Method for evaluating fatigue strength of semi-submersible platform

Abstract

The invention relates to the technical field of ship and ocean engineering, and particularly discloses a semi-submersible platform fatigue strength evaluation method, through which the fatigue damage condition of a structure at the most vulnerable hot spot position can be efficiently and accurately evaluated in the actual operation process of a semi-submersible platform, and the fatigue strength of the semi-submersible platform can be evaluated by evaluating and adjusting the loading and subsequent operation states of the structure in real time. And hidden risks caused by fatigue damage of the semi-submersible platform are reduced to the maximum extent. And the current damage condition of the semi-submersible platform can be quickly predicted based on numerical data obtained by a high-precision simulation model and real-time stress-strain field and crack tip opening displacement data obtained by a monitoring system. Meanwhile, black box processing is performed on the data through digital twinning, so that the problem of time consumption of calculation can be avoided, and the survival rate of the semi-submersible platform is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of ship and ocean engineering, and particularly relates to a fatigue strength evaluation method for a semi-submersible platform. Background Art

[0002] As a common form of ocean structure, the semi-submersible platform has the advantage of good wave and wind resistance. It is a platform form widely used in offshore drilling, mining and scientific research at present. Most semi-submersible platforms are integrated processing platforms, with a working deck on the upper part, a pontoon structure on the lower part, and support columns connecting them. The semi-submersible platform usually needs to operate in harsh sea conditions for a long time. For some special platforms, it even needs to complete high-speed navigation in harsh sea conditions. Therefore, the connection strength of its key nodes is often greatly tested. How to effectively predict the fatigue of the structure and how to effectively monitor the occurrence of structural fatigue and repair it in time are the core problems in the current design of semi-submersible platforms.

[0003] The fatigue design of existing semi-submersible platforms often ensures no fatigue damage during operation by reserving a large amount of redundancy. Even for semi-submersible platforms that are regularly dry-docked for inspection, the lowest safety factor required by the code is usually not taken, resulting in more structural strengthening costs. At the same time, for the regular fatigue detection of existing semi-submersible platforms, it is often carried out by flaw detection or visual inspection, which is easy to miss, and it is almost impossible to detect small cracks in the initial stage, leaving potential safety hazards. In addition, existing digital twin monitoring methods for semi-submersible platforms are all based on fatigue life monitoring, with huge computational amounts in the database formation link and extremely difficult in actual application.

[0004] Therefore, there is an urgent need for a fatigue strength evaluation method for a semi-submersible platform to solve the above problems. Summary of the Invention

[0005] The purpose of the present invention is to provide a fatigue strength evaluation method for a semi-submersible platform, which can improve the efficiency and quality of fatigue evaluation and monitoring of the semi-submersible platform, reduce the fatigue margin in the design stage, and reduce the design cost.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a fatigue strength evaluation method for a semi-submersible platform, including:

[0008] S100: Design and screen out the limit working conditions that cause the highest fatigue damage rate of the semi-submersible platform to be evaluated under various different operating states;

[0009] S200: For each of the screened design limit working conditions, calculate the fatigue damage rate at the key connection structures, and determine the most vulnerable hot spot positions corresponding to each of the design limit working conditions;

[0010] S300: For each of the most vulnerable hot spot locations, calculate the stress and strain field distributions in the areas near the crack propagation directions under different crack lengths and directions according to the different operating conditions of the semi-submersible platform to be evaluated, so as to form the maximum stress and strain at different crack lengths, and the opening displacement limit value as the fatigue screening criterion.

[0011] S400: For each of the most vulnerable hot spot locations, a fatigue monitoring system is correspondingly set up to obtain the stress and strain field distribution in the area near the most vulnerable hot spot location during the actual operation of the semi-submersible platform and the crack opening displacement data after cracks occur.

[0012] S500: Compare and evaluate the stress and strain field in the area near the obtained most vulnerable hot spot location with the fatigue screening criterion.

