Method and system for evaluating ultimate strength of cabin truss

Abstract

The invention discloses an ultimate strength evaluation method and system for a cabin truss, and relates to the field of wind turbine generator testing, and the method comprises the steps: building a finite element model composed of a cabin cover, an elastic support and the cabin truss; applying a boundary condition to the finite element model, and performing ultimate strength solution calculation on the finite element model based on the boundary condition to obtain an ultimate strength calculation result; determining the maximum equivalent stress value of the cabin truss according to the ultimate strength calculation result; the allowable stress value of the cabin truss is determined, and the ultimate strength of the cabin truss is evaluated based on the allowable stress value and the maximum equivalent stress value, so that the ultimate strength of the cabin truss is accurately evaluated.

Description

Technical Field

[0001] The present application relates to the technical field of wind turbine testing, and in particular to an ultimate strength assessment method and system for a cabin truss. Background Art

[0002] The nacelle truss, as the core supporting structure inside the nacelle of a wind turbine, plays a key role in being closely connected to the nacelle cover through elastic support, effectively bearing and transmitting the wind load from the nacelle cover and the inertial load caused by wind. This structure is usually made of high-strength steel sections and plates precisely welded together to ensure its structural stability and load-bearing capacity. However, under extreme external static load conditions, especially in areas where weld toes and plate stresses are highly concentrated, the nacelle truss is prone to ultimate strength failure, which will not only damage the integrity of the nacelle cover, but may also cause it to lose its protective function for the delicate components inside the nacelle, thus posing a serious threat to the operational safety of the entire wind turbine. Therefore, it is crucial to evaluate the ultimate strength of the nacelle truss.

[0003] The currently used evaluation methods often only focus on the influence of the hub center load and the inertial load of the nacelle itself, resulting in inaccurate evaluation results.

[0004] Therefore, how to improve the accuracy of the ultimate strength assessment results of the cabin truss has become a technical problem that needs to be solved urgently. Summary of the invention

[0005] In view of this, the main purpose of the present application is to provide a method and system for evaluating the ultimate strength of a cabin truss, with the aim of accurately evaluating the ultimate strength of the cabin truss.

[0006] The first aspect of the present application provides a method for evaluating the ultimate strength of a cabin truss, the method comprising:

[0007] Establish a finite element model consisting of the nacelle cover, elastic support and nacelle truss;

[0008] Apply boundary conditions to the finite element model, and perform ultimate strength calculation on the finite element model based on the boundary conditions to obtain ultimate strength calculation results;

[0009] Determine the maximum equivalent stress of the cabin truss based on the ultimate strength calculation results;

[0010] The allowable stress value of the cabin truss is determined, and the ultimate strength of the cabin truss is evaluated based on the allowable stress value and the maximum equivalent stress.

[0011] In some implementations of the first aspect of the present application, in the finite element model, the nacelle cover is meshed using shell elements, and the elastic support and the nacelle truss are meshed using solid elements;

[0012] In some implementations of the first aspect of the present application, the boundary conditions include: connection boundary conditions, constraint boundary conditions, and load boundary conditions;

[0013] Among them, the connection boundary condition is that the connection relationship between the cabin cover, elastic support and cabin truss is binding contact, the constraint boundary condition is the bottom full displacement constraint of the cabin truss, and the load boundary condition is the load transferred to the cabin truss by the cabin cover under multiple working conditions.

[0014] In some implementations of the first aspect of the present application, the acting load includes: wind load; the load boundary conditions include: wind load on the windward side of the nacelle cover, wind load on the leeward side of the nacelle cover, and wind load on the parallel side of the nacelle cover.

[0015] In some implementations of the first aspect of the present application, the acting load also includes: a gravity load, and the load boundary conditions include: a first acting load obtained by superimposing the wind load on the windward surface of the nacelle cover and the gravity load of the nacelle cover, a second acting load obtained by superimposing the wind load on the leeward surface of the nacelle cover and the gravity load of the nacelle cover, and a third acting load obtained by superimposing the wind load on the surface parallel to the nacelle cover and the gravity load of the nacelle cover.

[0016] In some implementations of the first aspect of the present application, the maximum value of the equivalent stress of the cabin truss includes: the maximum value of the equivalent stress of the weld, and the maximum value of the equivalent stress of the cabin truss is determined according to the ultimate strength calculation result, including:

[0017] According to the ultimate strength calculation results, determine the first position corresponding to the maximum value of the weld equivalent stress under different working conditions;

[0018] For the first position under each working condition, the equivalent stress value of the second position at a first distance from the first position and the equivalent stress value of the third position at a second distance from the first position are respectively extracted, and the equivalent stress value of the first position is calculated according to the equivalent stress value of the second position and the equivalent stress value of the third position, so as to obtain the equivalent stress value of the first position under each working condition;

[0019] The maximum value among the equivalent stress values ​​at the first position under each working condition is determined as the maximum equivalent stress value of the weld.

[0020] In some implementations of the first aspect of the present application, the maximum value of the equivalent stress of the cabin truss includes: the maximum value of the equivalent stress of the parent material, and the maximum value of the equivalent stress of the cabin truss is determined according to the ultimate strength calculation result, including:

[0021] According to the ultimate strength calculation results, the maximum value of the equivalent stress of the parent material under different working conditions is determined, and the maximum value among the maximum values ​​of the equivalent stress of the parent material under different working conditions is determined as the maximum value of the equivalent stress of the parent material.

[0022] In some implementations of the first aspect of the present application, the allowable stress value of the cabin truss includes: an allowable stress value of a weld, and determining the allowable stress value of the cabin truss includes:

[0023] The allowable stress value of the weld is determined based on the yield strength of the weld and the additional safety factor of the first material.

[0024] In some implementations of the first aspect of the present application, the allowable stress value of the cabin truss includes: the allowable stress value of the parent material, and determining the allowable stress value of the cabin truss includes:

[0025] The allowable stress value of the parent material is determined based on the yield strength of the parent material and the additional safety factor of the second material.

[0026] A second aspect of the present application provides an ultimate strength assessment system for a cabin truss, the system comprising: a cabin truss finite element modeling subsystem, a computational model boundary condition loading calculation subsystem, and an ultimate strength assessment subsystem;

[0027] The cabin truss finite element modeling subsystem is used to establish a finite element model consisting of the cabin cover, elastic support and cabin truss;

[0028] The technical solution provided by this application has the following beneficial effects:

[0029] In the technical solution provided in the present application, firstly, considering the unique elastic support connection mode between the truss and the cabin cover, which has a significant impact on the local stress distribution of the truss and can significantly change the stress distribution pattern, a finite element model consisting of the cabin cover, the elastic support and the cabin truss is established to introduce the influence of the elastic support on the local stress distribution of the truss for subsequent calculations; then, boundary conditions are imposed on the finite element model to simulate the stress state in the actual use environment, and the ultimate strength solution calculation of the finite element model is performed, and the ultimate strength calculation result is obtained in combination with the influence of the elastic support connection mode on the stress distribution of the truss. Afterwards, according to the ultimate strength calculation result, the maximum value of the equivalent stress of the cabin truss under the boundary conditions can be determined to reflect the stress level of the cabin truss under extreme conditions. Finally, the allowable stress value of the cabin truss is determined, and the ultimate strength of the cabin truss can be accurately evaluated based on the maximum value of the equivalent stress and the allowable stress value. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic diagram of a process flow of an ultimate strength assessment method for a cabin truss provided in an embodiment of the present application;

[0031] Figure 2 A schematic diagram of a finite element model provided in an embodiment of the present application;

[0032] Figure 3A schematic flow chart of another method for evaluating the ultimate strength of a cabin truss provided in an embodiment of the present application;

[0033] Figure 4 A schematic diagram of the wind pressure coefficients of each wind-bearing surface of the nacelle cover provided in an embodiment of the present application;

[0034] Figure 5 A schematic flow chart of another method for evaluating the ultimate strength of a cabin truss provided in an embodiment of the present application;

[0035] Figure 6 A schematic flow chart of another method for evaluating the ultimate strength of a cabin truss provided in an embodiment of the present application;

[0036] Figure 7 A schematic flow chart of another method for evaluating the ultimate strength of a cabin truss provided in an embodiment of the present application;

[0037] Figure 8 A schematic structural diagram of an ultimate strength assessment system for a cabin truss provided in an embodiment of the present application. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0039] Since the truss and the cabin cover are connected by elastic supports, this connection method has a great influence on the local stress distribution of the truss. This factor is not taken into account in the existing method, resulting in inaccurate calculation results. Therefore, an embodiment of the present application provides a method and system for evaluating the ultimate strength of the cabin truss, which aims to accurately evaluate the ultimate strength of the cabin truss.

[0040] See also Figure 1 As shown, the embodiment of the present application provides a method for evaluating the ultimate strength of a cabin truss, which may specifically include the following steps:

[0041] S101: Establish a finite element model consisting of the cabin cover, elastic support and cabin truss.

[0042] The nacelle cover refers to the outer shell used to cover and protect the internal components of the nacelle in a wind turbine generator set; the nacelle truss refers to the frame structure that supports the nacelle cover and internal equipment in a wind turbine generator set. As the main load-bearing structure of the nacelle, it bears the weight of the internal equipment of the nacelle and the external environmental load. The elastic support refers to the structural element connecting the nacelle cover and the nacelle truss. It has a certain degree of flexibility and rigidity, and can deform within a certain range to absorb and disperse stress, reduce stress concentration and impact on the truss, thereby improving the safety and stability of the overall structure.

[0043] In the embodiment of the present application, the following is constructed according to the actual design parameters and geometric dimensions of the cabin cover 3, the elastic support 2 and the cabin truss 1: Figure 2 The finite element model shown is used to simulate the elastic support connection between the truss and the nacelle cover, so as to accurately reflect the influence of the elastic support on the local stress distribution of the truss in the subsequent calculation process. Among them, the finite element model is a computational model used for numerical analysis, which simulates and predicts the behavior of an object in physical processes such as force by discretizing the continuum into a finite number of interconnected units.

[0044] Generally speaking, the nacelle cover is a relatively thin surface structure, and its thickness is much smaller than other dimensions. Therefore, in some implementations of the embodiments of the present application, in the finite element model, shell elements are used to simulate the thin-walled structure of the nacelle cover, while the elastic support and the nacelle truss are meshed with solid elements. This is conducive to the accurate calculation of the subsequent ultimate strength solution.

[0045] In some implementations of the embodiments of the present application, the number of data layers in the wall thickness direction at locations where the local stress of the cabin truss is relatively large is further set to at least three layers to ensure a more accurate evaluation result.

[0046] S102: applying boundary conditions to the finite element model, and performing ultimate strength calculation on the finite element model based on the boundary conditions to obtain an ultimate strength calculation result.

[0047] In the embodiments of the present application, the boundary condition refers to the force, displacement or other physical quantity conditions or constraints used to describe and define the model boundary in finite element analysis. By applying the boundary condition, the interaction between the structure of the cabin truss and the external environment is simulated. It can be understood that the present application performs an ultimate strength assessment on the cabin truss, so the boundary condition specifically simulates the extreme environment of the cabin truss.

[0048] After applying the boundary conditions, the finite element analysis software is used to discretize a finite element model into individual units, and the linear solution method is used to calculate the ultimate strength of the model to obtain the calculation result data corresponding to each unit, that is, the ultimate strength calculation result; it can be understood that the calculation process takes into account the influence of the elastic support connection method on the stress distribution of the truss.

[0049] S103: Determine the maximum value of the equivalent stress of the cabin truss according to the ultimate strength calculation result.

[0050] In an embodiment of the present application, the calculation result data corresponding to each unit in the ultimate strength calculation result can be represented by different colors, for example, from high red to low blue, so that the cabin truss in the entire finite element model presents a continuous change in color, that is, a cloud map. Since the present application extracts equivalent stress, it can also be called an equivalent stress cloud map. Afterwards, by comparing the equivalent stress values ​​or colors of different areas, the maximum equivalent stress of the cabin truss can be determined, and the maximum equivalent stress can reflect the stress level of the cabin truss under extreme conditions.

[0051] In the embodiments of the present application, the maximum value of the equivalent stress of the cabin truss includes: the maximum value of the equivalent stress of the weld and / or the maximum value of the equivalent stress of the base material. The specific description can be found in the subsequent embodiments.

[0052] S104: Determine the allowable stress value of the cabin truss, and evaluate the ultimate strength of the cabin truss based on the allowable stress value and the maximum equivalent stress value.

[0053] In an embodiment of the present application, the allowable stress value of the cabin truss refers to the maximum stress value that the cabin truss can withstand under actual working conditions. After determining the allowable stress value, the ultimate strength of the cabin truss can be further evaluated based on the allowable stress value and the maximum value of the equivalent stress. For example, by comparing the allowable stress value with the equivalent stress value, when the equivalent stress value is greater than the allowable stress value, it is considered that the cabin truss has a higher strength and meets the design requirements. For another example, the ultimate safety factor of the cabin truss is determined based on the ratio of the allowable stress value to the equivalent stress value, and the ultimate strength of the cabin truss is evaluated based on the size of the ultimate safety factor. Furthermore, different strength grades can be divided based on the numerical interval into which the ultimate safety factor falls.

[0054] In the embodiments of the present application, the allowable stress value of the cabin truss may include: the allowable stress value of the weld and / or the allowable stress value of the parent material. The specific description can be found in the subsequent embodiments.

[0055] exist Figure 1In the process shown, first, considering the unique elastic support connection between the truss and the cabin cover, which has a significant impact on the local stress distribution of the truss and can significantly change the stress distribution pattern, a finite element model consisting of the cabin cover, elastic support and cabin truss is established to introduce the influence of the elastic support on the local stress distribution of the truss for subsequent calculations; then, boundary conditions are applied to the finite element model to simulate the stress state in the actual use environment, and the ultimate strength solution calculation of the finite element model is performed, and the ultimate strength calculation result is obtained in combination with the influence of the elastic support connection method on the stress distribution of the truss. Afterwards, according to the ultimate strength calculation result, the maximum equivalent stress of the cabin truss under the boundary conditions can be determined to reflect the stress level of the cabin truss under extreme conditions. Finally, the allowable stress value of the cabin truss is determined, and the ultimate strength of the cabin truss can be accurately evaluated based on the maximum equivalent stress and the allowable stress value.

[0056] See also Figure 3 As shown, the embodiment of the present application provides a method for determining the ultimate strength of a cabin truss. Figure 1 Based on the process shown, the boundary conditions are further described, which may include the following steps:

[0057] S301: Establish a finite element model consisting of a cabin cover, elastic supports, and cabin trusses.

[0058] In the embodiment of the present application, the shell elements and solid elements in the finite element model have the feature of configuring material properties. At the same time, the embodiment of the present application sets the thickness size of the shell element according to the actual thickness distribution, and the material properties of the elastic support are set according to the actual stiffness value.

[0059] Taking the steel truss as an example, the shell element thickness dimension attribute is set according to the actual thickness of 10 mm, and the material properties of each component are shown in Table 1;

[0060] Table 1. Material properties of cabin truss, elastic support and cabin cover

[0061]

[0062] S302: applying boundary conditions to the finite element model, and performing ultimate strength calculation on the finite element model based on the boundary conditions to obtain ultimate strength calculation results; the boundary conditions include: connection boundary conditions, constraint boundary conditions and load boundary conditions; wherein the connection boundary condition is that the connection relationship between the cabin cover, the elastic support and the cabin truss is binding contact, the constraint boundary condition is the bottom full displacement constraint of the cabin truss, and the load boundary condition is the action load transmitted to the cabin truss by the cabin cover under multiple working conditions.

[0063] At present, conventional contact is mainly divided into binding contact and friction contact. Among them, binding contact means that the parts will not move relative to each other, including sliding and separation, while friction contact means that the parts can move relative to each other and there is a friction coefficient. Considering that the cabin cover, elastic support parts and cabin trusses are welded together, it is more in line with the requirements of binding contact. Therefore, this application applies the connection boundary condition of binding contact to the connection relationship between the cabin cover, elastic support and cabin trusses on the finite element model.

[0064] In addition, in order to ensure that the calculation process complies with the actual physical constraints, constraint boundary conditions for limiting the movement of the model are further applied to the finite element model. Here, the constraint boundary conditions in the embodiment of the present application are specifically the bottom full displacement constraints of the cabin truss, which limit the displacement and rotation of the bottom of the cabin truss in all directions to be fixed, that is, Ux, Uy, Uz, Rotx, Roty, Rotz = 0; wherein U usually represents the translation displacement, Ux, Uy, Uz are the translation displacements in three directions of the rectangular coordinate system, Rot usually represents the rotation displacement, and Rotx, Roty, Rotz are the rotation displacements around the three coordinate axes.

[0065] Finally, in order to simulate the external loads on the cabin truss under actual working conditions, load boundary conditions for simulating external loads are further applied to the finite element model to evaluate the ultimate strength of the cabin truss under extreme working conditions. Specifically, the load boundary conditions are the action loads transmitted to the cabin truss by the cabin cover under multiple working conditions, where the action loads refer to the various forces applied by the cabin cover on the cabin truss.

[0066] In some implementations of the present application, considering that wind can generate different forces on different surfaces, affecting the stability and strength of the structure, the present application uses wind load as the action load, wherein the wind load refers to the force of wind on the surface of the nacelle cover. At this time, the action load includes: wind load; the load boundary conditions may specifically include: wind load on the windward surface of the nacelle cover, wind load on the leeward surface of the nacelle cover, and wind load on the parallel surface of the nacelle cover.

[0067] Among them, Figure 4 As shown, the wind pressure coefficient of each wind-bearing surface of the nacelle cover can be determined according to the GL2010 specification. The wind pressure coefficient values ​​at different positions are shown in Table 2, where "+" indicates that the surface is under pressure, and "-" indicates that the surface is under tension.

[0068] Table 2 Wind pressure coefficients at different positions of the nacelle cover

[0069]

[0070] Based on the wind pressure coefficients at different positions of the nacelle cover, the pressure loads on each wind-bearing surface of the nacelle cover under three wind load conditions can be further calculated. Specifically, according to the GL2010 specification, the nacelle cover is subjected to three types of extreme wind load conditions, namely, windward conditions, crosswind conditions, and leeward conditions. The surface pressure load P of each wind-bearing surface of the nacelle cover under the three wind load conditions is calculated according to the following formula:

[0071]

[0072] Among them, the air density is ρ, the wind pressure coefficient is Cp, and the wind speed is v.

[0073] In the embodiment of the present application, the air density ρ is set to 1.225 kg / m3, and the wind load adopts the instantaneous wind load v=80 m / s which occurs once in 50 years. The pressure loads on each surface of the nacelle cover under the three wind load conditions are calculated according to the above formula. The results are shown in Table 3.

[0074] Table 3 Nacelle cover surface pressure load (unit: Pa)

[0075]

[0076] In some implementations of the embodiments of the present application, the inventors took into account that in addition to the wind load transmitted by the cabin cover, the cabin truss also bears the gravity load of the cabin cover which is transmitted to the truss through elastic supports, and therefore further introduced a gravity load, wherein the gravity load refers to the load applied to the cabin truss by the cabin cover through elastic supports due to the action of gravity.

[0077] At this time, the load boundary conditions specifically include: a first acting load obtained by superimposing the wind load on the windward surface of the nacelle cover and the gravity load of the nacelle cover, a second acting load obtained by superimposing the wind load on the leeward surface of the nacelle cover and the gravity load of the nacelle cover, and a third acting load obtained by superimposing the wind load on the surface parallel to the nacelle cover and the gravity load of the nacelle cover.

[0078] In the embodiment of the present application, the value of the inertial load is set to 9.81×1.1 m / s2 as the gravity acceleration, where 1.1 is the additional safety factor of the load.

[0079] After superimposing the gravity load and wind load, the working conditions used for the ultimate strength calculation of the cabin truss are shown in Table 4.

[0080] Table 4 Load conditions for calculation of ultimate strength of cabin truss

[0081] Working conditions Wind load Nacelle weight / N Condition 1 Windward conditions g＝9.81×1.1 Condition 2 Crosswind conditions g＝9.81×1.1 Condition 3 Leeward conditions g＝9.81×1.1

[0082] S303: Determine the maximum equivalent stress of the cabin truss according to the ultimate strength calculation result;

[0083] S304: Determine the allowable stress value of the cabin truss, and evaluate the ultimate strength of the cabin truss based on the allowable stress value and the maximum equivalent stress value.

[0084] exist Figure 3 In the process shown, by applying boundary conditions including connection boundary conditions, constraint boundary conditions and load boundary conditions on the finite element model, the actual use scenario of the cabin truss under extreme working conditions is simulated, thereby further improving the accuracy of the evaluation.

[0085] In addition, the inventors also found that the prior art did not take into account the wind load transmitted by the nacelle cover, and the load boundary conditions were not fully considered, resulting in inaccurate results. Therefore, the wind load was introduced to fully consider the load conditions actually borne by the nacelle truss, which can more accurately evaluate the ultimate strength of the nacelle truss; it overcomes the defect that the prior art of evaluating the ultimate strength of the truss of a wind turbine generator set did not establish a nacelle cover elastic support model and did not consider the wind load transmitted by the nacelle cover, resulting in inaccurate simulation calculation results.

