A Multiscale Analysis and Extension of an Energy Based Fatigue Life Prediction Method for High, Low, and Combined Cycle Fatigue PDF Download

Author: Casey M. Holycross
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Book Description
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.

Author: Dino Anthony Celli
Publisher:
ISBN:
Category : Additive manufacturing
Languages : en
Pages : 0

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Book Description
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: Claude Amzallag
Publisher: ASTM International
ISBN:
Category :
Languages : en
Pages : 658

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Author: John Nicholas Wertz
Publisher:
ISBN:
Category :
Languages : en
Pages : 49

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Abstract: An energy-based cycle-dependent fatigue life prediction framework for the calculation of torsional fatigue life and remaining life has been developed. The framework for this fatigue prediction method is developed in accordance with previously developed energy-based axial and bending fatigue life prediction approaches, which state: the total strain energy density accumulated during both a monotonic fracture event and cyclic processes is the same material property, where each can be determined by measuring the area beneath the monotonic true stress-strain curve and the area within a hysteresis loop, respectively. The energy-based fatigue life prediction framework is composed of the following entities: (1) the development of a shear fatigue testing procedure capable of assessing cyclic plastic strain energy density accumulation in a pure shear stress state and (2) the incorporation of an energy-based fatigue life calculation scheme to determine the remaining fatigue life of in-service gas turbine materials subjected to pure shear fatigue. Validation of the improved theory was attempted but failed due to undesired axial loading occurring during testing. Future work was proposed to address the issues.

Author: Darrell Socie
Publisher: SAE International
ISBN: 0768065100
Category : Technology & Engineering
Languages : en
Pages : 510

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Book Description
This book provides practicing engineers, researchers, and students with a working knowledge of the fatigue design process and models under multiaxial states of stress and strain. Readers are introduced to the important considerations of multiaxial fatigue that differentiate it from uniaxial fatigue.

Author: Onome Ejaro Scott-Emuakpor
Publisher:
ISBN:
Category : Bending stresses
Languages : en
Pages : 156

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Book Description
Abstract: An accelerated method for determining the fatigue stress versus cycle life (S-N) behavior of isotropic materials is developed for prediction of axial (tension-compression), bending, shear, and multi-axial fatigue life at various stress ratios. The framework for this accelerated method was developed in accordance with a previous understanding of a strain energy and fatigue life correlation, which states: the total strain energy dissipated during a monotonic fracture and a cyclic process is the same material property, where each can be determined by measuring the area underneath the monotonic true stress-strain curve and the area within a hysteresis loop, respectively. The developed framework consists of the following six elements: (1) New experimental procedures used to acquire more sufficient uniaxial and multi-axial test results than conventional methods, (2) an analytical representation for the effect of the stress gradient through the fatigue zone, thus providing capability for bending fatigue prediction, (3) the effect of mean stress on fatigue life for tension/compression and bending, (4) development of an improved energy-based prediction criterion for shear loading at various stress ratios, (5) fatigue life prediction for materials experiencing the endurance limit phenomenon, and (6) the development of a multi-axial fatigue life prediction method. Validation of this accelerated fatigue life determination framework is achieved based on comparison with numerous experimental results acquired from Aluminum 6061-T6 and Titanium 6Al-4V. The results of the comparison are extremely encouraging, thus providing justification that the future direction for the strain-energy based fatigue life prediction method is very promising.

Author: Touhid Zarrin-Ghalami
Publisher:
ISBN:
Category : Elastomers
Languages : en
Pages : 153

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Book Description
This study investigates constitutive behavior, material properties and fatigue damage under constant and variable amplitude uniaxial and multiaxial loading conditions, with the goal of developing CAE analytical techniques for durability and life prediction of elastomeric components. Such techniques involve various topics including material monotonic and cyclic deformation behaviors, proper knowledge of stress/strain histories, fatigue damage quantification parameters, efficient event identification methods, and damage accumulation rules. Elastomeric components are widely used in many applications, including automobiles due to their good damping and energy absorption characteristics. The type of loading normally encountered by these components in service is variable amplitude cyclic loading. Therefore, fatigue failure is a major consideration in their design and availability of an effective technique to predict fatigue life under complex loading is very valuable to the design procedure. In this work a fatigue life prediction methodology for rubber components is developed which is then verified by means of analysis and testing of an automobile cradle mount made of filled natural rubber. The methodology was validated with component testing under different loading conditions including constant and variable amplitude in-phase and out-of-phase axial-torsion experiments. The analysis conducted includes constitutive behavior representation of the material, finite element analysis of the component, and a fatigue damage parameter for life predictions. In addition, capabilities of Rainflow cycle counting procedure and Miner's linear cumulative damage rule are evaluated. Fatigue characterization typically includes both crack nucleation and crack growth. Therefore, relevant material deformation and fatigue properties are obtained from experiments conducted under stress states of simple tension and planar tension. For component life predictions, both fatigue crack initiation approach as well as fatigue crack growth approach based on fracture mechanics are presented. Crack initiation life prediction was performed using different damage criteria. The optimum method for crack initiation life prediction for complex multiaxial variable amplitude loading was found to be a critical plane approach based on maximum normal strain plane and damage quantification by cracking energy density on that plane. The fracture mechanics approach was used for total fatigue life prediction of the component based on specimen crack growth data and FE simulation results. Total fatigue life prediction results showed good agreement with experiments for all of the loading conditions considered.

