scholarly journals Admissibility of External Cracks in a Pipeline API X60 Using the SINTAP Procedure

2017 ◽  
Vol 61 (4) ◽  
pp. 261
Author(s):  
Kaddour Bahram ◽  
Benattou Bouchouicha ◽  
Mohamed Benguediab ◽  
Abdelkader Slimane
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Modeling And Simulation ◽  
Safety Factors ◽  
Diagram Method ◽  
Failure Assessment Diagram ◽  
Failure Assessment ◽  
Abaqus Software

In this paper we tried to apply the failure assessment diagram method on an API X60 pipeline under two pressures 70 and 90 bar, this work will be divided into two parts; the first part will be devoted to modeling and simulation of a pipeline under pressure 70/90 bar. With abaqus software to determine the stress intensity factor of several ratios, The second part will focus on the exploitation of these results in order to draw the diagram of evaluation of the failure (FAD), once finished, We can pronounce on the vulnerability of the cracks which can cause the ruin of the pipeline to study, on mode of ruin and proposed safety factors.

Comparison Between API 579-1/ASME FFS-1 and ASME VIII Division 3 Stress Intensity Factor Solutions Used for Fracture Mechanics and Fatigue Analysis of Thick Walled Cylinders

2008 ◽  
Author(s):  
Jan G. M. Keltjens
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Life Time ◽  
Time Study ◽  
Worked Example ◽  
Failure Assessment ◽  
Section Viii ◽  
Burst Analysis

The paper discusses the differences between API 579-1/ASME FFS-1-1/ASME FFS-1 [1] and ASME Section VIII Division 3 [2] stress intensity factor solutions. In addition to this, the use of the Failure Assessment Diagram (FAD) in leak before burst analysis is compared to the present Division 3 approach. The paper contains the background of both approaches and a worked example demonstrating the effect of both methods. Finally, a simplified fatigue crack growth based life time study is presented.

scholarly journals Numerical Simulation of the Influence of Width of a Prefabricated Crack on the Dimensionless Stress Intensity Factor of Notched Semi-Circular Bend Specimens

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Sheng Zhang ◽  
Longfei Wang ◽  
Mingzhong Gao
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Width ◽  
Linear Increase ◽  
Maximum Relative Error ◽  
Dimensionless Stress ◽  
Relative Errors ◽  
New Formula ◽  
Abaqus Software

To analyze the effect of the width of a prefabricated crack on the dimensionless stress intensity factor of notched semi-circular bend (NSCB) specimens, ABAQUS software was employed to perform numerical calibration of the crack tip stress intensity factor for the width of prefabricated cracks in the range of 0.0∼2.0 mm. The relative errors of the dimensionless stress intensity factor for different widths of prefabricated cracks were analyzed. The results indicate that the dimensionless stress intensity factor shows an approximate linear increase as the width of the prefabricated crack increases. The longer is the length of the prefabricated crack, the “faster” is the increase in speed. The effect of the dimensionless support spacing on the increase in the speed of the dimensionless stress intensity factor due to the increase in crack width is minimal. When the prefabricated crack width is 2.0 mm, the maximum relative error of the dimensionless stress intensity factor is 4.325%. The new formula for the dimensionless stress intensity factor that eliminates the influence of the width of a prefabricated crack is given, which provides a theoretical basis for the more accurate fracture toughness value measured using an NSCB specimen.

Calculation of KJ Under Secondary Loads in Isolation for R6

2015 ◽  
Author(s):  
Peter James
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Intensity Factors ◽  
Secondary Stress ◽  
Secondary Load ◽  
Failure Assessment ◽  
Different Levels

A range of methods are currently available within R6 to calculate the inelastic secondary stress intensity factor under secondary loads in isolation, KJS. Each of these methods has different levels of associated conservatism depending on assumptions made, the complexity of the approach and the ability to account for different levels of elastic follow-up. Approaches that include an elastic follow-up factor, Z, for treating the interaction of combined primary and secondary stresses have recently been investigated by Ainsworth and James. However, the maturity of this recent work under combined primary and secondary loading means that one of the most significant aspect of the conservatisms in calculating the combined elastic-plastic stress intensity factor, KJ, is now in the calculation of KJS. This work considers existing approaches in R6 to calculate KJS and proposes a further approach allowing the value of Z to be altered. For comparison this work considers finite element analyses of a circumferentially cracked cylinder with four thermal distributions and two shallow cracks. These conditions were controlled to manipulate the level of Z. The magnitude of the temperature difference in these profiles has been increased over the analysis time to provide a relationship between the elastic and inelastic secondary stress intensity factors, KIS and KJS, with increasing secondary load to demonstrate any enhancement and subsequent redistribution of the secondary stress. These finite element estimates have been compared to existing methods in R6 to calculate KJS/KIS which reinforce the available advice in R6 for each case. The proposed approach also compares favourably with the finite element results through modification of Z. The proposed approach is also seen to be compatible with the other approaches within R6 as it has been shown to reproduce the Option 2 failure assessment curve for cases where the elastic follow-up is significant (i.e. Z ≫ 5) and conforms to the displacement controlled estimate of KJS in Section III.14.5 of R6.

Research on the Stress Intensity Factor of the Cracks in the Spherical Shell

2015 ◽  
Vol 757 ◽  
pp. 25-28
Author(s):  
Fei Chen ◽  
Ying Juan Yue ◽  
Cui Ping Zhang ◽  
Hai Xia Du
Keyword(s):  
Finite Element Method ◽  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Spherical Shell ◽  
Vessel Wall ◽  
Three Dimensional ◽  
Surface Cracks ◽  
Abaqus Software

Three models including scheme A, B and C of the semicircular or crescent surface cracks, and two ones including scheme D and E of elliptical inner cracks in the vessel wall in three-dimensional are estabished with ABAQUS software. The values of the crack tip of the stress intensity factor are calculated and compared with the empirical results based on BS 7910 standard. The results show that scheme C and D are better, which provide a new method for the modeling and simulation of three-dimensional components containing cracks with finite element method.

