# HW6Solutions - MSE280B Introduction to Materials...

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MSE280B: Introduction to Materials Engineering Homework 6: Solutions 1. (5 Points) Elastic deformation is where bonds between atoms stretch reversibly whereas plastic deformation involves bond breaking between neighboring atoms and new bonds forming. 2. (5 Points) Elastic modulus remains constant upon cold working. Slope during unloading and reloading is parallel to original elastic portion of the curve. 3. Problem 7.9 from Callister (10 points) This problem asks that we compute the original length of a cylindrical specimen that is stressed in compression. It is first convenient to compute the lateral strain x as ε x = d d 0 = 30.04 mm 30.00 mm 30.00 mm = 1.33 × 10 -3 In order to determine the longitudinal strain z we need Poisson's ratio, which may be computed using Equation 7.9; solving for yields ν = E 2 G 1 = 65.5 × 10 3 MPa (2) ( 25.4 × 10 3 MPa ) 1 = 0.289 Now z may be computed from Equation 7.8 as ε z = ε x ν = 1.33 × 10 3 0.289 = 4.60 × 10 -3 Now solving for l 0 using Equation 7.2 l 0 = l i 1 + ε z = 105.20 mm 1 4.60 × 10 3 = 105.69 mm

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