Authors: Li Ming Yu, Yue Ma, Chun Gen Zhou, Hui Bin Xu
3971
Authors: Joong Hwan Jun, Bong Koo Park, Jeong Min Kim, Ki Tae Kim, Woon Jae Jung
Abstract: Microstructures and damping properties of semi-solid AM50 (Mg-5%Al-0.3%Mn) alloy were
investigated and compared with those of die-cast AM50 alloy, based on experimental results of X-ray
diffractometry (XRD), optical microscopy (OM), hardness tests and damping tests in a flexural mode.
The semi-solid AM50 specimens show higher damping capacity than die-cast one in as-fabricated state,
and the higher the fraction of solid α-(Mg), the greater the damping capacity. The annealing at 200oC
deteriorates the damping properties of the semi-solid and die-cast specimens. This would be due to the
segregation of solute atoms on dislocation lines, which eventually leads to lower internal friction by the
restriction of dislocation movement. The peak damping values of the AM50 specimens are obtained after
annealing at 400oC. The disappearance of segregates acting as pinning points of dislocations is thought
to be responsible for the improvement in damping capacity. This result implies that the presence of solid
α-(Mg) phase and annealing treatment at high temperature are beneficial to damping property of AM50
alloy.
292
Authors: Zhen Yan Zhang, Li Ming Peng, Xiao Qin Zeng, Lin Du, Lan Ma, Wen Jiang Ding
Abstract: Effects of extrusion on mechanical properties and damping capacity of Mg-1.8wt.%Cu
-0.5wt.%Mn (MCM1805) alloy have been investigated. Tensile tests and dynamic mechanical
analyzer were respectively used to measure tensile properties and damping capacity at room
temperature of as-cast and as-extruded MCM1805 alloy. The microstructure was studied using optical
microscope, X-ray diffraction and scanning electron microscope with an energy dispersive X-ray
spectrometer. Granato-Lücke model was used to explain the influences of extrusion on damping
capacity of MCM1805 alloy. The results showed that extrusion dramatically decreases the grain size
but has little influence on phase composition and solute atoms concentration of MCM1805 alloy, and
the grain refinement was the dominant reason for the obvious increase of tensile properties and
decrease of internal friction of MCM1805 alloy.
257
Authors: Yue Ying Li, Yong Bing Liu, Zhan Yi Cao
Abstract: The stir-casting method was utilized in this paper to synthesize 6063Al/Al2O3·SiO2
reinforced composites consisting of 6063Al alloy as matrix and Al2O3·SiO2 particles as additive with
content of 5%, 10%, 15%, 20% (volume fraction) respectively. Al2O3·SiO2 particles were obtained
from fly ash particles of Steam Power Plant and were pretreated. The shape of these fly ash particles
was spheroidal and ellipsoidal. The damping behavior of 6063Al/Al2O3·SiO2 particle reinforced
composites was studied by measuring the composite’s internal friction values on a Multifunctional
Damping Measurement Apparatus. Under the condition of this series of experiments,
6063Al/Al2O3·SiO2 particle reinforced composites had a higher internal friction values than that of
6063Al matrix and also showed the dependency of internal friction on Al2O3·SiO2 particles volume
fraction, particles dimension, vibration frequency and temperature. There was an increased trend for
internal friction values with increasing the volume fraction of Al2O3·SiO2 particles and decreasing
particles dimension of Al2O3·SiO2 at the same frequency and the different temperature. It has been
found that in the lower frequency, the higher internal friction value was obtained. The internal friction
of the composites increased with increasing temperature. In the case of lower frequency, two damping
peak were observed. A low-temperature damping peak appeared at a temperature near 245°C which a
high-temperature damping peak appeared near 450°C. Based on the experimental results, the
damping mechanism of 6063Al/Al2O3·SiO2 particle reinforced composites was preliminary
discussed. It may be concluded that the damping mechanisms associated with 6063Al/Al2O3·SiO2
reinforced composites include mainly intrinsic damping, dislocation damping and interface damping.
However, only the interface damping mechanism is dominant at high temperature.
633
Authors: Xiao Yuan Pei, Jia Lu Li
Abstract: The modal properties of carbon fiber woven fabric / epoxy resin composites with different fiber orientation angles were studied by using single input single output free vibration of cantilever beam hammering modal analysis method. With the same fiber volume fraction, the different fiber orientation of the laminated composite has an effect on parameters of vibration mode of composites. The experimental results show that with the fiber orientation increasing, the natural frequency of laminated composites becomes smaller and damping ratio becomes larger. The fiber orientation smaller, the peak value of natural frequency becomes higher and the attenuating degree of acceleration amplitude becomes slower.
345
