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CRC Press - Mechanical Engineering Handbook- Mechanics Of Solids Part 7

Tham khảo tài liệu 'crc press - mechanical engineering handbook- mechanics of solids part 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 1-60 Section 1 The magnification factor for the amplitude of the oscillations is MF A I 1 F k d 2Z ffl 2 1 - o ffl 2 2 1.4.11 This quantity is sketched as a function of the frequency ratio Q for several damping factors in Figure 1.4.3. Note that the amplitude of vibration is reduced at all values of Q if the coefficient of damping c is increased in a particular system. Q 0 FIGURE 1.4.3 Magnification factor in damped forced vibration. Vibration Control Vibration Isolation It is often desirable to reduce the forces transmitted or the noise and motions inside or in the neighborhood of vibrating machines and structures. This can be done to some extent within the constraints of space and additional weight and cost by the use of isolators such as rubber engine mounts and wheel suspension systems in cars. Many kinds of isolating materials and systems are available commercially. The effectiveness of vibration isolation is expressed by the transmissibility TR the ratio of the force transmitted FT to the disturbing force Fo. A simple isolation system is modeled as a spring and a dashpot in parallel for which the transmissibility is given by Equation 1.4.12 and sketched in Figure 1.4.4. TR F F o J1 4Z2 ỊA Ị2 J 1 ÍÍẠ 2 4Z2 ỊẠO 2 1.4.12 FIGURE 1.4.4 Transmissibility patterns of a vibration .