Compact Car-Body Surface Design with T-spline Surface

Creating proper B-spline surface models is a very challenging task for designers in car-body surface design.Due to the tensor-product structure of B-spline surface,some undesirable issues of the redundant control points addition,incomplete surface definition and the difficulty of trimming boundary alteration frequently occur,when designing the car-body surface with B-spline surfaces in local-feature-lines construction,full-boundary-merging and visual surface trimming.A more efficient approach is proposed to design the car-body surface by replacing B-spline surface with classical T-spline surface.With the local refinability and multilateral definition offered by Tspline surface,those designing issues related with B-spline surface can be overcomed.Finally,modeling examples of the door,hood and rear-window are given to demonstrate the advantage of T-spline surface over B-spline surface in car-body surface design.

Global Continuity Adjustment and Local Shape Optimization Technique for Complex Trimmed Surface Model

Smoothly stitching multiple surfaces mainly represented by B-spline or NURBS together is an extremely important issue in complex surfaces modeling and reverse engineering. In recent years, a lot of progress has been made in smooth join of non-trimmed surface patches, while there has been seldom research on smoothly stitching trimmed surface patches together. This paper studies the problem of global continuity adjustment, damaged hole repair and local shape optimization for complex trimmed surface model, and presents a uniform scheme to deal with continuity adjustment of trimmed surfaces and geometric repair of local broken region. Constrained B-spline surface refitting technique and trim calculation are first utilized to achieve global G^1 continuity, and then local shape optimization functional is adopted to reduce fitting error and improve local quality of refitted surface patch. The proposed approach is applied to a discontinuity ship hull surface model with an irregular hole, and the result demonstrates the validation of our method. Furthermore, on the premise of global continuity, the proposed locally repairing damaged surface model provides a better foundation for following research work, such as topology recovery technique for complex surface model after geometric repair.

Exact mesh shape design of large cable-network antenna reflectors with flexible ring truss supports

An exact-designed mesh shape with favorable surface accuracy is of practical significance to the performance of large cable-network antenna reflectors. In this study, a novel design approach that could guide the generation of exact spatial parabolic mesh configurations of such reflector was proposed. By incorporating the traditional force density method with the standard finite element method, this proposed approach had taken the deformation effects of flexible ring truss supports into consideration, and searched for the desired mesh shapes that can satisfy the requirement that all the free nodes are exactly located on the objective paraboloid. Compared with the conventional design method,a remarkable improvement of surface accuracy in the obtained mesh shapes had been demonstrated by numerical examples. The present work would provide a helpful technical reference for the mesh shape design of such cable-network antenna reflector in engineering practice.

Novel Annulus-shaped Flexure Pivot in Rotation Application and Dimensionless Design

Large-deflection flexure pivot is widely used in high precision rotation application, but there are less flexure configurations and simple and convenient design methods, This paper presents a novel large-deflection curved-compliant annulus-shaped flexure pivot composed of six curved beam flexure elements. It can offer more than lO^angular stroke theoretically. Firstly, main-motion pseudo-rigid-body method is introduced to establish the flexure pivot model. Although pseudo-rigid-body method can be used to analyze the large-deformation flexure pivot performance, the method is definitely a laborious and difficult task for designing this novel flexure pivot. In order to simply the designing process, dimension-design graphs based on the parametric models and finite element analysis is presented. Using the dimension-design method as a tool, the designers can determine the optimal geometry rapidly, based on the stiffness and rotation demands of an annulus-shaped flexure pivot. Finally, dimension-design graph examples are given whose primary design aims to achieve a rotation stroke of annulus-shaped flexure pivot. The finite element analysis results show that the relative designing error between anticipative rotation stroke and graph design result is less than 4%. The dimensionless method used in designing annulus-shaped flexure pivot can reduce design process in both time and complexity. The novel annulus-shaped flexure pivot and dimension-design method are helpful supplement to configuration and design method of large-deflection flexure pivot.

Combined Size and Shape Optimization of Structures with DOE,RSM and GA

In this paper,size and shape optimization problem of a machine gun system is addressed with an efficient hybrid method,in which a novel and flexible mesh morphing technique is employed to achieve fast parameterization and modification of complexity structure without going back to CAD for reconstruction of geometric models or to finite element analysis（ FEA） for remodeling. Design of experiments（ DOE） and response surface method（ RSM） are applied to approximate the constitutive parameters of a machine gun system based on experimental tests. Further FEA,secondary development technique and genetic algorithm（ GA） are introduced to find all the optimal solutions in one go and the optimal design of the demonstrated machine gun system is obtained. Results of the rigid-flexible coupling dynamic analysis and exterior ballistics calculation validate the proposed methodology,which is relatively time-saving,reliable and has the potential to solve similar problems.

