CN113505449A - Random analysis method for predicting failure load of composite material flexible pipe - Google Patents
Random analysis method for predicting failure load of composite material flexible pipe Download PDFInfo
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Abstract
The invention belongs to the field of ocean engineering design, and discloses a random analysis method for predicting failure load of a composite material flexible pipe, which comprises the following steps: establishing a three-dimensional mechanical analysis model of the deep sea composite material flexible pipe, acquiring a random range of production parameters, simultaneously generating random samples of the production parameters, combining the random sample number with an ABAQUS software calculation model, and randomly analyzing the failure load of the composite material flexible pipe according to a Hashin-Yeh failure criterion and a composite material progressive damage failure coefficient. The system comprises: a random sample generation module; a strength parameter and elastic constant evaluation module; a stress analysis module; and the damage failure analysis module for the composite material flexible pipe. The invention provides a random analysis method for damage failure of a flexible pipe made of a deepwater composite material based on a Monte-Carlo method combined with ABAQUS finite element analysis, and can predict damage failure load of the flexible pipe more accurately.
Description
Technical Field
The invention belongs to the field of ocean engineering design, and particularly relates to a random analysis method for predicting failure load of a composite material flexible pipe.
Background
At present: the deep sea composite material flexible pipe is a novel winding composite pipe. Because the flexible pipe is different from a non-bonding flexible pipe, the flexible pipe does not need a complex framework layer, an armor layer and other structures or thermosetting resin, the production and construction cost of the flexible pipe is lower than that of other pipelines, and the flexible pipe has the advantages of excellent strength, corrosion resistance, winding capability, easy installation and the like. Such pipelines were originally developed for onshore applications such as oil and water pipelines. For example, Sovereign pipelines (formally known as HalliflowTM) were a commercial RTPs early developed by Wellstream corporation as an innovative pipeline technology for onshore oilfield flowlines since 1989. Due to the good results of the application of composite flexible pipes on land, more and more experts and scholars accept composite flexible pipes as a replacement pipeline for offshore projects. In recent years, over 500 km of RTPs have been installed in the middle east and southeast asia, and interest in expanding the use of RTPs is still increasing in the oil and gas industry, while along with the development of composite materials, composite flexible pipes are gradually trying to be applied to the exploitation and transportation of deep water oil and gas.
However, at the present stage, the research on the relevant mechanical properties of the deep sea composite material flexible pipe is still to be perfected, and the damage failure prediction is still a difficult problem in accordance with the production design of the material flexible pipe at present. At present, in the research and design process of the composite material flexible pipe, deterministic modeling is carried out on the basis of determining each process parameter, however, due to uncertainty in the production process of the composite material, the design parameters (such as layer thickness, winding angle and fiber content) present randomness. Meanwhile, the mechanical properties of the composite material flexible pipe are obviously influenced by various production process parameters. Therefore, in order to more accurately predict damage failure of a composite pipe, the randomness of the design parameters should be considered.
Through the above analysis, the problems and defects of the prior art are as follows: the existing technology carries out modeling analysis aiming at deterministic process parameters, and the ignored randomness of each parameter in the production process, namely the accuracy of each production parameter value cannot be guaranteed in the production process, fluctuates in a certain range, so that the calculation result cannot accurately represent the real mechanical property of a sample tube due to the fact that the existing technical scheme is ignored.
The difficulty in solving the above problems and defects is: in the production process of the sample tubes, certain randomness exists in production process parameters (such as wall thickness, fiber content, winding angle and the like), namely, the process parameter values of the produced sample tubes are not fixed values, but fluctuate near the fixed values. According to the existing research results, different production process parameter values have obvious influence on the mechanical property of the flexible pipe. In the production process of the flexible pipe, a plurality of process parameters and more parameter values are distributed, and the determination of the numerical fluctuation range of different process parameters is a difficult point; meanwhile, how to comprehensively consider the randomness of each process parameter is the second difficulty.
