Download or read book An Experimental Study of Fatigue Crack Retardation Under Tensile and Compressive Loading in Polymethylmethacrylate written by Kurt Charles Schulz and published by . This book was released on 1986 with total page 550 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Experimental Study of Fatigue Crack Propagation and Retardation Using Polymethylmethacrylate written by Francis J. Pitoniak and published by . This book was released on 1972 with total page 88 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fatigue cracks were grown in compact tension specimens of polymethylmethacrylate, a transparent polymer which was used as a model for metals. Various peak overloads applied to the constant DeltaK baselines used produced changes in the baseline load crack growth rates. A study of the monochromatic light interference fringe patterns emanating from the fatigue cracks at zero load indicated that the crack surface were closed along the saw cut edge and on the free surface of the specimens. The crack surfaces were displaced in the interior of the specimen at zero load. Measurement of the crack opening displacements from the fringe patterns indicated that the crack surfaces opened on the free surface at approximately half the baseline load level for a stress ratio of approximately zero. This is in agreement with the Elber crack closure concept.

Download or read book Experimental Study of Fatigue Crack Propagation and Retardation Using Polymethylmethacrylate written by Francis J. Pitoniak (CAPT, USAF.) and published by . This book was released on 1972 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fatigue Crack Retardation and Closure in Polymethylmethacrylate written by F. J. PITONIAK and published by . This book was released on 1973 with total page 1 pages. Available in PDF, EPUB and Kindle. Book excerpt: RESULTS ARE PRESENTED FROM AN INVESTIGATION OF CRACK SURFACE PROFILES AND THE INFLUENCE OF INTERMITTENT OVERLOADS ON FATIGUE CRACK GROWTH IN POLYMETHYLMETHACRYLATE, A TRANSPARENT POLYMER. FATIGUE CRACKS WERE GROWN IN COMPACT TENSION SPECIMENS UNDER CONDITIONS OF CONSTANT RANGE IN STRESS INTENSITY FACTOR. TENSILE OVERLOADS WERE FOUND TO PRODUCE CHANGES IN THE SUBSEQUENT CRACK GROWTH SIMILAR TO THOSE OBSERVED IN METALS. THE FATIGUE CRACK GROWTH RATE IN POLYMETHYLMETHACRYLATE MAY BE RETARDED BY APPLICATION OF TENSILE OVERLOADS. EXAMINATION OF MONOCHROMATIC LIGHT INTERFERENCE FRINGE PATTERNS EMANATING FROM THE FATIGUE CRACKS AT ZERO LOAD INDICATE THAT THE CRACK PERIMETER WAS CLOSED AT ZERO LOAD. THE CRACK SURFACES WERE DISPLACED, HOWEVER, IN THE INTERIOR OF THE SPECIMEN AT ZERO LOAD. MEASUREMENTS OF THE CRACK OPENING DISPLACEMENTS DURING LOADING REVEALED THAT SIGNIFICANT TENSILE LOAD WAS REQUIRED TO DISPLACE THE PORTIONS OF THE CRACK SURFACES WHICH WERE INITIALLY CLOSED. THESE OBSERVATIONS ARE DISCUSSED IN LIGHT OF THE ELBER CONCEPT OF CRACK CLOSURE.

Download or read book Masters Theses in the Pure and Applied Sciences written by Wade H. Shafer and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 386 pages. Available in PDF, EPUB and Kindle. Book excerpt: Masters Theses in the Pure and Applied Sciences was first conceived, published, and disseminated by the Center for Information and Numerical Data Analysis and Synthesis (CINDAS) * at Purdue University in 1957, starting its coverage of theses with the academic year 1955. Beginning with Volume 13, the printing and dissemination phases of the activity were transferred to University Microfilms/Xerox of Ann Arbor, Michigan, with the thougtit that such an arrangement would be more beneficial to the academic and general scientific and technical community. After five years of this joint undertaking we had concluded that it was in the interest of all con cerned if the printing and distribution of the volumes were handled by an interna tional publishing house to assure improved service and broader dissemination. Hence, starting with Volume 18, Masters Theses in the Pure and Applied Sciences has been disseminated on a worldwide basis by Plenum Publishing Cor poration of New York, and in the same year the coverage was broadened to include Canadian universities. All back issues can also be ordered from Plenum. We have reported in Volume 31 (thesis year 1986) a total of 11 ,480 theses titles trom 24 Canadian and 182 United States universities. We are sure that this broader base tor these titles reported will greatly enhance the value ot this important annual reterence work. While Volume 31 reports theses submitted in 1986, on occasion, certain univer sities do re port theses submitted in previousyears but not reported at the time.

