Characteristics estimation f or sintered materials by analyssis of frequency response function of mechanical bivration.

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Taking note of the fact tht precise higher order resonant frequency can be detected simply by using Fast Fourier Transform (FFT) analyzer, some attempts were made to estimate both densities and elastic moduli for the sintered iron compacts and 2024 Al alloy sintered compacts. The results obtained were as follows ;(1) Three spectrums of resonant frequencies were observed by bending vibration method. Rigid linear relationship was obtained between these resonant frequencies and sintered resonant frequency was the largest among three specturns, which seems to be advantageous for estimating the sintered density.(2) Considerable difference in elastic modulus for the sintered iron compacts was found between present and already reported results.(3) In the strain-amoplitude-independent part, the Q^<-1> measured is 1.5^-8.1x10^<-3>, which is about 10 times higher than the value of sintered iron. Moreover, after T6 treating these materials, they were found to have an even higher Q^<-1> than the as sintered materials.(4) An increase in Cu content resulted in a decrease in the Q^<-1> of both the as-sintered and T6 treated materials.(5) Damping mechanisms appeared to be relaxation due to dislocation motion and reversible multiphase boundary sliding.(6) Changes in fr during vibration at a constant amplitude correspond to those in the internal friction (Q^<-1>), and amarked decrease in Q^<-1> occurs as a result of the formation of fatigue cracks. These cracks propagate mainly along grain boundaries in as-sintered specimens, and transgranularly in T6 treated ones.