Reliability Calculation of Welded Pressure Pipe with Circumferential Crack Based on 3-D Elastic-Plastic SFEM

2008 ◽  
Vol 575-578 ◽  
pp. 639-642
Author(s):  
Bo Lin He ◽  
Ying Xia Yu ◽  
Li Xing Huo ◽  
Yu Feng Zhang
Keyword(s):  
Surface Crack ◽  
Safety Assessment ◽  
Crack Depth ◽  
Three Dimensional ◽  
Bending Moment ◽  
Mean Value ◽  
Pressure Pipe ◽  
Circumferential Crack ◽  
The Mean ◽  
Welded Pipe

In this paper, the reliability of welded pressure pipe with circumferential surface crack was calculated by using three dimensional stochastic finite element method. This method has overcome the shortcomings of conservative results in safety assessment with deterministic fracture mechanics method. The calculation of reliability was based on three dimensional elastic-plastic stochastic finite element program which was developed by ourselves. The effects of variables such as fracture toughness, bending moment and the depth of the circumferential surface crack on the structure reliability were also discussed. The calculation results indicate that the crack depth has great effect on the reliability of the welded pipe. When the mean value of the crack depth is changed from 3mm to 7mm, the failure probability of the welded pipe will change from 10-8 to 10-2. The bending moment also has great effect on the reliability of the welded pipe. When the mean value of moment is changed from10000 N.m to 15000 N.m, the failure probability of the welded pipe increases dramatically for the same circumferential crack depth. Irrespective of the changing of moment, the pipe has higher reliability if the crack depth is less than 5mm(a/t<0.5, t is the thickness of the pipe). The method has put forward a new way for safety assessment of welded pipe with circumferential surface crack.

Effects of External Loads on the Reliability of A131 Welded Pipe with Circumferential Crack

2011 ◽  
Vol 704-705 ◽  
pp. 664-667 ◽  
Author(s):  
Bo Lin He ◽  
Ying Xia Yu ◽  
Li Xing Huo ◽  
Yu Feng Zhang
Keyword(s):  
Finite Element ◽  
Failure Probability ◽  
Surface Crack ◽  
Safety Assessment ◽  
Three Dimensional ◽  
Mean Value ◽  
Stochastic Finite Element ◽  
Circumferential Crack ◽  
The Mean ◽  
Welded Pipe

In this paper, the reliability of welded pressure pipe with circumferential surface crack was calculated by using three dimensional stochastic finite element method for A131 pipe steel. This method has overcome the shortcomings of conservative results in safety assessment with deterministic fracture mechanics method. The calculation of reliability was based on three dimensional elastic-plastic stochastic finite element programs which were developed by ourselves. The calculation results indicate that the external load has great effect on the reliability of the welded pipe. When the mean value of bending moment changes from 10000N.m to 20000N.m, the failure probability of the welded pipe will change from 3.3750×10-9 to 1.6794×10-1. When the mean value of moment is changed from10000N.m to 20000N.m, the failure probability of the welded pipe increases dramatically for the same circumferential crack opening angle, inner pressure and the crack depth. The method has put forward a new way for safety assessment of welded pipe with circumferential surface crack.

Effects of External Loads on the Reliability of Welded Pipe with Circumferential Crack

2007 ◽  
Vol 353-358 ◽  
pp. 2513-2516
Author(s):  
Bo Lin He ◽  
Ying Xia Yu ◽  
Li Xing Huo ◽  
Yu Feng Zhang
Keyword(s):  
Finite Element ◽  
Failure Probability ◽  
Surface Crack ◽  
Safety Assessment ◽  
Bending Moment ◽  
Mean Value ◽  
Stochastic Finite Element ◽  
Inner Pressure ◽  
The Mean ◽  
Welded Pipe

The reliability of welded pressure pipe with circumferential surface crack was calculated by using 3-D stochastic finite element method. This method has overcome the shortcomings of conservative results in safety assessment with deterministic fracture mechanics method. The calculation of reliability was based on 3-D elastic-plastic stochastic finite element program which was developed by ourselves. The effects of variables such as bending moment, the inner pressure on the structure reliability were discussed. The calculation results indicate that the bending moment has great effect on the reliability of the welded pipe, and the inner pressure has little effect on the reliability of the welded pipe if the inner pressure is less than 10MPa. If the mean value of the inner pressure changed from 0.5MPa to 30MPa, the failure probability will changes from 10-6 to 10-2. The bending moment also has great effect on the reliability. When the mean value of moment is changed from10000 Nm to 15000 Nm, the failure probability of the welded pipe increases dramatically for the same inner pressure. Irrespective of the changing of moment, the pipe has higher reliability if the inner pressure is less than 6 MPa. The method has put forward a new way for safety assessment of welded pipe with circumferential surface crack.

