Three-dimensional crack growth: Numerical evaluations and experimental tests

Cali, Calogero; Citarella, Roberto; Perrella, Michele

doi:10.1016/s1566-1369(03)80019-5

Cited by 13 publications

(12 citation statements)

References 10 publications

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“…There are several approaches to calculate SIFs such as crack tip opening displacement (CTOD) approach, crack tip stress field approach, SIF extraction method from J‐integral, averaged strain energy density (SED) approach, and peak stress method (PSM) . In the present work, the SIFs are extracted from the J ‐integral based on the following equation:

J = \frac{B}{E} \cdot ((), K_{I}^{2} + K_{II}^{2}) + \frac{1}{2 G} \cdot K_{III}^{2},

where B = (1 − ν 2 ) for plane strain and 1 for plane stress and G is the tangential modulus of elasticity.…”

Section: Numerical Analysesmentioning

confidence: 99%

A computational strategy for damage‐tolerant design of hollow shafts under mixed‐mode loading condition

Lepore

Yarullin

Maligno

et al. 2018

Fatigue Fract Eng Mat Struct

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Three‐dimensional numerical analyses, using the finite element method (FEM), have been adopted to simulate fatigue crack propagation in a hollow cylindrical specimen, under pure axial or combined axial‐torsion loading conditions. Specimens, made of Al alloys B95AT and D16T, have been experimentally tested under pure axial load and combined in‐phase constant amplitude axial and torsional loadings. The stress intensity factors (SIFs) have been calculated, according to the J‐integral approach, along the front of a part through crack, initiated in correspondence of the outer surface of a hollow cylindrical specimen. The crack path is evaluated by using the maximum energy release rate (MERR) criterion, whereas the Paris law is used to calculate crack growth rates. A numerical and experimental comparison of the results is presented, showing a good agreement in terms of crack growth rates and paths.

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J = \frac{B}{E} \cdot ((), K_{I}^{2} + K_{II}^{2}) + \frac{1}{2 G} \cdot K_{III}^{2},

where B = (1 − ν 2 ) for plane strain and 1 for plane stress and G is the tangential modulus of elasticity.…”

Section: Numerical Analysesmentioning

confidence: 99%

A computational strategy for damage‐tolerant design of hollow shafts under mixed‐mode loading condition

Lepore

Yarullin

Maligno

et al. 2018

Fatigue Fract Eng Mat Struct

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Section: Introductionmentioning

confidence: 99%

“…In particular, the stress analysis on the global model is performed by FEM [1][2][3] whereas the crack propagation phase is simulated by DBEM [4][5][6][7], with the stress intensity factors (SIFs) values along the crack front calculated using the crack opening displacement (COD) method [8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

“…An automatic crack propagation simulation on the blade is performed by a coupled approach which, starting from the results of a global finite element method (FEM) analysis, proceeds through the sub modelling of the cracked volume in a DBEM dual boundary element method (DBEM) environment and subsequent propagation analysis. displacement (COD) method [8][9][10][11].Residual fatigue life of turbine blades could be predicted with reasonable accuracy from knowledge of 3D stress-strain state, SIFs, fracture resistance material properties and in correspondence of different types of operation loadings.In operation, the analysed blades experiences two main types of damage: the first is the erosive and corrosive pitting, with an initial flaw size approximately equal to 0.5 mm; the second is a welding defect introduced during the protective coating application, on the leading edge of the blade, with an initial flaw size approximately equal to 1.5 mm. The former kind of defect is modelled in this work.…”

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confidence: 99%

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Fatigue Crack Growth by FEM-DBEM Approach in a Steam Turbine Blade

