Method and device for improving mechanical fatigue performance of submarine cable flexible joint

Abstract

The invention provides a method and device for improving the mechanical fatigue performance of a submarine cable flexible joint, and relates to the technical field of ocean engineering. The method comprises the following steps: firstly, measuring the surface roughness and the residual stress of the soft joint before treatment to obtain a first measurement value, obtaining the geometric profile precision of the soft joint before treatment, determining the residual stress design value and the surface roughness design value of the soft joint according to a fatigue life target, and determining the geometric profile precision of the soft joint according to the first measurement value and the design value; required laser peening parameters are determined in a second database, and laser peening treatment is carried out on the surface of the flexible joint according to the parameters until the geometric profile precision, the surface roughness and the residual stress of the flexible joint all meet the design requirements; the device comprises a computer control system, a laser power supply, laser shot blasting equipment, a transmitting mirror group, a part clamping robot and a water coating robot, according to the method and the device provided by the invention, the tensile property, the fatigue resistance and the electrochemical corrosion resistance of the flexible joint can be improved.

Description

Technical Field

[0001] The invention belongs to the field of marine engineering, and in particular relates to a method and a device for improving the mechanical fatigue performance of a submarine cable flexible joint. Background Art

[0002] As the country's demand for resource exploration continues to increase, the scale of development and utilization of marine and island resources is also increasing. The application of submarine cables is developing rapidly, and the demand is increasing. The requirements and demands for high-voltage and long-distance submarine cables are also getting higher and higher. The key to solving long-distance cables is the flexible joint of the cable. In addition to the cross-linking extrusion vulcanization and degassing processes that need to be considered in the manufacturing process of the flexible joint, the welding process is required to connect the cable conductors. Due to the traditional welding process, tensile stress is generated at the conductor weld. Due to the presence of tensile stress, the tensile properties and fatigue properties of the flexible joint weld are low. Under the action of various ocean current loads on the seabed, such as tension, compression, and torsion, the submarine cable is easily damaged at the flexible joint. As we all know, replacing and repairing the flexible joint in such a complex and harsh environment on the seabed is a pain point and difficulty, which increases the maintenance and maintenance costs of submarine cables.

[0003] Therefore, a method and a device are needed to improve the tensile properties, fatigue resistance and electrochemical corrosion resistance of submarine cable flexible joints. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a method and a device for improving the mechanical fatigue performance of a submarine cable flexible joint. According to the fatigue life target of the flexible joint, the surface of the flexible joint is laser shot peened to increase the service time and life of the submarine cable flexible joint on the seabed.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A method for improving the mechanical fatigue performance of a submarine cable flexible joint comprises the following steps:

[0007] A method for improving the mechanical fatigue performance of a submarine cable flexible joint comprises the following steps:

[0008] S1, measuring the geometric surface accuracy and surface roughness of the flexible joint before laser shot peening, and transmitting the geometric surface accuracy and surface roughness to the memory unit of the computer control system through the information acquisition system;

[0009] S2, the computer control system calculates the residual stress of the flexible joint under the action of the seabed load, and establishes a function of the relationship between the residual stress and the surface roughness and the fatigue life, which is composed of binary variables of the residual stress and the surface roughness, to form a first database;

[0010] S3. Determine the residual stress design value and surface roughness design value of the flexible joint according to the fatigue life target of the flexible joint;

[0011] S4, establishing the relationship between laser peening parameters and residual stress and surface roughness to form a second database;

[0012] S5, the surface roughness and the residual stress before laser shot peening are first measured values, and the required laser shot peening parameters are determined in a second database according to the first measured values, the residual stress design value, and the surface roughness design value;

[0013] S6. Perform laser shot peening on the surface of the flexible joint according to the required laser shot peening parameters;

[0014] S7, measuring the geometrical surface accuracy and surface roughness of the flexible joint after laser shot peening again, and measuring the residual stress of the flexible joint after laser shot peening, the surface roughness and residual stress of the flexible joint after laser shot peening are second measurement values, and the geometrical surface accuracy of the flexible joint after laser shot peening and the second measurement value are transmitted to the memory unit of the computer control system through the information acquisition system;

[0015] S8. The computer control system compares the second measured value with the residual stress design value and the surface roughness design value, and compares the geometric surface accuracy of the treated flexible joint with the geometric surface accuracy design value. If all of them meet the requirements, the laser shot peening treatment is determined to be qualified. If any one of them does not meet the requirements, the required laser shot peening parameters are re-determined in the second database based on the second measured value, the residual stress design value and the surface roughness design value, and S6-S8 are repeated, and the process is iterated repeatedly until the comparison result meets the design requirements.