基于Geomagic Design X组合体的逆向建模

Geomagic Design X软件常用于STL面片的逆向建模,选取一典型组合体对其逆向建模,通过对组合体对齐、分割领域、创建面片草图、创建实体和扫掠完成实体建模,最后验证体偏差检测是否符合要求,为后续相似零件的逆向建模提供参考。

ThinkDesign在汽车模具设计上的应用

通过两个实例,介绍了ThinkDesign的GSM(全局形状建模)技术在汽车模具型面设计与修改上的应用。

Surface area-volume ratios in insects

Body mass, volume and surface area are important for many aspects of the physiology and performance of species. Whereas body mass scaling received a lot of attention in the literature, surface areas of animals have not been measured explicitly in this context. We quantified surface area-volume （SA/V） ratios for the first time using 3D surface models based on a structured light scanning method for 126 species of pollinating insects from 4 orders （Diptera, Hymenoptera, Lepidoptera, and Coleoptera）. Water loss of 67 species was measured gravimetrically at very dry conditions for 2 h at 15 and 30 ℃ to demonstrate the applicability of the new 3D surface measurements and relevance for predicting the performance of insects. Quantified SA/V ratios significantly explained the variation in water loss across species, both directly or after accounting for isometric scaling （residuals of the SA/V - mass2/3 relationship）. Small insects with a proportionally larger surface area had the highest water loss rates. Surface scans of insects to quantify allometric SA/Vratios thus provide a promising method to predict physiological responses, improving the potential of body mass isometry alone that assume geometric similarity.

Optimization of the head shape of the CRH3 high speed train

Aiming at optimizing the head shape of the CRH3 high speed train, an efficient optimization approach is proposed. The CFD analysis by solving Navier-Stokes equations is coupled with optimization calculation based on the multi-objective genetic algorithm, meanwhile the arbitrary shape deformation technique (ASD) is also introduced into the design flow, which greatly shortens the time consumption for geometry regeneration and flow field remeshing. As a result, the efficiency of the optimization calculation is highly improved. Statistical analysis is done to the designs in the design space, and the correlation between the design variables and the objective is studied to find out the key variables that most affect the objective. Response surface analysis is also performed to get the nonlinear relationship between the key design variables and the objective with the Kriging algorithm. Finally, after the optimization, an aerodynamic performance comparison between the optimal shape and the original shape reveals that the original shape of CRH3 high speed train owns a very stable aerodynamic performance and can be trustingly used in industry.

Ethnography of Women＇ s Perception of Their Workwear： Comparative Study between South Afi＇ica and Uganda

The study investigates women＇s perception of the workwear, and their awareness about how garment fit can affect one＇s body image. Drawing on the theory of practice, we propose an ethnographic account of women＇s perception of workwear and their preferred alternative. The study presents a comparative perspective of attitudes, and perceptions about the workwear of women in South Africa and Uganda explored through the habitus. We present pro-vocal recollections of women perceptions on the current workwear ideal for men which omits women＇ body physique. In particular, from the current personal protective equipment （PPE）, we examine ＂the overall＂ common attire at site and an integral part of the PPE. Overalls are designed following the men＇s physique, and women in work place are subjected to put them on yet, differences in body structure/shapes amongst women, namely, hour glass, bottom hourglass, spoon, and pear shape, are hardly considered. The identification of different female body shapes is made possible through the 3D anthropometric measurements using a Three Dimensional （3D） Body Scanner （TC2）. We develop endogenous explanations of what women would want to see as workwear based on the understanding of women found on site in men＇s workwear or without any work weal- in South Africa and Uganda. Using ethnographic design approach, we capture voices of 10 women from South Africa and Uganda through participant observation and unstructured interviews. We analyze data thematically to determine the patterns of their responses toward an appropriate workwear. Moreover, we （re）construct these responses into possible design models that would be ideal workwear for women, which gives them the pride, respect, dignity, and confidence as women.

旗袍设计与人种体型特征关系研究

旗袍是我国传统服饰的典型代表之一,追溯旗袍的发展,在中国已有百年的历史,其也被视为东方服饰璀璨的明珠。如今,服装设计者们仍热衷于参与旗袍的改良设计。本文立足于旗袍以及黄种人的体型特征,探究旗袍与人种体型之间的关系,从旗袍的发展史分析女性思想的变化,根据3类人种起源的不同地理位置、气候因素、人种特点及时代审美等研究旗袍设计与人种体型特征之间的联系。

Analysis of Effect of Oblateness of Smaller Primary on the Evolution of Periodic Orbits

Evolution of periodic orbits in Sun-Mars and Sun-Earth systems are analyzed using Poincare surface of section technique and the effects of oblateness of smaller primary on these orbits are considered. It is observed that oblateness of smaller primary has substantial effect on period, orbit’s shape, size and their position in the phase space. Since these orbits can be used for the design of low energy transfer trajectories, so perturbations due to planetary oblateness has to be understood and should be taken care of during trajectory design. In this paper, detailed stability analysis of periodic orbit having three loops is given for A2 = 0.0001.

Analysis of Effect of Solar Radiation Pressure of Bigger Primary on the Evolution of Periodic Orbits

Evolution of periodic orbits in Sun-Mars and Sun-Earth systems are analyzed using Poincare surface of section technique and the effects of solar radiation pressure of bigger primary and actual oblateness of smaller primary on these orbits areconsidered. It is observed that solar radiation pressure of bigger primary has substantial effect on period, orbit’s shape, size and their position in the phase space. Since these orbits can be used for the design of low energy transfer trajectories, so perturbations due to solar radiation pressure has to be understood and should be taken care of during trajectory design. It is also verified that stability of such orbits are negligible so they can be used as transfer orbit. For each pair of solar radiation pressure q and Jacobi constant C we get two separatrices where stability of island becomes zero. In this paper, detailed stability analysis of periodic orbit having two loops is given when q = 0.9845.

基于H型翼梁的无人机整体尾段的设计与分析

针对某型无人机设计总体方案针对尾段结构提出的减重及降低综合成本的优化目标,本文基于复合材料“整体化”设计及翼身融合布局设计的新概念,设计了一种基于H型翼梁的将平尾、尾罩翼身融合一体的无人机整体尾段结构。在7 g过载、5°侧滑角两种飞行工况下对结构进行了有限元分析,结果显示整体尾部的强度安全系数高达1.5倍以上。研究结果表明,整体式尾段结构达成了结构减重30%、综合成本降低30%以上的设计指标,并具有结构简单、重量轻、载荷传递效率高等优势,满足了无人机轻量化结构设计的需求,并为类似结构的设计提供了可靠有效的参考。

螺旋曲面清水混凝土工程施工技术研究

当前,建筑领域的异形构件越来越多,形式各异。清水混凝土施工操作多依赖人工,机械化、标准化程度不高,不同的施工工艺带来的成型效果截然不同。文章以富阳科技馆工程为例,介绍了螺旋曲面清水混凝土工程施工技术的难点和施工方案的选择。利用BIM参数化设计同自动化下料设备的配合,确定异型背楞与双面板模板加固体系的施工工艺,以供参考。

超高压调节阀阀芯型面设计及流量特性验证

通过建立数学模型、公式推导和理论计算,获得了阀芯型面设计所需的流通面积、阀芯直径、夹角、母线长度等参数,并初步设计了线性流量特性阀芯形面;再利用模拟仿真的方法,对不同开度的流量系数进行验证,并反复修正阀芯形面,使各开度下的流量系数趋近于理论计算值;修正后的形面经过阀门流量特性试验验证,对比分析实际误差,在允许范围内可得最终的阀芯设计形面图,以确保阀门在实际运行时具有高精度的调节控制。此方法也可以推广应用到其他高端类调节阀的阀芯形面设计。

基于逆向工程的电话机身的模具设计的研究

通过对某型电话机身的逆向工程及模具设计,详细阐述了反求过程中的数据测量、曲线曲面重构及反求模型的模具设计,采用了一种将逆向工程与EMX系统相结合的设计方法。与传统的设计方法相比,该方法为新产品的开发提供了更方便、快捷的途径,能大大缩短产品模具设计和制造周期。

土壤粘附仿生研究(二) 典型土壤动物体表形态减粘脱土的初步研究

土壤动物的不粘土特性,对于地面机械减粘脱土的仿生研究具有重要意义。本文利用实体显微镜和扫描电镜对典型土壤动物穿山甲、蝼蛄、蚂蚁和蜣螂等的体表形态进行了观察研究。结果表明,上述土壤动物具有类似波纹状的体表结构,并用波形表面模型进行了减粘脱土的机理分析。

大客车车身骨架多学科协同优化设计

对某全承载大客车车身骨架结构进行包括轻量化、刚度、强度、振动模态和翻滚的多学科设计优化,以提高客车的综合性能。为克服客车翻滚分析的高度非线性带来的寻优困难,并解决结构有限元分析的低效问题,建立各学科的近似模型。首先建立大客车车身结构有限元模型,其中刚度、强度以及振动模态分析由Msc.Nastran完成,翻滚分析由显式动力学软件Ls-dyna完成。其次结合工艺要求和灵敏度分析结果,选择出各学科的设计变量,用优化的拉丁方方法完成试验设计。在此基础上,采用响应面方法建立各学科结构响应的近似模型。建立客车车身骨架结构的多学科优化模型,并用协同优化方法求解。结果显示,优化后的设计方案在轻量化、刚度、强度、模态振动和翻滚安全性方面均优于原设计方案。

风力机叶片外形设计及三维实体建模研究

基于贝茨理论,结合具体工程实际,对某中型风力机叶片进行外形设计。并在此基础上提出了风力机叶片的三维建模方法,即利用点的坐标变换理论来计算叶片各断面翼型的空间实际坐标,然后运用UG强大的三维曲面建模功能来建立叶片复杂曲面。该文提出的方法减少了风力机叶片等复杂曲面的建模工作量;叶片实体模型的建立也为叶片的气动性能计算和结构设计与分析奠定了基础。