The significance of solving the problems and the defects is as follows: mechanical analysis of flexible pipe is of great importance for flexible pipe design, as underestimation of certain parameters (such as pipe wall thickness, wrap angle, etc.) can lead to pipe failure with catastrophic consequences in environmental, economic and geopolitical terms. On the other hand, since the length of offshore pipelines is usually long, a slight overestimation of some parameters (e.g. wall thickness, fiber content) will result in a lot of additional production and transportation costs. The existing deterministic analysis method cannot accurately simulate the random distribution of production process parameters in the production process, so that the mechanical property of the flexible pipe can be overestimated or underestimated, and the safety of the flexible pipe in the operation period cannot be ensured. The invention can more accurately evaluate the mechanical property of the flexible pipe, comprehensively considers the randomness of each process parameter, can ensure the production quality of the flexible pipe, and can provide more reliable basis for the selection of the safety coefficient.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a random analysis method for predicting the failure load of a composite material flexible pipe.
The invention is realized in such a way that a random analysis method for predicting the failure load of the composite material flexible pipe comprises the following steps: establishing a three-dimensional mechanical analysis model of the deep sea composite material flexible pipe, acquiring a random range of production parameters, simultaneously generating random samples of the production parameters, combining the random sample number with an ABAQUS software calculation model, and randomly analyzing the failure load of the composite material flexible pipe according to a Hashin-Yeh failure criterion and a composite material progressive damage failure coefficient.
Further, the random analysis method for predicting the failure load of the composite material flexible pipe comprises the following steps:
step one, determining the fluctuation range of production process parameters; generating a random sample in a fluctuation range of production process parameters by adopting a Monte-Carlo method;
the first step has the positive effects: the distribution range of main process parameters is covered, the randomness of the production process is more comprehensively considered, main samples which possibly appear in the production process of the flexible pipe are obtained, and analysis samples are provided for subsequent analysis.
Evaluating the strength parameter and the elastic constant of the reinforced layer composite material under the production process parameters corresponding to different samples;
the second step has the positive effects that: the randomness of the process parameters has a decisive influence on the strength parameters and the elastic constants of the reinforced layer composite material, meanwhile, the reinforced layer is a main bearing structure of the flexible pipe, and the accurate simulation of the strength parameters and the elastic constants of the reinforced layer is a key step for accurately analyzing the mechanical performance of the flexible pipe.
Establishing a finite element analysis model of the composite material flexible pipe by using ABAQUS finite element analysis software, and applying load to calculate stress distribution for stress analysis;
the third step has the positive effects: the accurate simulation of the stress distribution of the flexible pipe under different load effects is the basis for the subsequent accurate prediction of the damage failure of the flexible pipe.
And fourthly, performing damage failure analysis on the composite material flexible pipe by utilizing a Hashin-Yeh failure criterion and a composite material progressive damage failure coefficient and combining a stress analysis calculation result of the ABAQUS finite element model.
The fourth step has the positive effects that: the method can accurately predict the damage failure of the flexible pipe, can accurately determine the ultimate load and the bearing capacity of the flexible pipe, can accurately evaluate the mechanical property of the flexible pipe, and is the final step of the method.
Further, the production process parameters comprise: the thickness of the reinforcing layer, the winding angle and the fiber content.
Further, the random sample number is determined by a coefficient of variation.
Further, under the evaluation of the production process parameters corresponding to the different samples, the calculation formula of the strength parameter and the elastic constant of the reinforced layer composite material is as follows:
E1＝EfVf+EmVm；
E1，E2，E3an anisotropic elastic modulus for the reinforcement layer; g12，G13，G23An anisotropic shear modulus for the reinforcement layer; v is12，ν13，ν21An isotropic poisson's ratio for the enhancement layer; efIs the modulus of elasticity of the glass fiber; gfIs the glass fiber shear modulus; v isfIs the poisson ratio of the glass fiber; fftIs the tensile strength of the glass fiber; vfIs the fiber volume content; emIs the elastic modulus of the matrix material; gmShear modulus of the matrix material; v ismIs the poisson ratio of the glass fiber; fmtIs the tensile strength of the glass fiber; vmIs the volume content of the matrix material; c is a contact coefficient (set to 0.2); xT，XC，YT，YC，ZTAnd ZCIs the enhancement layer strength parameter.
