Investigation of vibratory drilling model with adaptive control. Part 2: mixed control of peak-to-peak vibration displacement and cutting continuity index

Chip segmentation is important condition for deep drilling efficiency improving. Chip segmentation could be ensured by sustaining stable axial self-excited vibrations of a drill. Vibrations are excited by regenerative effect when cutting edges move along the surface formed by previous passes. The conditions required for reliable chip segmentation could be created by using of a special vibratory head with an elastic element, providing tool additional axial flexibility. To maintain stable vibro-process with amplitude sufficient for chip segmentation, it’s suggested to use the vibratory head with a special actuator for adaptive feedback control proportional to a tool vibration velocity. Two algorithms of the feedback gain adaptation are proposed in the present paper: the adaptation by peak-to-peak displacement and the mixed adaptation by peak-to-peak displacement with cutting continuity index. The investigation of effectiveness of the proposed algorithms applicable to the model, described in [9], is also presented

Dynamic fracture in carbon-fibre composites: Effect of steel and ice projectiles

In this study the resultant ballistic dynamic response observed in a 2x2 twill weave T300 carbon fibre/epoxy composite flat-plate specimen is examined, using a combination of non-invasive analysis techniques. The study investigates deformation, damage and fracture following the impacts with both solid (steel) and fragmenting (ice) projectiles travelling with velocities of 70-90 m/s and 300-500 m/s, respectively. Digital image correlation was employed to obtain displacement data for the rear surfaces of the specimens in each experiment, and used to assess the effect of impact velocity and projectile material on the specimen’s response. 3D X-ray computed tomography was used to image and visualize the resultant internal cloud of damage and fracture, initiated by dynamic loading in each specimen. It was shown that solid projectiles led to greater localized deformation and, in some cases, penetration, whereas fragmenting projectiles destroyed on impact resulted in more distributed loading leading to major front-surface damage depending on the depth on indentation before fragmentation

Chatter suppression in boring with tool position feedback control

Regenerative self-excited vibrations (chatter) often occur in boring operation due to low stiffness of a slender cantilever holder of a tool. These vibrations lead to significant defects of a machined surface and cutting tool damages. The new chatter suppression method is proposed in the paper. Displacement signal measured in the direction which is orthogonal to machined surface is used for generating a control action in the feed direction. Linear proportional control law is applied. Mathematical model of boring process dynamics with control has been developed for validation of the proposed method efficiency and searching better values of feedback gain

Impact damage in woven carbon fibre/epoxy laminates: Analysis of damage and dynamic strain fields

© 2017 The Authors. Published by Elsevier Ltd. In this study the resultant ballistic dynamic response observed in a 2x2 twill weave T300 carbon fibre/epoxy composite flat-plate specimen is examined, using a combination of non-invasive analysis techniques. The study investigates deformation and damage caused by impacts of two types of projectiles: solid (steel) travelling with velocity of 70-90 m/s, and fragmenting (ice) with the velocity in the range of 300-500 m/s. Digital image correlation was employed to obtain displacement and to estimate dynamic strain fields from the rear surfaces of the specimens during each experiment. 3D X-ray computer tomography (CT) was used to image and visualize the resultant damage inside the samples. It was shown that solid projectiles lead to greater localized deformation and in some cases penetration, whereas fragmenting projects destroyed on impact cause a more distributed impact load but can lead to major front-surface damage depending on the depth of indentation before fragmentation

WW Scattering Parameters via Pseudoscalar Phase Shifts

Using domain-wall lattice simulations, we study pseudoscalar-pseudoscalar scattering in the maximal isospin channel for an SU(3) gauge theory with two and six fermion flavors in the fundamental representation. This calculation of the S-wave scattering length is related to the next-to-leading order corrections to WW scattering through the low-energy coefficients of the chiral Lagrangian. While two and six flavor scattering lengths are similar for a fixed ratio of the pseudoscalar mass to its decay constant, six-flavor scattering shows a somewhat less repulsive next-to-leading order interaction than its two-flavor counterpart. Estimates are made for the WW scattering parameters and the plausibility of detection is discussed.Comment: 8 pages, 6 figure

Processing parameters influence on dynamics of vibratory drilling with adaptive control

Chip segmentation is one of necessary conditions of ensuring the deep hole drilling quality when processing hard-to-machine metals. It may be achieved through making drill bit harmonic oscillations in axial direction. Possible way to maintain such vibrations is to replace the standard drilling head with special vibratory head which includes elastic element giving the instrument a possibility to move in axial direction. Self-excitation of drill regenerative oscillations is possible if elastic element stiffness and processing parameters are chosen properly. It is advisable to complement this way of excitation by control action which is determined in feedback circuit and sustains required vibration process characteristics in wide range of processing parameters. In present paper the adaptive control algorithm of vibratory drilling process dynamics is proposed. Control action on oscillation system is proportional to drill vibrational velocity, the feedback gain is determined in adaptation circuit basing on comparison of actual peakto- peak vibrational displacement and its target value. Simulation of closedloop nonlinear system «elastic system – machining process – control system» dynamics has been performed for different values of processing parameters for cases with or without control. The simulation revealed efficiency of suggested algorithm in wide range of processing parameters. Joined influence of processing parameters and target peak-to-peak displacement values on chip breakage conditions is studied. Recommendations for choice of processing parameters and control parameters values are developed. Influence of control action magnitude limit on control system possibilities to achieve control target is analyzed

Influence of technological system’s rigidity on the dynamics of grinding process of flexible parts

The object of the present study is to investigate the dynamic of plane grinding by the tool with random distribution of abrasive grains, owning random geometric characteristics. The model is based on the consideration of machining system’s dynamical deformable characteristics, which have influence on the workpiece’s displacement under grinding process. The excitation of vibrations has significant effects on precision and surface quality, which is especially important in machining spatial parts, such as turbine blades

Influence of technological system’s rigidity on the dynamics of grinding process of flexible parts

The object of the present study is to investigate the dynamic of plane grinding by the tool with random distribution of abrasive grains, owning random geometric characteristics. The model is based on the consideration of machining system’s dynamical deformable characteristics, which have influence on the workpiece’s displacement under grinding process. The excitation of vibrations has significant effects on precision and surface quality, which is especially important in machining spatial parts, such as turbine blades

The Russian Science Citation Index (RSCI): the first three years (2016–2018)

Objective: To observe changes in the number, form (print and online), and distribution (by academic disciplines) of Russian journals indexed in the first three years of the Russian Science Citation Index (RSCI).Background: The globalization of science and the need to involve Russia in the international process of knowledge exchange have influenced the main directions of publication activity and interaction with the world scientific community. Methods: Statistical information freely available through the databases of the Scientific Electronic Library of Russia for January 2019 were compared with data from January 2016. Results: In 2016, the number of Russian journals included in the RSCI was 650; by 2019, the number had increased to 771, an increase of 18.6%. The number of journals with printed and online versions increased by 13.3% to reach 266 units. The number of Russian journals indexed in Scopus and the Web of Science databases increased during the period, as did the number of journals with both print and online versions.Conclusions: Journals from the RSCI database tend also to be added to Scopus or WoS databases and do not remain exclusively as part of the local database. Implementing the RSCI project had a positive impact on the full spectrum of Russian academic journals, which are increasingly committed to improving their work to continue to be part of RSCI or Scopus or WoS databases

Spectral and Cathodoluminescence Decay Characteristics of the Ba_1−xCe_xF_2+x (x = 0.3–0.4) Solid Solution Synthesized by Precipitation from Aqueous Solutions and Fusion

Single-phase samples of the Ba1−xCexF2+x solid solution (x = 0.3–0.4) were synthesized by directional crystallization in the form of single crystals and by co-precipitation from aqueous nitrate solutions using potassium fluoride as a fluorinating agent in the form of nanopowders. The cathodoluminescence of the pressed powder samples was studied in comparison with the BaF2: Ce single crystals in 250–460 nm (2.7–5 eV) spectral range upon excitation by an electron accelerator. The cathodoluminescence spectra of the samples revealed a wide band in the range of 3.0–4.0 eV, which consists of two typical components of Ce3+ with decay time 23 ns in the case of single crystals and three decay times 27 ns, 140–170 ns, and ~600 ns in the case of pressed powders. The decay time of the short-wavelength component (27 ns) in the case of pressed powders is close to the lifetime of the excited state of the Ce3+ ion. The developed X-ray phosphors can be applied for embedding in diamonds for diamond–nanoparticle composite preparation