THE TOPOLOGICAL OPTIMIZATION FOR TRUSS STRUCTURES WITH STRESS CONSTRAINTS BASED ON THE EXIST-NULL COMBINED MODEL

A new exist-null combined model is proposed for the structural topology optimization. The model is applied to the topology optimization of the truss with stress constraints. Satisfactory computational result can be obtained with more rapid and more stable convergence as compared with the cross-sectional optimization. This work also shows that the presence of independent and continuous topological variable motivates the research of structural topology optimization.

Optimization and Characterization of Combined Degumming Process of Typha angustata L. Stem Fibers

Plant derived natural fibers have been widely investigated as alternatives to synthetic fibers in reinforcing polymers.Researchers over the years have explored many plant fibers using different extraction processes to study their physical,chemical,and mechanical properties.In this context,the present study relates to the extraction,characterization,and optimization of Typha angustata L.stem fibers.For this purpose,desirability functions and response surface methodology were applied to simultaneously optimize the diameter(D),linear density(LD);yield(Y),lignin fraction(L),and tenacity(T)of Typha stem fibers.Typha stems have been subjected to both alkali(NaOH)and enzymatic(pectinex ultra-SPL)treatments.Three levels of process variables including enzyme concentration(10,15,and 20 ml/L)and treatment duration(10,15,and 20 days)were used to design the experiments according to the factorial design.Experimental results were examined by analysis of variance and fitted to second order polynomial model using multiple regression analysis.The Derringer’s desirability function released that the values of process variables generating optimized diameter,linear density,yield,lignin ratio and tenacity are 20 ml/L and 20 days for concentration of pectinex ultra-SPL enzyme and treatment duration,respectively.Confirmation was performed and high degree of correlation was found between the experimental and statistical values.Moreover,the morphological structure has been investigated by the scanning electron microscope,showing a crenelated structure of ultimate fiber bundles of cellulose composing the Typha fiber.Compared to Typha stem non-treated fibers(TSNTF),Typha stem combined treated fibers(TSCTF),brings to improve mechanical properties.This change in mechanical properties is affected by modifying the fiber structure showing alpha cellulose of(66.86%)and lignin ratio of(10.83%)with a crystallinity index of(58.47%).

Optimization of energy consumption structure based on carbon emission reduction target:A case study in Shandong Province,China

It is urgent to significantly reduce greenhouse gas emissions to actively deal with global warming.This paper investigates Shandong Province,a typical province of energy consumption,as the research object,aiming to optimize total energy consumption and consumption structure in the future planning year.This paper constructs a methodological system to optimize energy consumption structure in Shandong Province,using a scenario combination of system dynamics(SD)prediction and analysis based on the coupling of key scenario elements affecting different energy consumption from different perspectives.Structural equation modeling and SD sensitivity analysis indicate an overlap between key factors restricting energy consumption.Pairing the key scenario factors can better reflect the internal mechanism of energy consumption development.Based on this,21 scenarios based on different combinations of the key elements are constructed.Through SD prediction and analysis,the most suitable scenario mode for optimizing energy consumption structure in Shandong Province is selected.This paper provides a suitable development range for the average gross domestic product growth rate,the proportion of secondary industry,energy consumption intensity of secondary industry,and the urbanization rate for Shandong Province.This paper can provide a reference for similar research and the government in formulating the optimization scheme of energy consumption structure.

CFD studies on the separation performance of a new combined gas–solid separator used in TMSR-SF

In order to comply with discharge standards, a gas–solid separator is used to remove solid particles from the thorium molten salt reactor-solid fuel (TMSR-SF) system. As a key component, it directly determines system energy efficiency. However, current gas–solid separators, based on activated carbon adsorption technology, result in high pressure drops and increased maintenance costs. In the present study, a new combined gas–solid separator was developed for the TMSR-SF. Based on a simplified computational fluid dynamics (CFD) model, the gas–solid twophase flow and the motion trajectory of solid particles were simulated for this new separator using commercial ANSYS 16.0 software. The flow and separation mechanism for this structure were also been discussed in terms of their velocity effects and pressure field distributions, and then the structure was optimized based on the influence of key structural parameters on pressure and separation efficiency. The results showed that the standard k–ε model could be achieved and accurately simulated the new combined separator. In this new combined gas–solid separator, coarse particles are separated in the first stage using rotating centrifugal motion, and then fine particles are filtered in the second stage, giving a separation efficiency of up to 96.11%. The optimum blade inclination angle and numbers were calculated to be 45° and four, respectively. It implicated that the combined separator could be of great significance in a wide variety of applications.

Efficient Combination of Topology and Parameter Optimization

This paper presents a combination method of Particle Swarm Optimization (PSO) and topology optimization. With this method a better result can be achieved compared with the sequential application of these two optimization methods. It inherits the ability in finding global optimum from PSO and also suits for discretized design domain. Some special schemes are used in order to provide higher computation efficiency. This method has only been tested with a convex optimization problem. The application in case of a concave problem will be a future study.

联合收获机发动机风冷系统优化设计

为了减少联合收获机收获过程中水箱“开锅”现象的发生,延长收获机的无故障工作时长,对4LXZ-8F型联合收获机的发动机风冷系统散热量进行了计算,并基于计算结果对防尘罩、散热器进行了优化设计,对冷却风扇进行了匹配选型。利用SolidWorks对优化前后风冷系统进行了三维建模,利用Fluent软件对发动机风冷系统优化前和优化后散热器散热性能分别进行仿真分析。仿真结果表明:优化前的冷却水入口温度为90℃,出口温度为72.3℃,进出口温差为17.7℃;优化后的冷却水入口温度为90℃,出口温度为71.1℃,进出口温差为18.9℃,表明优化后散热器散热性能提升了6.78%。研究成果可为提高发动机风冷系统的散热性能,延长无故障收获时长提供理论指导。

基于传递矩阵的管路-壳体耦合系统动力学建模

针对管路-支撑-壳体耦合系统的振动响应快速预报和传递特性分析,采用Riccati传递矩阵法建立直管-弯管-变径管-泵-阀门复杂组合管路的动力学模型,以获取考虑流固耦合效应时组合管路的频响特性;采用频响函数子结构综合方法建立组合管路-支撑-壳体耦合系统的动力学模型,以获得在管路系统泵源模拟激励下的振动传递特性。对耦合系统的位移频响、传递特性开展分析,得到如下结论:对组合管路利用Riccati变换可解决传递矩阵法多管段数值精度累积误差的问题,在垂向简谐力激励下壳体和管路受到的垂向力大于轴向力和横向力,在各个支撑处通过各个方向传递的功率流量级基本一致。

基于ANSYS Workbench的联合收获机滚筒轴疲劳强度分析与优化

切纵轴流谷物联合收获机脱粒能力强、工作效率高,是未来收获行业的发展趋势。联合收获机在作业的过程中由于喂入量不稳定、物料层不均匀使得切流脱粒滚筒所受的交变载荷冲击较大,造成滚筒轴断裂。采用ANSYS Workbench对滚筒轴进行静力学和疲劳强度分析,得到实际作业过程中导致滚筒轴断裂失效的原因为疲劳断裂,然后对轴的结构和材料进行改进,改进后的轴最大应力值减小至原来的40.6%左右,疲劳寿命循环次数有了极大的提高,有效保障了联合收获机长时间的安全作业。

一种新型转向架橡胶垫的开发与应用

橡胶垫在机车车辆一、二系悬挂系统上得到广泛应用,作用是绝缘、减振以及调整系统组合刚度,通过调整组合刚度能有效地改善机车车辆的动力学性能。文章首先从橡胶垫对一系悬挂装置系统组合刚度影响的角度出发,利用Abaqus软件建立了一系悬挂系统仿真模型,分析了不同结构的橡胶垫对系统组合刚度、橡胶垫应力和应变的影响;其次模拟橡胶垫实际运用工况,搭建了一系悬挂系统的刚度试验台,对装有不同结构橡胶垫的一系悬挂垂向刚度进行了试验测试,并与计算结果进行了对比分析,结合仿真计算和试验验证结果,最后选取对调整系统组合刚度最优方案的橡胶垫进行了产品开发。该橡胶垫顺利通过了疲劳试验,并装用于某出口动车组上,效果良好、性能稳定,为后续橡胶垫的开发提供了参考依据。

