded, which are respectively recorded as R A and R B ;

[0018] Rotate the monitoring angle and perform T+2 monitoring. At this time, record at least two different angles, and at least one angle is different from the T+1 monitoring angle, and one angle is the same as the T+1 monitoring angle. Record the ligament radius of T+2 monitoring, which is recorded as R B and R C ;

[0019] Among them, A, B, and C represent angles;

[0020] If the measured ligament radius satisfies, R A >R B And R B <R C When the angle is adjusted, face the B angle and continuously record the changes in the ligament radius under the B angle.

[0021] In some embodiments, when performing T+1 monitoring and thereafter, each forward or reverse rotation angle is rotated according to a set angle value; ​

[0022] The initially set monitoring angles are 0°, 60°, and 120°;

[0023] When the measured angle is 60°, the ligament radius is the smallest;

[0024] Rotate forward by 10°. During monitoring, record at least the ligament radii at the angles of 60° and 70°, denoted as R 60° and R 70° ;

[0025] If R 60° >R 70° ;

[0026] Continue to rotate forward by 10°. During monitoring, record at least the ligament radii at the angles of 70° and 80°, denoted as R 70° and R 80° ;

[0027] If R 70° <R 80° ;

[0028] Aim at the 70° angle and continuously record the change in the ligament radius at the 70° angle.

[0029] In some embodiments, when performing the (T + 1)-th monitoring and thereafter, each forward or backward rotation angle is rotated according to the set angle value;

[0030] The initially set monitoring angles are 0°, 60°, and 120°;

[0031] When the measured angle is 60°, the ligament radius is the smallest;

[0032] Rotate forward by 10°. During monitoring, record at least the ligament radii at the angles of 60° and 70°, denoted as R 60° and R 70° ;

[0033] If R 60° <R 70° ;

[0034] Rotate backward by 10°. During monitoring, record at least the ligament radii at the angles of 50° and 60°, denoted as R 50° and R 60° ;

[0035] If R 60° <R 50° ;

[0036] Aim at the 60° angle and continuously record the change in the ligament radius at the 60° angle.

[0037] In some embodiments, after there are ligament radius sizes different, it is recorded as the (T + 1)-th monitoring. At this time, at least two different angles are recorded, and the ligament radii of different sizes are denoted as R A and R B ;

[0038] Rotate the monitoring angle to conduct the (T + 2)-th monitoring. At this time, at least two different angles are recorded, and at least one angle is different from the angle of the (T + 1)-th monitoring, and one angle is the same as the angle of the (T + 1)-th monitoring. Record the ligament radius of the (T + 2)-th monitoring, denoted as R B and R C ;

[0039] where A, B, and C represent angles;

[0040] If the measured ligament radii satisfy R A = R B ;

[0041] Face the angle of (A + B) / 2 and continuously record the numerical value and time change of the ligament radius at the angle of (A + B) / 2;

[0042] If the measured ligament radii satisfy R B = R C ;

[0043] Face the angle of (B + C) / 2 and continuously record the numerical value and time change of the ligament radius at the angle of (B + C) / 2.

[0044] In some embodiments, the initially set monitoring angles are 0°, 60°, and 120°;

[0045] If the measured angle is 60° and the ligament radius is the smallest;

[0046] Rotate 10° in the positive direction. During monitoring, at least record the ligament radii at the angles of 60° and 70°, denoted as R 60° and R 70° , compare the sizes of R 60° and R 70° , and there are at least three cases;

[0047] If R 60° = R 70° ;

[0048] Face the angle of 65° and continuously record the change of the ligament radius at the angle of 65°;

[0049] If R 60° < R 70° ;

[0050] Rotate 10° in the reverse direction. During monitoring, at least record the ligament radii at the angles of 50° and 60°, denoted as R50° and R 60° ;

[0051] and R 60° = R 50° ;

[0052] Aim at the 55° angle and continuously record the change of the ligament radius at the 55° angle;

[0053] If R 60° > R 70° ;

[0054] Rotate forward by 10°. During monitoring, at least record the ligament radii at the 70° and 80° angles, denoted as R 70° and R 80° ;

[0055] and R 70° = R 80° ;

[0056] Aim at the 75° angle and continuously record the change of the ligament radius at the 75° angle.