[0013] As a preferred technical solution of the above semi-submersible platform fatigue strength evaluation method, after S500, the semi-submersible platform fatigue strength evaluation method further includes:

[0014] S600: If the stress and strain field in the area near the obtained most vulnerable hot spot location exceeds the fatigue screening criterion, predict the remaining life under specific operating conditions; if the stress and strain field in the area near the obtained most vulnerable hot spot location does not exceed the fatigue screening criterion, the fatigue monitoring system continues to monitor.

[0015] As a preferred technical solution of the above semi-submersible platform fatigue strength evaluation method, in S400, the fatigue monitoring system includes a surface strain monitoring module and a crack tip opening displacement monitoring module. The surface strain monitoring module is used to monitor the surface stress and strain field in the area of the most vulnerable hot spot location, and the crack tip opening displacement monitoring module is used to monitor the surface crack tip opening displacement data in the area of the most vulnerable hot spot location.

[0016] As a preferred technical solution of the above semi-submersible platform fatigue strength evaluation method, the surface strain monitoring module includes several groups of strain gauges, and several groups of the strain gauges are covered and arranged in the area of the most vulnerable hot spot location. The crack tip opening displacement monitoring module includes a displacement sensor, the displacement sensor has two monitoring foot points, and the two monitoring foot points straddle the area of the most vulnerable hot spot location. The fatigue monitoring system further includes a data integration and analysis module and a data acquisition device. The data acquisition device is used to receive the data monitored by several groups of the strain gauges and the displacement sensor, and the data integration and analysis module is communicatively connected to the data acquisition device.

[0017] As a preferred technical solution of the above semi-submersible platform fatigue strength evaluation method, the surface strain monitoring module further includes a first data transmission unit, and a plurality of groups of strain gauges are communicatively connected to the first data transmission unit. The crack tip opening displacement monitoring module further includes a second data transmission unit, and the displacement sensor is communicatively connected to the second data transmission unit. Both the first data transmission unit and the second data transmission unit are communicatively connected to the data acquisition device.

[0018] As a preferred technical solution of the above semi-submersible platform fatigue strength evaluation method, two adjacent groups of the strain gauges are arranged staggeredly.

[0019] As a preferred technical solution of the above semi-submersible platform fatigue strength evaluation method, the fatigue monitoring system further includes a wave protection device, and the wave protection device covers the surface strain monitoring module and the crack tip opening displacement monitoring module.

[0020] As a preferred technical solution of the above semi-submersible platform fatigue strength evaluation method, in S200, fatigue scans are respectively performed on the key connection structures according to the environmental conditions corresponding to the navigation conditions and operation conditions and different operation drafts, so as to screen and determine the most vulnerable hot spot positions.

[0021] As a preferred technical solution of the above semi-submersible platform fatigue strength evaluation method, the positions of the fatigue scans at least include the moonpool and the corner of the cabin, the connection nodes of the column and the deck box, the connection nodes of the column and the cross brace, and the connection nodes of the column and the lower floating body.

[0022] As a preferred technical solution of the above semi-submersible platform fatigue strength evaluation method, in S300, a high-fidelity digital model is adopted, and according to the platform loading, operation environment and preset crack size, the stress-strain field distributions in the regions near the crack propagation directions with different crack lengths and directions at each of the most vulnerable hot spot positions are calculated.

[0023] The beneficial effects of the present invention are as follows:

[0024] The present invention provides a semi-submersible platform fatigue strength evaluation method. Through this method, during the actual operation of the semi-submersible platform, the fatigue damage conditions of the structures at the most vulnerable hot spot positions can be efficiently and accurately evaluated, and the loading and subsequent operation states of the structures can be adjusted through real-time evaluation, so as to minimize the hidden risks brought by the fatigue damage of the semi-submersible platform. Based on the numerical data obtained from the high-precision simulation model and the real-time stress-strain field and crack tip opening displacement data obtained from the monitoring system, the current damage conditions of the platform can be quickly predicted. At the same time, by performing black-box processing on the data through digital twin, the problem that the fatigue calculation is extremely time-consuming during real-time monitoring can be avoided, thereby greatly improving the monitoring efficiency and safety of the semi-submersible platform. Description of the Drawings

[0025] Figure 1 Schematic flow chart of the semi-submersible platform fatigue strength assessment method provided by the present invention;

[0026] Figure 2 Schematic of the operation of the fatigue monitoring system provided by the present invention Figure 1 ;

[0027] Figure 3 Schematic of the operation of the fatigue monitoring system provided by the present invention Figure 2 ;

[0028] Figure 4 Principle flow chart of the fatigue monitoring system provided by the present invention.

