Browsing by Author "S., Naidu Balireddy"

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    Vibro-Acoustics of Beams Under Variable Axial Loads
    (National Institute Of Technology Karnataka, Surathkal., 2024) S., Naidu Balireddy; P., Jeyaraj
    Stiffeners and beam like structural elements used in aircraft structures are subjected to variable axial loads. These structural elements are subjected to steady state mechanical excitations as well. The nature of variable axial load influences static stability and hence dynamic characteristics of the structural elements are also effected. Furthermore, the vibration and acoustic responses caused by steady state excitation need to be analyzed to take care of dynamic stress and human comfort. Numerical simulation studies carried out on a beam to analyze its vibroacoustic response under the action of variable axial loads (VALs) is presented. Effects of six different types of VALs and three types of end conditions on buckling, free vibration and sound radiation characteristics of an isotropic beam is carried out initially. Static buckling and free vibration characteristics are analyzed using shear and normal deformable theorem and Ritz method. Forced vibration response is obtained using modal super-position method and the acoustic response parameters are obtained using Rayleigh integral. The nature of variation of VALs and end conditions are influencing buckling and free vibration characteristics remarkably. Results indicate that the acoustic response is highly sensitive to the nature of VAL and intensity of the VAL. In general, sound power at resonance decreases when the magnitude of VAL is increased. In continuation, static stability and dynamic characteristics of a bi-directional functionally graded beams subjected to VALs using the Ritz method and Reddy’s beam theory has been carried out. The material property is varied as a function of the gradation pattern along with the length and thickness directions. The influence of uniform, linear, and parabolically varying axial loads on buckling and free vibration frequencies is investigated. There is a remarkable variation observed in both the characteristics, by changing the material properties from isotropic to bi-direction functionally graded. Furthermore, the study reveals that higher stiffness is achieved by the material gradation index increment along the thickness direction compared to the lengthwise gradation index increment. Buckling and free vibration modes are also highly sensitive to the nature of variable axial loads and gradation index.Similarly, a detailed investigation is carried out on the effects of bi-directional gradation, length-to-height ratio, and end conditions on the sound radiation behaviour of bi-directional functional graded beams subjected to quadratically decreasing axial load. The study reveals that the highest value in the gradation indexes in both directions significantly influences the sound power levels. The directivity pattern reveals that bi-directional functionally graded beams exhibits higher sound pressure levels around the critical buckling load. It is also observed that both structural and end conditions are influential factors in sound power levels (dB) and sound pressure levels (dB). Finally, an investigation on the influence of bio-inspired laminate reinforced composite material on the static and dynamic responses of the beams, with a particular emphasis on the acoustic study is also done. The responses demonstrates the significance of variable axial loads, boundary stiffness, material composition, lay up pattern and aspect ratios highly influences the non-dimensional buckling loads of bio-inspired beams. The study further revealed that the vibration analysis are following the buckling trends, and the fundamental frequency is approaching minimum value at the critical buckling load. The study also includes the behaviour of the bio-inspired in comparison to vibrational responses at various modes and parameter variations. It is found that quasi isotropic-symmetric (QI) bio-inspired beam has poor buckling, vibration and acoustic behaviours, while uni-directional bio-inspired beams has better characteristics.