introduction to materials science and engineering · pdf file© 2011 cengage learning...
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Chapter 1:Chapter 1:
Introduction to Introduction to Materials Materials
Science and Science and EngineeringEngineering
Chapter 1: Introduction to Materials Science and Engineering
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Learning Objectives
1. What is materials science and engineering?
2. Classification of materials.
3. Functional classification of materials.
4. Classification of materials based on structure.
5. Environmental and other effects.
6. Materials design and selection.
Chapter 1: Introduction to Materials Science and Engineering
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Composition Chemical makeup of a material
Structure Description of the arrangement of atoms, as seen at different levels of detail
Materials science Underlines the relationships between the synthesis and processing, structure, and properties of materials
Materials engineering
Focuses on how to translate or transform materials into useful devices or structures
Microstructure Structure of the material at the microscopic scale
What is Materials Science and Engineering?
Chapter 1: Introduction to Materials Science and Engineering
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Figure 1.1 - Application of the Tetrahedron of Materials Science and Engineering to Sheet Steels for Automotive
Chassis
Chapter 1: Introduction to Materials Science and Engineering
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Figure 1.2 - Application of the Tetrahedron of Materials Science and Engineering to Semiconducting Polymers for
Microelectronics
Chapter 1: Introduction to Materials Science and Engineering
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Table 1.1 - Representative Examples, Applications, and Properties for Each Category of Materials
Chapter 1: Introduction to Materials Science and Engineering
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Polymers
Polymerization Process by which polymers are produced
Strength-to-weight ratio
Is high for polymers
Thermoplastic polymers
Contain long polymer chains that are not rigidly connected, have good ductility and formability
Thermosettingpolymers
Strong polymers but more brittle because the molecular chains are tightly linked
Plastics Contain additives that enhance the properties of polymers
Composites Formed from two or more materials, producing properties not found in any single material
Chapter 1: Introduction to Materials Science and Engineering
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Figure 1.3 - Representative strengths of various categories of materials
Chapter 1: Introduction to Materials Science and Engineering
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Figure 1.6 - Functional Classification of Materials
Chapter 1: Introduction to Materials Science and Engineering
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Classification of Materials Basedon Structure
Crystalline The material’s atoms are arranged in a periodic fashion
Amorphous The arrangement of the material’s atoms does not have a long-range order
Single crystals Crystalline materials in the form of one crystal
Polycrystalline Crystalline materials with many crystals or grains
Grain boundaries Regions between individual crystals in a
polycrystalline material
Chapter 1: Introduction to Materials Science and Engineering
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Figure 1.7 - Increasing Temperature NormallyReduces the Strength of a Material
Chapter 1: Introduction to Materials Science and Engineering
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Figure 1.8 - Skin Operating Temperatures for Aircraft Have Increased With the Development of Improved Materials
Chapter 1: Introduction to Materials Science and Engineering
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Environmental and Other Effects
Corrosion Metals and polymers react with oxygen or other gases,
particularly at elevated temperatures. Metals and ceramics — Disintegrate. Polymers and non-oxide ceramics — Oxidize. Materials are attacked by corrosive liquids which leads to
premature failure.
Chapter 1: Introduction to Materials Science and Engineering
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Environmental and Other Effects
Fatigue Components must be designed such that the load on the
material may not be enough to cause permanent deformation.
Fatigue failure: When the material is loaded and unloaded thousands of times small cracks may begin to develop and materials fail as these cracks grow.
Strain rate Metallic materials:
Can be stretched significantly if pulled slowly — Small rate of strain.
Can snap if pulled fast — High rate of strain.
Chapter 1: Introduction to Materials Science and Engineering
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Materials Design and Selection
The material must: Acquire the desired physical and mechanical properties. Be capable of being processed or manufactured into the
desired shape. Provide an economical solution to the design problem.
Material cost is calculated on a cost-per-kilogram basis. Density of the material or its weight per unit volume
should be considered.
Chapter 1: Introduction to Materials Science and Engineering
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Table 1.2 - Strength-to-Weight Ratios of Various Materials
Chapter 1: Introduction to Materials Science and Engineering
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Key Terms
Composition Composites Crystalline Density Fatigue failure Grains Grain boundaries Materials science and engineering Materials science
Chapter 1: Introduction to Materials Science and Engineering
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Key Terms
Mechanical properties Materials engineering Microstructure Materials science and engineering tetrahedron Polymerization Plastics Polycrystalline Physical properties Processing
Chapter 1: Introduction to Materials Science and Engineering
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Key Terms
Structure Synthesis Strength-to-weight ratio Semiconductors Smart material Single crystals Thermoplastic Thermosetting
Chapter 1: Introduction to Materials Science and Engineering