1,721,205 research outputs found
Recent developments and selected patents on vibration based methods for the elastic characterization of isotropic materials
No full textA detailed knowledge of the basic engineering material properties is of fundamental importance for fabrication purpose as well as for proper design and reliability estimation of any kind of engineering structure. In particular, knowledge of elastic properties, such as Young's Modulus and Poisson's Ratio allows to assess the static and/or dynamic performances of a structure and provides information on the quality achieved during the fabrication process. Various methodologies have been proposed through the years for the elastic characterization of engineering materials. Vibrationbased methods allow to determine the material properties combining experimentally measured natural frequencies of suitable samples to analytical or numerical models relating the natural frequencies to the geometrical dimensions, mass density and the unknown elastic properties. Vibration-based methods are today commonly employed because of the nondestructive nature of frequency measurements and the simple operating procedures involved. The efforts provided by research scientists and engineers in this field are currently enclosed in a huge number of meaningful journal papers and patents devoted to the subject. The aim of the present work is to review recent progresses and selected patents in the field of vibration based methods for the elastic characterization of isotropic materials. © 2009 Bentham Science Publishers Ltd
Fatigue analysis of adhesive joints with laser treated substrates
Full text linkAbstractRecent literature works focused on the analysis of laser irradiation on the strength of adhesive joints under quasi-static loading conditions. It has been demonstrated that laser surface preparation allows to remove impurity and weak boundary layers from the mating substrates and, depending on the energy density, it is also able to modify surface morphology promoting mechanical interlocking. In previous works, the authors assessed the effect of Yb-fiber laser ablation over the quasi-static strength and toughness, of aluminum and stainless steel adhesively bonded joints. The experimental results demonstrated the ability of laser irradiation to improve the mechanical properties of the joints. The aim of this work is to extend the scope of previous investigations to fatigue loading. Double Cantilever Beam (DCB) samples with laser treated aluminum substrates have been bonded with a two component epoxy adhesive. For comparison standard degreasing and grit blasting have been also deployed for samples preparation. The results have been compared in terms of cycles to failure and the fracture surfaces have been analyzed by means of Scanning Electron Microscopy (SEM) in order to investigate the mechanism of failure
An inverse procedure for determining the material constants of isotropic square plates by impulse excitation of vibration
No full textThe paper presents a procedure whereby the Poisson's ratio and dynamic Young's modulus of isotropic and homogeneous materials are determined using two of the first four frequencies of natural vibration in thin square plates. The procedure is based on suitable approximate relationships relating the resonant frequencies to the elastic constants of the material. These relations were derived from an extensive series of numerical analysis carried out by a finite element code. To measure the fundamental resonant frequencies, inexpensive computerized equipment is proposed. The procedure has been validated on Carbon Steel specimens
A procedure for determining the elastic constants of isotropic materials by modal vibration testing of rectangular thin plate
No full textThe paper presents a procedure whereby the Poisson's ratio and the dynamic Young's modulus of isotropic and homogeneous materials are determined using two of the first four frequencies of natural vibration in thin rectangular plates. The procedure is based on suitable approximate relationships, relating the resonance frequencies to the elastic constants of the material. These relations were derived from the Warburton's ones by taking into account for a correction factor obtained by an extensive numerical analysis carried out by a finite element code. In order to verify the procedure, a comparison with reference solutions has been made
Pertussis toxin (PTX) and its non-toxic Derivatives as vaccine adjuvant and microbicides
No full textSimulating fracture in bonded composite joints using cohesive zone models
No full textThe cohesive zone model (CZM) is a powerful tool for the simulation of fracture in bonded assemblies. In this chapter the CZM is used to study the enhancement of bond toughness in adhesive joints with laser-irradiated substrates. The chapter first discusses the implementation of an interface element, incorporating the Park-Paulino-Roesler (PPR) potential-based cohesive model, in the framework of a finite element commercial code (ABAQUS Standard). The PPR model is then applied to the simulation of debonding in T-peel joints with laser-treated substrates when these undergo failure with large plastic deformations. © 2011 Woodhead Publishing Limited. All rights reserved
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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