Properties of Materials Chapter 5

1. Properties of MaterialsChapter 5 Manufacturing Enterprises

2. Selecting Materials • Selection is based on an understanding of various properties. • Selecting materials cannot be taken lightly. • Lives of customers and the reputation of the company is at stake.

3. Properties of Materials • 7 types • Physical • Mechanical • Chemical • Thermal • Electrical/Magnetic • Optical • Acoustical

4. Physical Properties • Structure: • Includes atomic and molecular structure (microstructure) • Includes visible structure (macrostructure) • Moisture Content: • Measure of trapped water within a material’s structure • Defined as the weight of water a s a percentage of the moisture-free weight of the material

5. Physical Properties cont. • Size/Shape: • Density: • Measure of the mass of a material. • Allows you to compare weights of various materials. • Specific gravity: • Porosity: • Ability of a material to absorb air and water • Surface texture: • The way a surface of a material looks and feels.

7. Mechanical Properties • Govern how a material will react to a force or load. • Determined by 3 factors: • Type of bonding • Structural arrangement of atoms/molecules • # and types of imperfections • 4 major mechanical properties: • Strength • Elasticity • Plasticity • Hardness

9. Mechanical Properties cont. • Strength: • Tensile: the maximum tension load a material can withstand before fracturing. Most widely used. • Compression: ability to resist forces which tend to squeeze the material into a new shape. • Basically opposite of tensile. • Excessive compression force will cause the material to rupture. • Shear: ability to resist fracture under shear forces. • Caused by offset forces applied in opposite directions. • Torsion: ability to resist twisting.

11. Mechanical Properties cont. Elasticity: ability of a material to undergo compression or stretching without permanent deformation. Plasticity: ability of a material to flow into a new shape under pressure. Ductility: ability of a material to undergo plastic deformation without rupturing. Have high malleability, workability, or formability Brittleness: measure of the lack or resistance to force. Brittle material will fracture when forces are applied.

12. Mechanical Properties cont. • Hardness: the resistance of a material to penetration or scratching. Resistance to denting

14. Stress vs Strain • Stress – the force applied to the material. • Strain – the change length of a material under stress. • Yield point: • Fracture Point:

15. Chemical Properties • Reaction between chemicals in the environment and the materials. • Corrosion types • Oxidation (iron oxide or rust) • Electrochemical corrosion • Water Absorption

16. Thermal Properties • All operate in the presence of heat. • Reactions of materials to varying levels of heat • 5 types of thermal Properties • Thermal Resistance: ability to resist melting • Thermal Conductivity: ability to conduct heat through the material • Thermal Expansion: degree the material expands in the presence of heat • Thermal Emission: ability to give off or radiate heat. • Thermal Shock Resistance: ability to resist shock produced by rapid changes in temp.

18. Electrical/Magnetic Properties • Ability to conduct electrical current: • Conductors: • Low electrical resistance • Semiconductors: • Between insulators and conductors • Insulators/resistors: • High resistance to electrical current • Magnetic: material’s reaction to magnetic field. • Magnetic permeability • Magnetic conductivity

20. Acoustical Properties • Materials reaction to sound waves • 2 major groups: • Acoustical transmission: • How well sound travels through materials. • Acoustical reflectivity: • Amount of sound that will bounce off a material.

22. Optical Properties • A material’s reaction to light • Color – reflection of light • Light refection: amount of light that a material reflects. • Transmission: Amount of light a material lets pass through it. • Opacity – how much the material blocks light • Transparent: allows most of the light to pass through it. • Translucent: allow some light to pass through.