Abstract: The Laboratory Soete developed a new test setup, based on the well-known pin-on-disc test rig. Instead of the standard composite specimen and steel disc, a rotating composite disc and a steel pin is presently used to have a visible wear track. Other measurement techniques (Acoustic Emission, vibrations, temperature) can be used on the test rig. Continuous monitoring of the wear track combined with standard wear and friction measurements, give results of the current state of the wear track. Fourier frequency analysis (FFT) of these signals gives an indication of the change in condition and contact geometry of the resulting pin-disc combination. A high-speed camera will be used to acquire digital images of the worn composite surface. These online measurements yield to the gradual evolution in damage of the composite specimens.
Abstract: The electromechanical properties of cymbal piezocomposite transducer were investigated in this paper. Piezoelectric ceramic PZT—5A was used as piezoelectric phase of transducer, and brass foil was used as end cap electrode of cymbal piezocomposite transducer. Several types of this transducer were fabricated. The displacements of this transducer as functions of the applied force and the applied electric field were investigated. It was calculated and analyzed for the energy
transmission coefficient and electromechanical coupling coefficient of this transducer which optimum values were obtained.
Abstract: The deformation and fracture behavior at 1773-2023K of the unidirectionally solidified
eutectic Al2O3/YAG (Yttrium-Aluminum Garnet with the composition of Y3Al5O13) ceramic composite was investigated. The stress-stain curve and strength of unnotched and notched specimens, measured by bending and tensile tests, showed that (a) both unnotched and notched specimens fractured in a brittle manner at low temperatures and at high displacement speeds, but in a ductile manner at high temperatures and at low displacement speeds, and (b) the notched strength increased, reaching maximum, and decreased with increasing temperature and decreasing displacement speed. The increase in the notched strength with increasing temperature and decreasing displacement speed up to the maximum value was accounted for by the increase in plastic zone size ahead of the notch,
and the decrease with further increasing temperature and decreasing displacement speed by the loss of the stress carrying capacity of the yielded ligament, based on the finite element analysis.
Abstract: Grazing-incidence small-angle scattering (GI-SAXS) technique was applied to self-assembled Ge islands capped with Si. GI-SAXS has a merit over TEM and AFM that the structure of islands buried in a cap layer for stabilization can be evaluated nondestructively. By analyzing the scattering patterns, the size of Ge islands was estimated to be about 5 nm in height and 26 nm in diameter, with the islands density of 4.2×1014/m2. From the best fitting of two-dimensional model intensity to the experiments, the shape of the islands was deduced
Abstract: It has been reported that SiC/SiC composite has high strength and toughness, but is
degraded when exposed in air at high temperatures due to the propagation of the crack made by the premature fracture of the SiO2 layer. The present work aimed to describe such a behavior with a computer simulation. For this aim, the shear lag - Monte Carlo simulation method was applied. The variation of strength of the composite as a function of thickness of the SiO2 layer and change of fracture morphology with progressing oxidation could be reproduced satisfactorily by this method.
Abstract: C/C composites have the phenomenon of the decrease of friction coefficient in wet
conditions, companied with the change of wear behavior. In this paper, the effect of
micro-tissue and density on the tribology behavior of C/C composites in wet conditions has been studied. The results indicate that all the above factors influence the tribology behavior of C/C composites at a different degree. It is believed that all the above factors change the ability of absorbing water by the C/C composites. The different degree of water absorption in turn changes the tribology mechanisms of C/C composites resulting in the change of tribology behavior of the C/C composites.
Abstract: Traditionally, automotive brake rotors are made with cast iron. Besides having
economical advantage, cast iron rotor provides many disadvantages due to its weight, such as reduction in fuel efficiency, increase in green house gas emission, and increase in noise, vibration and hardness. With the development of commercial aluminum composites, composite brake rotors are now manufactured. However, the present commercial composite materials are not specifically made for brake application and there are drawbacks. A major drawback is their poor elevated temperature property. In this paper, the unique properties offered by an aluminum composite for brake application is addressed, and an approach to compensate its properties for brake application is highlighted.
Abstract: A smart material is used as spectacle frames and brassiere frames, and partly in medical supplies because of its shape memory effect. The smart composite can be used on the wing of an airplane instead of the existing aluminium to control crack propagation. In this study, the smart composite was fabricated by a hot press method. TiNi alloy as reinforcement and Al6061 as matrix were used, respectively. The mechanical properties of the smart composite under thermal shock cycles were evaluated. In addition, Acoustic Emission techniques were also used to clarify the
damage behavior of the smart composite under thermal shock cycles nondestructively.
Abstract: An evolutionary optimization process involving a genetic algorithm and combinatorial
chemistry (combi-chem) was tailored exclusively for the development of LED phosphors. The genetic algorithm assisted combi-chem (GACC) is a well-known, very efficient heuristic optimization method. Therefore the combination of a genetic algorithm and combi-chem would enhance the searching efficiency when applied to phosphor screening. The ultimate goal of our study was to develop oxide red and green phosphors, which are suitable for three-band white light emitting diodes (LED). In this regard, promising red and green phosphors for three-band white LED applications, such as Eu0.14Mg0.18Ca0.07Ba0.12B0.17Si0.32Od and Tb0.01Gd0.02Ce0.04B0.1Si0.83Od, were obtained.
Abstract: The present investigation aimed at visualizing the propagating crack in a
mechano-luminescence (ML) material, which enabled us to measure instantaneous R-curves and observe directly the bridging (shielding) stress in the fast-propagating crack system. The well-known ML compound, SrAl2O4:Eu,Dy,Nd, was adopted as a testing material. The crack initiation and growth from the mechanically machined sharp notch tip in the disc shaped compact tension (CT) specimen at a relatively fast loading rate were found to be associated with the extent of light emission around the crack. The in-situ measurement of crack length and applied load for 0.3 sec yielded an instantaneous R-curve at the conventional crack propagation speed.