(7) Most of the gas pipe explosions we discussed in the class very likely occurr
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Question
(7) Most of the gas pipe explosions we discussed in the class very likely occurred when the atmospheric (or ground) temperature (a) went above the melting temperature of the pipes, (b) went below the freeing temperature of the pipes, (c) went below the brittle-ductile transition temperature, (d) below the Brill-transition temperature of the pipes (8) An isotropic material with a Poisson's ratio 0.3 is subjected to a stress of 10' psi in the axial direction. Its modulus of elasticity is 10* psi, then the magnitude of lateral (perpendicular to the axial direction) strain is: (a) 0.3 (b) 0.03, (c) 3 (d) 0.003 (9) For a material with a critical stress intensity factor Kie for all types of cracks, an engineer found two cracks at two different locations -a tunnel crack and a penny crack. For an applied stress of o, which statement is the best regarding which crack is the critical one (meaning with the same crack size, which would initiate fracture): (a) tunnel crack, (b) penny crack, (c) both are equal in this regard, (d) none of these, we need a wedge-opened crack (10) If the critical stress intensity factor for a tunnel crack Kic is 30 MPa-m/2 with an yield strength of 500 MPa. If the thickness of this material is 1 cm, what is the applied stress when it fails under fracture if the tunnel crack has a length of length 2a = 0.02/ meters? (a) 30 MPa (b) 300 MPa (c) 300/T MPa (c) 100/TExplanation / Answer
7)
option C) is correct because when the brittle-ductile transition material will burst on ductile side
8)
lateral strain = 0.3*107/108 = 0.03 option B
9) INTENSITY FACTOR IS SEME , HENCE OPTION C is correct.
10) C
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