Unreinforced Flat Oval Duct Deformation Testing and Modeling

Unreinforced 12 in. × 23 in. (305 mm × 584 mm) galvanized steel flat oval ducts were tested to measure deformations when internal static gauge pressures were applied. The experiments were performed on spiral seam non-corrugated duct. Finite element models with discrete ring seams and an average wall thickness approach were utilized to represent the continuous spiral seam, and therein predict duct deflections at prescribed locations along the duct wall. Predicted deflections from the finite element models were tabulated and compared to experimental data. Satisfactory agreement between model predictions and test data were obtained from a non-linear finite element analysis that employed a simplified average wall thickness to characterize the spiral seam and duct wall. It is straightforward to implement the average wall thickness methodology in finite element modeling of duct deformation.

Fabrication of NiO Nanorings by Bubble-Bursting Bubbles as Templates

A simple and low-cost method based on a heat-treating of Ni (NO3)2/SiO2film has been developed for fabricating NiO nanorings. The as-prepared nanorings have an inner diameter of 150-250nm and an average wall thickness (namely wire diameter) of approximately 20 nm on the surface of SiO2matrix. Furthermore, a growth mechanism, namely bubble-bursting bubbles as templates was tentatively proposed for understanding the formation of the NiO nanorings.

Improved Prediction of External Pressure Collapse of Seamless Pipe

Seamless pipe typically features well controlled average wall thickness around its cross-section, but is prone to significant local thickness variation arising from the manufacturing process. Pipeline design codes, such as DNV OS-F101, provide little guidance on how to treat thickness variation whilst designing for collapse resistance. Standard practice is to consider minimum wall thickness across the whole cross-section, an assumption that two dimensional finite element simulations have proven conservative. This justifies the need for an improved design method. A program of simulations has been carried out to investigate the effect of wall thickness variation on collapse pressure. A modification to the DNV OS-F101 collapse design equation using average wall thickness over the whole crossection together with a fabrication factor is presented based on the results of this study. The fabrication factor de-rates the collapse pressure according to the amount of thickness variation present. The correction has been calibrated for thickness variations up to the maximum permitted by typical line pipe specifications. A number of FE trials demonstrate that the proposed formula predicts simulated collapse pressures with 98% accuracy. Adopting this method could provide significant wall thickness savings for deep water flowlines which in turn could lead to a reduction in steel costs and transportation and lay vessel requirements.

Effect of Thinning on the Wood Structure in Annual Growth Rings of Japanese Larch (Larix Leptolepis)

The objective of this study was to determine the effect of thinning on the annual ring structure and the cross-sectional dimensions of tracheids in plantation-grown Japanese larch (Larix leptolepis). Annual ring width, earlywood width and latewood width increased significantly after thinning. The width of the band of nonflat latewood tracheids in the annual ring increased more than that of flat latewood tracheids. Thinning did not significantly affect latewood percentage. The average radial diameter of both earlywood and latewood tracheids increased after thinning. After thinning, average wall thickness of earlywood tracheids increased, while that of latewood tracheids decreased. Cell wall percentage in earlywood was not influenced significantly by thinning, but latewood cell wall percentage decreased. The changes of the average radial tracheid diameter, the average wall thickness of tracheids and cell wall percentage from earlywood to latewood within a growth ring became more gradual after thinning. However, thinning did not affect significantly the cell wall percentage of the whole growth ring. This study suggests that thinning has little effect on wood density of the whole growth ring in Japanese larch.