Papers by Author: Akira Shimamoto

Abstract: Plastic film assumes a large role as packaging material in our life. Especially, by lamination which is pasting some kind of simple substances together, plastic films are able to have many kind of function on demand of usage. It is considered that enough high peel strength and tensile strength are needed for liquid package material. And it is considered that low tearing strength is needed for easy open package too. Adhesive existing at interlayer of laminated film, and the amount of adhesive may have effect on these physical properties. In this study, we changed amount of adhesive about laminated film, measured peel strength, tensile strength and tearing strength. And we investigated best suited amount of interlayer adhesive.

Abstract: Intelligent materials have been studied in various fields. In this study, Shape Memory Composite (SMC) is produced as one of those intelligent materials. SMC consists of Shape Memory Polymer (SMP) and Shape Memory Alloy (SMA). These two materials possess different characteristics in temperature changes. Therefore, we investigated the possibility of the SMC’s actuator function as an intelligent material. The actuator function is achieved by applying a current to SMA fiber of SMC to grab and release objects. As a result of this investigation, meaningful data for actuator to design SMC is obtained.

Abstract: In order to enhance grinding efficiency of the magnetic abrasive finishing (MAF) method, we usually use the sinter method or the cementation method to mix the magnetic particles and abrasive particles together. However, the cost is high, and the variety is incomplete. Therefore, with the ferromagnetism to iron particles, the alumina particles and the lipin three kind of material simple mixture participate in the magnetic abrasive finishing which directly polishes, already obtained the good effect through the experiment. This paper analyses and explains the characteristic of the friction coefficient and the friction force on magnetic abrasive finishing according as account and experiment data.

Abstract: In this study, the photoelastic experiment hybrid method was introduced and applied to the fracture problems of the isotropic polycarbonate plate with a central crack under the uniaxial and equibiaxial tensile load. The influences of equibiaxial tensile load on the isochromatic fringes and stress fields, stress intensity factors near the mixed mode crack-tip were investigated. As the results, without relation to the inclined angle of crack, the asymmetric isochromatic fringes around the crack propagation line under uniaxial tensile load has become symmetric and the slope of isochromatic fringe loop has inclined toward crack surface when an equal lateral tensile load was added. Furthermore, the distribution of all stress components have changed from asymmetric shape to symmetric shape, and only the range of compressive stress of σχ/σ0 have changed as compared with the mode I condition under unaxial load with β = 0°. When an equal lateral tensile load was added to uniaxial load, the value of stress intensity factors are little changed when β = 0° but the values of KI /K0 are increased and KII /K0 are become zero, that is, mode I situation when β = 15°~45°.

Abstract: The shapes and types of containers for foods, drugs and medicines, and cosmetics and detergent refills are diverse: glass bottles, cans, PET bottles and laminate-film liquid packaging bags are examples. In recent years, to increase the ease of pouring out the contents of laminate-film liquid packaging bags, the shape of the heat seal has been changed from a flat seal to a bottleneck seal. However, the large number of bottleneck seal ruptures of liquid packaging bags due to impact load during the transport, loading and unloading of packaged products has been a problem. In our previous study, we investigated impact peel strength in the heat-sealed area of a laminate film; however, the effects of the bottleneck seal shape and heat-sealed area width on impact peel strength and rupture occurrence have not yet been clarified. In this study, experiments were carried out to clarify the effects of the flat and bottleneck seal shapes, as well as heat-sealed area width, on impact peel strength and bag rupture occurrence. The following two films were used : (1) a multilayered laminate film with barrier characteristics against oxygen and water vapor, which is frequently used for liquid packaging bags owing to its high efficacy in food quality preservation, and (2) a multilayered laminate film without barrier characteristics. On the basis of the results obtained, we established, for the first time, a new standard regarding bottleneck seal shape and heat-sealed area width.

Abstract: In this study, stress intensity factors were investigated and determined by photoelastic and caustics methods to clarify the mechanical behavior of crack tips under various biaxiality ratios. Polycarbonate (PC) plates with isotropic and anisotropic properties were used as specimens. The results confirmed that regardless of biaxiality ratio or the material’s property only ‘KI’ was generated in cases of a crack angle θ = 0º. It was also confirmed that only KI was generated in the isotropic PC plate with crack angle θ = 45º under a biaxial load (1:1). When the biaxiality ratio is more than 1:1 with a crack angle θ = 45º, both KI and KII are simultaneously generated in the isotropic specimen. Furthermore, KI, and KII values are influenced most by the extrusion direction in the anisotropic specimens as the biaxiality load ratios increase.

Abstract: Magnesium alloy is the lightest metal that is used as a structural material. It has a higher specific tensile strength and specific stiffness than Iron and Aluminum alloy, and the dent is not caused easily from Iron and Aluminum alloy at the impact. Therefore, Magnesium alloy is widely used in many areas, especially as an external shell of a mobile device and automotive parts which replaces iron and plastic, etc., and its demand is expected to grow in the future. In this paper we studied the hypervelocity impact with a ballistic range to clarify the characteristic of Magnesium alloys which had such a characteristic. The effect of impact velocity, temperature and the size of perforation hole were investigated experimentally. The perforation resistance of Magnesium alloys and their impact behavior were characterized.

Abstract: The dynamic fracture experiments were conducted on the heat treated magnesium alloys; AZ31B-O, AZ31B-200 °C, and AZ31B-430 °C. Cross shaped specimens with the crack on their center were used for the experiments. Dynamic fracture behavior near a crack tip under equal and unequal biaxial stress was observed by the caustics method. From the observation, the stress intensity factor and the fracture toughness value were calculated. As a result, the effect of heat treatment was found. However, no clear relation such as correlation between dynamic stress intensity factor and heat treatment temperature was deduced.

Abstract: Assisted living instruments and medical implants, such as wheelchairs and joint prostheses are usually subjected to biaxial or three-axial stresses instead of uniaxial stress. So, authors already developed a servo biaxial fatigue-testing machine, and clarified about the performance evaluation. Moreover, closed-packed hexagonal lattice metal, such as magnesium and titanium, is frequently used for assisted living instruments or medical implants. In this research, fatigue crack propagation tests of magnesium alloy AZ31B and pure titanium TP340C were conducted under conditions of biaxial and uniaxial loading by using a cruciform specimen in a bi-axial fatigue machine, in order to investigate the effect of non-singular stress cycling on the fatigue crack growth properties ⊿K-da/dN. From these comprehensive experiments, in the magnesium alloy, the re-markable effect was found in the specific biaxial load stress ratio on ⊿K-da/dN relation. When biaxial load stress ratio was 0.5, it turned out that the fatigue crack propagation rate of a magnesium alloy becomes very slow. On the other hand, in the titanium, it was confirmed that there is a little influence of a biaxial load stress ratio on ⊿KⅠ -da/dN relation.

Abstract: Static and dynamic loading fracture experiments were conducted on magnesium alloy under equal and unequal biaxial stress. Cross shape specimens with a crack on their center were used for tests. Fracture behavior was observed by two methods; the caustic and the one point gauge method. From the observation, the stress intensity factors and the fracture toughness values were calculated. It was found that the one point gauge method was not suitable for calculating the stress intensity factor with a strain gauge widely available. The fracture toughness values obtained under equal biaxial stress were 1.2~2.3 times greater than those of magnesium alloy naturally inherited. Moreover, plate thickness was negatively related to the fracture toughness value.