Optimal Design of Surface Structure of a Magnetic Head

Currently, the surface structure of a magnetic head has been transferred from a positive to a negative model. In order to increase magnetic storage density and to decrease the flight height, the surface structure of a head needs to be optimized continually. In the present paper, the influence of surface structure of a negative magnetic head on its flight attitude is analyzed in brief by both theoretical analysis and numerical simulation. Firstly, based on theoretical analysis, one-dimensional model of optimal design is built whose results play an important role in guiding for the two-dimensional model. Secondly, to analyze the impacts of different slructures of negative pressure heads, the original head structure is divided into five zones; the impacts of different zones on both pressure distribution and load carrying capacity were detailed analyzed by numerical analysis. Thirdly, remain the leading-head structure of the negative head, and optimized tail-end structure can be gained by the regional planning strategy to control the gas film pressure distribution. With layout strategy, three kinds of structures of the head were designed. The results show that the tail-end structure impacts on the flight performances significantly and the middle boss plays a major role on positive pressure, while the bilateral bosses lying in either side play assistant regulating role. The structures of bilateral bosses have slightly impact on pressure distribution. The results also show that an optimum tail structure can meet the needs of a lower flight height and a larger magnetic storage density.

Multi-stage optimum design of magazine type automatic tool changer arm

To enhance machining efficiency,tool change time has to be reduced.Thus,for an automatic tool changer attached to a machining center,the tool change time is to be reduced.Also the automatic tool changer is a main part of the machining center as a driving source.The static attributes of the automatic tool changer using the commercial code,ANSYS Workbench V12,were tried to interpret.And the optimum design of automatic tool changer arm was proposed by performing the multi-stage optimum design.The shape optimization of the automatic tool changer was proposed and the result was verified to obtain acceptable improvements.It is possible to obtain an optimized model in which the maximum deformation,maximum stress,and mass are reduced by 10.46%,12.89% and 9.26%,respectively,compared with those of the initial model.Also,the results between conventional method by the design of experiments and proposed method by the multi-stage optimum design method were compared.

Optimum Environmental Load Design Criterion for Marine Structures Based on Investment and Benefit Analysis

Marine structures operating in natural ocean environment are subjected to various stochastic loads. For design of the marine structures, the most important task is to determine environmental load design criterion. This paper presents a method to determine the optimum environmental load design criterion for marine structures. This method is based on the investment and benefit analysis and it can reach the design purpose of decreasing total costs during the service life of the structures and increasing economic benefits.

OPTIMUM DESIGN BASED ON RELIABILITY IN STOCHASTIC STRUCTURE SYSTEMS

The optimum design method based on the reliability is presented to the stochastic structure systems （i. e., the sectional area, length, elastic module and strength of the structural member are random variables ） under the random loads. The sensitivity expression of system reliability index and the safety margins were presented in the stochastic structure systems. The optimum vector method was given. First, the expressions of the reliability index of the safety margins with the improved first-order second-moment and the stochastic finite element method were deduced, and then the expressions of the systemic failure probability by probabilistic network evaluation technique（PNET） method were obtained. After derivation calculus ,the expressions of the sensitivity analysis for the system reliability were obtained. Moreover, the optimum design with the optimum vector algorithm was undertaken. In the optimum iterative procedure, the gradient step and the optimum vector step were adopted to calculate. At the last, a numerical example was provided to illustrate that the method is efficient in the calculation, stably converges and fits the application in engineering.

Research and design of the main equipments and structure of Xiangjiaba shiplift

The type of pinion and rack vertical shiplifts has been developed in recent a couple of years in the construction of dams.But the design methods and methodologies have rarely been discussed in literature.The Xiangjiaba shiplift is the second shiplift of this type following the Three Gorges shiplift.Being aimed at the technological rationality of the design in synthetically considering security,economy and applicability,this paper presents the research results of some vital issues relating the design of the Xiangjiaba shiplift,including the determination of design water depth of ship chamber based on fluid numeral computation and physical model test,the optimum design of general layout of main equipments and the civil structure of the Xiangjiaba shiplift,the finite element method(FEM) analysis of stress,vibration modes and the buckling of ship chamber,antiseismic research and the design of structures and mechanisms of the shiplift and the optimum design of driving mechanisms.This research provides the theoretical basis for the design of the Xiangjiaba shiplift.The design principles and research methods are valuable for the design of the same type of shiplifts.

Optimum Design for Offshore Platform Structural Reliability

In this paper, the main problems concerning reliability design of offshore platform structure are described and the general steps for the use of Safety Coefficient Method are presented.