[0057] In some embodiments, there are two sets of specimen data on both sides at each angle, and record the side with the maximum crack propagation length;

[0058] All subsequent records only record the side with the maximum crack propagation length.

[0059] In some embodiments, crack monitoring is surface light source monitoring.

[0060] The specimen crack monitoring device includes a monitoring host, a crack monitor and a rotating assembly. The rotating assembly is installed on the monitoring host, and the crack monitor is installed on the rotating assembly. The crack monitor uses surface light source laser monitoring.

[0061] The technical solution provided by the present invention has the following advantages and effects:

[0062] Compared with the traditional crack monitoring device, this solution directly monitors the crack propagation position, and can scan and monitor the crack at multiple angles, then compare to find the place where the crack propagates fastest, stop the crack monitoring device at the position where the crack propagation can be monitored fastest, continuously record the crack propagation situation, and most intuitively view the crack propagation situation. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 is a schematic flow chart of the monitoring in the embodiment of the present invention;

[0064] Figure 2 is a schematic cross-sectional structure diagram of the specimen in the embodiment of the present invention;

[0065] Figure 3 It is a schematic diagram of the front view of the specimen in the embodiment of the present invention;

[0066] Figure 4 It is a schematic structural diagram of the monitoring angles of 0°, 60°, and 120° in the embodiment of the present invention;

[0067] Figure 5 It is a schematic diagram of the monitoring after the monitoring angle rotates forward by 10° again in the embodiment of the present invention;

[0068] Figure 6 It is in the embodiment of the present invention [[ID=~]] Figure 4 On the basis, it is a schematic diagram of the monitoring after the monitoring angle rotates backward by 10° again;

[0069] Figure 7 It is a schematic structural diagram of the monitoring angles of 0°, 30°, 60°, 90°, 120°, and 150° in the embodiment of the present invention;

[0070] Figure 8 It is a schematic diagram of the structure of the monitoring device before monitoring in the embodiment of the present invention;

[0071] Figure 9 It is a schematic diagram of the structure of the monitoring device during monitoring in the embodiment of the present invention.

[0072] Explanation of reference numerals:

[0073] 10. Monitoring host; 20. Crack monitor; 30. Rotating assembly. Detailed implementation manners

[0074] For the convenience of understanding the present invention, the specific embodiments of the present invention will be described in more detail below with reference to the accompanying drawings of the specification.

[0075] Unless otherwise specified or defined, the "first, second..." used herein is only for distinguishing names and does not represent a specific quantity or order.

[0076] Unless otherwise specified or defined, the term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0077] It should be noted that when an element is considered to be "fixed to" another element, it can be directly fixed to the other element or there can be an intermediate element.

[0078] Such as Figure 8 And Figure 9As shown, the specimen crack monitoring device includes a monitoring host 10, a crack monitor 20, and a rotating assembly 30. The rotating assembly 30 is installed on the monitoring host 10, and the crack monitor 20 is installed on the rotating assembly 30. The crack monitor 20 uses a surface light source for monitoring. During monitoring, the specimen is prepared and clamped on the monitoring host 10. The monitoring host 10 performs repeated tensile actions on the specimen. At this time, the crack monitor 20 is a surface light source laser monitor, so the outer cracks of the specimen can be monitored. At this time, under the action of the rotating assembly 30, the crack monitor 20 rotates according to the set time and speed. When the crack monitor 20 reaches the set monitoring angle, the crack condition at the set angle is recorded. After finding the angle at which the specimen crack propagates the fastest, the rotating assembly 30 transports the crack monitor 20 to this position and records the continuous propagation of the crack.

[0079] The surface light source of the monitor 20 can be visible light or invisible light. Here, laser monitoring is used, and the wavelength of the laser can be selected according to the usage requirements.

