Stress Analysis of Pipeline Subjected to Differential Frost Heave

2013 ◽  
Author(s):  
Yan Di ◽  
Jian Shuai ◽  
Lingzhen Kong ◽  
Xiayi Zhou
Keyword(s):  
Strain Analysis ◽  
Element Model ◽  
Frozen Soil ◽  
Computational Method ◽  
Frost Heave ◽  
Safe Operation ◽  
Stress Strain ◽  
Segregation Potential ◽  
Differential Frost Heave ◽  
Design Construction

Frost heave must be considered in cases where pipelines are laid in permafrost in order to protect the pipelines from overstress and to maintain the safe operation. In this paper, a finite element model for stress/strain analysis in a pipeline subjected to differential frost heave was presented, in which the amount of frost heave is calculated using a segregation potential model and considering creep effects of the frozen soil. In addition, a computational method for the temperature field around a pipeline was proposed so that the frozen depth and temperature variation gradient could be obtained. Using the procedure proposed in this paper, stress/strain can be calculated according to the temperature on the surface of soil and in a pipeline. The result shows the characteristics of deformation and loading of a pipeline subjected to differential frost heave. In general, the methods and results in this paper can provide a reference for the design, construction and operation of pipelines in permafrost areas.

Delamination in the scoring and folding of paperboard

TAPPI Journal ◽  
2012 ◽  
Vol 11 (1) ◽  
pp. 61-66 ◽  
Author(s):  
DOEUNG D. CHOI ◽  
SERGIY A. LAVRYKOV ◽  
BANDARU V. RAMARAO
Keyword(s):  
Finite Element ◽  
Plane Deformation ◽  
Strain Analysis ◽  
Local Strain ◽  
Uniaxial Stress ◽  
Material Model ◽  
Element Model ◽  
Plastic Behavior ◽  
Stress Strain ◽  
Strain Fields

Delamination between layers occurs during the creasing and subsequent folding of paperboard. Delamination is necessary to provide some stiffness properties, but excessive or uncontrolled delamination can weaken the fold, and therefore needs to be controlled. An understanding of the mechanics of delamination is predicated upon the availability of reliable and properly calibrated simulation tools to predict experimental observations. This paper describes a finite element simulation of paper mechanics applied to the scoring and folding of multi-ply carton board. Our goal was to provide an understanding of the mechanics of these operations and the proper models of elastic and plastic behavior of the material that enable us to simulate the deformation and delamination behavior. Our material model accounted for plasticity and sheet anisotropy in the in-plane and z-direction (ZD) dimensions. We used different ZD stress-strain curves during loading and unloading. Material parameters for in-plane deformation were obtained by fitting uniaxial stress-strain data to Ramberg-Osgood plasticity models and the ZD deformation was modeled using a modified power law. Two-dimensional strain fields resulting from loading board typical of a scoring operation were calculated. The strain field was symmetric in the initial stages, but increasing deformation led to asymmetry and heterogeneity. These regions were precursors to delamination and failure. Delamination of the layers occurred in regions of significant shear strain and resulted primarily from the development of large plastic strains. The model predictions were confirmed by experimental observation of the local strain fields using visual microscopy and linear image strain analysis. The finite element model predicted sheet delamination matching the patterns and effects that were observed in experiments.

Microstructure-Based Random Finite Element Method Simulation of Frost Heave: Theory and Implementation

2018 ◽  
Vol 2672 (52) ◽  
pp. 347-357 ◽  
Author(s):  
Shaoyang Dong ◽  
Xiong (Bill) Yu
Keyword(s):  
Finite Element ◽  
Ground Surface ◽  
Finite Element Method Simulation ◽  
Element Model ◽  
Frozen Soil ◽  
Traffic Load ◽  
Frost Heave ◽  
Holistic Model ◽  
Water Pipes ◽  
Random Finite Element

Frost heave can cause serious damage to civil infrastructure. For example, interactions of soil and water pipes under frozen conditions have been found to significantly accelerate pipe fracture. Frost heave may cause the retaining walls along highways to crack and even fail in cold climates. This paper describes a holistic model to simulate the temperature, stress, and deformation in frozen soil and implement a model to simulate frost heave and stress on water pipelines. The frozen soil behaviors are based on a microstructure-based random finite element model, which holistically describes the mechanical behaviors of soils subjected to freezing conditions. The new model is able to simulate bulk behaviors by considering the microstructure of soils. The soil is phase coded and therefore the simulation model only needs the corresponding parameters of individual phases. This significantly simplifies obtaining the necessary parameters for the model. The capability of the model in simulating the temperature distribution and volume change are first validated with laboratory scale experiments. Coupled thermal-mechanical processes are introduced to describe the soil responses subjected to sub-zero temperature on the ground surface. This subsequently changes the interaction modes between ground and water pipes and leads to increase of stresses on the water pipes. The effects of cracks along a water pipe further cause stress concentration, which jeopardizes the pipe’s performance and leads to failure. The combined effects of freezing ground and traffic load are further evaluated with the model.

