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In this study, the fundamental burnishing characteristics and quality of a molded product were evaluated during the sliding burnishing process with an active rotary tool developed by the authors was applied to the on-machine surface finishing of an aluminum mold for resin injection molding. The burnishing characteristics were mainly evaluated based on the surface profile, roughness, glossiness, material composition, and residual stress. The burnishing force increased with the indentation depth of the tool, and a constant fluctuation occurred according to the tool rotation cycle. Good burnished surface roughness and glossiness were achieved when the burnishing tool was fed at the same height as the cusp recesses on the preliminary surface. High compressive residual stress existed on the subsurface during the burnishing process, compared to the machined surface and polished surface, and the compressive residual stress increased with the indentation depth of the burnishing tool. The feed direction of the burnishing tool had a significant effect on the burnished surface quality, and the quality improved when the sliding directions of the tool rotation and tool feed were the same. The mold piece obtained from the burnishing process had almost same surface roughness as that obtained from the polishing process. The molded product quality obtained for these molds was similar to the mold surface quality, and the molded product obtained from the mold fabricated through the burnishing process had the same quality with that obtained through the polishing process. Based on these results, on-machine surface finishing of the injection mold was achieved using a general machine tool through position control by applying sliding burnishing with an active rotary tool.

Sulfurnitriding, one of various surface treatments for mechanical components made of steels realizes solid lubrication for decreasing friction force of each contact point and keeping lubricating condition on the surface. Any tribological data on sulfurnitrided steel gears have not been published. In this study, friction performance of sulfurnitrided gears made of low-carbon steels (JIS-S45C) was investigated. Wear tests of the gears were conducted at room temperature without any lubrication. The gears with different treatments such as non-treated, as-nitrided, as-carbonized, as-quenched and as-induction-hardened ones were applied to the same low-carbon steel for comparison. The amount of wear of the gears was decreased by applying the all surface treatments. The gears with the sulfurnitridation show smaller wear than others while the surface hardness of the gears was comparable or lower than the others. In particular, the surface treatment combining of sulfurnitridation and nitridation showed the lowest value of the amount of wear. The FeS layer formed by the sulfurnitriding is approximately 1 μm in thickness which is much lower than the amount of wear after 4 h in test time. Lubrication effects on the FeS layer remains after removing the layer. As well, nitridation after sulfurnitriding is effective to improve a solid lubrication performance for low-carbon gears at room temperature in air.

A novel total hydrocarbon (THC) emission concentration estimation model is proposed for reduction of engine development cost as well as simplification of measurement system. The model is based on machine learning algorithm including the least absolute shrinkage and selection operator (LASSO) regression and bagging techniques. Major features of the proposal model are taking the absorbance spectrum of Fourier transform infrared (FTIR) spectrometer as input and incorporating not only spectra of the engine exhaust gas but also those of individual hydrocarbon and inorganic gas components as training data set. This method was validated on the exhaust gas before the catalyst of a gasoline engine. The results show an error of less than 5% in both steady and transient operating conditions, outperforming the 20 % error of conventional regression model using only the reference hydrocarbon concentrations. We also evaluate the contribution to performance improvements in THC estimation of employing FTIR spectrum and incorporating spectrum information of gas components, respectively.

A variety of health assessment technologies for mechanical systems utilizing time-series sensor data has been developed and are recently being applied to the maintenance work as a solution to the predictive maintenance. A majority of these technologies are the condition-based way which premises the existence of condition monitoring sensors such as accelerometers for the vibration monitoring of rotating mechanical elements. In the present study, authors suggested a load history-based methodology for identifying a descriptive and stochastic model of the useful life of mechanical systems to realize the predictive maintenance under constraints of sensing conditions. The methodology (Damage-based survival analysis, DbSA) was based on a parametric survival analysis by the maximum likelihood estimation assuming the Weibull distribution of the useful life. A random variable of the probability distribution was converted from the elapsed time to cumulative value of a function of time-series sensor data and parameters of this function were optimized to minimize the dispersion of the probability distribution by the particle swarm optimization. DbSA was applied to a historical record of a clogging problem in a strainer in a chemical plant and its time-series process data to demonstrate the usefulness. An identified damage-based lifetime model exhibited less than 50% smaller dispersion (coefficient of variance) compared to the timed-based probability distribution. In addition, an identified function composed of the process data implied an effect of the impurity generation to the clogging problem. If the identified model was applied to a dataset which was not used to the model identification, it was indicated that 3 of 8 cloggings were occurred when the damage-based failure probability was more than 50% although the time-based probability did not reach to this level at any time.

