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 Fatigue in Additive Manufactured Metals written by Filippo Berto and published by Elsevier. This book was released on 2023-09-20 with total page 321 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fatigue in Additive Manufactured Metals provides a brief overview of the fundamental mechanics involved in metal fatigue and fracture, assesses the unique properties of additive manufactured metals, and provides an in-depth exploration of how and why fatigue occurs in additive manufactured metals. Additional sections cover solutions for preventing it, best-practice design methods, and more. The book recommends cutting-edge evidence-based approaches for designing longer lasting additive manufactured metals, discusses the latest trends in the field and the various aspects of low cycle fatigue, and looks at both post-treatment and manufacturing process-based solutions. By providing international standards and testing procedures of additive manufactured metal parts and discussing the environmental impacts of additive manufacturing of metals and outlining simulation and modeling scenarios, this book is an ideal resource for users in industry. - Discusses the underlying mechanisms controlling the fatigue behavior of additive manufactured metal components as well as how to improve the fatigue life of these components via both manufacturing processes and post-processing - Studies the variability of properties in additive manufactured metals, the effects of different process conditions on mechanical reliability, probabilistic versus deterministic aspects, and more - Outlines nondestructive failure analysis techniques and highlights the effects of unique microstructural characteristics on fatigue in additive manufactured metals

Download or read book Fatigue Performance of Additively Manufactured Ti 6Al 4V written by Carter Brooks Keough and published by . This book was released on 2020 with total page 181 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fatigue Behavior and Failure Mechanisms of Direct Laser Deposited Ti 6Al 4V written by Amanda Jo Sterling and published by . This book was released on 2016 with total page 47 pages. Available in PDF, EPUB and Kindle. Book excerpt: In order for additive-manufactured parts to become widely utilized and trusted in application, their mechanical properties must be characterized. This study investigates the fatigue behavior and failure mechanisms of Ti-6Al-4V specimens fabricated using Laser Engineered Net Shaping (LENS), an additive manufacturing (AM) process. Fully-reversed strain-controlled fatigue tests were conducted on Ti-6Al-4V specimens manufactured via LENS in their as-built and heat-treated conditions. Scanning Electron Microscopy (SEM) is used to examine the fracture surfaces to qualify the failure mechanism, crack initiation sites, and defects. Due to the relatively high localized heating and cooling rates experienced during deposition, fabricated parts possess anisotropic microstructures and different mechanical properties than those of their traditionally-manufactured wrought counterparts. Porosity promotes unpredictable fatigue behavior, as evidenced by data scatter. Pore shape, size, location, and number were found to impact the fatigue behavior of additive-manufactured parts.

Download or read book Fatigue Performance of Laser Additive Manufactured Ti 6al 4V in Very High Cycle Fatigue Regime Up to 1E9 Cycles written by Eric Wycisk and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Additive manufacturing technologies are in the process of establishing themselves as an alternative production technology to conventional manufacturing, such as casting or milling. Especially laser additive manufacturing (LAM) enables the production of metallic parts with mechanical properties comparable to conventionally manufactured components. Due to the high geometrical freedom in LAM, the technology enables the production of ultra-light weight designs, and therefore gains increasing importance in aircraft and space industry. The high quality standards of these industries demand predictability of material properties for static and dynamic load cases. However, fatigue properties especially in the very high cycle fatigue (VHCF) regime until 109 cycles have not been sufficiently determined yet. Therefore, this paper presents an analysis of fatigue properties of laser additive manufactured Ti-6Al-4V under cyclic tension-tension until 107 cycles and tension-compression load until 109 cycles. For the analysis of laser additive manufactured titanium alloy Ti-6Al-4V, Woehler fatigue tests under tension-tension and tension-compression were carried out in the high cycle and VHCF regime. Specimens in stress-relieved as well as hot-isostatic-pressed conditions were analyzed regarding crack initiation site, mean stress sensitivity, and overall fatigue performance. The determined fatigue properties show values in the range of conventionally manufactured Ti-6Al-4V with particularly good performance for hot-isostatic-pressed additive-manufactured material. For all conditions, the results show no conventional fatigue limit but a constant increase in fatigue life with decreasing loads. No effects of test frequency on life span could be determined. However, independently of testing principle, a shift of crack initiation from surface to internal initiation could be observed with increasing cycles to failure.

