302_Mechanics SolutionInstructors_Sol.Manual-Mechanics_Materials_7e.book_Gere_light.1

302_Mechanics SolutionInstructors_Sol.Manual-Mechanics_Materials_7e.book_Gere_light.1

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296 CHAPTER 3 Torsion Problem 3.7-5 A hollow circular shaft for use in a pumping station is being designed with an inside diameter equal to 0.75 times the outside diameter. The shaft must transmit 400 hp at 400 rpm without exceeding the allowable shear stress of 6000 psi. Determine the minimum required outside diameter d . Problem 3.7-4 The drive shaft for a truck (outer diameter 60 mm and inner diameter 40 mm) is running at 2500 rpm (see figure). (a) If the shaft transmits 150 kW, what is the maximum shear stress in the shaft? (b) If the allowable shear stress is 30 MPa, what is the maximum power that can be transmitted? 60 mm 2500 rpm 60 mm 40 mm Solution 3.7-4 Drive shaft for a truck d 2 ± 60 mm d 1 ± 40 mm n ± 2500 rpm (a) M AXIMUM SHEAR STRESS
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Unformatted text preview: max P power (watts) P 150 kW 150,000 W T torque (newton meters) n rpm T 60(150,000 W) 2 p (2500 rpm) 572.96 N # m P 2 p nT 60 T 60 P 2 p n I P p 32 ( d 2 4 d 1 4 ) 1.0210 * 10 6 m 4 (b) M AXIMUM POWER P max allow 30 MPa ; 267 kW P max P t allow t max (150 kW) a 30 MPa 16.835 MPa b ; t max 16.8 MPa 16.835 MPa t max Td 2 2 I P (572.96 N # m)(0.060 m) 2(1.0210 * 10 6 m 4 ) (b) R OTATIONAL SPEED IS DOUBLED If n is doubled but H remains the same, then T is halved. If T is halved, so is the maximum shear stress. Shear stress is halved ; H 2 p nT 33,000 Sec_3.5-3.7.qxd 9/27/08 1:10 PM Page 296...
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