Evaluation of Coalescence Criteria for Parallel Cracks

2002 ◽  
Author(s):  
Masayuki Kamaya
Keyword(s):  
Structural Reliability ◽  
Multiple Cracks ◽  
The Finite Element Method ◽  
Multiple Crack ◽  
Systematic Analysis ◽  
Parallel Cracks ◽  
Parallel Surface ◽  
Crack Interactions ◽  
Calculation Results ◽  
Flaw Characterization

When multiple cracks approach one another, the stress intensity factor (SIF) is likely to change due to the interaction of the stress field. Since the change in the SIF is not always conservative in structural reliability evaluations, this interaction between multiple cracks must be taken into account. Section XI of the ASME Boiler and Pressure Vessel Code (Sec. XI) provides a flaw characterization method for considering multiple crack interactions. In Sec. XI, adjacent cracks are replaced by a coalesced single combined crack if they are located within a certain distance. However, no systematic analysis of the SIF for interacting parallel surface cracks is provided. Furthermore, the background of the coalescence criterion prescribed in Sec. XI is not clear. In this study, the SIF of interacting parallel cracks was calculated using the finite element method. A coalescence criterion for parallel cracks was then proposed based on the calculation results. A simplified mesh generation method was adopted in order to improve the complexity of the mesh generating procedure, which uses a transitional mesh, referred to as a “Tie Block.”

scholarly journals Deterministic and Probabilistic Investigation on Multiple Crack Interactions in a Semi-Infinite Domain

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Eui-Keun Kim ◽  
Habeun Choi ◽  
Kyoungsoo Park ◽  
Won-Hee Kang
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Shielding Effect ◽  
Multiple Cracks ◽  
Infinite Domain ◽  
Multiple Crack ◽  
Crack Interactions ◽  
Safety And Reliability ◽  
Crack Shielding Effect

The investigation of multiple crack interactions in fracture mechanics is important to predict the safety and reliability of structures. This study aims to investigate the interactions of multiple parallel cracks in a semi-infinite domain in both deterministic and probabilistic ways by using an automated finite element modeling procedure and the Monte Carlo simulation. The stress intensity factor is considered as an indicator of failure and accurately evaluated by using the domain integral technique. The variation of the stress intensity factor according to the position, the length, and the number of cracks is demonstrated. In a probabilistic investigation, the effects of the number of cracks, the random distribution of the crack lengths, and the crack interactions to the failure probability are studied for a semi-infinite domain. The stress redistribution among multiple cracks, the effect of unevenly distributed crack lengths, and the combined effect of crack length uncertainties and a crack shielding effect have been examined.

The Reciprocal Effect Among a Quarter-Circle Corner Crack and a Non-Aligned Surface Crack of Comparable Size in an Infinitely Large Plate Under Uniaxial Tension

2018 ◽  
Author(s):  
M. Perl ◽  
C. Levy ◽  
Q. Ma
Keyword(s):  
Surface Crack ◽  
Mutual Influence ◽  
Mutual Effect ◽  
Multiple Cracks ◽  
Relative Depth ◽  
Reciprocal Effect ◽  
Corner Crack ◽  
Parallel Cracks ◽  
Parallel Surface ◽  
Comparable Size

The reciprocal effect between a quarter-circle corner crack and a non-aligned surface crack of comparable size is addressed in the present study. The significance of understanding the reciprocal effect between the non-aligned parallel cracks is to assist in the evaluation of non-aligned multiple cracks as required in various fitness-for-service codes. For non-aligned parallel cracks, on-site inspection needs to decide whether the cracks should be treated as coalesced or separate multiple cracks. In the existing literature, criteria and standards for the adjustment of multiple non-aligned cracks are very source dependent, and those criteria and standards are often derived from on-site service experience without rigorous and systematic verification. Based on this observation, the authors previously reported on the effect of an embedded parallel crack on an edge crack in 2-D scenarios and, more recently, in 3-D scenarios of a circular corner crack influenced by a parallel surface crack. It may be just as important to evaluate the mutual effect of a quarter-circle corner crack on a non-aligned surface crack as reflected in their stress intensity factors (SIFs). In the present study, the quarter-circle corner crack and the non-aligned surface crack are assumed to be of the same length a2 = a1 = 15mm. While keeping throughout the entire analysis the geometry of the quarter-circle corner crack unchanged, the relative depth of the semi-elliptical surface crack is varied so that b1/a1 = 0.2–1.0. For each particular case a pair of horizontal (H) and vertical (S) separation distances between the two cracks is chosen (H/a2 = 0.4–2 and S/a2 = −0.5–2) and the SIFs along the 3D crack fronts are extracted for both the corner and the surface crack. The reciprocal effect on the SIFs for both cracks are discussed. It is found that the mutual influence between the corner crack and the surface crack are equally important, and each may dominate the decision making based on present criteria and standards in Fitness-for-Service.

scholarly journals NUMERICAL ANALYSIS OF CORRUGATED STEEL PLATE BRIDGE WITH REINFORCED CONCRETE RELIEVING SLAB

2015 ◽  
Vol 22 (5) ◽  
pp. 585-596 ◽  
Author(s):  
Damian BEBEN ◽  
Adam STRYCZEK
Keyword(s):  
Reinforced Concrete ◽  
Numerical Analysis ◽  
Steel Plate ◽  
Numerical Models ◽  
Experimental Tests ◽  
Bridge Engineering ◽  
Steel Plates ◽  
The Finite Element Method ◽  
Calculation Results ◽  
Rc Slab

The paper presents a numerical analysis of corrugated steel plate (CSP) bridge with reinforced concrete (RC) relieving slab under static loads. Calculations were made based on the finite element method using Abaqus software. Two computation models were used; in the first one, RC slab was used, and the other was without it. The effect of RC slab to deformations of CSP shell was determined. Comparing the computational results from two numerical models, it can be concluded that when the relieving slab is applied, substantial reductions in displacements, stresses, bending mo­ments and axial thrusts are achieved. Relative reductions of displacements were in the range of 53–66%, and stresses of 73–82%. Maximum displacements and bending moments were obtained at the shell crown, and maximum stresses and axial thrusts at the quarter points. The calculation results were also compared to the values from experimental tests. The course of computed displacements and stresses is similar to those obtained from experimental tests, although the absolute values were generally higher than the measured ones. Results of numerical analyses can be useful for bridge engineering, with particular regard to bridges and culverts made from corrugated steel plates for the range of necessity of using additional relieving elements.

scholarly journals Cause Analysis and Countermeasures of a Breakdown Failure of Flexible 110 kV Cable Terminal

2018 ◽  
Vol 38 ◽  
pp. 04004
Author(s):  
Feng Huang
Keyword(s):  
Electric Field ◽  
Electric Field Intensity ◽  
Field Model ◽  
Semiconductor Layer ◽  
Mechanism Analysis ◽  
The Finite Element Method ◽  
Cable Insulation ◽  
Cause Analysis ◽  
Breakdown Mechanism ◽  
Calculation Results

disintegration examination and analysis are employed in flexible terminal breakdown of 110 kV XLPE insulated cables. It is considered that the main reason of breakdown is the separation of the stress cone of the terminal and the fracture of the semi- conductive layer of the cable insulation. Therefore, the finite element method is used to electric field model and simulate the dislocation fault of internal stress cone and outer semiconductor layer of cable insulation. The distribution of the electric field intensity is calculated and compared. The simulation and calculation results verify the validity of the breakdown mechanism analysis, and put forward some practical suggestions.

scholarly journals Multiple crack identification in stepped beam by measurements of natural frequencies

2014 ◽  
Vol 36 (2) ◽  
pp. 119-132
Author(s):  
Nguyen Tien Khiem ◽  
Duong The Hung ◽  
Vu Thi An Ninh
Keyword(s):  
Crack Detection ◽  
Natural Frequencies ◽  
Rayleigh Quotient ◽  
Crack Identification ◽  
Multiple Cracks ◽  
Simple Relationship ◽  
Multiple Crack ◽  
Scanning Method ◽  
New Approach ◽  
Efficient Procedure

A new approach is proposed for calculating natural frequencies and crack detection in a stepped cantilever beam with arbitrary number of cracks. This is based an explicit expression of the natural frequencies in term of crack parameter derived in the form similar to the so-called Rayleigh quotient for vibrating beam. The obtained simple relationship between natural frequencies and crack parameters enables not only accurate calculating the natural frequencies but also to develop an efficient procedure for detecting multiple cracks from given natural frequencies. The proposed technique called crack scanning method is illustrated and validated by numerical results.

