MATLS 1M03 - WebCT - Assignment 5 - Try 4

MATLS 1M03 - WebCT - Assignment 5 - Try 4 - Learning System...

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View Results Name: SIAMAK KIANI Attempt: 1 / 3 Out of: 15 Started: March 23, 2009 6:41pm Finished: March 25, 2009 2:31am Time spent: 31 hr, 50 min., 9 sec. Question 1 (1 point) Which kind of fracture is associated with the transgranular crack propagation mechanism? Student response: Correct Response Student Response Answer Choices a. Ductile b. Brittle c. Either ductile or brittle General feedback: Transgranular fractures are brittle in nature, and crack propagation is through the grains. For more information, see the section on Brittle Fracture in the text. Score: 1 / 1 Question 2 (1 point) A brittle polymer component that has a surface crack length of 0.310 mm must not fail when a tensile load is applied. Determine the maximum stress (in MPa) that may be applied if the specific surface energy of this polymer is 0.483 J/m 2 . Assume an elastic modulus of 305 GPa. Use decimal notation, digits after decimal: 1 Student response: 1.7 MPa Correct answer: 17.4 MPa General feedback: See equation 8.3 in the text. Score: 0.1 / 1 Question 3 (1 point) The fracture strength of glass may be increased by etching away a thin surface layer. It is believed that the etching may alter the surface crack geometry (i.e. reduce crack length and increase tip radius). Calculate the ratio of the original to the etched crack tip radius if the stress concentration factor is increased by a factor of 2.45 when 26.1% of the crack length is removed. Use decimal notation, digits after decimal: 2 Student response: 4.44 Correct answer: 4.44 General feedback: Using equation 8.2 in the text, rearrange to solve for the original crack tip radius ρ t 1 . Using equation 8.2 again, multiply Kt by the factor of increase and
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This note was uploaded on 02/08/2010 for the course MATLS 1M03 taught by Professor Okon during the Winter '09 term at McMaster University.

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MATLS 1M03 - WebCT - Assignment 5 - Try 4 - Learning System...

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