[PDF] On Line Fatigue Life Prediction Under Stochastic Loading By Time Series Modeling eBook

Author : Dino Anthony Celli
Publisher :
Page : 0 pages
File Size : 23,58 MB
Release : 2021
Category : Additive manufacturing
ISBN :

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The fatigue life prediction framework developed and described in the proceeding chapters can concurrently approximate both typical stress versus cycle (SN) behavior as well as the inherent variability of fatigue using a limited amount of experimental data. The purpose of such a tool is for the rapid verification and quality assessment of cyclically loaded components with a limited knowledge-base or available fatigue data in the literature. This is motivated by the novelty of additive manufacturing (AM) processes and the necessity of part-specific structural assessment. Interest in AM technology is continually growing in many industries such as aerospace, automotive, or bio-medical but components often result in highly variable fatigue performance. The determination of optimal process parameters for the build process can be an extensive and costly endeavor due to either a limited knowledge-base or proprietary restrictions. Quantifying the significant variability of fatigue performance in AM components is a challenging task as there are many underlying causes including machine-to-machine differences, recycles of powder, and process parameter selection. Therefore, a life prediction method which can rapidly determine the fatigue performance of a material with little or no prior information of the material and a limited number of experimental tests is developed as an aid in AM process parameter optimization and fatigue performance qualification. Predicting fatigue life requires the use of a previously developed and simplistic energy-based method, or Two-Point method, to generate a collection of life predictions. Then the collected life predictions are used to approximate key statistical descriptions of SN fatigue behavior. The approximated fatigue life distributions are validated against an experimentally found population of SN data at 10^4 and 10^6 cycles failure describing low cycle and high cycle fatigue. A Monte Carlo method is employed to model fatigue life by first modeling SN distributions at discrete stress amplitudes using the predicted fatigue life curves. Then the distributions are randomly sampled and a life prediction model is obtained. The approach is verified by using Aluminum 6061 data due to ample material characterization and previous life prediction analysis available in literature. SN life prediction is modeled via a Random Fatigue Limit (RFL) model using least square regression to determine the model coefficients. The life prediction framework is further developed by incorporating Bayesian statistical inference and stochastic sampling techniques to estimate the RFL model parameters. In addition, digital image correlation (DIC) is leveraged during experimentation to collect hysteresis energy as a novel method to monitor hysteresis strain energy or the assumed critical damage variable. Fatigue life prediction is performed in a dynamic way such that the life prediction model is continually updated with the generation of experimental data. The life prediction framework is applied to conventional Aluminum 6061-T6 and AM Inconel 718 and Titanium 6Al-4V. The framework is validated for life prediction and forecasting SN high cycle fatigue behavior using only low cycle fatigue data. The culmination of this work enables the rapid characterization of fatigue of AM materials by concurrently approximating the variation of fatigue life as well as high cycle fatigue behavior with low cycle fatigue data. The benefit of this framework is the significant reduction in experimental testing time, effort, and cost necessary to accurately assess the fatigue behavior of materials with limited prior information and specimen availability, such as in the case with AM Alloys.

Author : Enrique Castillo
Publisher : Springer Science & Business Media
Page : 232 pages
File Size : 49,43 MB
Release : 2009-02-27
Category : Technology & Engineering
ISBN : 1402091826

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This book is an attempt to provide a uni?ed methodology to derive models for fatigue life. This includes S-N, ?-N and crack propagation models. This is not a conventional book aimed at describing the fatigue fundamentals, but rather a book in which the basic models of the three main fatigue approaches, the stress-based, the strain-based and the fracture mechanics approaches, are contemplated from a novel and integrated point of view. On the other hand, as an alternative to the preferential attention paid to deterministic models based on the physical, phenomenological and empirical description of fatigue, their probabilistic nature is emphasized in this book, in which stochastic fatigue and crack growth models are presented. This book is the result of a long period of close collaborationbetween its two authors who, although of di?erent backgrounds, mathematical and mechanical, both have a strong sense of engineering with respect to the fatigue problem. When the authors of this book ?rst approached the fatigue ?eld in 1982 (twenty six years ago), they found the following scenario: 1. Linear, bilinear or trilinear models were frequently proposed by relevant laboratoriesandacademiccenterstoreproducetheW ̈ ohler?eld. Thiswas the case of well known institutions, which justi?ed these models based on clientrequirementsorpreferences. Thisledtotheinclusionofsuchmodels and methods as, for example, the up-and-down, in standards and o?cial practical directives (ASTM, Euronorm, etc.), which have proved to be unfortunate.

Author :
Publisher :
Page : 456 pages
File Size : 39,94 MB
Release : 1995
Category : Aeronautics
ISBN :

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Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.

Author : Y. Murakami
Publisher : Butterworth-Heinemann
Page : 251 pages
File Size : 33,80 MB
Release : 2013-10-22
Category : Technology & Engineering
ISBN : 1483161420

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The Rainflow Method in Fatigue: The Tatsuo Endo Memorial Volume documents the proceedings of The International Symposium on Fatigue Damage Measurement and Evaluation Under Complex Loadings held in Fukuoka, Japan, on 25-26 July 1991. The Symposium was held in memory of Professor Tatsuo Endo, inventor of the rainflow method of counting fatigue cycles. His contributions were key to the development of an overall method for evaluating the service life of engineering components subjected to fatigue loading. This volume contains 23 papers organized into four parts. Part I on the cycle counting method includes papers on the historical development of the rainflow cycle counting method, and a fatigue analysis data reduction concept for general multidimensional time series. Part II on ground vehicles includes studies on methods for solving vehicle fatigue problems caused by body resonance, and a synthetic computer system for fatigue damage-based design of weld structure for construction machines. Part III on fatigue testing and analysis includes papers on crack closure load measurements during fatigue crack growth tests on the titanium alloy Ti-6A1-4V, and growing fatigue cracks under varying amplitude loadings. Part IV presents a panel discussion on total system of fatigue damage measurement and evaluation under complex loadings.

Author : E. D. Poppleton
Publisher :
Page : 1 pages
File Size : 31,9 MB
Release : 1962
Category : Materials
ISBN :

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A review is given of some current methods of estimating fatigue damage and a new damage equation is derived based on the work of Corten and Dolan, and Torbe. This equation is applied to the case of a stationary Gaussian stress history and a discussion is given of the parameters appearing in the resulting equation for the fatigue life. (Author).