Method and device for improving the mechanical fatigue performance of a submarine cable soft joint

Abstract

The application provides a method and device for improving the mechanical fatigue performance of a submarine cable soft joint, and relates to the technical field of ocean engineering. The method first measures the surface roughness and residual stress of the soft joint before treatment, obtains a first measurement value, and obtains the geometric surface accuracy of the soft joint before treatment, and determines the residual stress design value and the surface roughness design value of the soft joint according to the fatigue life target, determines the required laser shot parameter in the second database according to the first measurement value and the design value, and performs laser shot treatment on the surface of the soft joint according to the parameter until the geometric surface accuracy, the surface roughness and the residual stress of the soft joint all meet the design requirements. The device comprises a computer control system, a laser power supply, a laser shot device, a transmission lens group, a part clamping robot and a water spraying robot. The method and device provided by the application can improve the tensile performance, the fatigue resistance and the electrochemical corrosion resistance of the soft joint.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of ocean engineering, and particularly relates to a method and device for improving the mechanical fatigue performance of a submarine cable soft joint. BACKGROUND

[0002] With the increasing demand for national resource exploration, the scale of development and utilization of marine and island resources is also increasing, the application of submarine cables is rapidly developing, and the demand is increasing. The requirements and needs for high-voltage and long-distance submarine cables are also increasing. The key to solving long-distance cables is the soft joint of the cable. In addition to considering cross-linking extrusion vulcanization and degassing process in the manufacturing process of the soft joint, welding process is needed to connect the cable conductor during the manufacturing process of the soft joint. Due to the traditional welding process, tensile stress is generated at the weld of the conductor. Due to the existence of tensile stress, the tensile properties and fatigue properties of the soft joint welding site are low. Under the action of various ocean current loads such as tension, pressure, and torsion, the soft joint is easily damaged. As we all know, it is difficult to replace and maintain the soft joint in such a complex and harsh environment under the sea, which increases the maintenance and maintenance cost of the submarine cable.

[0003] Therefore, a method and device are needed to improve the tensile properties, fatigue properties, and electrochemical corrosion resistance of the submarine cable soft joint. SUMMARY

[0004] The present application provides a method and device for improving the mechanical fatigue performance of a submarine cable soft joint, which addresses the problems of the prior art. The surface of the soft joint is treated by laser shot peening according to the fatigue life target of the soft joint, thereby improving the service time and life of the submarine cable soft joint under the sea.

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

[0006] A method for improving the mechanical fatigue performance of a submarine cable soft joint, comprising the following steps,

[0007] A method for improving the mechanical fatigue performance of a submarine cable soft joint, comprising the following steps,

[0008] S1, measuring the geometric surface accuracy and surface roughness of the soft 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 soft joint under the action of the submarine load, and establishes a function of the relationship between the residual stress and the surface roughness according to the residual stress and the surface roughness, and forms a first database;

[0010] S3, determining a residual stress design value and a surface roughness design value of the soft joint according to a fatigue life target of the soft joint;

[0011] S4, establishing a 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 peening treatment are first measurement values, and required laser peening parameters are determined in the second database according to the first measurement values, the residual stress design value and the surface roughness design value;

[0013] S6, laser peening treatment is performed on the surface of the soft joint according to the required laser peening parameters;

[0014] S7, the geometric surface precision and the surface roughness of the soft joint after laser peening treatment are measured again, and the residual stress of the treated soft joint is measured, the surface roughness and the residual stress of the soft joint after laser peening treatment are second measurement values, and the geometric surface precision of the treated soft joint and the second measurement values are transmitted to the memory unit of the computer control system through the information collection system;

[0015] S8, the computer control system compares the second measurement values with the residual stress design value and the surface roughness design value, and compares the geometric surface precision of the treated soft joint with the geometric surface precision design value, if all meet the requirements, it is determined that the laser peening treatment is qualified, if any one does not meet the requirements, the required laser peening parameters are determined again in the second database according to the second measurement values, the residual stress design value and the surface roughness design value, and S6-S8 are repeated, and the iteration is repeated until the comparison result meets the design requirements.

[0016] Further, the laser peening parameters at least include laser power, laser width, laser frequency, laser spot shape, laser spot diameter, spot overlap rate, laser scanning path, and soft joint surface water layer thickness.

[0017] Further, in S5 and S8, the required laser peening parameters are determined in the second database by using traversal optimization.

[0018] Further, in S6, the step of performing laser peening treatment on the surface of the soft joint comprises,

[0019] S6.1, the computer control system compiles a motion trajectory program of a part clamping robot and a water coating trajectory program of a water coating robot, determines a laser peening area, a laser emission timing series of a laser peening device, and a laser light irradiation point of 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 spot shape and size of the laser shot peening device output, the computer control system cooperates to control the linkage positioning of the part clamping robot and the water coating robot, and cooperates to control the posture of the part clamping robot and the water coating robot.

