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Title: Energy dissipation in metal matrix composites
Keywords: vibration, damping, internal friction, composite, MMC, anelasticity
Issue Date: 31-Jul-2006
Citation: NARASIMALU SRIKANTH (2006-07-31). Energy dissipation in metal matrix composites. ScholarBank@NUS Repository.
Abstract: Passive damping is a critically important material property from the viewpoint of vibration suppression in aerospace, semiconductor and automotive industries. The ultimate goal is to design and produce materials with high damping. Metals are chosen for such applications since they possess many mechanisms which contribute to the total damping e.g. point defect relaxation, dislocation motion, grain boundary sliding, inclusion-matrix friction, magnetoelastic effects, and elasto-thermodynamic effects. In the present study, effect of the addition of stiff particulates to the metallic matrixa??s overall damping capacity was studied. Such particulates were varied in type of material (ceramic versus metal), morphology (discontinuous versus interconnected) and size (micro size to nano size). Additionally, in the present research, a new methodology of using free-free beam method coupled with circle-fit approach is used to determine damping of ceramic reinforced metal matrix materials. This technique is based on classical vibration theory, by which the geometry and material properties of the metal matrix composites are related to resonant frequency and structural damping of the test specimen. Using the fact that the ratio of the vibration response to the applied force fits to a circle in the Argand plane for each resonant frequency of the test specimen, the damping factor and elastic modulus are predicted accurately for the test specimens. Results confirmed that the presence of stiff reinforcement enhanced the damping characteristics of the ductile matrix. This increase in damping capability of the MMC when compared against the monolithic specimen can be attributed to the increase in dislocation density and presence of plastic zone at the matrix-particulate interface due to thermal mismatch. A novel finite element based numerical model has been formulated that is capable to predict the damping caused due to the micro-plasticity and elasto-thermodynamic damping mechanisms which may help material scientists to formulate new composite formulations in future.Damping results of the nanomaterials containing critical dimensions in nano-regime (viz., nano-grain, nano-particle) were also studied which showed enhanced and interesting results which are in tune with other peculiar properties exhibited by nanomaterials.
Appears in Collections:Ph.D Theses (Open)

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