Download or read book Fatigue Performance of Additive Manufactured Ti6Al4V in Aerospace Applications written by Magnus Kahlin and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Effect of Hot Isostatic Pressing on Fatigue Properties and Particle Shedding in Additively Manufactured Ti 6Al 4V ELI written by Julius Bonini and published by . This book was released on 2019 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hot isostatic pressing (HIP) is known to improve the fatigue properties of Ti-6Al-4V castings and can result in a significant reduction in porosity. It is often used as a postprocessing step in additively manufactured Ti-6Al-4V-ELI. Microstructure, relative levels of porosity, and particle shedding are assessed and compared for as-built and HIPed acetabular cup specimens. HIPing causes the as-built martensitic microstructure to transition to lamellar alpha and beta. The effects of HIP on additively manufactured Ti-6Al-4V-ELI as related to the fatigue performance of the material are discussed. Axial fatigue testing and the resulting stress versus the number of cycles to failure data (S-N curves) are presented from specimens of electron beam melted Ti-6Al-4V ELI in the as-built and HIPed conditions. Although the effect of HIPing on fatigue performance generally was good, significant data scatter was still found. Further analysis of fracture surfaces and cross sections are presented to explain the data scatter.

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 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 Fatigue of Ti 6Al 4V Thin Parts Made by Electron Beam Melting written by Théo Persenot and published by . This book was released on 2018 with total page 191 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nowadays, reducing the energy consumption is crucial for most of the industries. For transportation industries, it can be achieved through weight reduction. In this context, cellular structures turn out to be one of the most efficient solution. Thanks to the development of additive manufacturing, producing such complex geometries is no longer an issue. However, their use will remain limited as long as their fatigue performances are not known. This PhD work aimed at understanding the mechanisms that govern the fatigue behaviour of such cellular structures. It was first decided to focus on their unitary element, i.e. a single strut. Single struts samples were manufactured by Electron Beam Melting and then characterized in as-built conditions using different experimental techniques (X-ray tomography, optical and electron microscopy, etc.). Their static and cyclic tensile properties were then evaluated. The rough surface and in particular notch-like defects were found to be responsible for the knockdown of the mechanical properties. Regarding the fatigue resistance, their detrimental impact was predicted using Kitagawa diagrams. It also enabled to explain the impact of the build orientation. Different post-treatments were used in order to improve these mechanical properties. Chemical etching and ultrasonic shot peening (USP) significantly reduced the severity of surface defects of as-built thin struts and thus increased their mechanical properties. After USP, the fatigue properties of machined samples were almost matched. Hot Isostatic Pressing lead to the closure of all internal defects and to the coarsening of the microstructure. When combined with one of the surface treatments, the fatigue properties were further improved. Finally, a method enabling to systematically and automatically extract from the surface the most critical defects and quantitatively analyze their influence on fatigue life was proposed and discussed. It was successfully applied to chemical etched samples but improvements are mandatory for other surface conditions.

Download or read book Laser Additive Manufacturing of High Performance Materials written by Dongdong Gu and published by Springer. This book was released on 2015-04-21 with total page 322 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book entitled “Laser Additive Manufacturing of High-Performance Materials” covers the specific aspects of laser additive manufacturing of high-performance new materials components based on an unconventional materials incremental manufacturing philosophy, in terms of materials design and preparation, process control and optimization and theories of physical and chemical metallurgy. This book describes the capabilities and characteristics of the development of new metallic materials components by laser additive manufacturing process, including nanostructured materials, in situ composite materials, particle reinforced metal matrix composites, etc. The topics presented in this book, similar as laser additive manufacturing technology itself, show a significant interdisciplinary feature, integrating laser technology, materials science, metallurgical engineering and mechanical engineering. This is a book for researchers, students, practicing engineers and manufacturing industry professionals interested in laser additive manufacturing and laser materials processing. Dongdong Gu is a Professor at College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics (NUAA), PR China.

