Papers by Author: Hirotsugu Inoue

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Authors: Insu Jeon, Masaki Omiya, Hirotsugu Inoue, Kikuo Kishimoto, Tadashi Asahina
Abstract: A new specimen is proposed to measure the interfacial toughness between the Al-0.5%Cu thin film and the Si substrate. The plain and general micro-fabrication processes are sufficient to fabricate the specimen. With the help of the finite element method and the concepts of the linear elastic fracture mechanics, the detailed structure for this specimen is modeled and evaluated. The results obtained from this research show that the proposed specimen provides efficient and convenient method to measure the interfacial toughness between the Al-Cu thin film and the Si substrate.
Authors: M. Nizar Machmud, Masaki Omiya, Hirotsugu Inoue, Kikuo Kishimoto
Abstract: Based on previous available constitutive models, a phenomenological constitutive model has been constructed and is proposed to describe the strain, strain rate and temperature dependentdeformation behavior of PC/ABS blends. In this paper, four quasi-static uniaxial tension tests of a specimen tested at different strain rates and temperatures were used to identify the constitutive model constants. By using the proposed constitutive model, predicting the stress-strain behavior of the PC/ABS blend tested at certain strain rate and different temperatures compares well to the behavior exhibited from the tests. From comparison between the DSGZ and the proposed models, proposed model shows a better prediction. Evaluation of the proposed constitutive model was also presented and it has revealed that the proposed model might have a potential to be used for predicting a wide range of temperatures and high strain rates behavior of PC/ABS blends.
Authors: Akira Shinozaki, Kikuo Kishimoto, Hirotsugu Inoue
Abstract: The mechanical properties of polymers are strongly influenced by meso-scale (10-9-10-3 m) structure such as entanglement, molecular weight distribution, orientation, etc. It is well known that sunlight induces the UV degradation of polymers. The mechanical properties of polymer are strongly influenced by UV irradiation because of chemical change of meso-scale structure. However the detail relationship between the mechanical properties and chemical change of meso-scale structure is not clear. In this study, it is aimed to clear this relationship by the simulation. Network models considered the meso-scale structure are constructed. Degradation is described to delete the chain elements in the network model. Large strain deformation of these network models is evolved via molecular dynamics analysis improved by us. It is possible to describe the degradation by this method.
Authors: M.F. Adziman, S. Deshpande, Masaki Omiya, Hirotsugu Inoue, Kikuo Kishimoto
Abstract: The stochastic nature of aluminum foam structure, having a random distribution of voids, makes it difficult to model its compressive deformation behavior accurately. In this paper, a 2-dimensional simplified modeling approach is introduced to analyze the compressive deformation behavior that occurs in Alporas aluminum foam (Al foam). This has been achieved using image analysis on real undeformed aluminum foam images obtained by VHX-100 digital microscope. Finite element mesh for the cross sectional model is generated with Object Oriented Finite element (OOF) method combined with ABAQUS structural analysis. It is expected that OOF modeling enable prediction of the origin of failure in terms of localized deformation with respect to the microstructural details. Furthermore, strain concentration sites leading to the evolution of the deformation band can be visualized. Thus, this investigation addresses the local inhomogeneity in the Al foam structure. This study implies that the OOF modeling approach combined with experimental observations can provide better insight into the understanding of aluminum foam compressive deformation behavior.
Authors: Hirotsugu Inoue, Tokuro Nanba, H. Hagihara, T. Kanazawa, Itaru Yasui
Authors: M. Nizar Machmud, Masaki Omiya, Hirotsugu Inoue, Kikuo Kishimoto
Abstract: An instrumented-drop weight impact test carried out at room temperature under a range of loading rates was applied to study the deformation and failure behaviors of PC/ABS (50/50) blends. Actually, these blends have different type of ABS, one grade of the blends is the blend containing small-sized particles of rubber and another grade is the blend containing larger-sized particles of rubber in the ABS systems. Testing results showed that both of the blends generally exhibited similar behaviors but they were totally different under 3 m/sec. A weld line-like formation captured on the fracture surface was found in each of the blends. Preliminary study using scanning electron microscope (SEM) indicated that crack also propagated along the weld line. Fracture of the blends might be initially induced due to fracture of the weld lines. Hence, it has been suspected as a factor affecting behavior of the blends. Since existence of the weld line-like formation has not been found in fractured ABS materials, it is necessary to point out the complex relationship among of the ABS composition, the existence of the weld line and the weld line quality in the blends. A finite element (FE) simulation of the testing was carried in order to determine whether the weld line strength is significant enough affects the behaviors. Although the model was generated using estimated failure criterion for the weld line, the simulation results showed that weld line strength might influence the blends behavior.
Authors: Tokuro Nanba, Hirotsugu Inoue, Yoshikazu Arai, Hisashi Hasegawa, Masaki Misawa, Itaru Yasui
Authors: Ryota Masuda, Masaki Omiya, Hirotsugu Inoue, Kikuo Kishimoto
Abstract: Adhesives are widely used in industrial world. However, it is difficult to characterize their mechanical properties because those strongly depend on environmental and mechanical conditions such as temperature, humidity or strain rate. In this paper, we focus on the strain rate dependence of the interfacial strength and investigate the interfacial strength by peel tests under several peel rates. The results show that, in low rate case (under 10-2 mm/s), the interfacial strength was constant and, in middle rate case (10-2 to 103 mm/s), the interfacial strength increased with the peel rate. Over 103 mm/s case, the interfacial strength became lower than those in middle rate cases. From the observation of peeling front by a high speed video camera, the deformation behavior of adhesives changed with the peel rate.
Authors: M. Nizar Machmud, Masaki Omiya, Hirotsugu Inoue, Kikuo Kishimoto
Abstract: Experimental works using a drop weight impact test method have been performed on a circular sheet specimen to evaluate and to characterize the impact resistance of the sheet-type plastic components designed for automotive wheel covers. Evaluation has been conducted for a set of engineering plastics: polycarbonate (PC), acrylonitrile-butadiene-styrene (ABS) and their blend (PC/ABS). The testing results showed that the PC/ABS blend specimens failed in brittle manner under higher impact speeds with very few of whitening zones. Secondary cracks captured perpendicular to fracture surface were also found in the mid-plane of the scattered PC/ABS blend specimens. Investigation is then focused on this blend and the testing results describe that impact resistance of the specimen made of this alternative material is determined by ABS not by PC. Combination of structures between PC and ABS through the thickness in the core due to their immiscibility was observed by scanning electron microscope (SEM) on the etched PC/ABS specimen. This latter result well correlates the results obtained from the testing. It therefore reveals that immiscibility between PC and ABS in the blend plays an important role in determining the impact resistance of the components. This paper also presents simulative results of the test obtained from a FEA work by introducing a 3D- layered finite element (FE) model of the PC/ABS specimen to take into account effect of a layer in the core on the behavior of the blend.
Authors: Takahiro Omori, Hirotsugu Inoue, Noriyasu Kawamura, Minoru Mukai, Kikuo Kishimoto, Takashi Kawakami
Abstract: A method to predict impact load caused by drop impact of thin cone-shaped structures is investigated. The Hertzian contact theory and the spherical shell theory are applied for modeling the contact stiffness of the impact tip of the cone. Experiments and finite element simulations are performed for several cones to evaluate the accuracy of impact load prediction. It is shown that appropriate choice of contact stiffness model depending on the curvature and thickness of impact tip of the cone is necessary in order to predict the impact load accurately.
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