[0080] Compared with traditional crack monitoring, this solution directly monitors the propagation position of the crack, and can scan and monitor the crack from multiple angles. Then, by comparison, the place where the specimen crack propagates the fastest is found. The crack monitor 20 is stopped at the position where the crack can be monitored to propagate the fastest, and the propagation of the crack is continuously recorded, so as to most intuitively view the propagation of the crack.

[0081] The data is described as follows. As Figure 2 and Figure 3 shown, the radius of the specimen is R0, the radius of the ligament is R n , and the crack depth is a; among them, the total crack depth a includes the prefabricated crack depth a0 and the depth a of the subsequent crack propagation n , and a = a0 + a n , and it satisfies R0 = R n + a. Here, R0 = R n + a n + X, that is, R0 = R n + a n + a0.

[0082] Figure 2 The dotted line indicates the position where the crack propagates to.

[0083] As Figure 1 shown, the method for monitoring the crack propagation of a plastic specimen includes the following steps:

[0084] Set multiple monitoring angles, and record the data of the ligament radius and / or crack propagation length at each angle once;

[0085] Compare the data monitored at each angle to determine whether the ligament radius and / or the crack propagation length are the same at each angle;

[0086] If they are the same, repeat the above two steps;

[0087] If they are different, continuously record the change in ligament radius or crack propagation at the angle of the minimum ligament radius or the maximum crack propagation length; specifically, find the minimum ligament radius, and record the value and time change of the ligament radius at the angle corresponding to the minimum ligament radius; or find the maximum crack propagation length, and record the value and time change of the crack propagation at the angle corresponding to the maximum crack propagation length. During monitoring, the ligament radius and the crack propagation length can be monitored simultaneously and the data can be recorded, or the ligament radius or the crack propagation length can be monitored separately, and according to the relationship of R0 = R n +a, whether it is the ligament radius monitoring or the crack propagation length monitoring, it can be converted;

[0088] Taking the monitoring of the crack propagation length as an example,

[0089] After crack propagation occurs, it is recorded as the (T + 1)-th monitoring. At this time, at least two different angles and different crack propagation lengths are recorded, which are respectively recorded as a A and a B ;

[0090] Rotate the monitoring angle to conduct the (T + 2)-th monitoring. At this time, at least two different angles are recorded, and at least one angle is different from the angle of the (T + 1)-th monitoring, and one angle is the same as the angle of the (T + 1)-th monitoring. Record the crack propagation length of the (T + 2)-th monitoring, which is recorded as a B and a C ;

[0091] where A, B, and C represent angles;

[0092] If the measured crack propagation length satisfies a A < a B and a B > a C at this time, facing the B angle, continuously record the value and time change of the crack propagation length at the B angle.

[0093] Specifically, in this embodiment, taking the monitoring of the ligament radius as an example.

[0094] After the ligament radius is different, it is recorded as the (T + 1)-th monitoring. At this time, at least two different angles and different ligament radii are recorded, which are recorded as R A and R B ;

[0095] Rotate the monitoring angle and conduct T+2 times of monitoring. At this time, at least two different angles should be recorded, and at least one angle is different from the angle of the T+1 time of monitoring, and one angle is the same as the angle of the T+1 time of monitoring. Record the ligament radius of the T+2 times of monitoring, denoted as R B and R C ;

[0096] A, B, and C represent angles; here, T+1 and T+2 do not necessarily mean the next time after crack propagation occurs, but represent all adjacent two-side monitorings after crack propagation occurs. For example, the first and second monitorings or the fourth and fifth monitorings after crack propagation occurs can both be represented as the T+1 and T+2 times of monitoring.

[0097] If the measured ligament radius satisfies, R A >R B and R B <R C When this is the case, facing the B angle, continuously record the change in the ligament radius at the B angle.

[0098] If the measured ligament radius satisfies, R A =R B When this is the case, facing the (A+B) / 2 angle, continuously record the change in the ligament radius at the (A+B) / 2 angle;

[0099] If the measured ligament radius satisfies, R B =R C When this is the case, facing the (B+C) / 2 angle, continuously record the change in the ligament radius at the (B+C) / 2 angle.

