A method for checking the stress concentration of the relief groove of the slewing bearing nose ring of an offshore crane

Abstract

A method for stress concentration checking of the relief groove of the slewing bearing nose ring of an offshore crane, the method includes establishing a finite element model of the slewing bearing nose ring based on a computer, establishing a non-linear contact model, checking the contact strength of the nose ring mesh model, designing and checking the corner of the relief groove, and checking the fatigue strength of the corner of the relief groove; in application, by establishing a rolling element model, a nose ring model and a corner model of the relief groove, and discretizing them into meshes to generate a mesh discrete model of the slewing bearing nose ring, then loading the load to obtain the stress at the corner of the local relief groove, then establishing a non-linear contact model between the rolling element mesh model and the nose ring mesh model, solving to obtain the contact stress, and comparing the contact stress, the stress at the corner of the relief groove with the allowable stress, and finally performing a fatigue life simulation on the nose ring model to complete the checking work. Therefore, the present invention not only has a relatively concentrated and accurate evaluation result, but also has a relatively accurate calculation result.

Description

Technical Field

[0001] The present invention relates to a checking method, belonging to the field of design and development of cranes for ships and offshore engineering equipment, and particularly to a method for checking stress concentration in the relief groove of the nose ring of the slewing bearing of an offshore crane. Background Art

[0002] The three-row roller slewing bearing is a kind of bearing that can bear the combined action of radial load, axial load and overturning load, and is a widely used slewing device for ship cranes and offshore crane devices; when the crane is working, the slewing bearing can bear the radial load, axial load and overturning moment transmitted from the tower body. Among them, the radial roller bearing bears the radial load, and the upper and lower row roller bearings bear the axial load and overturning moment. The tracks of the slewing ring beam in contact with the upper and lower rows of rollers bear almost all of the bearing load and overturning moment, and the stress concentration at the relief groove is often ignored or underestimated, thus affecting the structure life and reliability. Therefore, the reliability and safety of the slewing ring structure are particularly important; the traditional analysis methods mainly include theoretical calculation and finite element calculation. Although they can generally analyze the stress of the nose ring, they still have the following defects:

[0003] When performing theoretical calculation, the nose ring is simplified into a beam to calculate the stress of the structure, but the stress at the corner cannot be accurately evaluated. Therefore, only the method of stress concentration coefficient can be used to magnify the result, and the influence of the specifications and dimensions of the relief groove on the result cannot be specifically simulated, and the evaluation result is relatively broad and vague; while in the finite element method, the bending moment is generally directly applied to the nose ring, so the interaction between the rolling elements and the slewing ring cannot be simulated, and the calculated result is not very accurate.

[0004] Disclosing the information of this background art section is only intended to increase the understanding of the overall background of the present application, and should not be regarded as an admission or any form of suggestion that this information constitutes the prior art already known to those of ordinary skill in the art. Summary of the Invention

[0005] The purpose of the present invention is to overcome the defects and problems in the prior art that the evaluation result is relatively broad and vague, and the calculation result is inaccurate, and to provide a method for checking stress concentration in the relief groove of the nose ring of the slewing bearing of an offshore crane with a relatively concentrated and accurate evaluation result and a relatively accurate calculation result.

[0006] To achieve the above purpose, the technical solution of the present invention is: a method for checking stress concentration in the relief groove of the nose ring of the slewing bearing of an offshore crane, and the checking method includes the following steps:

[0007] Step 1: Establish a finite element model of the slewing bearing nose ring based on a computer;

[0008] The finite element model of the slewing bearing nose ring includes: a rolling element model, a nose ring model, and a model at the corner of the relief groove; then, the finite element model of the slewing bearing nose ring is discretized into a mesh to generate a meshed discrete model of the slewing bearing nose ring; the meshed discrete model of the slewing bearing nose ring includes a rolling element mesh model, a nose ring mesh model, and a mesh model at the corner of the relief groove; finally, a load is applied to the meshed discrete model of the slewing bearing nose ring to obtain the stress at the corner of the relief groove.

[0009] Step 2: Establish a non-linear contact model.

[0010] The method for establishing the non-linear contact model is as follows: establish a non-linear contact model between the rolling element mesh model and the nose ring mesh model; the non-linear contact model is a contact pair generated between each rolling element and the nose ring; the contact pair includes a target surface and a contact surface; the target surface is the rolling element, and the contact surface is the support track surface of the nose ring; then, perform a non-linear solution on the rolling element mesh model and the nose ring mesh model to obtain the contact stress of the contact surface.

[0011] Step 3: Check the contact strength of the nose ring mesh model.

[0012] The method for checking the contact strength of the nose ring mesh model is as follows: compare the contact stress with the allowable stress, and the comparison result is any of the following:

[0013] The first case: If the contact stress ≤ the allowable contact stress, then proceed to Step 4.

[0014] The second case: If the contact stress ≥ the allowable contact stress, then optimize the rolling element mesh model and repeat Steps 1 to 3 until the contact stress ≤ the allowable stress.

[0015] Step 4: Check the design of the corner of the relief groove.

[0016] The method for checking the design of the corner of the relief groove is as follows: compare the stress at the corner of the relief groove with the allowable contact stress, and the comparison result is any of the following:

[0017] The first case: If the stress at the corner of the relief groove ≤ the allowable contact stress, then proceed to Step 5.

[0018] The second case: If the stress at the corner of the relief groove ≥ the allowable contact stress, then optimize the mesh model at the corner of the relief groove and repeat Steps 1 to 4 until the stress at the corner of the relief groove ≤ the allowable contact stress.

[0019] Step 5: Check the fatigue strength of the corner of the relief groove.

[0020] The method for checking the fatigue strength of the corner of the relief groove is as follows: perform a fatigue simulation on the mesh model at the corner of the relief groove, and the simulation result is any of the following:

[0021] The first case: If the simulated fatigue life ≥ the allowable fatigue life, the finite element model design of the slewing bearing nose ring is reasonable, and the check is completed;

[0022] The second case: If the simulated fatigue life ≤ the allowable fatigue life, optimize the mesh model at the corner of the tool withdrawal groove, and repeat steps 1 to 5 until the simulated fatigue life ≥ the allowable fatigue life.

[0023] In the first step, it also includes setting Young's modulus and Poisson's ratio parameters for the finite element model of the slewing bearing nose ring, and setting constraint conditions for it;

[0024] The constraint conditions are: fixed constraints are applied at the contact surface between the bottom surface of the nose ring model and the base column, and non-linear contact is used between the rolling element model and the nose ring model to constrain the translational and rotational degrees of freedom.

[0025] In the first step, the method for generating the mesh discrete model of the slewing bearing nose ring is: first, cut the nose ring model into half rings, define one end section of the half ring as the source surface and the other end as the target surface, and at the same time define the corner coupling area as the encrypted mesh area and other areas as non-encrypted mesh areas, and sweep from the source surface to the target surface along the axis of the half ring to generate the mesh discrete model of the slewing bearing nose ring.

[0026] In the second step, the method for obtaining the contact stress of the contact surface is: use the augmented Lagrangian algorithm for the rolling element mesh model and the nose ring mesh model, set the load force, iteration convergence criterion and iteration step size to solve, and obtain the contact stress of the contact surface;

[0027] The method for obtaining the load force is: solve the equivalent load of the rolling element mesh model. The rolling element mesh model includes the upper row of rollers and the lower row of rollers. Calculate the forces on the upper row of rollers or the lower row of rollers and the upper row of rollers and the lower row of rollers to obtain the load force.

[0028] The formula used for calculating the force on the upper row of rollers or the lower row of rollers is:

[0029] P = Kδ 1.1

[0030]

[0031] Where P is the load borne by the roller; δ is the contact deformation; K is the deformation constant; L we is the effective length of the roller;

[0032] Assume that the axial displacement of the contact surface between the nose ring model and the rolling element model under the action of axial load and overturning moment is δ a, the angular displacement is θ, and the elastic deformation of the roller with the maximum load is:

[0033] δ max = δ a + θD pw / 2

[0034] where; δ max is the elastic deformation of the roller with the maximum load; D pw is the pitch diameter of the roller;

[0035] Position angle The elastic deformation of the roller at is:

[0036]

[0037]

[0038]

[0039] where: The position angle is the position angle of the Nth roller relative to the middle plane; ε is the load distribution parameter; δ max is the elastic deformation of the roller with the maximum load;

[0040] Assume that the load borne by the roller with the maximum load in a single row of rollers is P max , and the relationship between stress and contact deformation is:

[0041]

[0042] Thus, the contact load of the roller at the position angle is: is:

[0043]

[0044] Furthermore, the axial resultant force of this row of rollers is obtained as:

[0045]

[0046] where:

[0047] where: is the contact load; F is the axial resultant force received by a single row of rollers; Z is the tipping moment received by a single row of rollers; J0(ε) is the total elastic deformation of the rolling elements; is the integration with respect to the position angle;

[0048] The resultant moment is:

[0049]

[0050] Among them:

[0051] Among them: M is the overturning moment; is the contact load; D pw is the pitch diameter of the roller.

[0052] The formula used for calculating the forces on the upper row of rollers and the lower row of rollers is:

[0053] F Axial = F1 - F2 = P max J0 * (ε1)

[0054] Among them: J0 * (ε1) = Z1J0(ε1) - CZ2J0(ε2)

[0055] Among them:

[0056] M Capsize = M1 + M2 = 0.5P max J M * (ε1)

[0057] Among them:

[0058] J M * (ε1) = Z1D pw1 J M (ε1) + CZ2D pw2 J M (ε2)

[0059]

[0060] Among them; F Axial is the axial force of the nose ring; F1 is the resultant force on the upper track; F2 is the resultant force on the lower track; Z1J0(ε1) is the load distribution of the upper row of tracks; Z2J0(ε2) is the load distribution of the lower row of tracks; M Capsize is the overturning moment.

