Iranian Society of Acoustics and Vibration and AvecinaJournal of Theoretical and Applied Vibration and Acoustics2423-476111220250830Influence of non-local parameter on period doubling behavior of CNTs conveying nanoparticles10912272392410.22064/tava.2025.2049773.1259ENRezaEbrahimiAssistant Professor, Mechanical Engineering, Faculty of Engineering, Yasouj University, Yasouj 75918-74831, Iran0000-0002-0118-437XMohammadSajjadnejadAssistant Professor, Materials Engineering, Faculty of Engineering, Yasouj University, Yasouj 75918-74831, IranJournal Article20250103In drug delivery systems, carbon nanotubes (CNTs) can be used as molecular channels to transport nanoparticles. In these applications, CNTs are subjected to a moving load, which leads to nonlinear vibrations of the CNTs. Therefore, the main goal of this study is to analyze the bifurcation behavior of CNTs under the effect of moving harmonic load. For this purpose, modeling of the system has been done using the non-local Euler-Bernoulli beam theory and Winkler spring. The Galerkin approach and Runge-Kutta method have been used to discretize and solve the equation of motion, respectively. The effects of the moving load, elastic bed stiffness and non-local elasticity parameter on the nonlinear dynamic response of the system have been investigated by using the bifurcation diagrams, phase plane, power spectrum and Poincare sections. The results indicate various non-linear behaviors such as the jump phenomenon, the periodic, subharmonic and quasi-periodic movements in the system response.https://tava.isav.ir/article_723924_a0f0d8795d67e9f44602a54bd5006ad9.pdfIranian Society of Acoustics and Vibration and AvecinaJournal of Theoretical and Applied Vibration and Acoustics2423-476111220250902Analytical synthesis of pulse-like strong near-fault ground motions through a parametric closed-form approach12314172308510.22064/tava.2025.2028274.1239ENAliNadim MovallooM.Sc. Student, Faculty of Engineering, Kharazmi University, Tehran, IRAN.AfshinMeshkat-DiniAssistant Professor, Faculty of Engineering, Kharazmi University, Tehran, IRAN.Journal Article20240509Near faults, recorded ground motions exhibit unique physical characteristics, different from those observed in far-field regions. These disparities are particularly evident in the configuration of accelerograms and their corresponding velocity- and displacement-based time-histories. The pulse structures observed in velocity time-histories characterized by an abrupt surge in the rate of energy release, especially in intensive ground motions with strong forward directivity effects, demand scrutiny. Many researchers have sought to develop closed-form formulas to accurately capture and explain these coherent pulses, as well as represent the medium- to high-amplitude frequency domains of strong ground motions. These closed-form formulas have been prepared to provide mathematical expressions that can effectively model the unique features of strong near-fault ground motions. Existing approaches typically rely on parametric formulations validated primarily through root-mean-square error minimization between modeled and recorded velocity time-histories. However, this paper presents a comprehensive analytical framework that implements systematic modeling and validation steps focused on capturing the essential physical characteristics of pulse-like near-fault ground motions critical for engineering applications. Adopting a set of closed-form formulas, this study replicates the key features of six strong near-fault earthquake records, with the methodology encompassing multiple validation criteria, including energy variation and displacement time-history profiles. The analytical models successfully captured at least 95% of the cumulative kinetic energy released during each record. These models demonstrate promising results in both rate of change and peak accuracy of displacement time-histories and effectively represent the main energetic frequency content throughout the analyzed time windows.https://tava.isav.ir/article_723085_3c8cb5c912fe9575222e0c1cb37d19f4.pdfIranian Society of Acoustics and Vibration and AvecinaJournal of Theoretical and Applied Vibration and Acoustics2423-476111220250701Studying free vibration of tympanic membrane using analytical, finite element and Rayleigh-ritz approaches14216072876310.22064/tava.2025.2049943.1260ENM. Mohammad-RezaOmmatmohammadiDepartment of Mechanical Engineering, University of Tabriz, Tabriz, Iran0009-0004-5154-7732HadiMajdiDepartment of Mechanical Engineering, University of Tabriz, Tabriz, IranJafarKeighobadiDepartment of Mechanical Engineering, University of Tabriz, Tabriz, IranJournal Article20250210<span style="font-size: 11.0pt; font-family: 'Times New Roman',serif; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA;">The tympanic membrane ™ plays a central role in the human hearing mechanism. Located at the entrance to the middle ear, it vibrates in response to changes in air pressure generated by incoming sound waves. The oscillation characteristics—particularly the natural frequencies and associated mode shapes—directly influence auditory perception and hearing sensitivity. This study investigates the TM’s natural frequencies using a simplified yet representative mathematical model, employing both analytical and semi‑analytical approaches. The semi‑analytical analysis is conducted using the Rayleigh–Ritz method with various basis functions to assess their accuracy in predicting frequency and mode shapes. Among these, Chebyshev polynomials exhibit exceptional efficiency, yielding high‑accuracy frequency estimates in close agreement with analytical solutions and validated by finite‑element simulations. In addition, the study examines the sensitivity of TM modes to variations in geometric and material parameters, providing valuable insight into their influence on dynamic behavior. A comparative analysis confirms that Chebyshev polynomials deliver the most accurate results, outperforming the other basis functions considered.</span>https://tava.isav.ir/article_728763_f2157cac10f21f8db053e07cf7aff0ce.pdfIranian Society of Acoustics and Vibration and AvecinaJournal of Theoretical and Applied Vibration and Acoustics2423-476111220250701Renovation of modified Biot's theory for modeling of the nanocomposite porous materials: A theoretical and experimental acoustical study16118372876210.22064/tava.2025.2053152.1261ENMohamadMirmasoumiAcoustics Research Lab., Department of Mechanical Engineering, Amirkabir University of Technology, Tehran, Iran.AbolfazlHasani BaferaniDepartment of Mechanical Engineering, Tafresh University, Tafresh, Iran.AbdolrezaOhadiAcoustics Research Lab., Department of Mechanical Engineering, Amirkabir University of Technology, Tehran, Iran.0000-0001-6514-4089Journal Article20250211<span style="font-size: 12.0pt; font-family: 'Times New Roman',serif; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA;">In this paper, the modified Biot’s theory is revised to predict the acoustic performance of nanocomposite porous materials more accurately, based on the nonlocal elasticity theory. The governing equations are derived for a transversely isotropic porous medium. The transfer matrix method is developed for the first time to obtain the absorption coefficient by introducing two non-local parameters, solid and fluid, to consider non-local effects. Subsequently, several nanocomposite foams are produced by various multiwall carbon nanotubes to validate the theoretical results. Different mechanical, acoustical, and non-acoustical properties of produced samples have been experimentally measured or calculated. Sound absorption for various solid and fluid nonlocal parameters is presented and compared with the corresponding absorption coefficient experimentally obtained from the impedance tube test. The obtained results show that by ignoring the fluid nonlocal effect, the experimental results agree well with the theoretical predictions based on modified Biot’s theory in wave propagation for large values of the solid nonlocal parameters.</span>https://tava.isav.ir/article_728762_dde914801ac24ad301838417ae092e45.pdfIranian Society of Acoustics and Vibration and AvecinaJournal of Theoretical and Applied Vibration and Acoustics2423-476111220250701The effect of shaft-coupling penetration ratio on torsional vibration analysis18420373281410.22064/tava.2025.2065737.1269ENMostafaIrannejadpariziAssistant Professor, College of Engineering, University of Tehran, Tehran, Iran.Rotor-dynamics Researcher, Oil Turbo-Compressor Equipment (OTCE), Tehran, Iran.0000-0002-1446-9219PouyaAsgharifard SharabianiRotor-dynamics Researcher, Oil Turbo-Compressor Equipment (OTCE), Tehran, Iran.HamedNavabiRotor-dynamics Researcher, Oil Turbo-Compressor Equipment (OTCE), Tehran, Iran.AkbarNaderpourRotor-dynamics Researcher, Oil Turbo-Compressor Equipment (OTCE), Tehran, Iran.SaeedHekmatgolmakaniRotor-dynamics Researcher, Oil Turbo-Compressor Equipment (OTCE), Tehran, Iran.Journal Article20250713<span>When designing typical rotating equipment, torsional natural frequencies (TNFs) must be studied to identify possible resonances. Accurate computation of TNFs and torsional modes requires precise modeling of the shaft-coupling connection. The shaft penetration factor (SPF), representing the shaft's penetration into the coupling hub, significantly affects torsional stiffness calculations. This paper develops a comprehensive torsional vibration software (TVS) for the analysis of a centrifugal compressor train. The torsional analysis of an electrocompressor train, based on API 617 criteria, examines the SPF's effect on torsional output. Five modeling approaches for shaft penetration are considered: SPF values of 0, ⅓, ½, 1, and an end-to-end shaft-coupling connection. These approaches' effects on the torsional behavior of a real centrifugal compressor train designed by OTCE are investigated. Results show that different modeling approaches change the 2nd and 4th flexible TNFs by about 21% and 13%, respectively, plus noticeable differences in mode shapes. The Campbell diagram reveals that intersections of the 2X excitation line with the 2nd and 4th TNFs fall near or within the API separation margin, shifting closer or farther from the critical speed range depending on the modeling approach. Therefore, precise modeling of flexible coupling stiffness is crucial for correctly addressing compressor train torsional natural frequencies, as minor uncertainties in the shaft-coupling connection may cause significant differences in torsional behavior.</span>https://tava.isav.ir/article_732814_b0b83f32af01743f66e0a6fe49981973.pdfIranian Society of Acoustics and Vibration and AvecinaJournal of Theoretical and Applied Vibration and Acoustics2423-476111220250701An investigation into the behaviour of resonances of polymeric and metallic cylinders in acoustic wave scattering20423173281510.22064/tava.2025.2070564.1272ENVajihehsadatSajadiNDE Lab., Faculty of Mechanical Engineering, K.N. Toosi University of Technology, Tehran, IRAN.FarhangHonarvarNDE Lab., Faculty of Mechanical Engineering, K.N. Toosi University of Technology, Tehran, IRAN.0000-0002-4774-3237MohammadrezaKariMedical Physics, University of Wisconsin-Madison, Madison, Wisconsin 53705, USAJournal Article20250904Accurate characterization of thin cylinders - such as polymer filaments and metal wires - is important for enhancing the performance of new additive manufacturing (AM) processes which are developing with very high speed. This study investigates the circumferential resonance frequencies of metallic and polymeric cylinders subjected to normally incident plane acoustic waves, enabling the identification of their key elastic properties. Using a combination of analytical techniques and experimental methods, the acoustic wave scattering of both material types is thoroughly examined. The analysis uncovers a clear distinction: in aluminum cylinders, resonance frequencies emerge as minima in the form function, while in polymer filaments, they present as maxima. This contrasting behavior is validated through theoretical models and experimental measurements. Furthermore, the study examines interference at normal incidence, showing that the constructive interference responsible for resonances in the polymer filament appears as maxima (peaks) in the form function, whereas the destructive interference in the metallic cylinder manifests as minima (dips). This clear analytical and experimental demonstration of contrasting resonance behavior provides deeper insight into the acoustic properties of metallic and polymeric materials, thereby supporting improved material selection and quality control in AM applications.https://tava.isav.ir/article_732815_154dd2c6430574f3d9f2339f6698d3d1.pdf