Stress Strain Analysis of Steel Specimens Not Wholly Quenched

2011 ◽  
Vol 261-263 ◽  
pp. 702-706
Author(s):  
Rui Jie Wang ◽  
He Ming Cheng ◽  
Bao Dong Shao ◽  
Jian Yun Li
Keyword(s):  
Finite Element ◽  
Fatigue Crack Initiation ◽  
Strain Analysis ◽  
Element Model ◽  
Cyclic Strength ◽  
Work Piece ◽  
Stress Strain ◽  
Element Analysis ◽  
Quenched Steel ◽  
Crack Initiation Life

A finite element model of not wholly quenched steel fatigue specimen is established. Hardness value of some distance to work piece surface are assumed different and cyclic strength coefficients of different zones are different, both is assumed to be proportional to hardness value. Elasto-plastic finite element analysis was carried out for this model. According to the stress-strain distribution on transverse section, the effect of not wholly quenched on fatigue crack initiation life is analyzed.

Study on Stress Strain in UG-Based Fatigue Analysis of Piston Pin

2013 ◽  
Vol 676 ◽  
pp. 145-148
Author(s):  
Hong Ying Wang ◽  
Wei Guo
Keyword(s):  
Boundary Condition ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Strain Analysis ◽  
Fatigue Analysis ◽  
Computational Method ◽  
Analysis Method ◽  
Stress Strain ◽  
Element Analysis ◽  
Conventional Algorithm

Carried on finite element analysis using the UG software to finally carry on the fatigue life’s computational method to carry on the exploration and the research. when carrying on the finite element stress strain analysis to the piston pin, used the different analysis method, because the piston pin’s quality is very slightly oppositeing to the piston quality, produces the force of inertia is very small, the counter stress computed result is not very obvious, therefore to piston pin finite element analysis we uses conventional algorithm that infliction boundary condition.

Influence of overconsolidation on the freezing characteristics of a clayey silt

1989 ◽  
Vol 26 (1) ◽  
pp. 9-21 ◽  
Author(s):  
J.-M. Konrad
Keyword(s):  
Hydraulic Conductivity ◽  
Void Ratio ◽  
Moisture Transfer ◽  
Frozen Soil ◽  
Frost Heave ◽  
Unfrozen Water ◽  
Initial Void Ratio ◽  
Clayey Silt ◽  
Segregation Potential ◽  
Lens Formation

Laboratory freezing tests were performed on a saturated clayey silt at various overconsolidation ratios (OCR) to establish the relationship between initial void ratio and stress history, and the amount of moisture transfer during freezing. The frost heave tests were analysed in terms of the segregation potential as well as a function of the temperature of ice lens formation and the overall hydraulic conductivity of the frozen fringe. All other factors being the same, the segregation potential was found to increase with increasing values of OCR (decreasing initial void ratios). However, the combined effects of decreasing void ratio and increasing suction at the frost line, all other factors being identical in all freezing tests, resulted in decreasing segregation potentials. This trend was the result of a decrease in the temperature of ice lens formation and the concomitant decrease in overall hydraulic conductivity of the frozen fringe. A simple model showed that the capillary unfrozen water between clay particles increases when the particles pack closer together, as overconsolidation increases, allowing the migratory water to freeze within the frozen soil at a colder temperature. Key words: frost heave, clayey silt, overconsolidation, void ratio.

Frost heave and thaw consolidation modelling. Part 1: A water flux function for frost heaving

2020 ◽  
Vol 57 (10) ◽  
pp. 1581-1594 ◽  
Author(s):  
Fan Yu ◽  
Peijun Guo ◽  
Yuanming Lai ◽  
Dieter Stolle
Keyword(s):  
Water Flux ◽  
Experimental Studies ◽  
Rate Function ◽  
Frozen Soil ◽  
Frost Heave ◽  
Volume Distribution ◽  
Freezing And Thawing ◽  
Flux Function ◽  
Thaw Consolidation ◽  
Segregation Potential

Although much effort has been made to develop various frost heave models in the past decades, a simple yet versatile model is still needed for engineering applications. This paper presents a method to estimate frost heave in frozen soil using a macroscopic water flux function that extends the segregation potential to make it applicable for both steady state and transient freezing and thawing states. The formation of an individual ice lens is modelled by combining previously developed stress and strain criteria. The water flux function, which includes various factors in accordance with the porosity rate function, can describe the growth of both new and old ice lenses. More importantly, every component of the water flux function is physically explained by the theory of pre-melting dynamics, where all the influencing factors are traced back to their impacts on the ice volume distribution. The performance of the model is demonstrated via simulations of one-dimensional freezing and thawing processes after the model is validated by a specific case from previous literature. Although adequate data are not available for a stricter experimental verification of the model, it is observed that the simulations predict the general course of events together with significant specific features that were identified in previous experimental studies.

