Emerging Technology in Fitness-for-Service Assessment of Crack-Like Flaws

2019 ◽  
Author(s):  
Ted L. Anderson
Keyword(s):  
Stress Intensity ◽  
Element Analysis ◽  
Reference Stress ◽  
Future Edition ◽  
Failure Assessment ◽  
Complex Shapes ◽  
Constraint Effects ◽  
New Equation ◽  
Definition Of ◽  
Flaw Shape

Abstract This paper describes several recent advances in crack assessment technology that have been or will be incorporated into the API 579 fitness-for-service standard. Four technology areas are addressed herein: • Stress intensity factor solutions. The 2016 edition of API 579 contains an extensive library of stress intensity solutions inferred from 3D finite element analysis. • A new equation for fitting elastic-plastic J solutions. A parametric equation that captures the elastic, fully-plastic and contained-yielding regimes of deformation provides an alternative definition of reference stress in the failure assessment diagram (FAD) method. • An enhanced constraint adjustment. A future edition of API 579 will include an improved version of the Wallin methodology for shifting the Master Curve reference temperature to account for constraint effects. • A procedure to account for non-ideal crack profiles. Most crack assessment methods assume an idealized flaw shape such as semi-elliptical, but many real-world flaws have complex shapes.

RSE-M - ASME XI - API 579: Comparison of Failure Assessment Diagrams (FAD)

2018 ◽  
Author(s):  
Claude Faidy
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Elastic Stress ◽  
Short Review ◽  
The Other ◽  
Ductile Tearing ◽  
Reference Stress ◽  
Failure Assessment ◽  
Tearing Resistance ◽  
Applied Stresses

After a short review of the 3 Codes in term of flaw evaluation, this paper will consider the Failure Assessment Diagrams (FAD) proposed in each of them. The cracked components are evaluated by a dedicated diagram for margin evaluation of ductile tearing resistance of the components: the elastic stress intensity factor of the crack normalized by the toughness of the material on one axis and the applied stresses normalized by a Reference Stress in the other axis. The 2017 Edition of RSE-M Appendix 5.4 and 5.6, the 2017 Edition of ASME XI Appendix H and the 2016 Edition of API 579 Part 9 will be used in this first comparison.

Inclusion of Crack Face Pressure in Reference Stress for Thick Walled Risers and Flowlines

2013 ◽  
Author(s):  
Mark Cerkovnik ◽  
Wasy Akhtar
Keyword(s):  
High Pressure ◽  
Element Analysis ◽  
Crack Face ◽  
Aspect Ratios ◽  
Reference Stress ◽  
Industry Standards ◽  
Full Cross Section ◽  
Failure Assessment ◽  
Fracture Assessment ◽  
Linear Material

A methodology is developed to account for the effect of crack face pressure on the reference stress in high pressure, thick walled, flowlines and risers. Risers and flowlines in production service may be exposed to corrosive attack resulting in pitting. In such cases, cracks can initiate and fitness for service assessment, including fatigue crack growth and fracture analysis, is required. For such thick walled lines, the effect of high internal pressure on the crack face is significant and must be taken into account. Current industry standards, including API-RP-579 [1] and BS7910 [2], are silent on the effects of crack face pressure on the reference stress. Reference stress, a quantity similar to the net section stress, can be used to predict the local plastic failure of the remaining ligament ahead of the crack tip, or the collapse of the full cross section. The reference stress is also used in the abscissa on the Failure-Assessment-Diagram (FAD) to determine the allowable stress intensity ratio for fracture assessment. The methodology described in the paper follows from systematic detailed finite element analysis (FEA) conducted using linear material properties. The analysis is conducted over a range of pipe thickness ratios (D/t), crack depths (a/t) and crack aspect ratios (c/a). The results presented permit an accurate calculation of the effect of crack face pressure that can be implemented within the framework of existing methods of fitness for service analysis without the use of FEA. This paper presents a detailed analysis of the effect of crack face pressure on the reference stress for axial and circumferential internal flaws. The results from this study provide expressions to estimate the reference stress with crack face pressure loading, thus, allowing an improved fracture prediction for high pressure risers and flowlines.

scholarly journals Shape Sensing of a Complex Aeronautical Structure with Inverse Finite Element Method

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1388
Author(s):  
Daniele Oboe ◽  
Luca Colombo ◽  
Claudio Sbarufatti ◽  
Marco Giglio
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Boundary Conditions ◽  
Strain Field ◽  
Element Analysis ◽  
Inverse Finite Element Method ◽  
Shape Sensing ◽  
Definition Of ◽  
High Level ◽  
Element Method

The inverse Finite Element Method (iFEM) is receiving more attention for shape sensing due to its independence from the material properties and the external load. However, a proper definition of the model geometry with its boundary conditions is required, together with the acquisition of the structure’s strain field with optimized sensor networks. The iFEM model definition is not trivial in the case of complex structures, in particular, if sensors are not applied on the whole structure allowing just a partial definition of the input strain field. To overcome this issue, this research proposes a simplified iFEM model in which the geometrical complexity is reduced and boundary conditions are tuned with the superimposition of the effects to behave as the real structure. The procedure is assessed for a complex aeronautical structure, where the reference displacement field is first computed in a numerical framework with input strains coming from a direct finite element analysis, confirming the effectiveness of the iFEM based on a simplified geometry. Finally, the model is fed with experimentally acquired strain measurements and the performance of the method is assessed in presence of a high level of uncertainty.

