CN116502501B - Method and device for predicting limit strain capacity of girth weld of high-grade steel pipeline - Google Patents
Method and device for predicting limit strain capacity of girth weld of high-grade steel pipeline Download PDFInfo
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Abstract
The invention provides a method and a device for predicting limit strain capacity of girth welds of high-grade steel pipelines, which are characterized in that the method comprises the following steps: establishing a near field dynamics-finite element coupling model; applying a load boundary condition; based on a finite element user dynamic subroutine module in finite element software ABAQUS, a user-defined subroutine is utilized to realize a proposed near field dynamics-finite element coupling model, the near field dynamics-finite element coupling model is calculated, and the limit strain capacity of the girth weld of the high-steel pipeline is predicted. The invention can realize the simulation of the real process of crack propagation and the accurate prediction of the limit strain capacity of the circumferential weld of the pipeline, and can provide scientific basis for the evaluation of the limit strain capacity of the circumferential weld of the high-grade steel pipeline.
Description
Technical Field
The invention relates to the technical field of elastoplastic metal materials, in particular to a method and a device for predicting limit strain capacity of girth welds of high-grade steel pipelines.
Background
In order to improve the natural gas delivery and the economical efficiency of pipeline delivery, pipeline engineering is developing towards high-grade steel, large-caliber and high-pressure delivery. With the application of the high-grade steel pipeline with the grade of X80 or more and the high-initiation period of failure of old and old pipelines in service, the girth weld cracking becomes a main factor of pipeline failure, the welding process causes the defects of material performance degradation, welding crack generation and the like of a girth weld area, and when the pipeline passes through a geological disaster multi-occurrence area, local strain concentration is caused to crack under the displacement effect, so that the strain capacity of the pipeline is restricted. How to evaluate the ultimate strain capacity of girth welds becomes a new problem in the control of pipe breaks. The current empirical formula aiming at the strain capacity of the pipeline is mostly based on finite element calculation, but the problem of discontinuous crack propagation cannot be effectively solved when the traditional finite element method solves the problem of crack propagation, and complicated external failure criteria are additionally introduced to judge the occurrence of fracture, so that the calculation efficiency is low, the difficulty is high, and the evaluation of the strain capacity is influenced. The numerical calculation method suitable for the analysis of the crack propagation failure of the girth weld of the high-grade steel pipeline is required to be provided, and is also a scientific problem to be solved urgently for the high-grade steel natural gas pipeline.
Near field dynamics (PD) is an emerging computing method in the form of non-local, grid-free particles, integral for the last two decades. The method discretizes the material model into object points with physical information, so that constitutive relation of the model is still effective at medium discontinuity. The theory holds that there is an interaction between each material point and other material points in its near field domain. The most significant advantages of PD theory are: the singularities and complexities of traditional models based on continuous theory in solving the discontinuity problem are avoided, and the damage and fractures are directly contained in the constitutive relationship as the natural result of the simulation. Therefore, along with the progress of the simulation process, crack initiation and propagation phenomena are generated, and the whole process of crack initiation and propagation can be simulated without any additional criteria. PD method development has been applied to the areas of rock, composite fiber brittleness and micro elastic material damage fracture, based on bond-based mechanism elongation failure criteria: the relationship between the elongation and the force density between the particles is linear, and when the elongation after deformation reaches the ultimate elongation s 0 If so, the process is not reversible. However, for most metals, damage is often accompanied by plastic deformation, which, unlike elastic deformation, depends on the loading history, and the external forces and deformation no longer obey a linear relationship, as in fig. 1, the failure criteria in the elastoplastic constitutive model can no longer be simply determined using the elongation of the final state.
The prior art couples the PD method with the finite element method (Finite element method, FEM) and runs in finite element software Abaqus. The key between two material points is regarded as a rod unit in the coupling model, a large number of rod units are generated between the material points and all points in the near field domain, so that an input file is overlarge, and the operation efficiency is influenced; the Poisson's ratio of the two-dimensional structure and the three-dimensional structure is taken as a fixed value of 1/3 and 1/4 by the key-based near-field dynamics model, so that constitutive relation of materials is limited. The near-field dynamics method avoids the defect that the finite element method solves the discontinuous problems such as crack extension and the like, can simulate the real process of crack extension, but has more application fields of brittle materials such as rock, fiber and the like, has the defect of researching the crack failure of metal materials, especially high-steel-grade long-distance pipelines in the aspects of calculation efficiency and elastoplastic damage failure criteria, and restricts the application of the near-field dynamics method in the analysis of the crack extension of elastoplastic metal materials.
