Thermo-mechanical Fatigue Using the Extended Space-time Finite Element Method PDF Download
Are you looking for read ebook online? Search for your book and save it on your Kindle device, PC, phones or tablets. Download Thermo-mechanical Fatigue Using the Extended Space-time Finite Element Method PDF full book. Access full book title Thermo-mechanical Fatigue Using the Extended Space-time Finite Element Method by Ryan T. Schlinkman. Download full books in PDF and EPUB format.
Author: Ryan T. Schlinkman Publisher: ISBN: Category : Continuum damage mechanics Languages : en Pages :
Book Description
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.
Author: Ryan T. Schlinkman Publisher: ISBN: Category : Continuum damage mechanics Languages : en Pages :
Book Description
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.
Author: Sagar D. Bhamare Publisher: ISBN: Category : Languages : en Pages : 165
Book Description
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.
Author: L. Remy Publisher: Elsevier ISBN: 0080542328 Category : Technology & Engineering Languages : en Pages : 397
Book Description
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.
Author: Amir R. Khoei Publisher: John Wiley & Sons ISBN: 1118869699 Category : Science Languages : en Pages : 584
Book Description
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
Author: Zhigang Wei Publisher: ISBN: Category : High-temperature fatigue Languages : en Pages : 21
Book Description
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.
Author: Ryan T. Schlinkman
Author: Ryan T. Schlinkman
Author: Sagar D. Bhamare
Author: L. Remy
Author: Amir R. Khoei
Author: 
Author: 
Author: Zhigang Wei
Author: 
Author: 
Author: