Download or read book Variations in Stress Intensity Factor Across Curved Crack Fronts in Fracture Mechanics Test Specimens written by A. P. Smith and published by . This book was released on 1984 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Numerical modelling of the effect of fatigue crack front curvature on the distribution of the mode I stress intensity factor at different positions across the specimen thickness is described.
Download or read book Effect of Crack Front Curvature on Experimental Evaluation of J Integral for Single Edge Bend Specimens written by Zijian Yan and published by . This book was released on 2014 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper presents three-dimensional (3D) finite element analyses of plane-sided single-edge bend specimens to investigate the effect of the crack front curvature on the accuracy of the average J-integral (J) evaluated over the crack front using the plastic eta-factor-based approach specified in ASTM E1820-11. Specimens with average crack lengths of 0.3, 0.5, and 0.7 and thickness-to-width ratios of 1, 0.5, and 0.25 were analyzed. The analysis was based on the J2 deformation theory of plasticity and assumed stationary cracks with sharp crack tips. The curved crack front was characterized by a power-law expression proposed by Nikishikov et al. that was validated using crack front data collected in this study. The plastic eta factors specified in ASTM E1820-11 and proposed by Zhu et al. were employed. The analysis results indicate that the errors in the plastic eta-factor-based J were generally between -7 % (i.e., underestimation) and 6 % (i.e., overestimation) for the specimens that had curved crack fronts with crack front curvature equal to the maximum allowable value specified in ASTM E1820-11. Based on the analysis results, crack front straightness criteria that are in most cases less stringent than those specified in ASTM E1820-11 are recommended. The suggested criteria could potentially lead to reduced specimen rejection rates and cost savings.
Download or read book Effect of Crack Front Curvature and Side Grooving on CTOD 5 and J Integral in CT and 3PB Specimens written by GP. Nikishkov and published by . This book was released on 1999 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fracture testing on compact tension (CT) and threepoint bend (3PB) specimens is preceded by fatigue precracking. Fatigue cracks have curved crack fronts. Nevertheless, crack front curvature is not taken into account in numerical modeling of fracture toughness testing procedures. In this paper we analyze actual fatigue cracks in CT specimens and show that the difference between crack depth at the center plane and at the surface of specimens is typically 0.01 to 0.03 of the specimen width. Three-dimensional elastic-plastic finite element analyses were performed for CT and 3PB specimens with crack fronts of different curvatures, and the CTOD ?5 and the J-integral were determined. It is found that the ratio ?5C/?5 is sensitive to the crack front curvature and strongly affected by side grooves. It is also shown that crack front curvature variations that are within the limits given by the test standards affect to a certain extent the ? factor employed for the determination of the experimental value of the J-integral using the area under the force versus load-point displacement record. These facts should be kept in mind when toughness is measured.
Download or read book Stress Singularity for a Crack with an Arbitrarily Curved Front written by R. J. Hartranft and published by . This book was released on 1976 with total page 45 pages. Available in PDF, EPUB and Kindle. Book excerpt: To investigate the possibility of a point of a crack front propagating in a direction not in the normal plane of the crack front, the three-dimensional form of the crack front stress field is obtained. To simplify comparisons of the states of stress at various points lying on a spherical surface centered at a point of the crack front, a local spherical coordinate system is used. It is found that the crack propagation will be from each point of the crack front in a direction lying in the normal plane. The results are used in conjunction with the strain energy density fracture criterion for the problem of an elliptical crack. The plane of the flat elliptical crack makes an arbitrary angle with the field of uniform applied tensile stress. Crack growth directions for various positoins along the crack front are determined, and loads required for fracture for various angles are obtained. (Author).
Download or read book Stress intensity Factor Equations for Cracks in Three dimensional Finite Bodies Subjected to Tension and Bending Loads written by J. C. Newman and published by . This book was released on 1984 with total page 98 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Stress Intensity Factors Associated with Curved Crack Fronts in a Compact Tension Specimen written by B. K. Neale and published by . This book was released on 1977 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fatigue Crack Front Shape and Its Effect on Fracture Toughness Measurements written by OL. Towers and published by . This book was released on 1983 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: The shapes of fatigue cracks in fracture toughness test specimens have been reviewed for a sample of approximately 680 three-point bend specimens. Up to 17% of this sample would be rejected for plane strain fracture toughness for Mode I loading KIc test procedures because of fatigue crack front shape. The corresponding rejection rate to crack tip opening displacement (CTOD) procedures is 3%. The results of published work for aluminum alloys indicate that relaxation of the KIc testing standards' restrictions on shape would not cause undue errors. This indication, however, appears to conflict with a computer model of curved crack fronts in a compact tension specimen. The suggestion is therefore made that the calculation procedures for fracture toughness determinations should be made more appropriate to the curved crack fronts usually observed, before the limits quoted in the standards are relaxed. To reduce the number of crack length measurements the removal of one limit on crack front shape is suggested. Finally, experimental justification for the change from the limits on crack front shape of British Standard Draft for Development DD19 [1972]) to those of the current CTOD testing standard, British Standard Methods for Crack Opening Displacement (COD) Testing BS 5762 (1979), is presented.
Download or read book Fracture Mechanics written by Fazil Erdogan and published by ASTM International. This book was released on 1995 with total page 716 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Toward Assessing the Effects of Crack Front Curvature CFC written by JL. Swedlow and published by . This book was released on 1972 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: Crack front curvature (CFC) is shown to affect the K calibration of four special geometries for which analysis is currently practicable. The inference is drawn that assuming straight crack fronts in, say, test specimens having non-zero CFC may be non-conservative; the aim of this paper is to initiate further investigation of the effects of CFC.
Download or read book New Contributions to R curves and Bridging Stresses Applications of Weight Functions written by Theo Fett and published by KIT Scientific Publishing. This book was released on 2014-07-31 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt: Most ceramics show an increase of the crack growth resistance during crack propagation (R-curve behaviour). Reasons for such behaviour are bridging effects between opposite crack surfaces, phase transformations around the tip of a crack, and development of micro-cracking zones.This booklet predominantly deals with the bridging behaviour and the discussion of the observed effects in terms of the fracture mechanics weight function procedure.
Download or read book Cracks and Fracture written by and published by ASTM International. This book was released on 1976 with total page 594 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Photoelastic Investigation of the Effect of Crack Front Curvature on the Stress Intensity Factor Distribution in a Single Edge Notch Specimen written by John J. McGowan and published by . This book was released on 1979 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Influence of Irregularities in the Crack Shape on the Crack Extension Measurement by Means of the Direct Current Potential Drop Method written by FO. Riemelmoser and published by . This book was released on 1999 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: The equations used for calculating the crack extension from the change in the potential drop at a fracture mechanics specimen are generally derived for perfectly straight crack fronts. In the practice of fracture mechanics tests the crack, however, usually grows faster in the interior of the specimen than at the exterior, leading to a curved crack front. For such a case we calculate the potential drop by means of a finite difference scheme. It is shown that for curved cracks the usual procedure of the direct-current-potential-drop method underestimates the real crack extension. The same finite difference scheme is then used to account for conductive bars and bridges, which sometimes are left behind the crack front. Finally, the influence of side grooves on the potential drop is investigated.
Download or read book Stress Analysis and Growth of Cracks written by and published by ASTM International. This book was released on 1972 with total page 315 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Interface Fracture and Delaminations in Composite Materials written by Leslie Banks-Sills and published by Springer. This book was released on 2017-07-05 with total page 125 pages. Available in PDF, EPUB and Kindle. Book excerpt: Part I of this SpringerBrief presents the problem of a crack between two dissimilar isotropic materials and describes the mathematical background. A fracture criterion is discussed and Methods for calculating fracture parameters such as stress intensity factors using the finite element method and three post-processors are considered. Actual test data and both deterministic and statistical failure curves are presented.In Part II of the book, similar descriptions are given for delaminations in composite laminates. The mathematical treatment of this type of damage including the first term of the asymptotic expansion of the stress and displacement fields is considered. Numerical post-processors for determining stress intensity factors for these cases are reviewed. Two examples of specific laminates are presented: one with a failure curve and the other with a failure surface. Finally, beam specimens used for testing such failures are discussed.
Download or read book Fast Fracture and Crack Arrest written by Gary T. Hahn and published by ASTM International. This book was released on 1977 with total page 438 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Tensile Fracturing in Rocks written by Dov Bahat and published by Springer Science & Business Media. This book was released on 2005-08-31 with total page 581 pages. Available in PDF, EPUB and Kindle. Book excerpt: ‘Tensile Fracturing in Rocks’ presents field observations on fracturing of sedim- tary rocks and granite outcrops from various provinces in three continents. It also combines results of recent experiments conducted at different laboratories around the world with current theories on fracturing. In treating faults, this book limits itself to faults that are associated with joint sets produced by definable causes and occasi- ally to cases where interaction between the two types of fracture – faults and joints – is not clear. The book’s subject matter is divided over six chapters, which are briefly described below. Chapter 1 summarizes current key concepts in fracture physics. It starts with a pr- entation of the elastic theory of fracture, and concentrates on the results of linear el- tic fracture mechanics. The chapter touches also upon other fracture properties, e.g., crack nucleation, dynamic fracturing and slow fracturing processes. Nucleation is - dressed by statistical mechanics methods incorporating modern approaches of th- mal and fiber bundle processes. The analyses of dynamic fracturing and slow fract- ing focus on the differences, as compared to the linear elastic approach. The cont- versy in interpreting experimental dynamic results is highlighted, as are the surface morphology patterns that emerge in fracturing and the non-Griffith crack extension criterion in very slow fracturing processes.
