Discontinuous reinforced aluminum (DRA) metal matrix composites are a part of a promising class of advanced materials with potential use in applications requiring high stiffness and strength, low weight and superior stress-controlled fatigue properties. The fatigue resistance of DRA is largely influenced by the nucleation and growth of a very large number of microcracks. This high density of microcracks leads to widespread coalesence and ultimately the formation of the fatal crack. The interval from which the fatal crack grows as a long crack and can be detected by nondestructive evaluation (NDE) is relatively short. As a result, the use of deterministic long crack methods such as the Paris equation for inspection scheduling is not always reliable. Quality assurance inspections, however, can be improved and made more cost effective if the microcrack length distributions (MLD) at various stages in fatigue are known. Such information pinpoints the timing for NDE inspection and prescribes the sensitivity of crack detection depending on needed reliability. This study presents experimental data and a reliability inspection philosophy for MLD in DRA. The initiation, growth, and distribution of surface microcracks are examined on smooth specimens of a 2124 aluminum alloy reinforced with SiC whiskers fatigued at different stress levels. To demonstrate this approach, a simple Monte Carlo simulation was constructed. The simulation provides a means of estimating the likelihood of cracks of a particular length initiating in a given part of a component as a function of fatigue loading and number of cycles. The methodology presented in this study encompasses not only DRA, but should also be useful for advanced materials in which high strength is achieved at the expense of some ductility.
Fatigue of discontinuous reinforced aluminium metal matrix composites: challenges facing nondestructive evaluation
Die Werkstoffermüdung von ungleichmäßig verstärkten Aluminium Metallmatrix-Verbundstoffen: Die Bewertung der Deckschicht mittels zerstörungsfreier Prüfung
1994
8 Seiten, 6 Bilder, 42 Quellen
Aufsatz (Konferenz)
Englisch
Schadenfrüherkennung , Automobilindustrie , Verbundwerkstoff , Aluminium , Matrix (Grundmasse) , Werkstoffprüfung , Werkstoffermüdung , Inspektionszeit , Prozessoptimierung , Gewichtsverminderung , Rissprüfung , Rissbildung , Rissausbreitung , Mikroriss , Monte-Carlo-Methode , Prognose , Wirtschaftlichkeit , Zeiteinsparung , Optimierung , Grundwerkstoff , Ermüdung , Riss , Simulation
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