Disclosure of Invention
The present invention has been made in view of the above problems, and it is an object of the present invention to provide a method and apparatus for predicting the ultimate strain capacity of girth welds in high grade steel pipelines that overcomes or at least partially solves the above problems.
In one aspect of the invention, a method of predicting girth weld limit strain capacity of a high grade steel pipeline is provided, the method comprising:
establishing a near field dynamics-finite element coupling model;
applying a load boundary condition;
based on a finite element user dynamic subroutine module in finite element software ABAQUS, a user-defined subroutine is utilized to realize a proposed near field dynamics-finite element coupling model, the near field dynamics-finite element coupling model is calculated, and the limit strain capacity of the girth weld of the high-steel pipeline is predicted.
Further, the establishing a near field dynamics-finite element coupling model includes: according to the node, the unit and the material attribute, a PD elastoplastic constitutive model is established;
failure criteria are configured.
Further, the building of the PD elastoplastic constitutive model includes: the yield surface expression is as follows:
in the method, in the process of the invention,is equivalent stress of point i->Is the yield stress, sigma y0 K is the equidirectional reinforcement modulus, which is the initial yield stress;
the expression is as follows:
where μ is the shear modulus, δ is the near field domain radius,for the elastic elongation of the bond between material points i and j, |ζ| is the distance between material points i and j, V (j) For the volume of material point j, a μ 、a k And->Are near field dynamic parameters, E is elastic modulus, v is Poisson's ratio, N is the number of nodes in the near field domain, h is the thickness of the two-dimensional structure,
θ (i) for volume expansion, the expression is as follows:
in the method, in the process of the invention,sum lambda (i)(j) Are all near-field kinetic parameters of the device,
s (i)(j) for elongation between material points i and j, the expression is as follows:
wherein y is (j) Is the coordinate of the material point j, y (i) As the coordinates of the point i of the material,M<ξ>is the direction of the deformation vector; equivalent plastic stretchingThe expression is as follows:
in the method, in the process of the invention,equivalent plastic tensile strain for the previous analysis step, +.>For equivalent plastic stretching strain increment, A 0 Is a coefficient of->Is the plastic tensile strain increment.
Further, the failure criteria are configured as follows:
the limiting energy release rate required to eliminate two interparticle effects is used as a criterion for judging whether the interparticle effects are invalid, and the expression is as follows:
in the method, in the process of the invention,g is the energy release rate between two particles c To eliminate the limiting energy release rate required by the interaction between two particles, after judging the disappearance of the interaction between two particles, a function psi is introduced (i)(j) Judging whether the action between two particles fails or not, and determining a function psi (i)(j) The value 0 or 1, < > is given>The expression is as follows:
g c the calculation formula is as follows:
wherein Deltax is the size of the PD model unit, h is the thickness of the two-dimensional structure, G c For the ultimate energy release rate of the material, N c Is a near field kinetic parameter, w (i)(j) The area surrounded by the force density and bond elongation relationship curve is the energy density between material points i and j;
material point x i Local injury value of (2)The method comprises the following steps:
wherein H is i Is the near field domain range of material point i.
Further, the applying load boundary condition includes:
defining a non-zero volume domain R at the boundary of the original domain R c The non-zero volume domain width is the same as the near field domain size delta, and an external load is applied to the virtual layer R in the form of a volume force c Is a material point of (a).
Further, the expression of the external load to which the near field dynamics-finite element coupling model is subjected is:
in the method, in the process of the invention,is the normal unit vector of the external load, delta is the virtual boundary layer width, where delta=delta, P (x，t) For application to near field dynamics-finite element coupling in continuous mechanicsExternal load of model boundary, x=r c Is a virtual layer R c Coordinates of the material points.
Further, based on a finite element user dynamic subroutine module in finite element software ABAQUS, the proposed near field dynamics-finite element coupling model is implemented by using a user-defined subroutine, and includes:
dividing the solving domain omega into FEM model subregion omega 1 And PD model subregion Ω 2 And Ω=Ω 1 ∪Ω 2 ，Establishing PD nodes and units in the PD subregions based on the background units;
the units in the near field dynamics-finite element coupling model include: the device comprises a pure FEM unit, a coupling unit and a pure PD unit, wherein the pure FEM unit comprises an FEM node, the coupling unit consists of an FEM node and a PD node and is used for connecting an FEM sub-region and a PD sub-region, and the pure PD unit comprises a PD node;
nodes in the near field dynamics-finite element coupling model are divided into three types of a, b and c;
the expression of the near field dynamics-finite element coupling model motion equation is:
wherein m is k For the quality of node k, u k As the acceleration vector, the acceleration vector is calculated,for external forces acting on node k +.>For local internal force vectors, calculated by ABAQUS,/->For non-local internal forces, the following formula is used:
in the method, in the process of the invention,T[x k ，t]<x j -x k >andT[x j ，t]<x k -x j >is the interaction force between jk bonds;
the a-type node is only acted by local internal force of the FEM unit; the class b node is subjected to local internal force action of the FEM unit and non-local internal force action of the coupling key; the class c node is only acted by the non-local internal force of the key.
Further, the calculating the near field dynamics-finite element coupling model, predicting the limit strain capacity of the girth weld of the high-grade steel pipeline, comprises:
selecting crack tip opening displacement CTOD, far-end strain epsilon of the pipeline and pipeline damage value I after each time step is finished; CTOD is defined as crack propagation driving force, and CTOD-epsilon curve is drawn to obtain material fracture toughness CTOD c Intercepting a crack expansion driving force curve, wherein the obtained intersection point is a crack initiation critical point, establishing a failure criterion based on the crack initiation critical point, wherein the crack initiation critical point is in a crack expansion limit state, the far-end strain corresponding to the crack initiation critical point is a pipeline limit strain, drawing an epsilon-I curve, intercepting the curve according to the pipeline limit strain, the damage value corresponding to the pipeline limit is pipeline limit damage, the pipeline limit damage is a criterion of the crack expansion limit state, and calculating the limit strain capacity of the girth weld of the high-grade steel pipeline.
In a second aspect of the invention, there is provided an apparatus for predicting the ultimate strain capacity of a girth weld of a high grade steel pipeline, the apparatus comprising:
the establishing module is used for establishing a near field dynamics-finite element coupling model;
an application module for applying load boundary conditions;
the prediction module is used for calculating the near field dynamics-finite element coupling model by utilizing a user-defined subroutine to realize the proposed near field dynamics-finite element coupling model based on a finite element user dynamic subroutine module in finite element software ABAQUS and predicting the limit strain capacity of the girth weld of the high-grade steel pipeline.
The method and the device for predicting the girth weld limit strain capacity of the high-grade steel pipeline can realize simulation of a real crack propagation process and accurate prediction of the girth weld limit strain capacity of the pipeline, can provide scientific basis for evaluating the girth weld strain capacity of the high-grade steel pipeline, and can judge material failure by integrating the force density corresponding to the elongation of the whole deformation process.
The foregoing description is only an overview of the present invention, and is intended to be implemented in accordance with the teachings of the present invention in order that the same may be more clearly understood and to make the same and other objects, features and advantages of the present invention more readily apparent.
Drawings
Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to designate like parts throughout the figures. In the drawings:
FIG. 1 schematically illustrates a deformation constitutive relationship diagram in plastic theory;
FIG. 2 is a flow chart of a method for predicting the girth weld limit strain capacity of a high grade steel pipeline according to an embodiment of the present invention;
FIG. 3 is a diagram illustrating a near field dynamics unit according to an embodiment of the present invention;
FIG. 4 shows a virtual layer R with a width delta according to an embodiment of the present invention c Is a structural schematic diagram of (a);
FIG. 5 is a region segmentation diagram provided by an embodiment of the present invention;
FIG. 6 is a graph of crack growth driving force versus strain provided by an embodiment of the present invention;
fig. 7 is a schematic structural diagram of a device for predicting the limit strain capacity of the girth weld of a high-grade pipeline according to an embodiment of the present invention.
Detailed Description
Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
As used herein, the singular forms "a", "an", "the" and "the" are intended to include the plural forms as well, unless expressly stated otherwise, as understood by those skilled in the art. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
It will be understood by those skilled in the art that all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs unless defined otherwise. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
FIG. 2 schematically illustrates a flow chart of a method of predicting the girth weld limit strain capacity of a high grade steel pipeline in accordance with one embodiment of the invention. Referring to fig. 2, the method for predicting the limit strain capacity of the girth weld of the high-grade steel pipeline according to the embodiment of the invention specifically comprises the following steps:
s21, establishing a near field dynamics-finite element coupling model;
s22, applying load boundary conditions;
s23, based on a finite element user dynamic subroutine module in finite element software ABAQUS, a near field dynamics-finite element coupling model is achieved by utilizing a user-defined subroutine, calculation is conducted on the near field dynamics-finite element coupling model, and limit strain capacity of the girth weld of the high-grade steel pipeline is predicted.
Further, the establishing a near field dynamics-finite element coupling model includes: according to the node, the unit and the material attribute, a PD elastoplastic constitutive model is established;
failure criteria are configured.
In this embodiment, a near field dynamics state function is defined;
initial position of keyXThe expression is as follows:
X<ξ>＝ξ，ξ＝x j -x i
relative displacement of two material pointsUThe expression is as follows:
U<ξ>＝u(x j ，t)-u(x i ，t)
deformation vectorYThe expression is as follows:
Y<ξ>＝X<ξ>+U<ξ>
direction of deformation vectorMThe expression is as follows:
e. the elongation e is expressed as follows:
e<ξ>＝y<ξ>-x<ξ>，y<ξ>＝|Y<ξ>|，x(ξ>＝|X<ξ>|
f. the weighted volume m is expressed as follows:
m＝[ω(|ξ|)·x<ξ>]·x<ξ>
wherein ω (|ζ|) is an influence function, ω is preferable 1 (|ζ|) =1 or
The non-local expansion amount θ is expressed as follows:
offset of delaye d <ξ>The expression is as follows:
wherein γ is a constant, and the expression is as follows:
k is bulk modulus and is expressed as follows:
μ is the shear modulus, expressed as follows:
where E is the modulus of elasticity and v is the Poisson's ratio.
In this embodiment, near field dynamics nodes and units are defined;
a two-dimensional tetrahedral unit discretizes an analysis domain omega to obtain a background unit; the center point of each background unit is near field dynamic material point x i The element corresponding to the near field kinetic material point is the integral domain Ω of the material point i Where i=1, 2, …, N, Ω=Ω 1 ∪Ω 2 ∪…∪Ω N As shown in fig. 3, Ω i Is of volume V i N is the total number of background cells.
For each material point x i Near field dynamics unit E of (2) in From the material point itself and with itA contiguous range of material points, where i represents the first node of the near field kinetic unit and n represents the near field kinetic unit number.
Further, the building of the PD elastoplastic constitutive model includes: the yield surface expression is as follows:
in the method, in the process of the invention,is equivalent stress of point i->Is the yield stress, sigma y0 K is the equidirectional reinforcement modulus, which is the initial yield stress;
the expression is as follows:
where μ is the shear modulus, δ is the near field domain radius,is made of materialElastic elongation of bond between points i and j, |ζ| is distance between material points i and j, V (j) For the volume of material point j, a μ 、a k And->Are near field dynamic parameters, E is elastic modulus, v is Poisson's ratio, N is the number of nodes in the near field domain, h is the thickness of the two-dimensional structure,
θ (i) for volume expansion, the expression is as follows:
in the method, in the process of the invention,sum lambda (i)(j) Are all near-field kinetic parameters of the device,
s (i)(j) for elongation between material points i and j, the expression is as follows:
wherein y is (j) Is the coordinate of the material point j, y (i) As the coordinates of the point i of the material,M<ξ>is the direction of the deformation vector;
equivalent plastic stretchingThe expression is as follows:
in the method, in the process of the invention,equivalent plastic tensile strain for the previous analysis step, +.>For equivalent plastic stretching strain increment, A 0 Is a coefficient of->Is the plastic tensile strain increment.