[0061] In the third step, the method for optimizing the rolling element mesh model is: increasing or decreasing the length and diameter of the rolling element mesh model to change the contact stress of the contact surface.

[0062] In the fourth and fifth steps, the method for optimizing the mesh model at the chamfer corner of the relief groove is: increasing or decreasing the radius size at the chamfer corner of the relief groove to change the stress at the chamfer corner of the mesh model at the chamfer corner of the relief groove.

[0063] In the fifth step, the method for fatigue simulation of the grid model at the corner of the relief groove is as follows: Set the S-N curve data and the number of cycles of the material of the nose ring model, and conduct fatigue simulation.

[0064] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0065] 1. In the method for stress concentration check of the relief groove of the nose ring of the offshore crane slewing bearing of the present invention, the method includes establishing a finite element model of the nose ring of the slewing bearing based on a computer, establishing a non-linear contact model, checking the contact strength of the grid model of the nose ring, design check at the corner of the relief groove, and fatigue strength check at the corner of the relief groove; In the application of this design, by establishing a rolling element model, a nose ring model and a model at the corner of the relief groove, and discretizing them into grids to generate a grid discretization model of the nose ring of the slewing bearing, then loading the load to obtain the stress at the corner of the local relief groove, and then establishing a non-linear contact model between the rolling element grid model and the nose ring grid model, solving it to obtain the contact stress, comparing the contact stress, the stress at the corner of the relief groove with the allowable stress, and finally conducting a fatigue life simulation on the nose ring model to complete the check work, and guiding the design at the corner of the relief groove with this as a reference. This method accurately captures the stress concentration level at the local corner and fully considers the non-linear contact relationship between the rolling element and the nose ring, and the obtained stress concentration result is relatively accurate. Therefore, the present invention not only has a relatively concentrated and accurate evaluation result, but also has a relatively accurate calculation result.

[0066] 2. In the method for stress concentration check of the relief groove of the nose ring of the offshore crane slewing bearing of the present invention, the nose ring model is cut into a semi-ring, one end section of the semi-ring is defined as the source surface, the other end is defined as the target surface, and at the same time, the corner area is defined as the encrypted grid area, and other areas are defined as non-encrypted grid areas, and the grid discretization model of the nose ring of the slewing bearing is generated by sweeping from the source surface to the target surface along the axis of the semi-ring; When this design is applied, local encrypted grids are used for the local corner, which are evenly distributed along the circumferential direction, capturing more concentrated local stress and avoiding the occurrence of the finite element hourglass self-locking phenomenon, thereby improving the accuracy of the calculation result. Therefore, the present invention can not only check the stress concentration level at the corner of the relief groove, but also has a high accuracy of the calculation result.

[0067] 3. In the method for stress concentration check of the relief groove of the slewing bearing nose ring in the present invention, a non-linear contact model is established between the rolling element mesh model and the nose ring mesh model, and then non-linear solution is carried out on the rolling element mesh model and the nose ring mesh model to obtain the contact stress of the contact surface. When this design is applied, the contact strength of the rolling element mesh model and the nose ring mesh model is quickly evaluated through non-linear contact calculation, which is more concentrated and accurate compared with theoretical calculation. Therefore, the present invention not only evaluates quickly, but also the evaluation results are more concentrated and accurate. Brief Description of the Drawings

[0068] Figure 1 is a schematic structural diagram of the finite element model of the slewing bearing nose ring in the present invention.

[0069] Figure 2 is a schematic diagram of the relative position between the nose ring model and the base column in the present invention.

[0070] Figure 3 is a schematic structural diagram of the mesh discrete model of the slewing bearing nose ring in the present invention.

[0071] Figure 4 is a schematic diagram of the relative position between the upper row of rollers and the lower row of rollers in the present invention.

[0072] Figure 5 is a schematic structural diagram of the non-linear contact model in the present invention.

[0073] Figure 6 is a schematic diagram of one of the optimized forms of the mesh model at the corner of the relief groove in Embodiment 1 of the present invention.

[0074] Figure 7 is a schematic diagram of one of the optimized forms of the mesh model at the corner of the relief groove in Embodiment 1 of the present invention.

[0075] Figure 8 is a schematic diagram of one of the optimized forms of the mesh model at the corner of the relief groove in Embodiment 1 of the present invention.

[0076] Figure 9 is a schematic diagram of the load application of the rolling element mesh model in Embodiment 1 of the present invention.

