8-Mechanical Behavior

89 x 103 pa 1 nm2 1 pa engineering strain strain lf

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Unformatted text preview: Pa ENGINEERING STRAIN Strain = lf - lo lo = Δl (change in length) lo ( original length ) Units SI meters per meter (m/m) US inches per inch (in/in) % engineering strain = Strain x 100 = % elongation Figure 5.21 Tensile Testing Machine Schematic Drawing of Tensile Test Frame Strain Extensometer TENSILE TEST Used to evaluate the strength of materials. MECHANICAL PROPERTIES ( Important for structural design ) 1. Modulus of elasticity (Young's modulus) 2. Yield strength 3. Ultimate tensile strength 4. Percent elongation 5. Percent reduction in area at fracture MODULUS OF ELASTICITY Stress and strain in the elastic region of the engineering stress-strain diagram is described by Hooke's Law. σ (stress) = E x ε (strain) E (elastic modulus) = stress σ = strain ε where E is the modulus of elasticity (Young's modulus) Elastic Modulus of Materials Materials Elastic Moduli GPa psi Steels 30 x 106 207 Aluminum 10 x 106 69 Glass 10 x 106 69 Wood 1x 106 7 Polyester 4 x 105 3 YIELD STRENGTH Stress at which significant plastic deformation begins. No definite point on stress-strain curve where ela...
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This document was uploaded on 02/27/2014 for the course NANO 108 at UCSD.

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