scholarly journals INFORMATIZATION OF CONSTRUCTION MANAGEMENT AS A BASIS FOR PREVENTING MAN-MADE ACCIDENTS

2021 ◽  
Vol 4 (4) ◽  
pp. 11-31
Author(s):  
S. Koryagina
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
The Finite Element Method ◽  
Calculation Results ◽  
Definition Of ◽  
Deep Pits ◽  
Geotechnical Problems ◽  
Seismic Impacts ◽  
Base Structure ◽  
Element Method

the article presents the principles and algorithms of the finite element method in solving geotechnical prob-lems taking into account seismic impacts for determining the stress-strain state of structures and slope stabil-ity, implemented in the Midas GTS NX software package. GTS NX allows you to perform calculations of various types of geotechnical problems and solve complex geotechnical problems in a single software envi-ronment. GTS NX covers the entire range of engineering and geotechnical projects, including calculations of the "base-structure" system, deep pits with various mounting options, tunnels of complex shape, consolida-tion and filtration calculations, as well as calculations for dynamic actions and stability calculations. At the same time, all types of calculations in GTS NX can be performed both in 2D and in 3D. The author does not claim to be the author of the finite element method, but he cannot do without pointing out the basic equa-tions, as this affects the definition of the boundaries of use, the formulation of algorithms for constructing calculation schemes and the analysis of calculation results.

Analysis by the mixed method of statically indeterminate frames with elements of increased rigidity and numerical verification of the calculation results using the finite element method

2021 ◽  
Vol 14 (2) ◽  
pp. 54-66
Author(s):  
Svetlana Sazonova ◽  
Viktor Asminin ◽  
Alla Zvyaginceva
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Initial Data ◽  
Mixed Method ◽  
Numerical Verification ◽  
Bending Moments ◽  
The Finite Element Method ◽  
Calculation Results ◽  
Internal Forces ◽  
Element Method

The sequence of application of the mixed method for calculating internal forces in statically indeterminate frames with elements of increased rigidity is given. The main system is chosen for the frame with one kinematic and one force unknown. The canonical equations of the mixed method are written, taking into account their meaning. Completed the construction of the final diagram of the bending moments and all the necessary calculations and checks. When calculating integrals, Vereshchagin's rule is applied. The solution of the problem is checked by performing the calculation using the computer program STAB12.EXE; the results of the calculations are numerically verified using the finite element method. An example of the formation of the initial data for the STAB12.EXE program and the subsequent processing of the calculation results, the rules for comparing the numerical results and the results obtained in the calculation of the frame by the mixed method are given.

scholarly journals On Simplified Calculations of Leakage Inductances of Power Transformers

Energies ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4952 ◽  
Author(s):  
Tadeusz Sobczyk ◽  
Marcin Jaraczewski
Keyword(s):  
Power Transformer ◽  
Short Circuit ◽  
Power Transformers ◽  
Stray Field ◽  
Good Representation ◽  
The Finite Element Method ◽  
Leakage Inductance ◽  
Leakage Flux ◽  
Calculation Results ◽  
Discrete Differential Operator

This paper deals with the problem of the leakage inductance calculations in power transformers. Commonly, the leakage flux in the air zone is represented by short-circuit inductance, which determines the short-circuit voltage, which is a very important factor for power transformers. That inductance is a good representation of the typical power transformer windings, but it is insufficient for multi-winding ones. This paper presents simple formulae for self- and mutual leakage inductance calculations for an arbitrary pair of windings. It follows from a simple 1D approach to analyzing the stray field using a discrete differential operator, and it was verified by the finite element method (FEM) calculation results.

Pipeline On-Bottom Stability Analysis Based on FEM Model

2011 ◽  
Author(s):  
Yong Bai ◽  
Zhimeng Yu
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Design Procedure ◽  
Element Model ◽  
The Finite Element Method ◽  
Fem Model ◽  
Engineering Software ◽  
Calculation Results ◽  
Pipeline Design ◽  
Element Method

Pipeline on-bottom stability is one of the sophisticated problems in subsea pipeline design procedure. Due to the uncertainty of the pipe-soil interaction and environment loads, including wave, current, or earthquake, etc., it is classified as the typical nonlinear problem. The Finite Element Method is introduced into pipeline engineering several years ago. More and more special engineering software such as AGA, PONDUS are available in market. However, when doing a project, some abnormal data was found when compared the DnV calculation results and AGA. In order to know the behavior of pipeline on seabed under wave and current load, finite element method – ABAQUS is introduced to do this analysis. The ABAQUS/explicit is used to simulate 600s pipeline dynamic response. The pipeline is supposed to be exposed on seabed and the selected seabed model is large enough to avoid the edge effect. ABAQUS calculation results are compared with the requirements in DnV rules to verify the validity of finite element model.

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