On the Interaction of Non-Coplanar Embedded Crack With Surface Crack in 3D Using FE and Multi-Level Sub-Structuring

2002 ◽  
Author(s):  
Walied A. Moussa
Keyword(s):  
Surface Crack ◽  
Crack Depth ◽  
Plate Thickness ◽  
Three Dimensional ◽  
Infinite Plate ◽  
Separation Distance ◽  
Multiple Cracks ◽  
Element Analysis ◽  
Weld Toe ◽  
Embedded Crack

The interaction and coalescence of multiple cracks may significantly affect the designed lives of aging pressure vessel structures. Knowledge of the growth behavior of interacting cracks is still limited. In this paper, a novel sub-modeling meshing algorithm is used in three-dimensional linear finite element analysis to investigate the interaction between two identical, non-coplanar, semi-elliptical cracks. One of these cracks is modeled as a surface crack while the other is modeled as an embedded crack under a weld toe. Both interacting cracks are assumed to be in an infinite plate subjected to a remote tension loading condition. The energy release rates (G) and the Stress Intensity Factors (SIF’s) for these cracks are calculated along the interacting crack-front. And, a parametric study involving the variation of the relative horizontal separation distance between the two interacting cracks is carried out for a specific crack depth to plate thickness ratio, a/t, of 0.2. The crack shape aspect ratio, a/c, is also varied in this study within a range that extend between 1.0 and 0.33. An empirical formula is derived that relates the effects of the relative positions of these cracks to their SIFs.

Role of Constraint in Specimen Geometries When Evaluating Fracture Toughness/Material Fracture Resistance for a Surface-Flawed Elbow

2019 ◽  
Author(s):  
S. Kalyanam ◽  
G. Wilkowski ◽  
F. W. Brust ◽  
Y. Hioe ◽  
E. Punch
Keyword(s):  
Surface Crack ◽  
State Of The Art ◽  
Crack Depth ◽  
Bending Moment ◽  
Compact Tension ◽  
Fe Analysis ◽  
Significant Finding ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Variable Surface

Abstract The fracture behavior of a circumferential surface crack in an elbow was evaluated using past data from the International Piping Integrity Research Group (IPIRG-2) Experiment 2-4. The elbow tested was nominal 16-inch diameter Schedule 100 TP304 material, which was solution-annealed after final fabrication. The elbow was loaded with an in-plane-closing bending moment and internal pressure of 15.51 MPa (2,250 psig) at 288 C (550 F). The surface crack was 180-degrees on the ID surface and centered on the extrados, but after fatigue precracking the depth was variable and the greatest was at about 45-degrees from the extrados. FE analysis of the IPIRG-2 elbow test was conducted with a state-of-the-art and precise 3D FE mesh (including variable surface crack depth, variable thickness, and initial elbow ovalization). The flaw depth for the single-edge notch tension (SENT) tests was selected to be equivalent to the deepest point in the elbow specimen crack front that provided the largest J-value in the elbow experiment, i.e., ao/W = 0.68. Comparison of the J-value for initiation (Ji) and crack-tip-opening displacement (CTODi) at crack initiation suggested that there was a slight difference in constraint between an identical depth SENT specimen (a/W = 0.68 with the same L-R orientation as the surface crack in the pipe) and an elbow with a circumferential surface crack (a/t = 0.68) [Ji was 0.368 MN/m, (2.1 ksi-inch) in the SENT tests, while it was 0.490 MN-m (2.8 ksi-inch) in the elbow test]. The more significant finding in this work was that the compact tension (C(T)) test Ji-value was much higher at 1.086 MN/m (6.2 ksi-inch) or ∼3 times higher. The elbow to SENT to C(T) specimen comparison illustrates very large differences in constraint between these geometries. From past work by several researchers it was determined that the constraint in C(T) specimens gives Ji-values that agree well with a circumferential through-wall crack in a straight pipe, but this difference with surface-cracked elbow or pipe is envisaged to be new information to the international research community. Additionally, from state-of-the-art FE analysis of the 180-degree surface-cracked elbow test it was found that the maximum J-value occurs at a position that was about 45-degree away from the extrados location. This trend showed that caution should be exercised when selecting the crack locations for elbow integrity evaluation, since for shorter flaw lengths it may be more critical to consider a crack that is closer to the 45-degrees from the extrados, which could be true for fracture as well as stress corrosion cracking (SCC) elbow evaluations.

