# Typical brittle materials like glass do not show any

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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 diagramFigure 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 FailureIs 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 failuresTwo 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 lbsCenter of fastener hole is 0.75 inn from the edgeFour 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 GravityA 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 ExpansionConductivity 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 conductivityElectrical conductivity- is a measure