Constraint Parameter for a Longitudinal Surface Notch in a Pipe Submitted to Internal Pressure

2008 ◽  
Vol 399 ◽  
pp. 3-11 ◽  
Author(s):  
Mohammed Hadj Meliani ◽  
M. Benarous ◽  
Z. Azari ◽  
G. Pluvinage
Keyword(s):  
Stress Distribution ◽  
Fracture Mechanics ◽  
Internal Pressure ◽  
Loading Conditions ◽  
Notch Stress ◽  
T Stress ◽  
Surface Notch ◽  
Pipe Geometry ◽  
Two Parameters ◽  
Method Approach

The use of two parameters fracture mechanics criterion as a tool for structural design and analysis has increased significantly in recent years. First, we discuse the elastic solution for the stress distribution at crack tip for two dimensional geometries and particularly constraint as T-stress under various loading conditions. Secondly, using notch fracture mechanics and particularly the Volumetric Method approach, we study the stress distribution at the tip of a notch in pipes submitted to internal pressure. The Notch Stress Intensity Factor Kρ and the effective T-stress are combined into a two-parameter fracture criterion (KIρ-Tef). This approach is then used to quantify the constraint of notch-tip fields for various pipe geometry and loading conditions.

scholarly journals An Extended Finite Element Method (XFEM) Study on the Elastic T-Stress Evaluations for a Notch in a Pipe Steel Exposed to Internal Pressure

Mathematics ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 507
Author(s):  
K. Yakoubi ◽  
S. Montassir ◽  
Hassane Moustabchir ◽  
A. Elkhalfi ◽  
Catalin Iulian Pruncu ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Internal Pressure ◽  
Extended Finite Element Method ◽  
Research Study ◽  
Extended Finite Element ◽  
T Stress ◽  
Cracked Structures ◽  
Element Method

The work investigates the importance of the K-T approach in the modelling of pressure cracked structures. T-stress is the constant in the second term of the Williams expression; it is often negligible, but recent literature has shown that there are cases where T-stress plays the role of opening the crack, also T-stress improves elastic modeling at the point of crack. In this research study, the most important effects of the T-stress are collected and analyzed. A numerical analysis was carried out by the extended finite element method (X-FEM) to analyze T-stress in an arc with external notch under internal pressure. The different stress method (SDM) is employed to calculate T-stress. Moreover, the influence of the geometry of the notch on the biaxiality is also examined. The biaxiality gave us a view on the initiation of the crack. The results are extended with a comparison to previous literature to validate the promising investigations.

Using the Multi-Parameter Fracture Mechanics for more Accurate Description of Stress/Displacement Crack Tip Fields

2013 ◽  
Vol 586 ◽  
pp. 237-240 ◽  
Author(s):  
Lucie Šestáková
Keyword(s):  
Stress Distribution ◽  
Fracture Mechanics ◽  
Boundary Conditions ◽  
Displacement Field ◽  
Singular Term ◽  
Crack Tip ◽  
Higher Order ◽  
Precise Description ◽  
Accurate Knowledge ◽  
Higher Order Terms

Most of fracture analyses often require an accurate knowledge of the stress/displacement field over the investigated body. However, this can be sometimes problematic when only one (singular) term of the Williams expansion is considered. Therefore, also other terms should be taken into account. Such an approach, referred to as multi-parameter fracture mechanics is used and investigated in this paper. Its importance for short/long cracks and the influence of different boundary conditions are studied. It has been found out that higher-order terms of the Williams expansion can contribute to more precise description of the stress distribution near the crack tip especially for long cracks. Unfortunately, the dependences obtained from the analyses presented are not unambiguous and it cannot be strictly derived how many of the higher-order terms are sufficient.

scholarly journals The theory of combined plastic and elastic deformation with particular reference to a thick tube under internal pressure

1947 ◽  
Vol 191 (1026) ◽  
pp. 278-303 ◽  
Keyword(s):  
Stress Distribution ◽  
Internal Pressure ◽  
Plastic Flow ◽  
Plastic Region ◽  
Strain Diagram ◽  
Combined Stresses ◽  
Usual Theory ◽  
Plastic Components ◽  
Longitudinal Extension ◽  
Elastic Strains

