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利用径向基函数(RBF)神经网络优异的非线性逼近能力,将流线型玻璃钢覆盖件样件外形数据、加工余量、变形数据作为神经网络输入,在神经网络的输出上可以分别得到覆盖件曲面和模具曲面离散数据点。再通过神经网络的输出数据对曲面进行造型。通过在复杂曲面模具造型上的实际应用,证明该方法能够实现产品和工艺装备的并行设计,缩短产品研制周期,提高了设计和生产效率。 相似文献
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The flexible riser top connection to the floating unit is a critical region considering extreme loading and fatigue lifetime assessment and is generally protected by a bend stiffener to limit the curvature in this region. The top connection usually interface the floating unit with two main configurations: i) end-fitting and bend stiffener directly connected to a riser balcony or ii) riser connected to the floating unit in the end of an I-tube, which reduces the end-fitting bending loading, and bend stiffener assembled to a bellmouth with a given inclination in relation to the I-tube longitudinal axis. The traditional modeling approach considers the riser/bend stiffener system attached to the floating unit, representative of the first configuration. A more realistic modeling approach, capturing the complex interactions of flexible riser/bend stiffener with I-tube interface can be employed for preliminary assessment with less conservatism. In this work, a large deflection analytical beam model is developed for the riser top connection with I-tube considering the bellmouth transition region with a straight rigid surface followed by a curved section. The riser follows a nonlinear bending behavior described by a bilinear moment vs curvature function and the bend stiffener polyurethane material exhibits nonlinear elastic symmetric response represented by a power law function. It is assumed that there is no gap between the riser and the bend stiffener and the riser is fixed in the end-fitting position. The mathematical formulation of the statically indeterminate system results in three systems of coupled differential equations combined with the corresponding multipoint boundary conditions to be numerically solved by an iterative procedure. A case study is carried out with a 7” flexible riser protected by a bend stiffener connected to an inclined I-tube bellmouth. The system is subjected to extreme loading conditions and the influence of the sleeve shape and I-tube length on the riser curvature distribution, including the end-fitting position, and contact forces between the riser/sleeve and riser/bend stiffener sections are assessed. 相似文献
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Bend stiffeners are subjected to cyclic loading during offshore operation or when subjected to a controlled full-scale qualification test. Due to the viscoelastic nature of the polyurethane, energy is dissipated within the material volume and the structure may experience a temperature increase, a phenomenon known as self-heating. The top connection is a flexible riser critical region in terms of fatigue, being the bend stiffener the main responsible for curvature control. As the curvature distribution is highly affected by the nonlinear time–temperature bend stiffener response, a detailed thermo-mechanical assessment may become relevant for riser lifetime and polyurethane material failure assessment, specially during accelerated full-scale tests. In the present paper (Part I), the polyurethane experimental characterization and steady-state thermo-mechanical mathematical formulation are presented for the bend stiffener self-heating assessment. A steady-state formulation is derived for a temperature dependent linear viscoelastic large deflection beam model to estimate the heat generation during harmonic tip loading. The temperature field distribution is calculated through a three-dimensional steady-state thermal model considering the viscoelastic heat calculated from the mechanical model with an iterative scheme. Stress relaxation tests are performed at different temperatures to determine the viscoelastic properties followed by thermal properties characterization through differential scanning calorimetry and by the Flash method to determine the specific heat, thermal conductivity and diffusivity, respectively. In a companion paper (Part II) the iterative numerical scheme is detailed and a case study presented. 相似文献
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针对动车组在太原动车所瞬间接收反向HU码导致控停的疑难问题,剖析了相关影响因素,分析了电路初次改进后仍存在的不足,提出了电路二次改进方案并付诸实施,解决了原有问题,保证了高铁的正常运营。 相似文献
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在理解提速道岔五线制控制电路原理,掌握继电器动作逻辑的基础上,总结出适用于电动机控制电路的反位法,故障处理时能够按照流程化的处理方式,缩小故障范围,快速、准确查找出故障点。 相似文献
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在对汽车外形的局部改型中,由于逆向设计具有设计精度高、开发周期短及节约成本等优点,逐渐得到厂家的广泛采用。文章根据原型车前后保险杠造型,运用逆向工程原理以及CATIA软件中的模块构建出新的保险杠造型,依据曲线几何连续性条件,利用曲面断面线法、斑马线法及曲面反射性分析法来评价曲面的质量。最终得到更加美观的轿车保险杠外表面造型。该方法大大提高了轿车外表面改型的开发效率。 相似文献
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随着我国经济实力不断提高,当前人们对于物质生活的需求有着本质的提升,汽车作为高端产品,方便了人们的日常出行,成为当前人们物质生活水平的象征,但汽车的研发与制造过程缓慢,尤其我国汽车研发产业起步较缓,国产汽车更新换代速率较慢,汽车质量、性能、造型难以满足当前人们的需求,而基于已有物质的逆向工程能够改变传统"从无到有"的研发思路,能在短时间内提高我国汽车的研发制造水平,基于此,文章首先简要分析了汽车研发制造领域内逆向工程技术的内涵,随后从四个方面讲述了汽车研发制造领域内逆向工程技术的使用策略,以此来供相关人士交流参考。 相似文献