p2-2019

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<p>Universidade Federal de Itajubá Instituto de Engenharia Mecânica EME504 - Vibrações Mecânicas I Prof. José Juliano de Lima Junior Nome: No.: Nota: Prova de EME504 Término: 9 h 30 min Data: 25/06/2019 Observações: - Esta prova contém 5 página(s) e 4 questões, totalizando 10 pontos; - Prova sem consulta; - Não é permitido o empréstimo de qualquer material e uso de calculadoras programáveis; - Escrever as equações literalmente e depois substituir os valores, com letra legível; - Comprovar as respostas através de cálculos; - Destacar os resultados finais e as respectivas unidades com caneta; - Desligar e guardar celular e - A interpretação faz parte da prova. Formulário = senwt = FT(t) = rpico = kY 30 - = 0,4536kg; 1 in = 0, 0254 m</p><p>Prova de EME504 Pag. 2 de 5 1. A 100 kg machine is supported on an isolator of stiffness 700 kN/m. The machine causes a vertical disturbance force of 350 N at a revolution of 3,000 rpm. The damping ratio of the isolator is 0.2. Calculate (5.6/453, Inman, 3rd, 2008): (a) (1 ponto) the amplitude of motion caused by the unbalanced force; (b) (1 ponto) the transmissibility ratio, and (c) (1 ponto) the magnitude of the force transmitted to ground through the isolator. i) Modelo Fater de Flt)= Fosenwt 1 1 XIt) k C Amplitude de movimento Dados -6 X= 38x10 m X=0,038 mm m= 100 kg resp a K=700 KN Transmissibilidade de 2 N Fo = n=3.000 rpm J = 0,2 TR 1366 = a iii) Frequencia de excitação = 314,16 rod it) Amplitude de forca transmitida = iN) a = FT = 47,8 N de frequencias = 314,16 r=3,76 83,67 Boa Prova! 25/06/2019</p><p>Prova de EME504 Pag. 3 de 5 2. (2 pontos) A simplified model of a washing machine is illustrated in Figure. A bundle of wet clothes forms a mass of 10 kg (mb) in the machine and causes a rotating unbalance. The rotating mass is 20 kg (including mb) and the diameter of the washer basket (2e) is 50 cm. Assume that the spin cycle rotates at 300 rpm. Let k be 1,000 N/m and = 0.01. Calculate the force transmitted to the sides of the washing machines (5.8/454, Inman, 3rd, 2008). Top view k/2 c/2 natural mb 20 m k/2 Razao de Frictionless support i) Modelo r=4,44 7,07 vi) devido as desbalanceamento 2 2 Fo = m I Fo = N rii) de Dados = mb = 10 kg TR = 0,054 transmitida cm n=300 rpm TR = in FT = 133,3 N in resp. J = 0,01 iii) Frequencia de excitacao 31,42 rad 30 S Boa Prova! 25/06/2019</p><p>Prova de EME504 Pag. 4 de 5 3. (3 pontos) Typically, in designing an isolation system, one cannot choose any continuous value of k and C but rather, works from a parts catalog wherein manufacturers list isolators available and their properties (and costs, details of which are ignored here). Table lists several made up examples of available parts. Using this table, design an isolator for a 500 kg compressor running in steady state at 1,500 rev/min (5.13/454, Inman, 3rd, 2008). Part No. R1 R2 R3 R4 R5 M1 M2 M3 M4 M5 k (kN/m) 250 500 1,000 1,800 2,500 75 150 250 500 750 C (Ns/m) 2,000 1,800 1,500 1,000 500 110 115 140 160 200 i) Dados Eswlha kec tabelados 500 kg pare ii) de valor de 5 FT do que Fo 1,0 Part. n= R3 k = KN e C = 1.500 m m Para r> dor. par r=3. Frequencia de r=3,51 Tin = 157,08 rad 30 30 un necessaria 157,08 un = = 157,08 44, 72 wn 3,0 2 k = = k N = 1.370,8 KN m Boa Prova! 25/06/2019</p><p>Prova de EME504 Pag. 5 de 5 4. (2 pontos) The instrument board of an aircraft is mounted on an isolation pad to protect the panel from vibration of the aircraft frame. The dominant vibration in the aircraft is measured to be at 2,000 rpm. Because of size limitation in the aircraft's cabin, the isolators are only allowed to deflect 1/8 in. Find the percent of motion transmitted to the instrument panel if it weights 50 lbf (5.21/456, Inman, 3rd, 2008). Assim i) Modelo 1x25,4x10 Instrument board v) de isolation = 209,44 r=3,77 pad an 55,58 Aircraft de base. frame ii) Dadas TR= n=2.000 rpm Para in = W = ebf Frequincia de TR = 0,076 Assim ITn S 30 30 7,6% Frequincia natural as instruments. A estatica SE determinada or pesa e rigidez do Mas k mg g Boa Prova! 25/06/2019</p>