Download or read book Fatigue Performance of Ti 6Al 4V Drilled Plates written by Ioannis Violatos and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book On the Fatigue Behaviour and Modelling of Fatigue Life for Laser welded Ti 6Al 4V written by Fedor Fomin and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This aim of this work is to investigate the fatigue behaviour of laser-welded Ti-6Al-4V titanium alloy in the region of high cycle fatigue. The crack initiation mechanism and the influence of weld defects on fatigue performance were comprehensively studied. A set of post-weld treatments that can mitigate the effect of inherent weld imperfections and thereby extend the fatigue life were analysed. A robust and efficient analytical assessment model for internally-flawed materials has been developed based on a fracture mechanics approach. The developed methodology can be used for the reliability assessment of components with various types of defects, thus enabling a defect-tolerant design of welded structures.

Download or read book Mechanisms of Fatigue in Mill Annealed Ti 6Al 4V at Room Temperature and 600F written by David K. Benson and published by . This book was released on 1971 with total page 51 pages. Available in PDF, EPUB and Kindle. Book excerpt: The mechanisms of the fatigue of mill-annealed Ti-6Al-4V were studied at 600F and room temperature. Early crack initiation (N sub o approximately = or

Download or read book Multiaxial Fatigue Behavior of Additive Manufactured Metals Experiments and Modeling written by Reza Molaei and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Additive manufacturing (AM) technology has gained significant attention in recent years due to several important advantages. However, design of critical load carrying parts using this technique is still at its infancy, partly due to the inferior performance and lack of sufficient understanding of fatigue behavior of AM metals as compared to their wrought counterparts. Similar to most other components in different industries, AM parts typically undergo cyclic loadings through their service life, therefore, fatigue performance is a key performance criterion. In addition, biaxial and multiaxial stresses are common for many components, even under nominal uniaxial loading conditions where the stress state can be multiaxial due to the complexities in the geometry such as notches, or presence of multidirectional residual stresses. Such effects are more pronounced in AM, where geometry complexities result in stress concentrations, multidirectional residual stresses from the fabrication process are inevitable, and produced defects are typically directional resulting in anisotropy. Despite this fact, previous works have only focused on constant amplitude uniaxial fatigue evaluation of AM materials. One of the main advantages of the AM technique is the capability in fabricating complex geometries, in which, as mentioned, stress concentrations might be inevitable. In addition, the rough surface and un-melted particle clusters on the surface of the AM fabricated parts can also act as stress concentrations and significantly affect the fatigue behavior. Therefore, it is essential to be able to accurately characterize and predict the materials behavior in the presence of stress concentrations, such as notches. Regarding to the loading history, service load histories are typically variable amplitude in nature, where the applied stress states may vary with time and, hence, load sequence and their interactions could play an important role in such loadings. This may become more complicated for AM when considering the effect of defects, both internal and surface, and their interaction with the stress concentrations caused by the notches. The effect of such loading for AM metals and processes in terms of cumulative fatigue damage evolution need to be considered, particularly when the stress states are multiaxial. The main objective of this study was to investigate the cyclic and fatigue behaviors of AM metallic alloys under constant and variable amplitude axial, torsion, and combined axial-torsion loadings. This included both unnotched and notched conditions. Two widely used metallic materials in AM were considered for this study. These include Ti-6Al-4V and 17-4 PH stainless steel alloys. Ti-6Al-4V is a high strength, light weight, and high corrosion resistant material with many applications in aerospace and biomedical industries, and 17-4 PH is a Precipitated Hardened (PH) stainless steel with common applications in corrosion resistant applications such as aerospace, petroleum, and chemical industries. The two materials were chosen to get an understanding of the general applicability of the findings for AM metals. Depending on the material, effect of different post-fabrication treatments such as stress relieving and Hot Isostatic Pressing (HIP) methods were evaluated. Surface finish effect was also considered as another key consideration in mechanical behavior evaluation of the AM alloys. To evaluate the build orientation effect, monotonic and fatigue performance of the vertically and diagonally built (at 45) specimens were compared. All of the results from the AM metals were also compared to the fatigue behavior of their conventional wrought metals. Since response of the materials under cyclic loading can vastly differ from their monotonic response due to phenomenon such as cyclic softening or cyclic hardening, both monotonic and cyclic deformation behaviors were studied. Proper fatigue analysis where plastic deformation is present requires characterization of the cyclic deformation behavior. Failure mechanism(s) and cracking behaviors were also carefully examined for all of the materials with different conditions. Knowing these behaviors under cyclic loading is essential to performing accurate fatigue analysis. For the analysis, based on the experimental results, observed microstructures and defect structures, failure mechanisms, and cracking behaviors of the materials with different post treatment conditions, appropriate predictive multiaxial fatigue life prediction models were applied. These include classical equivalent stress- and strain- based analysis approaches as well as more advanced analysis techniques such as critical plane-based damage parameters. For the notched specimen tests, different models, including computational, analytical and empirical approaches were discussed to estimate the local stresses/strains and predict the fatigue lives. However, due to the presence of internal defects in AM materials and their interactions with notches, some of these methods may not be appropriate for AM metals. Therefore, a modification to the Theory of Critical Distance (TCD) was proposed to account for the presence of internal defects in AM metals. In order to evaluate life prediction procedures under variable amplitude multiaxial loading conditions, different aspects were considered to predict the fatigue life. These include studying the effect of defects (both internal and surface), anisotropy, and residual stresses, which may result in different load sequence effects and, therefore, different fatigue life predictions as compared to the conventionally fabricated metals.Using the geometrical freedom offered by additive manufacturing, some novel specimens geometries were also proposed. These included a plate-type specimen geometry for axial fatigue testing, a hollow cylindrical specimen for torsion testing, and two thin-walled circular cross section specimens for torsion or axial-torsion fatigue testing. The proposed geometries reduce the stress concentration at the gage-to-grip transition area, improve the uniformity of the shear stress distribution throughout the wall thickness, and increase buckling resistance during the compression part of the loading cycle..

