| Acoustic Emission Monitoring of Damage in Metal-Matrix Composites Subjected to Thermomechanical Fatigue. |
1994 |
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| Authors:
R. W. Neu; I. Roman; WRIGHT LAB WRIGHT-PATTERSON AFB OH MATERIALS DIRECTORATE
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 | Acoustic emission (ae) was monitored during thermomechanical fatigue (tmf) tests conducted on a silicon carbide fiber, titanium alloy matrix composite, scs-6/timetal 21s. the tests were stress-controlled with a stress ratio of 0-1, and temperature was cycled from 150 to 650 c. in-phase and out-of-phase tmf cycling were characterized by distinct ae behavior. the rate of fiber fractures as indicated by ae during in-phase cycling was much higher than during out-of-phase ... |
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| Microstructure, Tensile Ductility, and Fracture Toughness of Ti-25Al-10Nb-3V-1Mo. |
1993 |
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| Authors:
C. H. Ward; I. Roman; J. C. Williams; A. W. Thompson; WRIGHT LAB WRIGHT-PATTERSON AFB OH
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| This paper investigates the fracture toughness, microstructure, and tensile ductility of Ti-25Al-10Nb-3V-1Mo alloy. Room temperature tensile and fracture tests were carried out. Failure was found to be preceded by little acoustic emission activity, indicating that failure is controlled by crack nucleation. The length of slip bands that formed during plastic deformation controlled fracture stress. |
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| Fiber-Matrix Interfacial Behavior in SiC-Titanium Alloy Composites. |
1993 |
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| Authors:
I. Roman; S. Krishnamurthy; D. B. Miracle; HEBREW UNIV JERUSALEM (ISRAEL)
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| This paper concerned mmc in some important way and contained information about, utilized, or discussed these subjects: basic topics:, cr mmc, data, mmc, mmc data materials and material types:, (sic)f/ti, (sic)f/ti-14-21, (sic)f/ti-6-4, fibers, scs-6 fibers, scs-6/ti, scs-6/ti-14-21, scs-6/ti-6-4, sic fibers, sic/ti, sic/ti-14-21, sic/ti-6-4, ti matrix, ti-14-21 matrix, ti-6-4 matrix material characteristics and data fields:, interfacial microstructures, stress-strain data testing and test conditions:, single fiber fragmentation test, tensile tests miscellaneous and ... |
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| Creep Behavior of SCS-6/Ti-6Al-4V Unidirectional Composites. |
1993 |
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| Authors:
S. W. Schwenker; I. Roman; D. Eylon; AIR FORCE WRIGHT AERONAUTICAL LABS WRIGHT-PATTERSON AFB OH
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| This paper concerned mmc in some important way and contained information about, utilized, or discussed these subjects: basic topics:, data, experimental, mmc, mmc data, models materials and material types:, (sic)f/ti, (sic)f/ti-6-4, fibers, scs-6/ti, scs-6/ti-6-4, sic/ti, sic/ti-6-4, ti-6-4 matrix material characteristics and data fields:, creep behaviors, creep data, creep resistances, creep strains, fractures, modulus data, uts data, yield strength data testing and test conditions:, ae, ae monitoring, creep tests manufacturing:, cvd ... |
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| Acoustic Emission Characterization of Damage Evolution During Tensile Testing of SiC/BMAS Ceramic Composites, |
1992 |
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| Authors:
I. Roman; L.P. Zawada
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| Glass-ceramic matrices reinforced with ceramic fibers are candidates for replacing traditional structural materials in 21st century gas turbines and aerospace structures. These materials are intended for elevated temperature applications as they retain their high specific strength and stiffness and possess adequate toughness at high service temperatures. A limited number of studies have characterized the mechanical properties of this emerging class of advanced materials at elevated temperatures in monotonic tension. Thus, ... |
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| Characterization of Fiber Failure in Graphite-Epoxy Composites, |
1992 |
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| Authors:
A. Mittelman; I. Roman
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| An approach that includes utilizing the moments of the Peak Amplitude Distribution (PAD) of the Acoustic Emission (AE) activity for damage mechanisms characterization in fiber reinforced composites (FRP) has been employed. The objective of this research was to distinguish between fibers and non-fibers damage mechanisms. This was conducted by analyzing the statistical moments value of the PAD. Unidirectional graphite-epoxy tensile specimens with fiber volume fraction of 0.55 manufactured by filament ... |
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| Interfacial Shear Properties and Acoustic Emission Behavior of Model Aluminum and Titanium Matrix Composites, |
1992 |
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| Authors:
I. Roman; S. Krishnamumurthy; D.B. Miracle
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| Interfaces between matrix and reinforcement play a critical role in determining the mechanical properties of intermetallic and metal matrix composites (IMC's and MMCs), which are potential candidates for advanced aerospace structural applications due to increased specific strength when compared to monolithic alloys. However, experimental techniques capable of determining interfacial mechanical properties of MMCs are not yet sufficiently established. Fiber push-out and fragmentation testing techniques have been developed and employed to ... |
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| Mechanical Interrogation of Interfaces in Monofilament Model Composites of Continuous SiC Fiber-Aluminum Matrix. |
1992 |
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| Authors:
I. Roman; R. Aharonov; HEBREW UNIV JERUSALEM (ISRAEL) GRADUATE SCHOOL OF APPLIED SCIENCE AND TECHNOL OGY
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| The interfacial region between continuous sic fiber and aluminum alloy matrix, in a monofilament metal matrix composites (mmc), has been characterized. the study utilized two sic fibers, produced by textron (scs-2) and sigma and two aluminum alloys: al1100 and al6061. characterization methods employed included: optical and electron microscopy (i.e. sem and epma), mechanical testing of as-received and heat treated single fiber samples and monitoring of acoustic emission (ae) during tensile ... |
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| Distinguishing Acoustic Emission Generated by Actual Damage Progression from Non-Relevant AE in Graphite Epoxy Composites, |
1989 |
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| Authors:
A. Mittelman; I. Roman
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| It is well established that the amount of non-relevant AE generated by friction, is a significant amount of the total emission, and in most cases even exceed that caused by actual damage progression in graphite-epoxy composites. In the work reported here, we have employed our approach of utilizing statistical moments of the peak amplitude distribution (PAD) in order to distinguish between actual and non-relevant AE. Unidirectional graphite-epoxy tensile samples, having ... |
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| Ductility and Precipitation in Sintered Tungsten Alloys, |
SEP 1986 |
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| Authors:
D. Rittel; I. Roman
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| The effects of post-sintering heat treatments were studied employing two tungsten alloys. For the first alloy, a typical heavy alloy with 90 wt.% W, heat treatments (T > 600 C) resulted in improved tensile ductility. For the second alloy, the composition of which was similar to that of the matrix phase of a heavy alloy, heat treatments resulted in age hardening as a result of precipitation phenomena, none of which ... |
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Reports by Author