[0086] See also Figure 5 As shown, Figure 5 Another method for evaluating the ultimate strength of a cabin truss provided in an embodiment of the present application is as follows: Figure 3 Based on the process shown, the maximum value of the equivalent stress of the cabin truss specifically includes: the maximum value of the equivalent stress of the weld, and the allowable stress value of the cabin truss specifically includes: the allowable stress value of the weld. The method specifically includes the following steps:

[0087] S501: Establish a finite element model consisting of a cabin cover, elastic supports, and cabin trusses.

[0088] S502: applying boundary conditions to the finite element model, and performing ultimate strength calculation on the finite element model based on the boundary conditions to obtain an ultimate strength calculation result.

[0089] S503: Determine, according to the ultimate strength calculation result, a first position corresponding to the maximum value of the weld equivalent stress under different working conditions.

[0090] In an embodiment of the present application, after performing the ultimate strength solution calculation, the equivalent stress cloud map of the cabin truss under different working conditions can be obtained through further post-processing. These cloud maps show the stress distribution of the entire cabin truss under different working conditions. Afterwards, the position of the maximum equivalent stress of the weld of the cabin truss under each working condition is taken as the first position. The first position is the position with the maximum stress in the weld and is a potential dangerous position of the weld. For example, from the stress cloud map, for the windward working condition, the crosswind working condition, and the leeward working condition, determine the first position A1 of the maximum equivalent stress of the weld under the windward working condition, determine the first position B1 of the maximum equivalent stress of the weld under the crosswind working condition, and determine the first position C1 of the maximum equivalent stress of the weld under the leeward working condition.

[0091] S504: For the first position under each working condition, the equivalent stress value of the second position that is a first distance away from the first position and the equivalent stress value of the third position that is a second distance away from the first position are respectively extracted, and the equivalent stress value of the first position is calculated according to the equivalent stress value of the second position and the equivalent stress value of the third position to obtain the equivalent stress value of the first position under each working condition.

[0092] The values ​​of the first distance and the second distance are different.

[0093] In an embodiment of the present application, for the first position under different working conditions, the position whose value is the first distance from the first position is determined to be the second position, the position whose value is the second distance from the first position is determined to be the third position, and the equivalent stress value of the second position is extracted to further determine the equivalent stress value of the first position, for example:

[0094] For the headwind condition, the equivalent stress value a2 of the second position A2 at the first distance from the first position A1 and the equivalent stress value a3 of the third position A3 at the second distance are extracted, and the equivalent stress value a1 of the first position A1 is determined based on a2 and a3.

[0095] For crosswind conditions, the equivalent stress value b2 of the second position B2 at a first distance from the first position B1 and the equivalent stress value b3 of the third position B3 at a second distance are extracted, and the equivalent stress value b1 of the first position B1 is determined based on b2 and b3.

[0096] For the leeward condition, the equivalent stress value c1 of the second position C2 at a first distance from the first position C1 and the equivalent stress value c3 of the third position C3 at a second distance are extracted, and the equivalent stress value c1 of the first position C1 is determined based on c2 and c3.

[0097] In some implementations of the embodiments of the present application, the equivalent stress values ​​at the positions 0.4t and 1.0t away from the weld toe are extracted and recorded as σ0.4t and σ1.0t, respectively, where t is the plate thickness at the position of the weld. Then, the equivalent stress value σ0t at the weld toe position is calculated by the linear extrapolation method, that is, the equivalent stress value at the 0t position. Specifically, the equivalent stress value at the weld toe position can be calculated using the following formula:

[0098] σ 0t =1.67×σ 0.4t -0.67×σ 1.0t

[0099] S505: Determine the maximum value among the equivalent stress values ​​at the first position under each working condition as the maximum value of the weld equivalent stress.

[0100] In an embodiment of the present application, the maximum value of the equivalent stress at the first position under each working condition is taken as the maximum value of the weld equivalent stress. For example, the maximum value is taken from a1 under the windward condition, b1 under the crosswind condition, and c1 under the leeward condition as the maximum value of the weld equivalent stress.

[0101] S506: Determine the allowable stress value of the weld according to the yield strength of the weld and the first material additional safety factor, and evaluate the ultimate strength of the cabin truss based on the allowable stress value of the weld and the maximum value of the weld equivalent stress.

[0102] In an embodiment of the present application, the yield strength of the weld is obtained by searching the material manual according to the thickness of the cabin truss weld at the location where the equivalent stress maximum value is located. For example, when the thickness at the weld location is 10 mm and the material type is Q345E, the corresponding yield strength is 345 MPa.

[0103] After that, the allowable stress value [σ] of the weld is calculated by the following formula:

[0104]

[0105] Where: Re is the yield strength; γm is the additional safety factor of the material, which is 1.1.

[0106] According to the above formula, when the thickness of the weld is 10 mm and the yield strength is 345 MPa, the allowable stress value of the cabin truss weld is 313.64 MPa.

[0107] exist Figure 5 In the process shown, the assessment is conducted from the perspective of welds. Welds, as locations where stress concentration is more obvious, are often weak points in structural strength. In the ultimate strength assessment of this application, by determining the maximum equivalent stress of the weld, the location where failure is most likely to occur can be directly found, thereby more specifically assessing the overall strength and safety of the cabin truss. Assessing the ultimate strength of the cabin truss based on the maximum equivalent stress of the weld and the allowable stress value of the weld can capture potential risks more accurately and effectively.