[0016] Furthermore, the laser shot peening parameters include at least laser power, laser width, laser frequency, laser spot shape, laser spot diameter, spot overlap rate, laser scanning path, and thickness of the water coating layer on the flexible joint surface.

[0017] Furthermore, in S5 and S8, a traversal optimization method is used to determine the required laser peening parameters in the second database.

[0018] Further, in S6, the step of laser peening the surface of the flexible joint includes:

[0019] S6.1. The computer control system compiles the motion trajectory program of the part gripping robot and the water coating trajectory program of the water coating robot, and determines the laser peening area, the laser peening equipment laser emission timing series, and the laser light irradiation point in the peening area according to the required laser peening parameters, the pre-compiled motion trajectory program and the water coating trajectory program;

[0020] S6.2. According to the shape and size of the light spot output by the laser shot peening equipment, the computer control system cooperatively controls the linkage positioning of the part clamping robot and the water coating robot, and cooperatively controls the postures of the part clamping robot and the water coating robot.

[0021] Furthermore, in S6.1, the laser emitted by the laser shot peening equipment is a flat-top beam, the laser spot size is 2mm-8mm, the laser pulse width is 8ns-24ns, and the pulse repetition rate is 1HZ-20HZ.

[0022] The present invention also provides a device for improving the mechanical fatigue performance of submarine cable flexible joints, and the method for improving the mechanical fatigue performance of submarine cable flexible joints described above is executed by the device. The device includes a computer control system, a laser power supply, a laser shot peening device, a transmission lens group, a part clamping robot, and a water coating robot; the computer control system is connected to the laser power supply, the laser power supply is connected to the laser shot peening device, and the transmission lens group is arranged in front of the laser shot peening device; the part clamping robot is used to clamp the flexible joint, and the computer control system is connected to the part clamping robot and the water coating robot signals.

[0023] Furthermore, it also includes a measuring device, through which the geometric surface accuracy and the surface roughness of the flexible joint are measured together.

[0024] Furthermore, it also includes a residual stress measuring robot, through which the residual stress of the flexible joint is measured.

[0025] Furthermore, it also includes a light spot shape conversion device, which is used to convert a circular light spot into a square light spot.

[0026] Furthermore, it also includes a part clamping robot control system and a water coating robot control system, the computer control system is signal-connected to the part clamping robot control system, and the part clamping robot control system is signal-connected to the part clamping robot; the computer control system is signal-connected to the water coating robot control system, and the water coating robot control system is signal-connected to the water coating robot.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The present invention coordinates and controls the laser output spot shape and size, the parts clamping robot and the water coating robot through a computer control system, so as to adjust the water flow, water pressure and the normal angle of the water flow under different spot shapes and sizes to ensure the consistency between the laser shock wave impact area and the thickness of the water confinement layer, and prevent the splashing effect of the water flow;

[0029] (2) The present invention can control the geometric surface accuracy and surface roughness of the flexible joint surface by changing the flexible movement mode of the linked parts clamping robot and the water coating robot through the laser shot peening process parameters;

[0030] (3) The present invention forms a database consisting of the correspondence between the shape and size of the laser shot peening spot and the residual stress distribution, geometric surface accuracy and surface roughness built into the computer memory, monitors the residual stress of the flexible joint in real time, and determines the shape and size of the laser shot peening spot by artificial intelligence big data mining, so as to realize the accurate prediction and control of the laser shot peening treatment on the surface of the flexible joint;

[0031] (4) The present invention optimizes the laser shot peening strategy for the flexible joint surface in accordance with the flexible joint material properties and geometric size effects, thereby forming an optimized residual stress distribution of the flexible joint, which can significantly improve its fatigue life. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic structural diagram of a device for improving the mechanical fatigue performance of a submarine cable flexible joint according to an embodiment of the present invention;

[0033] Figure 2 This is a schematic diagram of the structure of connecting submarine cable conductors through flexible joints.