[0029] Wherein:

[0030] 100, strain gauge; 200, data acquisition device; 300, wireless transmission device; 400, displacement sensor. Detailed implementation manners

[0031] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

[0032] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance. Among them, the terms "first position" and "second position" are two different positions.

[0033] Unless otherwise clearly defined and limited, the terms "installed", "connected", "connected", "fixed" should be understood in a broad sense. For example, it can be a fixed connection or a detachable connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0034] Unless otherwise clearly specified and defined, the first feature being "on" or "under" the second feature may include the direct contact between the first feature and the second feature, or may also include the contact between the first feature and the second feature through additional features therebetween. Moreover, the first feature being "above", "over" and "on top of" the second feature includes that the first feature is directly above and obliquely above the second feature, or merely means that the horizontal height of the first feature is higher than that of the second feature. The first feature being "under", "below" and "beneath" the second feature includes that the first feature is directly below and obliquely below the second feature, or merely means that the horizontal height of the first feature is lower than that of the second feature.

[0035] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific embodiments.

[0036] As Figures 1 to 4 shown, the present embodiment provides a method for evaluating the fatigue strength of a semi-submersible platform, and the method for evaluating the fatigue strength of the semi-submersible platform includes:

[0037] S100: Design and screen out the extreme working conditions that cause the highest fatigue damage rate of the semi-submersible platform to be evaluated under various different operating conditions. Specifically, for a semi-submersible platform to be evaluated, according to its overall loading details and operation manual, the target extreme working conditions with the highest stress level are screened out respectively according to the loading form, the height of the platform's center of gravity, and the state of the variable load on the deck.

[0038] It should be noted that when determining the operating conditions with the largest proportion during the operation of the semi-submersible platform, the operating platform usually takes the operating conditions as the main ones. The operating conditions can also be divided into different drafts. If the semi-submersible platform considers navigation, the navigation should also have a certain proportion, as well as a very small number of survival conditions. The purpose of the present invention is to focus on the fatigue life of the structure. Therefore, the operating conditions and the navigation conditions are mainly considered, and the influence of the survival conditions can be ignored. Based on this, the operating conditions that may cause the largest deformation of the hot spot structure are initially screened out. In actual screening, the most severe loading condition with the diagonal loading in still water or the highest center of gravity of the platform can be used as the screening principle to screen out the most dangerous loading conditions under different drafts.

[0039] S200: For each selected design limit condition, calculate the fatigue damage rate at the key connection structures and determine the most vulnerable hot spot locations corresponding to each design limit condition. Specifically, for the loading corresponding to each design limit condition, perform fatigue scanning on the key connection structures according to the environmental conditions corresponding to the navigation condition and the operation condition. The hot spot locations for fatigue scanning should be key connection nodes. For a semi-submersible platform, it should at least include the connection nodes between the columns and the deck box, the connection nodes between the columns and the cross braces, and the connection nodes between the columns and the lower floating body. If there is a moonpool, the corner nodes of the moonpool should be concerned. If there are heavy equipment such as towers, the connection nodes between the tower and the deck box should be concerned. The fatigue scanning should at least include the above key nodes, calculate the fatigue damage rate of the key connection structures, and determine the most vulnerable locations at the key connection structures. Assume that the key connection structure is a key node gusset. For each element, there is a corresponding fatigue damage rate. According to the distribution of this fatigue damage rate, determine the vulnerable area. This area should be the element corresponding to the maximum fatigue damage rate and its surrounding area. The screening principle for the surrounding area is that the damage of this element is not less than 50% of the maximum fatigue damage element. Determine the area composed of all the selected elements as the fatigue vulnerable area and use it as the target location for fatigue monitoring.