[0108] See also Figure 6 As shown, Figure 6 Another method for evaluating the ultimate strength of a cabin truss provided in an embodiment of the present application is as follows: Figure 3 Based on the process shown, the maximum value of the equivalent stress of the cabin truss specifically includes: the maximum value of the equivalent stress of the parent material, and the allowable value of the cabin truss specifically includes: the allowable value of the parent material. The method specifically includes the following steps:

[0109] S601: Establish a finite element model consisting of the cabin cover, elastic support and cabin truss.

[0110] S602: applying boundary conditions to the finite element model, and performing ultimate strength calculation on the finite element model based on the boundary conditions to obtain an ultimate strength calculation result.

[0111] S603: Determine the maximum value of the equivalent stress of the parent material under different working conditions according to the ultimate strength calculation result, and determine the maximum value among the maximum values ​​of the equivalent stress of the parent material under different working conditions as the maximum value of the equivalent stress of the parent material.

[0112] In an embodiment of the present application, after performing the ultimate strength solution calculation, the equivalent stress cloud diagram of the cabin truss under different working conditions can be obtained through further post-processing. Afterwards, the maximum value of the equivalent stress of the parent material of the cabin truss under different working conditions is determined, and the maximum value is selected as the maximum value of the equivalent stress of the parent material. For example, from the equivalent stress cloud diagram, for the windward working condition, the crosswind working condition, and the leeward working condition, the target maximum value of the equivalent stress d1 under the windward working condition is determined, the maximum value of the equivalent stress of the parent material under the crosswind working condition is determined d2, and the maximum value of the equivalent stress of the parent material under the leeward working condition is determined d3, and the maximum value is selected from d1, d2, and d3 as the maximum value of the equivalent stress of the parent material.

[0113] S604: Determine the allowable stress value of the parent material according to the yield strength of the parent material and the additional safety factor of the second material, and evaluate the ultimate strength of the cabin truss based on the allowable stress value of the parent material and the maximum value of the equivalent stress of the parent material.

[0114] In an embodiment of the present application, the yield strength of the parent material is obtained by searching the material manual according to the thickness of the cabin truss parent material at the location of the maximum equivalent stress. For example, when the thickness of the parent material is 30 mm and the material type is Q345E, the corresponding yield strength is 335 MPa.

[0115] After that, the allowable stress value [σ] of the weld is calculated by the following formula:

[0116]

[0117] Where: Re is the yield strength; γm is the additional safety factor of the material, which is 1.1.

[0118] According to the above formula, when the thickness of the parent material is 30 mm and the yield strength is 335 MPa, the allowable stress value of the parent material is 304.55 MPa.

[0119] exist Figure 6In the process shown, the ultimate strength of the cabin truss is evaluated from the perspective of the parent material. The parent material is usually the largest part of the entire structure, and its stress condition determines the overall strength of the truss. If the parent material is damaged, it may trigger a series of chain reactions, thus affecting the structural safety of the entire cabin truss. From the perspective of the parent material, the ultimate strength evaluation combined with the maximum equivalent stress of the parent material and the allowable stress value of the parent material can provide an accurate strength evaluation of the cabin truss.

[0120] See also Figure 7 As shown, Figure 7 Another method for evaluating the strength of a cabin truss provided in an embodiment of the present application is as follows: Figure 3 Based on the process shown, the maximum value of equivalent stress of the cabin truss specifically includes: the maximum value of equivalent stress of the weld and the maximum value of equivalent stress of the parent material, and the allowable value of the cabin truss specifically includes: the allowable value of the weld and the allowable value of the parent material, which specifically includes the following steps:

[0121] S701: Establish a finite element model consisting of the cabin cover, elastic support and cabin truss.

[0122] S702: applying boundary conditions to the finite element model, and performing ultimate strength calculation on the finite element model based on the boundary conditions to obtain an ultimate strength calculation result.

[0123] S703: Determine, according to the ultimate strength calculation result, a first position corresponding to the maximum value of the weld equivalent stress under different working conditions.

[0124] S704: For the first position under each working condition, the equivalent stress value of the second position that is a first distance away from the first position and the equivalent stress value of the third position that is a second distance away from the first position are respectively extracted, and the equivalent stress value of the first position is calculated according to the equivalent stress value of the second position and the equivalent stress value of the third position to obtain the equivalent stress value of the first position under each working condition.

[0125] S705: Determine the maximum value among the equivalent stress values ​​at the first position under each working condition as the maximum value of the weld equivalent stress.

[0126] S706: Determine the maximum value of the equivalent stress of the parent material under different working conditions according to the ultimate strength calculation result, and determine the maximum value among the maximum values ​​of the equivalent stress of the parent material under different working conditions as the maximum value of the equivalent stress of the parent material.

[0127] S707: Determine the allowable stress value of the weld according to the yield strength of the weld and the first material additional safety factor, and determine the allowable stress value of the parent material according to the yield strength of the parent material and the second material additional safety factor.

[0128] In the embodiments of the present application, Figure 6 The specific implementation of the process shown can be found in Figure 5 , 6 The process shown is not described in detail in this application.

[0129] S708: The ultimate safety factor of the weld is calculated based on the allowable stress value of the weld and the maximum value of the equivalent stress of the weld. The ultimate safety factor of the parent material is calculated based on the allowable stress value of the parent material and the maximum value of the equivalent stress of the parent material. The ultimate safety factor is used to evaluate the ultimate strength of the cabin truss.

[0130] In an embodiment of the present application, when the ultimate safety factor is used to evaluate the strength of the cabin truss, when the ultimate safety factor of the weld and the ultimate safety factor of the parent material are both greater than 1, it can be considered that the cabin truss meets the design requirements.

[0131] In some embodiments of the present application, when the load boundary conditions in the boundary conditions include a first action load obtained by superimposing the wind load on the windward side of the nacelle cover and the gravity load of the nacelle cover, a second action load obtained by superimposing the wind load on the leeward side of the nacelle cover and the gravity load of the nacelle cover, and a third action load obtained by superimposing the wind load on the parallel surface of the nacelle cover and the gravity load of the nacelle cover, the maximum value of the equivalent stress of the nacelle truss weld that can be calculated by the above method is σ 0t,Weld =295.42MPa, the maximum equivalent stress of the parent material is σ 0t,Edge =279MPa.

[0132] When the ultimate safety factor is used to evaluate the ultimate strength of the cabin truss, the ultimate safety factor of the cabin truss weld and parent material is calculated according to the following formula:

[0133]

[0134] For this embodiment, according to the above formula, it can be calculated that the ultimate safety factor of the cabin truss weld is 1.06, and the ultimate safety factor of the parent material is 1.09, both of which are greater than 1 and meet the design requirements.

[0135] exist Figure 7 In the process shown, the influence of welds and parent materials on the ultimate strength of the cabin truss is comprehensively considered. As the connection between different components of the cabin truss, the weld is usually a prone area of ​​stress concentration and fatigue failure; while the parent material is the main load-bearing part of the truss, occupying most of the volume and weight of the entire structure, and its strength directly determines the load-bearing capacity and structural safety of the truss. By calculating the maximum value of the equivalent stress and the allowable stress value of the weld and the parent material respectively, a double verification method is provided to ensure that the cabin truss can maintain safety and reliability under various complex working conditions. This double verification method can more comprehensively evaluate and respond to weak points and potential hidden dangers in the structure.

[0136] See also Figure 8As shown, the embodiment of the present application also provides an ultimate strength assessment system for a cabin truss, the system comprising: a cabin truss finite element modeling subsystem 801, a calculation model boundary condition loading calculation subsystem 802 and an ultimate strength assessment subsystem 803;

[0137] The cabin truss finite element modeling subsystem 801 is used to establish a finite element model consisting of a cabin cover, elastic support and cabin truss;

[0138] The calculation model boundary condition loading calculation subsystem 802 is used to apply boundary conditions to the finite element model, and perform ultimate strength calculation on the finite element model based on the boundary conditions to obtain ultimate strength calculation results;

[0139] The ultimate strength evaluation subsystem 803 is used to extract the maximum equivalent stress of the cabin truss from the ultimate strength calculation results; it is also used to determine the allowable stress value of the cabin truss, and calculate and evaluate the ultimate strength of the cabin truss based on the allowable stress value and the maximum equivalent stress value.

[0140] In some implementations of the embodiments of the present application, in the finite element model, the nacelle cover is meshed using shell elements, and the elastic support and the nacelle truss are meshed using solid elements;

[0141] In some implementations of the embodiments of the present application, the boundary conditions include: connection boundary conditions, constraint boundary conditions, and load boundary conditions;

[0142] Among them, the connection boundary condition is that the connection relationship between the cabin cover, elastic support and cabin truss is binding contact, the constraint boundary condition is the bottom full displacement constraint of the cabin truss, and the load boundary condition is the load transferred to the cabin truss by the cabin cover under multiple working conditions.

[0143] In some implementations of the embodiments of the present application, the applied load includes: wind load; the load boundary conditions include: wind load on the windward side of the nacelle cover, wind load on the leeward side of the nacelle cover, and wind load on the parallel side of the nacelle cover.

[0144] In some implementations of the embodiments of the present application, the acting load also includes: a gravity load, and the load boundary conditions include: a first acting load obtained by superimposing the wind load on the windward surface of the nacelle cover and the gravity load of the nacelle cover, a second acting load obtained by superimposing the wind load on the leeward surface of the nacelle cover and the gravity load of the nacelle cover, and a third acting load obtained by superimposing the wind load on the surface parallel to the nacelle cover and the gravity load of the nacelle cover.

[0145] In some implementations of the embodiments of the present application, the maximum value of the equivalent stress of the cabin truss includes: the maximum value of the equivalent stress of the weld, and the maximum value of the equivalent stress of the cabin truss is determined according to the ultimate strength calculation result, including:

[0146] According to the ultimate strength calculation results, determine the first position corresponding to the maximum value of the weld equivalent stress under different working conditions;

[0147] For the first position under each working condition, the equivalent stress value of the second position at a first distance from the first position and the equivalent stress value of the third position at a second distance from the first position are respectively extracted, and the equivalent stress value of the first position is calculated according to the equivalent stress value of the second position and the equivalent stress value of the third position, so as to obtain the equivalent stress value of the first position under each working condition;

[0148] The maximum value among the equivalent stress values ​​at the first position under each working condition is determined as the maximum equivalent stress value of the weld.

[0149] In some implementations of the embodiments of the present application, the maximum value of the equivalent stress of the cabin truss includes: the maximum value of the equivalent stress of the parent material, and the maximum value of the equivalent stress of the cabin truss is determined according to the ultimate strength calculation result, including:

[0150] According to the ultimate strength calculation results, the maximum value of the equivalent stress of the parent material under different working conditions is determined, and the maximum value among the maximum values ​​of the equivalent stress of the parent material under different working conditions is determined as the maximum value of the equivalent stress of the parent material.

