Statistical Approach of Stress Concentration Factor (SCF) Within Pipeline Girth Welds

2014 ◽  
Author(s):  
Pierre-Louis Auvret ◽  
Antonio Carlucci ◽  
Jun Li ◽  
Kamel MCirdi
Keyword(s):  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Material Behavior ◽  
Stress Concentrations ◽  
Alignment Procedure ◽  
Fabrication Tolerances ◽  
Girth Welds ◽  
Pipe Size

Engineering design must take care of local peaks within stress field, in order to provide relevant forecast of material behavior. Within pipeline girth welds, pipe misalignment is an ordinary cause of significant stress concentrations. The matching of pipe ends depends of the quality of alignment procedure but it is also much influenced by pipe fabrication tolerances. In general, misalignment is estimated considering the maximal and minimal values of each pipe size according to pipe fabrication tolerances. But, in practice, the probability to get a such case is very low. This paper describes how to improve the calculation of stress concentration factor (SCF) through a statistical analysis of pipe dimensions. The use of actual pipe measurements is not necessary even if it provides better SCF estimation. Indeed the distribution of pipe size can be estimated through the fabrication tolerances which require acceptable capacities of the manufacturing system.

Analysis of strain and stress concentrations in micro-lattice structures manufactured by SLM

2019 ◽  
Vol 26 (2) ◽  
pp. 370-380 ◽  
Author(s):  
Laura Boniotti ◽  
Stefano Foletti ◽  
Stefano Beretta ◽  
Luca Patriarca
Keyword(s):  
Mechanical Properties ◽  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Image Correlation ◽  
Stress Concentrations ◽  
Content Type ◽  
Lattice Materials ◽  
Geometrical Imperfections

Purpose Additive manufacturing (AM) enables the production of lightweight parts with complex shapes and small dimensions. Recent improvements in AM techniques have allowed a significant growth of AM for industrial applications. In particular, AM is suitable for the production of materials shaped in lattice, which are very attractive for their lightweight design and their multi-functional properties. AM parts are often characterised by geometrical imperfections, residual porosity, high surface roughness which typically lead to stress/strain localisations and decreasing the resistance of the structure. This paper aims to focus on the study of the effects of geometrical irregularities and stress concentrations derived from them. Design/methodology/approach In this paper, several technique were combined: 3D tomography, experimental tests, digital image correlation and finite elements (FE) models based on both the as-designed and the as-manufactured geometries of lattice materials. The Digital Image Correlation technique allowed to measure local deformations in the specimen during the experimental test. The micro-computed tomography allowed to reconstruct the as-manufactured geometries of the specimens, from which the geometrical quality of the micro-structure is evaluated to run FE analyses. Findings Experimental and numerical results were compared by means of a stress concentration factor. This factor was calculated in three different specimens obtained from three-different printing processes to compare and understand their mechanical properties. Considering the as-designed geometry, it is not possible to model geometrical imperfections, and a FE model based on an as-manufactured geometry is needed. The results show that the mechanical properties of the printed samples are directly related to the statistical distribution of the stress concentration factor. Originality/value In this work, several techniques were combined to study the mechanical behaviour of lattice micro-structures. Lattice materials obtained by different selective laser melting printing parameters show different mechanical behaviours. A stress concentration factor can be assumed as a measure of the quality of these mechanical properties.

Effect of Blend Radius on Stress Concentration Factor of Crossbored Holes in Thick Walled Pressure Vessels

2003 ◽  
Author(s):  
Daniel T. Peters
Keyword(s):  
Stress Concentration ◽  
Detailed Analysis ◽  
Computer Technology ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Pressure Vessels ◽  
Stress Concentrations ◽  
The Past ◽  
Recent Developments ◽  
Fea Analysis

Many studies have been performed on the effect of stress concentration factor in thick walled cylinders caused by holes drilled to the wall perpendicular to the vessel ID, commonly called crossbores. Recent developments in FEA analysis and computer technology have allowed detailed analysis in their effect on the stresses in pressure vessels. This allows the reevaluation of many theories developed in the past. The following is a study of how applying a blend radius to the inside intersection of a vessel bore and a crossbore affects the stresses in vicinity of the hole and the stress concentrations developed near the hole.

