The goal of this study is to numerically compare solutions and algorithms determined by element- and node-wise topology optimization designs for dynamic free vibration-resistance structures. As another version in the fields of topology optimization methods, the study supports the node-based optimization rather than the classical element-based optimization comparing two methods. The terms element-and node-wise denote the usage of element and node density as design parameter, respectively. For static problems solution comparisons of the two types for SIMP topology optimization designs have already been introduced by the author⁽¹⁾. For dynamic topology optimization problems the objective is in general related to maximum eigenfrequency optimization subject to a given material limit since structures with a high fundamental frequency tends to be reasonable stiff for static loads. For dynamic problems SIMP material is used in this study and an implemented optimization method is the method of moving asymptotes (MMA). Numerical applications topologically maximizing the first natural eigenfrequency for dynamic concrete deep beam designs depending on element or node density verify differences of solutions and algorithms between dynamic element- and node-wise topology optimum designs.

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In order to improve performance of anti lock brake system (ABS) and detect condition of road surface, intelligent tires that monitor strain of interior surface and rolling radius of tire are demanded. However, the high stiffness of an attached sensor like a strain gauge causes debonding of sensors from tire rubber. In the present study, noncontact concurrent monitoring method is proposed using digital image correlation method (DICM) and spotlight projection. In-plane strain and out-of-plane displacement (rolling radius) are calculated by using image processing with an image of interior surface of tire that is taken with a single CCD camera fixed on wheel rim. New monitoring system is applied to Al beam and commercially available radial tire. As a result, this monitoring system is proved to be able to measure in-plane strain and out-of-plane displacement with high accuracy, and confirmed to be effective for concurrent monitoring of tires.

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This paper presents characterization and evaluation of a silicon nitride plate subjected to repeated impact by a small but hard particle at velocity in a range from 80 to 160 m/s. It specifically focuses on damage patterns in relation to repeated impacts. In addition, the paper also provides a finite element analysis in conjunction with the Tuler-Butcher damage model that is employed to study the formation of the damages during the multiple impact events. The results of the analysis using a very fine mesh indicated that during the contact of the projectile and the plate, the area beneath the contact surface is mainly governed by a compressive stress state. However, a small-adjacent area encircled the compressed region was in a high tensile stress state. The largest tensile stress in the area instantly occurred after the projectile touched the ceramic within a time significantly shorter than the time required for the maximum contact. Majority of the ring cracks observed in the experiments occurred in this area. Furthermore, the ring cracks grew upon further application of impact. Finally, the analysis indicated that the growth of the ring crack led to formation of the spall or the cone crack.

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Thin films of lead-free piezoelectric ceramics (Bi_1/2Na_1/2)TiO₃ (abbreviated as BNT) were prepared on pure titanium substrates by a hydrothermal method. The properties of BNT films synthesized from the reaction solution with various contents of bismuth and titanium were investigated using SEM, EDX, XRD and other instruments. Moreover, the effects of the concentrations of starting materials on permittivity and piezoelectric effect of deposited BNT films were discussed. The results showed that an impurity of Bi₂O₃ crystal was produced on the surfaces of all deposited films. With assumption of deposited films as an system of (1-x) (Bi_1/2Na_1/2)TiO₃-xBi₂O₃, the BNT content was calculated from the Bi/Ti ratio of the EDX results. The optimized synthesis condition was determined on the evaluation target of the calculated BNT content. In addition, the unimorph cantilever type actuators were fabricated by BNT deposited samples, and their piezoelectric responses were measured at their resonance frequencies under AC field. It was noted that the piezoelectric effect of the deposited BNT film was greatly dependent on its crystallization level.

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An exact approach is used to investigate the propagation of Bleustein-Gulyaev waves in a functionally graded piezoelectric substrate carrying a finite-thickness metal layer. The piezoelectric material is polarized in the direction perpendicular to the wave propagation plane and the material properties change gradually with the depth of the substrate. We here assume that all material properties of the substrate have the same exponential function distribution along the depth direction. The dispersion relation for the existence of the waves with respect to phase velocity is obtained analytically. The effects of the material gradient on the phase velocity and group velocity are discussed in detail. The displacement, electric potential, and stress distributions along the depth of the structure are calculated and plotted. Numerical examples show that the material gradient has a significant effect on the starting part of the wave mode and appropriate gradient distribution of the material properties can not only make the waves propagate along the surface but also decrease the interfacial stresses of the layered structure, which is in favor of designing acoustic wave devices with better performance. The existence condition of the waves at all values of wave number has also been obtained theoretically.

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Thermoplastic resin is often used to form molded material without post-curing or aging treatments. Creep and physical aging occur simultaneously in such material, and these effects are dependent on the time and temperature. The effects of physical aging after molding are also dependent on the thermal history of the material, and this has a large influence on the mechanical properties, especially creep. It is therefore necessary to control the progress of physical aging when designing materials. In this study, we examined the creep deformation of polycarbonate to determine the thermal history as the effect of physical aging on the creep behavior. The physical aging effects had a distinct time and temperature dependency that also affected the density of the material. Our findings showed that it was possible to calculate the effect of the thermal history on physical aging using only the relationship between physical aging and density.

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This study proposes the cohesive zone model (CZM) for predicting fatigue damage growth in notched carbon-fiber-reinforced composite plastic (CFRP) cross-ply laminates. In this model, damage growth in the fracture process of cohesive elements due to cyclic loading is represented by the conventional damage mechanics model. We preliminarily investigated whether this model can appropriately express fatigue damage growth for a circular crack embedded in isotropic solid material. This investigation demonstrated that this model could reproduce the results with the well-established fracture mechanics model plus the Paris' law by tuning adjustable parameters. We then numerically investigated the damage process in notched CFRP cross-ply laminates under tensile cyclic loading and compared the predicted damage patterns with those in experiments reported by Spearing et al. (Compos. Sci. Technol. 1992). The predicted damage patterns agreed with the experiment results, which exhibited the extension of multiple types of damage (e.g., splits, transverse cracks and delaminations) near the notches.

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This study presents a numerical simulation to predict damage progress in notched composite laminates under cyclic loading by using a cohesive zone model. A damage-mechanics concept was introduced directly into the fracture process in the cohesive elements in order to express crack growth by cyclic loading. This approach then conformed to the established damage mechanics and facilitated understanding the procedure and reducing computation costs. We numerically investigated the damage progress in holed CFRP cross-ply laminates under tensile cyclic loading and compared the predicted damage patterns with experiment results. The predicted damage patterns agreed with the experiment results that exhibited the extension of multiple types of damage (splits, transverse cracks, and delamination) near the hole. A numerical study indicated that the change in the distribution of in-plane shear stress due to delamination induced the extension of splits and transverse cracks near the hole.

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