STUDY ON HYDRAULICALLY OPTIMUM DESIGN OF PUMP SUMPS

In past years a great deal of research work for the hydraulic design of pump sumps has been executed by means of experiments. Due to the differences of their experimental conditions, there were some obvious differences between the design rules suggested from different researchers. In this paper a method based on the 3-D numerical simulation of turbulence flow has been applied to hydraulically optimize the geometrical parameters of pump sumps, which makes it possible to establish the hydraulic criteria of design for pump sumps theoretically.

Optimum structural design of full-scale steel buildings using drift-tribe-charged system search

In this paper,the potential of utilizing improved metaheuristic approaches in optimal design of building structures is concerned.In this regard,the drift-tribe-charged system search algorithm is proposed that the position and velocity updating processes of the charged system search is developed by implementing the mathematical presentation of the free-electron model utilized for metal conductors.In addition,the searching phase of the developed algorithm is also divided into three separate phases in order to improve the convergence capability of the algorithm.By means of these modifications,the exploitation and exploration rates of the standard algorithm are enhanced.In order to determine the ability of the proposed improved metaheuristic method considering some complex optimization problems,a 10-story steel building structure with 1026 structural members alongside a 60-story structure with 8272 members are utilized as numerical examples.The overall capability of the developed metaheuristic approach is compared with other metaheuristics.A total number of 30 independent runs have been conducted for each of the standard and proposed methods while a statistical analysis is also conducted for comparative purposes.The obtained optimum results demonstrated that the proposed metaheuristic approach is capable of preparing better outcomes than other metaheuristics.

考虑多种作用效应的表面防渗聚脲涂层非线性分析及设计

聚脲与聚氨酯相比,具有绿色环保、耐久性好、力学性能优异、施工面适应性强等优势,聚脲基防渗层被广泛应用于水工结构中。鉴于防渗聚脲尚无成型的结构设计计算理论,惯常采用的经验性设计可能会导致不安全、不合理、不经济的设计结果,本研究通过探讨聚脲基表面防渗涂层非线性分析的关键理论,基于有限单元法建立了非线性数值模型。在涂层基面开裂、水压荷载作用、伸缩缝变形等不同受力工况下,通过对材料的受力变形行为、剥离行为、破坏模式等分析,总结了涂层受力变形规律,并基于分析结果,提出表面防渗聚脲设计流程。研究表明:对于水压作用下的涂层基面开裂工况,涂层最大应力随水压荷载、粘结强度增大而增大,随开裂宽度变化不显著,涂层剥离长度随粘结强度增大而减小,随开裂宽度增大而增大;对于伸缩缝变形工况,涂层剥离长度均随涂层厚度增大而增大,涂层剥离长度随伸缩缝变形量增大而增大,随粘结强度增大而减小,剥离长度随水压荷载变化趋势不显著;涂层最大应力随涂层厚度增大而减小,随粘结强度增大而增大,随水压荷载增大而逐渐增大。最终基于数值分析结果提出了考虑伸缩缝变形工况下的聚脲涂层结构设计方法,形成设计流程并计算机软件化。

空气预热器的设计计算和数值分析

对完成设计的工艺目标,将室温空气加热到一定温度时,空气预热器需要的电加热功率进行计算,并对相关设备结构进行设计。利用Workbench有限元分析软件建立空气预热器流场的数值分析模型,分析设备内流场情况,从理论上了解具体的混合和传热状态,考察工艺计算和设计的正确性。此外,还研究了相关工艺参数和结构设计对设备性能的影响,认为提高空气处理量,会快速降低出口温度,并显著提高设备阻力,但空气受热更加均匀;增加加热功率,出口温度和设备阻力逐渐升高,但空气受热均匀程度有所降低。此外,设备内布置折流板,能够有效促进流场湍流程度,提升设备出口温度,增加混合传热效果,但会带来较大的设备阻力。