基于TOPSIS-灰色关联法的负倒棱刃口几何参数优化

在重型切削中需优化刀具负倒棱结构,以提高刀具寿命,提出了TOPSIS与灰色关联相结合的刃口参数优化方法。基于层次分析法和熵权法构建组合权重,确定各评价指标的加权因子;通过TOPSIS法计算其Euclid距离,并根据灰色关联分析计算各备选方案到正、负理想解的灰色关联度,获得关于Euclid距离和灰色关联度的综合相对接近度;分析各参数各水平对排序结果的影响程度,确定最优的负倒棱刃口参数组合;通过优化刀具的有限元仿真分析,验证该方法对刀具刃口优化设计的有效性。

基于双向渐进结构优化算法的预制拼装箱梁剪力键设计研究

为研究单项和多项荷载组合作用下节段预制拼装箱梁接缝处剪力键受力状况,以郑州南四环全预制装配高架桥为背景,采用Abaqus软件和双向渐进结构优化(BESO)算法,建立典型箱梁节段分析模型,研究剪力键在单位轴力、剪力、扭矩、弯矩和不同荷载组合作用下的布置规律。结果表明:轴力作用时剪力键应布置于顶板;剪力作用时剪力键应布置于腹板和底板;扭矩作用时剪力键应布置在顶板、腹板交接处和腹板外侧;横桥向弯矩作用时剪力键应布置于顶板、腹板下侧和底板;竖向弯矩作用时,剪力键应布置于顶板翼缘。轴剪组合作用下,当剪力占比小于50%时,轴力对剪力键布置起控制作用;当剪力占比达95.24%时,剪力对剪力键布置起控制作用。弯剪组合作用下,当剪力占比超过4.76%时,剪力对剪力键布置起控制作用;当剪力占比小于0.50%时,横桥向弯矩对剪力键布置起控制作用。扭剪组合作用下,当剪力占比超过0.10%时,剪力对剪力键布置起控制作用。预制拼装箱梁剪力键布置受荷载类型及荷载组合影响显著,应考虑不同位置剪力键的实际受力状况进行设计。

带有预应力的连续体组合结构拓扑优化

考虑梁结构的预应力,导出了结构的应力及其灵敏度公式。同时,结合结构单元应力水平和相对差商,对于带有尺寸和拓扑变量的连续体组合结构优化问题,建立了一套优化准则,在双方向渐进结构优化方法思想的基础上,形成了一种新的拓扑优化算法。最后,算例表明了该方法的正确性和有效性。

微网多目标经济调度优化

为减少气体污染物的排放,微网节能减排发电调度成为一种必然趋势。提出考虑微源同时提供有功和无功出力并计及制热收益的热电联产型微网系统多目标经济调度模型,以一个包含风、光、储、微型燃气轮机、燃料电池以及热电负荷的具体微网为例,在研究模糊优化理论的基础上,采用最大模糊满意度法将多目标经济调度问题转化成非线性单目标优化问题,并运用改进遗传算法优化考虑实时电价的并网运行方式下各微源的有功、无功出力和多目标优化的满意度,对比分析单目标与多目标系统优化值。仿真算例表明,多目标模型比单目标模型更能确切反映微网的实际运行状态,能够以尽量小的运行成本实现较好的环境效益,验证了所提模型和算法的有效性。

大型风电机组组合式塔架结构优化设计

为解决传统单管风力发电塔架在大型风电机组应用中加工、制作、安装和运输成本大幅上升的问题,提出一种新型组合式塔架结构,并对其进行结构优化设计.该塔架上部为传统单管式塔架,下部为四角钢十字形组合截面塔柱的格构式塔架.通过对四角钢十字形组合截面的轴压极限承载力进行分析,得到组合截面的稳定系数曲线.基于粒子群算法,综合考虑应力、频率和长细比约束等因素,对下部格构式塔架的形状和杆件截面进行优化.分析结果表明,组合式塔架结构可以解决传统单管式风力发电塔架的运输问题,且用钢量节省约34%.

