Chapter 6 hw edit

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Apr 3, 2024

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Madelaine Tew 4/3/2023 HW 5 6.3 A specimen of aluminum having a rectangular cross section 10 mm * 12.7 mm (0.4 in.0.5 in.) is pulled in tension with 35,500 N (8000 lbf) force, producing only elastic deformation. Calculate the resulting strain Stress = 35500 / (10*12.7) = 279.53 Strain = 279.53 / 70E3 = 3.99 * 10^-3 6.7 For a bronze alloy, the stress at which plastic deformation begins is 275 MPa (40,000 psi), and the modulus of elasticity is 115 GPa (16.7 106 psi). (a) What is the maximum load that may be applied to a specimen with a cross-sectional area of 325 mm2 (0.5 in.2) without plastic deformation? - 275 * 325 = 89,375 (b) If the original specimen length is 115 mm (4.5 in.), what is the maximum length to which it may be stretched without causing plastic deformation? - 115 * (1 + 275/115E3) = 115.28 6.15 A cylindrical specimen of aluminum having a diameter of 19 mm (0.75 in.) and length of 200 mm (8.0 in.) is deformed elastically in tension with a force of 48,800 N (11,000 lbf). Using the data contained in Table 6.1, determine the following: (a) The amount by which this specimen will elongate in the direction of the applied stress. - Area = pi r^2 = Pi (9.5)^2 = 283.53 - E = youngs = 69E3 - (48,800 * 200) / (285.53 * 69E3) = 0.50 (b) The change in diameter of the specimen. Will the diameter increase or decrease? - -(0.33 * 19 * 0.498) / 200 = -0.0156 which means it will be decreasing 6.18 A cylindrical specimen of a hypothetical metal alloy is stressed in compression. If its original and final diameters are 20.000 and 20.025 mm, respectively, and its final length is 74.96 mm, compute its original length if the deformation is totally elastic . The elastic and shear moduli for this alloy are 105 GPa and 39.7 GPa, respectively -
6.21 A cylindrical metal specimen 12.7 mm (0.5 in.) in diameter and 250 mm (10 in.) long is to be subjected to a tensile stress of 28 MPa (4000 psi); at this stress level, the resulting deformation will be totally elastic. (a) If the elongation must be less than 0.080 mm (3.2 10-3 in.), which of the metals in Table 6.1 are suitable candidates? Why? - 0.080 / 250 = 3.2E-4 - 28 / 3.2E-4 = 87.5 meaning anything except for aluminum or magnesium. This is determined when we look at table 6.1 (b) If, in addition, the maximum permissible diameter decrease is 1.2 10-3 mm (4.7 10-5 in.) when the tensile stress of 28 MPa is applied, which of the metals that satisfy the criterion in part (a) are suitable candidates? Why? - Because we are given the max permissible diameter we have to use it to find poisson's ratio. - -1.2E-3 / 12.7 = -9.45E-5 - Aluminum = (0.33 * 28E6) / (69 * 10E9) = 1.34E-4 - Magnesium = (0.29 * 28E6) / (45 * 10E9) = 1.80E-4 - Brass = (0.34 * 28E6) / (97 * 10E9) = 9.81E-5 Copper = (0.34 * 28E6) / (110 * 10E9) = 8.65E-5 Nickel = (0.31 * 28E6) / (207 * 10E9) = 4.19E-5 Steel = (0.30 * 28E6) / (207 * 10E9) = 4.06E-5 Titanium = (0.34 * 28E6) / (107 * 10E9) = 8.90E-5 Tungsten = (0.28 * 28E6) / (407 * 10E9) = 1.93E-5 6.27 A load of 85,000 N (19,100 lbf) is applied to a cylindrical specimen of a steel alloy (displaying the stress–strain behavior shown in Figure 6.22) that has a cross-sectional diameter of 15 mm (0.59 in.). (a) Will the specimen experience elastic and/or plastic deformation? Why? - Area = pi (7.5)^2 = 176.71 - 85,000 / 176.71 = 481 When looking at the graph we know that elastic deformation is before the curve begins while elastic + plastic is during the curve. In this case it would be both elastic and plastic. (b) If the original specimen length is 250 mm (10 in.), how much will it increase in length when this load is applied? - 250 * 0.0140 = 3.5mm 6.30 A specimen of ductile cast iron having a rectangular cross section of dimensions 4.8 mm 15.9 mm (3/16 in. 5/8 in.) is deformed in tension. Using the load-elongation data shown in the following table, complete problems (a) through (f) Area: 0.0048 * 0.0159 = 7.63E-5 m
(a) Plot the data as engineering stress versus engineering strain. - Engineering stress = load / area - Engineering strain = (Deformed - original length) / original length Load Length Length change Area Stress Strain 0 7.50E-02 0.00E+00 7.63E+05 0 0.00E+00 4740 7.50E-02 2.50E-05 7.63E+05 6.21E-03 3.33E-04 9140 7.51E-02 5.00E-05 7.63E+05 1.20E-02 6.66E-04 12,920 7.51E-02 7.50E-05 7.63E+05 1.69E-02 9.99E-04 16,540 7.51E-02 1.13E-04 7.63E+05 2.17E-02 1.50E-03 18,300 7.52E-02 1.50E-04 7.63E+05 2.40E-02 2.00E-03 20,170 7.52E-02 2.25E-04 7.63E+05 2.64E-02 2.99E-03 22,900 7.54E-02 3.75E-04 7.63E+05 3.00E-02 4.98E-03 25,070 7.55E-02 5.25E-04 7.63E+05 3.29E-02 6.95E-03 26,800 7.58E-02 7.50E-04 7.63E+05 3.51E-02 9.90E-03 28,640 7.65E-02 1.50E-03 7.63E+05 3.75E-02 1.96E-02 30,240 7.80E-02 3.00E-03 7.63E+05 3.96E-02 3.85E-02 31,100 7.95E-02 4.50E-03 7.63E+05 4.08E-02 5.66E-02 31,280 8.10E-02 6.00E-03 7.63E+05 4.10E-02 7.41E-02 30,820 8.25E-02 7.50E-03 7.63E+05 4.04E-02 9.09E-02 29,180 8.40E-02 9.00E-03 7.63E+05 3.82E-02 1.07E-01 27,190 8.55E-02 1.05E-02 7.63E+05 3.56E-02 1.23E-01 24,140 8.70E-02 1.20E-02 7.63E+05 3.16E-02 1.38E-01 18,970 8.87E-02 1.37E-02 7.63E+05 2.49E-02 1.55E-01
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