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Record 1 of 3573
An investigation of theories of failure for ceramic matrix composites
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Author and Affiliation:
Hemann, John H.(Cleveland State Univ., OH, United States)
Abstract: This final report is comprised of the abstract of a masters thesis research grant. The abstract of the thesis, 'An Investigation of Acoustic Emission Techniques for the Discrimination of Damage Mechanisms in Ceramic Matrix Composites', is as follows: In order to further advance the understanding of the mechanical behavior of ceramic matrix composites (CMS's), acoustic emission (AE) techniques were implemented to monitor and identify damage mechanisms in CMC's under tensile loading. In addition to real-time AE monitoring techniques, a data acquisition system was developed and implemented in order to capture AE waveforms resulting from stress-induced damage. Waveforms were inspected for multiple events, separated in distinct events, and then analyzed to determine waveform characteristics in the time and frequency domains. Waveform characteristics included peak amplitude, event duration, MARSE, energy, and dominant and centroidal frequency. In addition to conventional methods for determining a damage discrimination criteria, a study of the distribution and correlation of the waveform characteristics criteria and a study of the distribution and correlation of the waveform characteristics were performed to aid in the determination of a damage discrimination criteria. The damage discrimination criteria was tested for 'uniqueness', i.e., the effectiveness of the criteria to identify and monitor damage independent of the stress-strain relationship. Insitu radiography was used to substantiate the damage accumulation. A simulation test was also performed over the loading history to study the changes in the waveform characteristics of the system response from a constant excitation. This thesis demonstrates the use of waveform analysis to study the AE activity resulting from stress-induced damage in CMC's in conjunction with other nondestructive evaluation techniques to investigate the mechanical behavior of CMC's.
Publication Date: Jul 21, 1995
Document ID:
19960011869
(Acquired Feb 16, 1996)
Accession Number: 96N70754
Subject Category: NONMETALLIC MATERIALS
Report/Patent Number: NASA-CR-200135, NAS 1.26:200135, NIPS-96-07896
Coverage: Final Report; 15 Jun. 1993 - 21 Jul. 1995
Document Type: Technical Report
Publisher Information: United States
Contract/Grant/Task Num: NCC3-306
Financial Sponsor: NASA; United States
Organization Source: Cleveland State Univ.; OH, United States
Description: 4p; In English
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: No Copyright
NASA Terms: ACOUSTIC EMISSION; APPLICATIONS PROGRAMS (COMPUTERS); CERAMIC MATRIX COMPOSITES; CUMULATIVE DAMAGE; DAMAGE ASSESSMENT; IMPACT LOADS; MECHANICAL PROPERTIES; NONDESTRUCTIVE TESTS; STRESS-STRAIN RELATIONSHIPS; WAVEFORMS; COMPUTERIZED SIMULATION; DATA ACQUISITION; FATIGUE TESTING MACHINES; IN SITU MEASUREMENT; RADIOGRAPHY; REAL TIME OPERATION; SOFTWARE ENGINEERING; UNIQUENESS
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