Download or read book Fatigue 87 written by Robert O. Ritchie and published by . This book was released on 1987 with total page 744 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fatigue Crack Growth and Life Predictions in Man Ten Steel Subjected to Single and Intermittent Tensile Overloads written by GO. Njus and published by . This book was released on 1977 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fatigue crack growth behavior was investigated in Man-Ten steel under conditions of constant load amplitude, single tensile overloads followed by constant load amplitude and intermittent single tensile overloads. Constant-amplitude ratios, Rl = Plmin / Plmax, were + 1/2, 0, -1/2, -1 and -2. The single overload test program excluded Rl = +1/2, and the intermittent overload program was for Rl = 0 only. A new simplified mathematical model was introduced which assumes that fatigue crack growth retardation is primarily a function of the overload ratio and the load ratio. The model predicted intermittent tensile overload life within 57 to 112 percent of the experimental life. The average prediction was 77 percent of experimental life. For Man-Ten steel, constant-amplitude crack growth rate versus positive ?? fell within a reasonable scatter band for Rl = 1/2 to -1. However, substantial decrease in life occurred with Rl = -2. Negative values of Rl following a single tensile overload substantially reduced retardation life. Thus compressive stress, either large or small, cannot be neglected in spectrum loading fatigue crack growth life predictions.

Download or read book Prediction of Fatigue Crack Growth Retardation Due to a Tensile Overload Using Two parameter delta K Kmax Approach written by Wataru Tsutsui and published by . This book was released on 2008 with total page 412 pages. Available in PDF, EPUB and Kindle. Book excerpt: A theoretical crack growth study on powder metallurgy aluminum alloys AA5091 and AA8022 was conducted. Specifically, the research focused on the crack growth retardation due to the application of a tensile overload. The tensile overload creates a plastic zone ahead of the propagating crack tip that induces the compressive residual stress after unloading. Such compressive residual stress pushes the crack tip faces against each other, which results in crack growth retardation. In the study, stimulation started from the calculation of the compressive residual stress. The details of the calculation steps are explained in the thesis. Eventually, the stress intensity factor range at the crack tip ([delta]Ktip) and the maximum stress intensity factor at the crack tip (Kmax tip) were calculated. These two parameters, along with constants C, m, and p, were used to simulate the crack growth rate. Within the scope of the two-parameter ([delta]K, Kmax) approach, seven different calculation methods were investigated. The crack growth rate from each method was compared against experimental results from open literature. Finally, the best method among seven was determined.

Download or read book Fatigue Crack Growth in Complex written by Amir Ebrahim Chahardehi and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Fatigue crack growth has been traditionally modelled using LEFM through the use ofthe Paris law. This requires an accurate method for stress intensity factor (K)calculation. Weight functions have been developed for one-dimensional cracks (e.g.edge and through cracks); these are functions that enable separation of the loading andgeometry and considering the effect of each one of these two factors on the stressintensity factor (SIF) separately. They have been proven to be useful for arbitrary stressdistributions where an accurate empirical formula for the stress intensity factor does notexist. Such cases include residual stress fields due to surface treatments or welds. However, in the case of surface cracks, or part-through cracks, the problem ofmodelling the growth of these cracks poses two main questions, namely, how should theParis law be generalised to suit the two-dimensional scenario, and under arbitraryloadings, how can the SIFs be calculated for these cracks. Current solutions involvetedious mathematical calculations and are complicated functions. In this thesis, the concept of root mean square (RMS) SIF is examined and by drawingmathematical analogy with the one-dimensional case, a novel weight function is derivedwhich enables calculation of RMS SIF values for a range of semi-elliptical surfacecracks under arbitrary loadings. The accuracy of the weight function is verified throughcomparisons with finite elements results for a variety of loadings/geometries. Thesimplicity of the weight function construction method makes it a useful tool for fatiguelife predictions where incremental recalculations of SIF is required as the crack grows. Surface treatments such as shot peening and laser peening are used for crack growthretardation. It is generally believed that it is through the introduction of what is termed?beneficiary compressive residual stresses? that crack retardation occurs. Thecompressive residual stresses are superimposed on the?detrimental tensile stresses? dueto loading and hence lead to a lower SIF level. By having such a strong tool as weightfunctions, this general belief can be put to test. To this end, a set of experiments werecarried out to study the behaviour of cracks in residual stress fields arising from laserpeening. Edge cracks were grown in partially-peened specimens. Neutron diffractionstress measurements were taken and stress profiles were obtained for these specimens. Measurements of strain fields near the crack show the interaction between the crack andthe stress field induced by the peening process. The effect of laser peening on crackgrowth is discussed and recommendations for future work are proposed. Overall the thesis proposes a weight function for surface cracks the uniqueness of whichis in its simplicity, and develops an understanding of the nature of induced and transientstresses in laser-peened components. The concept of?effective fatigue stress? isintroduced and its calculation is described, and conclusions are drawn from the nature ofthis stress distribution.

