Analytical Methodology for Evaluating Stress and Strain of Pipeline Exposed in Flood

Author(s):  
Xiaolin Wang ◽  
Jian Shuai ◽  
Xiaomin Guo

River-crossing pipeline is threatened by flood which could induce pipeline being eroded and exposed, moreover, floating in a large scale. Under the combined effects of dynamic wave, buoyancy, gravity and resistance of bank soil, pipeline presents spatial deformation. A mechanical analysis model is built according to loadings on pipeline and deformation of pipeline. Taking into account nonlinear soil-pipe interaction, axial force, nonlinear material property of pipeline steel and spacial deformation of pipeline, an analytical methodology for evaluating pipeline deformation and stress distribution is developed. Compatibility equation of pipeline physical elongation and geometrical elongation is derived, by which pipeline stress and strain are calculated with iterative method. Based on proposed methodology, a computer program is developed and a series of cases of pipeline in flood are analyzed with it. Compared with finite element analysis, results of proposed methodology are well accepted. Finally, safety assessment method for pipeline in flood is proposed based on limit state theory and the safety of pipeline exposed in mountain torrent are evaluated.

Author(s):  
Muntaseer Kainat ◽  
Doug Langer ◽  
Sherif Hassanien

Pipeline operators’ utmost priority is to achieve high safety measures during the lifecycle of pipelines including effective management of integrity threats during excavation and repair processes. A single incident pertaining to a mechanical damage in a gas pipeline has been reported previously which resulted in one fatality and one injury during investigation. Some operators have reported leaking cracks while investigating rock induced dents. Excavation under full operating pressure can lead to changes in boundary conditions and unexpected loads, resulting in failure, injuries, or fatalities. In the meantime, lowering operating pressure during excavation can have a significant impact on production and operational availability. The situation poses two conflicting objectives; namely, maximizing safety and maximizing operational availability. Current pipeline regulations require that operators have to ensure safe working conditions by depressurizing the line to a level that will not cause a failure during the repair process. However, there are no detailed guidelines on how an operator should determine a safe excavation pressure (SEP) level, which could lead to engineering judgment and subjectivity in determining such safety level. While the pipeline industry relies on well-defined fitness for purpose analyses for threats such as crack and corrosion, there is a gap in defining a fitness for purpose for dents and dents associated with stress riser features in order to set an SEP. Stress and strain based assessment of dents can be used in this matter; however, it requires advanced techniques to account for geometric and material nonlinearity. Additionally, loading and unloading scenarios during excavation (e.g. removal of indenter, overburden pressure, etc.) drive a change in the boundary conditions of the pipe that could lead to leakage. Nevertheless, crack initiation or presence within a dent should be considered, which requires the incorporation of crack geometry and application of fracture mechanics in assessing a safe excavation pressure. Recently, there have been advancements in stress and strain based finite element analysis (FEA) of dents coupled with structural reliability analysis that can be utilized to assess SEP. This paper presents a reliability-based approach to determine a safe excavation pressure for dented liquid pipelines. The approach employs nonlinear FEA to model dents interacting with crack features coupled with uncertainties associated with pipe properties and in-line-inspection information. A fracture mechanics-based limit state is formulated to estimate the probability of failure of dents associated with cracks at different levels of operating pressure during excavation. The application of the developed approach is demonstrated through examples within limited scope. Recommended enhancements and future developments of the proposed approach are also discussed.


2011 ◽  
Vol 121-126 ◽  
pp. 4523-4527
Author(s):  
Yu Yan Liu ◽  
Yan Wang ◽  
Lin Chen ◽  
Ge Li ◽  
Jian Guo Wang

The paper established U75V 100-meter rail 3-D transient non-liner finite element analysis model about U75V 100-meter rail by using the large-scale non-liner finite element analysis software ABAQUS. By analyzing the different positions in the section of the temperature variation, the changes of bending degree and the residual stress variation after the bending deformation have changed. Based on the 100-meter straight rail in natural cooling under the cooling process, simulation results showed that in the cooling process, deflection change with time mainly divided into four stages; In consideration of the friction effect, the flat rail cold curve for its deformation among roughly flat, the curve about either ends, the scope for bending is 18 meters, the maximal displacement is 1.88 meters while the flat rail occured end colding.


2011 ◽  
Vol 314-316 ◽  
pp. 1591-1596
Author(s):  
Xiang Jun Yu ◽  
Ming Yao Yao

A new Rollover Protective Structure (ROPS) of the large-scale wheel loader was designed based on a buffer-induced structure. Dynamic Finite Element analysis model of the entire vehicle was created and boundary conditions of typical rollover cases were given. Optimization design of this new ROPS was obtained through a comprehensive analysis of 16 dynamic simulation samples, which were designed by Orthogonal Experimental Method. Comparison analysis of dynamic response results between original ROPS and optimal new ROPS indicates that this new ROPS effectively prolonged the duration time of the first collision and reduced the acting time of peak force. Deformation extent of main structure of this new ROPS is significantly smaller than that of the original ROPS. Buffer-induced structures can increase the kinetic energy absorption capability of ROPS. Therefore, it can reduce the possibility of brittle fracture of ROPS and improve the probability of operator survival.


2013 ◽  
Vol 712-715 ◽  
pp. 1080-1083
Author(s):  
Hu Qi Wang ◽  
Hai Zhao He ◽  
Hai Yan Lu ◽  
Rong Xing Huang

A large-scale forklift's wheel rim appeared cracking phenomenon in the course of use. This article summarized and analyzed force of the forklift's wheel rim according to the typical working conditions of forklift, and calculated the load of various working conditions. It provided the correct boundary conditions for the finite element analysis of the wheel rim [. After the analysis of wheel rim's three typical conditions, found the weak parts of the structure of the rim, and this part was consistent with the feedback part, so it proved correct of the finite element analysis model. Clever was used ribbed-plate and punching groove to strengthen the weak part of wheel rim and the finite element model was used to calculate and check the improved wheel rim again. The results showed that the improved wheel rim stress decreased quite, so the measure was correct.


2010 ◽  
Vol 139-141 ◽  
pp. 2386-2390 ◽  
Author(s):  
Guo Jun Yu ◽  
Cheng Bin Du ◽  
Fa Xue Wan

Based on electromagnetic-thermal coupling field mechanism, a large-scale finite element analysis model for electromagnetic-thermal coupling global damper is established by ANSYS software. Electromagnetic field and temperature field sequential coupling analysis method is used in this study. Relative permeability and resistivity of magnetic material with temperature is also considered in the FE model. The simulation results show that the temperature of self- decoupling magnetic damper rises rapidly under external excitation, the temperature changes the magnetic fluid yoke and the materials’ core parameters, magnetic flux density in damper channel gradually decreases with the time, and the damping force decreases, finally the high temperature decline phenomenon is revealed.


Author(s):  
Xin Li ◽  
Wenjian Liu ◽  
Gaoliang Peng ◽  
Qiang Wang

The severe operating conditions required Logging While Drilling (LWD) devices to withstand the high temperatures and pressures. And the seal capability is one of the most important factors to determine the performance and reliability of LWD device directly. O-shaped seal ring is generally used for mechanical sealing in most LWD devices. To precisely predict the behavior of O-shaped seal ring, in this paper, a Finite Element Analysis (FEA) method is proposed to expose the stress and strain of O-shaped seal ring worked under rigorous conditions. An analysis model, which considers all parts are non-rigid components, is established and the contact balance equation is presented. By using ANSYS, the stress distribution and the deformation of O-shaped seal ring is analyzed and a test case is given.


Author(s):  
Ben Edmans ◽  
Dinh Chi Pham ◽  
Zhiqian Zhang ◽  
Tianfu Guo ◽  
Sridhar Narayanaswamy ◽  
...  

Unbonded flexible risers are a key technology in existing and proposed offshore developments. With increasing water depth, the demands on risers increase and the design against hydrostatic and tension loads becomes more of a challenge. In addition, many existing subsea production systems are approaching the end of their design life and operators need to know if they can remain in-service. To enable the benefits from deepwater production and life extension projects to be realized while minimizing risks to life, property and the environment, accurate modelling and analysis tools are required to improve the prediction of failure modes and to develop a better understanding of the conditions leading to progressive failure. In this work, a multi-scale approach is adopted whereby a global dynamic analysis model is employed to determine the overall displacements of the riser and this is linked with a local model that can provide accurate forces and stresses for the prediction of collapse, fatigue damage and buckling of tensile armour wires. Firstly, we describe a nonlinear constitutive model for use in large-scale dynamic analysis of flexible risers based on an analytical homogenization of composite cylinders using the analogy between slip between pipe layers and plastic flow in continua. The model is able to reproduce the bending hysteresis behaviour observed in flexible pipes and its dependence on internal and external pressure. Secondly, we show a procedure for obtaining equivalent material parameters for this model from finite element local analyses of a flexible pipe. Finally, we show the implementation of this constitutive model in a riser system using two-dimensional co-rotational hybrid beam finite elements.


2012 ◽  
Vol 602-604 ◽  
pp. 2245-2248
Author(s):  
Zhong Xian Wang ◽  
Rui Feng Zhang

A detailed elastic-plastic analysis on different semi-elliptical surface crack geometries under uniaxial and biaxial load was conducted using 3D finite element analysis for pipeline steel X100. After quantitating fracture driving force J-integral and plastic yielding load, the effects of biaxial load and crack geometry were investigated by using the Option 3 of R6 failure assessment diagram approach for the surface cracks with the different crack sizes ( aspect ratios c/a = 1, 1.5 and 3 ) and the various biaxial loading ratios λ from -1 to 2. And three option curves of the R6 assessment were compared to evaluate the applicability of R6 assessment method for the X100 steel.


2013 ◽  
Vol 690-693 ◽  
pp. 1966-1971
Author(s):  
Peng Shang ◽  
Kai Cheng Qi ◽  
Ya Xu Wang ◽  
Yu Ming Guan

This paper used the finite element method to compare the mechanical properties of two different configuration counterweight booms of the bucket wheel stacker reclaimer. And two different forms of the finite element analysis model of the counterweight booms were built in ANSYS. The stresses and strains under its working state were calculated. Then the impact of the counterweight arm to the force and stability of the whole rack could be analyzed. The results of this analysis provided a basis to select different types of the counterweight booms in different environment, and it has an important guidance and reference significance to the design and analysis of counterweight booms of large-scale machinery.


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