Wavelet-like analysis in the frequency-damping domain for modal parameters identification

Modal analysis and parametric model identification play a fundamental role in many fields, especially for the optimization and vibration control of civil structures and complex mechanical systems. In the last decades these techniques have been frequently applied for the development of innovative cutting tools and CNC machine tools. Although several methodologies are available in literature for parametric model identification, there is still a lack of an effective and robust algorithm. In this paper a new algorithm for automatic identification of a parametric model of a linear dynamic Single Input Single Output system with Multiple Degrees of Freedom is presented. Some recent approaches perform the Wavelet decomposition of the Impulse Response in the time-frequency domain. Here a Wavelet-like decomposition of the Frequency Response in the frequency-damping domain is introduced for vibration modes recognition. Afterwards, advanced statistical approaches are applied for vibration modes selection and model generation. The method was successfully tested on a complicated frequency response characterized by several vibration modes, which was obtained from experimental modal analysis performed on a circular saw blade

Influencia del homogeneizado previo al laminado en frío en la microestructura del AA3003

The aluminum alloy AA3003 produced by a direct chill continuous casting process has a microstructure that significantly affects its potential use in engineering applications. This work studies the effects of the homogenizing heat treatment on the microstructure of AA3003 with cold working. Six conditions were studied, combining the variables initial condition (with and without homogenizing) and amount of cold working. All conditions were evaluated by means of optical and scanning electron microscopy, in combination with backscattered electrons and energy dispersive X ray spectroscopy techniques. Results suggest that for both initial conditions, the secondary phases present are Al6(Mn,Fe) and ?-Al(Mn,Fe)Si, which vary in number, size, and shape. The homogenization caused the dissolution and precipitation of dispersoids, in addition to the spheroidization of primary particles, and minor variation of the size of secondary particles during cold working. Secondary phases are composed of primary and secondary particles, which differ in their Fe and Mn content, resulting in a lower Mn/Fe ratio for the primary particles (0,57 for the as?received condition and 0,80 for the homogenized condition), whereas the dispersoids have a higher Mn/Fe ratio (1,56 after the homogenization). Homogenization increased ductility and reduced the likelihood of cracking during cold working. This was evidenced by the results obtained for strength, hardness, and ductility.La aleación de aluminio AA3003 proveniente de colada continua posee una microestructura que afecta significativamente su uso potencial en aplicaciones de ingeniería. Este trabajo estudia los efectos de la homogeneización sobre la microestructura del AA3003 con trabajo en frío. Se estudiaron seis condiciones combinando las variables: condición inicial (con y sin homogeneizado) y cantidad de trabajo en frío. Se evaluaron todas las condiciones mediante microscopía óptica y electrónica de barrido, combinadas con técnicas de electrones retrodispersados y espectroscopía de dispersión de rayos X. Los resultados sugieren que, para ambas condiciones iniciales, las fases secundarias presentes son Al6(Mn,Fe) y ?-Al(Mn,Fe)Si. La homogeneización causó la disolución y precipitación de los dispersoides, la esferoidización de las partículas primarias y permitió que la variación del tamaño de las partículas secundarias fuese mínima durante el trabajo en frío. Además, se obtuvo que las fases secundarias están compuestas de partículas primarias y secundarias, que difieren en su contenido de Fe y Mn, lo que resulta en una relación Mn/Fe más baja para las partículas primarias (0,57 para la condición recibida y 0,80 para la condición homogeneizada), mientras que los dispersoides tienen una mayor relación Mn/Fe (1,56 después de la homogeneización). La homogenización aumentó la ductilidad y redujo la probabilidad de agrietamiento del material durante el trabajo en frío, lo cual se evidenció en los resultados obtenidos de resistencia, dureza y ductilidad

Innovative tool coatings for increasing tool life in milling Nickel-coated Nickel-Silver alloy

In the automotive market, there is a strong interest for the production of sidewinder keys made of Nickel-coated Nickel-Silver alloy. The Nickel coating improves wear resistance and brightness of the key, nevertheless it reduces the machinability and the tool life when milling the key groove is short. In this work, several innovative tool coatings were applied on conventional mills to enhance the machinability of Nickel-coated Nickel-Silver alloy. Tool life and burr formation obtained with the tested tools were investigated and discussed. Some of the coatings proved to be very promising for this application thank to their excellent tool life. Specifically, the PCD tool was the most interesting since the tool life was significantly longer than conventional carbide tool. \ua9 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license