Modelling of pipeline under differential frost heave considering post-peak reduction of uplift resistance in frozen soil

2006 ◽  
Vol 43 (3) ◽  
pp. 282-293 ◽  
Author(s):  
Bipul C Hawlader ◽  
Vincent Morgan ◽  
Jack I Clark
Keyword(s):  
Analytical Solution ◽  
Frozen Soil ◽  
Frost Heave ◽  
Large Strains ◽  
Peak Reduction ◽  
Numerical Predictions ◽  
Discontinuous Permafrost ◽  
Nonlinear Stress ◽  
Uplift Resistance ◽  
Differential Frost Heave

The interaction between buried chilled gas pipelines and the surrounding frozen soil subjected to differential frost heave displacements has been investigated. A simplified semi-analytical solution has been developed considering the post-peak reduction of uplift resistance in frozen soil as observed in laboratory tests. The nonlinear stress–strain behaviour of the pipeline at large strains has been incorporated in the analysis using an equivalent bending stiffness. The predicted results agree well with our finite element analysis and also with numerical predictions available in the literature, hence the simple semi-analytical solution can be considered as an alternative to numerical techniques. A parametric study has been carried out to identify the influence of key factors that can modify the uplift resistance in frozen soil. Among them, the residual uplift resistance has been found to be the important parameter for the development of stresses and strains in the pipeline.Key words: pipeline, frost heave, discontinuous permafrost, semi-analytical solution, uplift resistance, frozen soil.

Discrete ice lens theory for frost heave in soils

1991 ◽  
Vol 28 (6) ◽  
pp. 843-859 ◽  
Author(s):  
J. F. (Derick) Nixon
Keyword(s):  
Hydraulic Conductivity ◽  
Temperature Gradient ◽  
Frozen Soil ◽  
Soil Freezing ◽  
Frost Heave ◽  
Overburden Pressure ◽  
Discrete Location ◽  
Freezing Soil ◽  
Analytical Technique ◽  
Segregation Potential

The existing segregation potential (SP) method for frost heave prediction in soils is semiempirical in nature and does not explicitly predict the relationship between heave rate, temperature gradient, and other more fundamental soil properties. The SP method assumes that the heave rate is directly related to the temperature gradient at the frost front but acknowledges that the SP parameter is dependent on pressure, suction at the frost front, cooling rate, soil type, and so forth. This paper extends and modifies an approximate analytical technique of Gilpin and accounts for the effects of distributed phase change within the freezing fringe in both the head- and mass-transfer components of the formulation. The approach requires as input a relationship between frozen hydraulic conductivity and temperature and predicts the discrete location of each ice lens within the freezing soil. The solution can be carried out quickly on a microcomputer to obtain the heave, suction at the frost front, ice lens temperature, and other results of interest with time. Furthermore, the discrete ice lens method predicts the effects of changing overburden pressure on the predicted heave rate. A method of extracting input parameters for the discrete ice lens procedure from a series of frost heave tests is proposed. The discrete ice theory has been tested and calibrated against well-documented frost heave test results in the literature, and very encouraging agreement between prediction and observation has been obtained. Key words: frost heave, discrete ice lens, segregation potential, hydraulic conductivity of frozen soil, freezing soil.

Frost heave – pipeline interaction using continuum mechanics

1983 ◽  
Vol 20 (2) ◽  
pp. 251-261 ◽  
Author(s):  
J. F. Nixon ◽  
N. R. Morgenstern ◽  
S. N. Reesor
Keyword(s):  
Continuum Mechanics ◽  
Applied Pressure ◽  
Soil Mass ◽  
Structural Member ◽  
Frozen Soil ◽  
Frost Heave ◽  
Flexible Pipe ◽  
Frozen Ground ◽  
Frost Heaving ◽  
Differential Frost Heave

As a chilled pipeline crosses a transition from frozen to unfrozen ground or shallow permafrost, a differential frost heave problem may develop causing strains in the pipe. Soil–structure interaction models that are currently available to handle this problem concentrate on the pipe as the dominant structural member and represent the soil mass as a series of unconnected springs. This paper considers the soil to be an elastic or nonlinear viscous continuum and imposes a nonlinear boundary condition to represent the frost heaving soil and the dependence of frost heave on applied pressure. The pipe is assumed to be a completely passive structural member and the soil strains at the pipe elevations are studied. The dependence of the maximum pipe strains on the length of the heaving section and on the thickness of frozen ground beneath the pipe have been established for a typical set of soil and frost heaving conditions. It is found that, for the conditions studied, when the thickness of shallow permafrost or frozen soil is greater than about 7–8 m, the strains that a flexible pipe experiences are less than the strain criteria currently in use on many pipeline projects. Keywords: frost heave, pipeline, interaction, stress analysis, finite elements, continuum mechanics, thermo-elasticity.

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