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 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 Multiscale Simulation of Failure Based on Space time Finite Element Method and Non ordinary State based Peridynamics written by Shogo Wada and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Engineering materials such as rubbers are widely used in industrial applications and are often exposed to cyclic stress and strain conditions while in service. To ensure safety and reliability, quantifying the effect of loads on the life is an important but challenging task, due to the combination of geometric/material nonlinearities and loading conditions for extended time durations. In this work, a novel simulation-based approach based on space-time finite element method (FEM) is presented with a goal to capture fatigue failure in rubbery material subjected to cyclic loads and dynamic fracture in general elastic solids. It is established by integrating the time discontinuous Galerkin (TDG) formulation with either nonlinear material constitutive laws or peridynamics models. In the first implementation, nonlinear space-time FEM framework is established and integrated with a continuum damage mechanics (CDM) model to account for the damage evolution due to cyclic loading. CDM parameters for synthetic rubber are calibrated based on fatigue experiment. The nonlinear system in space-time FEM is solved using Newton’s method in which the system Jacobian is approximated with a finite difference approach. The developed approach is then employed to solve a set of benchmark problems involving fracture and low cycle fatigue in rubber. Additional tests on notched rubber sheet specimen are carried out to validate the simulation predictions. The simulation predictions yield good agreement with the tests. In addition, it is shown that responses to fatigue load with 106 cycles can be captured using the proposed approach. In the second case, a multiscale method that couples the space-time FEM based on the time discontinuous Galerkin method with non-ordinary state-based peridynamics (NOPD) is developed for dynamic fracture simulation. A concurrent coupling scheme is presented for the coupling, in which the whole domain is discretized by finite elements, and a local domain of interest is simulated with NOPD. The space-time FEM approach allows flexible choice of time step size and this makes the computation more effective. As a meshfree method, NOPD is introduced as a fine scale representation to capture the initiation and propagation of the crack. Through coupling to space-time FEM, NOPD simulation domain moves with the propagating crack front, leading to an adaptive multiscale simulation scheme. The robustness of this methodology is demonstrated through examples of a linear elastic material, in which comparisons are made to the full scale NOPD simulation. In summary, the proposed space-time approach introduces the key capability to establish approximations in the temporal domain, thus enabling prediction of nonlinear responses that are strongly time-dependent. This is demonstrated in two cases in this dissertation: the first involves fatigue failure prediction at extended time scale, and the second deals with dynamic fracture at small time scale. Based on the implementation and results, it is concluded the established space-time FEM framework is both efficient and accurate, and overcomes the critical limit of the traditional FEM approach using semi-discrete time integration schemes. The presented framework is ideal for many engineering problems featured by a multitude of temporal scales.
Download or read book Multiscale Methods for Fatigue and Dynamic Fracture Failure and High performance Computing Implementation written by Rui Zhang and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation presents several multiscale methods for material failure and implementations on high-performance computing (HPC) platforms. The work is motivated by thechallenges in fully capturing the mechanics of failure using a single scale method. As such,multiscale approaches that incorporate multiple temporal and spatial scales have been established. To address the high computational costs, efficient algorithms and their implementations on the HPC platform featuring many-core architectures have been developed.Based on the topics being addressed, the dissertation is divided into two parts. First, a multiscale computational framework for high cycle fatigue (HCF) life prediction is establishedby integrating the Extended Space-Time Finite Element Method (XTFEM) with multiscalefatigue damage models. XTFEM is derived based on the time-discontinuous Galerkin approach, which is shown to be A-stable and high-order accurate. While the robustness ofXTFEM has been extensively demonstrated, the associated high computational cost remains a critical barrier for its practical applications. A novel hybrid iterative/direct solveris proposed with a unique preconditioner based on Kronecker product decomposition of thespace-time stiffness matrix. XTFEM is further accelerated by utilizing HPC platforms featuring a hierarchy of distributed- and shared-memory parallelisms. A two-scale damagemodel is coupled with XTFEM to capture nonlinear material behaviors under HCF loadingand accelerated by parallel computing using both CPUs and GPUs. Furthermore, an efficientdata-driven microstructure-based multiscale fatigue damage model is established by employing the Self-consistent Clustering Analysis, which is a reduced-order method derived fromMachine Learning. Robustness and efficiency of the framework are demonstrated throughbenchmark problems. HCF simulations are conducted to quantify key effects due to meanstress, multiaxial load conditions, and material microstructures.In the second part, a concurrent multiscale method to dynamic fracture is established bycoupling Peridynamics (PD) with the classical Continuum Mechanics (CCM). PD is a novelnonlocal generalization of CCM. It is governed by an integro-differential equation of motion,which is free of spatial derivatives. This salient feature makes it attractive for problemswith spatial discontinuities such as cracks. However, it generally leads to a much highercomputational cost due to its nonlocality. There is a continuing interest to couple PDwith CCM to improve efficiency while preserving accuracy in critical regions. In this work,Finite Element (FE) simulation is performed over the entire domain and coexists with alocal PD region where crack pre-exists or is expected to initiate. The coupling schemeis accomplished by a bridging-scale projection between the two scales and a class of twoway nonlocal matching boundary conditions that eliminates spurious wave reflections at thenumerical interface and transmits waves from the FE domain to the PD region. An adaptivescheme is established so that the PD region is dynamically relocated to track propagatingcrack. Accuracy and efficiency of the proposed method are illustrated by wave propagationexamples. Its effectiveness and robustness in material failure simulation are demonstratedby benchmark problems featuring brittle fracture.Finally, conclusions are drawn from the research work presented and prospective futuredevelopments of the established multiscale methods are provided.