分布式冷热电联供系统优化配置与适用性分析

为提高冷热电联供系统在不同负荷结构下的优化配置水平与综合运行效益,对计及蓄能装置的冷热电三联供系统的优化配置及运行进行了深入研究。基于以热定电、以电定热和多目标综合效益最优的3种运行模式,建立了综合考虑能源、经济和环境效益的多目标优化模型,利用遗传算法对系统设备容量和运行模式进行了优化。然后,分析了能源价格与引入蓄能装置对冷热电联供系统综合效益的影响。最后,基于某建筑负荷不同的冷电比和热电比对上述内容进行仿真分析,并以分供系统作为参照对象,给出了不同负荷结构下冷热电联供系统的最佳配置及最佳运行模式。优化结果表明,在大部分负荷结构下,冷热电联供系统采用多目标综合效益最优运行模式时各方面效益更好。

板壳加筋结构的组合优化

提出了一种将结构加筋布局优化和结构参数优化相结合的优化方法。该方法先对结构中的加强筋进行布局优化,然后再优化结构参数。在加筋布局优化中,用单元应变能密度灵敏度作为删除单元的准则。在参数优化中,目标函数和约束函数被近似地表示为二阶表达式,并用改进的DFP(Davidon,Fletcher and Powell)方法来求优化解。为了降低计算复杂度,采用组合近似(CA)方法对修改后的结构位移和应力进行重分析,并应用该方法对储水箱结构进行了结构优化设计。数值结果表明,该方法处理板壳加筋结构优化问题十分有效,而且容易在计算机上实现。

结构静态拓扑重分析的迭代组合近似方法

提出一种拓扑修改的静态重分析的迭代组合近似方法.这种方法基本上是两步法。首先,将新增加的自由度通过Guyan缩减方法凝聚到原始自由度上,形成凝聚方程.其次,用迭代组合近似方法求出原始自由度的近似位移,从而求出原结构自由度的位移.新增加自由度的位移可以通过恢复得到。通过板结构的加筋布局优化设计的数值例子表明,该方法对拓扑修改较大时仍可得到满意的结果。

基于遗传算法和梯度算法的一种结构优化混合方法

基于遗传算法和梯度算法,文章提出了一种结构优化的混合方法。算例表明该方法兼具遗传算法的优良全局搜索能力和梯度算法的强大局部搜索的特点,且具有很好的工程适应性。

UUV耐压结构多目标优化设计

UUV(unmanned underwater vehicle,无人水下航行器)在海洋民用与军事领域具有广阔的应用前景。UUV耐压结构作为影响UUV负载能力及保障UUV航行任务安全高效执行的重要部件,其优化设计有重要意义。为了最大程度地实现减重目标,有效平衡耐压结构质量、结构强度和稳定性之间的矛盾,进而提升UUV综合性能,提出一种基于组合加权响应面法的多目标优化方法。通过试验设计得到初始采样点,利用有限元工具计算响应值并构建代理模型;然后,以折衷规划法对子目标进行归一化处理,采用组合加权法设定子目标权重系数,以进行耐压结构的多目标优化设计。以某型UUV为例,利用所提方法对其梯形肋骨耐压结构进行多目标优化设计,优化后耐压结构质量减轻了6.6%,肋骨应力下降了6.7%,同时满足稳定性要求。在此基础上,分别以质量为优化目标和以质量、结构强度和稳定性为综合优化目标,对不同肋骨形式耐压结构进行优化设计。结果表明:梯形肋骨耐压结构的综合优化效果最佳。该研究方法适用于UUV耐压结构的多目标优化,研究结果可为UUV耐压结构优化设计提供理论指导,具有实际工程意义。

利用单元模态应变能法的地下框架结构损伤诊断

基于地下框架结构损伤前后动力特性的分析,证明了模态应变能变化对单元损伤的敏感性。选择单元模态应变能变化率作为人防结构损伤诊断的标识量,证明了多位置损伤状态下产生的单元模态应变能变化率是单位置损伤状态的叠加,并提出了应用组合优化求解结构多位置损伤诊断的方法。以一典型的人防工程为算例,通过对其在不同损伤情况下计算结果的分析和讨论,说明所提出方法是有效可行的,它不仅可以准确完成人防结构的损伤诊断,并且简化了损伤诊断过程。