[0077] In the figure: finite element model of the slewing bearing nose ring 1, rolling element model 11, nose ring model 12, model at the corner of the relief groove 13, base column 14, mesh discrete model of the slewing bearing nose ring 2, rolling element mesh model 21, upper row of rollers 211, lower row of rollers 221, nose ring mesh model 22, mesh model at the corner of the relief groove 23, non-linear contact model 3, target surface 31, contact surface 32. Detailed Description of the Invention

[0078] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0079] See Figure 1 — Figure 9 , a method for stress concentration checking of the relief groove at the nose ring of a slewing bearing for offshore cranes. The checking method includes the following steps:

[0080] Step 1: Establish a finite element model 1 of the nose ring of the slewing bearing based on a computer;

[0081] The finite element model 1 of the nose ring of the slewing bearing includes: a rolling element model 11, a nose ring model 12, and a model 13 at the corner of the relief groove; then, the finite element model 1 of the nose ring of the slewing bearing is discretized into a mesh to generate a mesh discretization model 2 of the nose ring of the slewing bearing; the mesh discretization model 2 of the nose ring of the slewing bearing includes a rolling element mesh model 21, a nose ring mesh model 22, and a mesh model 23 at the corner of the relief groove; finally, a load is applied to the mesh discretization model 2 of the nose ring of the slewing bearing to obtain the stress at the corner of the relief groove;

[0082] Step 2: Establish a non - linear contact model 3;

[0083] The method for establishing the non - linear contact model 3 is: establish a non - linear contact model 3 between the rolling element mesh model 21 and the nose ring mesh model 22; the non - linear contact model 3 is a contact pair generated between each rolling element and the nose ring; the contact pair includes a target surface 31 and a contact surface 32; the target surface 31 is the rolling element, and the contact surface 32 is the support track surface of the nose ring; then, a non - linear solution is performed on the rolling element mesh model 21 and the nose ring mesh model 22 to obtain the contact stress of the contact surface 32;

[0084] Step 3: Check the contact strength of the nose ring mesh model 22;

[0085] The method for checking the contact strength of the nose ring mesh model 22 is: compare the contact stress with the allowable stress, and the comparison result is any of the following:

[0086] The first case: If the contact stress ≤ the allowable contact stress, then proceed to Step 4;

[0087] The second case: If the contact stress ≥ the allowable contact stress, optimize the rolling element mesh model 21 and repeat Steps 1 to 3 until the contact stress ≤ the allowable stress;

[0088] Step 4: Check the design at the corner of the relief groove;

[0089] The method for checking the design at the corner of the relief groove is: compare the stress at the corner of the relief groove with the allowable contact stress, and the comparison result is any of the following:

[0090] The first method: If the stress at the corner of the relief groove ≤ the allowable contact stress, then proceed to Step 5;

[0091] The second method: If the stress at the corner of the relief groove ≥ the allowable contact stress, then optimize the mesh model 23 at the corner of the relief groove, and repeat Steps 1 to 4 until the stress at the corner of the relief groove ≤ the allowable contact stress;

[0092] Step 5: Check the fatigue strength at the corner of the relief groove;

[0093] The method for checking the fatigue strength at the corner of the relief groove is as follows: Perform fatigue simulation on the mesh model 23 at the corner of the relief groove, and the simulation result is any of the following:

[0094] The first method: If the simulated fatigue life ≥ the allowable fatigue life, then the finite element model 1 of the slewing bearing nose ring is reasonably designed, and the check is completed;

[0095] The second method: If the simulated fatigue life ≤ the allowable fatigue life, then optimize the mesh model 23 at the corner of the relief groove, and repeat Steps 1 to 5 until the simulated fatigue life ≥ the allowable fatigue life.

[0096] In Step 1, it also includes setting the Young's modulus and Poisson's ratio parameters for the finite element model 1 of the slewing bearing nose ring, and setting the constraint conditions for it;

[0097] The constraint conditions are as follows: Fix the constraint at the contact surface between the bottom surface of the nose ring model 12 and the base column 14, and adopt non - linear contact between the rolling element model 11 and the nose ring model 12 to constrain the translational and rotational degrees of freedom.

[0098] In Step 1, the method for generating the mesh discrete model 2 of the slewing bearing nose ring is as follows: First, cut the nose ring model 12 into half - rings, define one end section of the half - ring as the source surface and the other end as the target surface. At the same time, define the corner coupling area as the encrypted mesh area and other areas as non - encrypted mesh areas, and sweep from the source surface to the target surface along the axis of the half - ring to generate the mesh discrete model 2 of the slewing bearing nose ring.

[0099] In Step 2, the method for obtaining the contact stress of the contact surface 32 is as follows: Adopt the augmented Lagrangian algorithm for the rolling element mesh model 21 and the nose ring mesh model 22, set the load force, iterative convergence criterion and iterative step size for solution, and obtain the contact stress of the contact surface 32;

[0100] The method for obtaining the load force is as follows: Solve the equivalent load of the rolling element grid model 21, where the rolling element grid model 21 includes the upper row of rollers 211 and the lower row of rollers 221. Calculate the forces on the upper row of rollers 211 or the lower row of rollers 221, and the forces on both the upper row of rollers 211 and the lower row of rollers 221 to obtain the load force.

