Download or read book The Role of Microstructure on High Cycle Fatigue Lifetime Variability in Ti 6Al 4V written by Alison Polasik and published by . This book was released on 2014 with total page 226 pages. Available in PDF, EPUB and Kindle. Book excerpt: Defect analyses of failed specimens indicated that damage accumulation is often localized during cyclic loading, with dislocation densities varying from one a lath to another. For all specimens, a-type dislocations are seen and c+a - type dislocations were observed only in regions of localized plastic strain. Investigation of site-specific TEM foils extracted from the crack nucleation region of [alpha]/[beta] -processed specimens provided information about the nature and behavior of dislocations during the crack nucleation event. A comparison of short- and long- life specimens provides information about differences in the evolution of the dislocation structure prior to crack nucleation. The potential of this combinatorial approach for future fatigue lifetime investigations is discussed. In particular, the project demonstrates that such an approach could be useful in developing a quantitative understanding of the role variations in microstructural features have on variations in HCF lifetime.

Download or read book A Study of Microstructure Tensile Deformation Cyclic Fatigue and Final Fracture Behavior of Commercially Pure Titanium and a Titanium Alloy written by Udaykar Bathini and published by . This book was released on 2010 with total page 131 pages. Available in PDF, EPUB and Kindle. Book excerpt: Rapid industrial growth and advances in the domains of engineering and related technologies during the last fifty years have led to the extensive use of traditional metals and their alloy counterparts. Titanium is one such metal which has gained wide popularity in the aerospace and defense related applications owing to a wide range of impressive mechanical properties like excellent specific strength ([sigma]UTS/[rho]), stiffness, corrosion and erosion resistance, fracture toughness and capability to withstand significant temperature variations. Two materials, namely commercial purity titanium (Grade 2), referred to henceforth as Ti-CP (Grade 2) and the "work-horse" alloy Ti-6Al-4V have been chosen for this research study. The intrinsic influence of material composition and test specimen orientation on the tensile and fatigue behavior for both Ti-CP (Grade 2) and Ti-6Al-4V have been discussed. Samples of both Ti-CP (Grade 2) and Ti-6Al-4V were prepared from the as-provided plate stock along both the longitudinal and transverse orientations. The specimens were then deformed to failure in uniaxial tension for the tensile tests and cyclically deformed at different values of maximum stress at constant load ratio of 0.1 for the high cycle fatigue tests. The microstructure, tensile properties, resultant fracture behavior of the two materials is presented in the light of results obtained from the uniaxial tensile tests. The conjoint influence of intrinsic microstructural features, nature of loading and specimen properties on the tensile properties is discussed. Also, the macroscopic fracture mode, the intrinsic features on the fatigue fracture surface and the role of applied stress-microstructural feature interactions in governing failure for the cyclic fatigue properties for both the materials under study Ti-CP (Grade 2) and the "work-horse" alloy Ti-6Al-4V have been discussed in detail. Careful study of the microstructure for Ti-CP (Grade 2) material at a low magnification revealed the primary alpha grains to be intermingled with small pockets of beta grains. Observation at the higher allowable magnifications of the optical microscope revealed very fine alpha phase lamellae located within the beta grain. The microhardness and macrohardness measurements were consistent through the sheet specimen for Ti-CP (Grade 2) and slightly lower compared to Ti-6Al-4V. However, the macrohardness was marginally higher than the microhardness resulting from the presence of a large volume fraction of the soft alpha phase. The hardness values when plotted reveal marginal spatial variability. Tensile fracture of Ti-CP (Grade 2) was at an inclination to the far field tensile stress axis for both longitudinal and transverse orientations. The overload region revealed a combination of fine microscopic cracks, microscopic voids of varying size and randomly distributed through the surface, and a large population of shallow dimples, features reminiscent of locally brittle and ductile failure mechanisms. The maximum stress ([sigma]maximum) versus fatigue life (Nf) characteristics shown by this material is quite different from those non-ferrous metals that exhibit a well-defined endurance limit. When compared at equal values of maximum stress at a load ratio of 0.1, the fatigue life of the transverse specimen is noticeably greater than the longitudinal counterpart. At equivalent values of maximum elastic strain, the transverse specimens revealed noticeably improved fatigue life as compared one-on-one to the longitudinal counterparts. Careful observations of the Ti-6Al-4V alloy microstructure over a range of magnifications spanning very low to high magnification revealed a duplex microstructure consisting of the near equiaxed alpha and transformed beta phases. The primary near equiaxed shaped alpha grains (light in color) was well distributed in a lamellar matrix with transformed beta (dark in color). The microhardness and macrohardness values recorded for the Ti-6Al-4V alloy reveal it to be harder than the commercially pure (Grade 2) material. However, for the Ti-6Al-4V alloy the microhardness is noticeably higher than the corresponding macrohardness value that can be ascribed to the presence of a population of processing-related artifacts and the hard beta-phase. Tensile fracture of the Ti-6Al-4V alloy was macroscopically rough and essentially normal to the far field stress axis for the longitudinal orientation and cup-and-cone morphology for the transverse orientation. However, microscopically, the surface was rough and covered with a population of macroscopic and fine microscopic cracks, voids of varying size, a population of shallow dimples of varying size and shape, features reminiscent of locally brittle and ductile failure mechanisms. When compared at equal values of maximum stress at a load ratio of 0.1, there is a marginal to no influence of microstructure on high cycle fatigue life of both orientations of the alloy.