Further, in step three, establishing a finite element analysis model of the composite material flexible pipe by using ABAQUS finite element analysis software, and applying a load to calculate stress distribution for stress analysis comprises:
generating all parts of the 3D deformable entity using two concentric circles of stretching; creating two materials, creating N +2 solid layers aiming at the specific number of the enhancement layer layers, namely N layers, of the flexible pipe, and simultaneously defining the winding angle of the enhancement layer; the liner, reinforcement laminate and coating were simulated using C3D 8R; creating two reference points RP1 and RP2 at the center of the two sections, respectively; the two reference points RP1 and RP2 are kinematically coupled with all nodes on the corresponding section, adding the corresponding design loads; setting the grid as a sweep grid, wherein the sweep direction is a radial direction; the side length of the inner liner layer grid is controlled to be 4mm through the seed distribution manager, the side length of the outer protection layer grid is controlled to be 2mm, the side length of the enhancement layer grid is controlled to be 0.25mm, and the stress distribution of each layer of the flexible pipe is obtained through operation calculation.
Further, the creating of the two materials includes:
an HDPE material for use as an inner liner and an outer protective layer to define its elasticity and plasticity;
the other is HDPE glass fiber band material used for the reinforced layer, and the elasticity of the HDPE glass fiber band material is defined by using anisotropic engineering constants.
Further, in the fourth step, the performing damage failure analysis on the composite material flexible pipe by using the Hashin-Yeh failure criterion and the composite material progressive damage failure coefficient and combining the stress analysis calculation result of the ABAQUS finite element model comprises the following steps:
taking a Hashin-Yeh failure criterion as a failure judgment standard of the composite material flexible pipe to obtain the ultimate loads of the composite material flexible pipe under different failure modes;
and determining a progressive failure coefficient of the composite material reinforcing layer, and determining material parameter degradation in the process of damaging the reinforcing layer by combining the progressive failure coefficient.
Further, the method for analyzing the damage failure of the composite material flexible pipe by utilizing the Hashin-Yeh failure criterion and the composite material progressive damage failure coefficient and combining the stress analysis calculation result of the ABAQUS finite element model comprises the following steps:
defining an initial external load P, iterating in a mode of gradually stacking loads, judging damage of a stress result of each step of iterative calculation by adopting a Hashin-Yeh failure criterion, and utilizing a damage factor Ri(i ═ ft, fc, mt, mc, s, td, and cd) reflects the state of damage; when the failure factor is greater than 1, indicating that damage occurs; meanwhile, calculating the rigidity attenuation of the composite material by using the damage failure coefficient according to the damage judgment result; and (5) taking the iteration result of the previous step as the initial state of the next iteration, outputting a limit failure load after a final damage failure mode is reached, and ending the iteration.
Further, the formula for performing damage failure analysis on the composite material flexible pipe by using the Hashin-Yeh failure criterion and the composite material progressive damage failure coefficient and combining the stress analysis calculation result of the ABAQUS finite element model is as follows:
σ1，σ2，σ3，τ12，τ13and τ23Is the component of normal stress and shear stress in all directions under the material coordinate system. X12，X13And X23The in-plane shear strength is the anisotropy. Ri(i ═ ft, fc, mt, mc, s, td and cd) are destruction factors.
Another object of the present invention is to provide a stochastic analysis system for predicting failure load of a composite flexible pipe, implementing the stochastic analysis method for predicting failure load of a composite flexible pipe, the stochastic analysis system for predicting failure load of a composite flexible pipe comprising:
the random sample generation module is used for determining the fluctuation range of the production process parameters; generating a random sample in a fluctuation range of production process parameters by adopting a Monte-Carlo method;
the strength parameter and elastic constant evaluation module is used for evaluating the strength parameter and the elastic constant of the reinforced layer composite material under the production process parameters corresponding to different samples;
the stress analysis module is used for establishing a composite material flexible pipe finite element analysis model by using ABAQUS finite element analysis software and applying load to calculate stress distribution for stress analysis;
and the composite material flexible pipe damage failure analysis module is used for analyzing the damage failure of the composite material flexible pipe by utilizing a Hashin-Yeh failure criterion and a composite material progressive damage failure coefficient and combining a stress analysis calculation result of the ABAQUS finite element model.
The invention also aims to provide a deep sea composite material flexible pipe load analysis terminal which is used for executing the random analysis method for predicting the failure load of the composite material flexible pipe.
By combining all the technical schemes, the invention has the advantages and positive effects that: the invention provides a random analysis method for damage failure of a deepwater composite material flexible pipe based on a Monte-Carlo method combined with ABAQUS finite element analysis. The traditional flexible pipe evaluation technical scheme only carries out deterministic analysis on a production sample pipe, ignores the randomness of production process parameters, then in the production process of the flexible pipe, the production process parameters fluctuate within a certain range, and the uncertainty of each parameter has obvious influence on the mechanical properties of the flexible pipe, so that the deterministic analysis method cannot really predict the ultimate load of a flexible pipe product. The technical scheme changes the thought of the traditional technical scheme, and considers the randomness of each production process, so that the mechanical characteristics of the flexible pipe product are simulated more truly, samples which possibly appear in the production process are covered, and the damage failure load of the flexible pipe can be predicted more accurately.
Drawings
Fig. 1 is a flowchart of a stochastic analysis method for predicting a failure load of a composite flexible pipe according to an embodiment of the present invention.
FIG. 2 is a schematic diagram of a finite element model of a composite material flexible pipe according to an embodiment of the present invention.
Fig. 3 is a schematic diagram of a random sample distribution provided by an embodiment of the present invention.
Fig. 4 is a schematic diagram of a convergence trend of the coefficient of variation according to the embodiment of the present invention.
Fig. 5 is a diagram illustrating the random analysis result of the burst pressure according to the embodiment of the present invention.
Fig. 6 is a schematic diagram of a composite material flexible pipe structure provided by an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Aiming at the problems in the prior art, the invention provides a random analysis method for predicting the failure load of a composite material flexible pipe, and the invention is described in detail below by combining the attached drawings.
The random analysis method for predicting the failure load of the composite material flexible pipe provided by the embodiment of the invention comprises the following steps:
establishing a three-dimensional mechanical analysis model of the deep sea composite material flexible pipe, acquiring a random range of production parameters, simultaneously generating random samples of the production parameters, combining the random sample number with an ABAQUS software calculation model, and randomly analyzing the failure load of the composite material flexible pipe according to a Hashin-Yeh failure criterion and a composite material progressive damage failure coefficient.
As shown in fig. 1, a random analysis method for predicting a failure load of a composite flexible pipe according to an embodiment of the present invention includes the following steps:
s101, determining the fluctuation range of production process parameters; generating a random sample in a fluctuation range of production process parameters by adopting a Monte-Carlo method;
s102, evaluating the strength parameter and the elastic constant of the reinforced layer composite material under the production process parameters corresponding to different samples;
s103, establishing a finite element analysis model of the composite material flexible pipe by using ABAQUS finite element analysis software, and applying load to calculate stress distribution for stress analysis;
and S104, performing damage failure analysis on the composite material flexible pipe by using a Hashin-Yeh failure criterion and a composite material progressive damage failure coefficient and combining a stress analysis calculation result of the ABAQUS finite element model.
The production process parameters provided by the embodiment of the invention comprise: the thickness of the reinforcing layer, the winding angle and the fiber content.
The random sample number provided by the embodiment of the invention is determined through the coefficient of variation.
In the embodiment of the invention, under the condition of evaluating the production process parameters corresponding to different samples, the strength parameter and the elastic constant of the reinforced layer composite material have the following calculation formula:
E1＝EfVf+EmVm；
E1，E2，E3an anisotropic elastic modulus for the reinforcement layer; g12，G13，G23An anisotropic shear modulus for the reinforcement layer; v is12，ν13，ν21An isotropic poisson's ratio for the enhancement layer; efIs the modulus of elasticity of the glass fiber; gfIs the glass fiber shear modulus; v isfIs the poisson ratio of the glass fiber; fftIs the tensile strength of the glass fiber; vfIs the fiber volume content; emIs the elastic modulus of the matrix material; gmShear modulus of the matrix material; v ismIs the poisson ratio of the glass fiber; fmtIs the tensile strength of the glass fiber; vmIs the volume content of the matrix material; c is contact coefficient (set to0.2)；XT，XC，YT，YC，ZTAnd ZCIs the enhancement layer strength parameter.
