Homework03 - CE 3101 Fall 2011 Homework 03 – Locating the...

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Unformatted text preview: CE 3101 Fall 2011 Homework 03 – Locating the Source Due Tuesday, 27 September 2011, 11:59:59 PM (This is a 25 point group assignment.) Abstract In self-selected groups of up to three members, you will write an Excel spreadsheet program to infer the source of an acoustic emission pulse in a standard concrete cylinder. Both the working code and a formal written report are required. Group Evaluation and the Time Card After completing this assignment you are each required to INDIVIDUALLY complete the Homework 03 Group Evaluation , found on the course Moodle web site. One of the components of this evaluation is a reporting of effort. As you will all be required to do in professional practice, in this course you will be responsible for detailed time estimates and time tracking. At the beginning of this homework assignment – after the first reading of the project requirements – record an estimate of the total time necessary to complete the assignment. After the task is complete, record the actual time spent. Time tracking should be recorded to the nearest 15 minutes (1/4 hour). Your time tracking is to be reported via the online questionnaire. Background Acoustic emissions (AEs) are the stress waves produced by the sudden internal stress redistri- bution of the materials caused by the changes in the internal structure. Possible causes of the internal-structure changes are crack initiation and growth, crack opening and closure, dislocation movement, twinning, and phase transformation in monolithic materials and fiber breakage and fiber-matrix debonding in composites. Most of the sources of AEs are damage-related; thus, the detection and monitoring of these emissions are commonly used to predict material failure. Extracted from “Using Acoustic Emission in Fatigue and Fracture Materials Research.” TMS. Web. 14 Sept. 2010. http://www.tms.org/pubs/journals/JOM/9811/Huang/Huang-9811.html . The Wikipedia entry on acoustic emissions is brief but informative 1 ; I recommend that you take a look at it. Problem In this problem you are going to interpret acoustic emission data (also known as micro-seismic data) from the laboratory 2 . Your specimen of interest is a standard concrete cylinder 3 measuring 12 [ in ] (304.8 [ mm ] ) tall and 6 [ in ] (152.4 [ mm ] ) in diameter (see Figure 1). You install N sensors on the outer surface of the cylinder at precisely known cylindrical coordinates 4 : { ( φ 1 , Z 1 ) , ( φ 2 , Z 2 ) ,..., ( φ N , Z N ) } (1) where φ j [ radians ] is the angular location of sensor j , with φ = 0 along the positive X-axis and φ = π/ 2 along the positive Y-axis. The Z-coordinate is the height, in inches, above the base of the cylinder. Thus, the origin of the coordinate system resides at the center point of the bottom face of the cylinder (see Figure 2)....
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Homework03 - CE 3101 Fall 2011 Homework 03 – Locating the...

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