[0101] The formula used for calculating the forces on the upper row of rollers 211 or the lower row of rollers 221 is:

[0102] P = Kδ 1.1

[0103] where P is the load borne by the roller; δ is the contact deformation; K is the deformation constant; L we is the effective length of the roller;

[0104] Assume that the axial displacement of the contact surface between the nose ring model 12 and the rolling element model 11 under the action of the axial load and the overturning moment is δ a , and the angular displacement is θ. Then the elastic deformation of the roller with the maximum load is:

[0105] δ max = δ a + θD pw / 2

[0106] where; δ max is the elastic deformation of the roller with the maximum load; D pw is the pitch diameter of the roller;

[0107] The elastic deformation of the roller at the position angle is:

[0108]

[0109]

[0110]

[0111] where: At the position angle is the position angle of the Nth roller relative to the middle plane; ε is the load distribution parameter; δ max is the elastic deformation of the roller with the maximum load;

[0112] Assume that the load borne by the roller with the maximum load in a single row of rollers is P max , and the relationship between the stress and the contact deformation is:

[0113]

[0114] Thus, the contact load of the roller at the position angle is is:

[0115]

[0116] Furthermore, the resultant axial force of this row of rollers is obtained as:

[0117]

[0118] Wherein:

[0119] Wherein: is the contact load; F is the resultant axial force received by a single row of rollers; Z is the tipping moment received by a single row of rollers; J0(ε) is the total elastic deformation of the rolling elements; is the integration of the position angle;

[0120] The resultant moment is:

[0121]

[0122] Wherein:

[0123] Wherein M is the tipping moment; is the contact load; D pw is the pitch diameter of the roller.

[0124] The formula used for calculating the forces on the upper row of rollers 211 and the lower row of rollers 221 is:

[0125] F Axial = F1 - F2 = P max J0*(ε1)

[0126] Wherein: J0*(ε1) = Z1J0(ε1) - CZ2J0(ε2)

[0127] Wherein:

[0128] M Capsize = M1 + M2 = 0.5P max J M *(ε1)

[0129] Wherein:

[0130] J M * (ε1) = Z1D pw1 J M (ε1) + CZ2D pw2 J M (ε2)

[0131]

[0132] Among them; F Axial is the axial force of the nose ring; F1 is the resultant force received by the upper track; F2 is the resultant force received by the lower track; Z1J0(ε1) is the load distribution of the upper row of tracks; Z2J0(ε2) is the load distribution of the lower row of tracks; M Capsize is the overturning moment.

[0133] In the third step, the method for optimizing the rolling element mesh model 21 is: increasing or decreasing the length and diameter of the rolling element mesh model 21 to change the contact stress of the contact surface 32.

[0134] In the fourth and fifth steps, the method for optimizing the mesh model 23 at the corner of the relief groove is: increasing or decreasing the radius size at the corner of the relief groove to change the stress at the corner of the mesh model 23 at the corner of the relief groove.

[0135] In the fifth step, the method for performing fatigue simulation on the mesh model 23 at the corner of the relief groove is: setting the S-N curve data and the number of cycles of the nose ring model 12 to perform fatigue simulation.

[0136] The principle of the present invention is explained as follows:

[0137] In the present invention, at the corner of the relief groove, the distance L from the center of the relief groove corner to the inner wall of the relief groove. In order to capture the stress concentration at the chamfer of the relief groove, a circular area with a radius of 1.5 - 2*L is established with the center of the relief groove corner as the axis, and rotated around the axis of the nose ring. This area is the encrypted mesh area, and other areas are non-encrypted mesh areas.

[0138] Example 1:

[0139] Refer to Figure 1 — Figure 9 , a method for checking the stress concentration of the relief groove of the nose ring of a marine crane slewing bearing. The checking method includes the following steps:

[0140] Step 1, establish a finite element model of the slewing bearing nose ring of a marine crane based on a computer;

[0141] The finite element model of the slewing bearing nose ring of a marine crane includes: a rolling element model, a nose ring model, and a model at the corner of the relief groove;

[0142] Furthermore, set the Young's modulus and Poisson's ratio parameters for the finite element model 1 of the slewing bearing nose ring of a marine crane, and set the constraint conditions for it; the Young's modulus is 2.06*10 11 Pa, and the Poisson's ratio is 0.3;

[0143] The constraint conditions are as follows: fixed constraints are applied at the contact surface between the bottom surface of the nose ring model 12 and the base column 14, and non-linear contact is adopted between the rolling element model 11 and the nose ring model 12 to constrain the translational degrees of freedom and rotational degrees of freedom in the X, Y, and Z directions;

[0144] Preferably, the method for generating the meshed discrete model of the slewing bearing nose ring 2 is as follows: First, the nose ring model 12 is cut into half rings. One end section of the half ring is defined as the source surface, and the other end is defined as the target surface. At the same time, the corner coupling area is defined as the area with encrypted meshes, and other areas are defined as areas with non-encrypted meshes. Based on the software Ansys, through the sweep method, the source surface is swept along the axis of the half ring to the target surface to generate the meshed discrete model of the slewing bearing nose ring 2;

