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This thesis consists of a fatigue study carried out on an aluminum alloy 2024-T3 in both time domain and frequency domain. Non-zero mean random signals of strain and stress are analyzed in time domain using usual Rainflow method and the damage is accumulated with the Palmgren-Miner rule, according to mean stress equations. The signals are analyzed in frequency domain using the power spectral density and the probability density function. The spectral domain analysis does not consider the negative effect of the mean stress in metal life under fatigue, so the correction factors for mean stresses developed by Goodman, Morrow, and Smith-Watson-Topper are used to change the power spectral density and, thus, the damage calculated by the probability density functions postulated by Dirlik and Tovo and Benasciutti. It is found that both Dirlik and Tovo and Benasciutti are non-conservative for a non-zero mean stress signal when comparing the damage to the one obtained in time domain analysis. When the spectral method is corrected, the results vary from Rainflow 4.9% for wide band and 6.8% for narrow band signals, always in the conservative zone, therefore predicting more damage. Tovo and Benasciutti 2 method is found to be the spectral function with the closest results when compared to the usual Rainflow method in time domain.
This monograph examines the theoretical foundations of the spectral method for fatigue life determination. The authors discuss a rule of description of random loading states with the matrix of power spectral density functions of the stress/strain tensor components. Some chosen criteria of multiaxial fatigue failure are analyzed. The formula proposed in this book enables readers to determine power spectral density of the equivalent history directly from the components of the power spectral density matrix of the multidimensional stochastic process.
Trends in the Analysis and Design of Marine Structures is a collection of the papers presented at MARSTRUCT 2019, the 7th International Conference on Marine Structures held in Dubrovnik, Croatia, 6-8 May 2019. The MARSTRUCT series of Conferences started in Glasgow, UK in 2007, the second event of the series having taken place in Lisbon, Portugal in March 2009, the third in Hamburg, Germany in March 2011, the fourth in Espoo, Finland in March 2013, the fifth in Southampton, UK in March 2015, and the sixth in Lisbon, Portugal in May 2017. This Conference series specialises in dealing with Ships and Offshore Structures, addressing topics in the fields of: - Methods and Tools for Loads and Load Effects - Methods and Tools for Strength Assessment - Experimental Analysis of Structures - Materials and Fabrication of Structures - Methods and Tools for Structural Design and Optimisation - Structural Reliability, Safety and Environmental Protection. Trends in the Analysis and Design of Marine Structures is an essential document for academics, engineers and all professionals involved in the area of analysis and design of Ships and Offshore Structures. About the series: The ‘Proceedings in Marine Technology and Ocean Engineering’ series is devoted to the publication of proceedings of peer-reviewed international conferences dealing with various aspects of ‘Marine Technology and Ocean Engineering’. The Series includes the proceedings of the following conferences: the International Maritime Association of the Mediterranean (IMAM) conferences, the Marine Structures (MARSTRUCT) conferences, the Renewable Energies Offshore (RENEW) conferences and the Maritime Technology (MARTECH) conferences. The ‘Marine Technology and Ocean Engineering’ series is also open to new conferences that cover topics on the sustainable exploration and exploitation of marine resources in various fields, such as maritime transport and ports, usage of the ocean including coastal areas, nautical activities, the exploration and exploitation of mineral resources, the protection of the marine environment and its resources, and risk analysis, safety and reliability. The aim of the series is to stimulate advanced education and training through the wide dissemination of the results of scientific research.
About the Series: This important new series of five volumes has been written with both the professional engineers and the academic in mind. Christian Lalanne explores every aspect of vibration and shock, two fundamental and crucially important areas of mechanical engineering, from both the theoretical and practical standpoints. As all products need to be designed to withstand the environmental conditions to which they are likely to be subjected, prototypes must be verified by calculation and laboratory tests, the latter according to specifications from national or international standards. The concept of tailoring the product to its environment has gradually developed whereby, from the very start of a design project, through the to the standards specifications and testing procedures on th e prototype, the real environment in which the product being tested will be functioning is taken into account. The five volumes of Mechanical Shock and Vibration cover all the issues that need to be addressed in this area of mechanical engineering. The theoretical analyses are placed in the context of the real world and of laboratory tests - essential for the development of specifications. Volume IV: Fatigue Damage Fatigue damage in a system with one degree of freedom is one of the two criteria applied when comparing the severity of vibratory environments. The same criterion is also employed for a specifciation representing the effects produced by the set of vibrations imposed in a real environment. In this volume, which is devoted to the calculation of fatigue damage, the author explores the hypotheses adopted to describe the behavior of material suffering fatigue and the laws of fatigue accumulation. He also considers the methods of counting the response peaks, which are used to establish the histogram when it is impossible to use the probability density of the peaks obtained with a Gaussian signal. The expressions for mean damage and its standard deviation are established and other hypotheses are tested.
