1. PHYSICAL PROPERTIES OF MATERIALS Chapter 3

2. Density Melting point Specific heat Thermal conductivity Thermal expansion Electrical properties Magnetic properties Resistance to oxidation Resistance to corrosion PHYSICAL PROPERTIES

3. DENSITY- MASS PER UNIT VOLUME Also called specific gravity which expresses a material’s density with respect to water

4. TABLE 3.1 PHYSICAL PROPERTIES OF SELECTED MATERIALS AT ROOM TEMPERATURE

5. TABLE 3.2 PHYSICAL PROPERTIES OF MATERIALS, IN DESCENDING ORDER

6. Titanium and aluminum are among the most commonly used metal for aircraft and aerospace applications

7. FIGURE 3.1 RATIO OF MAXIMUM YIELD STRESS TO DENSITY FOR SELECTED METALS.

8. FIGURE 3.2 SPECIFIC STRENGTH (TENSILE STRENGTH/DENSITY) AND SPECIFIC STIFFNESS (ELASTIC MODULUS/ DENSITY) FOR VARIOUS MATERIALS AT ROOM TEMPERATURE. (SEE ALSO CHAPTER 9.)

9. COMPOSITE MATERIALS HAVE BECOME IMPORTANT FOR THEIR HIGH SPECIFIC STRENGTH AND STIFFNESS Density High speed equipment Textile machines Printing press Cameras High weight desirable- – Counterweights – Flywheels – Ballasts – Golf clubs Elevated temperatures- specific strength & stiffness Turbines Automotive Jet engines Gas turbines

10. FIGURE 3.3 SPECIFIC STRENGTH (TENSILE STRENGTH/DENSITY) FOR A VARIETY OF MATERIALS AS A FUNCTION OF TEMPERATURE. NOTE THE USEFUL TEMPERATURE RANGE FOR THESE MATERIALS AND THE HIGH VALUES FOR COMPOSITE MATERIALS. MMC—METAL-MATRIX COMPOSITE; FRP—FIBER- REINFORCED PLASTIC.

11. Plastics have lowest useful range Graphite and refractory metals have the highest useful range Annealing Heat treating Hot-working MELTING POINT- DEPENDS ON THE TEMPERATURE TO SEPARATE ITS ATOMS

12. Alloying has a minor effect on specific heat Temperature rise in a work piece is a function of the work done and of the specific heat of the work piece material SPECIFIC HEAT- THE ENERGY TO RAISE THE TEMPERATURE OF A UNIT MASS BY 1 DEGREE

13. The rate at which heat flows within and through a material Metallically bonded materials (metals) generally have a higher conductivity Ionically or covalently bonded materials (ceramics, plastics) have poor conductivity Cooling fins Cutting tools Die-cast molds to conduct heat THERMAL CONDUCTIVITY

14. Generally, the coefficient of thermal expansion is inversely proportional to the melting point of the material Shrink fits utilize thermal expansion and contraction-heat a part often installed on a shaft, install the part, let the part cool and contract Thermal stress Cracking Warping Loosening Thermal fatigue results from thermal cycling Thermal shock-cracks after just a single thermal cycle Low expansion alloys-iron-nickel alloys with low thermal-expansion coefficients THERMAL EXPANSION

15. ELECTRICAL CONDUCTIVITY

16. ELECTRICAL EQUIPMENT MACHINERY MANFACTURING PROCESSSES UNITS: MHO/M OR MHO/FT WHERE MHO IS THE REVERSE OF OHM, THE UNIT OF ELECTRICAL RESISTANCE ALLOYING OF METALS RAISES THE CONDUCTIVITY ELECTRICAL CONDUCTIVITY

17. INSULATORS OR DIELECTRICS: MATERIALS WITH HIGH ELECTRICAL RESISTIVITY ELECTRICAL RESISTIVITY IS THE INVERSE OF ELECTRICAL CONDUCTIVITY CONDUCTORS: MATERIALS WITH HIGH ELECTRICAL CONDUCTIVITY

18. SUPERCONDUCTIVITY IS THE PHENOMENON OF NEAR- ZERO ELECTRICAL RESISTIVITY THAT OCCURS IN SOME MATERIALS OR ALLOYS BELOW A CRITICAL TEMPERATURE (OFTEN ABSOLUTE ZERO) HIGH-POWER MAGNETS MRI-MAGNETIC RESONANCE IMAGING SUPERCONDUCTORS

19. CORROSION REFERS TO THE DETERIORATION OF METALS AND CERAMICS DEGRADATION REFERS TO THE DETERIORATION OF PLASTICS FOOD CHEMICAL PETROLIUM INDUSTRY MANUFACTURING OPERATIONS CORROSION RESISTANCE

20. CORROSION RESISTANT MATERIALS: NONFERROUS METALS STAINLESS STEEL NONMETALLIC MATERIALS STEEL & CAST IRON MUST BE PROTECTED BY COATINGS AND SURFACE TREATMENTS PITTING: LOCALIZED CORROSION OF A MATERIAL SALT…CORROSION?

21. TWO ELECTRODES IN AN ELECTROLYTE IN A CORROSIVE ENVIRONMENT THAT INCLUDES MOISTURE CAUSE GALVANIC CORROSION STRESS-CORROSION CRACKING OXIDATION-REMOVAL OF MATERIAL BY CHEMICAL REACTION GALVANIC CELL