Download or read book High Cycle Fatigue written by Theodore Nicholas and published by Elsevier. This book was released on 2006-07-07 with total page 657 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dr Theodore Nicholas ran the High Cycle Fatigue Program for the US Air Force between 1995 and 2003 at Wright-Patterson Air Force Base, and is one of the world's leading authorities on the subject, having authored over 250 papers in leading archival journals and books. Bringing his plethora of expertise to this book, Dr Nicholas discusses the subject of high cycle fatigue (HCF) from an engineering viewpoint in response to a series of HCF failures in the USAF and the concurrent realization that HCF failures in general were taking place universally in both civilian and military engines. Topic covered include: - Constant life diagrams - Fatigue limits under combined LCF and HCF - Notch fatigue under HCF conditions - Foreign object damage (FOD) - Brings years of the Author's US Air Force experience in high cycle fatigue together in one text - Discusses HCF in the context of recent international military and civilian engine failures
Download or read book Applied mechanics reviews written by and published by . This book was released on 1948 with total page 400 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 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 Engineering Damage Mechanics written by Jean Lemaitre and published by Springer Science & Business Media. This book was released on 2006-01-16 with total page 396 pages. Available in PDF, EPUB and Kindle. Book excerpt: Reflecting his major contributions to the field, Jean Lemaitre’s "Engineering Damage Mechanics" presents simplified and advanced methods organized within a unified framework for designers of any mechanical component. Explains how to apply continuous damage mechanics to failures of mechanical and civil engineering components in ductile, creep, fatigue and brittle conditions. Incorporates many basic examples, while emphasizing key practical considerations such as material parameter identification, and provides perspective on the advantage and disadvantages of various approaches.
Download or read book Introduction to Unified Mechanics Theory with Applications written by Cemal Basaran and published by Springer Nature. This book was released on 2021-02-02 with total page 452 pages. Available in PDF, EPUB and Kindle. Book excerpt: This text describes the mathematical formulation and proof of the unified mechanics theory (UMT) which is based on the unification of Newton’s laws and the laws of thermodynamics. It also presents formulations and experimental verifications of the theory for thermal, mechanical, electrical, corrosion, chemical and fatigue loads, and it discusses why the original universal laws of motion proposed by Isaac Newton in 1687 are incomplete. The author provides concrete examples, such as how Newton’s second law, F = ma, gives the initial acceleration of a soccer ball kicked by a player, but does not tell us how and when the ball would come to a stop. Over the course of Introduction to Unified Mechanics Theory, Dr. Basaran illustrates that Newtonian mechanics does not account for the thermodynamic changes happening in a system over its usable lifetime. And in this context, this book explains how to design a system to perform its intended functions safely over its usable life time and predicts the expected lifetime of the system without using empirical models, a process currently done using Newtonian mechanics and empirical degradation/failure/fatigue models which are curve-fit to test data. Written as a textbook suitable for upper-level undergraduate mechanics courses, as well as first year graduate level courses, this book is the result of over 25 years of scientific activity with the contribution of dozens of scientists from around the world including USA, Russia, Ukraine, Belarus, Spain, China, India and U.K.
Download or read book Crystal Plasticity Finite Element Methods written by Franz Roters and published by John Wiley & Sons. This book was released on 2011-08-04 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt: Written by the leading experts in computational materials science, this handy reference concisely reviews the most important aspects of plasticity modeling: constitutive laws, phase transformations, texture methods, continuum approaches and damage mechanisms. As a result, it provides the knowledge needed to avoid failures in critical systems udner mechanical load. With its various application examples to micro- and macrostructure mechanics, this is an invaluable resource for mechanical engineers as well as for researchers wanting to improve on this method and extend its outreach.