Further, the failure criteria are configured as follows:
the limiting energy release rate required to eliminate two interparticle effects is used as a criterion for judging whether the interparticle effects are invalid, and the expression is as follows:
in the method, in the process of the invention,g is the energy release rate between two particles c To eliminate the limiting energy release rate required by the interaction between two particles, after judging the disappearance of the interaction between two particles, a function psi is introduced (i)(j) Judging whether the action between two particles fails or not, and determining a function psi (i)(j) The value 0 or 1, < > is given>The expression is as follows:
g c the calculation formula is as follows:
wherein Deltax is the size of the PD model unit, h is the thickness of the two-dimensional structure, G c For the ultimate energy release rate of the material, N c Is a near field kinetic parameter, w (i)(j) The area surrounded by the force density and bond elongation relationship curve is the energy density between material points i and j;
material point x i Local injury value of (2)The method comprises the following steps:
wherein H is i Is the near field domain range of material point i.
Further, the applying load boundary condition includes:
defining a non-zero volume domain R at the boundary of the original domain R c The non-zero volume domain width is the same as the near field domain size delta, and an external load is applied to the virtual layer R in the form of a volume force c Is a material point of (a).
In this embodiment, as shown in fig. 4, the non-zero volume domain width is the same as the near field domain size δ.
Further, the expression of the external load to which the near field dynamics-finite element coupling model is subjected is:
in the method, in the process of the invention,is the normal unit vector of the external load, delta is the virtual boundary layer width, where delta=delta, P (x，t) For external loads applied to near field dynamics-finite element coupling model boundaries in continuous mechanics, x=r c Is a virtual layer R c Coordinates of the material points.
Further, based on a finite element user dynamic subroutine module in finite element software ABAQUS, the proposed near field dynamics-finite element coupling model is implemented by using a user-defined subroutine, and includes:
dividing the solving domain omega into FEM model subregion omega 1 And PD model subregion Ω 2 And Ω=Ω 1 ∪Ω 2 ，Establishing PD nodes and units in the PD subregions based on the background units;
the units in the near field dynamics-finite element coupling model include: the device comprises a pure FEM unit, a coupling unit and a pure PD unit, wherein the pure FEM unit comprises an FEM node, the coupling unit consists of an FEM node and a PD node and is used for connecting an FEM sub-region and a PD sub-region, and the pure PD unit comprises a PD node;
nodes in the near field dynamics-finite element coupling model are divided into three types of a, b and c;
the expression of the near field dynamics-finite element coupling model motion equation is:
wherein m is k For the quality of node k, u k As the acceleration vector, the acceleration vector is calculated,for external forces acting on node k +.>For local internal force vectors, calculated by ABAQUS,/->For non-local internal forces, the following formula is used:
in the method, in the process of the invention,T[x k ，t]<x j -x k >andT[x j ，t](x k -x j >is the interaction force between jk bonds;
the a-type node is only acted by local internal force of the FEM unit; the class b node is subjected to local internal force action of the FEM unit and non-local internal force action of the coupling key; the class c node is only acted by the non-local internal force of the key.
In this embodiment, as shown in FIG. 5, the solution domain Ω is divided into FEM model subregions Ω 1 And PD model subregion Ω 2 The node and element information for the different sub-areas is shown in fig. 5 (b).
The units in the coupling model shown in fig. 5 (b) are divided into three types: the pure FEM unit, the coupling unit and the pure PD unit can be input into the ABAQUS software through input files.
The nodes in the coupling model shown in fig. 5 (c) are classified into three types a, b and c.
Further, the calculating the near field dynamics-finite element coupling model, predicting the limit strain capacity of the girth weld of the high-grade steel pipeline, comprises:
selecting crack tip opening displacement CTOD, far-end strain epsilon of the pipeline and pipeline damage value I after each time step is finished; defining CTOD as splitLine expansion driving force, drawing CTOD-epsilon curve, and using material fracture toughness CTOD c Intercepting a crack expansion driving force curve, wherein the obtained intersection point is a crack initiation critical point, establishing a failure criterion based on the crack initiation critical point, wherein the crack initiation critical point is in a crack expansion limit state, the far-end strain corresponding to the crack initiation critical point is a pipeline limit strain, drawing an epsilon-I curve, intercepting the curve according to the pipeline limit strain, the damage value corresponding to the pipeline limit is pipeline limit damage, the pipeline limit damage is a criterion of the crack expansion limit state, and calculating the limit strain capacity of the girth weld of the high-grade steel pipeline.
