scholarly journals Numerical Investigation on Crack Propagation for a Central Cracked Brazilian Disk Concerning Friction

2021 ◽  
Vol 11 (6) ◽  
pp. 2839
Author(s):  
Jiuzhou Huang ◽  
Xin Pan ◽  
Jianxiong Li ◽  
Shiming Dong ◽  
Wen Hua
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Propagation ◽  
Relative Length ◽  
Mode I ◽  
Brazilian Disk ◽  
Crack Type ◽  
T Stress ◽  
Crack Propagation Angle

This paper concerns the effect of friction on crack propagation for the centrally cracked Brazilian disk under diametric forces by using a modified finite element method. It shows that the mode II stress intensity factor decreases obviously with the increase of friction after the crack is closed, while friction has no influence on the stress intensity factor of mode I and T-stress. Meanwhile, there are some significant influences on the crack propagation due to the change of the friction after the crack is closed with the appropriate loading angle and relative length of the crack. When T-stress is positive, the effect of friction becomes obvious and the crack propagation angle increases with a lager friction coefficient. With increasing the friction, the deviation for the crack propagation trajectory increases and the curvature of path decreases, which may lead to the change of crack type. Additionally, the larger relative crack length can amplify the effect of friction, which is similar to the loading angle.

scholarly journals Influence of Stress Intensity Factor on Rail Fatigue Crack Propagation by Finite Element Method

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5720
Author(s):  
Ruipeng Gao ◽  
Mengmeng Liu ◽  
Bing Wang ◽  
Yiran Wang ◽  
Wei Shao
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Propagation ◽  
Crack Length ◽  
Rolling Contact ◽  
Mode I ◽  
Propagation Angle ◽  
Crack Propagation Angle

Wheel rail rolling contact fatigue is a very common form of damage, which can lead to uneven rail treads, railhead nuclear damage, etc. Therefore, ANSYS software was used to establish a three-dimensional wheel–rail contact model and analyze the effects of several main characteristics, such as the rail crack length and crack propagation angle, on the fatigue crack intensity factor during crack propagation. The main findings were as follows: (1) With the rail crack length increasing, the position where the crack propagated by mode I moved from the inner edge of the wheel–rail contact spot to the outer edge. When the crack propagated to 0.3–0.5 mm, it propagated to the rail surface, causing the rail material to peel or fall off and other damage. (2) When the crack propagation angle was less than 30°, the cracks were mainly mode II cracks. When the angle was between 30 and 70°, the cracks were mode I–II cracks. When the angle was more than 70°, the cracks were mainly mode I cracks. When the crack propagation angle was 60°, the equivalent stress intensity factor reached the maximum, and the rail cracks propagated the fastest.

Mode I stress intensity factor and T-stress by exponential matrix method

2019 ◽  
Vol 103 ◽  
pp. 102287
Author(s):  
J.-M. Nianga ◽  
F. Mejni ◽  
T. Kanit ◽  
A. Imad ◽  
J. Li
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Matrix Method ◽  
Mode I ◽  
T Stress ◽  
Exponential Matrix

Analysis of Stress Intensity Factor for Cracked Flattened Brazilian Disk: Part I – Analysis Method and Pure Mode I Crack

2012 ◽  
Vol 525-526 ◽  
pp. 85-88 ◽  
Author(s):  
Shi Ming Dong ◽  
Qing Yuan Wang
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Closed Form Expression ◽  
Mode I ◽  
Pure Mode ◽  
Analysis Method ◽  
The Finite Element Method ◽  
Brazilian Disk ◽  
Mode I Loading

In order to solve the problem how to calculate the stress intensity factor for a cracked flattened Brazilian disk under mode I loading, the finite element method was employed to analyze the stress intensity factor for the cracked flattened Brazilian disk under mode I loading, based on the closed-form expression of the stress intensity factor for a cracked Brazilian disk subjected to pressure. The analyzed result shows that within the certain range of the load distribution angle, the formula of the stress intensity factor for the cracked Brazilian disk can be directly used to calculate the stress intensity factor for the cracked flattened Brazilian disk under mode I loading.

scholarly journals Rectangular Strain-Rosette Method for Measuring the Mode I Stress-Intensity Factor KI and T-stress

2017 ◽  
Vol 7 (5) ◽  
pp. 1922-1929
Author(s):  
A. Hamdi ◽  
N. Benseddiq ◽  
F. Mejni
Keyword(s):  
Stress Intensity Factor ◽  
Asymptotic Expansion ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Tip ◽  
Mode I ◽  
Finite Element Calculations ◽  
Higher Order Terms ◽  
Strain Rosette ◽  
T Stress

In this paper, a new experimental technique for measuring Stress Intensity Factor (SIF) and T-stress under mode I loading is developed. The expressions of the normal and tangential strains close to the crack tip are given using the first five terms of the generalized Westergaard formulation. In order to accurately determine the SIF and T-stress, the method exploits the optimal positioning of a rectangular strain gage rosette near a crack tip in mode I. Thus, errors due to the higher order terms of the asymptotic expansion are eliminated. Finally, a comparison of the analytical results with a finite element calculations, for different specimen dimensions, is carried out.

