Three-dimensional shock wave reflections from a cone with angles of attack were examined experimentally and numerically. The Mach number of the incident shock wave was 1.35. The attack angles of a cone model with a semi-apex angle of 30° were 10° , 15° , 20° and 25°. The experiments were performed using a vertical shock tube, and the wave configurations were visualized using a conventional schlieren system. Numerical simulations of the shock wave reflections were also conducted using unstructured solution adaptive grids. The triple-point distributions around the cone were reconstructed from the visualized wave configurations, and then compared with those obtained from the numerical simulations. The characteristic flow fields behind a curved Mach stem around the cone are revealed.

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This paper presents a method for calculating and estimating the parameters of a bus load model in power system stability studies. There are two basic approaches to obtain load voltage characteristics. One is to directly measure the voltage sensitivity of load active power and reactive power at substations or feeders. The other is to build up a composite load model from knowledge of the mix of load class. It is effective to calculate load voltage characteristics by utilizing the feature of both approaches.
The bus load model we propose consists of a load branch with equivalent impedance to the feeders and transformers in the 66kV or 77kV distribution system, reactive power compensation and load, which is composed of three load classes, such as industrial, commercial and residential. The load voltage characteristics are calculated from voltage and current measured at several feeders, where voltage sag due to a fault occurs. The static load voltage characteristics are represented the exponents, and have correlation with temperature. Exponents of load class are calculated from the measured exponents, temperature and load class mix by least-squares method. The validity to be applicable for the estimated exponents by the exponents of load class and the mix of load classes is evaluated. The bus load using this exponents will be adaptable to not-measured bus loads. They will make stability simulation results more accurate.

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Buried pipelines may be deformed due to earthquakes and also corrode despite corrosion control measures such as protective coatings and cathodic protection. In such cases, it is necessary to ensure the integrity of the corroded pipelines against earthquakes. This study developed a method to evaluate the earthquake resistance of corroded pipelines subjected to seismic motions. Pipes were subjected to artificial local metal loss and to axial cyclic loading tests to clarify the cyclic deformation behavior until buckling occurs under seismic motion. As the cyclic loading progressed, displacement shifted to the compression side due to the formation of a bulge. Finally, the pipe buckled after several cycles. To evaluate the earthquake resistance of different pipelines, with varying degrees of local metal loss, a finite-element analysis method was developed that simulates the cyclic deformation behavior. A combination of kinematic and isotropic hardening components was used to model the material properties. These components were obtained from small specimen tests that consisted of a monotonic tensile test and a low cycle fatigue test under specific strain amplitude. This method enabled the successful prediction of the cyclic deformation behavior, including the number of cycles required for the buckling of pipes with varying degrees of metal loss.

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This study focuses on the opening mode of induction bends; this mode represents the deformation outside a bend. Bending experiments on induction bends are shown and the manner of failure of these bends was investigated. Ruptures occur at the intrados of the bends, which undergo tensile stress, and accompany the local reduction of wall thickness, i.e., necking that indicates strain localization. By implementing finite element analysis (FEA), it was shown that the rupture is dominated not by the fracture criterion of material but by the initiation of strain localization that is a deformation characteristic of the material. These ruptures are due to the rapid increase of local strain after the initiation of strain localization and suddenly reach the fracture criterion. For the evaluation of the deformability of the bends, a method based on FEA that can predict the displacement at the rupture is proposed. We show that the yield surface shape and the true stress-strain relationship after uniform elongation have to be defined on the basis of the actual properties of the bend material. The von Mises yield criterion, which is commonly used in cases of elastic-plastic FEA, could not predict the rupture and overestimated the deformability. In contrast, a yield surface obtained by performing tensile tests on a biaxial specimen could predict the rupture. The prediction of the rupture was accomplished by an inverse calibration method that determined the true stress-strain relationship after uniform elongation.

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