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Unformatted text preview: MechEng 382 Winter 2009 Homework #10 Solutions 1. [ A&J-1 , Ex. 21.1] It is found that a force F will inject a given weight of a thermosetting polymer into an intricate mould in 30s at 177 ◦ C and in 81.5s at 157 ◦ C. If the viscosity of the polymer follows an Arrhenius law, with a rate of process proportional to e- Q/ ¯ RT , calculate how long the process will take at 227 ◦ C. Solution t = 3 . 5s 2. [ A&J-1 , Ex. 20.1] A cylindrical tube in a chemical plant is subjected to an excess internal pressure of 6MPa , which leads to a circumferential stress in the tube wall. The tube wall is required to withstand this stress at a temperature of 510 ◦ C for 9 years. A designer has specified tubes of 40mm bore and 2mm wall thickness made from a stainless alloy of iron with 15 percent by weight of chromium. The manufacturer’s specification for this alloy gives the following information 1 . Over the present ranges of stress and temperature the alloy can be considered to creep according to the equation ˙ = Aσ 5 exp- Q ¯ RT (1) where A and Q are constants, ¯ R is the universal gas constant, and T is the absolute tempera- ture. Given that failure is imminent at an effective creep strain of 0.01 for the present alloy,ture....
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This note was uploaded on 09/28/2010 for the course MECHENG 382 taught by Professor Thouless during the Winter '08 term at University of Michigan.
- Winter '08