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Fatigue

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Full-Text Articles in Engineering Science and Materials

3d Printing Of 316l Stainless Steel And Its Effect On Microstructure And Mechanical Properties, Rawn Penn Oct 2017

3d Printing Of 316l Stainless Steel And Its Effect On Microstructure And Mechanical Properties, Rawn Penn

Graduate Theses & Non-Theses

Laser powder bed fusion or 3D printing is a potential candidate for net shape forming and manufacturing complex shapes. Understanding of how various parameters affect build quality is necessary. Specimens were made from 316L stainless steel at 0°, 30°, 60°, and 90° angles measured from the build plate. Three tensile and four fatigue specimens at each angle were produced. Fracture morphology investigation was performed to determine the fracture mode of specimens at each build angle. Microstructural analysis was performed on one of each orientation. The average grain size of the samples was marginally influenced by the build angle orientation. Tensile ...


Peridynamic Models For Fatigue And Fracture In Isotropic And In Polycrystalline Materials, Guanfeng Zhang May 2017

Peridynamic Models For Fatigue And Fracture In Isotropic And In Polycrystalline Materials, Guanfeng Zhang

Mechanical (and Materials) Engineering -- Dissertations, Theses, and Student Research

To improve design and reliability, extensive efforts has been devoted to understanding damage and failure of materials and structures using numerical simulation, as a complement of theory and experiment. In this thesis, peridynamics is adopted to study fatigue and dynamic failure problems.

Fatigue is a major failure mode in engineering structures. Predicting fracture/failure under cyclic loading is a challenging problem. Classical model cannot directly be applied to problems with discontinuities. A peridynamic model is adopted in this work because of important advantages of peridynamics in allowing autonomous crack initiation and propagation. A recently proposed peridynamic fatigue crack model is ...


Electrically Induced Strain And Polarization Fatigue In Lead-Free Ceramics, Daniel Sommer Jan 2017

Electrically Induced Strain And Polarization Fatigue In Lead-Free Ceramics, Daniel Sommer

Graduate Theses and Dissertations

Piezoelectric ceramics have traditionally been used in commercial applications such as actuators and sensors. By far the most popular piezoceramics currently in use are Pb(Zr,Ti)O3-based (PZT) ceramics. PZT ceramics are able to produce large strain and polarization with the application of an electric field, and this is due to the Morphotropic phase boundary (MPB). A MPB is associated with the boundary between tetragonal and rhombohedral perovskite phases. A disadvantage of PZT ceramics is that they contain ≥ 60 wt. % of lead. Since lead is toxic, this poses an environmental and health hazard because lead is released into the ...


Fatigue Analysis Of The Welded Region In The Automotive Torsion Beam Rear Suspension System, Nan Zhan, Xiaochuan Zhang Oct 2016

Fatigue Analysis Of The Welded Region In The Automotive Torsion Beam Rear Suspension System, Nan Zhan, Xiaochuan Zhang

The 8th International Conference on Physical and Numerical Simulation of Materials Processing

No abstract provided.


Fatigue Properties Of Magnetorheological Elastomers And The Design Of Interfacial Layers To Improve Fatigue Life., Yanfen Zhou Jan 2016

Fatigue Properties Of Magnetorheological Elastomers And The Design Of Interfacial Layers To Improve Fatigue Life., Yanfen Zhou

Doctoral

The primary aim of this PhD programme was to understand the fatigue behaviour of magnetorheological elastomers (MREs) and provide a reliable fatigue life predictor for this class of materials. To realise this aim required the study of the dynamic behaviour of MREs using the equi-biaxial bubble inflation test method. Isotropic and anisotropic MREs were fabricated from silicone rubber (SR) filled with soft carbonyl iron (CI) particles. The equi-biaxial fatigue behaviour of these samples was determined using a bubble inflation method. Wöhler (S-N) curves for both isotropic and anisotropic MREs were produced by subjecting the compounds to cycling over a range ...


Electromechanical Coupling Behavior Of Dielectric Elastomer Transducers, Jianyou Zhou Sep 2015

Electromechanical Coupling Behavior Of Dielectric Elastomer Transducers, Jianyou Zhou

Electronic Thesis and Dissertation Repository

Dielectric elastomer transducers with large deformation, high energy output, light weight and low cost have been drawing great interest from both the research and industry communities, and shown potential for versatile applications in biomimetics, dynamics, robotics and energy harvesting. However, in addition to multiple failure modes such as electrical breakdown, electromechanical instability, loss-of-tension and fatigue, the performance of dielectric elastomer transducers are also strongly influenced by the hyperelastic and viscoelastic properties of the material. Also, the interplay among these material properties and the failure modes is rather difficult to predict. Therefore, in order to provide guidelines for the optimal design ...


Effects Of Alloying Elements On The Microstructure And Fatigue Properties Of Cast Iron For Internal Combustion Engine Exhaust Manifolds, David Jon Eisenmann Jan 2015

Effects Of Alloying Elements On The Microstructure And Fatigue Properties Of Cast Iron For Internal Combustion Engine Exhaust Manifolds, David Jon Eisenmann

Graduate Theses and Dissertations

In the design of exhaust manifolds for internal combustion engines the materials used must exhibit resistance to corrosion at high temperatures while maintaining a stable microstructure. Cast iron has been used for manifolds for many years by auto manufacturers due to a combination of suitable mechanical properties, low cost, and ease of casting. Over time cast iron is susceptible to microstructural changes, corrosion, and oxidation which can result in failure due to fatigue. This thesis seeks to answer the question: “Can observed microstructural changes and measured high temperature fatigue life in cast iron alloys be used to develop a predictive ...


