CN113435081A - Non-penetration weld static strength evaluation method based on structural stress and Eurocode3 standard - Google Patents
Non-penetration weld static strength evaluation method based on structural stress and Eurocode3 standard Download PDFInfo
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Abstract
The invention provides a non-penetration weld static strength evaluation method based on structural stress and Eurocode3 standard, which comprises the following steps: s1, importing the overall structure geometry file into finite element software, and carrying out finite element meshing; s2, defining a weak section of the concerned main bearing welding seam; s3, obtaining a complete finite element calculation model; s4, obtaining the worst load as the structural load applied during model solution; s5, after the model is solved, extracting the node force on each main bearing weld weak section, and calculating the structural stress in three directions on the weak section; s6, extracting film stress components of the structural stress in three directions, and calculating the synthetic stress; s7, calculating allowable stress of each concerned welding line; s8, comparing the calculated resultant stress of each weak section with the corresponding allowable welding seam stress, and judging whether the welding seam strength meets the requirement; if the requirements are not met, the joint design is carried out again, and the steps S1-S8 are repeated.
Description
Technical Field
The invention relates to a non-penetration weld static strength evaluation method based on structural stress and a Eurocode3 standard.
Background
The welded joints in complex engineering structures often have the characteristics of low strength and complex stress state. In the case of a penetration joint, the strength is generally at or near that of the parent material. However, there are also a number of non-fusion joints in conventional engineered structures, such as fillet joints, single-sided butt joints, slab joints, and the like. If the size of the welded joint is insufficient, the ultimate bearing capacity of the joint is far lower than that of the parent metal, so that the safety of the whole structure is obviously affected, and important attention should be paid to joint design and structural strength evaluation.
For the strength evaluation of the non-penetration joint, a calculation formula which can be used for a simple joint exists in the prior art, and more weld strength evaluation methods for joint size design provided in steel structure design standards are applied in engineering. Typical of these are the fillet strength evaluation formulas in the Eurocode3 standard. However, the shapes and stress states of a large number of joints in an actual engineering structure are very complex, and the weld stress is difficult to calculate accurately, so that great difficulty is brought to engineering application of the method, and hidden dangers are buried for structural safety.
Disclosure of Invention
According to the proposed non-penetration weld static strength evaluation method based on the structural stress and the Eurocode3 standard, the shapes and stress states of a large number of joints in an actual engineering structure are very complex, the weld stress is difficult to calculate accurately, and great difficulty is brought to engineering application of the method, so that the technical problem of hidden danger of structural safety is solved. The method mainly extracts the node force on each main bearing weld weak section by defining the weak section and combining finite element analysis, calculates the structural stress in three directions on the weak section by using a structural stress method, extracts the film stress components of the structural stress in the three directions, calculates the synthetic stress, and compares the calculated synthetic stress of each weak section with the corresponding allowable weld stress to judge whether the weld strength meets the requirement, thereby overcoming the limitation of the Eurocode3 standard, accurately calculating the stress on the weld section, and enabling the weld strength calculation formula of the Eurocode3 standard to be used for complex engineering structures and have wide engineering application value.
The technical means adopted by the invention are as follows:
a non-penetration weld static strength evaluation method based on structural stress and Eurocode3 standards comprises the following steps:
s1, importing the overall structure geometry file in the format of step or iges and the like into finite element software, and geometrically dividing finite element meshes for the structure by utilizing the preprocessing function of the software;
s2, related units and nodes are designated according to the requirements of the structural stress method, and the minimum section of the concerned welding seam is defined as a weak section;
s3, defining the element type and material parameters of the finite element mesh of the structure, and applying constraint conditions which accord with the stress state of the structure, thereby obtaining a complete finite element calculation model;
s4, obtaining the worst load as the structural load applied during model solution;
s5, after solving the model by using finite element software, extracting the node force on the weak section of each main bearing weld joint, and calculating the structural stress in three directions on the weak section by using a structural stress method;
s6, extracting film stress components of structural stress in three directions, and calculating the synthetic stress as three weld stresses in the Eurocode3 standard;
s7, according to the specification of the Eurocode3 standard, calculating the allowable stress of each concerned welding line according to the type and the ultimate strength value of the base metal connected with the welding joint;
s8, comparing the calculated resultant stress of each weak section with the corresponding allowable welding seam stress, and judging whether the welding seam strength meets the requirement; if the requirements are not met, the joint design is carried out again, and the steps S1-S8 are repeated.
Further, in step S1, the finite element software is a common commercial software such as ANSYS, Patran/nanostran, Abaqus or Hypermesh.
Further, in step S1, the solid elements are used when the finite element mesh is divided, and the connection relationship of the mesh nodes near the non-penetration weld is noticed to accurately simulate the force transfer characteristics of the joint position.
Further, in step S4, the worst loads are selected from the structural loads specified in the calculation outline compiled during structural design or the relevant industry standards.
Further, in step S5, the method for calculating the structural stress in three directions on the weak cross section includes the following specific steps:
s51, extracting the unit node force of the finite element result on the weak section of each main bearing weld joint;
s52, respectively and equivalently converting the node force of each row of nodes into the node force F on the section center line along the length direction of the sectioniBending moment M of the jointi；
S53, based on the principle of balance-equivalence, connecting the node force FiBending moment M of the jointiAlong the length direction of the weld into a linear force fiBending moment m of linei；
And S54, calculating the normal structural stress at each node of the section and the shear structural stress in two directions.
Further, in the step S54, the calculation solution of the normal structural stress at each node of the cross section satisfies the following formula:
wherein, sigma is normal structure stress and comprises two components of membrane stress and bending stress; t is the plate thickness; sigmamNormal film stress; sigmabIs normal bending stress, fxIs a linear force in the x direction, mzIs the z-direction line bending moment.
Further, in the step S54, the calculation solution of the shear structural stress in two directions satisfies the following formula:
in the formula, τLThe stress of the in-plane shearing structure comprises two components of film stress and bending stress; t is the plate thickness; tau isLmFor longitudinal shear of film stress, τLbFor longitudinal shear bending stress, fzIs a linear force in the z direction, mxIs a line bending moment in the x direction;
τTthe structural stress is sheared in the thickness direction, and only the film stress component can be calculated; tau isTmFor transverse shear of film stress, fyIs the y-direction line force.
Further, in the step S6, the stress σ is synthesizedCombination of Chinese herbsThe following formula in the Eurocode3 standard was used for the calculation of (c):
in the formula: sigmaCombination of Chinese herbsTo synthesize stress, σ⊥For normal stress, τ⊥For transverse shear stress, τ//Is the longitudinal shear stress; wherein each stress component is a stress value on the minimum section of the welding seam; according to the corresponding relation between each stress component and the structural stress component, sigma⊥、τ⊥And τ//Using respectively sigmam、τTmAnd τLmThe value of (c).
Further, in the step S8, when the combined stress of each weak section is not greater than the allowable stress of the weld, the weld strength is satisfied.
Further, in step S8, when the weld strength is satisfied, the following formula is satisfied between the resultant stress of each weak section and the corresponding allowable weld stress:
In the formula: f. ofuNominal tensile strength of the parent material of the weak part for joint connection; beta is awIs a correlation factor corresponding to the type of steel; r isM2Is a coefficient of partial term, rM21.25; wherein the content of the first and second substances,
is a calculation formula of allowable stress.
Compared with the prior art, the invention has the following advantages:
1. the non-penetration weld static strength evaluation method based on the structural stress and the Eurocode3 standard overcomes the limitation of the Eurocode3 standard, can accurately calculate the stress on the section of a weld, enables the weld strength calculation formula of the Eurocode3 standard to be used for complex engineering structures, and has wide engineering application value.
2. The non-penetration weld static strength evaluation method based on the structural stress and the Eurocode3 standard can evaluate the strength of any section of a weld through a flexible finite element meshing technology so as to adapt to the stress condition with a complex actual structure.
3. According to the non-penetration weld static strength evaluation method based on the structural stress and the Eurocode3 standard, due to the structural stress method, the fatigue performance of the weld section can be evaluated by using a main S-N curve method, and the calculation efficiency is improved.
In conclusion, the technical scheme of the invention can solve the problems that the shapes and stress states of a large number of joints in an actual engineering structure are very complex, the welding line stress is difficult to calculate accurately, great difficulty is brought to engineering application of the method, and therefore hidden danger is buried for structural safety.
