Fatigue crack growth for straight-fronted edge crack in a round bar

Yang, Fangzhou; Kuang, Zhen‐Bang; Shlyannikov, V.N.

doi:10.1016/j.ijfatigue.2005.07.036

Cited by 39 publications

(32 citation statements)

References 12 publications

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“…However, the 3D nonlinear analysis is so expensive that it often discourages to be selected in iterative design stages. In addition, the crack at the center surface showed the fastest crack propagation in fatigue crack growing tests 12,13) shown in Fig. 3.…”

Section: Decoupling the Diffusion Analysis And Fracturementioning

confidence: 90%

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A Prediction Model for Hydrogen Induced Cracking in a Prestressed Wire with a Fracture Analysis

Cho

Kim

2008

ISIJ Int.

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Section: Decoupling the Diffusion Analysis And Fracturementioning

confidence: 90%

“…Propagated fatigue crack shape on a round bar. 13) and crack tip are located. A plane strain hypothesis can be adopted, following a well known linear elastic solution in the vicinity of a 3D crack with an arbitrary curved front.…”

Section: Geometry and Modelmentioning

confidence: 99%

A Prediction Model for Hydrogen Induced Cracking in a Prestressed Wire with a Fracture Analysis

Cho

Kim

2008

ISIJ Int.

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“…This indicates that for straight or almost straight crack front, the crack is probably initiated around those regions [9]. Toribio, Matos [13] and Yang, Kuang [34] revealed that crack aspect ratios play an important role in determining the shape of crack front, however it depend on the type of loading. However, when a/b > 0.2, most of the SIFs located around the outer points start to decrease when compared with the SIFs closer to the central point.…”

Section: Finite Element Modellingmentioning

confidence: 98%

Mode I stress intensity factors of sickle-shaped surface cracks in round solid bars under bending moment

Ismail¹

2016

Int. J. Automot. Mech. Eng.

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Sickle-shaped crack may occur on the surface of solid round cylinder under some specific reasons such as design discontinuities or material defects. This type of crack is capable to grow circumferentially around the bar and it is called a sickle-shaped surface cracks. The complete solution of stress intensity factors (SIF) of sickle-shaped surface cracks is hard to find and therefore the objective of this paper is to present the behaviour of these cracks under remotely applied bending moment. In order to understand the role of these cracks, there are seven crack aspect ratios, a/b considered, ranging from 0.0 to 1.2. For each crack aspect ratio, there are six relative crack depths, a/D used ranging from 0.1 to 0.6. ANSYS finite element program is used to model the crack. Stress intensity factor (SIF) which is based on the J-integral is used to characterize the cracks. For relatively shallow cracks (a/D  0.3), the role of SIFs along the crack front is insignificant regardless of a/b. However, for the deeper cracks (a/D > 0.3), the effect of a/b is tremendous on the SIFs. If a/b is increased from 0.0 to 1.2, higher SIFs are obtained around the central compared with the outer regions of the crack fronts. This is due to the fact that the circumferential cracks at both sides of the bar experience lack of mode I opening mechanism compared with the crack faces at the upper side cracks. It is suggested that the phenomena of crack closure are not only caused by the plastic deformation, surface roughness and other related factors but the shape of crack also plays an important role.

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“…Crack growth assessment was performed for the round bar specimens with the straight-fronted edge notch with initial depth h 0 =0.5 mm [12]. The geometric parameters of specimen test section and growing crack are shown in Figures 3a and 3b.…”

Section: Crack Size Assessment Proceduresmentioning

confidence: 99%

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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Fatigue crack growth for straight-fronted edge crack in a round bar

Cited by 39 publications

References 12 publications

A Prediction Model for Hydrogen Induced Cracking in a Prestressed Wire with a Fracture Analysis

A Prediction Model for Hydrogen Induced Cracking in a Prestressed Wire with a Fracture Analysis

Mode I stress intensity factors of sickle-shaped surface cracks in round solid bars under bending moment

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

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