Exam 2 Fall 08 Solved

Exam 2 Fall 08 Solved - MEEN 222 Section 503 Fall 2008 Exam...

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MEEN 222 Section 503 Fall 2008 Exam II November 18, 2008 Name: _Miladin Radovic – Answers ____________________________________ GENERAL INSTRUCTIONS: A. Exam time: 1 hour and 25 min B. Read carefully each question C. Numerical problems without clearly indicated procedure will be considered incomplete! D. Sign Aggie honor statement. (100 points + 10 extra points) Aggie Honor Code: “On my honor, as an Aggie, I have neither given or received unauthorized aid on this academic work” Signature: ____________________________________________________
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_________ out of 100 + 10 extra points Part A. Fill the blanks or circle correct answer A1 (2) (2) (2) (2) (2) (2) (2) (2) (2) (2) Please indicate whether the following statements are TRUE or FALSE. - Brittle fracture takes place without any appreciable deformation and by rapid crack propagation. TRUE / FALSE - If all other conditions are the same, critical stress required for crack propagation in brittle materials will be smaller for the material with larger modulus of elasticity. TRUE / FALSE - The relaxation modulus is time dependent elastic modulus that is typical for totally elastic solids. TRUE / FALSE - The melting point of the polymer increases while glass transition temperature decreases with increasing molecular weight of polymer. TRUE / FALSE - The strength of the composite materials that contains discontinues fibers depends on the length of the fibers. TRUE / FALSE - Electrical conductivity of extrinsic semiconductors increases continuously with temperature because concentration of both mobile electrons and holes also increases with temperature. TRUE / FALSE - In both good electronic conductors and semiconductors, electrical conductivity increases with amount of impurities. TRUE / FALSE - Heat is transported in solid materials by both lattice waves (phonons) and free electrons. TRUE / FALSE - In antiferromagnetic materials the spin moments of neighboring atoms or ions are aligned in opposite direction. TRUE / FALSE - For transparent materials, index of refraction is larger if dielectric constant of the materials is larger. TRUE / FALSE A2 (2) The melting temperature in a polymer is always higher /lower ( circle correct answer ) than the glass transition temperature.
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A3 (2) Deformation of the material that is exposed to the static mechanical stresses at elevated temperatures is called: (a) Fatigue (b) Creep (c) Corrosion (d) Slow crack growth
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This note was uploaded on 01/05/2010 for the course MEEN 222 taught by Professor Radovic during the Spring '08 term at Texas A&M.

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Exam 2 Fall 08 Solved - MEEN 222 Section 503 Fall 2008 Exam...

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