REG NASA-LLIS-0508-1994 Lessons Learned - Determining the Angle of Impact of an Object on a Thin-Walled Structure through Analysis of Acoustic Waves.pdf

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1、Lessons Learned Entry: 0508Lesson Info:a71 Lesson Number: 0508a71 Lesson Date: 1994-25a71 Submitting Organization: LARCa71 Submitted by: Bernard LewisSubject: Determining the Angle of Impact of an Object on a Thin-Walled Structure through Analysis of Acoustic Waves Description of Driving Event: Curr

2、ently, only one method is available for determining an objects angle of impact against a structure: high speed photography. This method requires a great deal of equipment and produces data, which requires a great deal of time to analyze. Presently, the acoustic emission technique is being used to as

3、sess damage caused by the impact of an object. As now used, this technique does not provide information concerning the angle of impact. However, a patent was granted on 3-2-93 for a method for determining the angle of impact of an object on a thin-walled structure through analysis of the acoustic wa

4、ves which result when the object impacts. Transducers are placed on and in the surface of the structure which sense the impact waves caused in the structure. The waves are recorded and saved for analysis. For source motion normal to the surface, the antisymmetric mode has a large amplitude while tha

5、t of the symmetric mode is very small.As the source angle increases with respect to the surface normal, the symmetric mode amplitude increases while the antisymmetric mode amplitude decreases. Thus, the angle of impact is determined by measuring the relative amplitudes of these two lowest order mode

6、s.Lesson(s) Learned: Through analysis of the acoustic waves which result from impact, it is now possible to determine the angle of impact of an object on a thin-walled structure.Recommendation(s): A patent was granted on 3-2-93 to William H. Prosser, NASA Langley Research Center, Hampton, Virginia,

7、23665; and, Michael R. Gorman, Aeronautics and Astronautics, Naval Postgraduate Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-School, Monterey, California, 93943 for this method of measurement.Evidence of Recurrence Control Effectiveness: N/ADocume

8、nts Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s): a71 Research & DevelopmentAdditional Info: Approval Info: a71 Approval Date: 1997-02a71 Approval Name: Elijah C. Kenta71 Approval Organization: 421a71 Approval Phone Number: 757-864-3345Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-