In this paper, we describe a pushing shear process carried out on a white-coated paperboard. The cutting load response of a 42° center bevel blade on the paperboard was measured by varying the mechanical conditions of a rubber fixture. An early-stage deformation of the paperboard was numerically analyzed with the orthotropic elastic model, and the stress distribution in the surface layer of the paperboard was discussed with respect to the rubber fixture effect. From the experiment and numerical simulation,the following results were obtained. (1) The load of inflection point f_C1 which corresponds to the surface layer breaking,decreases by 10-20% as a result of the mounting of a rubber fixture on a die set,while the load of peaked point f_C2,during the final breaking,increases by 0-10% as a result of the mounting of the rubber fixture,for a specified condition of rubber fixture mounting. (2) The maximum principle stress (tensile) markedly increases at the surface layer near the blade tip as a result of considering the rubber fixture,at the early stage of blade indention into the paperboard. (3) The maximum principle stress markedly decreases in the surface layer, which is in 2-4 times the paperboard thickness from the blade tip,at the early stage.

View full abstract

The main objectives of this study are to reveal the delamination characteristics of a paperboard during a pushed shear process by a crushed blade tip and to determine an easy method of estimating the delamination strength of the paperboard. Two types of paperboard, with different interbond strengths, were compared with respect to the results of the peel cohesion test of a wedged end-surface and the bending moment resistance of a creased line. The obtained results show that there is a positive correlation between the peel cohesion strength of the paperboard and the bending moment resistance of the creased line; a certain burr height on the crushed blade tip affects the peel cohesion strength on the wedged end-surface of the paperboard.

View full abstract

The elastopasticity behavior of a high-strength steel sheet was investigated by performing biaxial tension experiments. To evaluate the accuracy of constitutive models in describing such elastoplasticity behavior, numerical simulations of stress-strain responses were conducted for the same stress paths as those in the experiments using two types of models: the isotropic hardening model (IH model) and the kinematic hardening model proposed by the present authors (Yoshida-Uemori model). In this work, special emphasise is placed in the cases of stress-path change. In experiments on radial loadings after equibalanced tension preloading, it was found that flow stresses are considerably lower than uniaxial tension flow stress. The IH model hardly describes this phenomenon, although it is sufficient for stress-strain analysis of proportional loading cases. In contrast, the Yoshida-Uemori model can well predict every stress-strain response in biaxial stress-path changes.

View full abstract

In order to evaluate the relaxation and surface irregularity of the famous artist’s bowl and other analytical objects, an analytical procedure was developed by applying the concept of fractals, a hyperbola model of the Richardson effect, and FFT analysis. The main results of this study are summarized as follows: (1) To evaluate the irregular surface of relaxation quantitatively, an analytical system using a high-resolution laser sensor was developed, and an analytical-procedure-developed mesh method was established. (2) It was found that the famous artist’s bowl has a fractal nature and a relative self-similarity in wide resolution ranges. (3) The geometrical irregularity of the surface can be effectively evaluated by combining the fractal dimension D and the FFT parameters. (4) In order to apply the design of a mechanical structure in a later study, the target value of the fractal dimension was estimated as D=2.33.

View full abstract

In recent years, the fuel cells have attracted attention in relation to the environmental problems of the earth. And studies on the improvement of the productivity of the fuel cell are required. The separator in a fuel cell is important. The manufacture of separators usually involves injection molding or compression forming. However, in terms of productivity, the manufacture of separators by extrusion has advantages. Thus, the aim of this research is the development of a new method of extrusion of a fuel cell separator using an orthogonal channel. The manufacture of separators by this new extrusion method was successful. Moreover, it is important to determine the most suitable speed condition for stable extrusion.

View full abstract

To understand the behavior of oil in water (O/W) emulsion in the inlet zone of cold rolling under starved condition, Al-1050H-24 sheets were rolled with neat oil and O/W emulsion, while changing lubrication conditions. The thickness of the inlet oil film between the roll and the workpiece was measured, while changing base oil viscosity, particle size, O/W emulsion concentration and the type of emulsifier using the relationship between the calculated inlet oil film thickness with neat oil and the surface brightness of the sheet rolled with O/W emulsion. Trapping ratio was estimated from the measured inlet oil film thickness using the calculated system for inlet oil film thickness in O/W emulsion. It was found that the trapping ratio decreases with increasing droplet size and O/W emulsion concentration, so that inlet oil film thickness depends slightly on particle size and O/W emulsion concentration. On the other hand the effect of the type of emulsifier on trapping ratio was found to be significant, enabling us to increase inlet oil film thickness by selecting appropriate emulsifiers.

View full abstract

Various mechanical properties of magnesium alloys have been reported by many researchers. Some researchers have studied the plastic buckling behaviors of magnesium alloys, but the effect of shot peening on plastic buckling strength of magnesium alloys has not been researched yet. In this paper, we describe the effect of shot peening on the plastic buckling behavior of a cylindrical pipe of AZ31(Mg-3%Al-1%Zn) magnesium alloy subjected to axial compressive load. The pipe was exposed to three types of shot peening, and a buckling test on the magnesium alloy pipe with a 38 mm outer diameter, a 35.6 mm inner diameter and a 100 mm gauge height was carried out with both ends of the pipe fixed. The main experimental results are summarized as follows: the buckling stress of the pipe exposed to shot peening is higher than that of the as-received one at 293 K, and is almost the same as that of the as-received one at 573 K.

View full abstract

A cold 2-stages stamping process for forming magnesium alloy cups having a small corner radius from commercial magnesium alloy sheets was developed. In the 1st stage, a cup having large corner radius was formed by deep drawing using a punch having large corner radius, and the corner radius of the cup was decreased by compressing the side wall in the 2nd stage. In the deep drawing of the 1st stage, fracture was prevented by decreasing the concentration of deformation with the punch having large corner radius. The magnesium alloy sheets were annealed at 500°C to increase the cold formability. Circular and square cups having small corner radii were formed by the cold 2-stages stamping. For the circular cup, the height of the cup was increased by ironing the side wall in the 1st stage. The radii of the bottom and side corners of the square cup were reduced by a rubber punch for applying pressure at these corners in the 2nd stage. It was found that comparatively shallow magnesium alloy square cups used as cases of laptop computers and mobile phones can be satisfactorily formed at room temperature without heating by the 2-stages stamping.

View full abstract