The method for establishing the finite element analysis model of the composite material flexible pipe by using ABAQUS finite element analysis software provided by the embodiment of the invention, and the stress analysis by applying load to calculate stress distribution comprises the following steps: generating all parts of the 3D deformable entity using two concentric circles of stretching; creating two materials, creating N +2 solid layers aiming at the specific number of the enhancement layer layers, namely N layers, of the flexible pipe, and simultaneously defining the winding angle of the enhancement layer; the liner, reinforcement laminate and coating were simulated using C3D 8R; creating two reference points RP1 and RP2 at the center of the two sections, respectively; the two reference points RP1 and RP2 are kinematically coupled with all nodes on the corresponding section, adding the corresponding design loads; setting the grid as a sweep grid, wherein the sweep direction is a radial direction; the side length of the inner liner layer grid is controlled to be 4mm through the seed distribution manager, the side length of the outer protection layer grid is controlled to be 2mm, the side length of the enhancement layer grid is controlled to be 0.25mm, and the stress distribution of each layer of the flexible pipe is obtained through operation calculation.
The creation of two materials provided by the embodiment of the invention comprises the following steps:
an HDPE material for use as an inner liner and an outer protective layer to define its elasticity and plasticity;
the other is HDPE glass fiber band material used for the reinforced layer, and the elasticity of the HDPE glass fiber band material is defined by using anisotropic engineering constants.
The method for analyzing the damage failure of the composite material flexible pipe by utilizing the Hashin-Yeh failure criterion and the progressive damage failure coefficient of the composite material and combining the stress analysis calculation result of the ABAQUS finite element model comprises the following steps:
taking a Hashin-Yeh failure criterion as a failure judgment standard of the composite material flexible pipe to obtain the ultimate loads of the composite material flexible pipe under different failure modes;
and determining a progressive failure coefficient of the composite material reinforcing layer, and determining material parameter degradation in the process of damaging the reinforcing layer by combining the progressive failure coefficient.
The method for analyzing the damage failure of the composite material flexible pipe by utilizing the Hashin-Yeh failure criterion and the progressive damage failure coefficient of the composite material and combining the stress analysis calculation result of the ABAQUS finite element model comprises the following steps:
defining an initial external load P, iterating in a mode of gradually stacking loads, judging damage of a stress result of each step of iterative calculation by adopting a Hashin-Yeh failure criterion, and utilizing a damage factor Ri(i ═ ft, fc, mt, mc, s, td, and cd) reflects the state of damage; when the failure factor is greater than 1, indicating that damage occurs; meanwhile, calculating the rigidity attenuation of the composite material by using the damage failure coefficient according to the damage judgment result; and (5) taking the iteration result of the previous step as the initial state of the next iteration, outputting a limit failure load after a final damage failure mode is reached, and ending the iteration.
The formula for performing damage failure analysis on the composite material flexible pipe by utilizing the Hashin-Yeh failure criterion and the composite material progressive damage failure coefficient and combining the stress analysis calculation result of the ABAQUS finite element model provided by the embodiment of the invention is as follows:
the technical solution of the present invention is further described with reference to the following specific embodiments.
Example 1:
analytical procedure
Step 1: determining the fluctuation range of the production process parameters (such as the thickness of the reinforced layer, the winding angle, the fiber content and the like).
Step 2: and generating a random sample in a fluctuation range of production process parameters by adopting a Monte-Carlo method. The random sample number N is determined by the coefficient of variation.
And step 3: and (4) evaluating the strength parameter and the elastic constant of the reinforced layer composite material (realized by MATLAB programming) under the production process parameters corresponding to different samples. The calculation formula is summarized as follows:
E1＝EfVf+EmVm (1)
and 4, step 4: establishing a finite element analysis model of the composite material flexible pipe by using ABAQUS finite element analysis software, and applying load to calculate stress distribution.
And 5: and taking the Hashin-Yeh failure criterion as the failure judgment standard of the composite material flexible pipe to obtain the ultimate load of the composite material flexible pipe under different failure modes.
Step 6: and (3) providing progressive failure coefficients of the reinforced layer of the composite material (see table 1), and determining the material parameter degradation in the damage process of the reinforced layer by combining the progressive failure coefficients.
