Download or read book Crack Closure Behavior on a Variety of Materials Under High Stress Ratios and Kmax Test Conditions written by Y. Yamada and published by . This book was released on 2012 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fatigue-crack-growth-rate tests on compact specimens have been made on a variety of materials (2024-T3, 2324-T39, 7050-T7451, 4340 steel, and Inconel-718) over a wide range in stress ratios from 0.1 to 0.9 (and 0.95 in some cases) and several Kmax test conditions. Test data has been generated from threshold to near fracture using the compression precracking constant amplitude or compression precracking load reduction test methods in the threshold regime; and constant-amplitude loading at higher rates. A remote back-face strain (BFS) gage was used to monitor crack growth and to measure crack-opening loads. Local strain gages were also placed along and slightly off (about one-half thickness) the anticipated crack path to measure crack-opening loads. Elber's load-against-reduced-strain method was used to determine crack-opening loads by means of visual inspection (equivalent to a 0 % compliance offset). For a particular material, the BFS and local strain gages produced essentially the same crack-opening loads at low stress ratio (R = 0.1) conditions. But at high stress ratios (R >= 0.7) and Kmax test conditions, the local gages produced significantly higher crack-opening loads than the BFS gage in the threshold and near-threshold regimes. Previous research had proposed that high stress ratios (R >= 0.7) and Kmax test conditions produce closure-free conditions based on crack-mouth-opening-displacement or BFS gages, and plasticity-induced crack-closure modeling. However, crack closure under high stress ratios (R >= 0.7) and Kmax test conditions is attributed to residual-plastic deformations, crack-surface roughness, and/or fretting-debris. From local crack-opening load measurements, the effective stress-intensity-factor range (DKeff) appears to be uniquely related to the crack-growth rate in the threshold and near-threshold regimes.
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 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 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 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 Advances in Fatigue Crack Closure Measurement and Analysis written by R. Craig McClung and published by ASTM International. This book was released on 1999 with total page 487 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Surface crack Growth written by Walter G. Reuter and published by ASTM International. This book was released on 1990 with total page 428 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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
Download or read book Separating the Influence of Kmax from Closure Related Stress Ratio Effects Using the Adjusted Compliance Ratio Technique written by GH. Bray and published by . This book was released on 1999 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt: In a common interpretation of crack closure, the crack is visualized as "peeling" open as stress is applied. This interpretation, while useful, has led to the assumption that the driving force for crack propagation, ?Keff, exists only when the crack tip is fully open (above K-opening). However, evidence of significant crack-tip cyclic strain below the K-opening will be presented. The exclusion of this additional driving force can yield misleading values of ?Keff. This is particularly so in the near-threshold regime where opening loads are typically high. The new analysis technique for estimating ?Keff is referred to as the adjusted compliance ratio (ACR) method and is based on an interpretation of crack closure as a stress redistribution (or load transfer) on a relatively compliant crack wake. The ACR method is evaluated using the results of fatigue crack growth tests on 6013-T651, 2324-T39 and 7055-T7751 aluminum alloys using the center crack tension M(T) specimen geometry and stress ratios ranging from -1.0 to above 0.96. The experimental results of this study indicate that the fatigue crack growth rate is not determined solely by ?Keff but also depends on Kmax. It was observed that this Kmax dependence takes the form of a power law with the magnitude of the exponent being a measure of Kmax sensitivity. As a result, ?Keff curves from all test conditions could be collapsed to a unique intrinsic FCGR curve using a simple modification to the Paris Law. It is expected that continued research in this area will lead to improvements in fatigue life prediction methodology.
Download or read book Influences of Crack Closure and Load History on Near Threshold Crack Growth Behavior in Surface Flaws written by Jira, JR. and published by . This book was released on 1990 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fatigue crack growth threshold tests are conducted on a high-strength titanium alloy using a surface flaw specimen geometry. A laser interferometer is used to monitor crack-mouth opening displacements, from which compliance determined crack length is computed. Four types of loading history involving both increasing-and decreasing-?K are used to reach a threshold condition. Two of the test conditions maintain constant Kmax under computer control. Crack closure is obtained from the load-displacement plots and used to determine an effective stress-intensity range, ?Keff. Results from all four test types indicate that a single value of an effective stress-intensity range is obtained which is independent of stress ratio, R, or load history. Crack growth rate data in the near-threshold regime, on the other hand, appear to have a dependence on R even when ?Keff is used as a correlating parameter.
Download or read book Proceedings of Fatigue Durability and Fracture Mechanics written by S. Seetharamu and published by Springer. This book was released on 2017-11-01 with total page 468 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents the proceedings of Fatigue Durability India 2016, which was held on September 28–30 at J N Tata Auditorium, Indian Institute of Science, Bangalore. This 2nd International Conference & Exhibition brought international industrial experts and academics together on a single platform to facilitate the exchange of ideas and advances in the field of fatigue, durability and fracture mechanics and its applications. This book comprises articles on a broad spectrum of topics from design, engineering, testing and computational evaluation of components and systems for fatigue, durability, and fracture mechanics. The topics covered include interdisciplinary discussions on working aspects related to materials testing, evaluation of damage, nondestructive testing (NDT), failure analysis, finite element modeling (FEM) analysis, fatigue and fracture, processing, performance, and reliability. The contents of this book will appeal not only to academic researchers, but also to design engineers, failure analysts, maintenance engineers, certification personnel, and R&D professionals involved in a wide variety of industries.