Citarella¹,

Lepore²,

Shlyannikov³

et al. 2015

Ind Eng Manage

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This study is concerned with the integrity assessment of cracked steam turbine rotor components, made of steel X20Cr13, that operate under cyclic loading. Damage accumulation and growth occurred on the leading edge of turbine blade starting from part-through surface flaws. Tensile tests are performed for assessment of the main mechanical and fracture steel properties: specimens are cut out from critical zones of turbine blade body after a given operating time. The subject for experimental studies is a steel bar of circular cross-section with straight-fronted edge crack. The optical microscope measurement and the COD method are used to monitor crack growth during the tests. An automatic crack propagation simulation on the blade is performed by a coupled approach which, starting from the results of a global finite element method (FEM) analysis, proceeds through the sub modelling of the cracked volume in a DBEM dual boundary element method (DBEM) environment and subsequent propagation analysis. displacement (COD) method [8][9][10][11].Residual fatigue life of turbine blades could be predicted with reasonable accuracy from knowledge of 3D stress-strain state, SIFs, fracture resistance material properties and in correspondence of different types of operation loadings.In operation, the analysed blades experiences two main types of damage: the first is the erosive and corrosive pitting, with an initial flaw size approximately equal to 0.5 mm; the second is a welding defect introduced during the protective coating application, on the leading edge of the blade, with an initial flaw size approximately equal to 1.5 mm. The former kind of defect is modelled in this work.Critical crack lengths discovered on in service blades were varying from 28 to 32 mm.The analysed blades belongs to the 27 th stage of a 200 MW power steam turbine with operation time t=92245 hours. Fatigue failures of blades in rotating turbine disk were detected in service. Their fracture was the result of fatigue crack initiation and propagation up to the formation of a critical crack. In all of these failures, crack propagation started from leading edge as a part-through surface flaw (Figure 1) produced by erosive and corrosive pitting. Experimental TestsTensile tests were performed for determination of the main mechanical properties of blade materials. Smooth and notched specimens were cut out from critical zones of turbine blade body with given operating time in order to allow for degradation of mechanical properties such as strength and ductility. The material analysed by experimental tests is a steel X20Cr13 bar of circular cross-section with The optical microscope measurement and the COD (crack opening displacement) method are used to monitor and calculate both crack depth and superficial crack length during the tests. The validity of effective crack length approximation, estimated by continuous measurements of COD data for each fatigue crack path under cyclic loading, is considered.Growth rate tests were performed with an harmonic test-cycl...

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“…Using the aforementioned relations, the crack front shape and crack growth rate in the depth direction can be predicted. The numerical simulations in [4] are based on the Dual Boundary Element Method [2][3] whereas, in this paper, the same calculations are performed based on the Finite Element Method (FEM). In the past a comparison between FEM and DBEM results on this kind of problems was already attempted but considering separately the two loading conditions [4][5]; now the comparison is extended in case of simultaneous application of the torsion and traction fatigue loads.…”

Section: Introductionmentioning

confidence: 99%

FEM simulation of a crack propagation in a round bar under combined tension and torsion fatigue loading

Citarella¹,

Lepore²,

Maligno³

et al. 2014

Frattura Ed Integrità Strutturale

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An edge crack propagation in a steel bar of circular cross-section undergoing multiaxial fatigue\ud loads is simulated by Finite Element Method (FEM). The variation of crack growth behaviour is studied under\ud axial and combined in phase axial+torsional fatigue loading. Results show that the cyclic Mode III loading\ud superimposed on the cyclic Mode I leads to a fatigue life reduction. Numerical calculations are performed using\ud the FEM software ZENCRACK to determine the crack path and fatigue life. The FEM numerical predictions\ud have been compared against corresponding experimental and numerical data, available from literature, getting\ud satisfactory consistenc

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Three-dimensional crack growth: Numerical evaluations and experimental tests

Cited by 13 publications

References 10 publications

A computational strategy for damage‐tolerant design of hollow shafts under mixed‐mode loading condition

A computational strategy for damage‐tolerant design of hollow shafts under mixed‐mode loading condition

Fatigue Crack Growth by FEM-DBEM Approach in a Steam Turbine Blade

FEM simulation of a crack propagation in a round bar under combined tension and torsion fatigue loading

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