In certain problems of plastic flow, for example, a thick tube expanded by internal pressure, it is important to consider changes in the elastic strain of material which is flowing plastically in order to deduce the correct stress distribution and deformation. The usual plastic theory which neglects elastic strains in the plastic region may lead to considerable errors in certain cases. In this paper we review the theory of the deformation of a material under combined stresses which involves both elastic and plastic components of strain. The relationship between stress and strain is represented on a plane diagram, the reduced stress-strain diagram, which facilitates discrimination between the elastic and plastic components of strain and aids considerably the solution of certain problems. The diagram can also be used to express the relationships governing the dissipation of energy during plastic flow under combined stresses. The theory is applied to the deformation of a long thick tube under internal pressure with zero longitudinal extension. The solution is compared with that based on the usual theory which neglects elastic strains in the plastic region, revealing an error which reaches a maxi­mum of over 60% in the longitudinal stress distribution. The significance of the differences between the two solutions is discussed in detail.

Influence of Inner Surface Defects on the Fatigue Strength of Pipe Subjected to Cyclic Internal Pressure

1978 ◽  
Vol 100 (4) ◽  
pp. 360-368
Author(s):  
Y. Yazaki ◽  
S. Hashirizaki ◽  
S. Nishida ◽  
C. Urashima
Keyword(s):  
Fatigue Strength ◽  
Internal Pressure ◽  
Test Specimen ◽  
Surface Defects ◽  
Fatigue Crack Initiation ◽  
Internal Surface ◽  
Fatigue Tests ◽  
Inner Surface ◽  
Surface Notch ◽  
Medium Diameter

Cyclic internal oil pressure fatigue tests were carried out on medium-diameter ERW pipes of API 5LX - X60 in an attempt to determine the influence of surface defects on the fatigue strength. Experimental factors investigated were the depth and location of internal surface notch in relation to the axis of pipe. The specimen was subjected to cyclic internal pressure, the cyclic rate being 0.3–0.5 Hz. During the test, Acoustic Emission (AE) techniques were applied to detect the fatigue crack initiation. Along with the aforementioned fatigue tests, pulsating tension fatigue tests were carried out on specimens with the same surface notches as the cyclic internal pressure fatigue test specimen.

An Analysis of Pipe Flange Connections Using Epoxy Adhesives/Anaerobic Sealant Instead of Gaskets

1995 ◽  
Vol 117 (4) ◽  
pp. 298-304 ◽  
Author(s):  
T. Sawa ◽  
R. Sasaki ◽  
M. Yoneno
Keyword(s):  
Stress Distribution ◽  
Internal Pressure ◽  
Theory Of Elasticity ◽  
Experimental Results ◽  
Clamping Force ◽  
Bonding Force ◽  
Epoxy Adhesives ◽  
Analytical Results ◽  
Sealing Performance ◽  
Circle Diameter

This paper deals with the strength and the sealing performance of pipe flange connections combining the bonding force of adhesives with the clamping force of bolts. The epoxy adhesives or anaerobic sealants are bonded at the interface partially instead of gaskets in pipe flange connections. The stress distribution in the epoxy adhesives (anaerobic sealant), which governs the sealing performance, and the variations in axial bolt force are analyzed, using an axisymmetrical theory of elasticity, when an internal pressure is applied to a connection in which two pipe flanges are clamped together by bolts and nuts with an initial clamping force after being joined by epoxy adhesives or anaerobic sealant. In addition, a method for estimating the strength of the combination connection is demonstrated. Experiments are performed and the analytical results are consistent with the experimental results concerning the variation in axial bolt force and the strength of combination connections. It can be seen that the strength of connections increases with a decrease in the bolt pitch circle diameter. Furthermore, it is seen that the sealing performance of such combination connections in which the interface is bonded partially is improved over that of pipe flange connections with metallic gaskets.

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