碳纤维复合材料控制臂多尺度多目标优化

为实现悬架控制臂轻量化设计,采用碳纤维复合材料(CFRP)对钢制控制臂进行材料替换,并利用多层次优化方法对CFRP控制臂进行铺层优化。基于多尺度分析方法,考虑碳纤维复合材料细观结构参数及铺层角度对控制臂宏观性能的影响,选取细观尺度下纤维束截面高度、宽度、纱线曲折度、单位长度经纬纱数量及四个经典铺层角度作为设计变量,以控制臂的质量最小、一阶模态频率最高为优化目标,以刚度和强度为约束条件,结合响应面近似模型和NSGA-Ⅱ优化算法对碳纤维复合材料控制臂进行多尺度多目标优化,得到Pareto解集。优化结果表明,在刚度满足使用性能要求下,CFRP控制臂的质量较钢制控制臂下降了65%,且强度、振动特性等性能得到大幅提升,轻量化效果显著,可为碳纤维复合材料结构件的轻量化设计提供参考。     

基于铺层设计特征的碳纤维增强复合材料悬架控制臂结构优化

基于铺层设计特征,提出一种使用碳纤维复合材料对承载结构件进行结构优化设计的方法和流程.该方法综合考虑结构几何特征、材料铺层方式、铺层厚度及铺层角度在设计环节中的序列关系,通过几何设计空间构建、离散变量多目标优化、基于工艺可行性的最优决策等方法实现结构设计.以碳纤维增强复合材料悬架控制臂的轻量化设计为例:首先,以钢质控制臂结构为参考建立复合材料控制臂的几何设计空间;然后,以复合材料铺层便利性为原则对其进行结构设计,采用准各向同性铺层对控制臂的铺层厚度进行设计;进而,以提高控制臂刚度和1阶固有频率为目标,使用优化算法对铺层角度进行多目标优化设计;最后,以工艺可行性为约束对优化结果进行筛选并最终完成结构设计.结果表明,所设计复合材料结构具有更大的刚度和1阶固有频率,并且与钢质结构相比减重47.9%.所提出的方法能够较好地兼顾结构特征和复合材料设计要求之间的关系,为复合材料结构优化设计理论与方法的发展提供有益参考.     

车用CFRP油底壳的结构与制造工艺并行优化设计

为实现碳纤维增强复合材料（carbon fiber reinforced polymer,CFRP）油底壳的替代与制造,结合复合材料铺层可制造性分析软件FiberSim与铺层结构优化模块Optistruct,对CFRP油底壳开展了结构与制造工艺并行优化设计。参照CFRP壳体类零件的成型过程,采用FiberSim软件制定了满足制造工艺要求的CFRP油底壳铺覆方案。并在此基础上,分别以CFRP油底壳刚度最大、质量最小为优化目标,以振动模态、制造工艺要求为约束,采用Optistruct模块对CFRP油底壳的铺层结构进行优化设计。经仿真分析验证,制造工艺调整后的CFRP油底壳满足各项替代要求,且CFRP油底壳的质量较原金属油底壳减小了56.7%。所提出的结构与制造工艺并行优化设计方法可较好地兼顾结构特征、复合材料设计及制造工艺要求,为复合材料产品的优化设计提供了参考。     

基于遗传算法的碳纤维增强树脂复合材料层合板单搭胶接结构的多目标优化

基于遗传算法对碳纤维增强树脂复合材料(CFRP)层合板单搭胶接结构进行了多目标优化,以提高其结构性能.首先,通过三维Hashin准则和三角形内聚力模型建立三维有限元模型来预测CFRP层内损伤过程、层间失效和胶层损伤过程,并通过试验验证其有效性.其次,利用拉丁超立方抽样(LHS)方法和二次多项式响应面法(RSM),基于搭...     

3-URPR并联机构的逆运动学与可达工作空间分析

目的 通过对推动臂结构尺寸进行优化设计,得到在提高推动臂工作性能和力学性能的前提下减小质量的最优方案。方法 以推动臂的质量为优化目标,以推动臂受到的压力大小为约束条件,以推动臂的结构尺寸为优化设计参数,建立优化的数学模型。应用Workbench的多目标驱动优化工具结合多目标遗传算法的理论对推动臂的结构尺寸进行优化设计。结果 通过优化分析,结果表明,优化后模型的等效应力极大值减少了23.08%,结构总质量减少了7.42%。结论 通过对不同结构尺寸在其约束条件下的研究分析,达到了最优结构尺寸下推动臂工作性能和力学性能更优、部件总质量更小的目的,为以后粘箱机的结构优化设计提供了思路和参考。     