A topology optimization method is proposed for the design of shallow-flow channels based on quasi-three-dimensional flow models of laminar and turbulent flows. The models for laminar flow and turbulent flow are derived from the Navier-Stokes equations and the Reynolds-Averaged Navier-Stokes (RANS) equations, respectively, by integrating along the direction of channel thickness. The thickness is employed as the design variable in the topology optimization. The design variables are updated using a time-dependent diffusion equation with a design sensitivity which is calculated by a discrete adjoint approach. Numerical examples for minimizing dissipation energy or variance of flow velocity magnitude using the topology optimization demonstrates that the proposed method is capable of finding optimal solutions that satisfy the KKT conditions. In the former example, the design domain was clearly divided into domains where the thickness was either near the upper limit or near the lower limit. However, in the latter example, the thickness was at an intermediate level in almost the whole the design domain. The distribution of the thickness varied depending on the Reynolds number in both examples.

This paper presents experimental, analytical and numerical study of impact perforation of steel plates with the aim to develop the procedures to assess the perforation of steel against tornado-generated missile impact. In the experiment, flat plates of SS400 steel and SUS304 stainless steel were perforated by a square pipe with cross section 200 x 300. Projectile mass and impact velocity were kept constant, namely, approximately 1300 kg and 17 m/s. Perforation limit thickness of SS400 and SUS304 flat plate was determined to be 9 mm and 6 mm, respectively. BRL formula was used for the analytical study, and equivalent diameter of square pipe for BRL formula was defined based on the experimental data. Numerical simulations of some experiments were also carried out and the effect of thermal softening and stress triaxiality on failure strain have to be taken into account in the material model in order to reproduce the experimental results.

Scallop pattern is widely recognized as a typical morphology on the corroded surface by high flow-accelerated corrosion (FAC) rate in single-phase flow. Although turbulence flow condition could be closely related to scalloped appearance, the detailed process of scallop development is not fully known. In this study, detailed characterization of scalloped appearance (scallop size, depth, and density) and oxide layer (nano-void structure, thickness, and compositional profile) on the inner surface of the carbon steel piping elbow used in a fossil power plant have been carried out. The extrados of the piping elbow showed maximum FAC rate (approximately 0.25 mm/year). On the other hand, the intrados of that showed no FAC. The FAC rate lineally decreased from the center of extrados to intrados side, while the scallop patterns were observed in a limited region on the extrados. Approximately half of the maximum FAC rate was shown even on the smooth surface. It has been notable that there was no significant increase of the FAC rate by scallop formation although the local turbulence was increased by hydrodynamic effect due to scallop surface. The relationship among scallop size, depth, and density obtained in this study indicated that the occurrence of overlapping horse-shoe shaped pits that give a scalloped appearance. The surface morphologies under FAC condition is considered to essentially depend on the nucleation density of pits. Nanometer-scaled thin porous oxide layer was formed on both extrados and intrados, and there was no significant difference in nano-void structure, thickness, and crystalline structure obtained by transmission electron microscope characterizations despite a significant difference in the FAC rate. Since no Cr enrichment was observed in the oxide layers formed on the both sides, FAC suppression by Cr content of carbon steels could be negligible in this condition.

A direct numerical simulation of compressible turbulent channel flow at low Mach number(Ma = 0.3) subject to strong temperature gradient is conducted. The wall temperature ratios which are defined by a temperature on the upper wall divided by that on the lower one, are set to 2 and 3. It is shown that the flow of high temperature wall side is laminarized as increasing the wall temperature ratio. Moreover, compressible and dilatational motions are induced on the low and high temperature wall sides, respectively. The identity of friction coefficient originally derived by Fukagata et al.(2002) (so-called ‘FIK identity’) is extended to those of friction coefficient and Nusselt number on the compressible channel flow. It is revealed that the viscous variation component attains to 16 % of the friction coefficient on the case of high temperature ratio. Furthermore, the pressure work component occupies about 20 % of the overall Nusselt number for the all cases. The pressure work has a redistributive effect between mean kinetic energy and internal energy. The energy transfer from mean kinetic energy to internal energy appears on the low temperature side whereas that toward the opposite direction on the high temperature side at the present low Mach number flow.

A computer simulation method to predict the thermal distortion value of a high-pressure die cast part was investigated. The evaluated product was a flat-shape JIS ADC12 part. The actual distortion value of the part was measured by an optical 3D digitizer and it was compared with the predicted distortion value. In this method, the initial temperature distribution of the part was determined by casting simulation. The thermal distortion value during cooling was calculated by FEM analysis. The stress-strain relation was approximated by the elastic-perfectly plastic material model including the temperature dependence of the yield strength. It was found that the heat-transfer coefficient between the die and the injected molten metal is a critical factor to implement an accurate FEM simulation in the casting simulation. The heat-transfer coefficient value was accessed and confirmed using the temperature distribution measured by a thermo camera. The distortion values of the actual part optically measured as a function of the curing time well coincided with the simulated value. It was concluded that the method can predict the distortion within a practically accepted preciseness.