[0021] Further, in S6.1, the laser emitted by the laser shot peening device 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 application also provides a device for improving the mechanical fatigue performance of a submarine cable soft joint, which executes the method for improving the mechanical fatigue performance of a submarine cable soft joint described above, and comprises 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.

[0023] Further, a measuring device is further included, which measures the geometric surface accuracy and the surface roughness of the soft joint.

[0024] Further, a residual stress measuring robot is further included, which measures the residual stress of the soft joint.

[0025] Further, a spot shape conversion device is further included, which is used to convert a circular spot into a square spot.

[0026] Further, a part clamping robot control system and a water coating robot control system are further included, the computer control system is signal connected with the part clamping robot control system, and the part clamping robot control system is signal connected with the part clamping robot; the computer control system is signal connected with the water coating robot control system, and the water coating robot control system is signal connected with the water coating robot.

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

[0028] (1) The present application coordinates the linkage positioning of the laser output spot shape and size, the part clamping robot and the water coating robot through the computer control system, so as to adjust the relationship between the water flow, water pressure and water flow normal angle proportion to ensure the consistency of the laser shock wave impact area and the water constraint layer thickness in the case of different spot shapes and sizes, and prevent the splashing effect of the water flow;

[0029] (2) The present application changes the flexible movement mode of the linkage part clamping robot and the water coating robot through the laser shot blasting process parameters, so as to realize the control of the surface geometric surface precision and surface roughness of the soft joint;

[0030] (3) The present application forms a database by the corresponding relationship between the laser shot blasting spot shape and size and the residual stress distribution, geometric surface precision and surface roughness in the computer memory, real-time monitors the residual stress of the soft joint, determines the laser shot blasting spot shape and size through the artificial intelligence big data mining method, and can realize the accurate prediction and control of the surface laser shot blasting treatment of the soft joint;

[0031] (4) The present application optimizes the laser shot blasting strategy of the soft joint surface according to the material characteristics and geometric size effect of the soft joint, forms an optimized residual stress distribution of the soft joint, and can greatly improve the fatigue life. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The structure schematic view of the device for improving the mechanical fatigue performance of the soft joint of the submarine cable in the embodiment provided by the present application;

[0033] Figure 2 The structure schematic view of the submarine cable conductor connected by the soft joint.

[0034] In the figure, 1, part clamping robot; 2, transmission lens group; 3, spot shape conversion device; 4, laser shot blasting equipment; 5, laser power supply; 6, measuring equipment; 7, information acquisition system; 8, computer control system; 9, residual stress measuring robot; 10, water coating robot control system; 11, part clamping robot control system; 12, water coating robot; 13, submarine cable conductor; 14, soft joint. DETAILED DESCRIPTION

[0035] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Although the description of the present invention is presented in conjunction with preferred embodiments, this does not mean that the features of the present invention are limited to these embodiments. On the contrary, the purpose of the description in conjunction with the embodiments is to cover other options or modifications that may be derived based on the claims of the present invention. To provide a deep understanding of the present invention, many specific details will be included in the following description. The present invention may also be implemented without using these details. Furthermore, to avoid confusion or obscuring the focus of the present invention, some specific details will be omitted in the description. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

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

[0037] Example 1

[0038] like Figure 2 As shown, the submarine cable conductor 13 can be connected by a flexible joint 14. The manufacturing process of the flexible joint 14 requires welding to connect the submarine cable conductor 13. Due to the traditional welding process, tensile stress is generated at the conductor weld. The presence of tensile stress will reduce the tensile properties and fatigue properties of the weld at the flexible joint 14, making the flexible joint 14 prone to damage. In order to improve the tensile properties, fatigue resistance and electrochemical corrosion resistance of the flexible joint 14, this invention provides a method and apparatus for improving the mechanical fatigue properties of submarine cable flexible joints.

[0039] A method for improving the mechanical fatigue performance of submarine cable flexible joints includes the following steps:

[0040] S1: The geometric accuracy and surface roughness of the flexible joint 14 before laser shot peening are measured by the measuring device 6 through the transmission mirror group 2, and the geometric accuracy and surface roughness are transmitted to the memory unit of the computer control system 8 through the information acquisition system 7 with components such as sensors and converters.

[0041] S2: The computer control system 8 calculates the residual stress of the flexible joint 14 under complex marine loads using the fluid-structure interaction method, and establishes a function relating the residual stress and surface roughness as binary variables to fatigue life based on the residual stress and surface roughness, forming the first database; this function can be expressed as N=F(ε,σ), where 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 the surface roughness design value required by the soft joint 14 according to the fatigue life target of the soft joint 14;

[0043] S4, the relationship between the laser shot parameter and the residual stress distribution and the surface roughness 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 processing technology variable parameter group, at least containing 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 layer thickness,

[0046] In this way, a second database is formed;

[0047] S5, the surface roughness and the residual stress before laser shot processing are first measurement values, and the required laser shot process parameters are determined in the second database by using an exhaustive optimization method according to the first measurement values, the residual stress design value and the surface roughness design value.