[0145] The meshed discrete model of the slewing bearing nose ring includes a rolling element mesh model, a nose ring mesh model, and a mesh model at the corner of the relief groove; Finally, load is applied to the meshed discrete model of the slewing bearing nose ring to obtain the stress at the corner of the relief groove;

[0146] Step 2: Establish a non-linear contact model;

[0147] The method for establishing the non-linear contact model is as follows: Establish a non-linear contact model between the rolling element mesh model and the nose ring mesh model; The non-linear contact model is the contact pair generated between each rolling element and the nose ring; The contact pair includes a target surface and a contact surface; The target surface is the rolling element, and the contact surface is the support track surface of the nose ring; Then, non-linear solution is performed on the rolling element mesh model and the nose ring mesh model. The augmented Lagrangian algorithm is adopted for the rolling element mesh model 21 and the nose ring mesh model 22, and the load force, iteration convergence criterion, and iteration step size are set for solution to obtain the contact stress of the contact surface 32;

[0148] Preferably, the method for obtaining the load force is as follows: The equivalent load of the rolling element mesh model 21 is solved by using the Newton-Raphson algorithm. The rolling element mesh model 21 includes upper row rollers 211 and lower row rollers 221. Force calculation is performed on the upper row rollers 211 or lower row rollers 221 and the upper row rollers 211 and lower row rollers 221 to obtain the load force;

[0149] Preferably, the formula used for force calculation on the upper row rollers 211 or lower row rollers 221 is:

[0150] P = Kδ 1.1

[0151]

[0152] where P is the load borne by the roller; δ is the contact deformation; K is the deformation constant; L weis the effective length of the roller;

[0153] Assume that the axial displacement of the contact surface between the nose ring model (12) and the rolling element model (11) under the action of axial load and overturning moment is δ a , and the angular displacement is θ. Then the elastic deformation of the roller with the largest load is:

[0154] δ max = δ a + θD pw / 2

[0155] where; δ max is the elastic deformation of the roller with the largest load; D pw is the pitch diameter of the roller;

[0156] Position angle The elastic deformation of the roller at is:

[0157]

[0158]

[0159]

[0160] where: Position angle is the position angle of the Nth roller relative to the middle surface; ε is the load distribution parameter; δ max is the elastic deformation of the roller with the largest load;

[0161] Assume that the load borne by the roller with the largest load in a single row of rollers is P max , and the relationship between stress and contact deformation is:

[0162]

[0163] Thus, the contact load of the roller at the position angle is: is:

[0164]

[0165] Furthermore, the axial resultant force of this row of rollers is obtained as:

[0166]

[0167] where:

[0168] where: is the contact load; F is the axial resultant force received by a single row of rollers; Z is the overturning moment received by a single row of rollers; J0(ε) is the total elastic deformation of the rolling elements; To integrate the position angle;

[0169] The resultant moment is:

[0170]

[0171] Where:

[0172] Where: M is the overturning moment; is the contact load; D pw is the roller pitch diameter;

[0173] Preferably, the formula used for calculating the forces on the upper row of rollers 211 and the lower row of rollers 221 is:

[0174] F Axial = F1 - F2 = P max J0 * (ε1)

[0175] Where: J0 * (ε1) = Z1J0(ε1) - CZ2J0(ε2)

[0176] Where:

[0177] M Capsize = M1 + M2 = 0.5P max J M *(ε1)

[0178] Where:

[0179] J M * (ε1) = Z1D pw1 J M (ε1) + CZ2D pw2 J M (ε2)

[0180]

[0181] Where; F Axial is the axial force of the nose ring; F1 is the resultant force on the upper track; F2 is the resultant force on the lower track; Z1J0(ε1) is the load distribution of the upper row of tracks; Z2J0(ε2) is the load distribution of the lower row of tracks; M Capsize is the overturning moment;

[0182] Preferably, the iteration step size is: initial time step 0.1s; minimum time step 0.1s; maximum time step 0.25s;

[0183] Preferably, the iteration convergence criterion is: value analysis is calculated by the solver; dimensional tolerance 0.5%; minimum reference value 1N;

[0184] Step 3: Check the contact strength of the nose ring grid model;

[0185] The method for checking the contact strength of the nose ring grid model is as follows: Compare the contact stress with the allowable stress, and the comparison result is any of the following:

[0186] The first case: If the contact stress ≤ the allowable contact stress, then proceed to Step 4;

[0187] The second case: If the contact stress ≥ the allowable contact stress, optimize the rolling element grid model by increasing or decreasing the length and size of the rolling element grid model to change the contact stress of the contact surface 32, and repeat Steps 1 to 3 until the contact stress ≤ the allowable stress;

[0188] Step 4: Check the design of the corner of the relief groove;

[0189] The method for checking the design of the corner of the relief groove is as follows: Compare the stress at the corner of the relief groove with the allowable contact stress, and the comparison result is any of the following:

[0190] The first case: If the stress at the corner of the relief groove ≤ the allowable contact stress, then proceed to Step 5;