[0034] In the figure, 1. Parts clamping robot; 2. Transmission mirror group; 3. Spot shape conversion device; 4. Laser shot peening equipment; 5. Laser power supply; 6. Measuring equipment; 7. Information acquisition system; 8. Computer control system; 9. Residual stress measurement robot; 10. Water coating robot control system; 11. Parts clamping robot control system; 12. Water coating robot; 13. Submarine cable conductor; 14. Flexible joint. DETAILED DESCRIPTION

[0035] The following is an explanation of the embodiments of the present invention by specific specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Although the description of the present invention will be introduced in conjunction with the preferred embodiment, this does not mean that the features of the present invention are limited to the embodiment. On the contrary, the purpose of introducing the embodiments in conjunction with the embodiments is to cover other options or modifications that may be extended based on the claims of the present invention. In order to provide a deep understanding of the present invention, the following description will include many specific details. The present invention can also be implemented without using these details. In addition, in order to avoid confusion or blurring the key points of the present invention, some specific details will be omitted in the description. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0036] To make the objectives, technical solutions and advantages of the present invention more clear, embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0037] Embodiment 1

[0038] like Figure 2 As shown, the submarine cable conductor 13 can be connected through the flexible joint 14. During the manufacturing process of the flexible joint 14, a welding process is required to connect the submarine cable conductor 13. The traditional welding process causes tensile stress to be generated at the conductor weld. Due to the presence of tensile stress, the tensile properties and fatigue properties of the welding part of the flexible joint 14 are relatively low, which makes the flexible joint 14 easy to be damaged. In order to improve the tensile properties, fatigue resistance and electrochemical corrosion resistance of the flexible joint 14, the present invention provides a method and device for improving the mechanical fatigue properties of the submarine cable flexible joint.

[0039] A method for improving the mechanical fatigue performance of a submarine cable flexible joint comprises the following steps:

[0040] S1: Using a measuring device 6 to measure the geometrical surface accuracy and surface roughness of the flexible joint 14 before laser shot peening through a transmission lens group 2, and transmitting the geometrical surface accuracy and surface roughness to a memory unit of a computer control system 8 through an information acquisition system 7 having components such as sensors and converters;

[0041] S2: The computer control system 8 calculates the residual stress of the flexible joint 14 under the action of complex sea and mixed loads through the fluid-solid coupling method, and establishes a function of the relationship between the residual stress and the surface roughness and the fatigue life composed of the binary variables of the residual stress and the surface roughness according to the residual stress and the surface roughness, so as to form a first database; the function can be expressed as N=F(ε,σ), wherein N is the fatigue life function, ε is the residual stress parameter value, and σ is the surface roughness variable parameter.

[0042] S3. Determine the residual stress design value and surface roughness design value required for the flexible joint 14 according to the fatigue life target of the flexible joint 14;

[0043] S4. The relationship between laser peening parameters, residual stress distribution and surface roughness is established, which can be expressed as:

[0044]

[0045] ε is the residual stress parameter value, σ is the surface roughness variable parameter. A is the laser shock strengthening process variable parameter group, which at least includes A1, pulse laser power, A2, pulse laser width, A3, pulse laser frequency, A4, pulse laser spot shape, A5, pulse laser spot diameter, A6, spot overlap rate, A7, laser scanning path, A8, soft joint surface water coating thickness,

[0046] Thus forming a second database;

[0047] S5, the surface roughness and the residual stress before laser shot peening are taken as first measured values, and the required laser shot peening process parameters are determined in a second database by adopting a traversal optimization method according to the first measured values, the residual stress design value, and the surface roughness design value;

[0048] In the specific technical scheme of the present invention, in S1-S5, the geometric surface data and surface roughness of the flexible joint 14 are measured together by using a measuring device 6, and the measuring device 6 can be a high-precision optical scanner and a geometric accuracy measuring instrument, and is transmitted to a storage unit of a computer control system 8 through an information acquisition system 7 having components such as sensors and converters. The computer control system 8 can determine the change law of the shape and size of the laser spot according to the system's built-in database by adopting artificial intelligence data mining, and form laser shot peening parameters and change the laser shot peening energy distribution law.