[0048] In the specific technical solutions of the present application, in S1-S5, the geometric surface data and the surface roughness of the soft joint 14 are measured by using a measuring device 6, which can be a high-precision optical scanner and a geometric precision measuring instrument, and are transmitted to the storage unit of the computer control system 8 through the information acquisition system 7 with sensors, converters and other elements. The computer control system 8 can determine the variation law of the laser spot shape and size by using artificial intelligence data mining according to the built-in database of the system, and form the laser shot parameters and the change law of the laser shot energy distribution.

[0049] S6, according to the required laser shot process parameters, the surface of the soft joint 14 is processed by laser shot; wherein the specific steps of processing the surface of the soft joint 14 by laser shot 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, determines the blade laser shot area, the laser shot device 4 emission laser timing series, the shot area laser light irradiation point according to the required laser shot parameters, the motion trajectory program and the water coating trajectory program, and opens and completes the laser shot processing of the required processing part of the surface of the soft joint 14.

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

[0052] S6.2. According to the spot shape and size output by the laser shot peening device 4, the computer control system 8 cooperatively controls the linkage positioning of the part clamping robot 1 and the water spraying robot 12, and cooperatively controls the postures of the part clamping robot 1 and the water spraying robot 12, so as to perform laser shot peening treatment on the required treatment part of the surface of the soft joint 14. In this way, under different spot shapes and sizes, the relationship between the water flow, the water pressure and the water flow normal angle is adjusted to ensure the consistency of the thickness of the water constraint layer of the laser shock wave impact area and the uniformity of the water constraint layer flow.

[0053] S7. The measurement device 6 is used to monitor and measure the geometric surface accuracy and surface roughness of the soft joint 14 after laser shot peening treatment, and the small residual stress measurement robot 9 integrated in the system is used to measure the residual stress of the soft joint 14. The surface roughness and residual stress of the soft joint after laser shot peening treatment are the second measurement values, and the geometric surface accuracy of the treated soft joint and the second measurement values 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 measurement values with the residual stress design values and the surface roughness design values, and compares the geometric surface accuracy of the soft joint before treatment with the geometric surface accuracy design values. The geometric surface accuracy is irrelevant to the fatigue life of the soft joint, but also needs to be kept within a certain error range. The geometric surface accuracy of the soft joint after treatment is compared with the geometric surface accuracy design values to determine whether the requirements are met. If the geometric surface accuracy, the surface roughness and the residual stress of the soft joint after laser shot peening treatment all meet the requirements, it is determined that the laser shot peening treatment is qualified. If any one does not meet the requirements, the required laser shot peening process parameters are re-confirmed in the second database by using the traversal optimization method according to the comparison error, and laser shot peening treatment is performed. This iteration is repeated until the comparison result meets the design requirements.

[0055] Embodiment Two

[0056] The difference between this embodiment and other embodiments is that the laser beam emitted by the laser shot peening device 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] Example three

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

[0059] Example four

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

[0061] Example five

[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 is a circular and square spot, the laser spot size is adjusted in the range of 2-3mm, the laser pulse width is 16ns, and the pulse repetition rate is 20Hz.

[0063] Example six

[0064] As shown in Figure 1 The application also provides a device for improving the mechanical fatigue performance of a submarine cable soft joint, which executes the method for improving the mechanical fatigue performance of a submarine cable soft joint described above, and comprises 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 spraying robot 12. The computer control system 8 is connected with the laser power supply 5, the laser power supply 5 is connected with the laser shot peening device 4, and preferably the laser shot peening device 4 is a high-power pulsed 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 through the lens group 2.

[0065] The part clamping robot 1 is used for clamping the soft joint 14, and the water spraying robot 12 is used for spraying water to form a water film at the required processing position of the soft joint 14, so as to constrain the shock wave and amplify the compressive stress of the shock wave. The computer control system 8 is signal connected with the part clamping robot 1 and the water spraying robot 12.

[0066] It also comprises a measuring device 6, such as a high-precision optical scanner and a geometric precision measuring instrument, which are used together to measure the geometric surface precision and the surface roughness of the soft joint.

[0067] A residual stress measuring robot 9 is further included, and the residual stress of the soft joint 14 is measured by the residual stress measuring robot 9.

[0068] A light spot shape conversion device 3 is further included, which can be a square diaphragm, and is used for converting a circular light spot into a square light spot.

