Assignment_4(2006)

Assignment_4(2006) - ENGINEERING 4032 Materials Science...

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ENGINEERING 4032 Materials Science Assignment #4 13.40 A three-point bending test is performed on a glass specimen having a rectangular cross- section of height d 5 mm and width b 10 mm; the distance between support points is 45 mm. (a) Compute the flexural strength if the load at fracture is 290 N. (b) Compute the point of maximum deflection δ at the center of the specimen at a load of 266 N, given E (the modulus of elasticity) for the glass is 69 GPa (10 x 10 6 psi) 13.D2 It is necessary to select a ceramic material to be stressed using a three-point loading scheme. The specimen must have a circular cross section and a radius of 2.5 mm, and must not experience fracture or a deflection of more than 6.2 x 10 -2 mm at its center when a load of 275 N is applied. If the distance between support points is 45 mm, which of the materials in Table 13.5 are candidates? 13.41 A circular specimen of MgO is loaded using a three-point bending mode. Compute the minimum possible radius of the specimen without fracture, given that the applied load is 425 N, the flexural strength is 105 MPa, and the separation between load points is 50 mm. 1
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7.20 The lower yield point for an iron that has an average grain diameter of 5 x 10 -2 mm is 135 MPa. At a grain diameter of 8 x 10 -3 mm, the yield point increases to 260 MPa. At what grain diameter will the lower yield point be 205 MPa? 7.24 (a) Show, for a tensile test, that if there is no change in specimen volume during the deformation process (i.e., A 0 l 0 = A d l d ). (b) Using the result of part a, compute the percent cold work experienced by naval brass (the stress–strain behavior of which is shown in Figure 6.12) when a stress of 400 MPa (58,000 psi) is applied. 7.25 Two previously undeformed cylindrical specimens of an alloy are to be strain hardened by reducing their cross-sectional areas (while maintaining their circular cross sections). For one specimen, the initial and deformed radii are 16 mm and 11 mm, respectively. The second 2
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specimen, with an initial radius of 12 mm, must have the same deformed hardness as the first specimen; compute the second specimen’s radius after deformation. 7.36 The average grain diameter for a brass material was measured as a function of time at 650ºC, which is tabulated below at two different times: (a) What was the original grain diameter? (b) What grain diameter would you predict after 150 min at 650ºC? 7.39 An uncold-worked brass specimen of average grain size 0.008 mm has a yield strength of 160 MPa. Estimate the yield strength of this alloy after it has been heated to 600ºC for 1000 s, if it is known that the value of k y is 12.0 MPa-mm 1/2 . 3
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9.10 Below is a portion of the H 2 O–NaCl phase diagram: (a) Using this diagram, briefly explain how spreading salt on ice that is at a temperature below 0ºC can cause the ice to melt. (b) What concentration of salt is necessary to have a 50% ice–50% liquid brine at -10ºC?
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Assignment_4(2006) - ENGINEERING 4032 Materials Science...

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