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A Theoretical Investigation of the Influence of Powertrain Mounts on Transmission Torsional Dynamics
No full textThis paper investigates the effect of the powertrain mounting system on the linear and nonlinear torsional dynamical behaviour of a transmission system. To this aim, two dynamic models, one with rigid mounts and the other with flexible mounts, are presented and compared: the first model considers only the torsional dynamics of transmission and driveline, while the second model includes also a 3 degrees-of-freedom powertrain block. The mechanical coupling and interaction between the powertrain block and transmission system is discussed and formulated. These models are then analyzed in terms of vibrational mode shapes, natural frequencies and Frequency Response Functions (FRFs); a sensitivity analysis of the main transmission parameters, e.g. the gear ratio, is also presented. From the comparison of the two simulated configurations (with and without powertrain mounts) both in time and frequency domain, a significant interaction between the two subsystems is noticed, particularly in the vehicle acceleration signal. Neglecting the powertrain mounts may lead to underestimating the real vibration level. A nonlinear model of a dual clutch transmission, including the main backlashes present along the transmission path (clutch spline, gear meshes, synchronizers), is coupled to the powertrain mounting system model. Finally, the effect of mount stiffness on transmission NVH during critical manoeuvres is shown
Low-loss micro-resonator filters fabricated in silicon by CMOS-compatible lithographic techniques: Design and characterization
No full textOptical resonators are fundamental building-blocks for the development of Si-photonics-integrated circuits, as tunable on-chip optical filters. In addition to the specific spectral shape, which may vary according to a particular application, extremely low losses from these devices are a crucial requirement. In the current state-of-the-art devices, most low-loss filters have only been demonstrated by exploiting ad hoc lithographic and etching techniques, which are not compatible with the standard CMOS (complementary metal-oxide semiconductor) process-flow available at Si-photonic foundries. In this paper, we describe the design and optimization of optical micro-resonators, based on Si-waveguides with a height lower than the standard ones (i.e., less than 220 nm), prepared on SOI (silicon on insulator) platform, which allow the realization of high-performance optical filters with an insertion loss lower than 1 dB, using only previously validated lithographic etch-depth
Calibration of a robotized bending system
No full textThe paper describes a method to identify the mechanical inaccuracies which may be present in the swinging unit of a robotized bending system. The method allows calculating the corrections that must be provided to the control system to compensate the mechanical inaccuracies. Finally, the procedure has been applied to a real bending system and the results are presented
Ultrasonic enhanced limestone dissolution: Experimental and mathematical modeling
No full textStricter emission regulations require the improvement of SO2 scrubbing efficiency and energy usage. In this work, the dissolution of two very pure limestone samples under the effect of ultrasound (US) was compared to their dissolution in silent conditions. The aim of this work was to assess experimentally whether this method could be adopted as a process intensification technique for Wet Flue Gas Desulfurization (WFGD) applications. A pH-stat method with vigorous agitation, coupled with in situ particle size distribution measurements was developed for evaluating the effect of US in limestone dissolution. The samples were characterized in detail, the experiments were modeled mathematically and, a chemical reaction constant was determined and used to compare quantitatively the use of US and the silent case. The results indicate that US does enhance limestone dissolution, and that the degree of enhancement depends largely on the type of sample, i.e. the geological origin and the particle size. The developed mathematical model was implemented satisfactorily; the model was able to fit the data with high degrees of accuracy (>94%). The degree of enhancement, quantified in terms of the increase in the estimated chemical reaction constant, ranged from 18% to 150%
Numerical modelling of out-of-plane response of infilled frames: State of the art and future challenges for the equivalent strut macromodels
No full textInfill-frame interaction constitutes a still open question both in research and in practicing engineering. Computational models used to predict this interaction are, in most cases, addressing the estimation of the response of the infilled frames when subjected to actions parallel to their plane. However, the observation of the post-earthquake damage has demonstrated that infills, weakened by the in-plane actions, may fail out-of-plane increasing the risks associated to the earthquake scenarios. In spite of this, different studies have shown that infills, if properly designed and supported by the frame, exhibit a significant strength and displacement capacity when called to resist to out-of-plane actions, offering the possibility to develop an arching mechanism in their deformed configuration. The prediction of the combined inplane out-of-plane response prefigures the new goal of the seismic assessment of masonry infilled frames. This paper presents an in-depth literature review of the capacity models developed for the prediction of the out-of-plane response of infilled frames, from the first flexural based computational models to the models implementing the arching action theory in their formulation. A comparison between the results obtainable is provided in order to compare the models reliability against the results of different experimental tests. A final discussion is devoted to the effectiveness the recent integrated in-plane/out-of-plane macromodels used in 3D structural models. A new promising approach, based on the use nonlinear fibersection elements, is also outlined providing a numerical testing of the capacity of such elements to naturally account for the out-of-plane arching mechanism
CONTROLLING SOFT TISSUE ADHESION ON TITANIUM SURFACES BY NANOGROOVES AND KERATIN NANOFIBRES
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Finite fracture mechanics predictions on the apparent fracture toughness of as-quenched Charpy V-type AISI 4340 steel specimens
No full textMagnetic loss versus frequency in non-oriented steel sheets and its prediction: minor loops, PWM, and the limits of the analytical approach
No full textThe Pulse Width Modulation (PWM) technique is commonly used to supply modern high-speed electrical machines. The fundamental frequency is typically in the kilohertz range, with switching frequencies of several tens of kilohertz, as determined by the new SiC or GaAs based power transistors modules. Switching introduces minor loops in the major hysteresis cycle, with durations of the order of 100 μs or lower, with the resulting magnetization dynamics influenced by strong skin effect. However, since these minor loops have relatively small amplitude, their constitutive equation may be described by an equivalent permeability (real or complex), depending on the mean slope of the minor loop and its static energy loss. By retrieving this permeability, the classical loss is straightforwardly calculated by analytical solution of the Maxwell's equations. In this work, we measure and calculate, according to the quasi-linear approximation for the minor loops, the magnetic energy losses of 0.194 mm thick non-oriented Fe-Si 3.2% sheets subjected to PWM induction waveform. Minor loop peak amplitudes ranging between 50 mT and 0.2 T and frequencies up to 10 kHz are investigated. The results are consistent with the proposed model, to within 5%