Finite element analysis (FEA) was done for semi-elliptical axial surface cracks in pipes under internal pressure in order to provide J-integral solutions for assessing the structural integrity of cracked pipes of nuclear power plants. Elastic and fully plastic solutions were obtained for wide ranges of geometrical and material conditions. The accuracy of the J-integrals estimated using the obtained solutions was confirmed through additional FEA for non-linear elastic material under various magnitudes of pressure. The obtained solutions were shown to be valid for structural integrity assessments regardless of material and geometrical conditions and the magnitude of pressure. The maximum error in failure pressure derived using the obtained J-integral solutions was 6%.

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The out of plane static analysis and stability analysis of curved beams of variable curvature on 2-D plane are investigated. The general solutions under various loadings are demonstrated. The analytical solutions of circular, cycloid, and spiral curved beams under pure moments are shown. The analytical solutions of circle, cycloid logarithmic spiral and spiral cantilever curved beams under concentrated load are presented as well. The out-of-plane critical load of a circular ring under uniform radial load is derived. Several critical loads are derived for various out-of-plane boundary conditions. The results are compared to the result by ANSYS. The results are consistent.

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With the aim of achieving stable operation of circular saws, this study finds the solution for the optimization problem of choosing a set of parameters for additional tensioning in a rotating circular saw that is subjected to both a local temperature distribution arising from the thermal load caused by the blade-workpiece friction and the in-plane plastic strain introduced by original and additional tensioning. The solution for in-plane forces is obtained on the basis of plate bending theory, and modal analysis for the out-of-plane behavior affected by the in-plane forces is performed. Numerical calculations are performed to investigate the effects of additional tensioning on the natural frequencies. The optimization problem to maximize, with respect to the intensity, location, and width of additional tensioning, the natural frequency of the most critical mode is solved by use of a genetic algorithm, and the optimal parameters of additional tensioning are determined at computational costs that are considerably lower than those of 100% inspection.

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The whole process of a prismatic dislocation loop (PDL) formation around a misfitting spherical inclusion embedded in a homogeneous isotropic matrix is studied using level set dislocation dynamics. Two small half loops are first punched out around a spherical particle on a specific cylindrical surface along which the magnitude of the misfit shear stress reaches the maximum among all the homocentric cylinder surfaces. The edge dislocation segments glide away from the inclusion-matrix interface under the influence of the shear stress, while the screw components cross slip around the cylindrical surface. When two ends with opposite orientations of the top and bottom half dislocation loops intersect, the screw segments annihilate and a PDL is produced. Level set dislocation dynamics successfully presents such a topological evolution under elastic dislocationdislocation/ dislocation-inclusion interactions. During the process of PDL formation, the total elastic strain energy in the system first increases as the initial half loops expand on the cylindrical cross-slip plane and reaches the climax when two loops merge into a middle-bended loop, and then decreases since the middlebended loop becomes a PDL. Finally, it becomes saturated as this dislocation loop gradually glides away from the inclusion-matrix interface.

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The small punch (SP) creep test has been proposed as a semi destructive testing methodology to examine the residual creep life of high temperature components. A series of SP creep tests were conducted on low alloy steel at 600°C both in air and in high vacuum to investigate the influences of both testing environment and the fillet radius of the lower die holder on the SP creep rupture life. The thickness of the oxide scale on the SP creep specimen in air increased with the test duration, e.g., about 30µm in thickness after a 400 hour exposure. The SP creep rupture life in air reduced to a half of the life in vacuum due to an increase in the actual stress in the specimen and also the coefficient of friction. In addition, the magnitude of the fillet radius at the lower die holder also affected the SP creep rupture life. The influence of the fillet radius on the SP creep rupture life was studied both experimentally and numerically. The SP creep rupture life with a smaller fillet radius of the lower die holder had twice the rupture life compared to that with a larger fillet radius. This effect was also demonstrated by the FE analysis.

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