Chatter stability analysis of variable speed milling with helix angled cutters

The number of factors considered in the establishing of chatter model for regenerative chatter would directly affect the accuracy of numerical analysis. In this paper, considering the helix angle of cutter, the establishment method of three degrees of freedom complex model is investigated synthetically. An improved semi-discretization method is adopted for the prediction of milling stability of variable speed milling with helix angle. The influences of milling cutter helix angle, radial immersion rate and variable speed modulation coefficient on chatter suppression in milling process are studied. The results show that the selection of milling cutters with different helix angles has a certain influence on the overall chatter stability, especially the effect cannot be ignored under local special machining conditions. Excessive radial immersion rate will increase the probability of chatter. Compared with constant speed milling, the chatter can be suppressed obviously by variable speed milling, and the selection of variable speed modulation coefficient will directly affect the suppression effect of chatter.

NEW APPROACHES IN MULTI-SHAFT GEAR DRIVES VIBRATION DIAGNOSTICS

Presented studies are aimed at developing of new and improving of existing methods of vibration signal analysis to detect local gears damages during their operating.The new method of calculating the modulation coefficient showed low sensitivity to the place of mounting of the vibration sensor and makes it possible to use in the absence of information about the vibration activity of the gear drive in the previous workable condition.A technique for designing and using unique wavelets was developed. The technique reflects the specifics of real processes in the interaction of meshing teeth and adapted for gears vibration analysis. Using of unique wavelets can noticeably increase the wavelet coefficients sensitivity to changes in gears condition.

A New Three-Dimension Deceptive Scene Generation against Single-Pass Multibaseline InSAR Based on Multiple Transponders

The interferometry synthetic aperture radar (InSAR) deceptive jamming method utilizing two synergetic transponders can generate a false three-dimension (3D) scene in a single baseline InSAR image. However, such deceptive capability could be reduced by the multibaseline InSAR system. To obtain effective deception on multibaseline InSAR, a novel deceptive scene generation method jointly employing multiple transponders is proposed. It only demands that each transponder is modulated with a complex coefficient when generating a false point. The complex modulation coefficient can be offline calculated according to the deceptive point coordinate by solving a matrix. Besides, the complex modulation coefficient can be combined with the deceptive scene template, and thus a large 3D deceptive scene is able to be created quickly in the multibaseline InSAR image by using the fast two-dimension (2D) SAR deceptive scene generation algorithm. As long as the number of transponders is not less than the number of antennas of the multibaseline InSAR system, this proposed method is effective. The effectiveness of the proposed method is validated by computer simulations.

Amplitude modulation between multi-scale turbulent motions in high-Reynolds-number atmospheric surface layers

Long-term measurements were performed at the Qingtu Lake Observation Array site to obtain high-Reynolds-number atmospheric surface layer flow data ($Re_{\unicode[STIX]{x1D70F}}\sim O(10^{6})$). Based on the selected high-quality data in the near-neutral surface layer, the amplitude modulation between multi-scale turbulent motions is investigated under various Reynolds number conditions. The results show that the amplitude modulation effect may exist in specific motions rather than at all length scales of motion. The most energetic motions with scales larger than the wavelength of the lower wavenumber peak in the energy spectra play a vital role in the amplitude modulation effect; the small scales shorter than the wavelength of the higher wavenumber peak are strongly modulated, whereas the motions with scales ranging between these two peaks neither contribute significantly to the amplitude modulation effect nor are strongly modulated. Based on these results, a method of decomposing the fluctuating velocity is proposed to accurately estimate the degree of amplitude modulation. The corresponding amplitude modulation coefficient is much larger than that estimated by establishing a nominal cutoff wavelength; moreover, it increases log-linearly with the Reynolds number. An empirical model is proposed to parametrize the variation of the amplitude modulation coefficient with the Reynolds number and the wall-normal distance. This study contributes to a better understanding of the interaction between multi-scale turbulent motions and the results may be used to validate and improve existing numerical models of high-Reynolds-number wall turbulence.

Analysis of surface properties of Ti-Cu-Ox gradient thin films using AFM and XPS investigations

The paper presents results of investigations on surface properties of transparent semiconducting thin films based on (Ti-Cu)oxide system prepared using multi-magnetron sputtering system. The thin films were prepared using two programmed profiles of pulse width modulation coefficient, so called V- and U-shape profiles. The applied powering profiles allowed fabrication of thin films with gradient distribution of Ti and Cu elements over the thickness of deposited layers. Optical investigations allowed determination of transparency of prepared films that reached up to 60 % in the visible part of optical radiation, which makes them attractive for the transparent electronics domain. Surface properties investigations showed that the surface of mixed (Ti-Cu)oxides was sensitive to adsorption, in particular to carbon dioxide and water vapor. Soft etching with argon ions resulted in surface cleaning from residuals, however, deoxidation of Cu-oxide components was also observed.