In this example, as shown in FIG. 6, a CTOD-. Epsilon.curve was plotted.
In the embodiment, calculating the force in the unit, the mass matrix and the external load;
the dimensions of the internal force vector f and the mass matrix M are respectivelyThe algorithm is shown in Table 1.
TABLE 1 Algorithm for force and mass matrix in near field dynamics unit
/>
The expression of the volume correction coefficient is:
wherein x is i And x j Material points i and j, respectively, at the initial timeCoordinates, |ζ|, is the distance between material points i and j, r j Is half the radius of a circle passing through point j with point i as the center.
The method for predicting the girth weld limit strain capacity of the high-grade steel pipeline provided by the embodiment of the invention can realize simulation of a real crack propagation process and accurate prediction of the girth weld limit strain capacity of the pipeline, can provide scientific basis for the girth weld strain capacity evaluation of the high-grade steel pipeline, and can judge the failure of the material by integrating the force density corresponding to the elongation of the whole deformation process.
For the purposes of simplicity of explanation, the methodologies are shown and described as a series of acts, it is to be understood and appreciated by one of ordinary skill in the art that the methodologies are not limited by the order of acts, as some acts may, in accordance with the methodologies, take place in other order or concurrently. Further, those skilled in the art will appreciate that the embodiments described in the specification are presently preferred embodiments, and that the acts are not necessarily required by the embodiments of the invention.
FIG. 7 schematically illustrates a structural schematic of an apparatus for predicting girth weld limit strain capacity of a high grade steel pipeline in accordance with one embodiment of the present invention. Referring to fig. 7, the device for predicting the limit strain capacity of the girth weld of the high-grade pipeline according to the embodiment of the invention specifically comprises:
a building module 701, configured to build a near field dynamics-finite element coupling model;
an apply module 702 for applying a load boundary condition;
the prediction module 703 is configured to implement the proposed near-field dynamics-finite element coupling model by using a user-defined subroutine based on a finite element user dynamic subroutine module in finite element software ABAQUS, calculate the near-field dynamics-finite element coupling model, and predict the limit strain capacity of the girth weld of the high-grade steel pipeline.
The device for predicting the girth weld limit strain capacity of the high-grade steel pipeline provided by the embodiment of the invention can realize simulation of a real crack propagation process and accurate prediction of the girth weld limit strain capacity of the pipeline, can provide scientific basis for evaluating the girth weld strain capacity of the high-grade steel pipeline, and can integrate the force density corresponding to the elongation of the whole deformation process to judge the failure of the material.
For the device embodiments, since they are substantially similar to the method embodiments, the description is relatively simple, and reference is made to the description of the method embodiments for relevant points.
The apparatus embodiments described above are merely illustrative, wherein the elements illustrated as separate elements may or may not be physically separate, and the elements shown as elements may or may not be physical elements, may be located in one place, or may be distributed over a plurality of network elements. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment. Those of ordinary skill in the art will understand and implement the present invention without undue burden.
From the above description of the embodiments, it will be apparent to those skilled in the art that the embodiments may be implemented by means of software plus necessary general hardware platforms, or of course may be implemented by means of hardware. Based on this understanding, the foregoing technical solution may be embodied essentially or in a part contributing to the prior art in the form of a software product, which may be stored in a computer readable storage medium, such as ROM/RAM, a magnetic disk, an optical disk, etc., including several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute the method described in the respective embodiments or some parts of the embodiments.
Furthermore, those skilled in the art will appreciate that while some embodiments herein include some features but not others included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention and form different embodiments. For example, any of the claimed embodiments can be used in any combination.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (7)
1. A method of predicting the ultimate strain capacity of a girth weld of a high grade steel pipeline, the method comprising:
establishing a near field dynamics-finite element coupling model, comprising: according to the node, the unit and the material attribute, a PD elastoplastic constitutive model is established; configuring failure criteria;
applying a load boundary condition;
based on a finite element user dynamic subroutine module in finite element software ABAQUS, a user-defined subroutine is utilized to realize a proposed near field dynamics-finite element coupling model, the near field dynamics-finite element coupling model is calculated, and the limit strain capacity of the girth weld of the high-steel-grade pipeline is predicted;
the building of the PD elastoplastic constitutive model comprises the following steps: the yield surface expression is as follows:
in the method, in the process of the invention,is equivalent to plastic tensile strain->Is equivalent stress of point i->Is the yield stress, sigma y0 K is the equidirectional reinforcement modulus, which is the initial yield stress;
the expression is as follows:
where μ is the shear modulus, δ is the near field domain radius,for the elastic elongation of the bond between material points i and j, |ζ| is the distance between material points i and j, V (j) For the volume of material point j, a μ 、a k And->Are near field dynamic parameters, E is elastic modulus, v is Poisson's ratio, N is the number of nodes in the near field domain, h is the thickness of the two-dimensional structure,
θ (i) for volume expansion, the expression is as follows:
in the method, in the process of the invention,sum lambda (i)(j) Are all near-field kinetic parameters of the device,
s (i)(j) for elongation between material points i and j, the expression is as follows:
wherein y is (j) Is the coordinate of the material point j, y (i) As the coordinates of the point i of the material,M<ξ>is the direction of the deformation vector;
equivalent plastic stretchingThe expression is as follows:
in the method, in the process of the invention,equivalent plastic tensile strain for the previous analysis step, +.>For equivalent plastic stretching strain increment, A 0 Is a coefficient of->Is the plastic tensile strain increment.
2. The method of claim 1, wherein the failure criteria are configured as follows:
the limiting energy release rate required to eliminate two interparticle effects is used as a criterion for judging whether the interparticle effects are invalid, and the expression is as follows:
in the formula g (i)(j) G is the energy release rate between two particles c To eliminate the limiting energy release rate required by the interaction between two particles, after judging the disappearance of the interaction between two particles, a function psi is introduced (i)(j) Judging whether the action between two particles fails or not, and determining a function psi (i)(j) The value of the value is 0 or 1,the expression is as follows:
g c the calculation formula is as follows:
wherein Deltax is the size of the PD model unit, h is the thickness of the two-dimensional structure, G c For the ultimate energy release rate of the material, N c Is a near field kinetic parameter, w (i)(j) The area surrounded by the force density and bond elongation relationship curve is the energy density between material points i and j;
material point x i Local injury value at time tThe method comprises the following steps:
wherein H is i Is the near field domain range of material point i.
3. The method of claim 1, wherein the applying load boundary conditions comprises:
defining a non-zero volume domain R at the boundary of the original domain R c The non-zero volume domain width is the same as the near field domain size delta, and the external load is applied to the non-zero volume domain, namely the virtual layer R in the form of volume force c Is a material point of (a).
4. A method according to claim 3, characterized in that the expression of the external load to which the near field dynamics-finite element coupling model is subjected is:
in the method, in the process of the invention,is the normal unit vector of the external load, delta is the virtual boundary layer width, where delta=delta, P (x,t) For external loads applied to near field dynamics-finite element coupling model boundaries in continuous mechanics, x=r c Is a virtual layer R c Coordinates of the material points.
5. The method according to claim 1, characterized in that the proposed near field dynamics-finite element coupling model is implemented with a user-defined subroutine based on a finite element user dynamic subroutine module in the finite element software ABAQUS, comprising:
dividing the solving domain omega into FEM model subregion omega 1 And PD model subregion Ω 2 And (2) andestablishing PD nodes and units in the PD subregions based on the background units;
the units in the near field dynamics-finite element coupling model include: the device comprises a pure FEM unit, a coupling unit and a pure PD unit, wherein the pure FEM unit comprises an FEM node, the coupling unit consists of an FEM node and a PD node and is used for connecting an FEM sub-region and a PD sub-region, and the pure PD unit comprises a PD node;
nodes in the near field dynamics-finite element coupling model are divided into three types of a, b and c;
the expression of the near field dynamics-finite element coupling model motion equation is:
wherein m is k For the quality of the node k,for acceleration vector +.>To function asExternal force on node k, +.>For local internal force vectors, calculated by ABAQUS,/->For non-local internal forces, the following formula is used:
in the method, in the process of the invention,T[x k ,t]<x j -x k >andT[x j ,t]<x k -x j >is the interaction force between jk bonds;
the a-type node is only acted by local internal force of the FEM unit; the class b node is subjected to local internal force action of the FEM unit and non-local internal force action of the coupling key; the class c node is only acted by the non-local internal force of the key.
