186,247 research outputs found
Study of anelastic phenomena in materials of engineering interest
No full textMechanical spectroscopy (MS) studies absorption spectra of mechanical energy under the conditions of applied periodic external mechanical field, this technique is a powerful tool for the study of materials. In particular, it is shown that such a technique can help the mechanical characterisation of materials.
The elastic and anelastic properties of the material have been investigated by
using a vibrating reed technique with electrostatic excitation and frequency modulation detection of flexural vibrations mode of cantilevered mounted reed samples for a wide range of materials of engineering interest
Analyses Concerning Phenomena of Desire in Husserl’s Thought
No full textANALYSES CONCERNING PHAENOMENA OF DESIRE IN HUSSERL’S THOUGHT Starting from the analysis of a large group of long unpublished manuscripts, known as Studies on the Structure of Consciousness and recently published as volume XLIII of the complete works, this contribution aims at reconstructing some central elements in Husserlian analysis of the phenomena of the sphere of desire. These phenomena are an excellent example of the interweaving that concretely constitutes the life of consciousness: they are in fact distinct from the acts of feeling and volition, while maintaining structural connections with them. In particular, they are an expression of that peculiar intentional mode that Husserl defines as “taking part in things”, thanks to which the subject is involved in the dynamics of the world. In the dimension of desire, Husserl finds three distinct phenomena: simple whishing (Wünschen), desire in the strict sense (Begehren) and the drive feeling (Triebgefühl). All of them show, each in its own way, a common character, namely missing (vermissen), which reveals a lack or a deficiency in the emotional life of consciousness. In simply whishing, the subject remains in a feeling of lack, missing something not yet real and desiring something in the sense of simply wanting, without actively striving for it. On the contrary, desire in the strict sense implies that the lacking object is given as something that calls us strongly, driving us toward possession and appropriation. Finally, in the case of the drive feeling, there is a lack understood as a restlessness that gives rise to a drive movement or action, in which the tension is discharged.</jats:p
Recensione a: P. Natorp, Forma e materia dello spazio : dialogo con Edmund Husserl / (a cura di N. Argentieri)
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Long-term heat treatments on Ti6Al4V-SiCf Composite. Part II - Mechanical characterization
No full textTi6Al4V-SiCf composite, manufactured by Hot Isostatic Pressing (HIP) at Centro Sviluppo Materiali, has been submitted to long-term heat treatments (up to 1000 hours) at 400 and 600°C. The mechanical properties of the material, in as-fabricated condition and after heat treatments, have been investigated by instrumented indentation (FIMEC), dynamic modulus, tensile and fatigue tests. For comparison some experiments have been carried out also on the monolithic Ti6Al4V alloy. Results show that heat treatments, also the most severe examined here, do not produce remarkable variations of mechanical characteristics. In agreement with the microstructure examinations presented in part I, this behaviour, quite promising for future aeronautical applications, can be primarily ascribed to the stability of fibre-matrix interface. © (2009) Trans Tech Publications, Switzerland
Single crystal PWA 1483 superalloy: Dislocation rearrangement and damping phenomena
No full textThe structural stability of the single-crystal PWA 1483 superalloy has been investigated by internal friction (IF) and dynamic modulus measurements from room temperature to 1073 K. The examined samples were in the solubilized state. The vibrating reed technique with electrostatic excitation and frequency modulation detection of flexural vibrations has been employed. Frequency was similar to 350 Hz. IF spectra recorded in successive test runs on the same samples show a Q(-1) maximum (M1) above 623 K, whose intensity and position change from one run to another: in correspondence with M1 the modulus undergoes a slow decrease followed by a sudden increase. Sometimes another maximum (M2) has been observed at lower temperature (similar to 523 K). After each run the values of the modulus and of Q(-1) change indicating that a progressive irreversible transformation occurs. Damping phenomena have been attributed to the rearrangement of dislocation structures in the disordered matrix. This rearrangement modifies the density and the average distance of pinning points. This explanation is supported by transmission electron microscopy (TEM) observations. (C) 2009 Elsevier B.V. All rights reserved
Structural changes of liquid Pb-Bi eutectic alloy
No full textLiquid Pb–Bi eutectic (LBE) alloy has been selected as coolant and neutron spallation source for
the development of MYRRHA, an accelerator driven system (ADS).
The alloy has been characterized in liquid state from melting (125 °C) to 750 °C by mechanical
spectroscopy, i.e. internal friction (IF) and dynamic modulus measurements. The experiments have
been carried out using hollow reeds of austenitic stainless steel filled with Pb-Bi alloy and sealed at
the extremities. Dynamic modulus showed a remarkable drop in the range 350-520 °C.
In the same temperature range radial distribution functions (RDFs), determined from X-ray
diffraction patterns, evidenced variations of the mean distance between the 1st nearest neighbour
atoms. The phenomenon has been explained as a structural re-arrangement of atoms in the liquid
metal
Anelastic phenomena and Cr2N precipitation in a high nitrogen austenitic steel
No full textInternal friction (IF) and dynamic modulus measurements on a high nitrogen (0.8 wt%) austenitic
steel in the temperature range from room temperature to 800 °C have been carried out by using a
vibrating reed technique with electrostatic excitation and frequency modulation detection of flexural
vibrations in the frequency range of kHz.
The IF spectrum of the as-prepared material shows a broad peak superimposed to an exponentially
increasing background. The discontinuous precipitation of Cr2N phase changes the characteristics of
the peak. The results have been discussed by considering interstitial-substitutional (i-s) interactions
Elastic and anelastic behaviour of Ti6Al4V-SiCf composites produced by HIP and RDB
No full textThe Ti6Al4V-SiCf composite is a promising material for applications in aeronautical engines including turbine components. Sheets of Ti6Al4V-SiCf have been produced by two different routes: Hot Isostatic Pressing (HIP) and Roll Diffusion Bonding (RDB), a new process developed at C.S.M. This work reports the elastic and anelastic characterization of the materials carried out by internal friction (IF) and dynamic modulus experiments. IF spectra of HIP and RDB composites are similar. They exhibit a relaxation peak superimposed to an exponentially increasing background. The peak is due to C-Al and C-V pairs re-orientation in the phase matrix around the fibres. The background, is higher for the RDB composite owing to its higher dislocation density and smaller grain size. Long-term isothermal tests performed at different temperatures evidenced a progressive increase of the dynamic modulus E and decrease of the damping factor Q-1: higher the temperature greater the variation. According to the Granato-Lücke dislocation string model the phenomenon has been explained by considering the interstitial atoms diffusion to dislocations which progressively reduces the mean distance between pinning points
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