Download or read book Titanium and Titanium Alloys written by Christoph Leyens and published by John Wiley & Sons. This book was released on 2006-03-06 with total page 532 pages. Available in PDF, EPUB and Kindle. Book excerpt: This handbook is an excellent reference for materials scientists and engineers needing to gain more knowledge about these engineering materials. Following introductory chapters on the fundamental materials properties of titanium, readers will find comprehensive descriptions of the development, processing and properties of modern titanium alloys. There then follows detailed discussion of the applications of titanium and its alloys in aerospace, medicine, energy and automotive technology.

Download or read book Analysis of Methods for Determining High Cycle Fatigue Strength of a Material with Investigation of Ti 6A1 4V Gigacycle Fatigue Behavior written by Randall D. Pollak and published by . This book was released on 2005 with total page 508 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fretting Fatigue written by David W. Hoeppner and published by ASTM International. This book was released on 2000 with total page 554 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume includes 36 of the 40 papers presented at the symposium, and a collection of six keynote papers providing background on the subject. Topics covered include parameter effects, environmental effects, crack nucleation, material and microstructural effects, damage analysis, fracture mechanic

Download or read book The High Cycle Fatigue Behavior of Ti 6Al 4V Alloy written by R. K. Steel and published by . This book was released on 1975 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt: The cyclic stress-strain behavior and the S/N behavior of a 'pseudo-elastic' alloy, Ti-6Al-4V of coarsened microstructure, and of a 'plastic' material, copper, are compared. In accord with views recently put forth by Freudenthal, important differences are noted between these two types of materials. These differences include the mode of crack initiation, the intensity of the Bauschinger effect, and the level below macroscopic yeild at which long-life fatigue data lie. (Author).

Download or read book Multiaxial Fatigue written by Darrell Socie and published by SAE International. This book was released on 1999-12-15 with total page 510 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides practicing engineers, researchers, and students with a working knowledge of the fatigue design process and models under multiaxial states of stress and strain. Readers are introduced to the important considerations of multiaxial fatigue that differentiate it from uniaxial fatigue.

Download or read book Illuminating the Mechanisms that Control the Fatigue Performance of Additively Manufactured Ti 6Al 4V written by Peipei Li and published by . This book was released on 2018 with total page 326 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation composes three papers detailing work intended to examine the mechanisms that control the failure of additively manufactured (AM) metallic materials. All studies aim at developing models to predict the fatigue performance of AM Ti-6Al-4V utilizing computational tools, and ultimately to realize a predictive process-structure-performance modeling framework. First, a thorough literature review was conducted to catalog and analyze the published fatigue performance data of AM Ti-6Al-4V. Comparing to traditionally manufactured Ti-6Al-4V, the key features that control fatigue performance of AM parts are the same as the ones governing traditional cast and wrought, i.e. surface finish, residual stress, build defects and microstructure. Second, possible mechanisms by which hot isostatic pressing (HIP) improves the high cycle fatigue performance of powder bed fused (PBF) Ti-6Al-4V were examined. The results suggest that HIP may act most significantly by decreasing the fraction of the defect population that can initiate fatigue cracks, both by decreasing defect sizes below a threshold and by changing the microstructure around defects, the latter of which is confirmed by an electron backscatter diffraction (EBSD) study. The gained understanding is used to provide initial guidance on the choice of optimum HIP parameter via a continuum mechanics model. Third, to understand the role of geometry on the fatigue performance of as-built laser PBF Ti-6Al-4V, two sets of specimens only differing in gage surface area were fabricated. A significant difference in fatigue performance was observed between these two geometries. Possible origins of the observed difference, such as surface roughness, microstructure, build defects, and mechanical interactions between fatigue cracks and the specimen geometry, were investigated. A weakest link approach with X-ray CT measurements of build defects in the two geometries was able to capture the geometric effect on the fatigue performance, consistent with the experimental data. To attempt to link the defect populations with the thermal histories resulting from the different geometries, a linear heat conduction thermal model was performed. Lastly, a predictive model framework that links the material properties from the witness coupon data with the fatigue performance of structural components was developed to facilitate the qualification and certification of PBF technique in safety critical loading bearing applications. Focusing on a PBF aircraft link component, a simple deterministic model was first developed. A probabilistic fatigue model was then constructed to predict both the median trend and variability of the fatigue life of the link component, taking both the populations of fatigue crack initiation sites and the full stress field from finite element (FE) simulations as inputs. Both models under-predicted the median fatigue life of the link component, which we hypothesize to be due to the overestimation of the multiaxial fatigue indicator. The predicted variability of the fatigue life of the probabilistic model showed good agreement with the experiments. In addition, the effect of crack initiation site density on the fatigue performance of the link component was also examined with the probabilistic model.

