scholarly journals Determination of Stress Intensity Factors in Low Pressure Turbine Rotor Discs

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Ivana Vasovic ◽  
Stevan Maksimovic ◽  
Katarina Maksimovic ◽  
Slobodan Stupar ◽  
Gordana Bakic ◽  
...  
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Finite Elements ◽  
Intensity Factor ◽  
Turbine Rotor ◽  
Analytic Formula ◽  
Intensity Factors ◽  
Lp Turbine ◽  
Critical Locations

An attention in this paper is focused on the stress analysis and the determination of fracture mechanics parameters in low pressure (LP) turbine rotor discs and on developing analytic expressions for stress intensity factors at the critical location of LP steam turbine disc. Critical locations such as keyway and dovetail area experienced stress concentration leading to crack initiation. Major concerns for the power industry are determining the critical locations with one side and fracture mechanics parameters with the other side. For determination of the critical locations in LP turbine rotor disc conventional finite elements are used here. For this initial crack length and during crack growth it is necessary to determine SIFs. In fatigue crack growth process it is necessary to have analytic formulas for the stress intensity factor. To determine analytic formula for stress intensity factor (SIF) of cracked turbine rotor disc special singular finite elements are used. Using discrete values of SIFs which correspond to various crack lengths analytic formula of SIF in polynomial forms is derived here. For determination of SIF in this paper, combinedJ-integral approach and singular finite elements are used. The interaction of mechanical and thermal effects was correlated in terms of the fracture toughness.

Experimental Determination of Stress Intensity Factor Distributions in Engineering Problems

1993 ◽  
Vol 46 (11S) ◽  
pp. S29-S40 ◽  
Author(s):  
C. W. Smith
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Intensity Factors ◽  
Local Modes ◽  
Engineering Problems ◽  
Practical Engineering ◽  
Stress Optic Law

Following a brief introduction of the concept of stress intensity factor from fracture mechanics and the frozen stress method from photoelasticity, an algorithm is developed from fracture mechanics equations and the stress-optic law for converting stress fringe measurements into a form useful for determining the stress intensity factor. This algorithm covers all three local modes of deformation and is used to analyse frozen stress slices along the border of cracks to obtain distributions for stress intensity factors K1, K2 and K3. The use of the method is illustrated by three examples from practical engineering problems and results are compared with the literature where possible.

Stress Intensity Factors for Unequal Longitudinal-Radial Cracks in Thick-Walled Cylinders

1991 ◽  
Vol 113 (1) ◽  
pp. 22-27 ◽  
Author(s):  
J. L. Desjardins ◽  
D. J. Burns ◽  
R. Bell ◽  
J. C. Thompson
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Finite Elements ◽  
Intensity Factor ◽  
Stress Intensity Factors ◽  
Two Dimensional ◽  
Intensity Factors ◽  
Radial Cracks ◽  
Good Agreement

Finite elements and two-dimensional photoelasticity have been used to analyze thick-walled cylinders which contain arrays of straight-fronted, longitudinal-radial cracks of unequal depth. The stress intensity factor K1 has been computed for the dominant crack and for some of the surrounding cracks. Cylinders with 2, 4, 6, 8, 16, 36 and 40 cracks have been considered. Good agreement has been obtained between the experimental and the numerical results and, for cylinders with 2 or 4 cracks, with previously published predictions. The results for all of the foregoing cases are used to develop simple, approximate techniques for estimating K1 for the dominant crack, when the total number of cracks is different from those that have been considered herein. Estimates of K1 obtained by these techniques agree well with corresponding finite element results.

Determination of Residual Stresses From Stress Intensity Factor Measurements

1971 ◽  
Vol 93 (2) ◽  
pp. 242-246 ◽  
Author(s):  
S. Vaidyanathan ◽  
I. Finnie
Keyword(s):  
Residual Stress ◽  
Stress Intensity Factor ◽  
Electron Beam ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Stress Measurement ◽  
Residual Stress Distribution ◽  
Intensity Factors ◽  
State Of Stress

It is shown that a familiar procedure for obtaining stress intensity factors for a plate containing a through crack may be inverted. That is, stress intensity factor measurements may be used to deduce the state of stress that existed in the plate prior to introduction of the crack. This approach to residual stress measurement appears to be superior to existing methods for situations in which the stress gradients in the plane of the plate are large. As an illustration, the residual stress distribution in an electron beam welded aluminum plate is determined.

scholarly journals A Numerical Approach for the Determination of Mode I Stress Intensity Factors in PMMA Materials

2014 ◽  
Vol 4 (3) ◽  
pp. 644-648
Author(s):  
F. Khelil ◽  
M. Belhouari ◽  
N. Benseddiq ◽  
A. Talha
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Stress Intensity Factors ◽  
Numerical Approach ◽  
Experimental Results ◽  
Intensity Factors ◽  
Element Analysis ◽  
Experimental Values

An evaluation technique of the KI stress intensity factors (SIF) by a numerical investigation using line strain method is presented in this paper. The main purpose of this research is to re-analyze experimental results of fracture loads from polymethyl-metacrylate (PMMA) specimens (fully finite plates). Stress intensity factor equation calculation is derived from the Williams stress asymptotic expansion. Possible error caused by strain gradients across the gage length is minimized by integrating the equation in the KI  calculation. Theoretical and computed values using finite element analysis of stress intensity factors are compared with experimental results. A good agreement is observed between the present approach and experimental values. It is shown that, in the case of a through-plate crack, the stress intensity factor can be calculated with adequate accuracy using the proposed method.

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