[0040] It should be noted that the calculation of the fatigue damage rate can be carried out using various simulation software. In the present invention, DNV-SESAM is recommended. The fatigue screening should be based on the S-N curve that can highlight the hot spot damage distribution and is suitable for the fatigue calculation of the current area. Although this is a free edge here, in order to obtain a certain fatigue damage gradient, it is recommended to use the E curve for screening. In addition, there are various selection methods for the hot spot stress used in fatigue calculation. On the premise that the element size meets the design requirements, select the maximum nodal stress on the surface of the element for the free edge area and select the maximum nodal stress at the center of the element for the area near the weld toe.

[0041] S300: For each most vulnerable hot spot location, according to different operating conditions of the semi-submersible platform to be evaluated, calculate the stress and strain field distributions in the areas near the crack propagation direction under different crack lengths and directions, so as to form the maximum stress and strain at different crack lengths, and the opening displacement limit value as the fatigue screening criterion. Specifically, use a high-fidelity digital model to calculate the stress and strain field distributions and opening displacements in the fatigue vulnerable areas screened out. Among them, the calculations include the effects of loading under different operating conditions such as navigation, operation, and survival, different draft heights, and different wave heights, wave directions, and wave periods, and obtain the stress and strain fields and opening displacements in the vulnerable areas of the complete structure under various environmental conditions and loadings. Then, preset cracks in the hot spot areas. For each same crack starting position, the crack lengths and propagation directions are different. The crack length should range from 0.1 mm to not less than the thickness of the bracket plate, with a change interval of 0.1 mm. The crack propagation direction needs to be set and calculated every 1° within the range of 45° along the maximum principal stress direction. Obtain a series of stress and strain field data and crack opening displacement data that vary with loading, draft, wave height, wave direction, period, and crack state.

[0042] S400: For each most vulnerable hot spot location, a fatigue monitoring system is correspondingly set up to obtain the stress and strain field distribution in the area near the most vulnerable hot spot location during the actual operation of the semi-submersible platform and the crack opening displacement data after cracks occur. Specifically, for the screened fatigue vulnerable areas, install a fatigue monitoring system to obtain the surface stress and strain field and crack tip opening displacement data in the key areas during the actual operation of the semi-submersible platform.

[0043] In this embodiment, please refer to Figure 2 and Figure 3 As shown, the fatigue monitoring system includes a surface strain monitoring module and a crack tip opening displacement monitoring module. The surface strain monitoring module is used to monitor the surface stress and strain field in the area of the most vulnerable hot spot location, and the crack tip opening displacement monitoring module is used to monitor the surface crack tip opening displacement data in the area of the most vulnerable hot spot location. Further, the surface strain monitoring module includes several groups of strain gauges 100 and a first data transmission unit. The several groups of strain gauges 100 are arranged to cover the area of the most vulnerable hot spot location, and the several groups of strain gauges are communicatively connected to the first data transmission unit. The crack tip opening displacement monitoring module includes a displacement sensor 400 and a second data transmission unit. The displacement sensor 400 is communicatively connected to the second data transmission unit. The displacement sensor 400 has two monitoring foot points, and the two monitoring foot points straddle the area of the most vulnerable hot spot location. The fatigue monitoring system further includes a data integration and analysis module and a data acquisition device 200. The first data transmission unit and the second data transmission unit are both communicatively connected to the data acquisition device 200, and the data integration and analysis module is communicatively connected to the data acquisition device 200.

