MATLS 1M03 - WebCT - Assignment 5 - Try 1

MATLS 1M03 - WebCT - Assignment 5 - Try 1 - 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 12:01 AM View Results Name: AARON MURENBEELD Attempt: 1 / 3 Out of: 11 Started: March 13, 2007 10:12pm Finished: March 23, 2007 11:58pm Time spent: 241 hr, 46 min., 4 sec. Question 1 (1 point) The effect of a stress raiser is more significant in which of type of material? Student response: Correct Response Student Response Answer Choices a. Brittle materials b. Ductile materials General feedback: The effect of a stress raiser is more significant in brittle materials . In a ductile material, plastic deformation occurs in the vicinity of the stress raiser. That leads to a more uniform distribution of stress and a maximum stress concentration factor that is less than the one predicted by theory. This phenomenon does not occur in brittle materials. For more information, see the section on Stress Concentration in the text. Score: 0 / 1 Question 2 (1 point) A structural component is fabricated from an alloy that has a plane strain fracture toughness of 38.8 MPa-m 1/2 . It has been determined that this component fails at a stress of 178 MPa when the maximum length of a surface crack is 1.32 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 41.0 MPa-m 1/2 ? The components will all be subject to the same amount of stress while in use. Use decimal notation, digits after decimal: 2 Student response: 1.47 mm Correct answer: 1.47 mm General feedback: Recall that Y is dependent on specimen sizes and geometries, so for a structural component this would be constant, even if it was made out of a different material. The components will all experience the same amount of stress while in use, so the applied stress will not exceed 178 MPa in the second alloy. Use equation 8.5 to solve for Y, and then equation 8.7 to find the maximum allowable crack length in
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MATLS 1M03 - WebCT - Assignment 5 - Try 1 - WebCT Quiz...

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