[0191] The second case: If the stress at the corner of the relief groove ≥ the allowable contact stress, optimize the grid model at the corner of the relief groove by increasing or decreasing the radius of the corner of the relief groove to change the stress at the corner of the grid model 23 of the corner of the relief groove, and repeat Steps 1 to 4 until the stress at the corner of the relief groove ≤ the allowable contact stress;

[0192] Step 5: Check the fatigue strength of the corner of the relief groove;

[0193] The method for checking the fatigue strength of the corner of the relief groove is as follows: Set the S-N curve data and the number of cycles of the material of the nose ring model, and perform fatigue simulation on the grid model at the corner of the relief groove. The simulation result is any of the following:

[0194] The first case: If the simulated fatigue life ≥ the allowable fatigue life, the design of the nose ring finite element model of the slewing bearing is reasonable, and the check is completed;

[0195] The second case: If the simulated fatigue life ≤ the allowable fatigue life, optimize the grid model at the corner of the relief groove by increasing or decreasing the radius of the corner of the relief groove to change the stress at the corner of the grid model 23 of the corner of the relief groove, and repeat Steps 1 to 5 until the simulated fatigue life ≥ the allowable fatigue life.

[0196] The above are only the preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. Any equivalent modifications or variations made by those of ordinary skill in the art according to the disclosure of the present invention shall fall within the protection scope recorded in the claims.

Claims

1. A method for checking the stress concentration of the relief groove of the slewing bearing nose ring of an offshore crane, characterized in that, The checking method includes the following steps: Step 1: Establish a finite element model (1) of the swing bearing nose ring based on a computer; The finite element model (1) of the swing bearing nose ring includes: a rolling element model (11), a nose ring model (12), and a model (13) at the corner of the tool withdrawal groove; then, mesh discretization is performed on the finite element model (1) of the swing bearing nose ring to generate a mesh discretization model (2) of the swing bearing nose ring; the mesh discretization model (2) of the swing bearing nose ring includes a rolling element mesh model (21), a nose ring mesh model (22), and a mesh model (23) at the corner of the tool withdrawal groove; finally, load is applied to the mesh discretization model (2) of the swing bearing nose ring to obtain the stress at the corner of the tool withdrawal groove; Step 2: Establish a non-linear contact model (3); The method for establishing the non-linear contact model (3) is: establish a non-linear contact model (3) between the rolling element mesh model (21) and the nose ring mesh model (22); the non-linear contact model (3) is a contact pair generated between each rolling element and the nose ring; the contact pair includes a target surface (31) and a contact surface (32); the target surface (31) is the rolling element, and the contact surface (32) is the support track surface of the nose ring; then, non-linear solution is performed on the rolling element mesh model (21) and the nose ring mesh model (22) to obtain the contact stress of the contact surface (32); Step 3: Check the contact strength of the nose ring mesh model (22); The method for checking the contact strength of the nose ring mesh model (22) is: compare the contact stress with the allowable stress, and the comparison result is any of the following: The first type: If the contact stress ≤ the allowable contact stress, then proceed to Step 4; The second type: If the contact stress ≥ the allowable contact stress, optimize the rolling element mesh model (21) and repeat Steps 1 to 3 until the contact stress ≤ the allowable stress; Step 4: Check the design of the corner of the tool withdrawal groove; The method for checking the design of the corner of the tool withdrawal groove is: compare the stress at the corner of the tool withdrawal groove with the allowable contact stress, and the comparison result is any of the following: The first type: If the stress at the corner of the tool withdrawal groove ≤ the allowable contact stress, then proceed to Step 5; The second type: If the stress at the corner of the tool withdrawal groove ≥ the allowable contact stress, optimize the mesh model (23) at the corner of the tool withdrawal groove and repeat Steps 1 to 4 until the stress at the corner of the tool withdrawal groove ≤ the allowable contact stress; Step 5: Check the fatigue strength of the corner of the tool withdrawal groove; The method for checking the fatigue strength of the corner of the tool withdrawal groove is: perform fatigue simulation on the mesh model (23) at the corner of the tool withdrawal groove, and the simulation result is any of the following: The first type: If the simulated fatigue life ≥ the allowable fatigue life, the design of the finite element model (1) of the swing bearing nose ring is reasonable, and the checking is completed; The second type: If the simulated fatigue life ≤ the allowable fatigue life, optimize the mesh model (23) at the corner of the tool withdrawal groove and repeat Steps 1 to 5 until the simulated fatigue life ≥ the allowable fatigue life.

2. The method for checking the stress concentration of the tool withdrawal groove of the nose ring of the offshore crane swing bearing according to claim 1, characterized in that: In the first step, it also includes setting Young's modulus and Poisson's ratio parameters for the finite element model (1) of the slewing bearing nose ring, and setting constraint conditions for it; The constraint conditions are: fixedly constraining at the contact surface between the bottom surface of the nose ring model (12) and the base column (14), and adopting non-linear contact between the rolling element model (11) and the nose ring model (12), constraining the translational degrees of freedom and rotational degrees of freedom.