考虑制造因素的变刚度层合板的抗屈曲铺层优化设计

与常规层合板相比,变刚度层合板的制造、有限元建模分析和铺层设计有其特殊之处。首先对设计时需考虑的制造因素进行了归纳,提出了变刚度层合板的铺层设计要求。然后给出了变刚度层合板的理想模型和考虑丝束宽度模型的建模方法。基于理想模型对ABAQUS的前处理模块进行二次开发,利用编制的参数化建模程序分析了不同铺放角的变刚度层合板的屈曲性能,并讨论了最小曲率半径对铺层的限制和变刚度设计提高屈曲载荷的机制。基于变刚度层合板的抗屈曲机制建立了一种铺层优化设计方法,使用遗传算法经两步优化得到最优铺层。对最优铺层建立考虑丝束宽度的模型以研究丝束宽度和铺层偏移对变刚度层合板抗屈曲铺层优化结果的影响。研究表明,在变刚度层合板的抗屈曲铺层优化中使用简化的理想模型通常来说是可行的。在考虑制造因素的情况下,优化后的变刚度层合板较常规层合板屈曲载荷有显著提高。     

轴心受压CFRP—铝合金组合管弹塑性屈曲性能分析

CFRP管具有轻质高强的特点,适合于建造大跨度空间网格结构,但其破坏呈脆性,且以节点连接破坏为主,不能充分发挥CFRP材料的优点,为此建议将CFRP与铝合金组合形成CFRP-铝合金组合管来改善其受力性能和构件连接性能。首先对CFRP-铝合金组合长管进行了轴心受压稳定试验研究,得到其基本受力性能与破坏模式。利用有限元方法对组合管的特征值屈曲进行分析,研究不同CFRP铺层角度、厚度和顺序的影响。根据特征值屈曲的分析结果,引入初始几何缺陷,对组合管进行了弹塑性屈曲分析,并将分析结果与试验结果进行了对比,确定了有限元分析模型的合理性,进一步研究了不同长细比、铺层角度和厚度对组合管弹塑性稳定性能的影响机理。最后基于试验结果与数值分析结果,通过修正Perry稳定计算公式,得到了CFRP-铝合金组合长管屈曲荷载的计算公式。     

硅片机器人大臂结构多目标拓扑优化设计

目的为了改善硅片机器人结构的静、动力学性能,实现结构的轻量化设计。方法引入多目标优化理论,并结合层次分析法,实现硅片机器人大臂的结构优化设计。依据设计方案分析大臂的受力情况,采用固体各向同性材料惩罚模型分别构建多目标优化数值模型,并运用优化准则法进行优化求解。引入数理统计中的层次分析法确定各子目标函数的权重比,依据折衷规划组合方法构造关于静刚度和一阶固有频率的总目标函数。结果优化结果可知,大臂的柔度从26.890 mm/N降到13.221 mm/N,一阶固有频率从556.86 Hz增加到629.90 Hz,结构质量从1.48 kg减少到0.583 kg。结论多目标优化结果表明,基于多目标优化理论对硅片机器人大臂结构的改进设计,不仅有效地提高了其静刚度特性,一阶固有频率的提高说明大臂结构能抑制振动能力的提升,还实现了大臂结构轻量化设计。层次分析法的引入为多目标优化问题中各子目标函数的重要性提供了客观的理论依据。     

引力波探测望远镜超低热变形桁架支撑结构设计技术

本文针对引力波探测望远镜超低热变形要求,提出了通过设计CFRP铺层改变材料热胀系数的方法,进而解决桁架支撑结构热变形问题。同时针对望远镜装调性能的要求,给出了结构的分段式设计方案。文章首先分析了CFRP的优势、现有的消热化的方式和国内外研究进展,确定了以CFRP为关键材料的三杆式望远镜的方案,并提出了设计指标。其次建立了“材料-热变形、桁架结构-热变形”数学模型,针对材料铺层和结构设计进行优化,给出了优化方案。然后将CFRP材料应用于支撑结构中,采用分段式主支撑结构设计方案,降低了结构加工装调的难度,最后对整体结构进行分析。分析结果表明：机械性能方面,结构基频和最大重力卸载变形满足主支撑结构的要求;热变形方面,基于CFRP铺层特定优化设计的结构方案热变形为普通铺层方案的27.15%、Invar材料支杆方案的6.42%、SiC支杆方案的11.50%和钛合金支杆方案的3.21%,即优化设计可显著降低结构热变形。     

碳纤维增强树脂复合材料和铝合金温热自冲铆接工艺及接头力学性能

为研究传统自冲铆(SPR)工艺连接碳纤维增强树脂复合材料(CFRP)和铝合金的损伤问题,制备三种典型铺层结构的自冲铆接头,研究铺层结构对接头表面宏观损伤形貌的影响。在不同测试温度下对CFRP进行力学试验,研究温度对CFRP力学性能及失效的影响。基于CFRP的温热力学性能,以减小接头损伤为目的,创新性提出了CFRP和铝合金的温热自冲铆接(WSPR)工艺,对比了两种铆接工艺获得接头中CFRP的损伤差异。制备CFRP和铝合金的WSPR接头,研究铺层角度对接头力学性能和失效过程的影响。研究表明:常温下铆接时,钉头附近区域易出现宏观裂纹缺陷,主要以平行于纤维方向的基体裂纹和垂直于纤维方向的纤维裂纹形式存在。在树脂基体的玻璃化转变温度下,CFRP在横向和剪切方向的延展性大幅度提高,导致WSPR接头的CFRP表面无宏观裂纹,同时减小了分层损伤面积。铺层角度影响接头的拉剪力学性能及失效过程,[0/90/0]_s铺层接头的力学性能最优。      

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.