Download or read book Mechanics of Fatigue written by Vladimir V. Bolotin and published by CRC Press. This book was released on 2020-07-09 with total page 210 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mechanics of Fatigue addresses the range of topics concerning damage, fatigue, and fracture of engineering materials and structures. The core of this resource builds upon the synthesis of micro- and macro-mechanics of fracture. In micromechanics, both the modeling of mechanical phenomena on the level of material structure and the continuous approach are based on the use of certain internal field parameters characterizing the dispersed micro-damage. This is referred to as continuum damage mechanics. The author develops his own theory for macromechanics, called analytical fracture mechanics. This term means the system cracked body - loading or loading device - is considered as a mechanical system and the tools of analytical (rational) mechanics are applied thoroughly to describe crack propagation until the final failure. Chapter discuss: preliminary information on fatigue and engineering methods for design of machines and structures against failures caused by fatigue fatigue crack nucleation, including microstructural and continuous models theory of fatigue crack propagation fatigue crack growth in linear elastic materials subject to dispersed damage fatigue cracks in elasto-plastic material, including crack growth retardation due to overloading as well as quasistationary approximation fatigue and related phenomena in hereditary solids application of the theory fatigue crack growth considering environmental factors unidirectional fiber composites with ductile matrix and brittle, initially continuous fibers laminate composites Mechanics of Fatigue serves students dealing with mechanical aspects of fatigue, conducting research in fracture mechanics, structural safety, mechanics of composites, as well as modern branches of mechanics of solids and structures.
Download or read book Fatigue of Materials at Very High Numbers of Loading Cycles written by Hans-Jürgen Christ and published by Springer. This book was released on 2018-11-19 with total page 624 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book represents the final reports of the scientific projects funded within the DFG-SPP1466 and, hence, provides the reader with the possibility to familiarize with the leading edge of VHCF research. It draws a balance on the existing knowledge and its enhancement by the joint research action of the priority program. Three different material classes are dealt with: structural metallic materials, long-fiber-reinforced polymers and materials used in micro-electro-mechanical systems. The project topics address the development of suitable experimental techniques for high-frequency testing and damage monitoring, the characterization of damage mechanisms and damage evolution, the development of mechanism-based models and the transfer of the obtained knowledge and understanding into engineering regulations and applications.
Download or read book Design of High Cycle Biaxial Fatigue Sample Near Resonance Using Finite Element Modeling written by Matthew Sorna and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Fatigue, the gradual accumulation of damage in of a material due to microstructural damage and subsequent crack growth, is prevalent among almost all components who sustain prolonged periods of cyclic loading. The number of loading cycles until failure is known as the fatigue life of a material, and is a function of the applied cyclic stress history. For certain materials and operating conditions, it is common to assume infinite fatigue life for stress amplitude levels below a certain value, known as the endurance limit. In this work, rectangular fatigue specimens were designed and simulated using finite element analysis software. Both free-free and fixed-free boundary conditions were studied to achieve a near resonance response assuming a commercially available shaker as the source of harmonic excitation. Eigenfrequency studies were used to determine resonant frequencies and time domain studies were used to simulate loading cycle histories. In the time domain analysis, special consideration was required for defining boundary conditions for valid finite element solutions. The results showed that nearly constant stress amplitude cycles were obtainable at the target stress of 140 MPa. By manipulating the free parameters of the shaker, a wide range of relatively low stress amplitudes can be generated to fully explore the high cycle (> 10^8 cycles) fatigue regime. Future work can be done to validate the simulated results, as well as design the appropriate mounting fixtures used to deliver the two boundary conditions used in the simulation. The proposed technique would allow measurement of high cycle fatigue properties, which can inform design choices and reduced costs associated with system failure and costs incurred through system downtime.
Download or read book Random Fatigue written by K. Sobczyk and published by Academic Press. This book was released on 2012-12-02 with total page 277 pages. Available in PDF, EPUB and Kindle. Book excerpt: For many years fatigue has been a significant and difficult problem for engineers, especially for those who design structures such as aircraft, bridges, pressure vessels, and cranes. Fatigue of engineering materials is commonly regarded as an important deterioration process and a principal mode of failure for various structural and mechanical systems. This book presents a unified approach to stochastic modeling of the fatigue phenomenon, particularly the fatigue crack growth process. The main approaches to construction of these stochastic models are presented to show their methodological consistency and potential usefulness in engineering practice. The analyses contained in this work should also inspire the development of new approaches for designing and performing fatigue experiments.
Download or read book A Multiscale Analysis and Extension of an Energy Based Fatigue Life Prediction Method for High Low and Combined Cycle Fatigue written by Casey M. Holycross and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: An improved fatigue life prediction method has been developed for Al 6061-T6511 test specimens using strain energy density as the criteria for assessing fatigue strength of plain and notched geometries at various stress ratios and loading spectra for cyclic lives from 10 to 105. The approach features interrogation at continuum and mesoscales using both a traditional fracture mechanics approach and a newly developed experimental procedure to determine strain energy density about machined notch roots in situ using digital image correlation. Testing revealed a critical strain energy density value independent of load ratio, notch geometry, and the effects of localized plasticity, indicating a new material dependent quantity to assess cyclic damage. The method better predicts lifetimes in low cycle fatigue than previously developed approaches, and has inherent capability to describe an endurance limit phenomenon. This study constitutes the most comprehensive investigation of strain energy density within the framework of the energy based fatigue life prediction method developed by Scott-Emuakpor et al., offering significant insight into cyclic damage behavior for all practical length scales and lifetimes.
Download or read book International Aerospace Abstracts written by and published by . This book was released on 1999 with total page 1044 pages. Available in PDF, EPUB and Kindle. Book excerpt:
