通过UG二次开发实现产品模型重构

逆向工程是目前非常实用的一种新产品开发技术,而模型重构则是逆向工程中非常重要的内容,同时也是难点之一。将VC＋＋6．0与UG二次开发相结合,首先通过投影法获取不同截面轮廓数据,然后对各轮廓数据进行数据预处理并实现排序,再进行曲线拟舍得到截面轮廓曲线族,最后实现三维模型重构。实验结果表明可以获得有效的产品重构模型。     

基于图像的启发式三维火焰重建算法

研究了火焰的重建,为改进现有稀疏视角输入下的层析成像算法的重建精度,提出了一种基于图像的启发式火焰重建方法。该重建方法通过迭代优化求解能量约束模型,实现对火焰三维温度场的重建。算法允许复杂的成像模型应用于重建过程中,使渲染过程更接近火焰真实成像过程,并对数据平滑性进行约束,以提高重建结果质量。算法在迭代过程中使用启发式规则引导温度场数据调整,使算法快速收敛,并通过使用图形处理器加速重建过程。使用模拟数据和真实捕获数据进行实验,结果表明,与现有方法相比,提出的方法有效提高了重建结果的精度及平滑性,验证了提出方法的有效性。     

基于UG二次开发的数控产品特征面的自动加工方法研究

数控加工技术是一个国家制造业发展的标志。利用数控加工技术可以完成很多以前不能完成的曲面零件的加工,而且加工的准确性和精度都可以得到很好的保证。但是,数控加工过程会出现产品精度不可靠、效率低、劣质产品信息反馈不及时、成本高的现象。因此提出了一种基于UG二次开发的数控产品G代码自动生成方法,论述了数控产品的CAD模型借助UG二次开发,在NX软件加工模块下实现一键获取PMI信息与PMI的关联特征信息,根据特征关联信息与PMI信息对数控模型进行自动编写加工参数并生成G代码。     

基于Pro／E的人体特征尺寸提取

根据三维服装CAD系统对三维数字化人体尺寸特征信息的需要,提出了一种提取人体特征尺寸的新方法.该方法可根据人体扫描数据重构人体曲面模型,而后将模型导入Pro/E中,通过创建水平基准面与人体表面求交,找出人体主要特征尺寸如颈围、胸围、腰围、臀围所在的截面轮廓曲线特点,以此设定搜索这些特征截面轮廓曲线需满足的条件,利用Pro/E的测量分析和优化特征分析功能进行求解,从而获得满足设定条件的人体截面轮廓曲线所在的位置,最终计算截面轮廓曲线的长度以得到人体特征尺寸.该方法具有操作简便,易于掌握的特点.     

核心约束空腹式型钢混凝土柱恢复力模型研究

为了研究核心约束空腹式型钢混凝土(LSRCC)柱的恢复力模型,通过8个LSRCC柱试件的低周反复加载试验,获取了骨架曲线和滞回曲线,分析了其滞回特性;基于骨架曲线和滞回曲线特征,在弹塑性刚度、软化刚度和卸载刚度等模型特征参数的计算中,量化了型钢与螺旋箍筋的约束效应,建立了考虑型钢与螺旋箍筋复合约束作用的骨架曲线模型和恢复力模型。结果表明:核心约束空腹式型钢混凝土柱的滞回特性主要受轴压比、截面类型、螺旋箍筋配箍率和型钢间接配钢率的影响;所建议的三折线型骨架曲线模型与实测骨架曲线吻合较好,所建议的定点指向型恢复力模型与滞回曲线也较好的吻合,并且能反映不同轴压比和复合约束效应对滞回特性的影响,可为该结构的弹塑性地震反应分析提供参考。     