[0100] When conducting the T+1 time of monitoring and afterwards, rotate the angle forward or backward by the set angle value each time.

[0101] The above is a brief overview of the monitoring method. The following is an explanation of the specific method.

[0102] It is divided into two implementation schemes. One is to fix the angle, such as fixing the monitoring angles as 0°, 60°, 120° (M = 3) or 0°, 30°, 60°, 90°, 120°, 150° (M = 6); the other is not to fix the angle, but to find the minimum value of the ligament radius or the maximum value of the crack propagation length. Here, M represents the number of measured angles, and the rotation angle is (180 / M)°. In this embodiment, the rotation time is 3 - 5 seconds, preferably 4 seconds; the photo data acquisition time is 1 - 3 seconds, preferably 2 seconds.

[0103] In the embodiment of fixing the angle, according to the M value, record the values of the ligament radius or the crack propagation length, and find the minimum value of the ligament radius or the maximum value of the crack propagation length.

[0104] In the embodiment with variable angles, the angle is fixed when there is no propagation of the initial crack. When crack propagation occurs subsequently and the angle at which the crack propagates fastest needs to be determined, the angle is measured as variable until the direction in which the crack propagates fastest is found, and then monitoring is carried out at this angle.

[0105] The initially set monitoring angles are 0°, 60°, and 120°. Since there are two crack propagation lengths at the same angle, that is, crack propagation may occur on both the left and right sides. For example, when the laser receiver or industrial camera receiver is at an angle of 60°, there are crack propagation lengths a 60 120° and a 60 0° , which respectively represent the crack propagation lengths on the side deviated by 120° and the side deviated by 0° at an angle of 60°. Or rather, since there are two ligament radii at the same angle, that is, crack propagation may occur on both the left and right sides. For example, when the laser receiver or industrial camera receiver is at an angle of 60°, there is a ligament radius length R 60 120° and R 60 0° , which respectively represent the ligament radius lengths on the side deviated by 120° and the side deviated by 0° at an angle of 60°. The smallest ligament radius at the same angle is recorded, and only the smallest side's ligament radius is recorded for subsequent records. Here, since the monitoring device monitors front and back, only a 180° range needs to be covered. For example, the monitoring angles of 0° and 180° are the same.

[0106] As Figure 4 shown, monitoring starts. Here, taking the case where the ligament radius changes for the first time and the ligament radius is the smallest when measured at an angle of 60° as an example.

[0107] The time for each monitoring is as follows in the table:

[0108]

[0109] After each monitoring, compare whether the ligament radius has changed, that is, whether the crack has propagated. If there is no propagation, continue with the next monitoring until the ligament radius changes during the Kth monitoring. When it is recorded that the angle is 60°, record the ligament radii on the 0° and 120° sides, denoted as R 60° 0° and R 60° 120° .

[0110] During the (K + 1)th monitoring, as Figure 5 shown, R 60° 0° >R 60° 120°, that is, at 60°, the ligament radius on the 0° side is larger than the ligament radius on the 120° side, and the crack extension length on the 0° side is smaller than the crack extension length on the 120° side. Rotate 10° in the positive direction (rotate 10° towards 120°), and then record at least the ligament radius at 60° and 70°, recorded as R 60° 120° , R 70° 120° , R 60° 0° and R 70° 0° At this time, the positive direction refers to the rotation from 0° to 120°. Figure 5 The middle dotted line indicates the overall monitoring direction after rotation. Since only the minimum ligament radius needs to be recorded at the same angle, assuming R 60° 120° <R 60° 0° , R 70° 120° <R 70° 0° .

[0111] Compared with the K+1 monitoring, R 60° 120° and R 70° 120° The following situations exist:

[0112] If R 60° 120° >R 70° 120° : Continue to rotate forward 10° and perform K+2 monitoring. During monitoring, record the ligament radius at 70° and 80°, which is recorded as R 70° 120° , R 80° 120° , R 70° 0° and R 80° 0° . Record and compare the minimum values of the four ligament radii. If R 70° 120° <R 80° 120° , here it is shown that the ligament radius on the 120° side is the smallest at an angle of 70°. Facing the 70° angle, the changes in the ligament radius at the 70° angle are continuously recorded.