The effect of friction on crack propagation in the dovetail fixings of compressor discs

1998 ◽  
Vol 212 (3) ◽  
pp. 171-181 ◽  
Author(s):  
R L Burguete ◽  
E A Patterson
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Propagation ◽  
Coefficient Of Friction ◽  
Stress Intensity Factors ◽  
Mode I ◽  
Mode Ii ◽  
Intensity Factors ◽  
The Coefficient Of Friction

Stress frozen photoelasticity has been used to model dovetail compressor blade fixings. During loading a known coefficient of friction was applied and the effect of the variation of this parameter on crack initiation and propagation was investigated. Data were recorded from the specimen using an automated computer aided polariscope based on the method of phase stepping. Isochromatic and isoclinic data were collected and used to determine the stress distribution, the stress intensity factor and the crack propagation direction. The method to predict the direction of crack propagation has been improved so that photoelastic data can be used reliably for this purpose. Three values of the coefficient of friction were used for two different dovetail geometries. It was found that the initial values of the mode II stress intensity factors were higher for a lower friction coefficient. An increase in crack length produced a corresponding decrease in the mode I stress intensity factor and a decrease in the mode II value. It was concluded that the coefficient of friction influenced crack growth at all stages of crack growth because it affects the relative levels of the mode I and mode II stress intensity factors. This has an effect on the direction of the maximum principal stress direction and so on the direction of crack propagation.

Fracture analysis of a semi-elliptical crack in a nozzle–vessel junction under external loads

2011 ◽  
Vol 226 (4) ◽  
pp. 871-886 ◽  
Author(s):  
K Sedighiani ◽  
J Mosayebnejad ◽  
M Mafi
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Stress Intensity Factors ◽  
Elliptical Crack ◽  
External Loading ◽  
Mode I ◽  
Loading Conditions ◽  
Intensity Factors ◽  
T Stress

In many previous investigations, the mode I stress intensity factor has been usedalone to analyse and predict the life of cracked cylindrical components. In this article, three-dimensional elastic finite element method was used to analyse semi-elliptical cracks located in the stress concentration area of a nozzle–vessel junction. Stress intensity factors and T-stresses were calculated for different geometrical configurations of a semi-elliptical crack and nozzle–vessel junction under different external loading conditions. The influence of these various parameters and loading conditions on both the stress intensity factors and T-stress is discussed. Itis shown that, for many cases, the mode II stress intensity factor and T-stress are not negligible compared to the mode I stress intensity factor.

Mode-I Crack Control by SMA Fiber With a Special Configuration

2009 ◽  
Author(s):  
M. Jin
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Theoretical Model ◽  
Shape Memory Alloy ◽  
Intensity Factor ◽  
Crack Propagation ◽  
Shape Memory ◽  
Crack Opening ◽  
Mode I ◽  
Mode I Crack

Crack propagation in solid members is an important reason for structure failure. In recent years, many research interests are focused on intelligent control of crack propagation. With the rise in temperature, contraction of prestrained shape memory alloy (SMA) fiber embedded in matrix makes retardation of crack propagation possible. However, with the rise in temperature, separation of SMA fiber from matrix is inevitable. This kind of separation weakens effect of SMA fiber on crack tip. To overcome de-bonding of shape memory alloy (SMA) fiber from matrix, a knot is made on the fiber in this paper. By shape memory effect with the rise in temperature, the knotted SMA fiber generates a couple of recovery forces acting on the matrix at the two knots. This couple of recovery forces may restrain opening of the mode-I crack. Based on Tanaka constitutive law on SMA fiber and complex stress function near an elliptic hole under a point load, a theoretical model on mode-I control is proposed. An analytical expression of relation between stress intensity factor (SIF) of mode-I crack closure and temperature is got. Simulation results show that stress intensity factor of mode-I crack closure decreases obviously with the rise in temperature higher than the austenite start temperature of SMA fiber, and that there is an optimal position for SMA fiber to restrain crack opening, which is behind the crack tip. Therefore the theoretical model supports that prestrained SMA fiber with knots in martensite can be used to control mode-I crack opening effectively because de-bonding between fiber and matrix is eliminated. Specimen of epoxy resin embedded with knotted SMA fiber can be made in experiment and is useful to an analytical study. However, in practical point of view, SMA fiber should be embedded in engineering structure material such as steel, aluminum, etc. The embedding process in these matrix materials should be studied systematically in the future.

scholarly journals Dynamic Fracture Experiment of Medium with Defects under Impact Loading

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Chenglong Xiao ◽  
Renshu Yang ◽  
Chenxi Ding ◽  
Cheng Chen ◽  
Yong Zhao ◽  
...  
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Dynamic Fracture ◽  
Mode I ◽  
Mode Ii ◽  
Obvious Effect ◽  
Initiation Stage

Defects have a significant effect on the dynamic fracture characteristics of the medium. In this paper, the dynamic fracture experiment of specimens with bias precracks is designed by utilizing the digital laser dynamic caustics system, and the effect of defect eccentricity on the dynamic fracture behavior is studied. Research shows that crack propagation can be divided into four stages: crack initiation stage, attraction stage, repulsion stage, and specimen fracture stage. The change of defect eccentricity has no obvious effect on the crack propagation behavior in the crack initiation stage and penetration stage but has a significant effect on the attraction stage and specimen fracture stage. In the process of the interaction between defect and crack, mode I stress intensity factor decreases at first and then increases. The decrease of mode I stress intensity factor reduces with the increase of defect eccentricity. The value of mode II stress intensity factor changes from negative to positive. With the increase of defect eccentricity, the symbol of mode II stress intensity factor no longer changes. The fractal dimension and the deflection angle of crack trajectory both decrease with the increase of defect eccentricity. In addition, a numerical simulation of the experiment is conducted by ABAQUS, which provides results that are in good agreement with the experimental results.

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