In this study, in order to determine the carbonation process relationship between cement hydrates and calcium carbonate polymorph, Raman spectroscopy was applied to measure the carbonation process of ordinary Portland cement and Alite cement paste at different relative humidity. As a result, carbonation of both cement paste was most progressed in the wet environment, while almost no carbonation progress in the dry and 60%RH condition. Calcite and vaterite were the main precipitates in the carbonation of ordinary Portland cement, while calcite was the main precipitate in the carbonation of Alite. The correlation coefficient between cement hydrates and calcium carbonate, and the carbonation rate of cement hydrates were obtained by Raman mapping data.

Rock drills have been widely used for blast hole drilling in tunnel construction and ore extraction. For the advancement of performance and efficiency of rock drills, it is essential to understand the penetration behavior of a button bit and each of the button tips into rock. In this study, static penetration tests were conducted with three rocks using each of button tips with six diameters. The test results showed that the force-penetration curves are linear in the loading phase and convex downward in the unloading phase for sandstone and andesite and that the curves are convex downward in both the loading and unloading phases for granite, if rock chipping does not occur. The force-penetration curves in the loading phase and deformation mechanisms of the rocks could be explained with the contact mechanics; plastic deformation is dominant for sandstone and andesite, and in contrast elastic deformation is dominant for granite. In addition, the relations of the diameter of a button tip, the Young’s modulus and yield stress of rock to the force-penetration curves were clarified. These results indicate that force-penetration curves are estimated beforehand from mechanical properties of the target rock. Occurrence of rock chipping was found to be influenced by not only the diameter of a button tip but also the heterogeneity of rock texture.

Fractographic analysis of fracture surfaces helps to improve the performance of mechanical pieces. In order to determine the causes that generated the fracture, it is necessary to classify a fracture into a failure mode. Experts in fractographic classification use visual evidence of textures and surface marks to determine the failure classification. The fractographic images for this task are obtained using a Scanning Election Microscope (SEM). With new advances in machine learning and artificial intelligence, specifically with deep learning and Convolution Neural Networks (CNN) becoming accessible, it is becoming possible to automate fractographic classification. This study aimed to improve the accuracy of fractographic classification using CNN by considering the material types. We proposed a Stepwise Selection of Source Classes (SSSC) to perform transfer learning considering the material types. The proposed method was applied to classifying fractographic SEM images into seven groups of fracture surfaces in alloy steels, austenitic stainless steels, and copper and copper alloys. The existing method, which does not distinguish the material types, achieved an average accuracy of 92.4%, while the proposed method improved the average accuracy to 98.7%.

Among variety of 3D printing or additive manufacturing methods, the laser power bed fusion (LPBF) technology for metals is now widely spread. In this study, the geometrical accuracy of 3D printed circular hole in a flat plate was investigated using aluminum alloy, Al-Si10-Mg, and polyamide, PA12. Some types of geometrical imperfections have been reported, for instance, in lattice structures or for overhang structures, but the distortion of a circular hole in a component made by LPBF has not yet been discussed in detail. This paper revealed the correlation between the geometrical parameters for distorted circular hole and the building angle. This enabled us to predict the distortion for unexperienced building angle by the interpolation, and to perform finite element analysis of mechanical behavior of a component with a circular hole. The influence of the geometrical inaccuracy on the mechanical behavior and that of the variability in mechanical properties were compared, and the former was found to be more influential. Finally, the geometry compensation in the design phase was also discussed using the statistically measured database.

High density polyethylene (HDPE) / ultra high molecular weight polyethylene (UHMWPE) blend is expected as an all-polyolefin recycle material that can achieve both mechanical properties and a continuous melt-mixing process. In order to improve the mechanical properties of polymer blends, optimal mixing is required to achieve both good dispersibility and low degradation. In this study, the effect of mixing conditions on the dispersion and degradation behavior of HDPE/UHMWPE blends were investigated. Neat HDPE and HDPE with 5% UHMWPE were obtained by melt mixing in internal batch mixer. Time of mixing, Specific Energy Input (SEI), and rotation speed of the rotors were changed. From the results of microscopic observation and a differential scanning calorimetry (DSC), the dispersibility progressed with the increase in SEI regardless of the rotor speed. The results of Gel Permeation Chromatography (GPC) show the molecular chain scission was also promoted by the increase in SEI. In the other hands, the results of oscillatory shear test show the increase in storage modulus G’ were promoted by increase in not only SEI but rotor speed. Furthermore, the molecular chain scission and increase in G’ were significantly suppressed by the nitrogen atmosphere.

In a hot steel rolling process, the rolling force and the strain distribution in a rolled material is strongly affected by the friction coefficient between the work roll and the rolled material and the rolling shape factor which is the ratio of the contact length between the work roll and the material to the material thickness. In this respect, many numerical attempts have been made to reveal their relationship. These simulations often suppose the homogeneity of the material because of simplicity. However, the recent researchers have suggested that the heterogeneity in microstructure can cause size effect on deformation behavior of polycrystalline material. In order to clarify the size effect in the rolling process, this study investigates the size effect on the deformation force and the strain distribution in the plane strain compression which is simple and similar to the flat rolling in effects of the friction coefficient and the shape factor, using the second-order homogenization-based finite element (2nd HMFE) simulations. Simulations are performed by two-dimensional 2nd HMFE with different friction coefficients, shape factors, work hardening parameters and size ratios between micro and macrostructures, which are related to strain heterogeneity in a deformed material. As a result, in case of the small friction coefficient, relatively uniform deformation tends to occur in the material, which results in small effects of the size ratio on deformation behavior. In contrast, in case of the large friction coefficient, size effects on the compression force and the strain distribution appears to be large when the shape factor of a deformed material approaches 1. It is considered to be because high strain gradient tends to reduce the plastic work in the microstructure and a deformation band in which the strain gradient is higher is formed in the material in such a case.