Mechanism of Delamination and Its Effects on Fracture of Surface Crack Bodies in Ductile Pipeline Steel

2005 ◽  
Vol 297-300 ◽  
pp. 1235-1240
Author(s):  
Hui Ru Dong ◽  
Wanlin Guo ◽  
Zheng Yang
Keyword(s):  
Fracture Toughness ◽  
Surface Crack ◽  
Safety Assessment ◽  
Pipeline Steel ◽  
Three Dimensional ◽  
Stress Constraint ◽  
Surface Cracks ◽  
Test Results ◽  
Real Material ◽  
Cracked Specimens

The effects of three-dimensional crack configurations and delaminations on fracture mechanism and fracture toughness Jc of pipeline steel were investigated experimentally by use of tensile specimens having surface cracks of different depth to length ratio. Comparison with test results of through-thickness cracks and mechanism analyses are made as well. When 3D stress constraint is larger than the strength in the thickness direction the delamination forms. As no delamination occurs in the interior of a surface crack, the constraint is higher and the fracture toughness is lower than that of the through-thickness cracks. Therefore, the nominal fracture toughness obtained from through-thickness cracked specimens is not a real material constancy, and not suitable for safety assessment of pipelines.

scholarly journals On the zeroth law of turbulence for the stochastically forced Navier-Stokes equations

2021 ◽  
Vol 0 (0) ◽  
pp. 0
Author(s):  
Yat Tin Chow ◽  
Ali Pakzad
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Energy Dissipation Rate ◽  
Mean Value ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Additional Hypothesis ◽  
The Mean ◽  
Deterministic Force ◽  
Martingale Solutions

<p style='text-indent:20px;'>We consider the three-dimensional stochastically forced Navier–Stokes equations subjected to white-in-time (colored-in-space) forcing in the absence of boundaries. Upper bounds of the mean value of the time-averaged energy dissipation rate are derived directly from the equations for weak (martingale) solutions. This estimate is consistent with the Kolmogorov dissipation law. Moreover, an additional hypothesis of energy balance implies the zeroth law of turbulence in the absence of a deterministic force.</p>

scholarly journals Wits Appraisal of a Qatari Male Population: A Comparative Study. Part II

2020 ◽  
Vol 2 (6) ◽  
Author(s):  
Hayder A. Hashim ◽  
Najat Al-Sayed ◽  
Ayah AL-Qaisi
Keyword(s):  
Three Dimensional ◽  
Mean Value ◽  
Cone Beam ◽  
Facial Appearance ◽  
Male Population ◽  
Significant Difference ◽  
The Mean ◽  
Age Range ◽  
Relationship Of ◽  
Gender Specific

Introduction: Cephalometric analysis aims to determine skeletal and dental relationships. The ANB angle, initially suggested by Rediel and applied by Steiner. is the most used angle in establishing the anteroposterior relationship of the mandible to the maxilla. However, limitations to the accuracy of the ANB angle for this purpose have been reported. To avoid these potential sources of inaccuracy a diagnostic tool was introduced by Jenkins and later modified by Jacobson and became known as the “Wits appraisal”. Aims: The aim of this study was to establish the Wits appraisal value in a sample of Qatari males, a group which had not previously been studied in this context, and to compare the findings with those from racially and ethnically differing groups as reported in the literature. Materials and Methods: The sample consisted of 28 lateral cephalometric radiographs of Qatari males with an age range of 15 to 32 years, presenting with a well-balanced facial appearance and an acceptable profile. Results: The mean value of the Wits appraisal for Qatari males in the present study was 0.50 ± 2.96. This differed at a statistically significant level from the mean value in the Jacobson study with no gender significant difference noted. On the other hand, significant differences were found when compared with previous reports on different races. Conclusion: The Wits appraisal value for the Qatari male population studied was 0.5±2.96, a result which is significantly higher than that reported in Jacobson’s study. This study revealed that the Wits appraisal is not ethnicity or gender-specific, and therefore cannot be used to differentiate between different ethnic groups. However, it can find application as an alternative to the ANB angle in the treatment of borderline cases. The application of cone beam computed tomography (CBCT) will enhance the diagnosis and treatment of cases by yielding three-dimensional views.

scholarly journals Three-Dimensional Stochastic Seepage Field Analysis of Multimedia Embankment

