The effects of structural modifications on acoustic characteristics of enclosed bodies

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Tezin Türü: Yüksek Lisans

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Mühendislik Fakültesi, Makina Mühendisliği Bölümü, Türkiye

Tezin Onay Tarihi: 2010

Öğrenci: ÖZLEM DEMİRKAN

Danışman: HASAN NEVZAT ÖZGÜVEN

Özet:

Low frequency noise caused by vibrating panels can pose problems for vehicles from noise, vibration and harshness (NVH) standpoint. In order to reduce interior noise levels in cars, some structural modifications are required on the car body. Structural modifications studied in this work are stiffeners welded on the walls of enclosed structure to change vibration characteristics. In this thesis, interaction between acoustic domain inside closed structures and their vibrating enclosing boundaries are analyzed. Analysis of vibro-acoustic behavior includes frequency response analysis of structure by Finite Element Method (FEM) and sound pressure level (SPL) prediction of the cabin interior by Boundary Element Method (BEM). The standard parts of the analyses are performed using available CAE (Computer Aided Engineering) software. It is demonstrated that the structural modification technique integrated with the vibro-acoustic model of the system reduces the computational effort considerably. The frequency response functions of a structure for each modification can easily be obtained in a fast and efficient way by using the structural modification technique. Thus, effects of design changes in the structure body on noise levels due to vibration of the structure can be very handily and efficiently studied. In the case studies presented, the effects of various different stiffeners applied on a simple closed structure are studied in detail.