CN109726407B

CN109726407B - Method for calculating ultimate strength of variable-pitch bearing connecting bolt of wind generating set

Info

Publication number: CN109726407B
Application number: CN201711038143.1A
Authority: CN
Inventors: 严素欣; 邢春雷; 苏晓慰
Original assignee: Beijing Quanqi Technology Innovation Co ltd
Current assignee: Beijing Quanqi Technology Innovation Co ltd
Priority date: 2017-10-30
Filing date: 2017-10-30
Publication date: 2023-07-14
Anticipated expiration: 2037-10-30
Also published as: CN109726407A

Abstract

The invention belongs to the technical field of static strength calculation methods, and particularly relates to a method for calculating the ultimate strength of a variable-pitch bearing connecting bolt of a wind generating set, which aims to solve the problems in the existing calculation method, adopts multi-section refinement beam unit modeling, and improves simulation accuracy and efficiency by batch loading. The method is characterized in that: it includes finite element modeling of structural components; constraint boundary setting; load boundary setting; and (5) carrying out batch treatment under multiple load working conditions. The invention adopts the multi-section beam units to simulate bolts, and adopts multi-section modeling to solve the problem that the simulation result is not true due to the internal stress averaging of the units in the single beam simulation process; the problem that the stress area of the screw thread section is reduced due to the fact that the stress sectional areas of the real high-strength bolts are different is solved, so that the screw thread section and the screw rod section of the bolts are modeled by adopting different diameters, and modeling is more real and close to reality.

Description

Method for calculating ultimate strength of variable-pitch bearing connecting bolt of wind generating set

Technical Field

The invention belongs to the technical field of static strength calculation methods, and particularly relates to a method for calculating ultimate strength of a variable pitch bearing connecting bolt of a wind generating set.

Background

The variable-pitch bearing connecting bolts among the structural members of the fan play a role in transferring load among the structures of the generator set and bearing partial load, and the strength performance of the variable-pitch bearing connecting bolts determines the stability and reliability of the fan in the working process.

At present, more than ten bolts are arranged between two parts of the fan, hundreds of bolts exist in two circles, and the static strength of the bolts in the past is calculated or modeled by using a solid unit, so that the workload is large and the efficiency is low. Or modeling by adopting three beam units, generally adopting three sections, wherein the stress is averaged in the finite element stress calculation process of each beam unit, the problem of stress concentration at the transition part of the bolt thread and the screw rod can not be embodied, the simulation deviates from reality, and the obtained calculation result is dangerous.

Disclosure of Invention

The invention aims to solve the problems in the existing calculation method, adopts multi-section thinned beam unit modeling, and improves the simulation accuracy and efficiency by adopting batch loading.

The invention is realized in the following way:

a method for calculating ultimate strength of a variable-pitch bearing connecting bolt of a wind generating set specifically comprises the following steps:

step one: finite element modeling of structural components. Because the structure is a central symmetry structure, 1/3 hub structure, variable pitch bearing structure and blade structure are selected for finite element modeling, and the hub structure adopts second order tetrahedron solid unit modeling. The variable-pitch bearing structure has higher grid requirements due to the fact that bolts are involved, and grid division is conducted by adopting hexahedral units. Meanwhile, the non-linear characteristic of load transmission of rollers is utilized by the inner ring and the outer ring of the variable pitch bearing, and the GAP unit which is only pressed and not pulled is adopted to connect the inner ring and the outer ring of the bearing to simulate the characteristics of the rollers. The leaves were simulated using hexahedral cell divisions greater than 1.5 times the diameter. The parts are connected, and friction contact is established between the inner ring of the variable-pitch bearing and the blades and between the outer ring of the variable-pitch bearing and the hub for simulation. The bolt modeling is carried out, the high-strength common bolt is adopted as the pitch connecting bolt of the wind generating set, and the bolt is divided into two circles and is respectively used for connecting the outer ring of the pitch bearing with the hub structure, the inner ring of the pitch bearing and the blade structure. The bolt is divided into a threaded part, a screw part and a nut part. The bolt modeling of the invention adopts a plurality of sections of beam units for modeling, the threaded part equally divides 4 sections according to geometric length, four head-to-tail connected beam units are established, two beam units are established by the threads and 4-5cm of the screw transition section, the rest screw part is evenly divided into about 10 sections, and 10 beam units are established. The thread section is modeled by adopting a diameter corresponding to the stress sectional area, and the screw section is modeled by adopting a nominal diameter of the bolt. The upper and lower parts of each beam unit of the thread section are bound with surrounding units of the bolt hole by using the beam units with the diameter of about 5mm, the uppermost end of the bolt is bound with the screw hole at the uppermost end of the hole, and the simulation nut is screwed.

Step two: constraint boundary setting. And the translational and rotational degrees of freedom of the 1/3 hub cut surface X, Y, Z direction are restrained, and the Z-direction rotation restraint of the inner gear ring area of the variable pitch bearing under the blade root coordinate system is restrained.

Step three: load boundary setting. The 1/3 hub, the outer ring of the variable-pitch bearing, the inner ring of the variable-pitch bearing and the blades are clamped through bolts, in an analysis model, the bolts are adopted for pretightening force simulation, and the simulation is applied to a node unit in the middle section of the screw. In the static strength analysis of the variable pitch connecting bolt structure, the load is mainly realized through the blade root load, a control point is established at the origin of a blade root coordinate system, then the control point is rigidly connected with the end face of the blade, and the load is applied to the control point through rigid load transmission.

Step four: and (5) carrying out batch treatment under multiple load working conditions. In the model, a control point is built into a set, a finite element model is output as a basic Base file, and various load working condition files are built through a Matlab program. Therefore, when each load calculation file is submitted by calculation, each load working condition file automatically calls the finite element model basic file, and multi-load working condition batch processing is realized.

The beneficial effects of the invention are as follows:

firstly, adopting a multi-section beam unit to simulate a bolt, and adopting multi-section modeling to solve the problem that a simulation result is not real due to the internal stress averaging of the unit in the single beam simulation process;

secondly, considering that the stressed cross sections of the high-strength bolts are different, the problem that the stressed area of the threaded section is reduced due to the threads is solved, so that the threaded section and the screw section of the bolts are modeled by adopting different diameters, and the modeling is more real and close to reality.

Again, according to engineering experience, the greatest stress position of the bolt is at the connecting part of the thread section and the screw section, which is caused by the difference of stress areas. Therefore, in the modeling process, two sections of modeling are thinned for the thread section and the screw section, and the purpose is to eliminate unit internal stress averaging in the single beam simulation process, so that the calculation result is more accurate.

And the invention templates the basic geometric modeling file, establishes a batch processing working condition mechanism of each load, greatly simplifies the complicated steps of manual loading under multiple working conditions, saves modeling loading time and reduces error rate.

Drawings

FIG. 1 is a geometric model of the static strength calculation of a pitch link bolt;

FIG. 2 is a pitch bearing inner and outer race gap unit connection;

FIG. 3 is a 3D view of a single bolt;

FIG. 4 is a pitch link bolt connection diagram;

FIG. 5 is a hub structural constraint;

fig. 6 is pitch bearing constraint.

Detailed Description

The invention is further described below with reference to the drawings and examples.

It should be noted that the method for calculating the static strength of the connecting bolt structural member of the present invention is applicable to any method for calculating the static strength of a connecting bolt of a variable pitch bearing of a fan, and is not limited to the specific model of fan connecting bolt structural member shown in the present application. In addition, the static strength calculation method for the variable-pitch bearing connecting bolt is suitable for static strength analysis of the variable-pitch bearing connecting bolt in any type of fan, and has good universality.

firstly, the hub and the pitch bearing are led into finite element pretreatment software, geometric structure details are cleaned, a model is simplified, and the remaining 1/3 hub of the hub is cut, namely the structure 1 in the structure drawing 1.

And (5) dividing grids. The hub structure is divided into two-order tetrahedral grids, and the variable-pitch bearing is divided into hexahedral grids. The blades stretch the blade prosthesis with the diameter of 1.5 times according to the grid of the contact surface of the inner ring of the variable-pitch bearing, and the blade prosthesis is also a hexahedral grid. GAP units (i.e. 2 structures in figure 2) are established to connect the inner and outer ring structures of the bearing.

And establishing a connecting bolt model. Modeling is carried out by adopting a plurality of sections of beam units, the threaded part is divided into 4 sections equally according to the geometric length, four head-to-tail connected beam units are established, two beam units are established by the threads and 4-5cm of the screw transition section, the rest screw part is divided into about 10 sections evenly, and 10 beam units are established. The thread section is modeled by adopting a diameter corresponding to the stress sectional area, and the screw section is modeled by adopting a nominal diameter of the bolt. FIG. 3 is a finite element 3D model of a variable pitch connecting bolt, wherein each beam unit of a threaded section is bound with surrounding units of a bolt hole by using beam units with diameters of about 5mm, and the uppermost end of the bolt is bound with a screw hole at the uppermost end of the hole. Fig. 4 is a schematic diagram of a bolting structure, and fig. 4 is a finite element model of a bolt.

Constraints and loads are established. FIGS. 5 and 6 illustrate 1/3 of the hub structure constraint and pitch bearing constraint. In fig. 5, 4 is translational and rotational degrees of freedom in the direction of a 1/3 hub section X, Y, Z, and in fig. 6, 5 is a Z-direction rotational constraint of the inner gear ring area of the constrained pitch bearing under the blade root coordinate system. The load boundary is set, and a bolt pretightening force corresponding to the diameter of the bolt is applied to the middle section node unit of the screw. And (3) establishing a control point at the origin of the blade root coordinate system, then rigidly connecting the control point with the end surface of the blade, and applying a load on the control point through rigid load transmission.

Submitting the calculation. The basic modeling file is output in.inp format. And generating load of each load working condition by utilizing the Matlab to load working conditions in the limit load table. And submitting and calculating the load of each load working condition, wherein the inp file is automatically called in the calculation process.

And checking the calculation result. The calculation was opened in the Abaqus software odb file, selecting a finite element view of the bolt shank and thread transition section.

The embodiment of the present invention has been described in detail with reference to the embodiments, but the present invention is not limited to the embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the spirit of the present invention. The invention may be practiced otherwise than as specifically described in the specification.

Claims

1. A method for calculating ultimate strength of a variable-pitch bearing connecting bolt of a wind generating set specifically comprises the following steps:

step one: modeling the finite element of the structural component; selecting a 1/3 hub structure, a variable pitch bearing structure and a blade structure for finite element modeling, wherein the hub structure adopts a second-order tetrahedron solid unit for modeling; dividing grids by adopting hexahedral units; GAP units which are only pressed and not pulled are adopted to connect the inner ring and the outer ring of the bearing to simulate the roller characteristics; the blade adopts a prosthesis divided by hexahedral units with the diameter larger than 1.5 times; the parts are connected, and friction contact is established between the inner ring of the variable-pitch bearing and the blades and between the outer ring of the variable-pitch bearing and the hub for simulation; the method comprises the steps of modeling a bolt, wherein a high-strength common bolt is adopted as a pitch-variable connecting bolt of the wind generating set, and the bolt is divided into two circles and is respectively used for connecting an outer ring of a pitch-variable bearing with a hub structure, an inner ring of the pitch-variable bearing and a blade structure; the bolt is divided into a threaded part, a screw part and a nut part; the bolt modeling adopts a multi-section beam unit for modeling, a threaded part equally divides 4 sections according to geometric length, four head-to-tail connected beam units are built, two beam units are built by threads and 4-5cm of a screw transition section, 10 sections are evenly divided by the rest screw part, and 10 beam units are built; the thread section is modeled by adopting a diameter corresponding to the stress sectional area, and the screw section is modeled by adopting a nominal diameter of the bolt; each beam unit of the thread section is bound with surrounding units of the bolt hole by a beam unit with the diameter of about 5mm, the uppermost end of the bolt is bound with a screw hole at the uppermost end of the hole, and the simulation nut is screwed;

step two: constraint boundary setting; restraining translational and rotational degrees of freedom in the direction of a 1/3 hub section X, Y, Z, and restraining Z-direction rotation restraint of an inner gear ring area of a variable pitch bearing under a blade root coordinate system;

step three: load boundary setting; clamping the 1/3 hub, the outer ring of the variable-pitch bearing, the inner ring of the variable-pitch bearing and the blades through bolts, simulating by adopting bolt pretightening force in an analysis model, and applying the simulation to a node unit in the middle section of the screw; in the static strength analysis of the variable pitch connecting bolt structure, the load is realized through the blade root load, a control point is established at the origin of a blade root coordinate system, then the control point is rigidly connected with the end face of the blade, and the load is applied to the control point through rigid load transmission;

step four: batch processing under multiple load working conditions; in the model, a control point is built into a set, a finite element model is output as a basic Base file, and various load working condition files are built through a Matlab program; therefore, when each load calculation file is submitted by calculation, each load working condition file automatically calls the finite element model basic file, and multi-load working condition batch processing is realized.