Download or read book An Analytical Investigation of Plasticity Induced Closure Involving Short Cracks written by E. Bednarz and published by . This book was released on 1988 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt: Plasticity induced crack closure and its effect on the fatigue growth of short cracks is investigated numerically. A plane stress finite-element analysis is used to simulate a nonpropagating crack of length 65 ?m in a single-edge-cracked specimen under two stress levels and two values of stress ratio R. A comparison of results is then made with a propagating crack of an initial length of 25 ?m, which is allowed to grow to a final length of 65 ?m. R values of 0.1 and -1.0 with stress levels of 60 and 90% of the yield stress for the material are considered. The plastic zone size for each case studied is approximately equal to the initial crack length, which provides conditions characteristic of short cracks.
Download or read book A Numerical Study of Plasticity Induced Closure in Short Cracks by the Finite Element Method written by Eugene J. Bednarz and published by . This book was released on 1990 with total page 186 pages. Available in PDF, EPUB and Kindle. Book excerpt: Plasticity induced closure and its effect on the fatigue growth of short cracks were investigated analytically in a high strength titanium alloy at room temperature as well as in a nickel base alloy at elevated temperature. The analysis consisted of subjecting a single-edge cracked specimen with an initial crack length of .001 inch to cyclic loading and allowing the crack to propagate. This was accomplished using a two-dimensional finite element code and a theoretical finite element model of a typical test geometry. Visco II, the two-dimensional plane stress/plane strain finite element code, uses constant strain triangular elements and incorporates the Bodner-Partom Viscoplastic Flow Law to handle non-linear material behavior. The numerical simulations involved subjecting specimens of TI-6246 at room temperature (time-independent behavior) to cyclic loads with maximum nominal stress values of approximately 60 and 90 percent of the material yield strength and load ratios of -1.0 and 0.1 with a frequency of 1.0 Hz. The numerical simulations of specimens consisting of Inconel 718 at 1200 F (time-dependent behavior) consisted of cyclic loads where the maximum nominal stress was .90 yield strength, the applied load ratio was 0.1, and the cyclic frequencies were .01 and 1.0 Hz. The formation of a plastic wake and the affects of plasticity induced closure were observed in these specimens. (AW).
Download or read book Mechanics of Fatigue Crack Closure written by Wolf Elber and published by ASTM International. This book was released on 1988 with total page 671 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Effects of Slip Character and Crack Closure on the Growth of Small Fatigue Cracks in Titanium aluminium Alloys written by James M. Larsen and published by . This book was released on 1990 with total page 286 pages. Available in PDF, EPUB and Kindle. Book excerpt: An investigation was performed to study the effects of slip character and crack closure on the propagation of small fatigue cracks in titanium- aluminum alloys. The materials examined were solution-treated Ti-4Al and Ti-8Al, as well as aged Ti-8Al. The propagation of naturally initiated surface cracks of depths as small as 25 micrometers was compared with the behavior of large through-thickness cracks. An extensometer was used to monitor crack closure throughout the large crack tests, and the closure behavior of the small cracks was measured using a computerized laser interferometric displacement gage having a displacement resolution of 0.01 micrometer. The measurements of crack closure were used to compute an effective stress intensity factor range. In all three alloys and for all test conditions, which included a range of stress levels and stress ratios, small cracks propagated faster than large cracks subjected to an equivalent Delta K, and the small cracks propagated under conditions that were significantly below the large-crack threshold, Delta K(th). Although the character and distribution of slip in Ti-Al alloys may have a dramatic influence on fatigue crack initiation and on the propagation of large cracks, this effect was minimal for small cracks.
Download or read book An Analytical Model which Combines Roughness and Plasticity Induced Fatigue Crack Closure written by Nong Chen and published by . This book was released on 1997 with total page 242 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Evaluation of the Plasticity Induced Crack Closure Concept and Measurement Methods written by James C. Newman (Jr.) and published by . This book was released on 1998 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Analytical and Experimental Study of Near Threshold Interactions Between Crack Closure Mechanisms written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-20 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt: The results of an analytical closure model that considers contributions and interactions between plasticity-, roughness-, and oxide-induced crack closure mechanisms are presented and compared with experimental data. The analytical model is shown to provide a good description of the combined influences of crack roughness, oxide debris, and plasticity in the near-threshold regime. Furthermore, analytical results indicate that closure mechanisms interact in a non-linear manner such that the total amount of closure is not the sum of closure contributions for each mechanism. Newman, John A. and Riddell, William T. and Piascik, Robert S. Langley Research Center NASA/TM-2003-211755, NAS 1.15:211755, L-18207, ARL-TR-2774
Download or read book Fatigue Crack Propagation in Metals and Alloys written by Ulrich Krupp and published by John Wiley & Sons. This book was released on 2007-04-09 with total page 312 pages. Available in PDF, EPUB and Kindle. Book excerpt: This comprehensive overview of the whole field of fatigue and fracture of metallic materials covers both the theoretical background and some of the latest experimental techniques. It provides a summary of the complex interactions between material microstructure and cracks, classifying them with respect to the overall damage process with a focus on microstructurally short cracks and dynamic embrittlement. It furthermore introduces new concepts for the numerical treatment of fatigue microcrack propagation and their implementation in fatigue-life prediction models.This comprehensive overview of the whole field of fatigue and fracture of metallic materials covers both the theoretical background and the latest experimental techniques. It provides a summary of the complex interactions between material microstructure and cracks, classifying them with respect to the overall damage process. It furthermore introduces new concepts for the numerical treatment of fatigue microcrack propagation and their implementation in fatigue-life prediction models.