6. The method of claim 1, wherein said computing the near field dynamics-finite element coupling model predicts high steel grade pipe girth weld limit strain capacity comprising:
selecting crack tip opening displacement CTOD, far-end strain epsilon of the pipeline and pipeline damage value I after each time step is finished; CTOD is defined as crack propagation driving force, and CTOD-epsilon curve is drawn to obtain material fracture toughness CTOD c Intercepting a crack propagation driving force curve, wherein the obtained intersection point is a crack initiation critical point, establishing a failure criterion based on the crack initiation critical point, wherein the crack initiation critical point is in a crack propagation limit state, the far-end strain corresponding to the crack initiation critical point is a pipeline limit strain, drawing an epsilon-I curve, intercepting the curve according to the pipeline limit strain, wherein the damage value corresponding to the pipeline limit is pipeline limit damage, the pipeline limit damage is a criterion of the crack propagation limit state, and calculating the high-grade steel pipeline ring weldingSeam ultimate strain capacity.
7. An apparatus for predicting the ultimate strain capacity of a girth weld in a high grade steel pipeline, the apparatus comprising:
the establishing module is used for establishing a near field dynamics-finite element coupling model and comprises the following steps: according to the node, the unit and the material attribute, a PD elastoplastic constitutive model is established; configuring failure criteria;
an application module for applying load boundary conditions;
the prediction module is used for calculating the near field dynamics-finite element coupling model by utilizing a user-defined subroutine to realize the proposed near field dynamics-finite element coupling model based on a finite element user dynamic subroutine module in finite element software ABAQUS, and predicting the limit strain capacity of the girth weld of the high-steel-grade pipeline;
the building of the PD elastoplastic constitutive model comprises the following steps: the yield surface expression is as follows:
in the method, in the process of the invention,is equivalent to plastic tensile strain->Is equivalent stress of point i->Is the yield stress, sigma y0 K is the equidirectional reinforcement modulus, which is the initial yield stress;
the expression is as follows:
where μ is the shear modulus, δ is the near field domain radius,for the elastic elongation of the bond between material points i and j, |ζ| is the distance between material points i and j, V (j) For the volume of material point j, a μ 、a k And->Are near field dynamic parameters, E is elastic modulus, v is Poisson's ratio, N is the number of nodes in the near field domain, h is the thickness of the two-dimensional structure,
θ (i) for volume expansion, the expression is as follows:
in the method, in the process of the invention,sum lambda (i)(j) Are all near-field kinetic parameters of the device,
s (i)(j) for elongation between material points i and j, the expression is as follows:
wherein y is (j) Is the coordinate of the material point j, y (i) As the coordinates of the point i of the material,M<ξ>is the direction of the deformation vector;
equivalent plastic stretchingThe expression is as follows:
in the method, in the process of the invention,equivalent plastic tensile strain for the previous analysis step, +.>For equivalent plastic stretching strain increment, A 0 Is a coefficient of->Is the plastic tensile strain increment.
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| CN110457790A (en) * | 2019-07-26 | 2019-11-15 | 顾鑫 | The discontinuous golden finite element method of gal the Liao Dynasty of near field dynamics for malformation analysis |
| CN111814310A (en) * | 2020-06-11 | 2020-10-23 | 大连理工大学 | Method for predicting structural damage by using intensity criterion-driven near-field dynamics model |
| CN112182927A (en) * | 2020-09-15 | 2021-01-05 | 西北工业大学 | Method for simulating mutual influence of cracks of high-temperature alloy linear friction welding joint |
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| CN110457790A (en) * | 2019-07-26 | 2019-11-15 | 顾鑫 | The discontinuous golden finite element method of gal the Liao Dynasty of near field dynamics for malformation analysis |
| CN111814310A (en) * | 2020-06-11 | 2020-10-23 | 大连理工大学 | Method for predicting structural damage by using intensity criterion-driven near-field dynamics model |
| CN112182927A (en) * | 2020-09-15 | 2021-01-05 | 西北工业大学 | Method for simulating mutual influence of cracks of high-temperature alloy linear friction welding joint |
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