Stability analysis in milling by taking into account the influence of forced vibrations on the actual tool-workpiece engagement conditions

n order to increase the material removal rate in milling, advanced cutting tools with complex geometry are typically applied under extreme cutting conditions which may trigger undesired chatter vibrations of the machining system. Recently some dynamic milling models were proposed in the literature which take into account the higher geometrical complexity of these tools. In these works, the tool-workpiece engagement conditions are computed from a purely geometric-kinematic analysis of the milling operation. Moreoever, they are kept constant throughout the stability analysis, independently from any possible increase of the axial depth of cut. In many cases the experimental validation of the proposed models is incomplete. In this work a novel methodology for assessing milling stability is presented, which is based on the correct linearization of the regenerative perturbations around the actual steady state forced vibrations. When the axial depth of cut is progressively increased, the resulting forced vibrations may cause a variation of each tooth-workpiece contact conditions, thus influencing the process dynamic behavior. This effect is more dominant when the degree of symmetry is poor as in the case of variable pitch cutters, when there is significant teeth runout, and when the average chip thickness is concurrently very small as in peripheral milling. The proposed approach for chatter prediction consists of an incremental linear stability analysis which does progressively adapt to the gradually increasing depth of cut up to the stability border. The concept was successfully verified with experimental cutting tests

Processed vs. non-processed biowastes for agriculture: effects of post-harvest tomato plants and biochar on radish growth, chlorophyll content and protein production

peer-reviewedThe aim of this work was to address the issue of processed vs. non-processed biowastes for agriculture, by comparing materials widely differing for the amount of process energy consumption. Thus, residual post harvest tomato plants (TP), the TP hydrolysates obtained at pH 13 and 60 degrees C, and two known biochar products obtained by 650 degrees C pyrolysis were prepared. All products were characterized and used in a cultivation of radish plants. The chemical composition and molecular nature of the materials was investigated by solid state C-13 NMR spectrometry, elemental analysis and potentiometric titration. The plants were analysed for growth and content of chlorophyll, carotenoids and soluble proteins. The results show that the TP and the alkaline hydrolysates contain lignin, hemicellulose, protein, peptide and/or amino acids moieties, and several mineral elements. The biochar samples contain also similar mineral elements, but the organic fraction is characterized mainly by fused aromatic rings. All materials had a positive effect on radish growth, mainly on the diameter of roots. The best performances in terms of plant growth were given by miscanthus originated biochar and TP. The most significant effect was the enhancement of soluble protein content in the plants treated with the lowest energy consumption non processed TP. The significance of these findings for agriculture and the environment is discussed.PUBLISHEDpeer-reviewe

The seismic sequence of 30 May - 9 June 2016 in the geothermal site of Torre Alfina (central Italy) and related variations in soil gas emissions

In the framework of a medium-enthalpy geothermal exploitation project, seismicity and soil gas emissions have been monitored in the area of Castel Giorgio-Torre Alfina since 2014. A dedicated local seismic network deepened the knowledge of the natural local seismicity in terms of source mechanisms, high-quality event localization and magnitude estimation. From November 2014 to May 2016, 846 seismic events were recorded, with a magnitude range of Md 0.1-2.8 and hypocentres 4-8 km depth. On 30th May 2016 a Mw 4.3 earthquake occurred near Castel Giorgio, followed by almost 1700 aftershocks; the moment tensor solution depicts a WNW-ESE oriented normal fault. An overview of the epicentral distributions since 2014, highlights that the active tectonic structures are NE-SW and WNW-ESE orientated. The diffuse soil CO2 flux is monitored since 2013 in six target areas located around the future production and reinjection wells, in order to assess the level of background natural degassing. In all target areas the maximum value of soil CO2 flux has been recorded during the 2016 seismic sequence. However, the values of δ13C of the emitted CO2 indicated a shallow biological origin of the gas. At Torre Alfina, the Solfanare natural gas emission, with a CO2 dominated gas, has same composition of the gas hosted in the geothermal reservoir. Here, high values of diffuse soil CO2 flux were recorded. During the 2016 seismic sequence, the Solfanare gas was continuously analysed by an automatic gas- chromatographic station. Results show that apart from small perturbations, no significant compositional variations were recorded. The significant contribution of CLVD and isotropic components suggest a possible opening of fluid cracks below the geothermal reservoir hosted in fractured Mesozoic limestones. The seismo-tectonic scenario indicates that the Solfanare fault was not activated. Kinematics and orientation of the activated faults suggest a relationship with the Bolsena caldera collapsePublishedNapoli, Italy1IT. Reti di monitoraggi

ELT-HIRES, the high resolution spectrograph for the ELT: results from the Phase A study

We present the results from the phase A study of ELT-HIRES, an optical-infrared High Resolution Spectrograph for ELT, which has just been completed by a consortium of 30 institutes from 12 countries forming a team of about 200 scientists and engineers. The top science cases of ELT-HIRES will be the detection of life signatures from exoplanet atmospheres, tests on the stability of Nature's fundamental couplings, the direct detection of the cosmic acceleration. However, the science requirements of these science cases enable many other groundbreaking science cases. The baseline design, which allows to fulfil the top science cases, consists in a modular fiber- fed cross-dispersed echelle spectrograph with two ultra-stable spectral arms providing a simultaneous spectral range of 0.4-1.8 μm at a spectral resolution of 100,000. The fiber-feeding allows ELT-HIRES to have several, interchangeable observing modes including a SCAO module and a small diffraction-limited IFU