[0044] Specifically, the following solution is exemplarily given in this embodiment: For the fatigue vulnerable areas screened out in S200, several groups of strain gauges 100 are used for coverage. In the plate thickness direction of the bracket, at least three groups of strain gauges 100 are arranged, and adjacent two groups of strain gauges 100 are arranged staggeredly to ensure that cracks in the bracket thickness direction will surely be covered by one of the groups of strain gauges 100. Along one surface of the bracket, a sufficient number of groups of strain gauges 100 should also be arranged, covering all areas within 30% of the maximum fatigue damage, and at least not less than 3 groups. Each group still needs to be arranged staggeredly to ensure that cracks expanding in any direction can be captured. At the same time, on the other surface of the bracket, a close-fitting displacement sensor 400 is arranged. The two monitoring foot points of the displacement sensor 400 need to span the entire screened fatigue vulnerable area to ensure that after cracks appear, they are still within the range of the displacement sensor 400. Then, several groups of strain gauges 100 and the displacement sensor 400 are both communicatively connected to the data acquisition device 200 and transmitted to the data integration and analysis module in the semi-submersible platform through the wireless transmission device 300. The data integration and analysis module can be a high-speed processing computer.

[0045] Optionally, in order to improve the protection effect and safety performance of the fatigue monitoring system, the fatigue monitoring system further includes a wave protection device, and the wave protection device covers the surface strain monitoring module and the crack tip opening displacement monitoring module. The wave protection device is a device that needs to protect the equipment from damage under high-intensity slamming loads. It can adopt two forms: rigid protection and flexible protection. Considering the cost, the steel structure protective cover welded at a specific position has a lower cost and higher safety, and this kind of rigid protection device is usually adopted.

[0046] S500: Compare and evaluate the stress-strain field in the area near the most vulnerable hot spot position obtained with the fatigue screening benchmark. Specifically, through the high-speed processing computer and the analysis program, the stress-strain field and the crack tip opening displacement data at the most vulnerable hot spot position transmitted to the data integration and analysis module are compared in real time. The comparison content is the strain data at the positions of all strain gauges 100 and the opening displacement data within the range of the displacement sensor 400.

[0047] S600: If the stress-strain field in the area near the most vulnerable hot spot location obtained exceeds the fatigue screening criterion, predict the remaining life under specific operating conditions; if the stress-strain field in the area near the most vulnerable hot spot location obtained does not exceed the fatigue screening criterion, the fatigue monitoring system continues to monitor. Specifically, for all the data in S500, based on the database results under the same loading, draft and environmental conditions, analyze and fit the data of each data point through data processing methods such as the least variance method or the correlation coefficient method to determine the structure state corresponding to the closest strain field distribution and crack opening displacement data, so as to judge whether there is a crack. When there is a crack, determine the crack length according to the crack tip displacement, and determine the crack direction according to the strain field near the crack tip. If there is no crack, continue to monitor and the platform continues to operate.

[0048] It should be noted that if there is a crack, the remaining fatigue life is predicted based on the current environmental data of the semi-submersible platform and the current crack information. This prediction is based on two premises, one is to continue in-situ operation, and the other is to return to port for maintenance in advance. If continuing in-situ operation, the remaining crack growth can be predicted based on the wave time history data of the semi-submersible platform's previous operations, the current crack length in the selected vulnerable area, and the stress transfer function for subsequent crack growth, based on the modified Wheeler model. At the same time, at each step of crack growth, the prediction model is corrected in real time according to the stress data measured by the fatigue monitoring system, so as to accurately judge the time for continuing operation. If it is decided to return to port for maintenance in advance, the environmental data of the next expected navigation area is used as a reference, combined with the stress transfer function and the modified Wheeler model, to predict the remaining fatigue life. In life assessment, if the predicted remaining life does not meet the next operating requirements, adjust the loading of the semi-submersible platform by comparing the current environmental conditions in the database, and adjust the ballast water in the direction with a smaller stress transfer function for the fatigue hot spot area, so as to reduce the hot spot stress level and increase the remaining fatigue life.

