Download or read book Thermo mechanical Fatigue Using the Extended Space time Finite Element Method written by Ryan T. Schlinkman and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Thermomechanical high-cycle fatigue is a major failure mechanism for many engineering components in a diverse range of industries such as aerospace, automotive, and nuclear among others. Engineers trying to determine the fatigue life of a component typically rely on commercial fatigue analysis software which uses traditional fatigue criteria that are limited in their applicability. For instance, they are poor at handling multiaxial and variable amplitude loading. Furthermore, adding variable amplitude thermal loading into the mix makes using these traditional fatigue criteria even less appealing. In recent years, there have been attempts to establish methods for simulating high cycle fatigue based on finite element calculations rather than using it as a post-processing step. These include cohesive zone and continuum damage mechanics models. However, all of these methods employ cycle jumping strategies to cut down on the enormous computational time required. However, cycle jumping is not applicable for a random loading history or with random or out-of-phase temperature variation. Motivated by these current developments, this thesis proposes the use of the extended space-time finite element method (XTFEM) in combination with a two scale progressive fatigue damage model for the direct numerical simulation of thermomechanical high cycle fatigue. Instead of using the conventional explicit or implicit finite difference time integration methods, temporal approximations are introduced with FEM mesh and enriched based on the extended finite element method. After outlining the basic theory for XTFEM with thermomechanical coupling, the effectiveness of the computational framework is demonstrated in numerical examples including a coupled, thermomechanical fatigue simulation of a plate and hat stiffener model representative of a hypersonic aircraft’s structure.
Download or read book High Cycle Fatigue Simulation Using Extended Space time Finite Element Method Coupled with Continuum Damage Mechanics written by Sagar D. Bhamare and published by . This book was released on 2012 with total page 165 pages. Available in PDF, EPUB and Kindle. Book excerpt: High cycle fatigue (HCF) is a failure mechanism that dominates the design for many engineering components and structures. Surface treatments such as laser shock peening (LSP), ultrasonic nanocrystal surface modification (UNSM) and many others introduce significant residual stresses in the material, which drastically affects the fatigue life. Motivated by the need for effectively incorporating the residual stress effect in the fatigue life prediction, two approaches are developed in this thesis. In the first approach, a strain-life approach based model is implemented. Specifically, the effect of LSP induced residual stresses on fatigue life of dynamic spinal implant rods is studied. Strain-life model is applied to predict the fatigue lives of LSP treated spinal implant rods subjected to the bending fatigue loads. However, it is observed that, the traditional life prediction methods due to their empirical nature cannot effectively model residual stress relaxation. Both safe-life and damage tolerance approaches are based on limited loading conditions and specimen geometry in the test. Extrapolation of such test data to the complicated parts with multiaxial loading conditions becomes very difficult. Motivated by these limitations, a multiple temporal scale computational approach is developed to assess the fatigue life of structural components. This full-scale simulation approach is proposed in light of the challenges in employing the traditional computational method based on Finite Element Method (FEM) and semi-discrete schemes for fatigue design and analysis. Semi-discrete schemes are known to suffer from either the time-step constraints or lack of convergence due to the oscillatory nature of the fatigue loading condition. As such, simulating loading conditions with cycles on the order of hundreds of thousands and beyond is generally an impractical task for FEM. On the other hand, there is a great demand for such a computational capability as factors such as stress history and triaxiality, nonlinear coupling among the loads are known to critically influence the fatigue failure and generally not fully accounted for in the empirical design approaches that are in practice today. More specifically, an extended space-time method (XTFEM) based on the time discontinuous Galerkin formulation is proposed to account for the multiple time-scales in fatigue problems. XTFEM is coupled with the two-scale continuum damage mechanics model for evaluating fatigue damage accumulation, with a damage model governing the fatigue crack-initiation and propagation. HCF simulations are performed using the proposed methodology on a notched specimen of AISI 304L steel to predict total fatigue life under different conditions. More than 1 million loading cycles are successfully simulated to accurately predict the irreversible fatigue damage growth in the specimen. Fatigue life results are verified by comparison with those obtained using traditional safe-life approach. Based on the extensive work performed, it is concluded that the proposed formulation is robust, accurate and not restricted by the time-step for simulating the practical fatigue loading histories. Such framework is ideal for simulating the random HCF loading experienced by many engineering components during their lifetime and can serve as a robust tool for determining the residual life.
Download or read book Temperature Fatigue Interaction written by L. Remy and published by Elsevier. This book was released on 2002-03-11 with total page 397 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains a selection of peer-reviewed papers presented at the International Conference on Temperature-Fatigue Interaction, held in Paris, May 29-31, 2001, organised by the Fatigue Committee of the Societé Française de Métallurgie et de Matériaux (SF2M), under the auspices of the European Structural Integrity Society. The conference disseminated recent research results and promoting the interaction and collaboration amongst materials scientists, mechanical engineers and design engineers. Many engineering components and structures used in the automotive, aerospace, power generation and many other industries experience cyclic mechanical loads at high temperature or temperature transients causing thermally induced stresses. The increase of operating temperature and thermal mechanical loading trigger the interaction with time-dependent phenomena such as creep and environmental effects (oxidation, corrosion). A large number of metallic materials were investigated including aluminium alloys for the automotive industry, steels and cast iron for the automotive industry and materials forming, stainless steels for power plants, titanium, composites, intermetallic alloys and nickel base superalloys for aircraft industry, polymers. Important progress was observed in testing practice for high temperature behaviour, including environment and thermo-mechanical loading as well as in observation techniques. A large problem which was emphasized is to know precisely service loading cycles under non-isothermal conditions. This was considered critical for numerous thermal fatigue problems discussed in this conference.