[0049] S6. According to the required laser shot peening process parameters, the surface of the flexible joint 14 is subjected to laser shot peening treatment. The specific steps of laser shot peening treatment on the surface of the flexible joint 14 are shown in S6.1 and S6.2.

[0050] S6.1. The computer control system 8 compiles the motion trajectory program of the part clamping robot 1 and the water coating trajectory program of the water coating robot 12, and determines the blade laser peening area, the laser peening timing series of the laser peening equipment 4, and the laser light irradiation point in the peening area according to the required laser peening parameters, the motion trajectory program, and the water coating trajectory program, and starts and completes the laser peening treatment of the required processing parts on the surface of the flexible joint 14.

[0051] The laser shot peening equipment 4 can use a high-power pulsed laser. The laser emitted by the laser shot peening equipment 4 is a flat-top beam, the laser spot size is 2mm-8mm, the laser pulse width is 8ns-24ns, and the pulse repetition rate is 1HZ-20HZ. In this embodiment, the laser emitted by the laser shot peening equipment 4 is a flat-top beam, the output laser spot is a circular spot, the laser spot size is 2mm, the laser pulse width is 8ns, and the pulse repetition rate is 1Hz.

[0052] S6.2. According to the spot shape and size output by the laser shot peening equipment 4, the computer control system 8 coordinates the linkage positioning of the part clamping robot 1 and the water coating robot 12, and coordinates the posture of the part clamping robot 1 and the water coating robot 12 to perform laser shot peening treatment on the required treatment part of the surface of the flexible joint 14. As a result, under different spot shapes and sizes, the relationship ratio of water flow, water pressure and water flow normal angle is adjusted to ensure the consistency of the thickness of the water constraint layer in the laser shock wave impact area, and ensure the uniformity of the flow of the water constraint layer.

[0053] S7, using the measuring device 6 to monitor and measure the geometric surface accuracy and surface roughness of the flexible joint 14 after laser shot peening again, and at the same time, the small residual stress measuring robot 9 integrated in the system measures the residual stress of the flexible joint 14, and the surface roughness and residual stress of the flexible joint after laser shot peening are the second measurement values, and the geometric surface accuracy of the processed flexible joint and the second measurement value are transmitted to the memory unit of the computer control system 8 through the information acquisition system 7;

[0054] S8. The computer control system 8 compares the second measured value with the residual stress design value and the surface roughness design value, and compares the geometric surface accuracy of the flexible joint before treatment with the geometric surface accuracy design value. The geometric surface accuracy has nothing to do with the fatigue life of the flexible joint, but it also needs to be maintained within a certain error range. The geometric surface accuracy of the flexible joint after treatment is compared with the geometric surface accuracy design value to determine whether it meets the requirements. If the geometric surface accuracy, surface roughness and residual stress of the flexible joint after laser shot peening meet the requirements, the laser shot peening is judged to be qualified. If any one of them does not meet the requirements, the required laser shot peening process parameters are re-determined in the second database according to the comparison error using a traversal optimization method, and laser shot peening is performed, and this is iterated repeatedly until the comparison result meets the design requirements.

[0055] Embodiment 2

[0056] The difference between this embodiment and other embodiments is that the laser beam emitted by the laser shot peening equipment 4 is a flat-top beam, the output laser spot is a circular spot, the laser spot size is 3 mm, the laser pulse width is 24 ns, and the pulse repetition rate is 10 Hz.

[0057] Embodiment 3

[0058] The difference between this embodiment and other embodiments is that the laser beam emitted by the laser shot peening equipment 4 is a flat-top beam, the output laser spot is a square spot, the laser spot size is 2 mm, the laser pulse width is 8 ns, and the pulse repetition rate is 10 Hz.

