Simplified calculation method for bearing capacity of single-point mooring bearing considering mounting structure

Abstract

The invention provides a simplified calculation method for the bearing capacity of a single-point mooring bearing considering an installation structure, and belongs to the technical field of single-point mooring systems.The method includes the steps that a finite element model of a single-point mooring turntable bearing and the installation structure of the single-point mooring turntable bearing is established, load distribution calculation is conducted, and then the load distribution condition of a rolling body is obtained; when simplified modeling is carried out on the turntable bearing of the single-point mooring system, bolts are replaced by beam units, and rollers are replaced by nonlinear springs. According to the simplification method disclosed by the invention, the number of grids is reduced, the contact problem of the roller and the raceway is simplified, the problems of non-convergence of calculation and overlong calculation time are effectively avoided, and a load distribution result can be quickly obtained. In addition, when the bearing capacity of the turntable bearing is calculated, the elastic deformation of the mounting structure is fully considered, the result is closer to the actual working condition, and the accuracy of bearing capacity calculation can be effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of single-point mooring systems, and in particular relates to a simplified calculation method for the bearing capacity of a single-point mooring bearing considering the installation structure. Background Art

[0002] With the development of marine resources and the rapid development of offshore equipment such as FPSOs (Floating Production Storage and Offloading units) and ultra-large oil tankers, single-point mooring systems have become one of the important mooring methods at sea. In this system, large turntable bearings, as key components for bearing the mooring forces of FPSOs and oil tankers, directly affect the safe and stable operation of the entire system. However, due to their harsh working environment and difficulties in maintenance and replacement, failures of turntable bearings seriously affect the normal operation of the system. Therefore, how to accurately calculate the bearing capacity of turntable bearings, especially in complex marine environments, has become a key issue for ensuring the safe operation of single-point mooring systems.

[0003] Turntable bearings need to simultaneously bear the combined action of axial loads, radial loads, and overturning moments under low-speed and heavy-load conditions. To meet the requirements of this working condition, three-row cylindrical roller bearings have become a common choice in such systems due to their high bearing capacity. Existing research mostly derives the maximum contact load formula of the bearing through mechanical modeling, usually based on the assumption of the rigidity of the bearing rings and the Hertz contact theory between the rollers and the rings. However, there is a certain gap between this idealized model and the actual working conditions, resulting in insufficient accuracy of the calculation results.

[0004] At the same time, finite element numerical simulation is an effective method for calculating the bearing capacity of complex structures. However, for three-row cylindrical roller bearings, their structural dimensions are large, the number of rolling elements is large, and the contact problems between the rolling elements and the rings are extremely complex. Establishing a full-scale finite element model not only requires refined treatment of the contact between the rollers and the rings, with a huge amount of mesh division, but also has a large amount of calculation, prone to problems such as too long calculation time or even difficulty in convergence, resulting in waste of calculation resources and inaccuracy of the results.

[0005] In addition, many studies only consider axial forces and overturning moments in the analysis, ignoring radial forces. However, in single-point mooring systems, the radial forces generated by the actions of wind, waves, and currents and the mooring forces of FPSOs or oil tankers cannot be ignored. Ignoring the calculation of radial forces will not be able to truly reflect the stress state of the turntable bearing. At the same time, most studies ignore the influence of bolts during the modeling process, or use solid bolt models for simplified treatment, which cannot accurately reflect the influence of bolt connections on the overall bearing capacity of the bearing.

[0006] Finally, existing calculation methods usually simplify the forces on the slewing bearing into equivalent calculations of axial load, radial load, and overturning moment. Although the calculation process is simplified, the influence of the deformation of the installation structure on the bearing load-bearing condition is not considered, resulting in insufficient accuracy of the calculation results.

[0007] Therefore, in view of the problems in the prior art such as ignoring the bearing capacity influence of bolts and radial rollers, there is an urgent need for a simplified calculation method that can consider the influence of the deformation of the installation structure to improve the accuracy and efficiency of the bearing capacity calculation of the slewing bearing in the single-point mooring system. Summary of the Invention

[0008] The problem to be solved by the present invention is to provide a simplified calculation method for the bearing capacity of a single-point mooring bearing considering the installation structure.