2021 ◽  
Vol 2021 ◽  
pp. 1-7
Author(s):  
Xiaoming Zhao ◽  
Shiyu Shang ◽  
Yuanlin Yang ◽  
Mingming Hu
Keyword(s):  
Hydraulic Conductivity ◽  
Random Field ◽  
Three Dimensional ◽  
Mean Value ◽  
Field Analysis ◽  
Anisotropy Ratio ◽  
Seepage Field ◽  
The Monte Carlo Method ◽  
Total Head ◽  
The Mean

The soil hydraulic conductivity of an embankment has strong spatial variability due to the spatiotemporal variation, both natural and artificial. The strong randomness of the hydraulic conductivity can be expressed by the coefficient of variation (COV) and the fluctuation scale θ. Moreover, different coefficients of variation and fluctuation scales correspond to different random field structures. To study the characteristics of the three-dimensional stochastic seepage field in an embankment under different COVs and fluctuation scales, we generate a three-dimensional random field of the hydraulic conductivity of multimedia embankment based on the local average subdivision technique. In particular, a calculation method for a three-dimensional random seepage field based on the Monte Carlo method combined with a three-dimensional multimedia random field and a deterministic analysis is proposed. The results showed that after three thousand realizations and considering the randomness of the hydraulic conductivity, the position of the free surface of each section in the embankment differed. The mean value of the total head decreased when the COV increased. Furthermore, when the COV was small, the change in the total head with anisotropy ratio was not evident, while the COV was large. The mean value of the total head increased with the anisotropy ratio. When the anisotropy ratio increased, the mean value of the standard deviation of the total head increased first and then decreased.

Limit Load Analysis of Elbow with Local Wall Thinning under Combined Loads

2015 ◽  
Vol 750 ◽  
pp. 198-205
Author(s):  
Peng Cui ◽  
Chang Yu Zhou
Keyword(s):  
Safety Assessment ◽  
Bending Moment ◽  
Limit Load ◽  
Orthogonal Experimental Design ◽  
Limit Loads ◽  
Pressure Pipe ◽  
Combined Loads ◽  
Wall Thinning ◽  
Volume Defect ◽  
Local Wall Thinning

The local wall thinning(LWT) is a kind of common volume defect in pressure pipe. The limit loads of elbows with LWT under pressure, bending moment, torque and their combined loads have been studied in detail by orthogonal experimental design and finite element method. The results have shown that the influence of depth and circumferential length of LWT on the limit load is more obvious compared to that of axial length when an elbow is under pressure, bending moment or torque. The change of limit bending moment and torque with the depth of LWT and circumferential length is significant for an elbow under combined bending moment and torque. At last, the safety assessment equations for elbow under combined in-plane closing bending moment and torque were proposed by regression analysis.

scholarly journals Comparison of Valgus Correction Angle between Patients with Developmental Dysplasia Hip and Normal Volunteers Measured by Three-Dimensional Reconstruction and X-Ray

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Aobo Zhang ◽  
Qing Han ◽  
Bingpeng Chen ◽  
Chenyu Wang ◽  
Xue Zhao ◽  
...  
Keyword(s):  
3D Reconstruction ◽  
Three Dimensional ◽  
Mean Value ◽  
Normal Group ◽  
Correction Angle ◽  
X Ray ◽  
Normal Volunteers ◽  
Significant Difference ◽  
The Mean ◽  
Valgus Correction Angle

Background and purpose. A new method of three-dimensional (3D) reconstruction technology was used to take place of X-ray in measuring valgus correction angle (VCA) of both DDH patients and normal volunteers to improve precision. Two different ways to define VCA according to the various conditions of patients were compared and analyzed. Methods. Bilateral VCA of 50 DDH patients and 56 normal volunteers were measured by Mimics software in the 3D method and X-ray in 2D. Two VCA (the upper VCA and the lower VCA) were measured in both two methods. Every VCA was measured by observer A and observer B for twice separately. The statistical analyses of the differences were calculated among the measurements of the VCA. Results. The mean value of the upper VCA measured in 3D was 4.95°±0.76° in DDH group and 5.56°±0.62° in the normal group with significant difference (t=−6.457, p<0.01). The VCA of DDH group and normal group measured by 3D was larger than 2D, both the upper VCA and the lower VCA. The differences indicated statistically significant. The mean value of lower VCA was 0.60° smaller than the mean value of upper VCA in normal volunteers. The mean value of the lower VCA was 0.58° larger than the mean value of the upper VCA in DDH patients. Conclusions. Compared to X-ray, 3D reconstruction technology is more accurate without conventional limitations. The lower VCA of DDH patients should be regarded as the femoral intramedullary guide angle in TKA, especially for patients with femoral deformities.

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