Based on the above reasons, the method can be widely popularized in the fields of non-penetration weld static strength evaluation of the welded joint and the like.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a schematic diagram of weld stress definition of a weak section in the Eurocode3 standard in the prior art.
FIG. 2 is a diagram illustrating the structural stress definition of the weld toe cross section of the present invention, wherein (a) is the local stress of the finite element, (b) is the structural stress, and (c) is the self-balancing stress.
Fig. 3 is a schematic diagram of the transformation of nodal force of the weld toe cross section based on the balance-equivalence principle of the present invention, wherein (a) is a map of weld line positions and (b) is a graph of nodal force transformation.
Fig. 4 is a schematic diagram of the geometry and stress of the oil cylinder support in embodiment 1 of the present invention, in which (a) is a geometric structural diagram, and (b) is a schematic diagram of the stress.
FIG. 5 is a schematic view showing details of a welded joint and dimensions of a weld in example 1 of the present invention, wherein (a) is a schematic view showing a structure of a joint I, (b) is a dimension of a weld I in the joint I in mm, (c) is a schematic view showing a structure of a joint II, and (d) is a dimension of a weld II in the joint II in mm.
FIG. 6 is a partial grid and cross-sectional definition of a key weld in example 1 of the present invention, wherein (a) is weld I and (b) is weld II.
Fig. 7 is a cloud chart of stresses near a key weld in example 1 of the present invention, where (a) is a cloud chart of stresses near a weld i, and (b) is a cloud chart of stresses near a weld ii.
FIG. 8 is a stress distribution diagram of a section of each weld in example 1 of the present invention, wherein (a) is a stress distribution of section I in weld I, (b) is a stress distribution of section II in weld I, (c) is a stress distribution of section I in weld II, and (d) is a stress distribution of section II in weld II.
In the figure: 1. a plate I; 2. a plate II; 3. a guide wheel; 4. a guide wheel plate; 5. a section I; 6. section II.
Detailed Description
It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
The relative arrangement of the components and steps, the numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise. Meanwhile, it should be understood that the sizes of the respective portions shown in the drawings are not drawn in an actual proportional relationship for the convenience of description. Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate. Any specific values in all examples shown and discussed herein are to be construed as exemplary only and not as limiting. Thus, other examples of the exemplary embodiments may have different values. It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, further discussion thereof is not required in subsequent figures.
The static strength evaluation of the non-penetration weld in the Eurocode3 standard was performed in four steps:
(1) calculating allowable stress according to a subentry coefficient specified by a standard, a correlation factor corresponding to the material type and the strength of the parent metal;
(2) selecting a minimum cross section of the non-penetration weld;
(3) calculating the stress in three directions on the minimum section of the welding seam, namely normal stress and shear stress in two directions;
(4) the resultant stress is calculated according to the formula provided in the standard (see formula (1) below) and compared with the allowable stress specified by the standard.
In the formula: f. ofuNominal tensile strength of the parent material of the weak part for joint connection; beta is awIs a correlation factor corresponding to the type of steel; r isM2Is a coefficient of partial term (r)M2＝1.25)；σ⊥Is normal stress; tau is⊥Is the transverse shear stress; tau is//Is the longitudinal shear stress. In addition, each stress component in the formula is a stress value on the minimum section of the weld joint, and the definition of the stress value is shown in fig. 1.
However, in the Eurocode3 standard, only weld stress definition on the minimum section is given, and no method is given for accurately calculating the stress of a weld section in a complex engineering structure. The weld strength evaluation method in the Eurocode3 standard has two major problems in engineering applications:
(1) the shapes and stress states of a large number of joints in an actual engineering structure are very complicated, and accurate calculation of weld stress becomes very difficult. The finite element numerical method is a common method for calculating the stress state of a complex structure in engineering, but the method outputs node stress which is not consistent with the stress definition of fig. 1, so that if the stress calculation is not appropriate, the strength evaluation cannot be directly carried out by using the formula (1).
(2) Numerous tests have shown that the failure location of a weld is not necessarily at the smallest cross-section of the weld, and therefore an evaluation of other possible weak cross-sections is also required.