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1973 with total page 1102 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Effects of Rest Time on Fatigue Crack Retardation and Observations of Crack Closure written by William N Sharpe (Jr) and published by . This book was released on 1975 with total page 33 pages. Available in PDF, EPUB and Kindle. Book excerpt: The report examines two variables which could influence fatigue crack retardation: rest periods and specimen thickness. A series of experiments are described in which a tensile overload was applied and the specimen allowed to rest at zero load prior to resuming the original cyclic loading. Since the size of the plastic zone is larger for conditions of plane stress than for plane strain, these tests were repeated for several specimen thicknesses.

Download or read book The Study of Crack Closure Phenomenon Following One Tensile Overload written by Yinan Sun and published by . This book was released on 2007 with total page 183 pages. Available in PDF, EPUB and Kindle. Book excerpt: During the load-controlled high-cycle fatigue test, when the overload was applied, it is shown that from the crack-growth rate (da/dN) versus stress-intensity-factor range ([Delta Kappa]) curve, the crack-growth rate decreased, following the overload, which indicated the crack-closure phenomenon. The crack-growth-retardation period was observed after the overload. The goal of this study is to investigate the deformation evolution during tensile loading and unloading cycles using neutron diffraction. Neutron diffraction is used to investigate the crack-closure phenomenon by measuring the changes in the elastic-lattice-strain profiles around the fatigue-crack tip in a compact-tension (CT) specimen during tensile loading and unloading cycles. Spatially-resolved-strain measurements were performed to determine the in-plane and through-thickness lattice-strain profiles ahead of the crack tip under a constant tensile load. The strain scanning was repeated under various applied loads ranging from 667 to 6,667 N. Subsequently, an overload at 8,889N was applied. The strain scans repeated. After the overload, large compressive strain fields were observed close to the crack tip, indicative of the crack-closure phenomena. Residual strain/stress mapping using neutron diffraction was also designed to investigate the mechanism of the retardation phenomenon by mapping the changes in the lattice-strain profiles around the fatigue-crack tip in a series of compact-tension (CT) specimens, which were fatigued to various stages through the retardation period after the overload. Following the overload, compressive-strain fields were observed along the loading direction close to the crack tip. As the crack grows out of the retardation period, the residual compressive strains decreased. The results provide a microscopic understanding of the overload effect during cyclic loading. The plastic deformation ahead of a fatigue-crack tip was measured from the diffraction-peak-width changes. The dislocation density was estimated from the fullwidth- half maximum (FWHM) of the diffraction peaks. High dislocation densities around the crack tip were observed after the overload. Furthermore, the plastic-zone size in front of the crack tip was estimated from the diffraction-peak broadening, which showed a good agreement with the calculated result. The plasticity-induced crack-closure phenomenon after an overload was observed. The measured elastic strains and dislocation densities will be compared to the finite-element simulations that are based on an irreversible, hysteretic-cohesive interface model. The experimental and numerical results will be compared and discussed. The deformation in the vicinity of the crack tip was not only studied with the neutron diffraction, but also the x-ray microbeam diffraction. The results help understand the overload effect, which induced a large plastic deformation causing dislocations inhomogeneously arranged around the crack tip. From neutron-diffraction measurements, the anisotropic line broadening was observed in front of the crack tip. Furthermore, Laue patterns, obtained from the microbeam diffraction at different locations near the crack, provide a better spatial resolution and show alternating regions with high and low dislocation densities. Overall, the dislocation density was found to decrease with the distance from the crack tip.

Download or read book International Aerospace Abstracts written by and published by . This book was released on 1993 with total page 1146 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Japanese Science and Technology written by and published by . This book was released on 1986 with total page 724 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Japanese Science and Technology 1983 1984 written by United States. National Aeronautics and Space Administration. Scientific and Technical Information Branch and published by . This book was released on 1985 with total page 1080 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Applied mechanics reviews written by and published by . This book was released on 1948 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Engineered Materials Abstracts written by and published by . This book was released on 1995-10 with total page 496 pages. Available in PDF, EPUB and Kindle. Book excerpt: