Literature on ECAP generally deals with room temperature or high-temperature deformation regimes. Very few data on low-temperature SPD processes have been published. This study presents some ...experimental results on the effect of cryogenic treatment prior to ECAP-BC on microstructure modification, mechanical response, and corrosion behaviour of an AA6012 Al-Mg-Si-Pb alloy. This type of Pb-bearing AA6000-series alloy, is produced and used for its marked post-extrusion machinability. The mechanical properties were inferred by nanoindentation to measure hardness, H, and local elastic modulus, Er. These data were presented in form of maps to account for the whole H and Er evolution with cumulative strain. The experimental results showed significant microstructure differences between the cryogenic treated ECAP condition and the conventional ECAP at room temperature. These differences were also correlated with electron microscopy inspections, XRD. Finally, the cryogenic treatment prior ECAP also affected the alloy corrosion behaviour.
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In order to reduce the suspension thermal noise, the second generation GW interferometric detectors will employ monolithic suspensions in fused silica to hold the mirrors. The fibres are produced by ...melting and pulling apart a fused silica rod, obtaining a long thin wire with two thicker heads. The dynamics of such a fibre is in principle different from that of a cylindrical, regular fibre, because most of the deformation energy is stored in the neck region where the diameter is variable. This is an advantage, since adjusting the neck tapering, a thermoelastic noise cancellation effect can be obtained. Therefore, a careful study of the suspensions behavior is necessary to estimate the overall noise and to optimize the control strategy. To simplify the control design, a simple three segment model for the silica fibres has been developed, fully equivalent to the beam equation at low frequencies. The model, analytically proved for a regular cylindrical fibre, can be extended to a fibre with tapered necks, provided that the equivalent bending length is suitably measured. We developed a tool to measure the position of the bending point for each fibre, thus allowing to experimentally check the validity of the model. A numerical code has been written to solve the beam equation for wires with varying diameter. This code confirms the validity of the three segment model. Moreover, it is possible to extend the solution to higher frequencies thus computing the transfer function and the energy distribution of the suspension system and estimating the thermal noise contribution.
The quest for gravitational waves from coalescing binaries is customarily performed by the LIGO-Virgo collaboration via matched filtering, which requires a detailed knowledge of the signal. Complete ...analytical coalescence waveforms are currently available only for the non-precessing binary systems. In this paper we introduce complete phenomenological waveforms for the dominant quadrupolar mode of generically spinning systems. These waveforms are constructed by bridging the gap between the analytically known inspiral phase, described by spin Taylor (T4) approximants in the restricted waveform approximation, and the ring-down phase through a phenomenological intermediate phase, calibrated by comparison with specific, numerically generated waveforms, describing equal mass systems with dimension-less spin magnitudes equal to 0.6. The overlap integral between numerical and phenomenological waveforms ranges between 0.95 and 0.99.
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