Analysis of void closure in open-die forging

Void closure studies have been conducted numerically and experimentally for open-die forging processes. The plane-strain FEM analysis was compared with bite forging experiments in order to determine how well the plane-strain approximation predicted the material flow in open-die forging. In addition physical modeling with plasticine was used to compare the measured and calculated deformation of the internal defect. The FEM analysis was in good agreement with the experimental results. Correlations for the computed effective strain and hydrostatic stress to the void closure were then calculated. Simulations of a solid cylinder side pressed with flat dies, V-shaped dies, and FML dies were done to determine the effectiveness of these dies at consolidating internal porosity based on the calculated strain and hydrostatic stress at the center of the billet. The V-shaped dies were found to be the most effective among those investigated. However, the press load for the V-shaped dies was also the highest.     

Enhanced longterm stability of aluminum solid electrolyte capacitor containing thiophene derivatives as a solid electrolyte

The derivatives of thiophene, 3,4-ethylene-1-methyl-2-oxy-5-thio-thiophene (EMOTT) and 3,4-ethylene-1-propyl-2-oxy-5-thio-thiophene (EPOTT), are synthesized and then, 3,4-ethylenedioxythiophene (EDOT), EMOTT, and EPOTT are polymerized with ferric 4-methylbenzenesulfonate (oxidant) to obtain PEDOT-OMBs, PEMOTT-OMBs, and PEPOTT-OMBs, respectively. The surface conductivity of PEDOT-OMBs shows the highest value among the fabricated materials because PEDOT-OMBs shows the better defined crystalline structure and the doping concentration of PEDOT-OMBs is much higher than that of PEMOTT-OMBs and PEPOTT-OMBs. Capacitance and equivalent series resistance (ESR) of PEDOT-OMBs show the slightly enhanced value compared to PEMOTT-OMBs and PEPOTT-OMBs because of high electrical conductivity of PEDOT-OMBs. The PEDOT-OMBs shows the highest decrease rate of capacitance and increase rate of ESR because the extent of separation between the PEDOT-OMBs and the dielectric is much larger than that of PEMOTT-OMBs and PEPOTT-OMBs since it has the lowest density and hardness compared to other polymerized materials.     

Effect of homogeneous Al(OH)3 covered MWCNT addition on the thermal conductivity of Al2O3/epoxy-terminated poly(dimethylsiloxane) composites

Aluminum hydroxide covered multiwalled carbon nanotubes (A-MWCNTs) were synthesized as a conducting additive to alumina-epoxy-terminated poly(dimethylsiloxane). The measured diffusivity and calculated conductivity exhibited dissimilar behavior between several Al₂O₃ concentrations as a function of A-MWCNT loading, which correlated with the interface density and interconnectivity of the structures. The fabricated heterostructured A-MWCNT did not have a significant effect on the thermal conductivity of the composite because of phonon scattering at the interface. A small amount of A-MWCNT was feasible for establishment of a heat conductive percolating network with the greatest enhancement of thermal conductivity and diffusivity at an A-MWCNT loading of 1.0 and 2.0 wt%. Continuously increasing thermal transport properties were observed with the 49.1 vol.% Al₂O₃ loading which derived from a lower interface density nanowire and polymer matrix with enhanced interconnectivity.     

Better understanding of the filtration characteristics in the flexible fibre filter module (3FM).

This study is about the particle retention and filtration characteristics of fibre filter. Four laboratory scale fibre filters with different heights were used in parallel at various packing densities and filtration velocities. Of all of the operating parameters studied, filtration velocity had the most influence. Contrary to general theories, pressure drop increases slightly during the filtration in spite of the continuous retention of particles. This may have occurred because of large porosity of the packing (about 93%). This might be considered an advantage of the filter and something that makes it economic. The higher the filtration velocity, the larger the mass of particles retained in the filter. For filtration velocities of 20 and 40 m/h, particles smaller than 5 microm are retained as proven by the particle size distribution at the inlet and outlet.     

Surface wrinkle defect of carbon steel in the hot bar rolling process

It is well known that surface defect is a common problem encountered in the multi-stage hot bar rolling process of carbon steel. In this study, the phenomenon was investigated by simulating the process by the finite element technique to identify the location where the surface defect might occur and checking the surface qualities obtained from the compression tests at various temperatures and strain rates to clarify the important parameter governing the possible surface defect formation. Also, the surface temperature was measured by employing pyrometer to support the experimental observation. The levels of temperature and specific deformation energy obtained from finite element simulations depending on the roll groove geometry were compared with the experimental observation to better understand the formation of the surface defect in the hot rolled bar. Based on this study, the surface defect might be formed by dissipating the excessive deformation energy accumulated by generating the new surface at the lower level of temperature where recrystallization cannot occur. According to this work, the comparison of the specific deformation energy level for determining the instability of the hot working process might be interesting for further investigation.     

Characterization of the defect found in gold decoration layer of bone China

We investigated the microstructure of the gold decoration layer of bone china to pinpoint the cause of the gold cracking occurring in the process of high quality bone china manufacturing. Through the cross-sectional TEM (transmission electron microscope) analysis it has been observed that SnO₂ crystals from the matting agent that lies underneath the gold have undergone abnormal growth. As the few SnO₂ crystals under the gold grow excessively, the matting oxide bursts through the gold layer resulting in the gold cracking in the bone china tableware. It is also found that the defects in the glossy gold area cause more serious detriment to the quality of the gold layer than do those in the matt gold area. From this study, we conclude that the control of the size distribution of SnO₂ crystals is very important to keep high quality in the gold layer of bone china.