Download or read book Thermal Fatigue of Materials and Components written by David A. Spera and published by ASTM International. This book was released on 1976 with total page 271 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Extended Finite Element Method written by Amir R. Khoei and published by John Wiley & Sons. This book was released on 2014-12-16 with total page 584 pages. Available in PDF, EPUB and Kindle. Book excerpt: Introduces the theory and applications of the extended finite element method (XFEM) in the linear and nonlinear problems of continua, structures and geomechanics Explores the concept of partition of unity, various enrichment functions, and fundamentals of XFEM formulation. Covers numerous applications of XFEM including fracture mechanics, large deformation, plasticity, multiphase flow, hydraulic fracturing and contact problems Accompanied by a website hosting source code and examples
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 692 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Research Technology 1998 written by and published by DIANE Publishing. This book was released on with total page 203 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book NASA Technical Memorandum written by and published by . This book was released on 1994 with total page 492 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Extended Finite Element Method written by Amir R. Khoei and published by John Wiley & Sons. This book was released on 2015-02-23 with total page 600 pages. Available in PDF, EPUB and Kindle. Book excerpt: Introduces the theory and applications of the extended finite element method (XFEM) in the linear and nonlinear problems of continua, structures and geomechanics Explores the concept of partition of unity, various enrichment functions, and fundamentals of XFEM formulation. Covers numerous applications of XFEM including fracture mechanics, large deformation, plasticity, multiphase flow, hydraulic fracturing and contact problems Accompanied by a website hosting source code and examples
Download or read book Applied Mechanics Reviews written by and published by . This book was released on 1987 with total page 934 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Thermomechanical Fatigue and Fracture written by M. H. Aliabadi and published by Computational Mechanics. This book was released on 2002 with total page 352 pages. Available in PDF, EPUB and Kindle. Book excerpt: This text covers the leading research, in computational methods and experimental measurements, in thermal and mechanical fatigue problems. One of the fracture problems found in engineering components, such as pressure vessels, high temperature engines and interfaces in computer technology.
Download or read book Hold Time Effect on Thermo Mechanical Fatigue Life and Its Implications in Durability Analysis of Components and Systems written by Zhigang Wei and published by . This book was released on 2014 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thermo-mechanical fatigue (TMF) resistance of engineering materials is extremely important for the durability and reliability of components and systems subjected to combined thermal and mechanical loadings. However, TMF testing, modeling, simulation, validation, and the subsequent implementation of the findings into product design are challenging tasks because of the difficulties not only in testing but also in results interpretation and in the identification of the deformation and failure mechanisms. Under combined high-temperature and severe mechanical loading conditions, creep and oxidation mechanisms are activated and time-dependent failure mechanisms are superimposed to cycle-dependent fatigue, making the life assessment very complex. In this paper, the testing procedures and results for high-temperature fatigue testing using flat specimens and thermal-fatigue testing using V-shape specimens are reported; emphasis is given to hold-time effects and the possible underlying mechanisms. The uncertainty nature and the probabilistic characteristics of the V-shape specimen test data are also presented. Finally, the impact of hold-time effect on current product design and validation procedure is discussed in terms of virtual life assessment.
Download or read book Engine Structures written by and published by . This book was released on 1988 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book International Aerospace Abstracts written by and published by . This book was released on 1996 with total page 504 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book On a Space Time Extended Finite Element Method for the Solution of a Class of Two Phase Mass Transport Problems written by Christoph Lehrenfeld and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Virtual Crack Closure Technique History Approach and Applications written by Ronald Krueger and published by . This book was released on 2002 with total page 66 pages. Available in PDF, EPUB and Kindle. Book excerpt: An overview of the virtual crack closure technique is presented. The approach used is discussed, the history summarized, and insight into its applications provided. Equations for two-dimensional quadrilateral elements with linear and quadratic shape functions are given. Formula for applying the technique in conjuction with three-dimensional solid elements as well as plate/shell elements are also provided. Necessary modifications for the use of the method with geometrically nonlinear finite element analysis and corrections required for elements at the crack tip with different lengths and widths are discussed. The problems associated with cracks or delaminations propagating between different materials are mentioned briefly, as well as a strategy to minimize these problems. Due to an increased interest in using a fracture mechanics based approach to assess the damage tolerance of composite structures in the design phase and during certification, the engineering problems selected as examples and given as references focus on the application of the technique to components made of composite materials.
Download or read book Proceedings of the 26th Intersociety Energy Conversion Engineering Conference written by and published by . This book was released on 1991 with total page 588 pages. Available in PDF, EPUB and Kindle. Book excerpt:
