scholarly journals A Study on The Effect Of Defect Location On Stress In Bending Pipe

2021 ◽  
Vol 12 (6) ◽  
pp. 802-806
Author(s):  
Jin-Bong KIM
Keyword(s):  
Boundary Condition ◽  
Stress Concentration ◽  
Plastic Zone ◽  
Boundary Conditions ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Stress Difference ◽  
Secondary Root ◽  
Defect Location ◽  
Minimum Value

In this study, the stress that generated when the first or second root of a corrugated pipe is defective is analyzed. The model is analyzed using F.E.M. code. The boundary conditions of deflection or torsion on the opposite side of the defect in the corrugated pipe are changed. The effect of the defect is evaluated using the change of the stress magnitude and the stress concentration factor(K) according to those conditions. As a result of comparing the stress magnitude, K around the flaw at the secondary root is larger than K around the flaw at the first root. Based on the position of the defect, the stress difference in the 1st root increases depending on the boundary condition of bending deflection. However, when the 2nd root is defective, the stress magnitude is similar in both cases regardless of the bending deflection. The magnitude of the stress generated in the corrugated pipe is the highest when the second root is defective. And the stress magnitude is the lowest when there is no defect. In the absence of defects, the stress gradually increases after the stress reaches the minimum value as the amount of deformation increases. However, if there is a defect, stress continues to increase, and when it passes through the plastic zone, the stress gradually increases.

A numerical approach to determine fiber orientations around geometric discontinuities in designing against failure of GFRP laminates

2019 ◽  
Vol 10 (3) ◽  
pp. 371-379 ◽  
Author(s):  
Roselita Fragoudakis
Keyword(s):  
Stress Concentration ◽  
Plastic Zone ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Load Condition ◽  
Content Type ◽  
Geometric Discontinuities ◽  
Failure Theories ◽  
Laminated Structures ◽  
Minimum Moment

Purpose Determining fiber orientations around geometric discontinuities is challenging and simultaneously crucial when designing laminates against failure. The purpose of this paper is to present an approach for selecting the fiber orientations in the vicinity of a geometric discontinuity; more specifically round holes with edge cracks. Maximum stresses in the discontinuity region are calculated using Classical Lamination Theory (CLT) and the stress concentration factor for the aforementioned condition. The minimum moment to cause failure in a lamina is estimated using the Tsai–Hill and Tsai–Wu failure theories for a symmetric general stacking laminate. Fiber orientations around the discontinuity are obtained using the Tsai–Hill failure theory. Design/methodology/approach The current research focuses on a general stacking sequence laminate under three-point bending conditions. The laminate material is S2 fiber glass/epoxy. The concepts of mode I stress intensity factor and plastic zone radius are applied to decide the radius of the plastic zone, and stress concentration factor that multiplies the CLT stress distribution in the vicinity of the discontinuity. The magnitude of the minimum moment to cause failure in each ply is then estimated using the Tsai–Hill and Tsai–Wu failure theories, under the aforementioned stress concentration. Findings The findings of the study are as follows: it confirms the conclusions of previous research that the size and shape of the discontinuity have a significant effect on determining such orientations; the dimensions of the laminate and laminae not only affect the CLT results, but also the effect of the discontinuity in these results; and each lamina depending on its position in the laminate will have a different minimum load to cause failure and consequently, a different fiber orientation around the geometric discontinuity. Originality/value This paper discusses an important topic for the manufacturing and design against failure of Glass Fiber Reinforced Plastic (GFRP) laminated structures. The topic of introducing geometric discontinuities in unidirectional GFRP laminates is still a challenging one. This paper addresses these issues under 3pt bending conditions, a load condition rarely approached in literature. Therefore, it presents a fairly simple approach to strengthen geometric discontinuity regions without discontinuing fibers.

The Interaction of Holes on Stress and Strain Concentrations in Uniaxially Loaded Tensile Plates

2012 ◽  
Vol 268-270 ◽  
pp. 767-771
Author(s):  
Zheng Yang
Keyword(s):  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Thickness Effect ◽  
Central Hole ◽  
Stress And Strain ◽  
Strain Concentration ◽  
Minimum Value ◽  
R Ratio ◽  
Stress Concentration Region

Abstract. The elastic stress and strain fields of plates containing one central hole and two auxiliary holes subjected to uniaxial tension are examined using finite element method. The interaction between holes and the thickness effect on stress and strain concentration factors are investigated. It is shown that the distributions of strain concentration factor and stress concentration factor are different near central hole and auxiliary hole, and both of them depend on the hole radii and the distance between central hole and auxiliary hole. There is a minimum value of Kε/Kσ in stress concentration region and the quantity and location of this minimum value in plane stress state depend on the r/R ratio and d/R ratio of the plate. There are some specific distances between central hole and auxiliary hole corresponding to the radii of auxiliary hole to make the stress concentration factor in the plate minimum.