Download or read book Utilization of a Microstructure Sensitive Fatigue Model for Additively Manufactured Ti 6Al 4V written by Brian Anthony Torries and published by . This book was released on 2016 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: The trustworthiness of AM metallic materials is not well characterized. Therefore, fatigue models that consider the unique microstructure and porosity inherent to AM parts are needed. Herein, a microstructure-based fatigue model is calibrated for use in predicting fatigue life of additively manufactured (AM) Ti-6Al-4V. Various Ti6Al-4V samples, with variations in porosity, were fabricated using Laser Engineered Net Shaping (LENS), a Direct Laser Deposition method. LENS samples in the as-built and heat treated conditions, together with wrought Ti-6Al-4V samples, underwent fatigue testing, as well as microstructure and fractographic inspection. The collected microstructure/defect statistics were used for calibrating a microstructure-sensitive fatigue model. LENS Ti-6Al-4V sample fatigue lives were found to be consistently less than those of the wrought Ti-6Al-4V samples, due to the presence of pores/defects within the LENS material. Results further indicate that fatigue life predictions from the employed model were in close agreement with experimental results.

Download or read book Strain Rate Sensitivity of Ti 6Al 4V and Inconel 718 and Its Interaction with Fatigue Performance at Different Speeds written by Joseph M. Juratovac and published by . This book was released on 2020 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fatigue failures are sudden and catastrophic, and for critical parts must be prevented through proper design. Fatigue testing of materials yields data critical for proper design but takes large spans of testing time to complete with conventional methods. Therefore, high speed fatigue testing that produces quality data is advantageous for reducing costs and time. However, it has been shown that testing speeds may affect material performance, both in static tensile testing and dynamic fatigue testing. The effect of strain rate on material performance in static tensile testing and how it relates to fatigue testing performance at commensurate strain rates was the primary objective for this thesis work for sheet Ti-6Al-4V and Inconel 718. Implementing a vibration-driven, fully reversed bending fatigue test protocol leveraging high speed testing capability, a comparable forced displacement bending fatigue test protocol, and a high speed tensile test protocol implementing Digital Image Correlation (DIC), stress versus strain data and S-N curve data was acquired to examine two strain-rates of fatigue and tensile testing. Higher ultimate tensile strengths were observed in high strain rate tests as compared to low strain rate tests, 4.23% higher for Ti-6Al-4V and 1.91% for Inconel 718. Ti-6Al-4V exhibited higher fatigue strength in high speed tests than low speed, but Inconel 718 exhibited lower fatigue strength at high speeds as compared to low speeds.