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In this paper, we are proposing a new formulation of dissipated energy of hard rubbers as a function of the deformation energy expressed by the Yeoh hyperelastic model. Torsion deformation is considered as a planar deformation of a simple shear on the surface of a cylinder. Thus the deformation energy is dependent only on the first invariant of strain. Based on the experiment, a “hyperelastic proportional damping” (HPD) is proposed for hard rubbers under finite strains. Such damping is analogical to the model of proportional damping in the linear theory of viscoelasticity, i.e. the dissipated energy is proportional to the deformation energymultiplied by the frequency of dynamic harmonic loading. To obtain the experimental data, samples of hard EPDM rubbers of different harnesses were dynamically tested on a torsional test rig for different frequencies and amplitudes. The Yeoh model is chosen since the deformation function is dependent only on the first strain invariant for the description of the simple shear of a surface cylinder. The Yeoh constants are evaluated by curve fitting of the analytical stress function to the experimental torsion stress-deformation curve. The constants are used to express the deformation energy of the Yeoh model for specific cases of tested rubbers. The coefficients of hyperelastic proportional damping are evaluated on the basis of experimental results.

The contribution describes PIV (Particle Image Velocimetry) measurement of airflow in the glottal region of complex physical models of the voice production that consist of 1 : 1 scaled models of the trachea, the self-oscillating vocal folds and the human vocal tract with acoustical spaces that correspond to the vowels /a:/, /u:/ and /i:/. The time-resolved PIV method was used for visualization of the airflow simultaneously with measurements of subglottal pressure, radiated acoustic pressure and vocal fold vibrations. The measurements were performed within a physiologically real range of mean airflow rate and fundamental phonation frequency. The images of the vibrating vocal folds during one oscillation period were recorded by the high-speed camera at the same time instants as the velocity fields measured by the PIV method.In the region above the models of the ventricular folds and of the epilaryngeal tube it is possible to detect large vortices with dimensions comparable with the channel cross-section and moving relatively slowly downstream. The vortices disappear in the narrower pharyngeal part of the vocal tract model where the flow is getting more uniform. The basic features of the coherent structures identified in the laryngeal cavity models in the interval of the measured airflow rates were found qualitatively similar for all three vowels investigated.

Application of dry friction damping contact is very often used for damping of turbine blades vibration. This problem is intensively studied in our Institute for several years, but the deficiency of knowledge of special material's friction characteristics introduces serious uncertainty into the results of research, particularly for the friction connection with periodic relative motion. Therefore, laboratory experimental equipment has been designed and realized. Results of the first set of measurement are presented and discussed. Friction of double steel blade material and overlay of tungsten carbide was investigated for various thrust forces and frequencies of relative motion at the simultaneous measurement of temperatures in three points near the friction surface. An increase of temperature after 25 s of friction run, friction coefficient, friction force, dissipated energy in one cycle during 1 s, entire energy during the friction run, lost power, and energy for 1℃ temperature increase in various conditions were ascertained. [ABSTRACT FROM AUTHOR]

The proposed method of parametric identification of thermo-mechanical constants of rubber was employed herein on the case of kinematically excited rubber beam. A linear 3D finite element thermo-mechanical model in program COMSOL was developed for low strain dynamic loading. Damping processes in rubber was described by special case of proportional damping. Thermo-mechanical coupling was realized by a conservative energy law. [ABSTRACT FROM AUTHOR]

The motivation of this paper is the continual development of the blades for the last stage of the steam turbine. The biggest problem is the slenderness of such blades and the extreme sensitivity to aeroelastic vibrations (flutter) caused by the instabilities present in the flow. This experimental research is dealing with the aeroelastic binding of the moving blades located in the blade grid with the flow field and vice versa. A parallelogram is used to ensure one order of freedom of the blade. The grid has five blades in total, three of them are driven by force control using three shakers. The deviation as well as force response is measured by strain gauges and dynamometers. The flow field statistical as well as dynamical characteristics are measured by optical method Particle Image Velocimetry. The grid is connected to the blow-down wind tunnel with velocity range up to 40 m/s. The aeroelastic binding is investigated in dependency on used actuation frequency and maximal amplitude (the intensity of force actuation) and on different Reynolds numbers. The flow field and the wake behind each individual blade are studied and the maximal interaction is examined for individual inter-blade phase angle of the grid.

Objectives: This study aimed to estimate vocal loading in loud phonation of a vowel and two widely used semiocclusion voice exercises (SOVTEs). Impact stress (IS) was estimated from glottal closing speed, inertial forces from the second derivative of glottal opening and closing., Study Design: Experimental study in vivo., Methods: A vocally healthy male sustained the [o:] vowel with habitual loudness and loudly: (1) without a tube, (2) into a silicone "Lax Vox" type tube (35 cm in length, 10 mm in diameter) outer end submerged 10 cm in water, and (3) into a straw (length 12.6 cm, diameter 2.5 mm) the outer end in air. He tried to use equal effort in all loud samples. High-speed video-laryngo-endoscopy was performed with a rigid scope. Oral air pressure (P oral ) was registered in a mouthpiece through which the endoscope was inserted into the larynx and to which the tubes were attached air-tightly., Results: Compared with vowel phonation at habitual loudness, mean of maximal glottal width (max GW) increased by 44.1% for loud tube phonation and decreased by 1.8% for loud straw phonation, and mean absolute value of minimum GW time derivative d min increased by 57.1% for tube and by 29.5% for straw suggesting faster glottal closing. Compared with loud vowel phonation, max GW increased by 22.6% for loud tube phonation, while it decreased by 16.6% for loud straw phonation. For the tube, d min decreased by 7.6% and for the straw by 23.8%. Maximal acceleration (ACC) and deceleration (DC) values were larger for the tube and smaller for the straw than the values for both vowel phonations., Conclusions: IS, deduced from d min , increased in loud SOVTEs compared to vowel phonation at a conversational loudness, but remained lower in loud SOVTEs than in loud vowel phonation, particularly with a narrow straw, which also reduced inertial forces, as suggested by the reduced ACC and DC., Competing Interests: Declaration of Competing Interest The authors have no interest to declare., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Purpose: Coughing is related to voice problems, since it involves firm glottal closure, fast glottal opening, and high subglottic pressure and flow rate. In this study, the glottal area variation and movements of laryngeal structures during coughing and phonation are compared., Methods: High-speed laryngoscopy recordings were made of a normophonic male participant with a healthy larynx producing a neutral vowel and coughing. Oral air pressure was registered in a mouthpiece, through which an endoscope was inserted into the pharynx. Electroglottography, acoustic, and pressure signals were recorded simultaneously. The glottal width variation at the membranous and cartilaginous parts of the glottis was derived from the high-speed images, and the strong vibration of the false vocal folds was also registered., Results: In coughing, compared to ordinary vowel phonation in nearly the same sound pressure level (93-94 dB 6cm ), the glottal width was 25% larger at the middle of the vocal folds, the maximum glottal opening velocity was 39% higher, and the maximum glottal width declination rate during glottal closing was up to three times higher. The maximum acceleration was 40% higher, and the maximum deceleration was 47% higher. Fundamental frequency f 0 was the highest (ca. 400 Hz) at the beginning of the first phase of a typical coughing process. During the last part of the coughing process, f 0 decreased from ca. 250 Hz to ca. 85 Hz at the phonation offset., Conclusions: The remarkable increase in maximum glottal width declination rate implies much higher vocal fold loading in coughing compared to phonation., (Copyright © 2023 The Voice Foundation. Published by Elsevier Inc. All rights reserved.)

Objectives: Water resistance voice therapy applies phonation into water through a tube. This study investigates how strenuous this therapy can be for the vocal folds in terms of impact stress (IS). It further examines whether it is possible to estimate the IS using the contact quotient (CQ) and maximum derivative from an electroglottogram (EGG)., Study Design: Experimental study., Methods: A male participant sustained a rounded back vowel [u:] or [o:] at a comfortable speaking pitch and loudness, and phonated into a silicone "Lax Vox" tube submerged 2 cm in water. High-speed videolaryngoscopy was performed with a rigid scope. Oral air pressure (P oral ) was registered in a mouthpiece through which an endoscope was inserted into the larynx. An EGG was recorded., Results: The CQ EGG from the EGG and the closed quotient from the glottal width (CQ area ) increased, while the maximum glottal amplitude and absolute value of derivative minimum (d min ) and also the derivative maximum from the EGG decreased for phonation into water. Normalized amplitude quotient from the glottal width variation also decreased but the change was not significant., Conclusions: Based on the glottal area findings, water resistance therapy does not seem to increase vocal fold loading (in terms of increased IS) even if the increase of CQ area , and CQ EGG suggest so. CQ EGG may qualitatively correspond to that of area, but the reliability of CQ (from the glottal area or the EGG) and the maximum derivative from the EGG as estimates of IS in semiocclusion exercises warrant further studies., (Copyright © 2018. Published by Elsevier Inc.)