Transition Method of Geometrically Similar Element to Calculate the Stress Concentration Factor of Notch

2007 ◽  
Vol 561-565 ◽  
pp. 2205-2208
Author(s):  
You Tang Li ◽  
Zhi Yuan Rui ◽  
Chang Feng Yan
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Stress Concentration ◽  
Intensity Factor ◽  
Boundary Conditions ◽  
High Precision ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Structural Dimension ◽  
Similar Element

There are close relations between stress concentration factor of notch and stress intensity factor of crack when the boundary conditions and geometrical conditions are in the same. The transition method of geometrically similar element to calculate the stress concentration factor of notch is proposed and some examples are computed by this method. There are some advantages for this method such as no limit of structural dimension, good adaptability, high precision and use convenience.

scholarly journals A novel thread connection structure of slimehole drilling tool in ultra-deep natural gas well

2021 ◽  
Vol 104 (2) ◽  
pp. 003685042110264
Author(s):  
Zhang Ying ◽  
Lian Zhanghua ◽  
Gao Anqi ◽  
Yang Kun
Keyword(s):  
Fatigue Life ◽  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Sensitivity Coefficient ◽  
Notch Sensitivity ◽  
Sensitivity Factor ◽  
Drilling Tool ◽  
Gas Well ◽  
Thread Connection

The thread connection’s root fillet radius of 0.038″ size is the greatest weakness of the API NC type joints and thread. During the slimehole drilling, especially in the deep and ultra-deep gas well, its stress concentration factor and notch sensitivity factor are very high A novel thread connection design (TM) of a drilling tool is proposed to decrease the fatigue failure of the slimehole drilling tool in the deep and the ultra-deep gas well in the Tarim oilfield China. The novelty in the TM thread structure is, reducing the threads per inch, extending the distance from the last engaged thread to the external shoulder of the pin and adding three threads to the conventional connection. The novel thread connection will improve the slimehole drilling tool’s anti-fatigue life due to its improved elasticity and rigidity. Furthermore, the TM can transfer the maximum stress at the connection root to the loaded surface, which can effectively lower the fatigue notch’s sensitivity coefficient. In this paper, the finite element method (FEM) is applied to carry out the detailed comparative analysis of the TM with existing thread connection NC38, TX60 and TH90. The TM has the lowest stress concentration factor and fatigue notch sensitivity coefficient, so its anti-fatigue life is the highest. In addition, TM is manufactured and is tested at Tarim oilfield in China.

Stress Concentration of Periodic Collinear Square Holes in an Infinite Plate in Tension

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Changqing Miao ◽  
Yintao Wei ◽  
Xiangqiao Yan
Keyword(s):  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Infinite Plate ◽  
Numerical Approach ◽  
Numerical Examples ◽  
Calculated Stress ◽  
Bueckner’S Principle

A numerical approach for the stress concentration of periodic collinear holes in an infinite plate in tension is presented. It involves the fictitious stress method and a generalization of Bueckner's principle. Numerical examples are concluded to show that the numerical approach is very efficient and accurate for analyzing the stress concentration of periodic collinear holes in an infinite plate in tension. The stress concentration of periodic collinear square holes in an infinite plate in tension is studied in detail by using the numerical approach. The calculated stress concentration factor is proven to be accurate.

Fracture of Inoculated Iron Under Biaxial Stresses

1955 ◽  
Vol 22 (2) ◽  
pp. 172-174
Author(s):  
I. Cornet ◽  
R. C. Grassi
Keyword(s):  
Cast Iron ◽  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Gray Cast Iron ◽  
Energy Criterion ◽  
Gray Cast ◽  
Published Data ◽  
Thin Wall ◽  
As Stress

Abstract Data are presented on the fracture of inoculated-iron thin-wall tubes, investigated under various ratios of axial to tangential stress, ranging from pure tension to pure compression. These data are consistent with published data on gray cast iron. It may be assumed that in cast-iron, plates of friable graphite in an iron matrix, act like solid iron with respect to compressive stresses, but they act as stress-concentrating cavities with respect to tensile stresses. This gives a stress-concentration factor, which is easily determined experimentally. Stress-concentration factors obtained were 3.2–3.3 for gray cast iron, and 2.4–2.5 for inoculated cast iron. A distortion-energy criterion for fracture, modified by this stress-concentration factor, is consistent with the experimental data. It appears that the concentration of the dispersed graphite, and the shape and size of this brittle phase, affect the fracture strength under combined stresses.

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