In order to overcome the difficulties and accurately calculate the stress on the section of the weld joint, so that a weld joint strength calculation formula of a Eurocode3 standard can be used for a complex engineering structure, the invention provides a non-penetration weld joint static strength evaluation method based on the structural stress and the Eurocode3 standard.
As shown in the figure, the invention provides a non-penetration weld static strength evaluation method based on structural stress and a Eurocode3 standard, which comprises the following steps:
s1, importing the overall structure geometry file in the format of step or iges and the like into finite element software, and geometrically dividing finite element meshes for the structure by utilizing the preprocessing function of the software;
s2, related units and nodes are designated according to the requirements of the structural stress method, and the minimum section of the concerned welding seam is defined as a weak section (namely, the weak section of the concerned main bearing welding seam is defined by designating a proper unit set and a proper node set);
s3, defining the element type and material parameter of the structure finite element grid (determined according to the actual structure and the used software), and applying the constraint condition (the structure constraint applied in the finite element calculation) according with the stress state of the structure, thereby obtaining a complete finite element calculation model;
s4, obtaining the worst load as the structural load applied during model solution;
s5, after solving the model by using finite element software, extracting the node force on each main bearing weld weak section, and calculating the structural stress in three directions on the weak section by using a structural stress method and a related post-processing program (software calculation tool);
s6, extracting film stress components of structural stress in three directions, and calculating the synthetic stress as three weld stresses in the Eurocode3 standard;
s7, according to the specification of the Eurocode3 standard, calculating the allowable stress of each concerned welding line according to the type and the ultimate strength value (material performance parameters, the specification of the existing standard) of the base material connected with the welding joint;
s8, comparing the calculated resultant stress of each weak section with the corresponding allowable welding seam stress, and judging whether the welding seam strength meets the requirement; if the requirements are not met, the joint design is carried out again, and the steps S1-S8 are repeated.
In a preferred embodiment, the finite element software in step S1 is a common commercial software such as ANSYS, Patran/nanostran, Abaqus or Hypermesh.
In a preferred embodiment, in step S1, solid elements are used in the division of the finite element mesh, and the connection relationship of mesh nodes near the non-penetration weld is noted to accurately simulate the force transfer characteristics of the joint position.
In a preferred embodiment, in step S4, the worst loads are selected from structural loads specified in a calculation outline compiled during structural design or a relevant industry standard (industry to which the actual structure belongs).
In a preferred embodiment, the method for calculating the structural stress in three directions on the weak cross section in step S5 (structural stress method) specifically includes the following steps:
s51, extracting the unit node force of the finite element result on the weak section of each main bearing weld joint;
s52, respectively and equivalently converting the node force of each row of nodes into the node force F on the section center line along the length direction of the sectioniBending moment M of the jointi；
S53, based on the principle of balance-equivalence, connecting the node force FiBending moment M of the jointiAlong the length direction of the weld into a linear force fiBending moment m of linei；
And S54, calculating the normal structural stress at each node of the section and the shear structural stress in two directions.
In a preferred embodiment, in step S54, the calculation of the normal structural stress at each node of the cross section satisfies the following formula:
wherein, sigma is normal structure stress and comprises two components of membrane stress and bending stress; t is the plate thickness; sigmamNormal film stress; sigmabIs normal bending stress, fxIs a linear force in the x direction, mzIs the z-direction line bending moment.
In a preferred embodiment, in step S54, the calculation solution of the shear structural stress in two directions satisfies the following formula:
in the formula, τLThe stress of the in-plane shearing structure comprises two components of film stress and bending stress; t is the plate thickness; tau isLmFor longitudinal shear of film stress, τLbFor longitudinal shear bending stress, fzIs a linear force in the z direction, mxIs a line bending moment in the x direction;
τTthe structural stress is sheared in the thickness direction, and only the film stress component can be calculated; tau isTmFor transverse shear of film stress, fyIs the y-direction line force.
In a preferred embodiment, in step S6, the calculation solution of the composite stress satisfies the following formula:
in the formula: sigmaCombination of Chinese herbsTo synthesize stress, σ⊥For normal stress, τ⊥For transverse shear stress, τ//Is the longitudinal shear stress; in which each stress component (σ)⊥、τ⊥、τ//) The stress value on the minimum section of the welding seam; according to the corresponding relation between each stress component and the structural stress component, sigma⊥、τ⊥And τ//Using respectively sigmam、τTmAnd τLmThe value of (c).