TABLE 1 progressive Damage failure coefficients for enhancement layers
The invention adopts a Monte-Carlo method to generate enough sample numbers, simulates the randomness of production process parameters, and the sample numbers are determined by defining a coefficient of variation (generally 500). Evaluating each sample correspondenceAnd applying the evaluation result to ABAQUS finite element analysis software to establish an integral analysis model of the composite flexible pipe for stress analysis. Firstly, defining an initial external load P, iterating by adopting a mode of gradually stacking loads, judging damage of a stress result of each step of iterative calculation by adopting a Hashin-Yeh failure criterion, and judging a damage factor Ri(i ═ ft, fc, mt, mc, s, td, and cd) reflects the state of damage. Once the failure factor is greater than 1, damage can occur. And meanwhile, calculating the rigidity attenuation of the composite material by using the damage failure coefficient provided by the table 1 according to the judgment result. And (5) taking the iteration result of the previous step as the initial state of the next iteration, outputting a limit failure load after a final damage failure mode is reached, and ending the iteration.
An analysis module:
module 1: random samples are generated. According to product statistics, the fluctuation ranges of different production process parameters (such as layer thickness, winding angle, fiber content and the like) are obtained by considering uncertainty in the production process. Sufficient samples were generated using the Monte-Carlo method. The number of samples N is determined by the coefficient of variation, which is required to ensure convergence, and is typically 500.
And (3) module 2: the material parameters (strength parameter and elastic constant) of the reinforced layer composite were evaluated. And (3) evaluating the material parameters of the reinforced layer composite material corresponding to different samples by utilizing Matlab programming software, and laying a foundation for subsequent stress analysis.
And a module 3: and (5) stress analysis. And (3) establishing an integral mechanics analysis model of the composite material flexible pipe by using finite element analysis software ABAQUS, and carrying out stress analysis on the load applied by each iteration step.
And (4) module: and analyzing damage failure and outputting failure load. And (3) performing damage failure analysis on the composite material flexible pipe by using a Hashin-Yeh failure criterion and a composite material progressive damage failure coefficient (table 1) and combining a stress analysis calculation result of an ABAQUS finite element model. And outputting the ultimate failure load after the ultimate damage failure mode is reached.
Example 2:
the prediction of the limit bearing internal pressure of the deepwater composite material flexible pipe is taken as an example. The method adopts a sample pipe provided by the Wighainewa Limited company to carry out an internal pressure blasting experiment, and adopts deterministic modeling and random modeling to predict the blasting pressure of the flexible pipe and compare the result with the experiment result.
Firstly, a finite element analysis model of the composite material flexible pipe is established by using ABAQUS finite element analysis software, as shown in figure 2.
The experimental pipeline parameters provided by the pipeline manufacturers are shown in tables 2 and 3:
TABLE 2 Flexible pipe construction parameters
TABLE 3 Flexible pipe Material parameters
The design thickness of the flexible tube reinforcement layer is 0.25mm, the winding angle is 55 °/-55 ° (± 55 °), and the fiber volume content is 40%. According to statistics in the production process of manufacturers, the thickness fluctuation range of the enhancement layer is 0.22-0.28, the winding angle fluctuation range is 52.5-57.5 degrees, and the fiber content fluctuation range is 35-45 percent. Firstly, random modeling analysis was performed to produce random samples for three production parameters (layer thickness, winding angle, fiber content) by the Monte-Carlo method, the number of samples being determined by the coefficient of variation to be 500 (determined according to the convergence criterion that the coefficient of variation is lower than 0.1), see fig. 3 and 4.
And calculating the elastic constant and the strength parameter of the enhancement layer according to the random samples, wherein the calculation formula is as follows:
E1＝EfVf+EmVm (1)
the random parameter samples were combined with the finite element model for random analysis, and the calculation results obtained are shown in fig. 5.
Meanwhile, routine deterministic analysis is performed, and the experimental result, the stochastic model analysis result and the deterministic analysis result are compared, for example, in table 4.
