MECH 210 – Materials Science and Engineering Problem Set 02, Fall Semester 2008 Due Wednesday (9/17) 1. Below are tabulated some Rockwell G hardness values measured on a single steel specimen. Compute (a) average and (b) standard deviation hardness values. (c) Calculate the range of hardness values for a 99.00% confidence level. 46.3 47.7 46.1 51.1 49.0 49.4 44.6 45.2 44.9 48.9 47.3 45.4 46.6 50.1 47.5 49.4 45.7 48.7 2. A hot rolled 1020 steel bar having a diameter of 15 mm is to be used to support a tensile load of 24,740 N in service. Calculate the safety factor for this design. 3. (a) Estimate the theoretical fracture strength of a brittle material if it is known that fracture occurs by the propagation of an elliptically shaped surface crack of length 0.5 mm and having a tip radius of 0.005 mm, when a stress of 1035 MPa is applied. (b) Estimate the theoretical stress concentration factor for the crack geometry. 4.
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