[0049] Obviously, the above-mentioned embodiments of the present invention are merely examples for clearly explaining the present invention, and are not intended to limit the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A method for evaluating the fatigue strength of a semi-submersible platform, characterized in that, Including: S100: Design and screen out the extreme working conditions that cause the highest fatigue damage rate of the semi-submersible platform to be evaluated under various different operating conditions; S200: For each of the screened design extreme working conditions, calculate the fatigue damage rate at the key connection structures, and determine the most vulnerable hot spot positions corresponding to each of the design extreme working conditions; S300: For each of the most vulnerable hot spot positions, according to the different operating conditions of the semi-submersible platform to be evaluated, calculate the stress and strain field distributions in the areas near the crack propagation direction under different crack lengths and directions, so as to form the maximum stress and strain under different crack lengths, and the opening displacement limit value as the fatigue screening criterion; S400: For each of the most vulnerable hot spot positions, a fatigue monitoring system is correspondingly set up to obtain the stress and strain field distribution in the area near the most vulnerable hot spot position of the semi-submersible platform during actual operation and the crack opening displacement data after cracks occur; S500: Compare and evaluate the stress and strain field in the area near the obtained most vulnerable hot spot position with the fatigue screening criterion.

2. The fatigue strength assessment method of the semi-submersible platform according to claim 1, characterized in that After S500, the semi-submersible platform fatigue strength evaluation method further includes: S600: If the stress and strain field in the area near the obtained most vulnerable hot spot position exceeds the fatigue screening criterion, predict the remaining life under specific operating conditions; if the stress and strain field in the area near the obtained most vulnerable hot spot position does not exceed the fatigue screening criterion, the fatigue monitoring system continues to monitor.

3. The fatigue strength assessment method of the semi-submersible platform according to claim 1, characterized in that In S400, the fatigue monitoring system includes a surface strain monitoring module and a crack tip opening displacement monitoring module. The surface strain monitoring module is used to monitor the surface stress and strain field in the area of the most vulnerable hot spot position, and the crack tip opening displacement monitoring module is used to monitor the crack tip opening displacement data on the surface in the area of the most vulnerable hot spot position.

4. The fatigue strength assessment method of the semi-submersible platform according to claim 3, characterized in that The surface strain monitoring module includes several groups of strain gauges (100). Several groups of the strain gauges (100) are arranged in a covering manner in the area of the most vulnerable hot spot position. The crack tip opening displacement monitoring module includes a displacement sensor (400). The displacement sensor (400) has two monitoring foot points. The two monitoring foot points straddle the area of the most vulnerable hot spot position. The fatigue monitoring system further includes a data integration and analysis module and a data acquisition device (200). The data acquisition device (200) is used to receive the data monitored by several groups of the strain gauges (100) and the displacement sensor (400). The data integration and analysis module is communicatively connected to the data acquisition device (200).

5. The fatigue strength assessment method for the semi-submersible platform according to claim 4, wherein The surface strain monitoring module further includes a first data transmission unit. Several groups of the strain gauges (100) are communicatively connected to the first data transmission unit. The crack tip opening displacement monitoring module further includes a second data transmission unit. The displacement sensor (400) is communicatively connected to the second data transmission unit. Both the first data transmission unit and the second data transmission unit are communicatively connected to the data acquisition device (200).

6. The fatigue strength assessment method of the semi-submersible platform according to claim 4, characterized in that Two adjacent groups of the strain gauges (100) are arranged staggeredly.

7. The fatigue strength assessment method of the semi-submersible platform according to claim 3, wherein The fatigue monitoring system further includes a wave protection device, and the wave protection device covers the surface strain monitoring module and the crack tip opening displacement monitoring module.

8. The fatigue strength assessment method for a semi-submersible platform according to any one of claims 1-7, characterized in that, In S200, fatigue scans are respectively performed on the critical connection structures according to the environmental conditions corresponding to the navigation conditions and operation conditions, as well as different operation drafts, so as to screen and determine the most vulnerable hot spot positions.

9. The fatigue strength assessment method for a semi-submersible platform according to claim 8, characterized in that The positions of the fatigue scans at least include the moonpool and the corner of the cabin, the connection nodes of the column and the deck box, the connection nodes of the column and the cross brace, and the connection nodes of the column and the lower floating body.

10. The fatigue strength assessment method for a semi-submersible platform according to any one of claims 1-7, characterized in that, In S300, a high-fidelity digital model is adopted to calculate the stress and strain field distributions in the regions near the crack propagation directions at different crack lengths and directions of each of the most vulnerable hot spot positions according to the platform loading, operation environment, and preset crack sizes.

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