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1
Content available remote Free vibration studies on skew sandwich plates
Kumar Dhotre Pavan, Venkateshappa Chikko Srinivasa
Composites Theory and Practice
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2020
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R. 20, nr 3-4
118--127
EN
The present work focuses on determining the fundamental frequencies of skew sandwich plates with face sheets considered to be classical thin plates, which are made of a graphite-epoxy material and an orthotropic core made of glass reinforced- epoxy using different boundary conditions. The fundamental frequencies were obtained using finite elements, which are validated with available literature results. The effects of the skew angle, ratio of the length to total thickness of the sandwich plate, and ratio of the thickness of the core to the face sheet on the fundamental frequency of skew sandwich plates were obtained. In addition, the effect of parameters such as the number of layers in the face sheet, the laminate stacking sequence and the fiber orientation angle on the fundamental frequencies of laminated skew sandwich plates was also ascertained. It was found that the CQUAD8 element yields better results than the CQUAD4 element in the present study. The fundamental frequencies were found to increase with an increasing skew angle. The variation in the fundamental frequency is negligible when there are a large number of layers in the face sheet.
2
Content available Numerical analysis for frequency and displacement improvement of a long span floor building
Supriyadi Bambang
Archives of Civil Engineering
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2020
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Vol. 66, nr 4
651--660
EN
In the last decade many buildings such as multipurpose buildings, malls, auditoriums, sports halls which have long-span building floor structure. Various research results indicate that in general long-span concrete floor structures have a fundamental frequency of less than 7 Hz. This will risk a resonance if this floor receives dynamic loads of people jogging to follow the song with a frequency of 2-3 Hz. This research was conducted to numerically analyze the long-span building floor model using SAP2000, to determine the fundamental frequency and maximum displacement of the floor structure model. It was also investigated how to increase its fundamental frequency and reduce the maximum displacement. The results have shown that the numerical analysis of the plate model long-span floor building using SAP2000 produces a fundamental frequency of 5.19 Hz. Model III with Reinforcing double equal angles (84x37x10x2.5) steel truss provides the best results, increases the fundamental frequency to be 7.93 Hz, and with a variety of static and dynamic loads, decreases the value of the displacement and far from the allowable displacement.
3
Content available Transient analysis of transversely functionally graded Timoshenko beam (TFGTB) in conjunction with finite element method
Khafaji Salwan Obaid Waheed, Al-Shujairi Mohammed A., Aubad Mohammed Jawad
Archive of Mechanical Engineering
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2020
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LXVII, nr 3
299--321
EN
In this work, transient and free vibration analyses are illustrated for a functionally graded Timoshenko beam (FGM) using finite element method. The governing equilibrium equations and boundary conditions (B-Cs) are derived according to the principle of Hamilton. The materials constituents of the FG beam that vary smoothly along the thickness of the beam (along beam thickness) are evaluated using the rule of mixture method. Power law index, slenderness ratio, modulus of elasticity ratio, and boundary conditions effect of the cantilever and simply supported beams on the dynamic response of the beam are studied. Moreover, the influence of mass distribution and continuous stiffness of the FGM beam are deeply investigated. Comparisons between the current free vibration results (fundamental frequency) and other available studies are performed to check the formulation of the current mathematical model. Good results have been obtained. A significant effect is noticed in the transient response of both simply supported and cantilever beams at the smaller values of the power index and the modulus elasticity ratio.
4
Content available remote Wyznaczanie wartości chwilowej częstotliwości podstawowej tonu krtaniowego za pomocą analizy falkowej sygnału mowy
Wilk B.
Przegląd Elektrotechniczny
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2015
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R. 91, nr 11
305-308
PL
Jednym z ważniejszych parametrów charakteryzujących źródło mowy dźwięcznej jest częstotliwość podstawowa tonu krtaniowego (F0), która odpowiada częstotliwości podstawowej drgań fałd głosowych. W artykule zaprezentowano metodę wyznaczania wartości chwilowych tej częstotliwości za pomocą analizy falkowej sygnału mowy. Metodę zastosowano do badania wyizolowanych głosek w celu oceny zmienności częstotliwości podstawowej tonu krtaniowego.
EN
One of the basic parameters characterizing voiced speech is the fundamental vocal frequency (pitch, F0), which corresponds to the rate of the vocal folds vibration. In this paper, a method based on wavelet analysis of speech signal for determining instantaneous fundamental frequency is presented. This method was applied to some isolated voiced vowels for assessment of pitch frequency variability.
5
Content available Finite element studies on free vibration of laminated composite cylindrical skew panels
Srinivasa C. V., Suresh Y. J., Prema Kumar W. P.
International Journal of Applied Mechanics and Engineering
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2014
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Vol. 19, no. 1
165--180
EN
This paper presents the finite element studies on free vibration of isotropic and laminated composite cylindrical skew panels. The analysis is performed using CQUAD4 and CQUAD8 elements of MSC/NASTRAN. The effects of the panel angle, skew angle, aspect ratio and length-to-thickness-ratio on fundamental frequency of isotropic cylindrical skew panels are studied. The effects of additional parameters such as the fiber orientation angle, numbers of layers and stacking sequence on the fundamental frequency of antisymmetric composite laminates are also studied. It is found that the CQUAD8 element yields better results than the CQUAD4 element in the validation and convergence studies. The CQUAD8 element is employed for the remaining part of the studies. The fundamental frequencies are found to increase with the panel angle and skew angle. When the number of layers in the laminate is large, the variation of the fundamental frequency with the number of layers is not appreciable. The boundary conditions are found to have a significant influence on the fundamental frequency.
6
Content available remote Computation of ground motion amplification in Kolkata megacity (India) using finite-difference method for seismic microzonation
Shiuly A, Kumar V, Narayan J.P.
Acta Geophysica
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2014
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Vol. 62, no. 3
425--450
EN
This paper presents the ground motion amplification scenario along with fundamental frequency (F0) of sedimentary deposit for the seismic microzonation of Kolkata City, situated on the world’s largest delta island with very soft soil deposit. A 4th order accurate SH-wave viscoelastic finite-difference algorithm is used for computation of response of 1D model for each borehole location. Different maps, such as for F0, amplification at F0, average spectral amplification (ASA) in the different frequency bandwidth of earthquake engineering interest are developed for a variety of end-users communities. The obtained ASA of the order of 3-6 at most of the borehole locations in a frequency range of 0.2510.0 Hz reveals that Kolkata City may suffer severe damage even during a moderate earthquake. Further, unexpected severe damage to collapse of multi-storey buildings may occur in localities near Hoogly River and Salt Lake area due to double resonance effects during distant large earthquakes.
7
Content available Diagnostic significance of phase spectrum in acoustic analysis of pathological voice
Samborska-Owczarek A.
Pomiary Automatyka Kontrola
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2010
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R. 56, nr 12
1547-1550
EN
The paper regards the possibility of using new numerical features extracted from the phase spectrum of a speech signal for voice quality estimation in acoustic analysis for medical purposes. This novel approach does not require detection or estimation of the fundamental frequency and works on all types of speech signal: euphonic, dysphonic and aphonic as well. The experiment results presented in the paper are very promising: the developed F0-independant voice features are strongly correlated with two voice quality indicators: grade of hoarseness G (r>0.8) and roughness R (r>0.75) from GIRBAS scale, and exceed the standard voice parameters: jitter and shimmer.
PL
Artykuł dotyczy możliwości ekstrakcji cech numerycznych z widma fazowego sygnału mowy w celu wykorzystania w analizie akustycznej na potrzeby medyczne. Podejście to umożliwia uzależnienie analizy akustycznej od zawodnych metod wykrywania/wyznaczania częstotliwości podstawowej (tonu krtaniowego) i dzięki temu przeznaczone jest do badania wszystkich typów sygnału mowy (również afonicznych). Wyniki eksperymentu są bardzo obiecujące - proponowane cechy Ph1 i Ph2 są silnie skorelowane z dwoma kategoriami percepcyjnymi: stopniem chrypki (r>0.8) oraz szorstkością głosu (r>0.75) ze skali GIRBAS, wykazując silniejsze znaczenie diagnostyczne niż znane i stosowane od dawna wskaźniki jitter i shimmer. Proponowane podejście oprócz skuteczności charakteryzuje się szeregiem dodatkowych korzyści: algorytm metody z powodu niskiej złożoności jest szybki i niekosztowny, interpretacja matematyczna jest prosta i jednoznaczna oraz spójna z obserwowanym obrazem widma fazowego głosu. Ponadto uniezależnienie od detekcji częstotliwości podstawowej sprawia, że algorytm jest deterministyczny oraz efektywny dla każdego typu sygnału mowy.
8
Content available remote Hydrodynamic resonation through-flow system as acoustic circuit
Kusnerova M., Valicek J., Hloch S., Sadilek M., Cep R.
Archiwum Technologii Maszyn i Automatyzacji
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2008
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Vol. 28, nr 4
43-52
EN
The paper proposes a derivation of general characteristic acoustic parameters of the hydrodynamic resonation system elements. The acoustic parameters of the system are the acoustic compliance and acoustic mass as primary parameters for calculation of the theoretical resonation fundamental frequency for turbulent water-flow. Frequency model (5 kHz to 25 kHz) refers to the interpolation for the liquid pressure range from 5 MPa to 25 MPa. The analysis travels in a direction of a value comparison of concrete acoustic characteristic parameters for any element of the system and has been contrasted with theoretical conditions about an acoustic mass for tubes and an acoustic compliance for chambers. This system generates a modulate liquid jet as a result of resonation chamber implantation. The theoretical model was built on the basis of knowledge of primarily geometric dimensions of the system and the pressures of the liquid to predict values of fundamental frequencies of oscillations. Predicted oscillation frequencies were verified by laboratory measurements.
PL
W artykule zaproponowano ogólną charakterystykę parametrów akustycznych hydrodynamicznego systemu rezonansowego. Podstawowymi parametrami akustycznymi systemu, wykorzystywanymi do obliczeń podstawowej częstotliwości teoretycznego rezonansu przepływu turbu-lentnego wody, są odkształcalność akustyczna i masa akustyczna. Model częstotliwościowy (od 5 kHz do 25 kHz) dotyczy interpolacji dla ciśnienia płynu od 5 MPa do 25 MPa. Analiza zmierza w kierunku porównania wartości konkretnych parametrów charakterystyk akustycznych każdego elementu systemu i została zestawiona z warunkami teoretycznymi dotyczącymi masy akustycznej rur i akustycznej odkształcalności komór. System ten tworzy modulowany strumień płynu jako wynik zastosowania rezonansu komory. Model teoretyczny był zbudowany na podstawie wiedzy o pierwotnych wymiarach geometrycznych systemu i ciśnień płynu po to, aby przewidzieć wartości podstawowych częstotliwości drgań. Przewidywane częstotliwości drgań były sprawdzane przez pomiary laboratoryjne.
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