[0113] If R 60° 120° <R 70° 120° :like Figure 6As shown, rotate counterclockwise by 10° and conduct K + 2 times of monitoring. During the monitoring, record at least the ligament radii at the angles of 50° and 60°, denoted as R 50° 120° , R 60° 120° , R 50° 0° and R 60° 0° . Record and compare the minimum values of the 4 ligament radii. If R 50° 120° > R 60° 120° , it indicates that the ligament radius on the 120° side of the 60° angle is the smallest. Facing the 60° angle, continuously record the change of the ligament radius at the 60° angle.

[0114] If R 60° 120° = R 70° 120° : The minimum ligament radius is between the monitoring angles of 60° and 70°. Take the median value of 65°. Facing the 65° angle, continuously record the change of the ligament radius at the 65° angle.

[0115] If the minimum ligament radius is not found, continue to repeat the steps of K + 1 and K + 2 until the minimum ligament radius and its corresponding angle are found.

[0116] Here, during the K + 1 and K + 2 times of monitoring, the rotated angles can be continuously monitored, that is, Figure 5 the angles indicated by the dotted line in Figure 6 and the dotted line, double-dotted line in

[0117] . During the K + 1 and K + 2 times of monitoring, the rotation time is 4 seconds, and the photographing data acquisition time is 2 seconds. Figure 7 shown, set M = 6, and the monitoring angles are set to 0°, 30°, 60°, 90°, 120°, 150°;

[0118] The rotation time is 4 seconds, and the photographing data acquisition time is 2 seconds. The time for each monitoring is as follows in the table:

[0119]

[0120]

[0121] Of course, in other embodiments, M can be set to other values, which will not be elaborated here one by one.

[0122] When referring to the drawings, it is to explain the newly emerged features; in order to avoid the description being not concise enough due to repeated reference to the drawings, for the features that have been described clearly, the drawings will not be cited one by one.

[0123] The above embodiments are not an exhaustive list of the present invention. In addition, there may be multiple other embodiments not listed. Any substitution and improvement made on the basis of not violating the concept of the present invention fall within the protection scope of the present invention.

Claims

1. A method for monitoring the crack propagation of plastic specimens, characterized in that, It includes the following steps: There are multiple monitoring angles, and for each angle, the ligament radius and / or crack propagation length data at this angle are recorded once. Compare the data monitored at each angle. Determine whether the ligament radius and / or crack propagation length sizes at each angle are the same. If they are the same, repeat the above two steps. If they are different, find the minimum ligament radius, and record the value of the ligament radius and its change over time at the angle where the minimum ligament radius is located. Among them, the specimen radius is R0, and the ligament radius is R n , the crack propagation length is a n ; satisfying R0 = R n +a n +X, where X is a constant; during the (T + 1)-th monitoring and afterwards, each time the angle of forward or reverse rotation is rotated according to the set angle value; After the ligament radius sizes are different, it is recorded as the (T + 1)-th monitoring. At this time, at least two different angles are recorded, and the ligament radii of different sizes are respectively recorded as R A and R B ; Rotate the monitoring angle and perform the monitoring for T+2 times. At this time, at least two different angles should be recorded, and at least one angle is different from the angle in the (T+1)-th monitoring, and one angle is the same as the angle in the (T+1)-th monitoring. Record the ligament radius in the (T+2)-th monitoring, denoted as R B and R C ; Where A, B, and C represent angles. If the measured ligament radius satisfies, R A >R B and R B <R C At this time, for the B angle, continuously record the change in the ligament radius at the B angle; If the measured ligament radius satisfies, R A = R B at that time, facing the angle of (A + B) / 2, continuously record the numerical value and time change of the ligament radius at the angle of (A + B) / 2; if the measured ligament radius satisfies, R B = R C at that time, facing the angle of (B + C) / 2, continuously record the numerical value and time change of the ligament radius at the angle of (B + C) / 2; Or find the maximum crack propagation length, and record the value of the crack propagation and its change over time at the angle where the maximum crack propagation is located. Among them, the specimen radius is R0, and the ligament radius is R n , and the crack propagation length is a n ; satisfying R0 = R n +a n +X, where X is a constant; After crack propagation occurs, it is recorded as the (T + 1)-th monitoring. At this time, at least two different angles and the crack propagation lengths of different sizes are recorded, which are denoted as a A and a B ; Rotate the monitoring angle and conduct T+2 times of monitoring. At this time, at least two different angles should be recorded, and at least one angle is different from the monitoring angle at T+1 time, and one angle is the same as the monitoring angle at T+1 time. Record the crack propagation length of the T+2 times of monitoring, denoted as a B and a C ; Where A, B, and C represent angles. If the measured crack propagation length satisfies, a A <a B and a B >a C At this time, facing the B angle, continuously record the crack propagation length value and time change under the B angle.

