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MATLS 1M03 - WebCT - Assignment 5 - Try 5

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

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View Results Assignment 5 (Ch 8 & 9) Name: SIAMAK KIANI Attempt: 2 / 3 Out of: 15 Started: March 25, 2009 2:38am Finished: March 25, 2009 2:56am Time spent: 18 min. 15 sec. Question 1 (1 point) True or False? The degree of brittleness of a material is not a function of temperature. Student response: Correct Response Student Response Answer Choices a. True b. False General feedback: False . Most materials become more ductile as the temperature increases. For more information, see the section on Fundamentals of Fracture in the text. Score: 1 / 1 Question 2 (1 point) What is the magnitude of the maximum stress (in MPa) that exists at the tip of an internal crack having a radius of curvature of 1.75 x 10 -4 mm and a crack length of 0.393 mm when a tensile stress of 153 MPa is applied? Use scientific notation, significant figures in answer: 3 Student response: Not answered Correct answer: 1.03E4 (1.03 * 10 4 ) MPa General feedback: See equation 8.1 in the text. Remember that a = half the internal crack length. Score: 0 / 1 ( Question not answered. ) Question 3 (1 point) For a metal that has a yield strength of 181 MPa and a plane strain fracture toughness K Ic of 48.8 MPa*m 1/2 , compute the minimum component thickness (in mm) for which the condition of plane strain is valid. The thickness B for which the condition of plane strain is valid may be computed using the following equation: Use decimal notation, digits after decimal: 0 Student response: Not answered Correct answer: 182 mm General feedback: Use the equation given to solve for B . Score: 0 / 1 ( Question not answered. ) Question 4 (1 point) A fatigue test was conducted in which the mean stress was 49 MPa and the stress amplitude was 191 MPa. Calculate the minimum stress level (in MPa).
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