Homework_1 - Introduction To Materials Science Chapter 1...

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Unformatted text preview: Introduction To Materials Science, Chapter 1, Introduction Composites Thin crystalline platelets grown fromCr,lut-on ,- Mo ihs voldhis crystal structure so !i Fe cha na f e t back and forth: chain-folded model Spring 2005 Engineering Material Polyethylene Polymer composite materials: reinforcing glass fibers in a polymer matrix. University of Virginia, Dept. of Materials Science and Engineering Homework #1 18 The average chain length is much greater than the thickness of the crystallite University of Virginia, Dept. of Materials Science and Engiineeriing of Virgi24ia, Dept. of Materials Science and Engineering U n v e r s ty n 9 Reading Assignments Chapters 1, 2 Chapter 3 sections 1-14 Chapter 12 sections 1-4 Chater 14 sections 1-4 Design 1. Explain why it is difficult to find a material with both a high stiffness and a high coefficient of thermal expansion 2. Describe some of the key mechanical and physical properties to consider in designing a material for an airplane wing. Primary Bonds 3. Electrical charge is transferred in metals by movement of valence electrons. How many potential charges carriers are there in an aluminum wire 1mm in diameter and 100 mm in length 4. What is the most likely type of primary bond in each of these materials (explain) Spring 2005 Engineering Material a. b. c. d. Cu KCl Si CdTe Your task is to 5. The bond energy curves for two engineering materials are shown below. select the better material for use in each application described below Energy x A B 1. A beam that shows low deflection under moderate load 2. A crucible to be used at a high service temperature 3. A device designed to sense changes in temperatures by changing dimensions Secondary Bonds 6. Predict which member of each pair of materials has a higher melting temperature 1. C2F4 or C2H2F2 2. CH4 or NH3 (predict the higher vaporization temperature) 3. C14H30 or C5H12 Crystal Structure 7. Tantalum has the bcc structure. Its lattice parameter is a = 0.33026 nm at room temperature. a. Sketch the unit cell, and show the lattice parameter. b. Determine the atomic radius, R, and the atomic diameter, d, in nm. c. Determine the atomic volume, Ω, in nm3 . d. Determine the density, ρ, in Mg/m3 e. Sketch another bcc unit cell and draw solid lines between the body-centered atom and its nearest neighbors. What is the nearest-neighbor coordination number? Spring 2005 Engineering Material Miller Indices 8. Fill in the direction indices and the Miller indices. Directions Planes HF IA EB BG HB CG HI EF OE OB ODF ABFG AIG BCFE BDF ACG BIO ACFD DEFG ACH 9.What are the indices of the four directions of the form <110> that lie in the (11 1) plane of a cubic cell? ...
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