Frequency Transfer Function From Fluid Temperature Fluctuations to Stress Intensity Factors

2003 ◽  
Author(s):  
Naoto Kasahara ◽  
Masanori Ando ◽  
Ihciro Furuhashi ◽  
Chen Fuquan ◽  
Hideki Takasho
Keyword(s):  
Stress Intensity ◽  
Transfer Function ◽  
Stress Intensity Factors ◽  
Temperature Fluctuation ◽  
Fatigue Cracks ◽  
Temperature Fluctuations ◽  
Fluid Temperature ◽  
Intensity Factors ◽  
Rational Analysis ◽  
Frequency Transfer

Temperature fluctuation from incomplete fluid mixing can induce fatigue cracks on structures of nuclear components, which should be prevented. For rational analysis of this phenomenon, the authors have developed a frequency transfer function that translates fluid temperature fluctuation to stress intensity factors. This function is formulated by a product of the effective heat transfer and the stress intensity factor functions, and enables us to quickly calculate stresses intensity factors induced by fluid temperature fluctuations. Furthermore, it can evaluate sensitivities of stress intensity factors to frequencies of temperature fluctuation, Biot number and constraint conditions of structures. Applicability of this function was verified through comparison with stress intensity factors calculated by the finite element method.

Monitoring Fatigue Cracks and Stress Intensity Factors Based on the Distributed Dislocation Technique

2012 ◽  
Vol 525-526 ◽  
pp. 189-192
Author(s):  
Ramdane Boukellif ◽  
Andreas Ricoeur
Keyword(s):  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Crack Detection ◽  
Dimensional Space ◽  
Fatigue Cracks ◽  
Particle Swarm Algorithm ◽  
Problem Solution ◽  
Intensity Factors ◽  
Unknown Parameters ◽  
Factor Measurement

We present a method for crack detection and stress intensity factor measurement in plate structures by using strain gauges and applying the dislocation method. The presented approach is based on the strain measured at different locations on the surface of the structure. This allows both the identification of crack position parameters, such as length, location and angles with respect to a reference coordinate system and the calculation of stress intensity factors (SIF). The method solving the direct problem is based on the idea of representing the crack by a line of point dislocations. The latter are formed by applying a constant displacement between adjacent points located at either side of the crack. Thus, the approach is based on the weighted superposition of elastic Greens functions representing the strain field due to the presence of a crack, where the weights are being identified by inverse problem solution. Since the strain fields are controlled by both external loads and the crack growth the unknown parameters are crack length, position and inclination as well as loading quantities. The particle swarm algorithm (PSO) came out to be most suitable for parameter identification in a high dimensional space.

Mode I and Mode II Stress Intensity Factors Based on Crack Opening and Sliding Displacements

2011 ◽  
Vol 179-180 ◽  
pp. 1417-1422
Author(s):  
You Li Ma
Keyword(s):  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Stress Ratio ◽  
Fatigue Cracks ◽  
Crack Opening ◽  
Intensity Factors ◽  
Slant Angle ◽  
Measured Stress ◽  
Discontinuous Displacement ◽  
Made In

It is necessary to study crack opening and sliding discontinuous displacement behavior under mixed-mode conditions because parts or structures of a machine with a crack maybe subject to stress from various directions. In this study ,therefore, using the cracks with different slant angle, which are made in circle stress of modeⅠwith stress ratio of R=0, the opening and sliding discontinuous displacements are measured ,so that modeⅠand mode Ⅱ stress intensity factors (KⅠ)mes and (KⅡ)mes at the crack tip are calculated. As a result, the measured stress intensity factors value of (KⅠ)mes from the fatigue crack with the slant angle β=60 deg. is smaller than the theoretical one (KⅠ). But for mode Ⅱ,(KⅡ)mes is about the same with (KⅡ). On the other hand, for the fatigue cracks with smaller slant angle β=45 deg.,(KⅡ)mes declined because of the crack-surface contact while (KⅠ)mes reduced.

