New crack length measurement methods using thin metal film were proposed in order to evaluate the crack growth characteristics during static fatigue process of ceramics. Also, the effect of crack length on the crack growth characteristics was investigated using both soda-lime glass and glass ceramics specimens. As the results, it was found that in the soda-lime glass, there is no difference between small- and long-crack growth characteristics. On the other hand, in the glass ceramics, it was found that sub-critical crack growth (SCG) resistance in small-crack propagation test is higher than that in long-crack propagation test. In addition, it is confirmed that the glass ceramics has higher SCG resistance than that in the soda-lime glass. Furthermore, it was confirmed that the proposed crack length measurement method is suitable for crack growth characteristics evaluation on ceramics.

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The stress redistribution locus (SRL) method has been proposed to make a reasonable estimate of inelastic behavior under elevated temperatures employing both the elastic Finite Element (FE) analysis and a unique hyperbolic curve, where dimensionless equivalent strain and stress are normalized by elastic ones in the elastic FE analysis. In order to investigate applicability of the SRL method to components under the elastic-plastic state, low cycle fatigue tests were conducted employing a smooth specimen and four types of circumferentially notched bars. The number of cycles to crack initiation estimated by the SRL method was compared with the experiment. This showed that when an adequate elastic region remained inside the notch root, the crack initiation life could be well predicted by the SRL method. However when a ratio of the plastic area to the entire section of the notch root occupied over approximately 0.3%, an equivalent strain range on a surface of the notch root estimated by the SRL method became smaller than the one calculated by using the detailed inelastic FE analyses. On this occasion the crack initiation life estimated by the SRL method was overestimated.

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This article discusses the results of the mode I energy release rate of rectangular piezoelectric ceramic strips with two symmetric edge cracks under electromechanical loading. Cracks were created normal or parallel to the poling direction, and applied electric fields were parallel/antiparallel to the poling. A nonlinear plane strain finite element analysis was performed, and the effect of localized polarization switching on the energy release rate was discussed for the permeable, impermeable, open and discharging cracks under a high negative electric field. In the case under a high positive electric field, we examined the effect of dielectric breakdown on the energy release rate.

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The effect of carbon nanotube (CNT) size on the wear properties of Cu-based CNT composite electrode in electrical discharge machining (EDM) was studied. Cu-based CNT electrodes were fabricated by electroplating using a copper sulfate plating bath containing three kinds of CNTs. EDM was performed on stainless steel to evaluate the wear properties of the electrodes. Single pulse discharge was performed to evaluate the craters generated on the electrode surface. The wear ratios of Cu-based CNT composite electrodes decreased by 50-72% in relation to those of electrolytic Cu electrodes. The wear resistance of the composite electrodes was dependent on CNT size. It increased as the length and thickness of CNTs increased. The mechanisms of wear resistance in Cu-based CNT composite electrodes are discussed through observation and analysis of craters formed by single pulse discharge. The diameters of the craters are almost identical and largely independent of the size and presence of CNTs, indicating that CNT addition does not improve the thermal conductivities of the electrodes. Hence, the increase in wear resistance is independent of thermal conductivity. Exposed CNTs observed in craters on electrodes containing large CNTs with high wear-resistance properties do not decrease in diameter via electrical discharge, indicating that large CNTs can be resistant to pyrolysis at the melting points for Cu and Fe. It is suggested that the carbon layer with exposed CNTs on the electrode surface prevents the electrode from spark erosion in a manner identical to that of turbostratic carbon.

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This work deals with the electromagneto-mechanical behavior of self-sensing giant magnetostrictive/piezoelectric laminated composites under electric fields both numerically and experimentally. The cantilever laminated composite is fabricated using thin magnetostrictive Terfenol-D and piezoelectric PZT layers. The magnetostriction of the laminated composite is first measured. Next, a nonlinear finite element analysis is performed to evaluate the second-order magnetoelastic constants in Terfenol-D layer bonded to PZT layer, using measured data. The tip deflection, internal stresses and induced magnetic field for the giant magnetostrictive/piezoelectric laminated composites under electric fields are then discussed in detail. Experimental results on the tip deflection and magnetic induction change due to electric fields, which verify the model, are also presented.

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