Download or read book Fracture Mechanics written by and published by ASTM International. This book was released on 1989 with total page 685 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Advanced Methods of Fatigue Assessment written by Dieter Radaj and published by Springer Science & Business Media. This book was released on 2013-05-13 with total page 507 pages. Available in PDF, EPUB and Kindle. Book excerpt: In five chapters, this volume presents recent developments in fatigue assessment. In the first chapter, a generalized Neuber concept of fictitious notch rounding is presented where the microstructural support factors depend on the notch opening angle besides the loading mode. The second chapter specifies the notch stress factor including the strain energy density and J-integral concept while the SED approach is applied to common fillet welded joints and to thin-sheet lap welded joints in the third chapter. The forth chapter analyses elastic-plastic deformations in the near crack tip zone and discusses driving force parameters. The last chapter discusses thermomechanical fatigue, stress, and strain ranges.
Download or read book Analytical and Experimental Study of Near Threshold Interactions Between Crack Closure Mechanisms written by John A. Newman and published by . This book was released on 2003 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Analysis of Crack Closure Under Plane Strain Conditions written by NA. Fleck and published by . This book was released on 1988 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt: An elastic-perfectly plastic finite-element analysis has been conducted of plasticity-induced crack closure under plane strain conditions. At a load ratio R ( = Kmin/Kmax) of zero, crack closure was observed in a center-cracked panel but not in a bend specimen. Crack closure in the center-cracked panel occurred for a transient period of growth as the crack evolved from the state of a stationary crack to the steady state of a growing fatigue crack. The influence of specimen geometry upon closure response was rationalized in terms of the "T-stress." This stress is the nonsingular constant second term in the near tip series expansion of the normal stress parallel to the crack plane. No closure was observed in the center-cracked panel for R ? 0.3. The crack opening response and plastic zone distribution of a growing fatigue crack were compared with those of a cyclically loaded stationary crack and a statically loaded tearing crack. Some of the features of the solution for the growing fatigue crack were similar to the solution for a stationary crack, while other features bore more resemblance to those of a tearing crack.
Download or read book International Aerospace Abstracts written by and published by . This book was released on 1992 with total page 1046 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Naval Research Reviews written by and published by . This book was released on 1998 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Innovative Approaches to Irradiation Damage and Fracture Analysis written by D. L. Marriott and published by . This book was released on 1989 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Evaluation of the Plasticity induced Crack closure Concept and Measurement Methods written by J. C. Newman and published by . This book was released on 1998 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: An assessment of the plasticity-induced crack-closure concept is made, in light of the questions that have been raised on the validity of the concept, and the assumptions that have been made concerning crack-tip damage below the crack-opening stress. The impact of using other crack-tip parameters, such as the cyclic crack-tip displacement, to model crack-growth rate behavior was studied. Crack-growth simulations, using a crack-closure model, showed a close relation between traditional [delta]K[sub eff] and the cyclic crack-tip displacement ([delta][Dirac delta function][sub eff]) for an aluminium alloy and a steel. Evaluations of the cyclic hysteresis energy demonstrated that the cyclic plastic damage below the crack-opening stress was negligible in the Paris crack-growth regime. Some of the standard and newly proposed remote measurement methods to determine the "effective" crack-tip driving parameter were evaluated on middle-crack tension specimens. A potential source of the K[sub max] effect on crack-growth rates was studied on an aluminum alloy. Results showed that the ratio of K[sub max] to K[sub c] had a strong effect on crack-growth rates at high stress ratios and at low stress ratios for very high stress levels. The crack-closure concept and the traditional crack-growth rate equations were able to correlate and predict crack-growth rates under these extreme conditions.
Download or read book Small Fatigue Cracks written by K.S. Ravichandran and published by Elsevier. This book was released on 1999-09-30 with total page 511 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book contains the fully peer-reviewed papers presented at the Third Engineering Foundation Conference on Small Fatigue Cracks, held under the chairmanship of K.S. Ravichandran and Y. Murakami during December 6-11, 1998, at the Turtle Bay Hilton, Oahu, Hawaii. This book presents a state-of-the-art description of the mechanics, mechanisms and applications of small fatigue cracks by most of the world's leading experts in this field. Topics ranging from the mechanisms of crack initiation, small crack behavior in metallic, intermetallic, ceramic and composite materials, experimental measurement, mechanistic and theoretical models, to the role of small cracks in fretting fatigue and the application of small crack results to the aging aircraft and high-cycle fatigue problems, are covered.
