Open-cell porous aluminum (Al) was fabricated by spark plasma sintering process. In this process, a mixture of pure Al powder, 6061 aluminum alloy powder and sodium chloride (NaCl) powder as spacer particle was used as starting materials. The powder mixture was sintered by spark plasma sintering process. NaCl was removed by placing the sintered mixture in water, and pores were formed. In this study, pore structures of obtained porous Al were nondestructively observed by X-ray computing tomography (CT). It was shown that strength of porous Al was improved by 6061 aluminum alloy powder addition.

In this study, precursor of Al-Si-Cu aluminum alloy ADC12 porous aluminum was foamed only by friction heat of friction stir welding (FSW). The precursor of the ADC12 porous aluminum was also fabricated from die casting aluminum plates by FSW. It was shown that precursor of ADC12 porous aluminum can be foamed using only the heat generated by the friction between the rotating tool and the copper plate.

Porous aluminum (Al) has lightweight and high energy absorption properties. Sandwich panel consisting of A6061-ADC12 functionally graded porous Al and A1050 Al plates was fabricated by friction stir processing (FSP). It is expected to be used as structural materials. In this study, bending test of sandwich panel was carried out. It was shown that deflection is larger than the uniform ADC12 porous aluminum sandwich panel.

This study investigated the compressive deformation behavior of hollow-strut cellular materials. The present cellular structure consists of pentagon and/or hexagonal shaped cellular network, where the individual strut cross-section is hollow triangular prism. Uni-axial compressive test is applied to the present material and we investigate macroscopic deformation behavior as well as the changes in microstructure with respected to the applied strain. The macroscopic nominal stress-strain curve showed a linear relationship during elastic deformation, and then a stress plateau region was observed, followed by the gradual increase in plastic flow stress. Next, by using X-ray micro-CT technique, the strut geometry was quantitatively identified, and based on which finite element method (FEM) was carried out to elucidate the relationship between the strut geometry and the microscopic/macroscopic elastoplastic deformation. A three dimensional spatial structure unit model was established to mimic the present open-cell structure, where the employed strut material properties were obtained from micro-indentation experiments. The FEM computational result agrees reasonably with experimental one of the macroscopic Young's modulus and yield stress. It also suggests that the stress concentration occurs in the minimum cross-section of strut, and then plastic deformation starts at this local point. Such a local yield phenomenon becomes a trigger of buckling for strut, leading to macroscopic plastic deformation characteristics.

Honeycomb sandwich structures are increasing being used to replace traditional materials in high strength and light weight applications. In the present work, the honeycomb sandwich specimens were manufactured by a new manufacturing method (i.e. a press and folding process). Two cases were studied one with the specimen bonded by using common adhesive and the other with the specimen bonded by aluminum claws. The three-point bending properties of the manufactured aluminum structure were investigated to evaluate the bending rigidity of the honeycomb sandwich structures. In addition, finite element analysis (FEA) was carried out by ANSYS 17.0 to evaluate the bending properties of the designed sandwich structure. A comparison of the results was made and a good agreement was evident.

On cold spray (CS) technology, low temperature gas is adopted witch is maintained below melting point of source materials. Cold spray has been applied for fabrication of composite films since the method is possible to prepare rather thick composite films containing various additives. In this research, thick polyethylene-based composite films are deposited on three types of substrates/ aluminum, polypropylene and nano-porous structured aluminum were used as substrate. In the case of preparation of polyethylene/carbon nanotube-composite films on polypropylene and nanoporous structured aluminum substrate, we succeeded to deposit thick film with hundreds μm in thickness and the film was sufficient adhesion with the substrate. This film has electric conductivity owing to carbon nanotubes incorporated in the polymer film.

In the present study, a uniaxial tension test was carried out using a pre-compressed magnesium alloy sheet to examine the effect of residual stress and twinning on the work-hardening behavior during tension following compression. The yield stress under tension was much smaller than the stress before the stress reversal, exhibiting strong Bauschinger effect. In contrast, when the sheet was annealed before tension, the yield stress increased much higher than that of the non-annealed sheet. This result indicated that the residual stress in the pre-compressed sheet significantly affected the yield stress under tension. A crystal plasticity finite-element method was used to verify the presumption. In the simulation, the annealing process was approximated by removing residual stresses. The stress-strain curves in non-annealed and annealed sheets obtained from the simulation were in good agreement with those of the experiment, which confirmed the presumption.

A development of the moveble flap gate type breakwater, which is based on a steel flap gate in hydraulic gates with a number of adoption results, is reaching the final stage of demonstration tests in the sea. The flap gate type breakwater usually lies down on a seabed and rises up through a sea surface with buoyancy when tsunami or storm surge occurs. In past studies reflected viewpoints of a large number of specialists, it has been confirmed that the flap gate type breakwater has capabilities against tsunamis. This paper describes the characteristics of the flap gate type breakwater, the expansion of utilizations in seawalls except breakwaters for tsunami and storm surge reduction.

To measure the deformation of the structural material, the Moiré method has been used for the full-field deformation measurements. However, in this method, two (master and model) grids or gratings should be overlapped on the specimen. To avoid this problem, a Moiré method using digital camera has been applied. The model grid was fabricated on the structural material, and shooting by a digital camera. Using an image processing system, the Moiré fringe can be observed. Using this method, the deformation of the structural material such as strain distribution, displacement, and vibration of the structural material can be measured. The damage of the structural material can be estimated.