Calculation of Stress Intensity Factors and Crack Opening Displacements for Cracks Subjected to Complex Stress Fields

2003 ◽  
Vol 125 (3) ◽  
pp. 260-266 ◽  
Author(s):  
A. Kiciak ◽  
G. Glinka ◽  
D. J. Burns
Keyword(s):  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Fatigue Cracks ◽  
Crack Opening ◽  
Complex Stress ◽  
Pressure Vessels ◽  
Stress Fields ◽  
Function Technique ◽  
Weight Functions ◽  
Intensity Factors

Fatigue cracks in shot peened and case hardened notched machine components and high-pressure vessels are subjected to the stress fields induced by the external load and the residual stress resulting from the surface treatment or autofrettage. Both stress fields are usually nonuniform and available handbook stress intensity factor solutions are in most cases unavailable for such configurations, especially in the case of two-dimensional surface breaking cracks such as semi-elliptical and quarter-elliptical cracks at notches. The method presented in the paper makes it possible to calculate stress intensity factors for such cracks and complex stress fields by using the generalized weight function technique. It is also shown that the generalized weight functions make it possible to calculate the crack opening displacement field often used in the determination of the critical load or the critical crack size.

X-Ray Micro-Tomography Coupled to the Extended Finite Element Method to Investigate Microstructurally Short Fatigue Cracks

2007 ◽  
Vol 567-568 ◽  
pp. 301-304 ◽  
Author(s):  
Emilie Ferrié ◽  
Jean Yves Buffière ◽  
Wolfgang Ludwig ◽  
Anthony Gravouil
Keyword(s):  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Crack Front ◽  
Extended Finite Element Method ◽  
Fatigue Cracks ◽  
Intensity Factors ◽  
Extended Finite Element ◽  
X Ray ◽  
The Real ◽  
Micro Tomography

In this paper we will present how it is possible to couple a 3D experimental technique with a 3D numerical method in order to calculate the stress intensity factors along the crack front taking into account the real shape of the crack. This approach is used to characterize microstructurally short fatigue cracks that exhibit a rather complicated 3D shape. The values of the stress intensity factors are calculated along the crack front at different stages of crack propagation and it can be seen that the crack shape irregularities introduce rather important fluctuations of the values of KI, KII and KIII along the crack front. The values of KI obtained taking into account the real shape of the crack are significantly different from the ones calculated using an approach based on a shape assumption

Shear Mode Stress Intensity Factors for Serrated Crack Fronts

2017 ◽  
Vol 754 ◽  
pp. 214-217 ◽  
Author(s):  
Stanislav Žák ◽  
Jana Horníková ◽  
Pavel Šandera
Keyword(s):  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Fatigue Cracks ◽  
Local Stress ◽  
Shear Mode ◽  
Intensity Factors ◽  
Crack Driving Force ◽  
Bcc Metals ◽  
Shear Modes ◽  
Mode Stress

The paper is related to experiments on near-threshold fatigue cracks under shear modes II, III and II+III in bcc metals. Cylindrical bars with circumferential cracked notch were loaded by shear force. In-plane precracks with microtortuous geometry were created by compressive cyclic loading in mode I to measure the effective values of the remote crack driving force. Fatigue cracks in bcc metals loaded under remote shear modes II, III and II+III always grew by creation of local tongues loaded in mode II and their coalescence. Therefore, serrated precrack fronts of a linear roughness identical to those of the real fronts were modeled and the related local stress intensity factors k2 were calculated. Since such FEM calculation for various values of roughness were time consuming, a further task was to identify a lowest number of isolated teeth that produces k2 components identical with those created by the continuously serrated crack front. The results reported in this article reveal that this condition is fulfilled by only two isolated teeth.

Stress Intensity Factors Evaluation for Rolling Contact Fatigue Cracks in Rails

2016 ◽  
Vol 60 (4) ◽  
pp. 645-652 ◽  
Author(s):  
Reza Masoudi Nejad ◽  
Khalil Farhangdoost ◽  
Mahmoud Shariati ◽  
Majid Moavenian
Keyword(s):  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Fatigue Cracks ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Rolling Contact ◽  
Intensity Factors
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