Key Engineering Materials Vol. 319

Abstract: Internal friction in ultra-fine grained Mg with 3vol% of Graphite was measured by forced vibration method at low frequencies of 0.1, 0.5, 1.0, and 2.0 Hz over a temperature range from room temperature to 753 K with continuous heating. The specimens were prepared by milling procedure in an inert atmosphere and subsequent compacted and hot extruded. Two developed peaks in the internal friction spectrum were obtained at temperatures ≈ 350 K and ≈ 550 K. While the position of the first peak is frequency dependent, the second peak position is stable, independent of measuring frequency. The activation energy of the low temperature peak was estimated. In the light of internal friction measurements, the high temperature internal friction peak is attributed to the generation and motion of dislocations produced by the difference in the coefficient of thermal expansion between the Mg matrix and Gr phase at the matrix–particle interfaces.

Abstract: Due to the recent earthquakes in the U.S. and Japan, many modern buildings ceased functioning and required costly structural and nonstructural repairs, although they successfully protected the lives of the occupants. Because of these, most major buildings constructed after the earthquakes utilize either passive-control scheme or base-isolation scheme in order to better protect the building and its contents. This paper addresses current status of passive control technology being implemented in Japan. Four major groups of dampers and their basic mechanisms are discussed. Three groups of frames are explained, referring to different connection schemes and deformation lags between the frame and damper. A unified approach to assess effectiveness of various dampers and frames will be presented.

Abstract: Fe-12Cr-22Mn and Fe-12Cr-22Mn-2Co (High Damping Stainless Alloy HIDAS) were developed and applied for suppression of noise or vibration. Since these alloys have high strength (1400Mpa) as well as high damping capacity (10
20) due to/ interface, their direct replacements for the parts of machines were possible. In this respect, the applications were tried mainly to machineries and nanotechnologies. Those were bolt and nut, gear, bite shank, cutting tool of numerically controlled (NC) machine, brake and arm of hard disk drive (HDD) and others. In those applications, all data obtained showed better results compared with other materials. Cost down and quality control would be the remaining problems.

Abstract: Although the high damping alloy M2052, which has been developed 10 years go, possesses both of very high damping capacity and excellent workability, it has been used only in the field of an audio/video field. If this alloy will be produced by combining high-quality raw material and optimum manufacturing processes, the damping capacity of 0.72 in logarithmic decrement that is near to that of rubber can be yielded. In addition, since workability is very excellent, the sizes and shapes of parts required for anti-vibration measures can be easily supplied, thus being able to satisfy to create all sorts of items necessary for the design of the measures. In this paper, we show how to use this alloy and some examples of application: a multi-axis with non-rotating grinding machine, bearing and boring machines, a surface grinder, coiled springs, and an installation mount. Many of excellent effects of damping provided by the applications such as an insert, a carpet, and a variety of new ideas to decrease a spring constant of parts suggest possibility to solve the hard problem which was not solved by rubber.

Abstract: Different viewpoints at high damping materials - from engineering needs to physical mechanisms are discussed. It is suggested that only several mechanisms in metallic materials can lead to high intrinsic damping capacity while some other “peak-like” effects are not sufficient to make high damping materials.

Abstract: A new algorithm OMI (Optimization in Multiple Intervals) for the computation of the logarithmic decrement from exponentially damped harmonic oscillations is described. This method is shown to be effective and computationally compact for high damping materials. A comparison between the OMI algorithm and the four classical methods usually used in the computation of the logarithmic decrement is reported. The OMI algorithm yields high precision in the computation of the logarithmic decrement and the smallest dispersion of experimental points on the plots of mechanical loss spectra. The effect of the acquisition parameters and the experimental conditions on the results of computations of the logarithmic decrement and the relative error is discussed.