TABLE 4 comparison of results
According to the calculation results in the table 3, compared with a deterministic modeling method, the average value of the prediction result of the stochastic modeling analysis method is closer to the test value, and meanwhile, the fluctuation range of the burst pressure under the influence of parameter randomness can be obtained through the stochastic analysis method, so that support is provided for determining the safety factors of different design loads.
It should be noted that the embodiments of the present invention can be realized by hardware, software, or a combination of software and hardware. The hardware portion may be implemented using dedicated logic; the software portions may be stored in a memory and executed by a suitable instruction execution system, such as a microprocessor or specially designed hardware. Those skilled in the art will appreciate that the apparatus and methods described above may be implemented using computer executable instructions and/or embodied in processor control code, such code being provided on a carrier medium such as a disk, CD-or DVD-ROM, programmable memory such as read only memory (firmware), or a data carrier such as an optical or electronic signal carrier, for example. The apparatus and its modules of the present invention may be implemented by hardware circuits such as very large scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, or programmable hardware devices such as field programmable gate arrays, programmable logic devices, etc., or by software executed by various types of processors, or by a combination of hardware circuits and software, e.g., firmware.
The above description is only for the purpose of illustrating the present invention and the appended claims are not to be construed as limiting the scope of the invention, which is intended to cover all modifications, equivalents and improvements that are within the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. A random analysis method for predicting failure load of a composite material flexible pipe is characterized by comprising the following steps: establishing a three-dimensional mechanical analysis model of the deep sea composite material flexible pipe, acquiring a random range of production parameters, simultaneously generating random samples of the production parameters, combining the random sample number with an ABAQUS software calculation model, and randomly analyzing the failure load of the composite material flexible pipe according to a Hashin-Yeh failure criterion and a composite material progressive damage failure coefficient.
2. A stochastic analysis method for predicting failure load of a composite flexible pipe according to claim 1, wherein the stochastic analysis method for predicting failure load of a composite flexible pipe comprises the steps of:
step one, determining the fluctuation range of production process parameters; generating a random sample in a fluctuation range of production process parameters by adopting a Monte-Carlo method;
evaluating the strength parameter and the elastic constant of the reinforced layer composite material under the production process parameters corresponding to different samples;
establishing a finite element analysis model of the composite material flexible pipe by using ABAQUS finite element analysis software, and applying load to calculate stress distribution for stress analysis;
and fourthly, performing damage failure analysis on the composite material flexible pipe by utilizing a Hashin-Yeh failure criterion and a composite material progressive damage failure coefficient and combining a stress analysis calculation result of the ABAQUS finite element model.
3. A stochastic analysis method for prediction of failure load of composite flexible pipe according to claim 1, wherein the production process parameters comprise: the thickness of the reinforcing layer, the winding angle and the fiber content.
4. A stochastic analysis method for predicting failure load of a composite flexible pipe according to claim 2, wherein the random sample number is determined by a coefficient of variation.
5. The stochastic analysis method for predicting the failure load of the composite flexible pipe according to claim 2, wherein under the condition of evaluating the production process parameters corresponding to different samples, the calculation formula of the strength parameter and the elastic constant of the reinforced layer composite material is as follows:
E1＝EfVf+EmVm；
6. a stochastic analysis method for predicting failure load of a composite flexible pipe as claimed in claim 2, wherein in step three, the establishing of the finite element analysis model of the composite flexible pipe by using ABAQUS finite element analysis software, the applying of load to calculate stress distribution for stress analysis comprises: generating all parts of the 3D deformable entity using two concentric circles of stretching; creating two materials, creating N +2 solid layers aiming at the specific number of the enhancement layer layers, namely N layers, of the flexible pipe, and simultaneously defining the winding angle of the enhancement layer; the liner, reinforcement laminate and coating were simulated using C3D 8R; creating two reference points RP1 and RP2 at the center of the two sections, respectively; the two reference points RP1 and RP2 are kinematically coupled with all nodes on the corresponding section, adding the corresponding design loads; setting the grid as a sweep grid, wherein the sweep direction is a radial direction; the side length of the inner liner layer grid is controlled to be 4mm through the seed distribution manager, the side length of the outer protection layer grid is controlled to be 2mm, the side length of the enhancement layer grid is controlled to be 0.25mm, and the stress distribution of each layer of the flexible pipe is obtained through operation calculation.
