[PDF] Stress Intensity Factor Equations For Cracks In Three Dimensional Finite Bodies eBook

Author : JC. Newman
Publisher :
Page : 28 pages
File Size : 26,18 MB
Release : 1983
Category : Corner cracks
ISBN :

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This paper presents empirical stress-intensity factor equations for embedded elliptical cracks, semielliptical surface cracks, quarterelliptical corner cracks, semielliptical surface cracks at a hole, and quarterelliptical corner cracks at a hole in finite plates subjected to remote tensile loading. These equations give stress-intensity factors as a function of parametric angle, crack depth, crack length, plate thickness, and, where applicable, hole radius. The stress-intensity factors used to develop the equations were obtained from current and previous three-dimensional finite-element analyses of these crack configurations. A wide range of configuration parameters was included in the equations. The ratio of crack depth to plate thickness ranged from 0 to 1, the ratio of crack depth to crack length ranged from 0.2 to 2, and the ratio of hole radius to plate thickness ranged from 0.5 to 2. The effects of plate width on stress-intensity variations along the crack front also were included, but generally were based on engineering estimates. For all combinations of parameters investigated, the empirical equations were generally within 5 percent of the finite-element results, except within a thin "boundary layer" where the crack front intersects a free surface. However, the proposed equations are expected to give a good estimate in this region because of a study made on the boundary-layer effect. These equations should be useful for correlating and predicting fatigue crack growth rates as well as in computing fracture toughness and fracture loads for these types of crack configurations.

Author : George C. Sih
Publisher : Springer Science & Business Media
Page : 344 pages
File Size : 50,84 MB
Release : 2012-12-06
Category : Science
ISBN : 940101292X

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This third volume of a series on Mechanies of Fraeture deals with eraeks in plates and shelIs. It was noted in Volume 2 on three-dimensional eraek problems that additional free surfaees can lead to substantial mathematical complexities, often making the analysis unmanageable. The theory of plates and shelIs forms a part of the theory of elasticity in which eertain physieal assumptions are made on the basis that the distanee between two bounded surfaees, either fiat or eurved, is small in eomparison with the overall dimen sions of the body. In modern times, the broad and frequent applieations of plate- and shell-like struetural members have aeted as a stimulus to whieh engineers and researchers in the field of fracture meehanies have responded with a wide variety of solutions of teehnieal importanee. These eontributions are covered in this book so that the reader may gain an understanding of how analytieal treat me nt s ofplates and shells containing initial imperfeetions in the form of eraeks are earried out. The development of plate and shell theories has involved long standing controversy on the eonsisteney of omitting eertain small terms and at the same time retaining others of the same order of magnitude. This defieieney depends on the ratio of the plate or shell thiekness, h, to other eharaeteristie dimensions and eannot be eompletely resolved in view of the approximations inherent in the transverse dependence of the extensional and bending stresses.

Author : National Aeronautics and Space Administration (NASA)
Publisher : Createspace Independent Publishing Platform
Page : 34 pages
File Size : 32,83 MB
Release : 2018-06-28
Category :
ISBN : 9781722025823

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A re-evaluation of the 3-D finite-element models and methods used to analyze surface crack at stress concentrations is presented. Previous finite-element models used by Raju and Newman for surface and corner cracks at holes were shown to have ill-shaped elements at the intersection of the hole and crack boundaries. These ill-shaped elements tended to make the model too stiff and, hence, gave lower stress-intensity factors near the hole-crack intersection than models without these elements. Improved models, without these ill-shaped elements, were developed for a surface crack at a circular hole and at a semi-circular edge notch. Stress-intensity factors were calculated by both the nodal-force and virtual-crack-closure methods. Both methods and different models gave essentially the same results. Comparisons made between the previously developed stress-intensity factor equations and the results from the improved models agreed well except for configurations with large notch-radii-to-plate-thickness ratios. Stress-intensity factors for a semi-elliptical surface crack located at the center of a semi-circular edge notch in a plate subjected to remote tensile loadings were calculated using the improved models. The ratio of crack depth to crack length ranged form 0.4 to 2; the ratio of crack depth to plate thickness ranged from 0.2 to 0.8; and the ratio of notch radius to the plate thickness ranged from 1 to 3. The models had about 15,000 degrees-of-freedom. Stress-intensity factors were calculated by using the nodal-force method. Tan, P. W. and Raju, I. S. and Shivakumar, K. N. and Newman, J. C., Jr. Langley Research Center RTOP 505-63-01-05...

Author : Walter G. Reuter
Publisher : ASTM International
Page : 428 pages
File Size : 48,55 MB
Release : 1990
Category : Fracture mechanics
ISBN : 080311284X

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From the symposium (on title) held in Sparks, Nevada, April 1988. Twenty-two peer-reviewed papers are divided into sections on models and experiments (monotonic loading), and fatigue crack growth. Areas addressed include the differences in constraint for 2-D through-thickness cracks and 3-D surface