混合基础隔震体系优化设计及性能

为解决基础隔震结构中隔震层位移需求过大的问题,提出了一种基础隔震结构(Base Isolated Structure,BIS)+串并联调谐质量阻尼器惯容器(Tuned Tandem Mass Damper-Inerter, TTMDI)的混合隔震体系。采用Bouc-Wen滞回模型模拟隔震层的非线性力-变形行为,基于随机等效线性化和模式搜索优化算法并考虑地震动模型,在频域内建立了BIS+TTMDI体系的优化设计框架。分别从鲁棒性、有效性、刚度和阻尼系数、冲程及对地震频率敏感性方面对BIS+TTMDI体系的性能进行评估,并与BIS+调谐质量阻尼器(Tuned Mass Damper, TMD)、串并联调谐质量阻尼器(TunedTandemMassDamper,TTMD)和调谐质量阻尼器惯容器(TunedMass Damper-Inerter, TMDI)进行比较。通过对近场地震动下某七层混合基础隔震结构(包括BIS+TTMDI和BIS+TMDI体系)的动力弹塑性分析,评价了其减/隔震性能。结果表明:BIS+TTMDI体系具有最好的减/隔震性能和强鲁棒性;而且在BIS+TTMDI体系中TTMDI的总阻尼需求不到BIS+TMDI体系中TMDI的一半,因而更为经济实用。

全模块化铝制天桥下部结构设计与力学分析

为了解决目前现存人行天桥桥墩设计过于保守,未能充分利用铝合金材料自重轻的优点,以及城市管网密集布设导致的城市地下结构施工困难等问题,结合钢材和混凝土2种材料的特性,采用钢材降低桥墩材料用量,并采用灌浆套筒、预埋件和螺栓锚固的连接方式,提出一种具有轻量化、模块化、拼装简单的新型全模块化铝制天桥桥墩;通过与传统独柱式桥墩对比,分析结构的力学性能,对桥墩的承载力水平、基础对土体的影响范围等方面进行研究。有限元数值分析结果表明,新型结构的承载能力高于传统结构,在减少材料消耗的基础上保证了结构的可靠性;基础的数值模拟结果表明,微型群桩承台基础对土层的影响范围小于桩柱式基础,有利于减小施工时城市管网造成的施工困难。

成组立模成型机模板结构优化设计研究

混凝土预制构件成组立模成型机(简称成组立模)是一种新型的生产混凝土预制构件的设备。为了提高成组立模台面的振动效果和承载能力,本研究以成组立模模板结构为研究对象,提出了一种拓扑优化新兴设计与响应面法结合的优化设计理论。首先,基于变密度法对成组立模模板结构加强筋布局进行拓扑优化设计,得到了加强筋最佳的材料分布形式,以此对成组立模模板结构进行了结构优化设计。为得到最佳的加强筋设计参数,采用中心组合试验设计,建立模板结构最大位移、最大等效应力的响应面模型。利用多目标遗传算法对响应面模型进行优化求解,得出加强筋各参数最优的组合方案。有限元分析结果表明:与初始方案相比,优化设计方案提高了台面的刚度和强度,同时改善了模板结构的振动特性,并提高了混凝土预制构件的成型质量。该研究为进一步推进成组立模的研究提供了理论指导。

喷箱辊筒式胶合板生产连续热压机设计

根据胶合板生产的工艺要求,结合并借鉴辊筒式单板干燥机的结构,设计了一型专用于胶合板生产的、采用辊筒加压、喷箱加热的连续式热压机;说明了喷箱辊筒式连续热压机的结构组成与工作原理,设计计算了压机的分段尺寸、液压系统与辊筒驱动系统的工作参数及其年产能;利用ANSYS Fluent软件,对喷箱喷孔的热气流流速均匀性、胶合板坯的加热均匀性进行了数值分析;设计与分析结果表明,该压机在结构设计上能够满足胶合板的生产需求,可以为胶合板连续热压机的开发提供借鉴。

不同结构参数对高速开关阀液压力的影响研究

因其具有价格低廉、抗污染性强等优点,高速开关阀已被广泛运用到各种车辆的制动系统中,其动态性能直接影响到车辆的制动效果,而阀芯所受的液压力是决定高速开关阀动态特性优劣的关键参数。针对不同参数对高速开关阀液压力的影响,以及实际工程中阀芯液压力难以测量的问题,采用计算流体动力学(CFD)对高速开关阀进行了数值模拟。首先,基于有限体积法(FVM),建立了不同开度、压差、温度、以及结构参数(阀座节流孔直径和锥角)的三维仿真模型;然后,对比不同网格数量的仿真结果,排除了网格数量对于仿真结果的影响,并详细分析了各参数对液压力的影响,得出了高速开关阀液压力与各参数之间的变化规律;最后,采用响应面分析结合遗传算法对开关阀的结构参数进行了优化。研究结果表明:随着阀芯开度的增加,节流区域发生了转变;较大的压差会导致液压力产生较大幅度的变化;相较于高温,低温对液压力有着更加显著的影响;对结构参数进行优化后,最小开度的液压力提高了49.2%,提高了阀控制稳定性,为高速开关阀线性控制设计提供了理论基础。

考虑SSI效应时TMD的减震优化设计

土-结构相互作用(SSI)效应可能会对地震作用下调谐质量阻尼器(TMD)的有效性产生重要影响,因此本文研究了考虑SSI效应时TMD对高层建筑的抗震控制性能。针对一个质量分布均匀、层刚度随高度呈线性分布的40层benchmark结构,以结构顶层均方根位移最小为优化目标,采用改进粒子群算法对其在不同地基土条件以及地震波激励下的调谐质量阻尼器参数进行优化设计。优化结果表明,忽略SSI效应可能会造成地震激励下高层结构中TMD减震性能的不恰当估计,TMD的优化参数与地基土类型和地震波种类紧密相关。优化后的TMD可以有效降低结构顶层位移响应且不增加其峰值加速度,优化后的TMD耗散了绝大部分地震输入能量,并大大降低了结构能量。

Design parameter optimization method for a prestressed steel structure driven by multi-factor coupling

To achieve efficient structural design,it is crucial to reduce the cost of materials while ensuring structural safety.This study proposes an optimization method for design parameters(DPs)in a prestressed steel structure driven by multi-factor coupling.To accomplish this,a numerical proxy model of prestressed steel structures is established with integration of DPs and mechanical parameters(MPs).A data association-parameter analysis-optimization selection system is established.A correlation between DPs and MPs is established using a back propagation(BP)neural network.This correlation provides samples for parameter analysis and optimization selection.MPs are used to characterize the safety of the structure.Based on the safety grade analysis,the key DPs that affect the mechanical properties of the structure are obtained.A mapping function is created to match the MPs and the key DPs.The optimal structural DPs are obtained by setting structural materials as the optimization objective and safety energy as the constraint condition.The theoretical model is applied to an 80-m-span gymnasium and verified with a scale test physical model.The MPs obtained using the proposed method are in good agreement with the experimental results.Compared with the traditional design method,the design cycle can be shortened by more than 90%.Driven by the optimal selection method,a saving of more than 20% can be achieved through reduction of structural material quantities.Moreover,the cross-sectional dimensions of radial cables have a substantial influence on vertical displacement.The initial tension and cross-sectional size of the upper radial cable exhibit the most pronounced impact on the stress distribution in that cable.The initial tension and cross-sectional size of the lower radial cable hold the greatest sway over the stress distribution in that cable.

膨胀节水压测试装备左梁结构优化设计

为了实现某水压测试装备左梁结构轻质化、高强度的优化设计目标,应用ANSYS Workbench的多目标驱动优化工具结合多目标遗传算法对左梁结构尺寸进行优化,应用ANSYS Workbench的拓扑优化工具对左梁结构形状进行优化。多目标驱动优化和拓扑优化相结合的优化方法,使左梁结构质量减少了23.24%,达到了优化目标,为水压测试装备结构优化设计提供了思路和参考。

钢-UHPC组合梁桥负弯矩作用下的设计优化

负弯矩区开裂是钢混组合梁桥的主要技术难题,利用钢-超高性能混凝土(UHPC)可以显著改善甚至规避钢混组合梁桥负弯矩区的开裂问题。本文基于钢-UHPC组合梁数值分析,研究了不同设计参数对钢-UHPC组合梁桥在负弯矩作用下的极限承载能力和开裂弯矩的影响。研究结果表明,采用一定厚度的UHPC和普通混凝土组合的方式可以显著改善结构的抗裂性能,而增加UHPC强度等级、厚度尺寸以及栓钉的直径对于刚度和极限抗弯承载能力并没有显著影响。这些结果可以为钢-UHPC组合梁桥的设计提供优化参考。

内撑式地铁基坑支护结构优化设计影响因素分析

文章以苏州地铁4号线某车站基坑围护工程为例,建立数值模型,分析了内撑式基坑支护结构体系中支撑竖向布置、水平间距、刚度、支护桩径等关键设计参数对支护体系内力、变形以及地表位移的影响规律。结果表明:中间支撑的布置接近坑底有利于基坑变形控制,支撑水平间距以适合施工的4 m为宜;支撑刚度越大,支撑轴力差异越明显;支护桩直径0.8~1.0 m能使地表竖向位移得到较好控制。基于研究结果,提出了相应的支护体系优化调整方案,在满足安全性要求下,可通过对设计参数的适当调整使地铁基坑工程的设计更加经济合理。