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.

Computation of Stress Concentration Factors for Tubular Joints

2013 ◽  
Author(s):  
Philippe Thibaux ◽  
Steven Cooreman
Keyword(s):  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Tubular Joints ◽  
Element Size ◽  
Out Of Plane ◽  
Weld Toe ◽  
Concentration Factors ◽  
Stress Concentration Factors ◽  
Bending Modes

Stress concentration factors for tubular joints were computed using solid quadratic elements. The results of the computations are compared with experiments reported in the literature and with expressions reported in the literature and in design codes. An influence of element size and element type was observed, which leads to recommendations regarding element size of four quadratic elements in thickness, which is finer than in different published recommendations. A parametric study was performed, showing that stress concentration factors from the literature are not always conservative, particularly at the crown toe of the chord, while they tend to be overconservative at the chord saddle. The stress concentration factor for the inside of the member was also computed; it is found that it can be close to the stress concentration factor at the weld toe for both the in plane or out of plane bending modes.

Orthotropy and geometry effects on stress concentration factors for short rectangular plates with a centred circular opening

2007 ◽  
Vol 42 (7) ◽  
pp. 551-555 ◽  
Author(s):  
K Bakhshandeh ◽  
I Rajabi
Keyword(s):  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Finite Width ◽  
Rectangular Plates ◽  
Circular Opening ◽  
Orthotropic Plates ◽  
Plate Length ◽  
Transition Length ◽  
Stress Concentration Factors

In this study, the effects of orthotropy ratio and plate length on the stress concentration factor for orthotropic plates with a centred circular opening under the action of uniaxial tension loads are investigated by use of the finite element method. This work demonstrates that the stress concentration factor depends on the length of the member in addition to other established geometric parameters. The value of the transition length between long and short plates is computed and reported as well. This study has shown that Tan's equation for a finite width orthotropic plate is accurate for a ratio of the opening radius to plate semiwidth of less than 0.35 for orthotropy ratios less than 50. A new concept is introduced, namely the transition ratio.

Numerical Investigation of Stress Concentration Factor at Irregular Corrosion Pit Under Tension-Torsion Loading

2014 ◽  
Author(s):  
Yuhui Huang ◽  
Chengcheng Wang ◽  
Shan-Tung Tu ◽  
Fu-Zhen Xuan ◽  
Takamoto Itoh
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Stress Concentration ◽  
Aspect Ratio ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Three Dimensional ◽  
Element Analysis ◽  
Stress Concentration Factors ◽  
Local Dissolution

Finite element analysis is adopted to study the stress concentration of pit area under tension-torsion loading. The stress concentration factors under regular evolution and irregular evolution of pits are investigated by conducting a series of three-dimensional semi-elliptical pitted models. Based on the finite element analysis, it can be concluded that pit aspect ratio (a/2c) is a significant parameter affecting stress concentration factor (SCF) for regular evolution pits. Pits, having higher aspect ratio, are very dangerous form and can cause significant reduction in the load carrying capacity. When local dissolution occurs in the pitting area, SCF will have a sharp increase, it is more probable for a crack to initiate from these areas compared with pits for regular evolution. Furthermore, local dissolution coefficient is proposed to study effect of local dissolution within the pit on SCF.

Investigation of Critical Stress Concentration Factor in Analytical Stress Based Forming Limit Criterion

2009 ◽  
Author(s):  
Kyle R. McLaughlin ◽  
Tugce Kasikci ◽  
Igor Tsukrov ◽  
Brad L. Kinsey
Keyword(s):  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Failure Criterion ◽  
Concentration Factor ◽  
Critical Stress ◽  
Strain Path ◽  
Path Dependence ◽  
Forming Limit ◽  
Concentration Factors ◽  
Stress Concentration Factors

Tearing concerns in sheet metal forming have traditionally been predicted by comparing the strain state imposed on a material to its associated strain based Forming Limit Diagram. A shortcoming of this strain based failure criterion is that the Forming Limit Curves exhibit strain path dependence. Alternatively, a stress based failure criterion was introduced and shown analytically and numerically to exhibit less strain path dependence. In our past research, an analytical model was created to predict the stress based Forming Limit Curve. Inputs into the model include a material constitutive relationship, anisotropic yield criterion and a critical stress concentration factor, defined as the ratio of the effective stress in the base material to the effective stress in the necking region. This stress concentration factor is thought to be a material parameter, which characterizes a material’s ability to work harden and prevent the concentration of stress which produces the necking condition. In this paper, the critical stress concentration factors for steel and aluminum alloys were determined by comparing analytical model predictions and experimental data and found to be significantly different. A setup is then proposed to experimentally measure the critical stress concentration factors and initial results are presented.

