WS2 - (b) To find the ultimate tensile strength, find the...

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MANE-4030: Elements of Mechanical Design: Worksheet #2 8/30/07: Ductile material behavior In a tension test of a steel specimen having a 7-mm radius circular cross section and using a gage length of 20 cm, the data shown below was recorded. Using this data, you are to (a) find the nominal (0.2% offset, engineering) yield stress, (b) find the nominal (engineering) ultimate tensile strength, (c) find the modulus of elasticity, and (d) compute the true stress at the maximum load. (a) To find the nominal yield stress, first, figure out what the deflection is associated with a 0.2% offset strain. Then, you need to draw a line parallel to the elastic loading line starting from this deflection, and find what the load is at this offset (where offset line intersects load line). Using this load and the known dimensions, compute the nominal yield stress.
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Unformatted text preview: (b) To find the ultimate tensile strength, find the maximum load and compute the corresponding stress. This stress is referred to as the ultimate tensile strength because it is associated with the maximum load that a unixially loaded specimen can carry in tension. (c) To find the elastic modulus, simply find the slope of the load deflection curve in the beginning linear region, and then normalize to convert this to stress/strain. (d) Using the change in length and the approximation that the volume is about the same, estimate the average cross-sectional area in the gage region. Use this area to compute the true stress at the maximum load. 10 20 30 40 50 60 70 5 10 15 20 25 30 load (kN) elongation (mm) 10 20 30 40 50 60 70 0.5 1 1.5 2 elongation (mm) Detail of small elongation region....
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