Mechanical Behavior of Buried Pipeline Crossing Thaw Settlement Zone

2021 ◽  
Author(s):  
Rui Xie ◽  
Prof. Jie Zhang
Keyword(s):  
Mechanical Behavior ◽  
Axial Strain ◽  
Compressive Strain ◽  
High Stress ◽  
Axial Direction ◽  
Soil Parameters ◽  
Buried Pipeline ◽  
Obvious Effect ◽  
Thaw Settlement ◽  
Pipeline Crossing

Abstract Thaw settlement is one of main reason caused pipeline failure crossing cold region. Mechanical behavior of buried pipeline crossing thaw settlement zone is investigated. Effects of pipeline and soil parameters on the buried pipeline were discussed. The results show that the high stress area and the max axial strain of the pipeline is at the edge of the thaw settlement zone. The upper surface of the pipeline is tensile strain, while the lower surface is compressive strain. The max ovality of pipeline near the edge of thaw settlement zone tends to oval. The pipeline axial strain, ovality and displacement decreases with the increasing of pipeline wall thickness, while the change of high stress area is not obvious. The high stress area and ovality decrease with the increasing of pipeline diameter, while the high stress area is expanded along the axial direction, but axial strain decreases slightly. The high stress area, axial strain, ovality and displacement of pipeline decrease with the buried depth increases. With the internal pressure increases, the stress and axial strain of pipeline increase, but the ovality decreases. The soil`s elasticity modulus has no obvious effect on pipeline`s stress, axial strain and displacement, but it can affect ovality slightly.

Mechanical Behavior Analysis of the Buried Steel Pipeline Crossing Landslide Area

2016 ◽  
Vol 138 (5) ◽  
Author(s):  
Jie Zhang ◽  
Zheng Liang ◽  
Chuanjun Han
Keyword(s):  
Mechanical Behavior ◽  
Tensile Strain ◽  
Structural Integrity ◽  
High Stress ◽  
Soil Parameters ◽  
Buried Pipeline ◽  
Landslide Area ◽  
Steel Pipeline ◽  
Bending Deformation ◽  
Pipeline Crossing

Landslide movement is one of the threats for the structural integrity of buried pipelines that are the main ways to transport oil and gas. In order to offer a theoretical basis for the design, safety evaluation, and maintenance of pipelines, mechanical behavior of the buried steel pipeline crossing landslide area was investigated by finite-element method, considering pipeline-soil interaction. Effects of landslide soil parameters, pipeline parameters, and landslide scale on the mechanical behavior of the buried pipeline were discussed. The results show that there are three high stress areas on the buried pipeline sections where the bending deformation are bigger. High stress area of the compression side is bigger than it on the tensile side, and the tensile strain is bigger than the compression strain in the deformation process. Buried pipeline in the landslide bed with hard soil is prone to fracture. Bigger deformations appear on the pipeline sections that the inside and outside lengths of the interface are 30 m and 10 m, respectively. The maximum displacement of the pipeline is smaller than the landslide displacement for the surrounding soil deformation. Bending deformations and tensile strain of the pipeline increase with the increase in landslide displacement. Bending deformation and the maximum tensile strain of the pipeline increase with increasing of the soil's elasticity modulus, cohesion, and pipeline's diameter–thickness ratio. Soil's Poisson's ratio has a great effect on the displacement of the middle part, but it has a little effect on other sections' displacement.

Numerical Analysis of Mechanical Behavior of Buried Pipes in Subsidence Area Caused by Underground Mining

2019 ◽  
Vol 141 (2) ◽  
Author(s):  
Jie Zhang ◽  
Rui Xie
Keyword(s):  
Friction Coefficient ◽  
Plastic Strain ◽  
Internal Pressure ◽  
Mechanical Behavior ◽  
Underground Mining ◽  
Axial Strain ◽  
High Stress ◽  
Soil Parameters ◽  
Buried Pipe ◽  
Subsidence Area