[0009] To solve the above technical problems, the technical solution adopted by the present invention is: a simplified calculation method for the bearing capacity of a single-point mooring bearing considering the installation structure, including the following steps: S1. Respectively establish finite element models of the main thrust rollers, radial rollers, and auxiliary thrust rollers in contact with the raceway, obtain the displacement amounts of the main thrust rollers, radial rollers, and auxiliary thrust rollers under different loads, and further obtain the nonlinear spring stiffnesses used to replace the main thrust rollers, radial rollers, and auxiliary thrust rollers; S2. Establish a geometric model of the slewing bearing of the single-point mooring system, after meshing, import the mesh model into finite element analysis software, perform assembly, and assign attributes to obtain a finite element model of the slewing bearing of the single-point mooring system; S3. According to the nonlinear spring stiffness calculated in step S1, equivalently replace the main thrust rollers, radial rollers, and auxiliary thrust rollers with nonlinear springs; simplify and establish a rolling element model on the finite element model of the slewing bearing of the single-point mooring system obtained in step S2, and at the same time use beam elements to simulate the stress condition of the bolts; S4. Set boundary conditions and apply external loads in the rolling element model, perform simulation calculations; extract the load distribution conditions of various rollers under the action of external loads to obtain load data.

[0010] Further, in step S1, in the finite element analysis software, respectively establish finite element models of the main thrust rollers, radial rollers, and auxiliary thrust rollers in contact with the raceway, set the corresponding material parameters, and use the penalty function to define the friction formula for the contact property. The specific formula expression is: Among them, is the penalty function; is the penalty factor; is the element penetration depth; T is the vector transpose symbol; At the same time, in the way of hard contact, the top surfaces of the upper raceways of the main thrust roller, radial roller and auxiliary thrust roller are coupled with the center points of the top surfaces. The boundary condition is set as full constraint on the bottom surface of the lower raceway, and the displacement in the y-axis direction of the coupling points on the upper raceway is released. The load is applied at the coupling points in the form of a concentrated force, and the direction is downward along the y-axis. Subsequently, by gradually increasing the magnitude of the concentrated force, the displacements of the main thrust roller, radial roller and auxiliary thrust roller in the analysis results are extracted, so as to calculate the nonlinear spring stiffness of the three types of rollers.

[0011] Further, in step S2, the single-point mooring system turntable bearing includes a rotating casting, a fixed casting, bolts and a bearing ring. The fixed casting is of an annular structure and is located inside the rotating casting and connected to the inner ring of the rotating casting. The bearing ring includes a main bearing outer ring and a main bearing inner ring. The main bearing outer ring is installed and fixed on the rotating casting through bolts, and the main bearing inner ring is installed and fixed on the fixed casting through bolts.

[0012] Further, in step S2, a corresponding geometric model is established according to the structural dimensions of the single-point mooring system turntable bearing, and the geometric model is processed by using the mesh generation function. When generating the mesh, a hexahedral mesh combined with some tetrahedral meshes is selected for processing. After the mesh generation is completed, the mesh model is imported into the finite element analysis software. Subsequently, material properties are assigned to each component and overall assembly is carried out.

[0013] Further, in step S3, the main thrust roller, radial roller and auxiliary thrust roller are simplified. They are respectively simplified into 6, 5 and 5 nonlinear springs. Combining with the nonlinear spring stiffness values calculated in step S1, they are respectively divided by the corresponding number of springs to calculate the nonlinear stiffness of each spring. At the same time, to simulate the bolts, a three-dimensional line element is established and beam element properties are assigned to it. The cross-section of the beam element is selected as circular to replace the actual real bolts. To more accurately simulate the interaction between the bolts and the bearing ring, the vertices of the beam element are coupled with the surrounding nodes by multi-point constraint, and a pre-tightening force is applied to the beam element to ensure that the mechanical behavior of the model conforms to the actual engineering situation.

[0014] Further, in step S4, when applying the load, the mounting point of the rotating casting is coupled and constrained with the reference point, and the vertical mooring force and horizontal mooring force borne by the single-point mooring system turntable bearing are concentratedly applied at the coupling point. The boundary condition is full constraint on the inner surface of the fixed casting and three-degree-of-freedom constraint is applied to the coupling point.

[0015] Due to the adoption of the above technical solutions, the present invention has the following beneficial effects: When simplifying the modeling of the swivel bearing of the single-point mooring system in the present invention, bolts are replaced by beam elements, and rollers are replaced by non-linear springs. In particular, considering that the radial force borne by the main bearing in the single-point mooring system is large and cannot be ignored, the load-bearing situation of the radial rollers is added during the modeling process. The simplification method of the present invention not only reduces the number of meshes, simplifies the contact problem between the rollers and the raceways, but also effectively avoids the problems of non-convergent calculation and excessive calculation time, and can quickly obtain the load distribution results.