Design And Development Of High-Performance Lead-Free Piezoelectric Ceramics, Xiaoming Liu Jan 2015

Design And Development Of High-Performance Lead-Free Piezoelectric Ceramics, Xiaoming Liu

Graduate Theses and Dissertations

Piezoelectric ceramics have been widely used in the commercial applications of actuators, sensors, etc. Nowadays, Pb(Zr,Ti)O3-based (PZT) ceramics, which contain ≥ 60 wt.% of lead, dominate the market due to their excellent electromechanical properties. The large electric field induced polarization and strain developed in PZT piezoceramics are intimately related to the morphotropic phase boundary (MPB). This has been attributed to the coexistence of tetragonal and rhombohedral perovskite phases. However, toxic lead severely threatens the environment and human health, as a significant amount of lead is released into the air during the fabrication and disposal. Thus, there is an ...


Detailed Finite Element Analysis And Preliminary Study Of The Effects Of Friction And Fastener Pre-Tension On The Mechanical Behavior Of Fastened Built-Up Members, Francisco Javier Bonachera Martin Apr 2014

Detailed Finite Element Analysis And Preliminary Study Of The Effects Of Friction And Fastener Pre-Tension On The Mechanical Behavior Of Fastened Built-Up Members, Francisco Javier Bonachera Martin

Open Access Theses

The characterization of fatigue resistance is one of the main concerns in structural engineering, a concern that is particularly important in the evaluation of existing bridge members designed or erected before the development of fatigue design provisions. The ability of a structural member to develop alternate load paths after the failure of a component is known as member-level or internal redundancy. In fastened built-up members, these alternate load paths are affected by the combination of fastener pre-tension and friction between the structural member components in contact. In this study, a finite element methodology to model and analyze riveted and bolted ...


A Quantitatively Accurate Theory Of Stable Crack Growth In Single Phase Ductile Metal Alloys Under The Influence Of Cyclic Loading, Peter Huffman Jan 2014

A Quantitatively Accurate Theory Of Stable Crack Growth In Single Phase Ductile Metal Alloys Under The Influence Of Cyclic Loading, Peter Huffman

Graduate Theses and Dissertations

Although fatigue has been a well studied phenomenon over the past century and a half, there has yet to be found a quantitative link between fatigue crack growth rates and materials properties. This work serves to establish that link, in the case of well behaved, single phase, ductile metals. The primary mechanisms of fatigue crack growth are identified in general terms, followed by a description of the dependence of the stress intensity factor range on those mechanisms. A method is presented for calculating the crack growth rate for an ideal, linear elastic, non-brittle material, which is assumed to be similar ...


Fatigue Testing And Data Analysis Of Welded Steel Cruciform Joints, Alina Shrestha May 2013

Fatigue Testing And Data Analysis Of Welded Steel Cruciform Joints, Alina Shrestha

University of New Orleans Theses and Dissertations

In this study, ABS Publication 115, “Guidance on Fatigue Assessment of Offshore Structures” is briefly reviewed. Emphasis is on the S-N curves based fatigue assessment approach of non-tubular joints, and both size and environment effects are also considered. Further, fatigue tests are performed to study the fatigue strength of load-carrying and non-load-carrying steel cruciform joints that represent typical joint types in marine structures. The experimental results are then compared against ABS fatigue assessment methods, based on nominal stress approach, which demonstrates a need for better fatigue evaluation parameter. A good fatigue parameter by definition should be consistent and should correlate ...


Creep, Fatigue And Creep-Fatigue Interactions In Modified 9% Cr - 1% Mo (P91) Steels, Valliappa Kalyanasundaram May 2013

Creep, Fatigue And Creep-Fatigue Interactions In Modified 9% Cr - 1% Mo (P91) Steels, Valliappa Kalyanasundaram

Theses and Dissertations

Grade P91 steel, from the class of advanced high-chrome ferritic steels, is one of the preferred materials for many elevated temperature structural components. Creep-fatigue (C-F) interactions, along with oxidation, can accelerate the kinetics of damage accumulation and consequently reduce such components' life. Hence, reliable C-F test data is required for meticulous consideration of C-F interactions and oxidation, which in turn is vital for sound design practices. It is also imperative to develop analytical constitutive models that can simulate and predict material response under various long-term in-service conditions using experimental data from short-term laboratory experiments. Consequently, the major objectives of the ...


A Critical Assessment Of The High Cycle Bending Fatigue Behavior Of Boron-Modified Ti-6al-4v, Casey M. Holycross Jan 2010

A Critical Assessment Of The High Cycle Bending Fatigue Behavior Of Boron-Modified Ti-6al-4v, Casey M. Holycross

Browse all Theses and Dissertations

Boron-modified Ti-6Al-4V alloys have shown increased performance in mechanical properties over unmodified alloys and are currently of interest for use in turbine engine applications. These alloys offer up to 40% increase in ultimate tensile strength, up to 30% increase in stiffness, and favorable damage characteristics while maintaining a ductility greater than 10%. These attractive properties are attributed to small additions of boron that refine the microstructure and form strong and stiff TiB whiskers. Previous research has found that these modified alloys compare favorably in fatigue. Samples machined from a powder-metallurgy forging with nominal composition Ti-6Al-4V-1B, were tested in fully-reversed bending ...