MSE 230 HW3 (due 01/28, 01/29) Spring 2010 1. A long steel tape measure 9.5 mm wide x 0.20 mm thick having an elastic modulus E = 210 GPa is used to measure the width of a concrete airport runway, which is perfectly flat and exactly 100.000 m wide. In making the measurement, the tape is pulled tight and straight with 40.0 N (~10 lb) force. (a) If the scale marks or graduations were printed on the tape under zero load and at the same temperature as the measurement is made (20°C), what value will it read (measure) for the actual length of 100.000 m? (b) Under the same load, at what temperature would the tape measure read exactly 100.000 m if the thermal expansion coefficient of the steel tape is 12.0 x 10-6/°C? 2. (a) Calculate the specific stiffness for bending of square bars (beams) of 1020 Steel, Ti-6Al-4V, Al-2024, and Mg-AZ31B. (b) For beams of these alloys of a given length and resistance to elastic deflection, calculate the mass relative to that of the steel beam and comment on the results. (c) Using the cost
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