[0016] When calculating the load-bearing capacity of the swivel bearing in the present invention, the elastic deformation of the installation structure is fully considered. By directly applying the load of the swivel bearing to the installation structure, the load distribution of the swivel bearing under actual working conditions can be accurately reflected. Compared with the equivalent calculation method that does not consider the installation structure, the results of this method are closer to the actual working conditions and can effectively improve the accuracy of the bearing capacity calculation. Description of the Drawings

[0017] The present invention will be specifically described below with reference to the drawings and in combination with examples. The advantages and implementation methods of the present invention will become more obvious. The content shown in the drawings is only used for the explanation of the present invention and does not constitute any limitation to the present invention. In the drawings: Figure 1 It is a finite element model diagram of a single roller and a raceway of the present invention.

[0018] Figure 2 It is a load diagram of the main push roller, radial roller and auxiliary push roller of the present invention.

[0019] Figure 3 It is a structural schematic diagram of the swivel bearing of the single-point mooring system of the present invention.

[0020] Figure 4 It is a simplified schematic diagram of the non-linear spring and beam element of the present invention.

[0021] Figure 5 It is a finite element model diagram of the swivel bearing and installation structure of the single-point mooring system of the present invention.

[0022] Figure 6 It is a schematic diagram of load application of the overall simplified model and traditional simplified model of the present invention.

[0023] Figure 7 It is a finite element model diagram of the traditional simplified model.

[0024] Figure 8 It is a comparison diagram of the load distribution between the traditional simplified model and the theoretical model.

[0025] Figure 9 It is a comparison diagram of the load distribution between the simplified model considering the installation structure of the present invention and the traditional simplified model.

[0026] Figure 10 This is the displacement comparison diagram of the simplified installation structure model and the traditional simplified model considered in the present invention.

[0027] In the figure: 1. Rotating casting; 2. Fixed casting; 3. Bolt; 4. Outer ring of main bearing; 5. Inner ring of main bearing; 8. Nonlinear spring; 9. Beam element; A. Loading point of overall simplified model; B. Loading point of traditional simplified model. Specific implementation manner

[0028] As Figures 1 to 10 shown, a simplified calculation method for the bearing capacity of a single-point mooring bearing considering the installation structure in the present invention includes the following steps: S1. Respectively establish finite element models of the main thrust roller, radial roller, and auxiliary thrust roller in contact with the raceway in a finite element analysis software, obtain the displacement amounts of the main thrust roller, radial roller, and auxiliary thrust roller under different loads, and further obtain the nonlinear spring stiffnesses for replacing the main thrust roller, radial roller, and auxiliary thrust roller.

[0029] Among them, the diameter of the main thrust roller is 40 mm and the length is 30 mm; the diameter of the radial roller is 50 mm and the length is 35 mm; the diameter of the auxiliary thrust roller is 30 mm and the length is 25 mm.

[0030] Specifically, as Figure 1 shown, in the finite element analysis software, respectively establish finite element models of the main thrust roller, radial roller, and auxiliary thrust roller in contact with the raceway, set the corresponding material parameters, and the elastic modulus in the material parameters, and the Poisson's ratio , and the contact property adopts the penalty function to define the friction formula, and its specific formula expression is: Among them, is the penalty function; is the penalty factor; is the unit implantation depth.

[0031] Here, the friction coefficient is selected as 0.2, and at the same time, the hard contact method is adopted. Couple the top surface center points of the upper raceways of the main thrust roller, radial roller, and auxiliary thrust roller, set the boundary condition as full constraint of the bottom surface of the lower raceway, release the displacement in the y-axis direction of the coupled points on the upper raceway, and apply the load in the form of a concentrated force at the coupled points, with the direction along the y-axis downward. Subsequently, by gradually increasing the magnitude of the concentrated force, extract the displacements of the main thrust roller, radial roller, and auxiliary thrust roller in the analysis results, so as to calculate the nonlinear spring stiffnesses of the three types of rollers, as Figure 2 shown.

[0032] S2. According to the structural form and dimensional characteristics of the swivel bearing of the single point mooring system, establish the geometric model of the swivel bearing, and import it into the finite element preprocessing software for refined mesh division; subsequently, import the mesh model into the finite element analysis software, and endow the mesh model with necessary conditions such as material properties and contact characteristics to obtain the finite element model of the swivel bearing of the single point mooring system.