[0151] In some implementations of the embodiments of the present application, the allowable stress value of the cabin truss includes: the allowable stress value of the weld, and determining the allowable stress value of the cabin truss includes:

[0152] The allowable stress value of the weld is determined based on the yield strength of the weld and the additional safety factor of the first material.

[0153] In some implementations of the embodiments of the present application, the allowable stress value of the cabin truss includes: the allowable stress value of the parent material, and determining the allowable stress value of the cabin truss includes:

[0154] The allowable stress value of the parent material is determined based on the yield strength of the parent material and the additional safety factor of the second material.

[0155] Finally, it should be noted that, in the embodiments of the present application, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements includes not only those elements, but also includes other elements that are not clearly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of more restrictions, the elements limited by the statement "comprise one..." do not exclude the presence of other identical elements in the process, method, article or equipment including the elements.

[0156] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for evaluating the ultimate strength of a cabin truss, characterized in that: The method comprises: Establish a finite element model consisting of the nacelle cover, elastic support and nacelle truss; Applying boundary conditions to the finite element model, and performing ultimate strength calculation on the finite element model based on the boundary conditions to obtain an ultimate strength calculation result; Determine the maximum value of equivalent stress of the cabin truss according to the ultimate strength calculation result; The allowable stress value of the cabin truss is determined, and the ultimate strength of the cabin truss is evaluated based on the allowable stress value and the maximum equivalent stress value.

2. The method according to claim 1, characterized in that In the finite element model, the nacelle cover is meshed using shell elements, and the elastic support and the nacelle truss are meshed using solid elements.

3. The method according to claim 1, characterized in that The boundary conditions include: connection boundary conditions, constraint boundary conditions and load boundary conditions; Among them, the connection boundary condition is that the connection relationship between the cabin cover, the elastic support and the cabin truss is binding contact, the constraint boundary condition is the bottom full displacement constraint of the cabin truss, and the load boundary condition is the acting load transmitted to the cabin truss by the cabin cover under multiple working conditions.

4. The method according to claim 3, characterized in that The action load includes: wind load; the load boundary conditions include: wind load on the windward surface of the nacelle cover, wind load on the leeward surface of the nacelle cover, and wind load on the parallel surface of the nacelle cover.

5. The method according to claim 4, characterized in that The acting load also includes: a gravity load, and the load boundary conditions include: a first acting load obtained by superimposing the wind load on the windward surface of the nacelle cover and the gravity load of the nacelle cover, a second acting load obtained by superimposing the wind load on the leeward surface of the nacelle cover and the gravity load of the nacelle cover, and a third acting load obtained by superimposing the wind load on the parallel surface of the nacelle cover and the gravity load of the nacelle cover.

6. The method according to claim 2, characterized in that The maximum value of the cabin truss equivalent stress includes: the maximum value of the weld equivalent stress, and the determination of the maximum value of the cabin truss equivalent stress according to the ultimate strength calculation result includes: According to the ultimate strength calculation result, determining the first position corresponding to the maximum value of the weld equivalent stress under different working conditions; For the first position under each working condition, the equivalent stress value of the second position at a first distance from the first position and the equivalent stress value of the third position at a second distance from the first position are respectively extracted, and the equivalent stress value of the first position is calculated according to the equivalent stress value of the second position and the equivalent stress value of the third position, so as to obtain the equivalent stress value of the first position under each working condition; The maximum value among the equivalent stress values ​​of the first position under the various working conditions is determined as the maximum value of the weld equivalent stress.

7. The method according to claim 2, characterized in that The maximum value of the equivalent stress of the cabin truss includes: the maximum value of the equivalent stress of the parent material, and the determination of the maximum value of the equivalent stress of the cabin truss according to the ultimate strength calculation result includes: According to the ultimate strength calculation result, the maximum value of the equivalent stress of the parent material under different working conditions is determined, and the maximum value among the maximum values ​​of the equivalent stress of the parent material under the different working conditions is determined as the maximum value of the equivalent stress of the parent material.

8. The method according to claim 1, characterized in that The allowable stress value of the cabin truss includes: the allowable stress value of the weld, and the determination of the allowable stress value of the cabin truss includes: The allowable stress value of the weld is determined based on the yield strength of the weld and the additional safety factor of the first material.

9. The method according to claim 1, characterized in that: The allowable stress value of the cabin truss includes: the allowable stress value of the parent material, and the determination of the allowable stress value of the cabin truss includes: The allowable stress value of the parent material is determined based on the yield strength of the parent material and the additional safety factor of the second material.

10. An ultimate strength assessment system for a cabin truss, characterized in that: The system comprises: a cabin truss finite element modeling subsystem, a calculation model boundary condition loading calculation subsystem and an ultimate strength evaluation subsystem; The cabin truss finite element modeling subsystem is used to establish a finite element model consisting of a cabin cover, elastic supports and a cabin truss; The calculation model boundary condition loading calculation subsystem is used to apply boundary conditions to the finite element model, and perform ultimate strength solution calculation on the finite element model based on the boundary conditions to obtain ultimate strength calculation results; The ultimate strength assessment subsystem is used to extract the maximum equivalent stress value of the cabin truss from the ultimate strength calculation results; it is also used to determine the allowable stress value of the cabin truss, and calculate and assess the ultimate strength of the cabin truss based on the allowable stress value and the maximum equivalent stress value.

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