Development of Resonant Ultrasound Spectroscopy for Determination of Material Properties of Solids at High Frequency PDF Download

Author: 鄭鴻輝
Publisher:
ISBN:
Category :
Languages : en
Pages : 95

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Author:
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ISBN:
Category :
Languages : en
Pages : 125

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The elastic properties of a solid are of considerable interest to both science and technology. Not only do they contain fundamental information about the nature of the inter-atomic bonding in the material, but they also determine the mechanical behavior of solids. In the past few years, considerable effort has been devoted to the study of elastic properties of bulk metallic glasses (BMGs), a relatively new class of metallic materials that display a unique combination of mechanical and physical properties. Our research has focused on Zr-based, Cu-based and Ca-based metallic glasses. Zr-based BMGs are known to have superior glass forming ability and high strength, but their ductility is too low for wide-spread practical applications. Cu-based BMGs recently received wide interest because of their low cost and good mechanical properties. Ca-based BMGs have low glass transition temperature T[subscript g], around 390 K, which make them very attractive to be studied near T[subscript g]. In this work, resonant ultrasound spectroscopy (RUS) has been applied to study the elastic properties of above mentioned BMGs from 5 K to their glass transition temperature T[subscript g]. RUS is a novel technique for determining the elastic moduli of solids, based on the measurement of the resonances of a freely vibrating body. In an RUS experiment, the mechanical resonances of a freely vibrating solid of known shape are measured, and an iteration procedure is used to "match" the measured lines with the calculated spectrum. This allows determination of all elastic constant of the solid from a single frequency scan. Below T[subscript g], the elastic constants of the BMGs under investigation show "normal" behavior, i.e. with increasing temperature, all moduli decrease and Poisson ratio increases. Above T[subscript g] changes in the trends occur due to structural relaxation and crystallization. We confirmed the suggested link between ductility and Poisson ratio: BMGs showing good ductility display high Poisson ratio. By increasing palladium content in Zr50Cu40-[subscript x]Al10Pd[subscript x] alloys, BMGs with high Poisson ratio and thus good ductility have been obtained. In addition, we developed a simple model to provide fast and good estimate of the temperature dependence of elastic constants of BMGs from room temperature measurements.

Author: Gautham Manoharan
Publisher:
ISBN:
Category :
Languages : en
Pages : 67

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The objective of this thesis is to validate Resonant Ultrasound Spectroscopy (RUS) as a non-destructive evaluation tool that can be used to study effects of radiation on the mechanical properties of a material, mainly its elastic constants. RUS involves experimentally measuring the resonant frequencies of a sample and calculating the elastic constants based on these measurements. Finite Element Method (FEM) is used to get the frequencies of the modes of free vibration for the sample model. This result depends on the elastic constant values used in the FEM simulation. Studies were conducted to confirm the accuracy of the FEM model, and determine the right configuration and parameters to use for the simulation. Assuming uniform and isotropic elastic property changes, the effects of radiation damage can be quantified by obtaining a set of matching resonant frequencies between the experimental and FEM simulation results, before and after irradiating the sample. This is done by adjusting the elastic constant values used in the simulation so that the results match with the experimentally obtained resonant frequencies. With powerful enough equipment, even real time monitoring is possible in harsh environments, thus pointing out imminent failure.

Author: Albert Migliori
Publisher: Wiley-VCH
ISBN:
Category : Medical
Languages : en
Pages : 224

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This first procedural guide to RUS, Resonant Ultrasound Spectroscopy offers a clear step-by-step tutorial, from developing a preliminary set of resonances to final determination of moduli. The book also contains intermediate computer outputs showing where mistakes are made, how to spot them, and how to remeasure to correct problems. Also a complete reference to the language of RUS, this book is full of clear explanations of every variable, concept, and hard-to-find term currently in use.

Author: 周鴻儒
Publisher:
ISBN:
Category :
Languages : en
Pages : 134

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Author: Abu Rafi Mohammad Iasir
Publisher:
ISBN:
Category :
Languages : en
Pages : 71

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The purpose of this thesis is to study Resonance Ultrasound Spectroscopy(RUS) and it's potential to evaluate the change in interfacial thermal resistance due to irradiation. Resonant Ultrasound Spectroscopy is conventionally used to determine the material properties of elastic bodies. It is a nondestructive technique that is very capable of extracting the elastic constants for a complete anisotropic material. Finite Element Method(FEM) is used to determine the natural frequency of a hollow cylinder. FEM was used due to the shape of the object. An experimental system was developed to capture the resonant frequencies of a hollow cylinder which is similar to Molybdenum-99 target. After successfully determining the resonance frequencies from the spectra, the frequencies were inverted to the elastic constants using the finite element model. Radiation effects on elastic constants was also studied. An investigation was made to assess the usefulness of RUS in evaluating radiation damage of materials. An experimental study was also completed to analyze the differences in RUS spectra in a contact pressure analysis between two cylinders of Molybdenum-99 target.

Author:
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Category : Aeronautics
Languages : en
Pages : 488

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Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 10

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All objects exhibit vibrational resonances when mechanically excited. These resonant frequencies are determined by density, geometry, and elastic moduli. Resonant ultrasound spectroscopy (RUS) takes advantage of the known relationship between the parameters. In particular, for a freely suspended object, with three of the four parameters (vibrational spectra, density, geometry, or elastic moduli) known the remaining one can be calculated. From a materials characterization standpoint it is straight-forward to measure density and geometry but less so to measure all the elastic moduli. It has recently become possible to quickly and accurately measure vibrational spectra, and using code written at Los Alamos, calculate all the elastic moduli simultaneously. This is done to an accuracy of better than one percent for compression and 0.1 percent for shear. RUS provides rapid acquisition of materials information here-to-fore obtainable only with difficulty. It will greatly facilitate the use of real materials properties in models and thus make possible more realistic modeling results. The technique is sensitive to phase changes and microstructure. This offers a change to input real data into microstructure and phase change models. It will also enable measurement of moduli at locations in and about a weld thus providing information for a validating coupled thermomechanical calculations.

Author: Samuel A. Lippert
Publisher:
ISBN:
Category :
Languages : en
Pages : 574

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Author: National Science and Technology Council (U.S.). Materials Technology Subcommittee
Publisher:
ISBN:
Category : Government publications
Languages : en
Pages : 204

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