In a preferred embodiment, in step S8, when the combined stress of each weak section is not greater than (reaches or approaches) the allowable stress of the corresponding weld, the weld strength is satisfied.
In a preferred embodiment, in step S8, when the weld strength is satisfied, the following formula is satisfied between the combined stress of each weak section and the corresponding allowable weld stress:
In the formula: f. ofuNominal tensile strength of the parent material of the weak part for joint connection; beta is awIs a correlation factor corresponding to the type of steel; r isM2Is a coefficient of partial term, rM21.25; wherein the content of the first and second substances,
is a calculation formula of allowable stress.
Specifically, in the above structural stress method, the stress on the cross section is decomposed into a linear stress portion (e.g., (b) of fig. 2) and a high-order self-balancing stress portion (e.g., (c) of fig. 2), and the linear stress portion is referred to as a structural stress, and the linear stress can be decomposed into two portions, namely, a film stress and a bending stress.
The structural stress of one section contains 3 components in total of normal stress and shear stress in two directions. Unlike the conventional finite element stress calculation method, the structural stress is calculated using the element node force in the finite element result.
Taking the weld toe section structure stress as an example, the calculation steps by using the three-dimensional solid model are as follows:
(1) extracting unit node force of a finite element result of the section of the welding toe;
(2) respectively and equivalently converting the node force of each row of nodes into node force F on a section central line along the length direction of the sectioniBending moment M of the jointi(see FIG. 3);
(3) based on the principle of balance-equivalence, the node force FiBending moment M of the jointiAlong the length direction of the weld into a linear force fiBending moment m of linei；
(4) And finally, calculating the normal structural stress at each node of the section of the weld toe by using a formula (2). In addition, with a similar process, the shear structural stress in two directions can be obtained by formula (3) and formula (4):
in the above formula, σ is the normal structural stress, τLIs an in-plane shear structural stress, both of which contain two components, film stress and bending stress, τTThe structural stress is sheared in the thickness direction, and only the film stress component can be calculated; t is the plate thickness; sigmamIs normal film stress, σbIs normal bending stress, fxIs a linear force in the x direction, mzIs a line bending moment in the z direction; tau isLmFor longitudinal shear of film stress, τLbFor longitudinal shear bending stress, fzIs a linear force in the z direction, mxIs a line bending moment in the x direction; tau isTmFor transverse shear of film stress, fyIs the y-direction line force.
A large amount of documents prove that the structural stress has grid insensitivity, and a main S-N curve method based on the structural stress is absorbed by a plurality of international standards such as ASME and the like and is widely applied to practical engineering. It should be noted that fatigue evaluation of a welded joint generally takes into account only normal structural stresses (including film and bending components), and shear stresses only when their values are large. In addition, it can be seen by comparison that the weld stress in fig. 1 is actually consistent with the film stress component definition in structural stress, and both represent the average stress in the cross-sectional thickness direction. Therefore, after only three directions of structural membrane stress are obtained, the strength of the welding seam can be evaluated as three welding seam stresses in the formula (1).
Example 1
As shown in fig. 4-8, the embodiment performs strength analysis on the key weld of the oil cylinder support of the special car for road and rail combined transport and piggyback transport, and proves the effectiveness of the non-penetration weld static strength evaluation method based on the structural stress and Eurocode3 standard.
The special vehicle for road-rail combined piggyback transport is a special railway vehicle designed for transporting road trucks. The oil cylinder support is one of key bearing parts in the structure, and the material type is weathering resistant steel Q450NQR 1. The geometry and forces are shown in figure 4 below. F in FIG. 4 (b)H1、FH2、FV1、FV2Respectively the load experienced at each location.
Under normal conditions, the oil cylinder support structure is mainly under the load action at 4 positions, and the guide wheel 3 is not obviously stressed, namely the guide wheel load FD can be ignored. However, due to factors such as manufacturing errors, the camel-back car can see that the oil cylinder support is obviously deformed due to huge contact force between the guide wheel and the guide rail in the using process, and the stress state is worse. Therefore, in order to guarantee the operational safety of piggyback cars, the limit value of the guide wheel load is estimated here by means of a strength analysis of the critical weld seams in the structure, taking into account the guide wheel load FD.
In this embodiment, the non-penetration weld static strength evaluation method based on the structural stress and the Eurocode3 standard specifically includes the following calculation procedures:
(1) and importing the oil cylinder support structure geometry file in the step format into Hypermesh software. According to the stress state of the oil cylinder support, the most critical can be judged on the welding joints between the guide wheel plate 4 and the plate I1 and between the plate I and the plate II 2 in fig. 4, the welding joint between the guide wheel plate 4 and the plate I1 is called as a joint I, and the welding joint between the plate I1 and the plate II 2 is called as a joint II. The two joint details and weld sizes are shown in fig. 5. Wherein, the plate II 2 and the guide wheel plate 4 are respectively thick plates with the thickness of 30mm and 40mm and cannot be welded through.
(2) The position of the dangerous weld joint in each joint can be judged according to the stress characteristics of the structure as shown in figure 5. Here, structural stress calculations and strength evaluations were performed for two sections of each weld starting from the root. It should be noted that, according to the geometry of the weld shown in fig. 5, the minimum cross-sections of the two welds are not section i 5 and section ii 6, but are inside the weld. However, since the minimum cross section is very different from the cross section i, the evaluation of the minimum cross section is replaced by the cross section i here for convenience.
(3) And dividing the finite element mesh according to the geometric file of the structure. In order to improve the calculation accuracy and facilitate the calculation of the structural stress of the weak section of the weld joint, the overall structure is modeled by using a fine solid unit, wherein two plates at each welding joint position are connected only through the weld joint unit (as shown in fig. 6).
(4) The 4 structural loads and guide wheel loads were applied to the model and finite element calculations were performed. It should be noted that the guide wheel load is unknown and trial and error is required until the resultant stress of the weakened section reaches or approaches the allowable stress. After a plurality of calculations, two key weld-vicinity stress clouds are given at a guide wheel load of 30t, as shown in fig. 7.
(5) And extracting the node force on the weak section of each main bearing weld joint, calculating the structural stress in three directions on the weak section by using a relevant post-processing program, extracting the film stress component, and substituting the film stress component into a Eurocode3 formula (1) to calculate the synthetic stress. The distribution of the stress of each section along the length direction of the weld is shown in fig. 8:
from the stress calculation results in fig. 8, it can be found that the distribution of the stress is very uneven along the length direction of the weld, and it is difficult to calculate by a general formula, which proves the necessity of using a numerical method.
(6) The allowable stress of the weld is utilized. The parent material type is weathering steel Q450NQR1, the nominal ultimate strength is 550MPa, according to the Eurocode3 standard, for this type of material, betaw1.0, the allowable stress on the right side of equation (1) is therefore 550/1.25-440 MPa.
(7) From the above calculation results, it can be seen that the maximum resultant stress is 403MPa on the section i of the weld ii, which is already close to the allowable stress (440MPa), and therefore, if a certain safety factor is considered, the limit value of the guide wheel load can be estimated to be slightly greater than 30 t.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. A non-penetration weld static strength assessment method based on structural stress and Eurocode3 standards is characterized by comprising the following steps:
s1, importing the integral structure geometry file in the step or iges format into finite element software, and geometrically dividing finite element meshes for the structure by utilizing the preprocessing function of the software;
s2, units and nodes are designated according to the requirements of the structural stress method, and the minimum section of the concerned welding seam is defined as a weak section;
s3, defining the element type and material parameters of the finite element mesh of the structure, and applying constraint conditions which accord with the stress state of the structure, thereby obtaining a complete finite element calculation model;
s4, obtaining the worst load as the structural load applied during model solution;
s5, after solving the model by using finite element software, extracting the node force on the weak section of each main bearing weld joint, and calculating the structural stress in three directions on the weak section by using a structural stress method;
s6, extracting film stress components of structural stress in three directions, and calculating the synthetic stress as three weld stresses in the Eurocode3 standard;
s7, according to the specification of the Eurocode3 standard, calculating the allowable stress of each concerned welding line according to the type and the ultimate strength value of the base metal connected with the welding joint;
s8, comparing the calculated resultant stress of each weak section with the corresponding allowable welding seam stress, and judging whether the welding seam strength meets the requirement; if the requirements are not met, the joint design is carried out again, and the steps S1-S8 are repeated.
2. The method for non-penetration weld static strength assessment based on structural stress and Eurocode3 standard according to claim 1, wherein in step S1, the finite element software is ANSYS, Patran/nanostran, Abaqus or Hypermesh.
3. The method for non-penetration weld static strength assessment based on structural stress and Eurocode3 standard according to claim 1, wherein in step S1, solid elements are used in the division of the finite element mesh, and the connection relationship of mesh nodes near the non-penetration weld is noted to accurately simulate the force transfer characteristics of the joint position.
4. The method for non-penetration weld static strength assessment based on structural stress and Eurocode3 standard according to claim 1, wherein in step S4, the worst loads are selected from the structural loads specified in the calculation schema compiled at the time of structural design or related industry standards.
5. The non-penetration weld static strength evaluation method based on the structural stress and the Eurocode3 standard according to claim 1, wherein the method for calculating the three-directional structural stress on the weak section in the step S5 comprises the following specific steps:
s51, extracting the unit node force of the finite element result on the weak section of each main bearing weld joint;
s52, respectively and equivalently converting the node force of each row of nodes into the node force F on the section center line along the length direction of the sectioniBending moment M of the jointi；
S53, based on the principle of balance-equivalence, connecting the node force FiBending moment M of the jointiAlong the length direction of the weld into a linear force fiBending moment m of linei；
And S54, calculating the normal structural stress at each node of the section and the shear structural stress in two directions.
6. The method for evaluating the static strength of the non-penetration weld based on the structural stress and the Eurocode3 standard according to claim 5, wherein in the step S54, the calculation solution of the normal structural stress at each node of the section satisfies the following formula:
wherein, sigma is normal structure stress and comprises two components of membrane stress and bending stress; t is the plate thickness; sigmamNormal film stress; sigmabIs normal bending stress, fxIs a linear force in the x direction, mzIs the z-direction line bending moment.
7. The method for evaluating the static strength of the non-penetration weld based on the structural stress and the Eurocode3 standard according to claim 5, wherein the calculation solution of the shear structural stress in two directions in the step S54 satisfies the following formula:
in the formula, τLThe stress of the in-plane shearing structure comprises two components of film stress and bending stress; t is the plate thickness; tau isLmFor longitudinal shear of film stress, τLbFor longitudinal shear bending stress, fzIs a linear force in the z direction, mxIs a line bending moment in the x direction;
τTthe structural stress is sheared in the thickness direction, and only the film stress component can be calculated; tau isTmFor transverse shear of film stress, fyIs the y-direction line force.
8. The method for non-penetration weld static strength assessment based on structural stress and Eurocode3 standard according to claim 1, wherein in the step S6, the stress σ is synthesizedCombination of Chinese herbsThe following formula in the Eurocode3 standard was used for the calculation of (c):
in the formula: sigmaCombination of Chinese herbsTo synthesize stress, σ⊥For normal stress, τ⊥For transverse shear stress, τ//Is the longitudinal shear stress; wherein each stress component is a stress value on the minimum section of the welding seam; according to the corresponding relation between each stress component and the structural stress component, sigma⊥、τ⊥And τ//Using respectively sigmam、τTmAnd τLmThe value of (c).
9. The non-penetration weld static strength evaluation method based on the structural stress and the Eurocode3 standard according to claim 1, wherein in the step S8, the weld strength is satisfied when the resultant stress of each weak section is not greater than the corresponding allowable weld stress.
10. The non-penetration weld static strength evaluation method based on the structural stress and the Eurocode3 standard according to claim 1 or 9, wherein in the step S8, when the weld strength meets the requirement, the following formula is satisfied between the resultant stress of each weak section and the corresponding allowable weld stress:
In the formula: f. ofuNominal tensile strength of the parent material of the weak part for joint connection; beta is awIs a correlation factor corresponding to the type of steel; r isM2Is a coefficient of partial term, rM21.25; wherein the content of the first and second substances,
is a calculation formula of allowable stress.
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