scholarly journals Mechanical Integrity Assessment of Two-Side Etched Type Printed Circuit Heat Exchanger with Additional Elliptical Channel

Energies ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4711
Author(s):  
Armanto P. Simanjuntak ◽  
Jae-Young Lee
Keyword(s):  
Heat Exchanger ◽  
Stress Intensity ◽  
Maximum Stress ◽  
High Stress ◽  
Element Analysis ◽  
Integrity Assessment ◽  
Printed Circuit ◽  
Mechanical Integrity ◽  
Finite Element Analysis Simulation ◽  
Maximum Stress Intensity

Printed circuit heat exchangers (PCHEs) are often subject to high pressure and temperature difference between the hot and cold channels which may cause a mechanical integrity problem. A conventional plate heat exchanger where the channel geometries are semi-circular and etched at one side of the stacked plate is a common design in the market. However, the sharp edge tip channel may cause high stress intensity. Double-faced type PCHE appears with the promising ability to reduce the stress intensity and stress concentration factor. Finite element analysis simulation has been conducted to observe the mechanical integrity of double-etched printed circuit heat exchanger design. The application of an additional ellipse upper channel helps the stress intensity decrease in the proposed PCHE channel. Five different cases were simulated in this study. The simulation shows that the stress intensity was reduced up to 24% with the increase in additional elliptical channel radius. Besides that, the horizontal offset channels configuration was also investigated in this study. Simulation results show that the maximum stress intensity of 2.5 mm offset configuration is 9% lower compared to the maximum stress intensity of 0 mm offset. This work proposed an additional elliptical upper channel with a 2.5 mm offset configuration as an optimum design.

Stress Intensity Factor for Repaired Circumferential Cracks in Pipe With Bonded Composite Wrap

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
F. Benyahia ◽  
A. Albedah ◽  
B. Bachir Bouiadjra
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Fracture Criterion ◽  
Three Dimensional ◽  
Element Analysis ◽  
Composite Systems ◽  
Bonded Composite ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

The use of composite systems as a repair methodology in the pipeline industry has grown in recent years. In this study, the analysis of the behavior of circumferential through cracks in repaired pipe with bonded composite wrap subjected to internal pressure is performed using three-dimensional finite element analysis. The fracture criterion used in the analysis is the stress intensity factor (SIF). The obtained results show that the bonded composite repair reduces significantly the stress intensity factor at the tip of repaired cracks in the steel pipe, which can improve the residual lifespan of the pipe.

Elastic Thermal Stresses in Bimetallic Pipe Welds

1980 ◽  
Vol 102 (4) ◽  
pp. 430-432 ◽  
Author(s):  
R. D. Blevins
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Stress Intensity ◽  
Maximum Stress ◽  
Thermal Stresses ◽  
Simple Expression ◽  
Element Analysis ◽  
Maximum Stress Intensity ◽  
Bimetallic Pipe ◽  
Uniform Change

The elastic thermal stresses in a welded transition between two pipes of the same size but different alloys are explored. A stress-free temperature is postulated and the stress due to a uniform change in temperature is characterized by the maximum stress intensity in the weld. A simple expression for predicting this maximum stress intensity is developed based on the results of finite element analysis.

Mixed Mode Stress Singularities in Anisotropic Composites

1999 ◽  
Author(s):  
Wan-Lee Yin
Keyword(s):  
Stress Intensity ◽  
Asymptotic Solution ◽  
Stress Intensity Factors ◽  
Stress Singularity ◽  
Free Edge ◽  
Complex Conjugate ◽  
Circular Path ◽  
Intensity Factors ◽  
Element Analysis ◽  
Anisotropic Elastic

Abstract Multi-material wedges composed of fully anisotropic elastic sectors generally show intrinsic coupling of the anti-plane and in-plane modes of deformation. Each anisotropic sector has three complex conjugate pairs of material eigensolutions whose form of expression depends on five distinct types of anisotropic materials. Continuity of the displacements and the tractions across the sector interfaces and the traction-free conditions on two exterior boundary edges determine an infinite sequence of eigenvalues and eigensolutions of the multi-material wedge. These eigensolutions are linearly combined to match the traction-boundary data (generated by global finite element analysis of the structure) on a circular path encircling the singularity. The analysis method is applied to a bimaterial wedge near the free edge of a four-layer angle-ply laminate, and to a trimaterial wedge surrounding the tip of an embedded oblique crack in a three-layer composite. Under a uniform temperature load, the elasticity solution based on the eigenseries yields interfacial stresses that are significantly different from the asymptotic solution (given by the first term of the eigenseries), even as the distance from the singularity decreases to subatomic scales. Similar observations have been found previously for isotropic and orthotropic multi-material wedges. This raises serious questions with regard to characterizing the criticality of stress singularity exclusively in terms of the asymptotic solution and the associated stress intensity factors or generalized stress intensity factors.

Sign in / Sign up

Export Citation Format

Share Document