Research on Pressure Measuring Device with Magnetic Fluid

Magnetic fluid is a novel material which could be applied in many fields including sensors, sealings, bilmedicines, and so on. Its super magnetism and fluidity could be used in the sensor as an inducting core. Magnetic fluid and its characteristics were introduced to adapt to the application in the pressure measuring devices. A pressure measuring device with magnetic fluid was proposed and the structure was analyzed and designed according to the characteristics of magnetic fluid. The working principle of pressure measuring device with magnetic fluid was analyzed, and the structure of pressure measuring device was designed and reformed to avoid the overflow and recovery of excessive of magnetic fluid. One arm of the U tube was designed to be a large cylinder to storage large quantities of magnetic fluid. The higher the required precision is, the larger the diameter of one arm should be designed with respect to the other arm of the tube. The measuring range of designed device could also be adjusted as needed. The measuring efficiency of the device could be improved by the designing and reforming work.

Analisis Daya Dukung Lateral pada Suction Pile dengan Menggunakan Metode Numerik. (Hal. 96-106)

ABSTRAKSuction Pile merupakan fondasi berbentuk silinder baja berdiameter besar yang tertutup pada bagian atas dan terbuka pada bagian bawah. Fondasi ini sering digunakan untuk menyokong bangunan offshore dan platforms. Beban yang diterima oleh suction pile merupakan beban aksial yang berasal dari beban strukturnya dan juga beban lateral dari tekanan tanah dan air laut di sekelilingnya. Analisis daya dukung lateral pada suction pile dilakukan dengan menggunakan metode numerik, yaitu menggunakan software PLAXIS 3D dengan soil model Mohr-Coulomb dan Hardening Soil, serta menggunakan metode analisis, yaitu metode COM624 dari Federal Highway Administrasion (FHWA). Pemodelan suction pile dilakukan dengan cara memvariasikan panjang dari suction pile dengan mutu baja, diameter suction pile, dan parameter tanah yang sama. Berdasarkan hasil dari penelitian bahwa semakin panjang penampang dari suction pile yang digunakan, maka daya dukung lateral yang diperoleh semakin meningkat dikarenakan letak titik jepit yang masih berubah.Kata Kunci: suction pile, daya dukung lateral, titik jepit, Mohr-Coulomb, Hardening Soil ABSTRACTSuction pile is a large cylinder-shaped steel foundation which has a closed top and an open bottom. This foundation is often used to support offshore buildings and platforms. The loads resisted by the suction pile are the axial load from its own structure weight and the lateral load caused by soil and deep-sea pressure around it. Analysis of lateral bearing capacity of suction pile is done by using numerical method is conducted using commercial software PLAXIS 3D, with Mohr-Coulomb and Hardening Soil as the soil model and analysis method is conducted using COM624 method from Federal Highway Administrasion (FHWA). Suction pile model is designed by varying the suction pile lengths of equal steel quality, suction pile diameter, and soil parameter. The result of the research showed that the longer the cross section of the suction pile used, the higher its lateral bearing capacity, due to the location of the fixity point is still changed.Keywords: suction pile, lateral bearing capacity, fixity point, Mohr-Coulomb, Hardening Soil.

A fast calculation method of large-cylinder asymmetrical rolling force considering shear effect

An analytical model for large-cylinder asymmetrical rolling is proposed based on an improved slab method, which can predict the rolling force more quickly. In this method, uneven normal and shear stresses acting on the vertical side are supposed. In the solution, the upper and lower contact lengths are different, and the roll gap is divided into four slabs. Moreover, the effects of the rolling parameters such as roll speed ratio, roll radius, exit thickness, and radius of cylinder on the rolling force and cross-shear zone ratio are investigated. The cross-shear zone ratio, which means the shear effect, is a key parameter in reducing rolling force and microstructure refinement. This method is conducted with the experimental and finite element verification, and good agreement has been found. It should be noted that the calculation result can be obtained rapidly and easily by this proposed model. Therefore, the present model is suitable for online application.

Numerical Investigations of Flow Past a Rotating Stepped Cylinder

Unsteady numerical investigations of flow past a partially rotating stepped cylinder have been performed. The objective of the study was to investigate whether the wake characteristics could be controlled with rotation of one cylinder while the other remains stationary and how partial rotation impacts the aerodynamic forces. The stepped cylinder was 2 m in length where the first meter was a round cylinder 5 cm in diameter followed by a 2:1 step down cylinder. Two round end plates, 0.1 cm thick and 40 cm in diameter, were placed at each end. The end plates were positioned at 5 degrees with respectto the incoming flow to remove the end effect on vortex shedding. All simulations were performed using the Siemens PLM STAR-CCM+ CFD software with K-ω turbulence model. The time step was 0.00083 second to resolve the flow for each 10 degrees rotation. 1200 time steps were used. The investigations were performed with one cylinder rotating while the other remains stationary. Four cases were investigated. When either cylinder was rotating, the RPM was maintained at either 2000 or 4000 while the free stream velocity was maintained at 10 m/sec. The Reynolds number for the large and small cylinders were approximately 32,258 and 16,129, respectively. The corresponding velocity ratios λ for the large cylinder rotating were 0.5 and 1.0, and 0.25 and 1.0 for the small cylinder. Previous investigations have classified vortical structure in the wake of a step cylinder in terms of L-cell (for large cylinder), S-cell (for small cylinder) and N-cell (the region in between). When the large cylinder is rotating, at λ = 1.0, the velocity and vorticity in the wake of the large cylinder is increased. The N-cell initially has a larger velocity than the L-cell and is at a slanted angle. A suction effect was observed in the near wake region, causing the flow in the L-cell to coalesce near its midsection. The vortices originated at the step were connected to the S-cell at a lower speed. The overall lift to drag ratio (L/D) for this case was 1.14. When λ = 0.5, vortex structures were maintained through the three different cells with increased variations in cell frequency across the large cylinder, the L/D was reduced to 0.36. When the small cylinder was rotating, at λ = 0.5, vortex shedding was suppressed within the S-cell and considerable distortion was observed in the vortical structure in the wake of the large cylinder. However, the N-cell had similar structure as when large cylinder was rotating, but connecting to the L-cell at a larger slanted angle. When λ was reduced to 0.25, shedding was observed across the length of the cylinder with increased variations. The corresponding L/D ratios for these cases were both at 0.2.