On the Assessment of Through-Wall Circumferential Cracks in Steam Generator Tubes With Tube Supports

2003 ◽  
Vol 125 (1) ◽  
pp. 85-90 ◽  
Author(s):  
Xin Wang ◽  
Wolf Reinhardt
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Steam Generator ◽  
Limit Load ◽  
Life Extension ◽  
Steam Generators ◽  
Failure Assessment ◽  
Circumferential Defects ◽  
Steam Generator Tubes

The assessment of steam generator tubes with defects is of great importance for the life extension of steam generators. Circumferential through-wall cracks are the most severe of all tube circumferential defects, and usually require plugging of the affected tubes. The assessment of the tubes with through-wall circumferential cracks or cracks projected to become through-wall can be conducted using the failure assessment diagram (FAD) approach. This approach requires the calculation of the stress intensity factor and the limit load. The available stress intensity factor and limit load solutions for cracked tubes do not include the constraining effect of the tube supports. In the present paper, it is shown that this can be overly conservative. Solutions for stress intensity factors and limit loads are presented for tubes with circumferential through-wall cracks including the effect from the tube support plates. Different values of support spacing are considered. Based on these solutions, the assessment of a typical steam generator tube is demonstrated.

Development of Pipeline Sleeve End Fillet Weld Stress Intensity Factor and Reference Stress Solutions for Fatigue and Failure Assessment

2016 ◽  
Author(s):  
Vlad Semiga ◽  
Aaron Dinovitzer ◽  
Amin Eshraghi ◽  
Robert Lazor
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Finite Length ◽  
Primary Objective ◽  
National Standards ◽  
Fillet Welds ◽  
Fillet Weld ◽  
Wide Range ◽  
Failure Assessment

Pipeline defects such as cracks, dents and corrosion often require permanent pressure retaining repairs. Full encirclement metallic repair sleeves with fillet-welded end connections to the pipeline are often used for this purpose. In-service failures have occurred at pressure retaining sleeves as a result of defects associated with the sleeve welds, such as hydrogen-induced cracks, undercut at the fillet welds and inadequate weld size. At present, accurate quantitative fitness for service assessments for circumferential defects in a sleeve fillet welds are difficult to carry out due to a lack of detailed stress intensity factor (SIF) solutions for finite length cracks. The primary objective of the project presented in this paper [1] was to develop flaw acceptance criteria which will fill gaps in the available Engineering Critical Assessment procedures for metallic sleeve repairs on all grades of pipelines. SIF solutions for finite length sleeve-end fillet weld toe and root cracks were generated and used to develop parametric equations suitable for carrying out defect assessments. These equations can be used in the assessment of fatigue crack growth and/or fracture using failure assessment diagram (FAD) methods at sleeve end fillets alongside the results developed for other structural geometries in national standards. The equations were developed based on detailed finite element (FE) analyses of a wide range of sleeve end fillet weld cracking scenarios to estimate the SIFs at both the deepest point and the surface breaking point along the crack front.

Damage accumulation near a hole under low cycle fatigue proceeding from measurements of local deformation response

2020 ◽  
Vol 86 (10) ◽  
pp. 46-55
Author(s):  
S. I. Eleonsky ◽  
Yu. G. Matvienko ◽  
V. S. Pisarev ◽  
A. V. Chernov
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Damage Accumulation ◽  
Stress Ratio ◽  
Low Cycle Fatigue ◽  
Accumulation Process ◽  
Stress Range ◽  
Cycle Fatigue ◽  
Deformation Response

A new destructive method for quantitative determination of the damage accumulation in the vicinity of a stress concentrator has been proposed and verified. Increase of damage degree in local area with a high level of the strain gradient was achieved through preliminary low-cycle pull-push loading of plane specimens with central open holes. The above procedure is performed for three programs at the same stress range (333.3 MPa) and different stress ratio values 0.33, – 0.66 and – 1.0, and vice versa for two programs at the same stress ratio – 0.33 and different stress range 333.3 and 233.3 MPa. This process offers a set of the objects to be considered with different degree of accumulated fatigue damages. The key point of the developed approach consists in the fact that plane specimens with open holes are tested under real operation conditions without a preliminary notching of the specimen initiating the fatigue crack growth. The measured parameters necessary for a quantitative description of the damage accumulation process were obtained by removing the local volume of the material in the form of a sequence of narrow notches at a constant level of external tensile stress. External load can be considered an amplifier enhancing a useful signal responsible for revealing the material damage. The notch is intended for assessing the level of fatigue damage, just as probe holes are used to release residual stress energy in the hole drilling method. Measurements of the deformation response caused by local removing of the material are carried out by electronic speckle-pattern interferometry at different stages of low-cycle fatigue. The transition from measured in-plane displacements to the values of the stress intensity factor (SIF) and the T-stress was carried out on the basis of the relations of linear fracture mechanics. It was shown that the normalized dependences of the stress intensity factor on the durability percentage for the first notch (constructed for four programs of cyclic loading with different parameters), reflect the effect of the stress ratio and stress range of the loading cycle on the rate of damage accumulation. The data were used to obtain the explicit form of the damage accumulation function that quantitatively describes damage accumulation process. The functions were constructed for different stress ratios and stress ranges.

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