•Typical brittle materials like glassdo not show any plastic deformationbut fail while the deformation is elastic. •One of the characteristics of a brittle failure is that the two broken parts can be reassembled to produce the same shape as the original component as there will not be a neck formation like in the case of ductile materials. •A typical stress strain curve for a brittle material will be linear.••Stress–strain curve for brittle materials.

Elastic material- Stress –strain diagram•Figure 8-7 shows a stress-strain diagram for a highly elastic material. •It could be rubber or anything else that is very elastic.

Strength of Joints

Bearing Failure•Is a type of compressive failure from a fastener pushing, or bearing against the sheet.•Will show up as an elongated hole.•Failures depends on bearing strength, the thickness of material, and the size of fastener.•Placing a fastener to close to the edge of a sheet will result in tear-out failure.

Example: computing failures•Two sheets of material to be joined by a single fastener.•Fastener is 0.25 in diameter with a Fs of 32,000 psi.•Material is 0.050 thick and 1 inch wide.•Material has Ft of55,000lb & Fb of 85,000 lbs•Center of fastener hole is 0.75 inn from the edge•Four problems to work: tensile failure, shear failure, bearing failure and tear-out failure.

Physical PropertiesPhysical properties of interest are:1. Density- is its weight per unit volume. >Lbs /cubic inch.> combined with strength of materials produces strength/weight ratio.Example: given two materials ,A with a tensile yield of 120,000 psi and a density of 0.28 lb/in3 and with a tensile strength of 60,000 psi and B with a tensile yield strength of 60,000 lb/in3 and density of 0.10 lb/in3.Provide a rod of 8 inches long of each material capable of supporting a load of 10,000 lb? How big a cross section?Remember the formula: f=P/A, then A is = P/fA = 0.083 in2 and B = 0.167 in2

2. Specific Gravity•A materials specific gravity used to compare the weights of materials.•The specific gravity of a substance is its weight divided by the weight of and equal volume of water.•Since volumes are in play then it is a ratio of densities.•Example: water weighs approximately 8 lbs to the gallon; an oil with a specific gravity of 0.9 would weigh 7.2 lbs to the gallon.

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3.Thermal Expansion•Conductivity of a material refers to either electrical or heat.•Thermal conductivity- is the property of a material to conduct heat.>This is desirable for materials needed to conduct excess heat away.> Insulating materials should have low thermal conductivity•Electrical conductivity- is a measure