Thermal spray-coated composite tool is one of the rapid tooling techniques used for moulding applications such as in automotive and food industries. The coating/substrate interfacial condition, hence, the finished mould quality, depends on the surface characteristics of the master model (substrate). Characterizations of surface deformations of the master model and the critical thickness of the coating on the polymer substrate were carried out in this work. The progressive deformation of the master model made from polypropylene (PP) was simulated during the solidification state, using linear and nonlinear finite element analysis (FEA&NFEA). The mechanical properties of the PP substrate and coating material are important parameters. In order to study their effects, the spraying conditions were kept constant for all specimens in the experiment. The critical thickness of the coating and the spring-back levels due to variation in coating thicknesses produced via thermal spraying process can be investigated by FEA&NFEA. This method can then be performed on other components to clarify the effects of the coating thickness in order to keep the deformation of polymer substrate of the thermal spray processing.

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Steel conveying rollers used in hot rolling mills must be exchanged frequently at great cost because hot conveyed strips induce wear and deterioration on the surface of roller in short periods. In this study, new roller structure is considered which has a ceramics sleeve connected with two steel shafts at both ends by shrink fitting. Here, although the ceramics sleeve can be used for many years, the steel shaft sometimes has to be exchanged for reconstruction under corrosive action induced by water cooling system. Since the thermal expansion coefficient of steel is about five times larger than that of ceramics, it is necessary to investigate how to separate the shrink fitting system by heating outside of sleeve and cooling inside of the shaft. In this study, the finite element method is applied to analyze the separation mechanism by varying the geometrical and thermal conditions for the structure. Finally the most appropriate dimension and thermal conditions have been found, which may be useful for designing of new rollers.

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A simple method was presented to conduct the low-temperature metal induced crystallization of an amorphous silicon (a-Si) film using nano-sized nickel particles. The effects of the annealing temperature and the duration on the morphology and the crystallized size of the induced polycrystalline silicon (poly-Si) film were investigated using a field emission scanning electron microscope (FE-SEM), a twin thin-film X-ray diffractometer (XRD), a Raman spectrometer, and an energy dispersive spectrum (EDS). In addition, the residual nickel and the I-V characteristics of the poly-Si film were measured using a secondary ion mass spectrometer and a semiconductor parameter analyzer, respectively. The crystalline peak of Si (311) was obviously detected even at an annealing temperature of 400°C and the duration of 1 h. The crystallization temperature was lowered due to the high activity of the nano-nickel particles. Therefore, this study supports the feasibility of applying nano-nickel particles to crystallize the a-Si film.

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A new method for detecting delamination cracks in carbon fiber reinforced polymer (CFRP) laminates using changes in electrical resistance was developed in a previous study. It was possible to detect delamination cracks without sampling the data from intact structures and to prevent false diagnoses from changes in electrical resistance caused by damage to the electrical contacts at the electrodes. As a result of the study, delamination of at least 5.3 mm in diameter caused by a quasi-static load in a quasi-isotropic-plied CFRP plate was detectable without sampling the data from intact structures. However, the proposed diagnostic method has not yet been experimentally performed for detecting delaminations subjected to impact loads. Although it is unfortunate that there is not much difference between damage of FRP laminates subjected to low-speed impacts and those subjected to quasi-static loads, broken fibers in the surface layer and plastic deformation such as a dent accompanied by delamination might depend on the rate of strain. It is also necessary to ensure that the diagnostic method provides correct diagnoses even if impact damage of electrical contact occurs at the electrodes. The diagnosis was not affected by chipped electrodes except for through chips. The present study employs the diagnostic method for delamination cracks and damage to electrical contacts of an electrode subjected to falling weight impact loads and dents from quasi-static loads.

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An impact load on a thick carbon fiber reinforced plastic (CFRP) plate usually causes a dent. The dent results in a decrease of electrical resistance. Our previous paper demonstrated the effect of the dent in the measurement of electrical resistance change of a thick CFRP plate subjected to impact loading. The present paper focuses on the electrical resistance decrease caused by the dent. Numerous FEM analyses were performed, and the relationship between electrical resistance changes and delamination location was constructed, by measuring the response surfaces. Several experiments were conducted and the measured electrical resistance changes were used to predict damage location from the response surfaces. The present study shows that the dent decreases the electrical resistance change ratio even in the adjacent segments, and the electrical resistance changes caused by the dent enable us to monitor the damage location. FEM analyses for a projected area model are sufficient to construct the relationships without resorting to many experiments.

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In the framework of atomistic-level modeling, a new technique for predicting the interface strength of the resin-mold structure has been proposed. We show that our proposed interfacial fracture energy is effective in determining the adhesion strength of three kinds of interfaces between epoxy resin and metals (Cu, Fe and Al). We also discuss the multi-scale connection between nano-scale adhesion and macro-scale interface strength in terms of interface roughness. When the interface with roughness is subject to shear load under vertical residual stress in experiments, FEM analysis taking account of the effect of interface roughness shows that local debonding (mode-I) due to the tensile stress induces global delamination. Our proposed method for dealing with local mode-I debonding by use of molecular dynamics is found to be effective in simulating the interfacial fracture with the shear load.

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