Vertical buckling analysis of buried pipelines under different initial defects Liang Guangqiang Zhang Wei 2, Qi Jinlong, Li Yongyu 1 (1. Offshore Oil Engineering Co., Ltd. Tianjin 300451; 2. School of Construction Engineering, Tianjin University, Tianjin 300072) The development is playing an increasingly important role. With the continuous improvement of the requirements for submarine pipeline work, the buckling failure problems of high temperature and high pressure pipelines are also increasing, which has attracted the attention and research of scholars at home and abroad. In this paper, the large-scale general finite element analysis software ABAQUS is used, and the contact model is used to consider the pipe-soil interaction, and a three-dimensional finite element elastoplastic numerical model of the pipeline is established. Numerical simulations were carried out on high-temperature buried pipelines with different initial defects, and the buckling law of pipelines under the influence of different defects was obtained. The results calculated by the finite element model deviate from Pedersenensen's analytical theory, but the basic laws obtained are different from those of Taylor and Tran. Take the z-graph of pipeline buckling finite element calculation when the defect is 25cm as an example, if not. Table 1 Model size basis under different initial defects (a) Soil stress-strain cloud image (b) Pipe stress-strain cloud image = 2511 Pipeline buckling finite element calculation cloud result analysis is easy to find out. With the increase of initial defects, the pipeline The critical buckling temperature decreases, and the critical buckling stress decreases accordingly. The smaller the amplitude of the defect, the more energy released after buckling, and the more obvious the phenomenon of reduced stress. The pipeline stress curve has an obvious descending and rising section. When the defect is large, the pipeline does not have obvious performance from pre-buckling to post-buckling (the inflection point is not obvious), and the buckling stress is small, that is, the critical temperature of buckling and the critical axial force of buckling will be It decreases with the increase of defects. Temperature / C buckling amplitude / cm Relationship between pipe temperature and buckling stress The relationship between piping buckling amplitude and stress shows that the greater the defect, the lower the temperature when buckling occurs; the amplitude of the buckling increases with the defect after the pipeline enters Large and increasing, indicating that the ability of the pipeline to resist buckling decreases, and the instability occurs at a lower stress. At this time, the soil stress does not reach the buckling stress; the displacement will continue to increase as the pipeline buckles, and the soil body increases the resistance of the pipeline. For buckling performance, the displacement of the soil when it reaches yield increases. A theory shows that the displacement of the soil when it reaches the shear yield â–³ + 8 /// D) D is compared with the results obtained by the Pedersenensen analytical formula, as shown in Table 3. Table 3 Comparison of buckling analysis results Initial defect 5 / cm wavelength finite element analysis results Buckling temperature Factory c Buckling stress / MPa Buckling temperature / X: Buckling stress / Mpa As can be seen from Table 3, the analysis results of the finite element model are less than Pedersen ensen Parse the results. The reason is that, in the finite element analysis, only the influence of the shear yield of the soil is considered, and the effect of the weight of the soil is not carefully considered. At the same time, Pedersen ensen analysis results that the buckling stress reaches 1014MPa when the small defect is 10,000 = 1.5cm. Because the pipeline material is API5LX65 steel, its yield stress is 448MPa. At this time, according to the theoretical analysis, the pipeline has already been destroyed, and the critical buckling temperature it is wrong. The simplification of the finite element model is based on adaptive eigenvalue analysis and Riks algorithm. Although there are some deviations, the overall calculation results are ideal and can be used in engineering practice. At the same time, the results obtained from the finite element can intuitively see the change process of the buckling amplitude, temperature and stress during the process of front and back buckling of the pipeline. 3. Conclusion The eigenvalue analysis in ABAQUS can accurately obtain the buckling mode of the pipeline, which can be further introduced into the buckling analysis as a defect. From the modal analysis, it is concluded that the pipeline buried under the seabed is most likely to have vertical buckling, which is consistent with the theory. For the vertical buckling problem, the Riks algorithm is used to introduce the main mode of the pipeline as the initial defect into the numerical model, and the buckling analysis of the whole process of the pipeline is carried out. The previous research on pipeline buckling is limited to the pre-buckling stage of the pipeline, and only reflects the overall instability. This finite element simulation also obtained the relevant results of the occurrence of post-buckling of the pipeline. It is concluded that the pipeline will undergo overall destabilization (buckling) in the case of defects. As the load (temperature or internal pressure) increases, local buckling will occur locally; sometimes the pipeline will first undergo local instability and then overall Sexual instability. The finite element numerical simulation can obtain the process of pipeline buckling, including the local buckling of the pipeline, and the analytical method can only obtain the critical buckling axial force when the pipeline is buckled overall.
They are modern styles that match well with any house . Super cute and bohemian style , they change ordinary into an elegant look and bring you joy for sure . Cotton plant hanger instructions , such a homie touch to your house ! Hanging plant holders are versatile , such as space saver and home decor .
Air Plant Holder,Macrame Plant Hanger,Macrame Plant Holder,Cotton Plant Holder Shandong Guyi Crafts Co.,Ltd , https://www.sddoorcurtains.com