The Influence of In-Plane Constraint on Void Behavior in Front of a Crack in Plane Strain

2014 ◽  
Vol 224 ◽  
pp. 139-144
Author(s):  
Jaroslaw Galkiewicz
Keyword(s):  
Boundary Layer ◽  
Plane Strain ◽  
Plastic Material ◽  
Three Dimensional ◽  
Plane Strain Condition ◽  
Strain Condition ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Elastic Plastic ◽  
Elastic Plastic Material

This paper investigates voids’ behavior in front of a crack in elastic-plastic material under plane strain condition. Using the modified boundary layer approach for selected values of Q-stress it evaluates the deformations of a material cell. The deformations are recomputed with an exact three-dimensional model.

Influence of Lined Pipe Fabrication on Liner Wrinkling

2019 ◽  
Author(s):  
Ilias Gavriilidis ◽  
Spyros A. Karamanos
Keyword(s):  
Plastic Material ◽  
Numerical Models ◽  
Three Dimensional ◽  
Local Buckling ◽  
Short Wave ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Imperfection Sensitivity ◽  
Elastic Plastic ◽  
Outer Pipe

Abstract An economical method to protect offshore pipelines against corrosive ingredients of hydrocarbons is a double-walled (also called “lined” or “bi-metallic”) pipe, in which a thick-walled low-alloy carbon steel (“outer pipe”) is lined internally with a thin layer (“liner pipe”) from a corrosion resistant alloy material. During the deep-water installation, a lined pipe is subjected to severe plastic loading, which may result in detachment of the liner pipe from the outer pipe forming short-wave wrinkles, followed by local buckling. In the current study, alternative lined pipe manufacturing processes are investigated, including elastic, plastic hydraulic and thermo-hydraulic expansion of the outer pipe, for different initial gaps between the two pipes. The problem is solved numerically, accounting for geometric non-linearities, local buckling phenomena and elastic-plastic material behaviour for both the liner and outer pipe. Two types of numerical models are developed, a quasi-two-dimensional model, examining the mechanical bonding between the pipes, and a three-dimensional model, repeating the manufacturing process and investigating its effect on the mechanical behaviour of a lined pipe subjected to monotonic bending. In addition, the influence of initial geometric imperfections on liner pipe buckling is investigated, showing the imperfection sensitivity of the lined pipe bending behaviour, for each fabrication process.

The Use of Subgrid Transport Equations in a Three-Dimensional Model of Atmospheric Turbulence

1973 ◽  
Vol 95 (3) ◽  
pp. 429-438 ◽  
Author(s):  
J. W. Deardorff
Keyword(s):  
Boundary Layer ◽  
Three Dimensional ◽  
Transport Equations ◽  
Subgrid Scale ◽  
Reynolds Stresses ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Truncation Errors ◽  
Subgrid Scales ◽  
Grid Points

A three-dimensional numerical model of turbulence in an atmospheric boundary layer has been revised to utilize subgrid transport equations for the subgrid Reynolds stresses and fluxes rather than subgrid eddy coefficients. It was applied to a daytime boundary layer over heated ground in a region of horizontal area 8km square and 2km deep, utilizing 40×40×40 grid points. The constraints involved in selecting four important subgrid closure constants are discussed in some detail, along with maintenance of realizability on the subgrid scale. The results indicate that the subgrid transport equations produce subgrid Reynolds stresses and fluxes which realistically simulate the transfer of larger scale variance to subgrid scales, provided truncation errors due to advective terms are not too large. They also show the superiority of this method over the use of (nonstability dependent) nonlinear eddy coefficients in maintaining the sharpness of the inversion base which lies above the mixed layer.

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