[0069] An information acquisition system 7 is further included, which is signal connected with the measuring device 6, the residual stress measuring robot 9 and the computer control system 8, receives the measured geometric surface precision, surface roughness and residual stress, and transmits the received information to the memory unit of the computer control system 8.

[0070] A part clamping robot control system 11 and a water coating robot control system 10 can be further included, the computer control system 8 is signal connected with the part clamping robot control system 11, the part clamping robot control system 11 is signal connected with the part clamping robot 1; the computer control system 8 is signal connected with the water coating robot control system 10, and the water coating robot control system 10 is signal connected with the water coating robot 12.

[0071] Finally, it should be noted that the above content is only used to illustrate the technical solutions of the present application, and is not a limitation on the protection scope of the present application, and the simple modification or equivalent replacement of the technical solutions of the present application by the ordinary skilled in the art does not deviate from the essence and scope of the technical solutions of the present application.

Claims

1. A method of improving the mechanical fatigue performance of a submarine cable soft joint, characterized in that: The method comprises the following steps, S1, measuring the geometric surface accuracy and surface roughness of the soft joint before laser 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 soft joint under the load of the seabed, and establishes a function of the relationship between the residual stress and the surface roughness according to the residual stress and the surface roughness, and forms a first database; the function can be expressed as wherein, is a fatigue life function, is a residual stress parameter value, is a surface roughness variable parameter; S3, determining the residual stress design value and surface roughness design value of the soft joint according to the fatigue life target of the soft joint; S4, establishing the relationship between the laser peening parameters and the residual stress and surface roughness to form a second database; represented as: ； is a residual stress parameter value, is a surface roughness variable parameter, is a set of laser shock peening process variable parameters, at least containing a pulse laser power, a pulse laser width, a pulse laser frequency, a pulse laser spot shape, a pulse laser spot diameter, a spot overlap ratio, a laser scanning path, a soft joint surface water layer thickness; S5, the surface roughness and the residual stress before laser peening are first measurement values, and the required laser peening parameters are determined in the second database according to the first measurement values, the residual stress design value and the surface roughness design value; S6, laser peening is performed on the surface of the soft joint according to the required laser peening parameters; S7, the geometric surface accuracy and surface roughness of the soft joint after laser peening are measured again, and the residual stress of the processed soft joint is measured, the surface roughness and the residual stress of the soft joint after laser peening are second measurement values, and the geometric surface accuracy of the processed soft joint and the second measurement values are transmitted to the memory unit of the computer control system through the information acquisition system; S8, the computer control system compares the second measurement values with the residual stress design value and the surface roughness design value, and compares the geometric surface accuracy of the processed soft joint with the geometric surface accuracy design value, if all meet the requirements, it is determined that the laser peening is qualified, if any one does not meet the requirements, the required laser peening parameters are determined again in the second database according to the second measurement values, the residual stress design value and the surface roughness design value, and S6-S8 are repeated, and the iteration is repeated until the comparison result meets the design requirements.

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

3. The method of improving the mechanical fatigue performance of a subsea cable soft joint of claim 1, wherein: In S5 and S8, the required laser peening parameters are determined in the second database by using traversal optimization method.

4. The method of improving the mechanical fatigue performance of a subsea cable soft joint of claim 1, wherein: In S6, the step of laser peening on the surface of the soft joint comprises, S6.1, the computer control system compiles the motion trajectory program of the part clamping robot and the water coating trajectory program of the water coating robot, determines the laser peening area, the laser emission timing series of the laser peening device, and the laser light irradiation point of 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 spot shape and size output by the laser peening device, the computer control system cooperatively controls the linkage positioning of the part clamping robot and the water coating robot, and cooperatively controls the posture of the part clamping robot and the water coating robot.

5. The method of improving the mechanical fatigue performance of a subsea cable soft joint according to claim 4, characterized in that: In S6.1, the laser emitted by the laser peening device 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 soft joint, characterized in that: The method for improving the mechanical fatigue performance of a submarine cable soft joint according to any one of claims 1-5 is performed by the device, which comprises 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 laser shot peening device is provided with the transmission lens group in front; the part clamping robot is used to clamp the soft joint, and the computer control system is signal-connected to the part clamping robot and the water coating robot.

7. The device for improving the mechanical fatigue performance of a subsea cable soft joint according to claim 6, characterized in that: The device further comprises a measuring device, which is used to measure the geometric surface accuracy and the surface roughness of the soft joint.

8. The device for improving the mechanical fatigue performance of a subsea cable soft joint according to claim 7, characterized in that: The device further comprises a residual stress measuring robot, which is used to measure the residual stress of the soft joint.

9. The device for improving the mechanical fatigue performance of a subsea cable soft joint according to claim 8, characterized in that: The device further comprises 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 subsea cable soft joint according to claim 9, characterized in that: The device further comprises 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.

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