7. A stochastic analysis method for predicting failure load of a composite flexible pipe according to claim 6, wherein the creating two materials comprises:
HDPE material used for the inner liner layer and the outer protective layer is used for defining the elasticity and plasticity of the HDPE material;
the reinforced layer is made of HDPE glass fiber band material, and the elasticity of the reinforced layer is defined by using anisotropic engineering constants.
8. The stochastic analysis method for predicting failure load of the composite flexible pipe as claimed in claim 2, wherein in the fourth step, the performing of the damage failure analysis of the composite flexible pipe by using the Hashin-Yeh failure criterion and the composite progressive damage failure coefficient in combination with the stress analysis calculation result of the ABAQUS finite element model comprises:
taking a Hashin-Yeh failure criterion as a failure judgment standard of the composite material flexible pipe to obtain the ultimate loads of the composite material flexible pipe under different failure modes;
determining a progressive failure coefficient of the composite material reinforcing layer, and determining material parameter degradation in the process of damaging the reinforcing layer by combining the progressive failure coefficient;
the method for analyzing the damage failure of the composite material flexible pipe by utilizing the Hashin-Yeh failure criterion and the progressive damage failure coefficient of the composite material and combining the stress analysis calculation result of the ABAQUS finite element model comprises the following steps:
defining an initial external load P, iterating in a mode of gradually stacking loads, judging damage of a stress result of each step of iterative calculation by adopting a Hashin-Yeh failure criterion, and utilizing a damage factor Ri(i ═ ft, fc, mt, mc, s, td, and cd) reflects the state of damage; when the failure factor is greater than 1, indicating that damage occurs; meanwhile, calculating the rigidity attenuation of the composite material by using the damage failure coefficient according to the damage judgment result; the iteration result of the previous step is used as the initial state of the next step of iteration, after the final damage failure mode is reached, the ultimate failure load is output, and the iteration is finished;
the formula for carrying out damage failure analysis on the composite material flexible pipe by utilizing the Hashin-Yeh failure criterion and the composite material progressive damage failure coefficient and combining the stress analysis calculation result of the ABAQUS finite element model is as follows:
E1，E2，E3an anisotropic elastic modulus for the reinforcement layer; g12，G13，G23An anisotropic shear modulus for the reinforcement layer; v is12，ν13，ν21An isotropic poisson's ratio for the enhancement layer; efIs the modulus of elasticity of the glass fiber; gfIs the glass fiber shear modulus; v isfIs the poisson ratio of the glass fiber; fftIs the tensile strength of the glass fiber; vfIs the fiber volume content; emIs the elastic modulus of the matrix material; gmShear modulus of the matrix material; v ismIs the poisson ratio of the glass fiber; fmtIs the tensile strength of the glass fiber; vmIs the volume content of the matrix material; c is a contact coefficient set to 0.2; xT，XC，YT，YC，ZTAnd ZCIs the enhancement layer strength parameter.
9. A stochastic analysis system for predicting failure load of a composite flexible pipe, implementing the stochastic analysis method for predicting failure load of a composite flexible pipe according to any one of claims 1 to 8, wherein the stochastic analysis system for predicting failure load of a composite flexible pipe comprises:
the random sample generation module is used for determining the fluctuation range of the production process parameters; generating a random sample in a fluctuation range of production process parameters by adopting a Monte-Carlo method;
the strength parameter and elastic constant evaluation module is used for evaluating the strength parameter and the elastic constant of the reinforced layer composite material under the production process parameters corresponding to different samples;
the stress analysis module is used for establishing a composite material flexible pipe finite element analysis model by using ABAQUS finite element analysis software and applying load to calculate stress distribution for stress analysis;
and the composite material flexible pipe damage failure analysis module is used for analyzing the damage failure of the composite material flexible pipe by utilizing a Hashin-Yeh failure criterion and a composite material progressive damage failure coefficient and combining a stress analysis calculation result of the ABAQUS finite element model.
10. The deep sea composite material flexible pipe load analysis terminal is characterized by being used for executing the random analysis method for predicting the failure load of the composite material flexible pipe according to any one of claims 1 to 8.
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