This third volume of eight from the IMAC - XXXII Conference, brings together contributions to this important area of research and engineering. The collection presents early findings and case studies on fundamental and applied aspects of Structural Dynamics, including papers on: Linear Systems Substructure Modelling Adaptive Structures Experimental Techniques Analytical Methods Damage Detection Damping of Materials & Members Modal Parameter Identification Modal Testing Methods System Identification Active Control Modal Parameter Estimation Processing Modal Data
I became interested in Random Vibration during the preparation of my PhD dissertation, which was concerned with the seismic response of nuclear reactor cores. I was initiated into this field through the cla.ssical books by Y.K.Lin, S.H.Crandall and a few others. After the completion of my PhD, in 1981, my supervisor M.Gera.din encouraged me to prepare a course in Random Vibration for fourth and fifth year students in Aeronautics, at the University of Liege. There was at the time very little material available in French on that subject. A first draft was produced during 1983 and 1984 and revised in 1986. These notes were published by the Presses Poly techniques et Universitaires Romandes (Lausanne, Suisse) in 1990. When Kluwer decided to publish an English translation ofthe book in 1992, I had to choose between letting Kluwer translate the French text in-extenso or doing it myself, which would allow me to carry out a sustantial revision of the book. I took the second option and decided to rewrite or delete some of the original text and include new material, based on my personal experience, or reflecting recent technical advances. Chapter 6, devoted to the response of multi degree offreedom structures, has been completely rewritten, and Chapter 11 on random fatigue is entirely new. The computer programs which have been developed in parallel with these chapters have been incorporated in the general purpose finite element software SAMCEF, developed at the University of Liege.
Most of the models used for taking into account the influence of mean stress on fatigue life work on the basis of the correction of stress amplitudes of particular loading cycles. This can be done directly on the amplitudes or through the modification of the reference S-N curve. The mentioned procedure is also applicable for variable amplitude loading where, after rainflow cycle counting, all loading cycles described by amplitude and mean-stress value are designated. Mean-stress correction can be difficult to apply in stochastic fatigue-damage accumulation, also called the spectral method, where the load and the stress level is defined in the frequency domain using the appropriate power spectral density (PSD) function. The PSD function by itself does not give information to the user about the level of mean stress and only provides us with some statistical information of the fluctuating part of the random loading processes. The aim of the paper is to present how we can perform the mean-stress effect correction directly on a PSD function of stress using well-known models, such as proposed by Gerber, Goodman, Soderberg, or Morrow. The correction can be performed depending on the frequency component, which is a significant advantage of the presented method. The theoretical elaborations were used to develop a computer simulation used to compare the frequency-domain with the time-domain computation path. To show the effectiveness of the presented method, fatigue life has been estimated and compared with experimental fatigue test results for S355JR steel.
This book gives an overview on the fatigue of materials under non-proportional loads. It presents the rich spectrum of phenomena and treats various computational models to mathematically describe the non-proportional fatigue of materials.
Volume is indexed by Thomson Reuters CPCI-S (WoS). The collection of peer reviewed papers covers all aspects of mechanics and materials: theoretical, experimental, and computational. Specific topics of interest include: mechanics of materials, rock and soil mechanics, fluid and heat mechanics, machine parts and mechanisms, composites, micro/nano materials, steel and alloys, and building materials and other related topics.
The book explores the pertinent aspects of sustainability of green and eco-friendly composites including their development methods and processing, characterization, properties, and applications. Significance for the design and engineering of high-performance green and eco-friendly composites is discussed in the present book. Insights on a wide spectrum of potential advanced applications ranging from automotive and aerospace to biomedical and packaging, etc. using these are highlighted. Further, it discusses life cycle and carbon footprint assessment of sustainable materials. Features: Explores different processing methods of green and eco-friendly composites Discusses development and optimization of green nanocomposites for sustainable manufacturing Collates modern green and eco-friendly composites research from theory to application Covers hybridization of reinforced fibers on the performance of green and eco-friendly composites Analyzes and discusses calculation of carbon footprint and Life Cycle Assessment of composites This book is aimed at graduate students and researchers in materials science and engineering, sustainable materials, composites, and nanomaterials.