scholarly journals Failure Assessment for the High-Strength Pipelines with Constant-Depth Circumferential Surface Cracks

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
X. Liu ◽  
Z. X. Lu ◽  
Y. Chen ◽  
Y. L. Sui ◽  
L. H. Dai
Keyword(s):  
Finite Element ◽  
Practical Interest ◽  
High Strength ◽  
Influence Functions ◽  
Surface Cracks ◽  
Constant Depth ◽  
Long Distance ◽  
Integrity Assessment ◽  
Failure Assessment ◽  
Bending Loads

In the oil and gas transportation system over long distance, application of high-strength pipeline steels can efficiently reduce construction and operation cost by increasing operational pressure and reducing the pipe wall thickness. Failure assessment is an important issue in the design, construction, and maintenance of the pipelines. The small circumferential surface cracks with constant depth in the welded pipelines are of practical interest. This work provides an engineering estimation procedure based upon the GE/EPRI method to determine the J-integral for the thin-walled pipelines with small constant-depth circumferential surface cracks subject to tension and bending loads. The values of elastic influence functions for stress intensity factor and plastic influence functions for fully plastic J-integral estimation are derived in tabulated forms through a series of three-dimensional finite element calculations for different crack geometries and material properties. To check confidence of the J-estimation solution in practical application, J-integral values obtained from detailed finite element (FE) analyses are compared with those estimated from the new influence functions. Excellent agreement of FE results with the proposed J-estimation solutions for both tension and bending loads indicates that the new solutions can be applied for accurate structural integrity assessment of high-strength pipelines with constant-depth circumferential surface cracks.

scholarly journals Improved J Estimation by GE/EPRI Method for the Thin-Walled Pipes With Small Constant-Depth Circumferential Surface Cracks

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
X. Liu ◽  
Z. X. Lu ◽  
Y. Chen ◽  
Y. L. Sui ◽  
L. H. Dai
Keyword(s):  
Influence Functions ◽  
J Integral ◽  
Surface Cracks ◽  
Constant Depth ◽  
Long Distance ◽  
Small Constant ◽  
Wide Range ◽  
Thin Walled ◽  
Plastic Influence Functions ◽  
J Estimation

Application of thin-walled high strength steel has become a trend in the oil and gas transportation system over long distance. Failure assessment is an important issue in the construction and maintenance of the pipelines. This work provides an engineering estimation procedure to determine the J-integral for the thin-walled pipes with small constant-depth circumferential surface cracks subject to the tensile loading based upon the General Electric/Electric Power Research (GE/EPRI) method. The values of elastic influence functions for stress intensity factor and plastic influence functions for fully plastic J-integral are derived in tabulated forms through a series of three-dimensional (3D) finite element (FE) calculations for a wide range of crack geometries and material properties. Furthermore, the fit equations for elastic and plastic influence functions are developed, where the effects of crack geometries are explicitly revealed. The new influence functions lead to an efficient J estimation and can be well applied for structural integrity assessment of thin-walled pipes with small constant-depth circumferential surface cracks under tension.

Modification Strain-Based Failure Assessment Diagram for High Strength Pipeline Steel

2016 ◽  
Vol 853 ◽  
pp. 33-40
Author(s):  
Jun Lin Shi ◽  
Jian Ping Zhao ◽  
Wei Jie Jiang
Keyword(s):  
Finite Element ◽  
Material Properties ◽  
Pipeline Steel ◽  
High Strength ◽  
Plastic Strains ◽  
Failure Assessment Diagram ◽  
Failure Assessment ◽  
High Plastic

The strain-based failure assessment diagram (SB-FAD) has been developed to predict failure due to high plastic strains. This paper validates the SB-FAD by finite element results for high strength pipeline steel (X80, X80HD, and X90) with four representative specimens (CT, CCP, DECP, and SCEP) of different crack sizes, respectively. The influence of material properties, geometries and crack sizes on failure assessment curves were compared and analyzed. Meanwhile, the modified Option-1 curve of SB-FAD is given in this paper. The results showed that the modified Option-1 curve of SB-FAD is more accurate when the value of abscissais Dr small and more conservative when the value of abscissa Dr is large.

Analysis of Interaction Behavior of Surface Flaws in Pressure Vessels

1986 ◽  
Vol 108 (1) ◽  
pp. 24-32 ◽  
Author(s):  
P. E. O’Donoghue ◽  
T. Nishioka ◽  
S. N. Atluri
Keyword(s):  
Finite Element ◽  
Stress Intensity ◽  
Pressure Vessels ◽  
Influence Functions ◽  
Surface Cracks ◽  
Intensity Factors ◽  
Alternating Method ◽  
Circumferential Crack ◽  
Magnification Factors ◽  
Surface Flaws

The evaluation of stress intensity factors for surface flaw problems and, in particular, semi-elliptical surface cracks in cylindrical pressure vessels has been well developed using the finite element alternating method. Some of the examples presented here include the interaction effects due to multiple internal longitudinal surface cracks in cylinders as recommended for analysis in the ASME Boiler and Pressure Vessel Code (Section XI). For each crack geometry, several loading cases are considered including internal pressure and polynomial pressure loadings from constant to fourth order. By the method of superposition, the magnification factors for internally pressurized cylinders are rederived using the polynomial influence functions. These influence functions give useful information for design purposes such as in the analysis of a thermally shocked cylinder. The problem of a single circumferential crack in a cylinder is also investigated using the finite element alternating method, and a number of results for such problems are also presented here.

Experimental Measurement and Finite Element Analysis of Screw Spike Fatigue Loads

2007 ◽  
Author(s):  
Matthew G. Dick ◽  
David S. McConnell ◽  
Hans C. Iwand
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Fatigue Failure ◽  
High Strength Steels ◽  
High Strength ◽  
Element Model ◽  
Element Analysis ◽  
Bending Fatigue ◽  
Fea Model ◽  
Bending Loads

Screw spikes, also known as coach screws, are an advanced alternative to common cut spikes for track fastening. Despite their ability to secure tie plates with a clamp load and utilization of high strength steels, they are still susceptible to bending fatigue failure from lateral wheel loads. A novel method of measuring these bending loads on screw spikes was developed and implemented to characterize the load environment of the screw spikes. Results indicated that measured peak bending loads under lateral wheel loads reached as high as 10,000 lbs for individual spikes, while others carried no load whatsoever. A finite element model was developed to determine the tensile stress fields created by the measured bending loads. A good correlation was found between the FEA model predicted point of highest stress and the location of fracture. Through the testing and analysis it was determined that lateral wheel loads are not distributed evenly among the four screw spikes of a single tie plate. Instead, it was found that one spike carried nearly no load while the spike opposite of it carried more load. Using the finite element analysis it was determined that the spike exposed to the higher loading was subjected to tensile stresses above its endurance limit, which would eventually lead to a bending fatigue failure.

Compressor Issues for Hydrogen Production and Transmission Through a Long Distance Pipeline Network

2008 ◽  
Vol 59 (4) ◽  
Author(s):  
Fred Starr ◽  
Calin-Cristian Cormos ◽  
Evangelos Tzimas ◽  
Stathis Peteves
Keyword(s):  
Pressure Ratio ◽  
High Strength Steels ◽  
High Strength ◽  
Energy System ◽  
Pipeline System ◽  
Hydrogen Energy ◽  
Long Distance ◽  
System Pressure ◽  
Production Of Hydrogen ◽  
Plant Exit

A hydrogen energy system will require the production of hydrogen from coal-based gasification plants and its transmission through long distance pipelines at 70 � 100 bar. To overcome some problems of current gasifiers, which are limited in pressure capability, two options are explored, in-plant compression of the syngas and compression of the hydrogen at the plant exit. It is shown that whereas in-plant compression using centrifugal machines is practical, this is not a solution when compressing hydrogen at the plant exit. This is because of the low molecular weight of the hydrogen. It is also shown that if centrifugal compressors are to be used in a pipeline system, pressure drops will need to be restricted as even an advanced two-stage centrifugal compressor will be limited to a pressure ratio of 1.2. High strength steels are suitable for the in-plant compressor, but aluminium alloy will be required for a hydrogen pipeline compressor.

Composite Solutions for Deck Catamarans

2018 ◽  
Vol 55 (1) ◽  
pp. 1-4
Author(s):  
Elena Felicia Beznea ◽  
Ionel Chirica ◽  
Adrian Presura ◽  
Ionel Iacob
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Sandwich Structure ◽  
High Strength ◽  
Total Weight ◽  
External Loading ◽  
Strength Analysis ◽  
Allowable Stress ◽  
The Finite Element Method ◽  
Inland Navigation

The paper is treating the strength analysis of the main deck structure of an inland navigation catamaran for 30 passengers. The main deck should have high stiffness and high strength to resist to external loading and endure high stresses from combined bending and torsion loads. Different materials for sandwich structure of the deck have been analysed by using the Finite Element Method in order to determine the solution which accomplish better designing criteria regarding allowable stress and deformations and total weight.

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