Functions of Chordotonal Sensilla in Bushcrickets (Orthoptera, Tettigoniidae)

Acoustic and vibrational sensitivity of single identified auditory receptors in bushcrickets was studied by electrophysiological methods. In the intermediate organ, some neurons were identified whose response to acceleration did not depend on the stimulus frequency over a significant frequency range; along with them, there were cells showing increased sensitivity to frequencies of 0.4–0.8 kHz for displacement, and/or 0.1–0.3, 1–1.2, and 1.4–3 kHz for all the vibration parameters. In addition, most of the studied receptors had a zone of increased sensitivity to highfrequency vibrations at 1.5–2.5 kHz. In the sensilla of the crista acustica, increased sensitivity was recorded at frequencies of 0.1–0.3, 0.4–0.8, 1–1.2, and 1.4–2.5 kHz. The best frequencies of a single sensillum may lie in different frequency ranges for different vibration parameters. Such differences in sensitivity to vibration acceleration, vibration velocity, and displacement, and also the different best frequencies in the receptors of the intermediate organ and the crista acustica were probably determined by differences in size, position, and morphological details of the sensilla, their own resonances, and reactions to resonance vibrations of the trachea section bearing the vibroreceptors. Thus, the chordotonal sensillum is a bifunctional mechanoreceptor which, along with auditory sensitivity, can combine the functions of both a displacement receiver and an accelerometer due to the different mechanical properties of its cells and the surrounding structures.

Mitigating Twist-Offs While Drilling with the Help of BHA Dynamics Software

One of the major challenges the Oil and Gas Industry faces nowadays during drilling operations is the twist-offs on Bottom Hole Assembly (BHA) components such as Drilling Jars, Shock Tools, Mud Motors, Roller Reamers, Stabilizers, Drill Collars, PBLs, Heavy Weight Drill Pipe (HWDP), Drill Pipe (DP), etc. To overcome this challenge, an initiative was proposed by performing a study based on twist-offs experienced on BHA components while drilling operations and recommendations are provided to reduce and eliminate twist-offs related to drilling with suboptimal drilling parameters. The statistical data for the twist-off events was collected coming from Daily Drilling Reports, and the analysis was limited to all wells which presented twist-offs on the drillstring and BHA components. Three examples of twist-offs due to drilling with erratic torque are discussed as well as a successful example of drilling parameters optimization. The three examples which presented drillstring and BHA twist-offs were analyzed using available BHA Dynamics and vibrations software and it was discovered that the parameters utilized (operational RPM) fell within the critical zone shearing force peaks (resonance vibrations). The components with the most twist-offs were identified. The hole size where we have the most twist-offs were also identified, which will help in focusing on these areas for the recommendations provided. This analysis will help Drilling Engineers and Foremen to foresee vibration dysfunctions and act accordingly by the use of available BHA Dynamics software in order to optimize drilling parameters before and during drilling. By drilling within a safe operating RPM window (away from resonant RPM), there will be reduction in the number of twist-offs and associated lost time.

Nonlinear excitation of hypersound vibrations in ferrite plate in conditions of combine influence in two frequencies. Part 1. Resonance on difference frequency

The task about nonlinear excitation of hypersound vibrations in ferrite plate in conditions of combine influence in two frequencies is investigated. As a preliminary task the investigation of only magnetic vibrations by two-frequency excitation is carried out. The possibility of description of forced linear vibrations on the basis of single nonuniform linear second order equation with arbitrary excitation is shown. It is found the analytical solution of task about excitation of oscillator by two signals which frequencies are distinguishes up and down from central frequency on the same frequency interval. It is shown the equivalency of representation of magnetic vibrations in linear regime and model vibrations on the basis of oscillator. It is found that in the general case the vibrations have view as beating which rounding frequency is equal to difference between excitation frequencies. The whole positing of task about excitation of nonlinear magnetoelastic vibrations in normal magnetized ferrite plate by two-frequency excitation is proposed. It is found that in conditions of large nonlinearity when the own elastic resonance of plate is equal to the difference frequency the powerful elastic vibrations are excited. It is found the nonlinear excitation of powerful non-resonance vibrations which take place also in the case of large elastic dissipation. It is shown that the non-resonance vibrations are determined precisely two-frequency character of excitation. It is found that the amplitude of non-resonance vibrations by increasing of plate thickness also is increased. By the small level of excitation, the low of increasing is linear, by middle – quadratic, by large – again approaches to linear with saturation and non-permanent sudden jumps. The character of excitation in conditions of resonance on difference frequency is investigated. It is shown that this resonance has powerful determined nonlinear character because it arises only by enough large excitation level. It is shown that the further increasing of resonance amplitude by the increasing the excitation level is realized by the low which is near to quadratic. But after this increasing when excitation level reaches determined value the resonance amplitude is saturated and remains constant. It is drawn attention to some discrepancy between the realization on nonlinearity by magnetic and elastic systems. For the de-scription of this discrepancy the empirical quadratic dependence is proposed. In brief is proposed some remarks about further development of work.

Assessment of the Impact of Shot-Peening on the Fatigue Life of a Compressor Blade Subjected to Resonance Vibrations

This publication presents an assessment of the influence of a surface treatment such as shot-peening on the fatigue life of a compressor blade exposed to resonant vibrations. As part of the work, a geometric model of the blade was developed, and a numerical modal and fatigue analysis were performed. The fatigue analysis was based on the Manson–Coffin–Basquin and Ramberg–Osgood models. Additionally, the location of the highest equivalent stresses was established. Based on the results of the strength analysis, two points were identified where a fatigue crack may potentially occur. As part of the work, the influence of different values of residual stresses on the results of the fatigue life was determined. The obtained results were compared to the literature values of fatigue life for this blade. A secondary objective of the study was to determine the size of the grains at various points of the blade, as well as the thickness of the layer plasticized as a result of peening. The relationship between the location of the highest values of the equivalent stresses and the thickness of the plasticized layer was determined. An explanation of the effect of shot-peening on the increase in the fatigue life of the blade was proposed.

Assessment of the Impact of Shot Peening on the Fatigue Life of a Compressor Blade Subjected to Resonance Vibrations

The publication presents the assessment of the influence of surface treatment such as shot-peening on the fatigue life of a compressor blade exposed to resonant vibrations. As part of the work, a geometric model of the blade was developed and a numerical modal and fatigue analysis were performed. The fatigue analysis was based on the Manson-Coffin-Basquin and Ramberg-Osgood models. As part of the work, the influence of different values of residual stresses on the results of fatigue life was determined. Additionally, the location of the highest equivalent stresses was established. The obtained results of the numerical analyzes were compared with the results presented in the scientific literature. An additional aim of the study was to determine the size of the grains at various points of the blade as well as the thickness of the layer plasticized as a result of peening. The obtained results are presented in the form of tables and charts. The relationship between the location of the highest values of equivalent stresses and the thickness of the plasticized layer was determined. The explanation of the effect of shot peening on the increase in fatigue life of the blade was proposed.

Research of resonance vibrations of the system «Telescopic screw — bulk medium» caused by torsional vibrations

The article outlines the relevance of using the principle of telescopy in the process of creation screw conveyors, which nowadays are folded to obtain significant lengths, which makes their designs expensive and structurally unreasonably complicated. It has been shown an experimental equipment, which provides measurement results of the research process in a wide range with high accuracy in an automated control mode with the necessary data capture. Based on the constructed mathematical model, the dependences of the angular perturbation velocity on the physicomechanical and geometric parameters of the «telescopic screw — bulk medium» system have been obtained. Because of analytical relations describing the laws of variation of characteristic parameters for its oscillation resonance case have been received. It has been proved that for resonant oscillations, when there are significant angular velocities of rotation, the natural frequency of the bending oscillations is smaller and at the same time the amplitude of the transition through the resonance is smaller. The results of the amplitude of the transverse oscillations of the system for different values of the angular velocity of rotation in time during the transition through the internal resonance, which largely depends on the physicomechanical and geometric characteristics of the motion of the medium, have been presented.