Calculation of hydrodynamics for semi-submersibles based on NURBS

Accurate hydrodynamic calculations for semi-submersibles are critical to support modern rapid exploration and extraction of ocean resources. In order to speed hydrodynamic calculations, lines modeling structures were separated into structural parts and then fitted to Non-uniform Rational B-spline （NURBS）. In this way, the bow and stern section lines were generated. Modeling of the intersections of the parts was then done with the universal modeling tool MSC.Patran. Mesh was gererated on the model in order to obtain points of intersection on the joints, and then these points were fitted to NURBS. Next, the patch representation method was adopted to generate the meshes of wetted surfaces and interior free surfaces. Velocity potentials on the surfaces were calculated separately, on basis of which the irregular frequency effect was dealt with in the calculation of hydrodynamic coefficients. Finally, the motion response of the semi-submersible was calculated, and in order to improve calculations of vertical motion, a damping term was affixed in the vertical direction. The results show that the above methods can generate fine mesh accurately representing the wetted surface of a semi-submersible and thus improve the accuracy of hydrodynamic calculations.     

EQ140型汽车转向传动装置花键齿形改进

EQ140型转向传动装置为矩形花键,用户在使用中发现花键耐磨性差、寿命短。为提高花键的耐磨性,采用了不经磨加工的渐开线花键取代矩形花键,使耐磨性显著提高,满足使用要求。     

北美粉末冶金行业的现状与前景

用于福特汽车扭力变速卡车齿轮箱中的输出轴套,由位于依利诺斯洲Schiller Park的芝加哥粉末金属产品公司制造,在2004年黑色金属粉末行业联合会MPIF国际设计比赛中得奖.零件是由温挤压成形技术制造的,最小密度为7.2g/cm^3,最小极限抗拉强度为1 070 MPa.外螺旋齿和直齿渐开线花键接近最终形状.该零件最初设计是锻件,使用粉末冶金温挤压技术后可以节约30%的成本.更好的粉末和新的工艺扩大了粉末冶金业的应用范围。     

矩形花键滚刀计算机辅助设计

本文介绍在ＡＳＴ４８６型计算机上成功编制的“矩形花键滚刀计算机设计程序”及程序功能、程序原理。本文给出了矩形花键滚刀计算机充程框图与程序清单及输出结果范例。