Materials ScienceLecture 1
What is Materials Science ?
Why do we study it ?
Example 1:Protective tiles on the space shuttle.
What conditions / environments might those tiles see?
What is the major concern in the design of those tiles?
Example 2: A concrete bridgeWhat is the role of the bridge? Fern Bridge, Californiahttp://sunnyfortuna.com/explore/sights.htm
I-35 bridge failureMultiple deficiencies at inspectionswww.greentechforum.net
Materials History: Prehistoric The earliest materials?
Two cave people
Materials History: Ancient HistoryExtraction of Metals
Processing Natural materials
Materials Science and EngieeringWe study materials to learn why they behave the way they do so that we may use that knowledge to make good engineering decisions in choosing the right materials for the job and so that we may, if necessary, seek out methods of creating materials that will serve our needs best.
Transmittance: --Aluminum oxide may be transparent, translucent, or opaque depending on the material structure. Adapted from Fig. 1.2,Callister 7e.(Specimen preparation,P.A. Lessing; photo by S. Tanner.)OPTICAL
Example 3: Follow the Bouncing Ball
ex: hardness vs structure of steel Properties depend on structure Data obtained from Figs. 10.30(a)and 10.32 with 4 wt% C composition,and from Fig. 11.14 and associateddiscussion, Callister 7e.Micrographs adapted from (a) Fig.10.19; (b) Fig. 9.30;(c) Fig. 10.33;and (d) Fig. 10.21, Callister 7e. ex: structure vs cooling rate of steel Processing can change structure Structure, Processing, & PropertiesHardness (BHN)Cooling Rate (C/s)1002003004005006000.010.11101001000
Example 4: Polarized Lightwww.exploratorium.edu
Four Components to the Discipline of MSE
Classifactions of Materials Metals -
Biomaterials - We will be primarily concerned with Metals, Polymers, and composites
Use the right material for the job. Understand the relation between properties, structure, and processing. Recognize new design opportunities offered by materials selection.Course Goals:SUMMARYUnderstand that new materials can be tailored to specific design requirements.
The study of why materials behave the way they do.As engineers we will be concerned with designing products and also with designing what those products are made of.1. Room Temp take-off2.Gradual cooling off while rising in elevation.3. Sustained cold while in space.4.Rapid heating to extreme temperatures during re-entry.5. Cool down after landing.
Major Concerns: Excessive temperature cycling.What happens when cycling temperatures? Expansion/Contraction, thermal stresses.Other Concerns: They found a solution.Cost, strength, means of fabrication etc. Cost $10,000/tile; tiles about 6in squareWhat is the role of the bridge? To support specified loads (cars) for a predetermined determined, long range, timeframe.Major Concerns: Will it fail? Will it last as long as we want? Safety. Will we be able to tell in advance when it is failing?Cost more of a factor b/c there are many, many bridges.Many bridges are made of concrete - cheap, strong, durable (environments)Safe? How does it fail?Relatively quick catastrophic failure.Not enough advance warning.Re-enforce with metals bars, rebars. metals bend before breaking, adds strength, and more time to notice failure.Earliest materials used by cave people? Natural materials, Wood, stone, clay, animal skins. Why choosen: found lying around. Next, biggest advance: Production of metals. Extract them from natural materials.Mixing and treating natural materials: firing pottery, alloys, heat treating metalsAll of the above are based on selection/treatment of what is existing.Materials drive our societyStone AgeBronze AgeIron AgeNext, biggest advance: Production of metals. Extract them from natural materials.Mixing and treating natural materials: firing pottery, alloys, heat treating metalsAll of the above are based on selection/treatment of what is existing.Recent focus: materials science and engineeringUse knowledge of science to understand why materials behave the way they do.Then use that information to engineer better materials.Two polarizing lenses. Crossed to block out light.Clear polymer bar in between. Still dark.Bend bar, light pases through. Why?Driven by molecular structure of polymer.Processing - ex: heat treating, fireing clayStructure - arrangement of internal components on several length scales: Subatomic, atomic, microscopic, macroscopicProperties - mechanical, electrical, thermal, magnetic, optical, and deteriorativePerformance - how well it does the job