Stress-Concentration Factors at a Doubly-Symmetric Hole

1966 ◽  
Vol 17 (2) ◽  
pp. 177-186 ◽  
Author(s):  
L. H. Mitchell
Keyword(s):  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Infinite Plate ◽  
Concentration Factors ◽  
Stress Concentration Factors

SummaryThe stress-concentration factor is calculated for an infinite plate in tension containing a doubly-symmetrical hole whose boundary consists of parts of three intersecting circles. A suggestion is made for modifying the results to apply to a strip.

Fatigue Behavior of the Low-Strength Steel Welded Joints Treated by TIG Dressing and Ultrasonic Peening Combined Method

2011 ◽  
Vol 295-297 ◽  
pp. 1885-1889
Author(s):  
Sen Li ◽  
Dong Po Wang ◽  
Hai Zhang ◽  
Bo Tan
Keyword(s):  
Fatigue Life ◽  
Fatigue Strength ◽  
Stress Concentration ◽  
Compressive Stress ◽  
Stress Level ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Combined Method ◽  
Ultrasonic Peening ◽  
Weld Toe

Butt-joint specimens of Q235B low-strength steel were treated by TIG dressing and ultrasonic peening combined method. The paper presents comparative fatigue test for welded specimens in the as-welded condition and specimens treated by TIG dressing, ultrasonic peening treatment (UPT) and the combined method. When the ratio of stress R=0.1, contrasted with the specimens in as welded condition, the fatigue strength of the specimens treated by TIG dressing is increased by 36%. The fatigue strength of the specimens treated by the combined method and UPT are almost the same, which are increased by 57% and 56% respectively. In the high stress level, weld toe treated by the combined method has smaller stress concentration factor than that of UPT, resulting in less release of residual compressive stress. So it's more effective to improve the fatigue life by the combined method. While in the low stress level, the residual compressive stress of weld toe treated by the combined method and UPT are nearly the same. Besides, the effect of stress concentration factor is smaller, thus the fatigue life of the two methods have little difference.

The Thermal Fatigue Performance for Cast Iron Brake Drum of Large Trucks

2011 ◽  
Vol 117-119 ◽  
pp. 821-823
Author(s):  
Gao Lu ◽  
Wen Yan Wang ◽  
Jing Pei Xie
Keyword(s):  
Cast Iron ◽  
Stress Concentration ◽  
Crack Initiation ◽  
Thermal Fatigue ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Fatigue Crack Initiation ◽  
High Strength ◽  
Fatigue Properties ◽  
Brake Drum

This paper studies the application in different cast iron brake drum the thermal fatigue properties of materials. The results show that the stress concentration factor of grey cast iron, hot fatigue crack initiation, low intensity, and easy to expand, organization crack initiation poor stability, antioxidant ability is poor, thermal fatigue is poorer. 35% of vermicular cast iron and of ductile iron high strength, toughness, good stress concentration factor small, thermal fatigue is well.

Stress Concentration Factors From Overlapping Stress Fields in Uniaxial Tension

1976 ◽  
Vol 98 (1) ◽  
pp. 332-339 ◽  
Author(s):  
H. T. Gencsoy ◽  
J. F. Hamilton ◽  
C. C. Yang
Keyword(s):  
Stress Concentration ◽  
Uniaxial Tension ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Substantial Effect ◽  
Stress Fields ◽  
Concentration Factors ◽  
Stress Concentration Factors ◽  
Stress Raisers ◽  
Resultant Stress

Standard transmission photoelastic techniques were used to determine the resultant stress concentration factors produced by multiple stress raisers in flat, rectangular bars under uniaxial tension. Observations were made on the overlapping stress fields due to various combinations and orientations of holes and semicircular grooves. Two cases of directly superposed discontinuities were also investigated. The results of this investigation indicate that the sizes and relative positions of the discontinuities had a substantial effect on the resultant stress concentration factor. In some cases the stress concentration factor would be decreased while in other cases it would be increased. In the case of superposed stress raisers considered in this investigation, the resultant stress concentration factor can be taken as the product of the individual stress concentration factors; this is in agreement with the results of other investigators. However, for other cases, much judgment and experience will be required to decide when this can be done. And even then this product should be considered only as the probable upper limit of the actual stress concentration factor.

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