Author: Yung-Li Lee
Publisher: Elsevier
ISBN: 0080477690
Category : Technology & Engineering
Languages : en
Pages : 417

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Book Description
Fatigue Testing and Analysis: Theory and Practice presents the latest, proven techniques for fatigue data acquisition, data analysis, and test planning and practice. More specifically, it covers the most comprehensive methods to capture the component load, to characterize the scatter of product fatigue resistance and loading, to perform the fatigue damage assessment of a product, and to develop an accelerated life test plan for reliability target demonstration. This book is most useful for test and design engineers in the ground vehicle industry. Fatigue Testing and Analysis introduces the methods to account for variability of loads and statistical fatigue properties that are useful for further probabilistic fatigue analysis. The text incorporates and demonstrates approaches that account for randomness of loading and materials, and covers the applications and demonstrations of both linear and double-linear damage rules. The reader will benefit from summaries of load transducer designs and data acquisition techniques, applications of both linear and non-linear damage rules and methods, and techniques to determine the statistical fatigue properties for the nominal stress-life and the local strain-life methods. - Covers the useful techniques for component load measurement and data acquisition, fatigue properties determination, fatigue analysis, and accelerated life test criteria development, and, most importantly, test plans for reliability demonstrations - Written from a practical point of view, based on the authors' industrial and academic experience in automotive engineering design - Extensive practical examples are used to illustrate the main concepts in all chapters

Author: Yung-Li Lee
Publisher: Elsevier
ISBN: 0123852056
Category : Technology & Engineering
Languages : en
Pages : 633

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Book Description
Understand why fatigue happens and how to model, simulate, design and test for it with this practical, industry-focused reference Written to bridge the technology gap between academia and industry, the Metal Fatigue Analysis Handbook presents state-of-the-art fatigue theories and technologies alongside more commonly used practices, with working examples included to provide an informative, practical, complete toolkit of fatigue analysis. Prepared by an expert team with extensive industrial, research and professorial experience, the book will help you to understand: - Critical factors that cause and affect fatigue in the materials and structures relating to your work - Load and stress analysis in addition to fatigue damage—the latter being the sole focus of many books on the topic - How to design with fatigue in mind to meet durability requirements - How to model, simulate and test with different materials in different fatigue scenarios - The importance and limitations of different models for cost effective and efficient testing Whilst the book focuses on theories commonly used in the automotive industry, it is also an ideal resource for engineers and analysts in other disciplines such as aerospace engineering, civil engineering, offshore engineering, and industrial engineering. - The only book on the market to address state-of-the-art technologies in load, stress and fatigue damage analyses and their application to engineering design for durability - Intended to bridge the technology gap between academia and industry - written by an expert team with extensive industrial, research and professorial experience in fatigue analysis and testing - An advanced mechanical engineering design handbook focused on the needs of professional engineers within automotive, aerospace and related industrial disciplines

Author: Jaime Tupiassú Pinho de Castro
Publisher: Createspace Independent Publishing Platform
ISBN: 9781530797042
Category :
Languages : en
Pages : 598

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Book Description
This second volume of the series describes strain-life approaches through the eN method, used when local plasticity at notch tips, where fatigue cracks typically originate, requires that the analysis follow the stress-strain behavior on a cycle-by-cycle basis. Such a low-cycle approach takes into account the elastoplastic material response, obtained from uniaxial stress-strain relations or multiaxial incremental plasticity calculations, including notch effects. Crack initiation under multiaxial non-proportional loads is also thoroughly discussed, with fatigue life predictions based either on high-cycle or low-cycle damage models.