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MATLS 1M03 - WebCT - Assignment 5 - Try 2

# MATLS 1M03 - WebCT - Assignment 5 - Try 2 - WebCT Quiz...

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WebCT Quiz Homepage http://webct.mcmaster.ca/SCRIPT/MATLS_1M03_T2_07/scripts/student... 1 of 5 3/24/2007 12:05 AM View Results Assignment 5 (Ch 8 & 9) Name: AARON MURENBEELD Attempt: 2 / 3 Out of: 11 Started: March 23, 2007 11:59pm Finished: March 24, 2007 12:05am Time spent: 5 min. 25 sec. Question 1 (1 point) Which kind of fracture is associated with the intergranular crack propagation mechanism? Student response: Correct Response Student Response Answer Choices a. Ductile b. Brittle c. Either ductile or brittle General feedback: Intergranular fractures are brittle in nature, and crack propagation is along grain boundaries . For more information, see the section on Brittle Fracture in the text. Score: 1 / 1 Question 2 (1 point) Suppose that a mechanical component on an aircraft is fabricated from an alloy that has a plane-strain fracture toughness of 41.6 MPa-m 1/2 . It has been determined that fracture results at a stress of 105 MPa when the maximum (or critical) internal crack length is 8.38 mm. For this same component and alloy, what is the maximum allowable stress level (in MPa) when the critical internal crack length is 5.33 mm? Use decimal notation, digits after decimal: 0 Student response: MPa Correct answer: 132 MPa General feedback: Use equation 8.5 in the text to solve for the parameter Y. Then use the same equation to solve for σ with a new crack length. Assume Y and K Ic remain constant. Score: 0.1 / 1 Question 3 (1 point) A structural component is fabricated from an alloy that has a plane strain fracture toughness of 46.6 MPa-m 1/2 . It has been determined that this component fails at a stress of 149 MPa when the maximum length of a surface crack is 2.13 mm. What is the maximum allowable surface crack length without fracture for this same component that is made from another alloy that has a plane strain fracture toughness of 54.5 MPa-m 1/2 ?

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