01-02ChapGere.0008 - strength of the cast iron in...

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SECTION 1.7 Allowable Loads 39 Problem 1.7-4 An aluminum tube serving as a compression brace in the fuselage of a small airplane has the cross section shown in the figure. The outer diameter of the tube is d 5 25 mm and the wall thickness is t 5 2.5 mm. The yield stress for the aluminum is s Y 5 270 MPa and the ultimate stress is s U 5 310 MPa. Calculate the allowable compressive force P allow if the factors of safety with respect to the yield stress and the ultimate stress are 4 and 5, respectively. d t Solution 1.7-4 Aluminum tube in compression d 5 25 mm t 5 2.5 mm d 0 5 inner diameter 5 20 mm A tube 5 p 4 ( d 2 2 d 0 2 ) 5 176.7 mm 2 Y IELD STRESS ± Y 5 270 MPa F.S. 5 4 The ultimate stress governs. A LLOWABLE COMPRESSIVE FORCE P allow 5 s allow A tube 5 (62 MPa)(176.7mm 2 ) 5 11.0kN 5 67.5 MPa s allow 5 270 MPa 4 d t U LTIMATE STRESS ± U 5 310 MPa F.S. 5 5 5 62 MPa s allow 5 310 MPa 5 Problem 1.7-5 A steel pad supporting heavy machinery rests on four short, hollow, cast iron piers (see figure). The ultimate
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Unformatted text preview: strength of the cast iron in compression is 50 ksi. The outer diameter of the piers is d 5 4.5 in. and the wall thickness is t 5 0.40 in. Using a factor of safety of 3.5 with respect to the ultimate strength, determine the total load P that may be supported by the pad. t d Solution 1.7-5 Cast iron piers in compression Four piers U 5 50 ksi n 5 3.5 s allow 5 s U n 5 50 ksi 3.5 5 14.29 ksi d 5 d 2 2 t 5 3.7in. P 1 5 allowable load on one pier 5 s allow A 5 (14.29 ksi)(5.152 in. 2 ) 5 73.62 k Total load P 5 4 P 1 5 294k 5 5.152 in. 2 A 5 p 4 ( d 2 2 d o 2 ) 5 p 4 [(4.5 in.) 2 2 (3.7 in.) 2 ] d t d 5 4.5in. t 5 0.4in. A-PDF Split DEMO : Purchase from www.A-PDF.com to remove the watermark...
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This note was uploaded on 09/20/2009 for the course COE 3001 taught by Professor Armanios during the Spring '08 term at Georgia Institute of Technology.

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