The buried pipe crossing the subsidence area is prone to failure. The mechanical behavior of buried pipe in subsidence area was investigated in this paper. Effects of subsidence displacement, pipe parameters and soil parameters on the mechanical behavior were investigated. The results show that high stress appears on the pipe's surface and exceeds the yield strength after the strata subsidence. As subsidence displacement increases, the ranges of high-stress area and displacement increase, and the pipe section changes from a circle to an ellipse. The maximum axial strain occurs on the pipe in no-subsidence area. The maximum plastic strain and ovality of the pipe increase with the increasing of subsidence displacement. The displacement, plastic strain, and ovality of the pipe increase with the increasing of diameter–thickness ratio and buried depth. Internal pressure and friction coefficient has a little effect on the pipe displacement. The ovality decreases as internal pressure increases. The plastic strain and ovality increase with the increasing of the friction coefficient. As the elastic modulus and cohesion of soil increase, the displacement, plastic strain, and ovality of the pipe increase. The effect of Poisson's ratio on the deformation of pipe is small.

An Interlocking Ligamentous Spinal Disk Arthroplasty with Neural Network Infrastructure

2010 ◽  
Vol 7 ◽  
pp. 55-79 ◽  
Author(s):  
Philip Boughton ◽  
James Merhebi ◽  
C. Kim ◽  
G. Roger ◽  
Ashish D. Diwan ◽  
...  
Keyword(s):  
Neural Network ◽  
Finite Element ◽  
Axial Compression ◽  
Wire Array ◽  
Axial Strain ◽  
Compressive Strain ◽  
Niti Wire ◽  
Motion Segment ◽  
Flexion Extension

An elastomeric spinal disk prosthesis design (BioFI™) with vertebral interlocking anchors has been modified using an embedded TiNi wire array. Bioinert styrenic block copolymer (Kraton®) and polycarbonate urethane (Bionate®) thermoplastic elastomer (TPE) matrices were utilized. Fatigue resistant NiTi wire was pretreated to induce superelastic martensitic microstructure. Stent-like helical structures were produced for incorporation within homogenous TPE matrix. Composite prototypes were fabricated in a vacuum hot press using transfer moulding techniques. Implant prototypes were subject to axial compression using a BOSE ® ELF3400. The NiTi reinforced implants exhibited reduction in axial strain, compliance, and creep compared to TPE controls. The axial properties of the NiTi reinforced Bionate® BioFI™ implant best approximated those of a spinal disk followed by Kraton®-NiTi, Bionate® and Kraton® prototypes. An ovine lumbar segment biomechanical model was used to characterize the disk prosthesis prototypes. Specimens were subject to 7.5Nm pure moments in axial rotation, flexion-extension and lateral bending with a custom jig mounted on an Instron® 8874. The motion preserving ligamentous nature of this arthroplasty prototype was not inhibited by NiTi reinforcement. Joint stiffness for all prototypes was significantly less than the intact and discectomy controls. This was due to lack of vertebral anchor rigidity rather than BioFI™ motion segment matrix type or reinforcement. Implant stress profiles for axial compression and axial torsion conditions were obtained using finite element methods. The biomechanical testing and finite element modelling both support existing BioFI™ design specifications for higher modulus vertebral anchors, endplates and motion segment periphery with gradation to a low modulus core within the motion segment. This closer approximation of the native spinal disk form translates to improvements in prosthesis biomechanical fidelity and longevity. Axial compressive strain induced within a TiNi reinforced Kraton® BioFI™ was found to be linearly proportional to the NiTi helical coil electrical resistance. This neural network capability delivers opportunities to monitor and telemeterize in situ multiaxis joint structural performance and in vivo spine biomechanics.