Download or read book Analytical and Experimental Study of Crack Closure Behavior Based on an S Shaped Unloading Curve written by D. Chen and published by . This book was released on 1988 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: Based on the S-shaped unloading hysteresis curve a new method for determining the crack closure has been developed in which the plastic deformation near the crack tip is taken into consideration. The crack growth rate can be expressed uniquely by the effective stress intensity range, ?Keffop = Kmax - Kop or ?Keffcl = Kmax - Kcl, which is independent of the stress ratio and the loading history. The tip of a nonpropagating crack does not open even under the maximum tensile load during one loading cycle. The measured values of the crack opening ratios Uop(?Keffop/Kmax) and Ucl(?Keffcl/Kmax) of a steadily propagating crack are mainly controlled by Kmax and the stress ratio R.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1988 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fracture and Strength of Solids VII written by Ahmad Kamal Ariffin and published by Trans Tech Publications Ltd. This book was released on 2011-01-20 with total page 1484 pages. Available in PDF, EPUB and Kindle. Book excerpt: Volume is indexed by Thomson Reuters CPCI-S (WoS). This two-volume set of 339 peer-reviewed papers covers the broad areas of Composite, Polymer and Ceramic Materials, Fracture Mechanics and Mechanisms, Materials, Mechanical Structure, Strength and Dynamics, Interface Failure and Failure Analysis, Nano-Mechanics and Structures, Damage and Failure, Structural Design and Optimisation, Fatigue and Crack Propagation, Materials Modelling and Computation, Concrete, Rock and Soil, Dynamic Fracture and Impact, Erosion and Corrosion, Smart Materials and Structures, Biomechanics and Other Novel Methods of Computer Modelling in Engineering and Science.
Download or read book An Evaluation of Plasticity Induced Crack Closure Concept and Measurement Methods written by JC. Newman and published by . This book was released on 1999 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: An assessment of the plasticity-induced crack closure concept is made, in light of some 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 or cyclic crack-tip hysteresis energy, to model crack-growth rate behavior was studied. Crack-growth simulations using the modified Dugdale crack closure model showed a close relation between traditional ?Keff and the cyclic crack-tip displacement (??eff) for an aluminum alloy and a steel over a wide range in stress ratios. 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 crack-opening stresses and the "effective" crack-tip driving parameter were evaluated from crack-growth simulations made on middle-crack tension specimens. Here, analyses were conducted under both constant-amplitude and single-spike-overload conditions. A potential source of the Kmax effect on crack-growth rates was studied at high stress ratios and at high stress levels for an aluminum alloy. Results showed that the ratio of Kmaxto Kc 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 Fatigue Crack Closure Behavior at High Stress Ratios written by CD. Carman and published by . This book was released on 1988 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fatigue crack delay behavior at high stress ratio caused by single peak overloads was investigated in two thicknesses of 7475-T731 aluminum alloy. Crack closure was measured in middle crack tension specimens with a crack-tip opening displacement gage located one-half of the specimen thickness behind the crack tip. Five overload ratios from 1.23 to 1.5 were investigated. The stress ratio was 0.7. Closure measurements indicated no closure occurred before or throughout the overload plastic zone following the overload. This was further substantiated by comparing the specimen compliance following the overload with the compliance of a low R ratio test when the crack was fully open. Scanning electron microscope studies revealed that crack tunneling and possibly reinitiation of the crack occurred, most likely a result of crack-tip blunting. The number of delay cycles was greater for the thinner mixed mode stress state specimen than for the thicker plane strain stress state specimen, which is similar to low R ratio test results and may be due to a larger plastic zone for the mixed mode case.
Download or read book Fourth International Conference on Advances in Steel Structures written by Z Y Shen and published by Elsevier. This book was released on 2005-06-07 with total page 963 pages. Available in PDF, EPUB and Kindle. Book excerpt: This two volume proceedings contains 11 invited keynote papers, 33 invited papers, and 225 contributed papers presented at the Fourth International Conference on Advances in Steel Structures (ICASS '05) held on 13-15 June 2005 in Shanghai, China. ICASS provides a forum for discussion and dissemination by researchers and designers of recent advances in the analysis, behaviour, design and construction of steel structures. Contributions to the papers came from 22 countries around the world and cover a wide spectrum of topics including: Constructional Steel, Hybrid Structures, Nonferrous Metals, Analysis of Beams and Columns, Computations, Frames, Design, Space Structures, Fabrication, along with a variety of other key subjects presented at the conference.
Download or read book Analysis of Engineering Structures and Material Behavior written by Josip Brnic and published by John Wiley & Sons. This book was released on 2018-05-07 with total page 498 pages. Available in PDF, EPUB and Kindle. Book excerpt: Theoretical and experimental study of the mechanical behavior of structures under load Analysis of Engineering Structures and Material Behavior is a textbook covering introductory and advanced topics in structural analysis. It begins with an introduction to the topic, before covering fundamental concepts of stress, strain and information about mechanical testing of materials. Material behaviors, yield criteria and loads imposed on the engineering elements are also discussed. The book then moves on to cover more advanced areas including relationships between stress and strain, rheological models, creep of metallic materials and fracture mechanics. Finally, the finite element method and its applications are considered. Key features: Covers introductory and advanced topics in structural analysis, including load, stress, strain, creep, fatigue and finite element analysis of structural elements. Includes examples and considers mathematical formulations. A pedagogical approach to the topic. Analysis of Engineering Structures and Material Behavior is suitable as a textbook for structural analysis and mechanics courses in structural, civil and mechanical engineering, as well as a valuable guide for practicing engineers.