[0059] Embodiment 4

[0060] The difference between this embodiment and other embodiments is that the laser beam emitted by the laser shot peening equipment 4 is a flat-top beam, the output laser spot is a square spot, the laser spot size is 3 mm, the laser pulse width is 24 ns, and the pulse repetition rate is 10 Hz.

[0061] Embodiment 5

[0062] The difference between this embodiment and other embodiments is that the laser shot peening beam is a flat-top beam, the output laser spot has two variations: circular and square spots, the laser spot size is adjusted within the range of 2-3mm, the laser pulse width is 16ns, and the pulse repetition rate is 20Hz.

[0063] Embodiment 6

[0064] like Figure 1 As shown, the present invention also provides a device for improving the mechanical fatigue performance of submarine cable flexible joints, and the method for improving the mechanical fatigue performance of submarine cable flexible joints described above is performed by the device, and the device includes a computer control system 8, a laser power supply 5, a laser shot peening device 4, a transmission lens group 2, a part clamping robot 1, and a water coating robot 12; the computer control system 8 is connected to the laser power supply 5, and the laser power supply 5 is connected to the laser shot peening device 4, and the laser shot peening device 4 is preferably a high-power pulse laser; the transmission lens group 2 is arranged in front of the laser shot peening device 4, and the light irradiation point can be changed by the lens group 2;

[0065] The part clamping robot 1 is used to clamp the flexible joint 14, and the water coating robot 12 is used to spray water to form a water film at the required processing position of the flexible joint 14, thereby constraining the shock wave and amplifying the compressive stress of the shock wave; the computer control system 8 is connected to the part clamping robot 1 and the water coating robot 12 by signal.

[0066] It also includes a measuring device 6, such as a high-precision optical scanner and a geometric accuracy measuring instrument, through which the geometric surface accuracy and the surface roughness of the flexible joint are measured together.

[0067] The residual stress measuring robot 9 is also included, and the residual stress of the flexible joint 14 is measured by the residual stress measuring robot 9 .

[0068] It also includes a light spot shape conversion device 3, for example, a square aperture can be used, and the light spot shape conversion device 3 is used to convert a circular light spot into a square light spot.

[0069] It also includes an information acquisition system 7, which is signal-connected to the measuring device 6, the residual stress measuring robot 9 and the computer control system 8. The information acquisition system 7 receives the measured geometric surface accuracy, surface roughness and residual stress, and transmits the received information to the memory unit of the computer control system 8.

[0070] It can also include a part clamping robot control system 11 and a water coating robot control system 10, the computer control system 8 is signal-connected to the part clamping robot control system 11, and the part clamping robot control system 11 is signal-connected to the part clamping robot 1; the computer control system 8 is signal-connected to the water coating robot control system 10, and the water coating robot control system 10 is signal-connected to the water coating robot 12.

[0071] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions of the technical solution of the present invention by ordinary technicians in this field do not deviate from the essence and scope of the technical solution of the present invention.

Claims

1. A method for improving the mechanical fatigue performance of a submarine cable flexible joint, characterized in that: The following steps are included: S1, measuring the geometric surface accuracy and surface roughness of the flexible joint before laser shot peening, and transmitting the geometric surface accuracy and surface roughness to the memory unit of the computer control system through the information acquisition system; S2, the computer control system calculates the residual stress of the flexible joint under the action of the seabed load, and establishes a function of the relationship between the residual stress and the surface roughness and the fatigue life, which is composed of binary variables of the residual stress and the surface roughness, to form a first database; S3. Determine the residual stress design value and surface roughness design value of the flexible joint according to the fatigue life target of the flexible joint; S4, establishing the relationship between laser peening parameters and residual stress and surface roughness to form a second database; S5, the surface roughness and the residual stress before laser shot peening are first measured values, and the required laser shot peening parameters are determined in a second database according to the first measured values, the residual stress design value, and the surface roughness design value; S6. Perform laser shot peening on the surface of the flexible joint according to the required laser shot peening parameters; S7, measuring the geometrical surface accuracy and surface roughness of the flexible joint after laser shot peening again, and measuring the residual stress of the flexible joint after laser shot peening, the surface roughness and residual stress of the flexible joint after laser shot peening are second measurement values, and the geometrical surface accuracy of the flexible joint after laser shot peening and the second measurement value are transmitted to the memory unit of the computer control system through the information acquisition system; S8. The computer control system compares the second measured value with the residual stress design value and the surface roughness design value, and compares the geometric surface accuracy of the treated flexible joint with the geometric surface accuracy design value. If all of them meet the requirements, the laser shot peening treatment is determined to be qualified. If any one of them does not meet the requirements, the required laser shot peening parameters are re-determined in the second database based on the second measured value, the residual stress design value and the surface roughness design value, and S6-S8 are repeated, and the process is iterated repeatedly until the comparison result meets the design requirements.

2. The method for improving the mechanical fatigue performance of a submarine cable flexible joint according to claim 1, characterized in that: The laser shot peening parameters include at least laser power, laser width, laser frequency, laser spot shape, laser spot diameter, spot overlap rate, laser scanning path, and thickness of the water coating layer on the flexible joint surface.

3. The method for improving the mechanical fatigue performance of a submarine cable flexible joint according to claim 1, characterized in that: In S5 and S8, the required laser peening parameters are determined in the second database by using a traversal optimization method.

4. The method for improving the mechanical fatigue performance of a submarine cable flexible joint according to claim 1, characterized in that: In S6, the step of laser peening the surface of the flexible joint includes: S6.

1. The computer control system compiles the motion trajectory program of the part gripping robot and the water coating trajectory program of the water coating robot, and determines the laser peening area, the laser peening equipment laser emission timing series, and the laser light irradiation point in the peening area according to the required laser peening parameters, the pre-compiled motion trajectory program and the water coating trajectory program; S6.

2. According to the shape and size of the light spot output by the laser shot peening equipment, the computer control system cooperatively controls the linkage positioning of the part clamping robot and the water coating robot, and cooperatively controls the postures of the part clamping robot and the water coating robot.

5. The method for improving the mechanical fatigue performance of a submarine cable flexible joint according to claim 4, characterized in that: In S6.1, the laser emitted by the laser shot peening equipment is a flat-top beam, the laser spot size is 2mm-8mm, the laser pulse width is 8ns-24ns, and the pulse repetition rate is 1HZ-20HZ.

6. A device for improving the mechanical fatigue performance of a submarine cable flexible joint, characterized in that: The method for improving the mechanical fatigue performance of the flexible joint of a submarine cable as described in any one of claims 1 to 5 is performed by the device, and the device includes a computer control system, a laser power supply, a laser shot peening device, a transmission lens group, a part clamping robot, and a water coating robot; the computer control system is connected to the laser power supply, and the laser power supply is connected to the laser shot peening device, and the transmission lens group is arranged in front of the laser shot peening device; the part clamping robot is used to clamp the flexible joint, and the computer control system is connected to the part clamping robot and the water coating robot by signal.

7. The device for improving the mechanical fatigue performance of a submarine cable flexible joint according to claim 6 is characterized in that: It also includes a measuring device, through which the geometric surface accuracy and the surface roughness of the flexible joint are measured.

8. The device for improving the mechanical fatigue performance of a submarine cable flexible joint according to claim 7 is characterized in that: It also includes a residual stress measuring robot, which is used to measure the residual stress of the flexible joint.

9. The device for improving the mechanical fatigue performance of a submarine cable flexible joint according to claim 8, characterized in that: It also includes a light spot shape conversion device, which is used to convert a circular light spot into a square light spot.

10. The device for improving the mechanical fatigue performance of a submarine cable flexible joint according to claim 9, characterized in that: It also includes a parts clamping robot control system and a water coating robot control system, the computer control system is connected to the parts clamping robot control system signal, and the parts clamping robot control system is connected to the parts clamping robot signal; the computer control system is connected to the water coating robot control system signal, and the water coating robot control system is connected to the water coating robot signal.

Images