2. The plastic specimen crack propagation monitoring method according to claim 1, wherein It includes the following steps: The initially set monitoring angles are 0°, 60°, and 120°. If the measured angle is 60° and the ligament radius is the smallest. Rotate forward by 10°. During monitoring, record at least the ligament radii at angles of 60° and 70°, denoted as R 60° and R 70° ; If R 60° > R 70° ; Continue to rotate forward by 10°. During monitoring, record at least the ligament radii at angles of 70° and 80°, denoted as R 70° and R 80° ; If R 70° <R 80° ; Face the 70° angle and continuously record the change in the ligament radius at the 70° angle.

3. The method for monitoring the crack propagation of a plastic specimen according to claim 1, wherein, It includes the following steps: The initially set monitoring angles are 0°, 60°, and 120°. If the measured angle is 60° and the ligament radius is the smallest. Rotate forward by 10°. During monitoring, record at least the ligament radii at the angles of 60° and 70°, denoted as R 60° and R 70° ; If R 60° <R 70° ; Rotate backward by 10°. During monitoring, record at least the ligament radii at angles of 50° and 60°, denoted as R 50° and R 60° ; If R 60° <R 50° ; Face the 60° angle and continuously record the change in the ligament radius at the 60° angle.

4. The plastic specimen crack propagation monitoring method according to claim 1, characterized in that, It includes the following steps: The initially set monitoring angles are 0°, 60°, and 120°. If the measured angle is 60° and the ligament radius is the smallest. Rotate forward by 10°. During monitoring, record at least the ligament radii at angles of 60° and 70°, denoted as R 60° and R 70° , compare R 60° and R 70° in terms of magnitude. There are at least three cases; If R 60° = R 70° ; Face the 65° angle and continuously record the change in the ligament radius at the 65° angle; If R 60° <R 70° ; Rotate 10° in the reverse direction. During monitoring, record at least the ligament radii at angles of 50° and 60°, denoted as R 50° and R 60° ; and R 60° = R 50° ; Face the 55° angle and continuously record the change in the ligament radius at the 55° angle; If R 60° > R 70° ; Rotate forward by 10°. During monitoring, record at least the ligament radii at angles of 70° and 80°, denoted as R 70° and R 80° ; and R 70° = R 80° ; Face the 75° angle and continuously record the change in the ligament radius at the 75° angle.

5. The method for monitoring the crack propagation of a plastic specimen according to any one of claims 1 to 4, characterized in that, It includes the following steps: For each angle, there are two sets of specimen data on both sides. Record the side with the maximum crack propagation length. All subsequent records only record the side with the maximum crack propagation length.

6. The plastic specimen crack propagation monitoring method according to any one of claims 1 to 4, characterized in that, It includes the following steps: The crack monitoring is surface light source monitoring.

7. Specimen crack monitoring device, adopting the plastic specimen crack propagation monitoring method according to any one of claims 1 to 6, characterized in that, It includes a monitoring host, a crack monitor, and a rotating component. The rotating component is installed on the monitoring host, and the crack monitor is installed on the rotating component. The crack monitor uses surface light source laser monitoring.

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