Download or read book Titanium Alloys written by Maciej Motyka and published by BoD – Books on Demand. This book was released on 2019-11-27 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt: Titanium alloys, due to unique physical and chemical properties (mainly high relative strength combined with very good corrosion resistance), are considered as an important structural metallic material used in hi-tech industries (e.g. aerospace, space technology). This book provides information on new manufacturing and processing methods of single- and two-phase titanium alloys. The eight chapters of this book are distributed over four sections. The first section (Introduction) indicates the main factors determining application areas of titanium and its alloys. The second section (Manufacturing, two chapters) concerns modern production methods for titanium and its alloys. The third section (Thermomechanical and surface treatment, three chapters) covers problems of thermomechanical processing and surface treatment used for single- and two-phase titanium alloys. The fourth section (Machining, two chapters) describes the recent results of high speed machining of Ti-6Al-4V alloy and the possibility of application of sustainable machining for titanium alloys.

Download or read book Microplasticity written by Charles J. McMahon and published by . This book was released on 1968 with total page 448 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Effect of Microstructure on High Cycle Fatigue Thresholds in a Turbine Engine Titanium Alloy written by Ravi Kiran Nalla and published by . This book was released on 2001 with total page 404 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Titanium written by Matthew J. Donachie and published by ASM International. This book was released on 2000 with total page 381 pages. Available in PDF, EPUB and Kindle. Book excerpt: Designed to support the need of engineering, management, and other professionals for information on titanium by providing an overview of the major topics, this book provides a concise summary of the most useful information required to understand titanium and its alloys. The author provides a review of the significant features of the metallurgy and application of titanium and its alloys. All technical aspects of the use of titanium are covered, with sufficient metals property data for most users. Because of its unique density, corrosion resistance, and relative strength advantages over competing materials such as aluminum, steels, and superalloys, titanium has found a niche in many industries. Much of this use has occurred through military research, and subsequent applications in aircraft, of gas turbine engines, although more recent use features replacement joints, golf clubs, and bicycles.Contents include: A primer on titanium and its alloys, Introduction to selection of titanium alloys, Understanding titanium's metallurgy and mill products, Forging and forming, Castings, Powder metallurgy, Heat treating, Joining technology and practice, Machining, Cleaning and finishing, Structure/processing/property relationships, Corrosion resistance, Advanced alloys and future directions, Appendices: Summary table of titanium alloys, Titanium alloy datasheets, Cross-reference to titanium alloys, Listing of selected specification and standardization organizations, Selected manufacturers, suppliers, services, Corrosion data, Machining data.

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.

Download or read book Electron Beam Melting of Metastable Austenitic Stainless Steel written by Johannes Günther and published by BoD – Books on Demand. This book was released on 2020-01-01 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt: The primary focus of this work is the processing – microstructure – property correlation of EBM manufactured high-alloyed austenitic CrMnNi stainless steel. Independent of the applied process parameters, to this point this alloy exhibits a fine-grained and weak textured microstructure in the as-built state upon EBM processing. As detailed in the literature review, this is opposite to numerous alloys like the benchmark AISI 316L stainless steel, which are commonly characterized by epitaxial growth of columnar grains elongated parallel to building direction. A theory for this unusual observation is presented based on a grain refinement due the process-inherent cyclic heat-treatment, i.e. repetitive reheating and partial melting of the consolidated material due to the energy input during melting of subsequent layers and resulting solid-liquid as well as solid-solid (ferritic bcc to austenitic fcc phase and vice versa) phase transformations. A calculation of the phase diagram, differential thermal II Abstract analysis and the investigation of the uppermost layers of bulky and thin-walled EBM processed structures are conducted to support this assumption. Moreover, the CrMnNi stainless steel specimens are characterized by an outstanding damage tolerance, which is demonstrated by tensile testing and examination of the fracture surfaces revealing large lack-of-fusion defects due to unsuitable process parameters. Combined EBSD and X-ray diffraction analysis attribute the high damage tolerance to a pronounced strain hardening and mitigation of the effect of defects due to the transformation-induced plasticity (TRIP) effect. The deformation-induced martensitic transformation and associated strain hardening has also been correlated to a considerable low-cycle fatigue performance even under the presence of large inhomogeneities. The chemical composition of the alloy upon EBM processing is strongly dependent on the process parameters, i.e. it is demonstrated that the evaporation rate of Mn varies with the scan strategy and volumetric energy density. This phenomenon is utilized for the fabrication of homogeneous specimens with different Mn concentrations and resulting mechanical properties.These findings are subsequently employed for a prove-of-concept of the possibility to produce functionally graded material by a spatial adjustment of the scan strategy throughout the layer-wise built-up of objects. This is a novel approach for the synthetization of functionally graded materials based on the processing of one homogenous precursor powder feedstock. In summary, the particular CrMnNi stainless steel is introduced as a novel alloy design for AM because it addresses current material-related issues inherent in layer-wise technologies and potentially further contributes to the exploitation of the full potential of AM.

Download or read book High Cycle Fatigue written by Theodore Nicholas and published by Elsevier. This book was released on 2006-07-07 with total page 657 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dr Theodore Nicholas ran the High Cycle Fatigue Program for the US Air Force between 1995 and 2003 at Wright-Patterson Air Force Base, and is one of the world's leading authorities on the subject, having authored over 250 papers in leading archival journals and books. Bringing his plethora of expertise to this book, Dr Nicholas discusses the subject of high cycle fatigue (HCF) from an engineering viewpoint in response to a series of HCF failures in the USAF and the concurrent realization that HCF failures in general were taking place universally in both civilian and military engines. Topic covered include: - Constant life diagrams - Fatigue limits under combined LCF and HCF - Notch fatigue under HCF conditions - Foreign object damage (FOD) - Brings years of the Author's US Air Force experience in high cycle fatigue together in one text - Discusses HCF in the context of recent international military and civilian engine failures

Download or read book Fatigue of Structures and Materials written by J. Schijve and published by Springer Science & Business Media. This book was released on 2008-12-16 with total page 627 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fatigue of structures and materials covers a wide scope of different topics. The purpose of the present book is to explain these topics, to indicate how they can be analyzed, and how this can contribute to the designing of fatigue resistant structures and to prevent structural fatigue problems in service. Chapter 1 gives a general survey of the topic with brief comments on the signi?cance of the aspects involved. This serves as a kind of a program for the following chapters. The central issues in this book are predictions of fatigue properties and designing against fatigue. These objectives cannot be realized without a physical and mechanical understanding of all relevant conditions. In Chapter 2 the book starts with basic concepts of what happens in the material of a structure under cyclic loads. It illustrates the large number of variables which can affect fatigue properties and it provides the essential background knowledge for subsequent chapters. Different subjects are presented in the following main parts: • Basic chapters on fatigue properties and predictions (Chapters 2–8) • Load spectra and fatigue under variable-amplitude loading (Chapters 9–11) • Fatigue tests and scatter (Chapters 12 and 13) • Special fatigue conditions (Chapters 14–17) • Fatigue of joints and structures (Chapters 18–20) • Fiber-metal laminates (Chapter 21) Each chapter presents a discussion of a speci?c subject.

Download or read book Fatigue of Materials written by Raghavan Srinivasan and published by John Wiley & Sons. This book was released on 2010-11-11 with total page 449 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fatigue of Materials covers a broad spectrum of topics that represent the truly diverse nature of the subject that has grown to become a key area of scientific and applied research. Constituting an international forum for the materials industry, the book provides the perspectives of operators, engineers, and researchers regarding all aspects of current and emerging technologies for materials.