Abdul Hamid, Muhammad Najib (2015) Analysis of Drum Brake Squeal. PhD thesis, Universiti Sains Malaysia.
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Abstract
Bentuk lenturan semasa operasi digunakan untuk menentukan mod bentuk getaran bagi kasut brek semasa kejadian bunyi kiut brek gelendong. Pengukuran bentuk lenturan semasa operasi bagi kasut brek adalah didapati dalam mod pulasan dan menyamai mod bentuk yang diperolehi melalui eksperimen modal bagi kasut brek dalam keadaan bersentuhan dengan gelendong brek. Model matematik bagi darjah kedua kebebasan dihasilkan dengan menggunakan maklumat daripada eksperimen modal dan juga frekuensi bunyi kiut iaitu 1850 Hz. Dalam kajian ini, bentuk lenturan semasa operasi digunakan dalam melaksanakan ubahsuai struktur dinamik kepada kasut brek bagi meningkatkan kestabilan sistem brek. Model parameter tergumpal bagi kasut brek ini digunakan untuk menilai kesan ubahsuai struktur dinamik dengan kaedah analisis fana. Model matematik tersebut menghasilkan keputusan yang hampir sama dengan eksperimen dan ini membolehkan para jurutera menilai parameter yang penting dalam menghasilkan brek gelendong yang bebas dari bunyi kiut. Seterusnya, bunyi kiut grek gelendong ini dianalisa pula menggunakan kaedah unsur terhingga. Kajian kedua meliputi kestabilan dinamik bagi brek gelendong yang terdiri daripada satu gelendong yang berputar dan dua kasut brek yang static yang mana kesan putaran diambil kira dalm analisis nilai eigen kompleks. Pengaruh kelajuan putaran gelendong diwakili oleh kesan Coriolis and daya empar. Hasil kajian menunjukkan satu mod tidak stabil pada 1658 Hz dan nilai ini hampir dengan frekuensi yang diukur. Apabila kelajuan ditingkatkan, bahagian positif pada nilai eigen kompleks menurun dan menjadi negatif apabila kelajuan melebihi 600 putaran seminit. ________________________________________________________________________________________________________________________ The operational deflection shapes were used to identify the mode of vibration for the brake shoes in drum brake squeal. The measurement of the operational deflection shapes of the brake shoes during drum brake squeal, which was in the torsional mode, was similar to that of the modes obtained from the experimental modal analysis of the brake shoe under the in-contact static condition. A two-degree-of-freedom model was developed on the basis of the experimental modal analysis data within the limited bandwidth of the squeal frequency of 1850 Hz. In this work, the operational deflection shape was used for determination of a structural dynamic modification to be carried out on the brake shoes in order to maximize the damping of the torsional mode as a way to improve the stability of the system. The lumped parameter model was then used to assess the effect of the structural dynamic modification on the squeal based on the transient analysis, which showed a similar trend and can assist brake designers in evaluating the critical parameter to obtain a squeal-free drum brake design. The drum brake squeal was further analysed using finite element method. The second part of this study was the dynamic instability of a drum brake system, which consists of a rotating drum and two immobile brake shoes which took into consideration the rotation effect on the complex eigenvalue. The Coriolis force and the centrifugal load represented the effect of the rotation of the drum. The results indicated an unstable mode at 1658 Hz, which is equivalent to the measured frequency of the drum brake squeal. As the speed was increased, the positive real part of the complex eigenvalue Re(λ) decreased and became negative at speeds beyond 600 rpm.
| Item Type: | Thesis (PhD) |
|---|---|
| Additional Information: | Full text is available at http://irplus.eng.usm.my:8080/ir_plus/institutionalPublicationPublicView.action?institutionalItemId=2114 |
| Subjects: | T Technology T Technology > TJ Mechanical engineering and machinery > TJ1-1570 Mechanical engineering and machinery |
| Divisions: | Kampus Kejuruteraan (Engineering Campus) > Pusat Pengajian Kejuruteraan Mekanikal (School of Mechanical Engineering) > Thesis |
| Depositing User: | Mr Mohd Jasnizam Mohd Salleh |
| Date Deposited: | 13 Jun 2018 02:18 |
| Last Modified: | 13 Jun 2018 02:18 |
| URI: | http://eprints.usm.my/id/eprint/40774 |
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