[0033] Specifically, as Figure 3 shown, the swivel bearing of the single point mooring system includes a rotating casting 1, a fixed casting 2, bolts 3 and a bearing ring. The fixed casting 2 is of an annular structure, which is located inside the rotating casting 1 and is connected to the inner ring of the rotating casting 1. The bearing ring includes a main bearing outer ring 4 and a main bearing inner ring 5. The main bearing outer ring 4 is installed and fixed on the rotating casting 1 through bolts 3, and the main bearing inner ring 5 is installed and fixed on the fixed casting 2 through bolts 3.

[0034] Establish the corresponding geometric model in Solidworks according to the structural dimensions of the swivel bearing of the single point mooring system. Considering that the calculation accuracy of the finite element model depends to a large extent on the precise division of the mesh, the powerful mesh division function of Hypermesh software is used to process the geometric model in this invention. The mesh type has an important influence on the accuracy of the calculation results. When dividing the mesh, hexahedral meshes combined with some tetrahedral meshes are selected for processing, and the number and size of the meshes at the bolt holes of the bolts 3 and the raceway surface are strictly controlled to ensure the calculation accuracy. After the mesh division is completed, the mesh model is imported into the finite element analysis software ABAQUS. Subsequently, in ABAQUS, material properties are assigned to each component, and overall assembly is carried out in ABAQUS to ensure the accuracy and operability of the model. The material properties are: the material is 42CrMo; the elastic modulus E is 206 GPa; the Poisson's ratio μ is 0.3; the pitch circle diameter of the main thrust rollers is 3600 mm; the pitch circle diameter of the radial rollers is 3400 mm; the pitch circle diameter of the auxiliary thrust rollers is 3500 mm.

[0035] S3. According to the nonlinear spring stiffness calculated in step S1, the main thrust rollers, radial rollers and auxiliary thrust rollers are all equivalent to nonlinear springs 8; by writing Python scripts, a rolling element model is simply established on the finite element model of the swivel bearing of the single point mooring system, and at the same time, the force condition of the bolts is simulated by beam elements 9.

[0036] Specifically, as Figure 4As shown, the main thrust roller, radial roller, and auxiliary thrust roller are simplified. They are respectively simplified to 6, 5, and 5 non-linear springs 8. Combining with the non-linear spring stiffness values calculated in step S1, divide them by the corresponding number of springs respectively to calculate the non-linear stiffness of each spring. Since there are a large number of non-linear springs 8 in the simplified model, in order to improve efficiency, the present invention batch builds non-linear springs 8 based on the Python language through self-written scripts, and modifies the spring stiffness parameters in the inp file to ensure that the springs are only compressed and not stretched, thus conforming to the load-bearing characteristics of the actual rollers.

[0037] Meanwhile, to simulate the role of the bolt, a three-dimensional line element is established and given the properties of a beam element. The cross-section of the beam element 9 is selected as circular with a radius of 210 mm to replace the actual real bolt. To more accurately simulate the interaction between the bolt and the bearing race, as Figure 4 shown, the vertices of the beam element 9 are batch coupled with the surrounding nodes by using a script for MPC (multi-point constraint), and a pre-tightening force is applied to the beam element 9 to ensure that the mechanical behavior of the model conforms to the actual engineering situation.

[0038] S4. As Figure 5 shown, set boundary conditions and apply external loads in the rolling element model for simulation calculation; extract the load distribution of various rollers under the action of external loads through a script to obtain accurate load data.

[0039] Specifically, in order to more accurately simulate the working state of the single-point mooring system turntable bearing in engineering practice, in this embodiment, when applying loads, the mounting position of the rotating casting 1 is coupled and constrained with the reference point, and the vertical mooring force and horizontal mooring force borne by the single-point mooring system turntable bearing are concentratedly applied at the coupling point. The vertical mooring force is 2000 KN, and the horizontal mooring force is 2001 KN. The load application position is as shown at Figure 6 A in. The boundary conditions are full constraint of the inner surface of the fixed casting 2 and constraint of three degrees of freedom at the coupling point (U3 = UR1 = UR2 = 0).

[0040] Subsequently, simulation calculation can be carried out, and the finite element calculation results can be obtained. Since the main thrust roller and radial roller are the main load-bearing structures, extract the load distribution curves of the main thrust roller and radial roller.

[0041] In order to verify the accuracy of the proposed simplified model and verify that the simplified calculation model considering the installation structure proposed by the present invention is more in line with the actual situation, this embodiment establishes two other calculation models. One is the finite element simplified model of the single-point mooring turntable bearing considering the installation structure, denoted as the traditional simplified model; the other is the theoretical calculation model of the turntable bearing without considering the installation structure, denoted as the theoretical model.

[0042] The establishment of the traditional simplified model is the same as the modeling method under the above-mentioned considered installation structure, except that the rotating casting 1 and the fixed casting 2 are not established. The finite element model is as follows Figure 7 , including the traditional outer ring of the main bearing and the traditional inner ring of the main bearing. In terms of the load application method, the axial mooring force and the radial mooring force received by the single-point mooring swivel bearing are equivalent to the traditional axial load , the traditional radial load and the traditional overturning moment M. The calculation formula of the traditional overturning moment M is as follows: Subsequently, the outer surface of the traditional outer ring of the main bearing is coupled with the geometric center of the main bearing, and the calculated traditional radial load and overturning are applied to this reference point. The traditional axial load is applied to the upper surface of the traditional outer ring of the single-point mooring swivel bearing. The load application schematic diagram is as shown in Figure 6 at B. The boundary conditions are applied as full constraints on the inner surface of the traditional inner ring of the main bearing and three degrees of freedom constraints (U3 = UR1 = UR2 = 0) are applied to the coupling point.

[0043] The calculation of the theoretical model first represents the position of each row of rollers (theoretical main thrust rollers, theoretical radial rollers, and theoretical auxiliary thrust rollers) in polar coordinates in the swivel bearing: Among them, is the position angle of the roller; Z is the number of rollers, i is the roller number.

[0044] The force balance calculation of the theoretical radial rollers is as follows: The deformation of the i-th theoretical radial roller in the normal contact is: Among them, is the overall radial displacement of the swivel bearing; is the position angle of the i-th theoretical radial roller.

[0045] The load borne by the i-th theoretical radial roller at any position is: Among them, is the contact stiffness between the theoretical radial roller and the raceway surface; The calculation formula of Among them, is the length of the theoretical radial roller.

[0046] The radial load borne by the slewing bearing is in force balance with the load borne by the roller: Among them, is the number of theoretical radial rollers.

[0047] The force balance calculation of the theoretical main thrust roller and the theoretical auxiliary thrust roller is as follows: The upper and lower rows of rolling elements of the three-row cylindrical roller bearing are subjected to the combined action of axial load and overturning moment. The outer ring of the slewing bearing will generate an overall displacement and a rotation angle along the axial direction. Therefore, the deformations of the i-th theoretical main thrust roller and the j-th theoretical auxiliary thrust roller in the normal contact can be calculated as and , and the calculation formula is as follows: Among them, is the distribution circle diameter of the theoretical main thrust roller, is the distribution circle diameter of the theoretical auxiliary thrust roller, is the angular displacement of the inner ring of the slewing bearing, is the distribution angle of the i-th main thrust roller, is the distribution angle of the j-th auxiliary thrust roller.

[0048] The load borne by the i-th theoretical main thrust roller at any position and the load borne by the j-th theoretical auxiliary thrust roller are respectively: Among them, is the contact stiffness between the theoretical main thrust roller and the raceway surface; is the contact stiffness between the theoretical auxiliary thrust roller and the raceway surface, is the overall axial displacement of the slewing bearing.

[0049] Among them, is the length of the theoretical main thrust roller; is the length of the theoretical auxiliary thrust roller.

[0050] The balance of the slewing bearing in the axial direction is the axial load and the overturning moment And through the force balance of the theoretical main pushing roller and the theoretical auxiliary pushing roller bearing the load, the following equilibrium equations are obtained: Wherein, is the number of theoretical auxiliary pushing rollers, is the number of theoretical main pushing rollers.

[0051] Subsequently, taking , and as iteration parameters, input the equivalent axial load , radial load and tipping moment , and perform iterative solution on the three equilibrium equations. Thus, the load borne by each roller of the theoretical main pushing roller, theoretical radial roller and theoretical auxiliary pushing roller is obtained.

[0052] Through the above process, the load distribution curves of the three types of rollers of the traditional simplified model and the theoretical model are obtained respectively, and the load distribution curves of the main pushing roller and the auxiliary pushing roller calculated by the traditional simplified model and the theoretical model are compared.

[0053] As Figure 8 shown, it can be seen from the figure that the load distribution curves calculated by the two models are very close and the error is extremely small. At the same time, the comparison of the maximum load errors of various rollers between the traditional simplified model and the theoretical model is listed, as shown in Table 1. Therefore, through the comparative analysis of the traditional simplified model and the theoretical model, it can be proved that the accuracy of the simplified model established by simplifying the use of the nonlinear spring 8 and the beam element 9 without considering the installation structure.

[0054] Table 1 Comparison of the maximum load errors of various rollers between the traditional simplified model and the theoretical model

[0055] After verifying the accuracy of the simplified bolt modeling method using the nonlinear spring 8 and the beam element 9, a further comparative analysis is carried out between the traditional finite element model and the calculation model considering the installation structure.

[0056] Since the main pushing roller and the radial roller are the main load-bearing components of the single-point mooring bearing, the results obtained from the simplified calculation model considering the installation structure in step S4 are processed, and the load distribution curves of the two types of rollers are extracted. Subsequently, the load distribution results of the two models are compared, and the results are as Figure 9 shown. From Figure 9As can be seen from Fig. (a), in terms of the main thrust roller, the model considering the installation structure shows a more concentrated load distribution. In particular, the rollers near the mounting point bear a larger load, and their maximum load is also significantly greater than that of the traditional simplified calculation method. And in Figure 9 in terms of the radial rollers in Fig. (b), although the maximum bearing loads of the two are not much different, the overall load distribution is more significant in the model considering the installation structure.

[0057] Regarding the overall deformation of the traditional simplified model and the model considering the installation structure, as Figure 10 shown. It can be observed that in the calculation model considering the installation structure, the displacement of the slewing bearing is more biased towards the mounting side, while the displacement change of the traditional structure is relatively gentle. At the same time, the overall displacement of the calculation model considering the installation structure reaches 2.372 mm, which is much larger than 0.1227 mm of the traditional simplified model. This is because in the model considering the installation structure, the load is directly applied at the mounting point, resulting in a relatively large displacement on the mounting side.

[0058] The traditional simplified calculation method simply considers the installation structure as a rigid structure, and then directly equivalent the mooring force exerted by the soft and rigid arm hook in the single point mooring system on the rotating casting to the axial load, radial load and overturning moment acting at the geometric center of the slewing bearing. However, such a calculation method does not conform to the actual stress situation of the structure. Therefore, considering the elastic deformation of the installation structure and the connection of bolts will directly affect the force transmission and deformation of the overall structure, resulting in the load distribution of the main thrust roller being concentrated near the mounting side, and at the same time, the calculated maximum bearing load of the main thrust roller is greater than the traditional calculation method. So the calculation model proposed by the present invention based on considering the installation structure is more in line with the actual situation, and at the same time, the calculated bearing load distribution and overall displacement situation are more in line with the force form of the slewing bearing of the single point mooring system.

[0059] So far, the present invention has proposed an effective bearing capacity calculation method through the simplified modeling of the slewing bearing of the single point mooring system. This method uses beam elements to simulate bolts and nonlinear spring 8 to replace rollers. In particular, it considers the large radial force borne by the main bearing under complex working conditions, filling the gap in the prior art that ignores the radial force. Through this simplified modeling method, not only the number of meshes is effectively reduced, the contact problem between the roller and the raceway is simplified, but also the situation of too long calculation time and non-convergence in the traditional method is avoided, and the load distribution results can be obtained quickly and accurately.

[0060] Different from the traditional simplified calculation method that only regards the installation structure as a rigid structure, the present invention fully considers the elastic deformation of the installation structure and the influence of bolt connection. By accurately simulating these factors, the present invention finds that the load distribution of the main thrust roller is more concentrated near the mounting side, and the calculated maximum bearing capacity of the main thrust roller is larger compared with the traditional method. The load distribution and overall displacement provided by this method are more consistent with the actual stress conditions of the slewing bearing of the single-point mooring system, significantly improving the accuracy and reliability of the calculation results.

[0061] The embodiments of the present invention have been described in detail above, but the above content is only the preferred embodiments of the present invention and cannot be considered as limiting the scope of implementation of the present invention. Any equivalent changes and improvements made within the scope of the present invention should still fall within the scope covered by the present invention.

Claims

1. Simplified calculation method for the bearing capacity of a single-point mooring bearing considering the installation structure, characterized in that: The steps include the following: S1. Respectively establish finite element models of the main thrust roller, radial roller and auxiliary thrust roller in contact with the raceway, obtain the displacements of the main thrust roller, radial roller and auxiliary thrust roller under different loads, and then obtain the non-linear spring stiffness for replacing the main thrust roller, radial roller and auxiliary thrust roller; S2. Establish a geometric model of the swivel bearing of the single point mooring system, after mesh generation, import the mesh model into the finite element analysis software, perform assembly, and assign attributes to obtain the finite element model of the swivel bearing of the single point mooring system; S3. According to the non-linear spring stiffness calculated in step S1, equivalently replace the main thrust roller, radial roller and auxiliary thrust roller with non-linear springs; simplify and establish a rolling element model on the finite element model of the swivel bearing of the single point mooring system obtained in step S2, and at the same time use beam elements to simulate the stress condition of the bolts; S4. Set boundary conditions and apply external loads in the rolling element model, perform simulation calculations; extract the load distribution of various rollers under the action of external loads to obtain load data.

2. The simplified calculation method for the bearing capacity of a single-point mooring bearing considering the installation structure according to claim 1, characterized in that: In step S1, in the finite element analysis software, respectively establish finite element models of the main thrust roller, radial roller and auxiliary thrust roller in contact with the raceway, set the corresponding material parameters, and use the penalty function to define the friction formula for the contact property. The specific formula expression is: Among them, is the penalty function; is the penalty factor; is the unit implantation depth; At the same time, in the way of hard contact, couple the top surface of the upper raceway of the main thrust roller, radial roller and auxiliary thrust roller with the center point of the top surface. Set the boundary condition that the bottom surface of the lower raceway is fully constrained, release the displacement in the y-axis direction of the coupled point on the upper raceway, apply the load in the form of a concentrated force at the coupled point, and the direction is downward along the y-axis. Then, by gradually increasing the magnitude of the concentrated force, extract the displacements of the main thrust roller, radial roller and auxiliary thrust roller in the analysis results, and calculate the non-linear spring stiffness of the main thrust roller, radial roller and auxiliary thrust roller.

3. The simplified calculation method for the bearing capacity of the single-point mooring bearing considering the installation structure according to claim 2, wherein: In step S2, the swivel bearing of the single point mooring system includes a rotating casting, a fixed casting, bolts and a bearing ring. The fixed casting is a ring structure, the fixed casting is located inside the rotating casting and is connected to the inner ring of the rotating casting. The bearing ring includes a main bearing outer ring and a main bearing inner ring. The main bearing outer ring is installed and fixed on the rotating casting through bolts, and the main bearing inner ring is installed and fixed on the fixed casting through bolts.

4. The simplified calculation method for the bearing capacity of a single-point mooring bearing considering the installation structure according to claim 3, characterized in that: In step S2, establish a corresponding geometric model according to the structural dimensions of the swivel bearing of the single point mooring system, use the mesh generation function to process the geometric model. When generating the mesh, select hexahedral meshes combined with some tetrahedral meshes for processing. After the mesh generation is completed, import the mesh model into the finite element analysis software, and then assign material properties to each component and perform overall assembly.

5. The simplified calculation method for the bearing capacity of the single-point mooring bearing considering the installation structure according to claim 4, characterized in that: In step S3, simplify the main thrust roller, radial roller, and auxiliary thrust roller, and simplify them into 6, 5, and 5 non-linear springs respectively. Combining with the non-linear spring stiffness values calculated in step S1, divide them by the corresponding number of springs respectively to calculate the non-linear stiffness of each spring. At the same time, to simulate the bolt, establish a three-dimensional line element and endow it with beam element properties. The cross-section of the beam element is selected as circular to replace the actual bolt. Couple the vertices of the beam element with the surrounding nodes, and apply a pre-tightening force to the beam element.

6. The simplified calculation method for the bearing capacity of a single-point mooring bearing considering the installation structure according to claim 5, characterized in that: In step S4, when applying the load, couple and constrain the mounting point of the rotating casting with the reference point, and concentrate and apply the vertical mooring force and horizontal mooring force borne by the turntable bearing of the single point mooring system to the coupling point. The boundary conditions are full constraint on the inner surface of the fixed casting and three-degree-of-freedom constraint on the coupling point.

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