|MadSci Network: Engineering|
All these terms are discussed in a Materials Science text book and are fairly well covered in the following Wikipedia links. Read up. Elastic Modulus http://en.wikipedia.org/wiki/Elastic_modulus Hardness http://en.wikipedia.org/wiki/Hardness Tensile strength http://en.wikipedia.org/wiki/Tensile_strength http://www.absoluteastronomy.com/topics/Tensile_strength Elastic modulus is the slope of the linear stress-strain curve with no deformation of the material. Tensile is the force per unit area necessary to deform or break the material. Hardness is a measurement of the distance a specific indentor penetrates into a material with a known force. Hardness and tensile strength are linearly related so hardness can be used as a fast measurement of tensile on the same materials. Since the measurements are all force on unit areas the units are usually Pascals [newtons/sq.m] or PSI[lbs/sq. in] altho hardness values are usually expressed in a scale from the specific machine used to test.
Try the links in the MadSci Library for more information on Engineering.