Effect of notch sensitivity on the mechanical properties of HA/PEEK functional gradient biocomposites

2016 ◽  
Vol 36 (9) ◽  
pp. 933-941 ◽  
Author(s):  
Pan Yusong ◽  
Chen Yan ◽  
Shen Qianqian ◽  
Pan Chengling
Keyword(s):  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Orthopedic Implants ◽  
Fracture Morphology ◽  
Notch Sensitivity ◽  
Stress Concentrations ◽  
Stress Strain ◽  
Functional Gradient ◽  
Strain Behavior

Abstract Biomaterials used as loading-bearing orthopedic implants usually require various excellent properties such as mechanical, bioactive and bio-tribological performances. Moreover, all of the orthopedic applications feature stress concentrations (notch sensitivity) in their design. In the present work, hydroxyapatite-reinforced polyetheretherketone functional gradient biocomposites (HA/PEEK FGBm) were successfully prepared by the layer stacking method combined with hot pressing molding technology. The effects of notch geometry on the stress-strain behavior of HA/PEEK FGBm were evaluated. The fracture morphology was investigated by scanning electron microscopy (SEM). The study of the stress-strain behavior indicated that the tensile and flexural stresses of HA/PEEK FGBm linearly increased with increasing strain under all the notch sensitivities. The fracture strain of the biocomposites decreased with increasing stress concentration factor and total HA content in the functional biocomposites. Moreover, the tensile and flexural strengths of HA/PEEK FGBm were lower than those of homogeneous HA/PEEK biocomposites. The SEM observation of the fracture micro-morphology showed that the fracture mechanism of HA/PEEK FGBm was gradually controlled by the brittle fracture process. Furthermore, both the tensile and the flexural strengths of HA/PEEK FGBm decreased with the increase in stress concentration factor and total HA content in the biocomposites.

scholarly journals New Methods for Stress Concentration Factor Calculation in Butt Welded Joints: A Comparative Study

2020 ◽  
Author(s):  
Miroslav Randic ◽  
Duško Pavletić ◽  
Marko Fabić
Keyword(s):  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Welded Joints ◽  
Concentration Factor ◽  
Computer Software ◽  
Base Material ◽  
Geometric Parameters ◽  
Stress Concentrations ◽  
Weld Toe ◽  
Toe Angle

Abstract Surface cracks in butt-welded joints usually occur in places with increased stress concentrations. The stress concentration factor (SCF) can be calculated using an empirical equation, with five geometric parameters of a butt-welded joint (thickness of the base material, toe radius, weld toe angle, weld width, and reinforcement height). However, in anindustrial environment, it is impractical and sometimes even impossible to measure all five geometric parameters with sufficient accuracy. In this study, eight experiments on butt-welded joints were performed. All samples were scanned with a 3D scanner, and the geometric sizes of the welded joints were measured using computer software. A modified empirical expression proposed by Ushirokawa and Nakayama was used to calculate the SCF; the expression was adjusted in such a way that the SCF was calculated by knowing only the toe radius. In addition, four new expressions were proposed for the calculation of the SCF by knowing the toe radius in relation to the weld toe angle; the expressions were then compared and analysed. Additionally, the values of the stress concentrations in the butt-welded joints were obtained using afinite element method (FEM). The SCFs calculated using the four methods were compared and further discussed. Our data suggested a new accurate and straightforward approach for calculating the SCF by knowing only the weld toe radius.

Notcheffect on J and Amplification of Anisotropic Stress Concentration Factor in a Laminated Plate Subjected to Tensile Load

2015 ◽  
Vol 1105 ◽  
pp. 381-385
Author(s):  
Djamel Ouinas ◽  
Bel Abbès Bachir Bouiadjra ◽  
A. Albedah ◽  
Mohamed Sahnoun
Keyword(s):  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Fibre Orientation ◽  
Notch Root ◽  
Tensile Load ◽  
Homogeneous Material ◽  
Laminated Plate ◽  
Stress Concentrations ◽  
Anisotropic Stress

Several analytical, numerical and experimental techniques are available to study the stress concentration around the notches. The stress distribution in a rectangular composite laminated plate with a central notch was studied using the finite element method. The objective of this study is to analyze the fibre orientation effect on the variation of stress concentrations at the notch root and the J-integral at the crack-tip emanating from this notch in a plate subjected to tensile loading. The results show that the anisotropic stress concentration factor can be higher or lower than that of a homogeneous material. The area of maximum normal and tangential stresses could shift with fibre orientation with respect to the loading axis. The interaction effect between a crack located on the ligament of the plate and the circular notch of radius is considered.The results indicate that fold sequence influences appreciably the acceleration or the retardation of the crack propagation.

scholarly journals Stress concentrations at an oblique hole in a thick plate

2000 ◽  
Vol 35 (2) ◽  
pp. 143-147 ◽  
Author(s):  
P Stanley ◽  
A G Starr
Keyword(s):  
Stress Concentration ◽  
Flat Plate ◽  
Uniaxial Tension ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Thick Plate ◽  
Empirical Equation ◽  
Elastic Stress ◽  
Cylindrical Hole ◽  
Stress Concentrations

An empirical equation has been obtained for the elastic stress concentration factor at an isolated oblique circular-cylindrical hole in a thick flat plate subjected to a uniform, arbitrarily oriented uniaxial tension. The equation is presented and its development is outlined in this note.

Evaluation of the Solutions for Calculating Misalignment-Induced Stress Concentration Factor at Girth Welds in Pipelines

2020 ◽  
Author(s):  
Yan-Hui Zhang ◽  
Matthew Dore ◽  
Jazeel R. Chukkan
Keyword(s):  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Fatigue Crack Initiation ◽  
Axial Loading ◽  
Induced Stress ◽  
Weld Toe ◽  
The Difference ◽  
Stress Concentration Factors ◽  
Girth Welds

Abstract Pipelines are commonly joined by girth welds. A centreline offset at a girth weld would inevitably be introduced due to either a difference in wall thickness of the pipes at each side of the weld or due to misalignment. An additional bending stress can result when the pipeline containing the girth weld is subjected to axial loading. This partly contributes to fatigue crack initiation from the weld toe. Therefore, the misalignment-induced stress concentration factor, Km, must be considered in fatigue design of girth welded pipelines. There are several solutions available to calculate Km including BS 7910, DNVGL-RP-C203 and Connelly and Zettlemoyer. In some cases, the difference in the stress concentration factors calculated using these solutions is significant. This paper reviews these and other solutions and verifies them by finite element results and experimental data obtained through strain gauge measurements. Based on the study, the most appropriate Km solution is recommended.

scholarly journals Evaluation of the Stress Concentration Factor in Butt Welded Joints: A Comparative Study

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 411
Author(s):  
Miroslav Randić ◽  
Duško Pavletić ◽  
Marko Fabić
Keyword(s):  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Welded Joints ◽  
Concentration Factor ◽  
Computer Software ◽  
Base Material ◽  
Geometric Parameters ◽  
Stress Concentrations ◽  
Weld Toe ◽  
Toe Angle

Surface cracks in butt-welded joints usually occur in places with increased stress concentrations. The stress concentration factor (SCF) can be calculated using an empirical equation, with five geometric parameters of a butt-welded joint (thickness of the base material, toe radius, weld toe angle, weld width, and reinforcement height). However, in an industrial environment, it is impractical and sometimes even impossible to measure all five geometric parameters with sufficient accuracy. In this study, eight experiments on butt-welded joints were performed. All samples were scanned with a 3D scanner, and the geometric sizes of the welded joints were measured using computer software. A modified empirical expression proposed by Ushirokawa and Nakayama was used to calculate the SCF; the expression was adjusted in such a way that the SCF was calculated by knowing only the toe radius. In addition, four new expressions were proposed for the calculation of the SCF by knowing the toe radius in relation to the weld toe angle; the expressions were then compared and analyzed. Additionally, the values of the stress concentrations in the butt-welded joints were obtained using a finite element method (FEM). The SCFs calculated using the four methods were compared and further discussed. Our data suggested a new accurate and straightforward approach for calculating the SCF by knowing only the weld toe radius.

Stress Concentrations in Tensile Strips with Central Notches of Varying End Radii

1962 ◽  
Vol 66 (617) ◽  
pp. 323-326 ◽  
Author(s):  
Ralph Papirno
Keyword(s):  
Stress Concentration ◽  
Excellent Agreement ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Elastic Stress ◽  
Finite Width ◽  
Stress Concentrations ◽  
Fixed Length ◽  
Tensile Strip ◽  
Image Position

SummaryUsing relations derived by Dixon and Inglis, the values of the elastic stress concentration factor for a fixed length notch in a finite width tensile strip with a varying notch end radius have been obtained in the form:Photoelastic tests on internally notched tensile strip models showed excellent agreement with the analytical results.

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