Permafrost Hazard of MoHe-DaQing Crude Oil Pipeline

2013 ◽  
Vol 734-737 ◽  
pp. 2659-2663
Author(s):  
Yun Bin Ma ◽  
Dong Jie Tan ◽  
Hong Yuan Jing ◽  
Quan Xue ◽  
Cheng Zhi Zhang
Keyword(s):  
Crude Oil ◽  
The Other ◽  
Frost Heave ◽  
Permafrost Soil ◽  
Buried Pipeline ◽  
Soil Frost ◽  
Plastic Deformations ◽  
Oil Pipeline ◽  
Thaw Settlement ◽  
Slope Instabilities

The crude oil pipeline from MoHe to DaQing (hereafter called Mo-Da pipeline) is part of China-Russia oil pipeline. Mo-Da pipeline is the first pipeline that through high latitude cold regions of China. The pipeline is in so complicated geography environment that many kinds of permafrost hazard are easily to happen including frost heave, thaw settlement, slope instabilities, and collapse and so on. The pipeline and the permafrost act and react upon one another. On one hand, soil frost heave and thaw settlement can produce extra stresses on pipe walls, which may result in centralized stresses and plastic deformations under certain conditions, even causes pipeline faults. On the other hand, buried pipeline will disturb ambient environment and then degrade the permafrost soil and finally impact safety of the pipeline. This paper mainly introduces the permafrost hazards of Mo-Da pipeline and demonstrates some methods for monitoring the influence of permafrost.

The Influence of Switch Temperature on Coke Drum Fatigue Life

2010 ◽  
Author(s):  
Fa´bio de Castro Marangone ◽  
Ediberto Bastos Tinoco ◽  
Carlos Eduardo Simo˜es Gomes
Keyword(s):  
Fatigue Life ◽  
Structural Model ◽  
High Stress ◽  
Axial Direction ◽  
Pressure Vessels ◽  
High Stress Concentration ◽  
Short Period ◽  
Bending Stresses ◽  
Switch Temperature ◽  
Lower Temperature

Coke drums are thin-walled pressure vessels that experience severe thermal cycling condition which consists of heating, filling and rapidly cooling the drum in a short period of time. After some years under operation, cracks at the vessel may occur, especially at high stress concentration areas such as the skirt support to shell attachment. During the filling phase of the cycle, when the empty and cooled coke drum is filled with hot oil, the shell and cone temperatures increase rapidly compared to the skirt temperature and the last is pushed outward, since its bottom is at lower temperature and fixed at a concrete base. During quenching (sudden cooling) phase, the coke drum is filled with water at about 80°C and tends to cool faster than the skirt, which is pulled inward until equilibrium is obtained. The skirt expansion and contraction movement results in bending stresses in axial direction on the top of skirt. As lower the switch temperature is, more severe is the bending effect. One of PETROBRAS delayed coke unit presented some operational problems at pre-heating phase, resulting in lower switch temperatures. This paper presents an analysis showing the influence of the switch temperature on coke drum fatigue life. At first, the transient loading conditions were established from thermocouple measurements at skirt attachment weld (hot box region). Later, a transient thermal analysis was performed with FEA and the temperature gradient at the skirt attachment during entire thermal cycle was obtained. The thermal results were then converted to a structural model which was solved for linear elastic stress including other loads such as pressure. Finally, the maximum stress components for both filling and quenching phases were determined and a complete stress range was calculated as per ASME Section VIII, Div 2. The procedure described above was applied for different switch temperatures scenarios in order to show its influence on the fatigue life of the coke drum.

Performance of Multifiber Beam Element for Seismic Analysis of Reinforced Concrete Structures

2014 ◽  
Vol 14 (06) ◽  
pp. 1450013 ◽  
Author(s):  
Xuan Huy Nguyen
Keyword(s):  
Reinforced Concrete ◽  
Damage Mechanics ◽  
Seismic Analysis ◽  
Axial Strain ◽  
Nonlinear Behavior ◽  
Bending Moment ◽  
Axial Direction ◽  
Beam Element ◽  
Shaking Table ◽  
Rc Structures

This paper presents a simplified modeling strategy for simulating the nonlinear behavior of reinforced concrete (RC) structures under seismic loadings. A new type of Euler–Bernoulli multifiber beam element with axial force and bending moment interaction is introduced. To analyze the behavior of RC structures in the axial direction, the interpolation of the axial strain is enriched using the incompatible modes method. The model uses the constitutive laws based on plasticity for steel and damage mechanics for concrete. The proposed multifiber element is implemented in the finite element Code_Aster to simulate the nonlinear behavior of two different RC structures. One structure is a building tested on a shaking table; the other is a column subjected to cyclic loadings. The comparison between the simulation and experimental results shows that the performance of this approach is quite good. The proposed model can be used to investigate the behavior of a wider variety of configurations which are impossible to study experimentally.

Microstructural Characterization of Creep Tested Cryomilled NiAl-13vol. % AlN

1994 ◽  
Vol 350 ◽  
Author(s):  
A. Garg ◽  
J. D. Whittenberger ◽  
B. J. M. Aikin
Keyword(s):  
Steady State ◽  
Compressive Strain ◽  
High Stress ◽  
Microstructural Characterization ◽  
Dislocation Network ◽  
Stress Regime ◽  
Stress Diagram ◽  
Superior Mechanical Properties ◽  
Power Law Creep

AbstractCryomilling of prealloyed NiAl powders, followed by extrusion, has been used to produce a particulate strengthened NiAl-13vol.% AlN material. At 1300 K, the compressive strain rate-flow stress diagram has two distinct deformation regimes, with the transition occurring near 150 MPa. The low and the high stress regimes have power law creep exponents of ∼ 6.1 and 14.2, respectively. Microstructural characterization of the as-extruded and tested samples has been performed to develop an understanding of the superior mechanical properties of the material. The microstructure of the as-extruded material was inhomogeneous and consisted of mantle regions containing a mixture of small NiAl grains (diameter ∼ 50–150 nm) and fine AlN particles (size ∼ 5–50 nm) that surround larger NiAl grains (diameter ∼ 0.3–8.0 μm) which were mostly particle free. In the low-stress regime, samples tested to steady state exhibited a structure composed of subgrain boundaries in the particle-free NiAl grains. In addition, some of the subgrains had developed a well defined dislocation network. AlN patricles occasionally found within large NiAl grains acted as pinning centers for dislocations. Small NiAl grains and the AlN particles constituting the mantle coarsened during these tests. In the high-stress regime, samples tested to steady state exhibited a high density of dislocations in most of the particle-free NiAl grains. Subgrain boundaries were found occasionally but dislocation networks were rare. The AlN particles had not significantly coarsened due to the shorter times at temperature.

scholarly journals Further Insight into the Depth-Dependent Microstructural Response of Cartilage to Compression Using a Channel Indentation Technique

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Ashvin Thambyah ◽  
Neil D. Broom
Keyword(s):  
Stress Relaxation ◽  
Axial Strain ◽  
Compressive Strain ◽  
Microstructural Analysis ◽  
Elastic Response ◽  
Axial Deformation ◽  
Aspect Ratios ◽  
The Matrix ◽  
Tissue System ◽  
Relaxation Responses

Stress relaxation and structural analysis were used to investigate the zonally differentiated microstructural response to compression of the integrated cartilage-on-bone tissue system. Fifteen cartilage-on-bone samples were divided into three equal groups and their stress relaxation responses obtained at three different levels of axial compressive strain defined as low (~20%), medium (~40%) and high (~60%). All tests were performed using a channel indenter which included a central relief space designed to capture the response of the matrix adjacent to the directly loaded regions. On completion of each stress relaxation test and while maintaining the imposed axial strain, the samples were formalin fixed, decalcified, and then sectioned for microstructural analysis. Chondron aspect ratios were used to determine the extent of relative strain at different zonal depths. The stress relaxation response of cartilage to all three defined levels of axial strain displayed an initial highly viscous response followed by a significant elastic response. Chondron aspect ratio measurements showed that at the lowest level of compression, axial deformation was confined to the superficial cartilage layer, while in the medium and high axial strain samples the deformation extended into the midzone. The cells in the deep zone remained undeformed for all compression levels.

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