3. A method for stress concentration checking of the relief groove of the slewing bearing nose ring of an offshore crane according to claim 1, characterized in that: In the first step, the method for generating the mesh discrete model (2) of the slewing bearing nose ring is as follows: First, cut the nose ring model (12) into a half-ring, define one end section of the half-ring as the source surface, the other end as the target surface, and at the same time define the corner coupling area as the encrypted mesh area and other areas as non-encrypted mesh areas, and sweep from the source surface to the target surface along the axis of the half-ring to generate the mesh discrete model (2) of the slewing bearing nose ring.

4. A method for stress concentration checking of the relief groove of the slewing bearing nose ring of an offshore crane according to claim 1, characterized in that: In the second step, the method for obtaining the contact stress of the contact surface (32) is: adopting the augmented Lagrangian algorithm for the rolling element mesh model (21) and the nose ring mesh model (22), setting the load force, iteration convergence criterion and iteration step size for solution, and obtaining the contact stress of the contact surface (32).

5. A method for stress concentration checking of the relief groove of the slewing bearing nose ring of an offshore crane according to claim 4, characterized in that: The method for obtaining the load force is: solving the equivalent load of the rolling element mesh model (21), the rolling element mesh model (21) includes the upper row of rollers (211) and the lower row of rollers (221), performing force calculation on the upper row of rollers (211) or the lower row of rollers (221) and between the upper row of rollers (211) and the lower row of rollers (221), and obtaining the load force.

6. A method for stress concentration checking of the relief groove of the slewing bearing nose ring of an offshore crane according to claim 5, characterized in that: The formula used for performing force calculation on the upper row of rollers (211) or the lower row of rollers (221) is: P = Kδ 1.1 Where P is the load borne by the roller; δ is the contact deformation; K is the deformation constant; L we is the effective length of the roller; Assume that the axial displacement of the contact surface between the nose ring model (12) and the rolling element model (11) under the action of axial load and overturning moment is δ a , and the angular displacement is θ. Then the elastic deformation of the roller with the maximum load is: δ max = δ a + θD pw / 2 Wherein; δ max is the elastic deformation of the roller with the maximum load; D pw is the pitch diameter of the roller; Position angle The elastic deformation of the roller at: Where: the angular position is the position angle of the Nth roller relative to the middle surface; ε is the load distribution parameter; δ max is the elastic deformation of the roller with the maximum load Assume that the load borne by the roller with the largest load in a single row of rollers is P max , and the relationship between stress and contact deformation is as follows: Thus, the contact load of the roller at the position angle is as follows: Furthermore, the resultant force in the axial direction of this row of rollers is obtained as: Wherein: Wherein: is the contact load; F is the axial resultant force received by a single row of rollers; Z is the tipping moment received by a single row of rollers; J0(ε) is the total elastic deformation of the rolling elements; is the integration of the position angle; The resultant moment is: Wherein: Where: M is the overturning moment; is the contact load; D pw is the pitch diameter of the roller.

7. A method for stress concentration checking of the relief groove of the slewing bearing nose ring of an offshore crane according to claim 5, characterized in that: The formula used for performing force calculation on the upper row of rollers (211) and the lower row of rollers (221) is: F Axia1 = F1 - F2 = P max J0 * (ε1) where: J0 * (ε1) = Z1J0(ε1) - CZ2J0(ε2) Wherein: M Capsize = M1 + M2 = 0.5P max J M *(ε1) where: J M * J(ε1) = Z1D pw1 J M J(ε1) + CZ2D pw2 J M J(ε2) Where; F Axial is the axial force of the nose ring; F1 is the resultant force on the upper track; F2 is the resultant force on the lower track; Z1J0(ε1) is the load distribution of the upper row of tracks; Z2J0(ε2) is the load distribution of the lower row of tracks; M Capsize is the overturning moment.

8. A method for stress concentration checking of the relief groove of the slewing bearing nose ring of an offshore crane according to claim 1, characterized in that: In the third step, the method for optimizing the rolling element mesh model (21) is: increasing or decreasing the length and diameter of the rolling element mesh model (21) to change the contact stress of the contact surface (32).

9. A method for stress concentration checking of the relief groove of the slewing bearing nose ring of an offshore crane according to claim 1, characterized in that: In the fourth and fifth steps, the method for optimizing the mesh model (23) at the corner of the relief groove is as follows: increasing or decreasing the radius size at the corner of the relief groove to change the stress at the corner of the mesh model (23) at the corner of the relief groove.

10. A method for checking the stress concentration of the relief groove of the nose ring of the slewing bearing of an offshore crane according to claim 1, characterized in that: In the fifth step, the method for simulating the fatigue degree of the mesh model (23) at the corner of the relief groove is as follows: setting the S-N curve data and the number of cycles of the material of the nose ring model (12) and performing fatigue degree simulation.

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