Evaluation of Finite Element Calculations in a Cracked Cylinder Under Internal Pressure by Speckle Photography

1983 ◽  
Vol 50 (4a) ◽  
pp. 896-897 ◽  
Author(s):  
G. H. Kaufmann ◽  
A. M. Lopergolo ◽  
S. Idelsohn
Keyword(s):  
Experimental Data ◽  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Mode I ◽  
Speckle Photography ◽  
Crack Line ◽  
Finite Element Calculations ◽  
Pressurized Cylinder ◽  
Good Agreement

The usefulness of using the speckle photography technique in fracture mechanics to check numerical calculations is demonstrated for an internally pressurized cylinder with a surface flaw. A pointwise technique was utilized to measure the opening displacements along the crack line and the Mode I stress-intensity factor was determined by extrapolating these results to the crack tip. Finite element calculations were performed to be compared with experimental data and good agreement was obtained.

Modeling approach to evaluating reduction in stress intensity factor in center-cracked plate with piezoelectric actuator patches

2016 ◽  
Vol 28 (10) ◽  
pp. 1334-1345 ◽  
Author(s):  
Ahmed Abuzaid ◽  
Meftah Hrairi ◽  
MSI Shaik Dawood
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Piezoelectric Actuator ◽  
Piezoelectric Actuators ◽  
Mode I ◽  
Damage Propagation ◽  
Piezoelectric Patch ◽  
Cracked Structure

Active repairs using piezoelectric actuators can play a significant role in reducing the crack damage propagation in thin plate structures. Mode-I crack opening displacement is the most predominant one in tension, and it is responsible for the failure which in turn affects the load carrying capability of the cracked structure. In addition, there are limited studies that investigated the effect of the piezoelectric actuator over mode-I active repair. In this study, the mode-I stress intensity factor for a plate with a center crack, and a bonded piezoelectric actuator was modeled using the linear elastic fracture mechanics. For this, an analytical closed-form solution is developed using the virtual crack closure technique taking into account mode-I as the only effective mode, coupling effects of the piezoelectric patch, and the singular stress at the crack tip. In addition, the total stress intensity factor was obtained by the superposition of the stress intensity factor obtained from the stresses produced by the piezoelectric actuators on the crack surfaces as the only external loads on the cracked plate and the stress intensity factor due to the far-field tension load. The proposed analytical model for mode-I stress intensity factor was verified by a finite element–based approach using ANSYS finite element software. The results demonstrated a good agreement between the analytical and finite element models with a relative error of less than 4% in all the cases studied. The results illustrated that the piezoelectric patch is efficient in reducing stress intensity factor when an extension mode of the actuator is applied. However, applying a contraction mode of the piezoelectric actuators produced negative strain which increased the stress intensity factor and thus the severity of the cracked structure and could lead to damage propagation.

A Novel Test Method to Measure the Fracture Toughness of Ceramic Balls Used in Bearings

2005 ◽  
Author(s):  
Michael O’Brien
Keyword(s):  
Fracture Toughness ◽  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Applied Load ◽  
Hoop Stress ◽  
Mechanical Test ◽  
Industrial Applications ◽  
Test Method ◽  
Finite Element Calculations

A novel mechanical test has been developed to measure the fracture toughness of the silicon-nitride balls used in modern hybrid bearings important for many defense, space and industrial applications. The ball is compressed diametrally between two hemispherical conforming dies, which causes the ball’s equator to bulge, generating a tensile hoop stress. Under applied load, a precrack placed at the equator grows. To calculate the ball’s fracture toughness at crack instability, finite element calculations of the applied stress field and an analytical solution for the stress intensity factor are used in the “two point plus semiellipse” method. The new technique appears more accurate than the indentation technique used to measure the toughness of ceramics.

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.

Stresses near narrow rectangular notches, with rounded corners, in beams in bending

1992 ◽  
Vol 27 (4) ◽  
pp. 227-234 ◽  
Author(s):  
T H Hyde ◽  
A Yaghi
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Analytical Solution ◽  
Shape Factor ◽  
Peak Stress ◽  
Notch Width ◽  
Finite Element Calculations ◽  
Tip Radius

The results of finite element calculations have been used to show that an analytical solution for the stresses in the vicinity of crack-like notches with elliptical and hyperbolic shaped ends gives accurate results for narrow, semi-circular ended notches. It is also shown that the peak stresses can be obtained from the stress intensity factor for an equivalent crack and the notch tip radius. Finite element solutions for narrow, rectangular notches with rounded corners, have also been used to show that the peak stresses in such notches can be obtained by using a notch shape factor to modify the peak stress values for semi-circular notches. The shape factor depends only on the notch width to corner radius ratio.

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.

Numerical and Experimental Analysis of Anisotropic Shrinkage during Sintering

2011 ◽  
Vol 233-235 ◽  
pp. 3068-3073
Author(s):  
Zhou Peng ◽  
Jian Zhong Xiao ◽  
Si Yang Mei ◽  
Shi Jun Huang
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
High Temperature ◽  
Green Body ◽  
Dimensional Changes ◽  
Finite Element Calculations ◽  
Powder Compacts ◽  
Modified Equation ◽  
Zirconium Powder ◽  
Good Agreement

With a view of simulating the dimensional changes during sintering of rectangle green bodies, the thermo-mechanical behavior of zirconium powder compacts at high temperature is investigated. In order to better describe the behavior of anisotropic shrinkage, the revised Master Sintering Curve is modified. Finite element calculations are then carried out on the green body according to the modified equation with the different shrinkages coefficients at the different stages of sintering. The possible causes of the anisotropic shrinkage are explained by macro-surface energy model. Numerical shape predictions have been compared with experimental data, which are considered to be in good agreement.

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