支持多学科协同设计的约束网络技术研究

针对多学科协同设计中约束条件过于复杂的情况,提出了一种基于约束网络协调模型的设计方法。该方法以约束网络协调模型管理所有领域的约束条件,以区间的形式描述设计参数、状态变量的不确定性信息,并利用区间算法实现了通用的一致性模型求解框架,具有求解代数方程、微分方程等形式约束的能力,从而可以建立跨领域的指标与设计变量间的双向联系。该方法现初步应用于某型转向架弹性元件参数的设计中。     

基于映射的拓扑优化最大尺寸控制方法

拓扑优化方法经过几十年的发展,已成功应用于机械工程、航空航天、电磁等领域的构型设计中。然而,由于制造工艺的限制,拓扑优化结果通常无法直接应用,需根据工艺要求进行修改,因此在拓扑优化模型中考虑制造约束成为重要的研究方向。其中,尺寸控制广泛存在于大部分制造工艺中,主要包括最小尺寸控制与最大尺寸控制。该文提出了一种基于映射的拓扑优化最大尺寸控制方法,构造了一种新的映射模型,对结构中不满足最大尺寸约束的中心单元密度进行惩罚,在不引入任何约束条件的情况下实现了对结构最大尺寸的控制。此外,该文将该方法中的惩罚转变为一个全局约束条件后与具有最小尺寸控制功能的拓扑优化鲁棒列式相结合,实现了对构件的最大最小尺寸协同控制。数值算例表明了该方法的有效性。     

基于跖跗围参数的鞋楦曲面重构

针对面向合脚性、舒适性的鞋楦个性化设计中的曲面重构问题,提出并实现了一种基于鞋楦跖跗围截面变换技术的鞋楦曲面参数化重构方法。通过对鞋楦跖跗截面围长和高度的控制,将跖、跗围的截面曲线变换到个性化设计所需求效果;基于三次样条插值函数构造局部、整体两类扩散函数,实现两种将两围截面变换效果扩散到整个鞋楦曲面的方式。此算法不仅可以准确地满足鞋楦围长约束要求,且保持了曲面光顺性。所提出的重构过程在Matlab平台上可以实现可视化交互设计,界面具有操作简单方便的特点。     

基于UG的渐开线型涡旋盘参数化建模设计

以渐开线型涡旋盘为例,研究其涡旋型线方程,利用UG参数化特征建模技术,将其转换为表达式方程,对基圆渐开线型涡旋盘进行三维造型。通过各参数之间的关联和约束,实现整体参数的自动更新,为渐开线型涡旋盘的参数化建模提供模型,为复杂曲线的设计和建模提供指导和借鉴,从而提高产品设计的效率,降低设计人员的劳动强度。     

UG集成环境下数控机床虚拟样机的实现

数控机床是一种重要的技术装备。为提高数控机床的设计水平和能力,在数控机床的设计开发过程中需要引入新的技术和设计手段。为把虚拟样机技术应用到数控机床设计开发的工程实践中,基于虚拟样机的概念讨论了数控机床虚拟样机的具体实现过程,分析比较了实现该过程的分布式软件平台和UG集成软件平台的特点。以数控铣床新产品开发为例,研究了UG集成环境下数控机床虚拟样机的构建与仿真过程,包括数字模型与装配、运动仿真、结构分析以及在虚拟样机上的加工仿真,给出了相应的示例。研究表明,应用UG的各功能模块可以有效地构建数控机床的虚拟样机并对其进行全面的仿真,使所设计的数控机床得到全面优化,为数控机床的开发设计提供了一种可行的先进方法。     

Structural optimization with an automatic mode identification method for tracking global vibration mode

This article presents a mode identification method for structural optimization with global mode constraints to overcome the mode switching problem. In engineering design, the natural frequencies of global vibrations for a complex structure, the orders of which would not be constant in optimization loops, are usually very difficult to constrain. In this case, an incorrect constraint may lead to an unreliable design. A mode identification technique based on modal effective mass fraction is implemented to track the global modes such that the constraints will be updated subsequently and the optimizer can run correctly. A study case with comparison to traditional modal assurance criterion approaches demonstrates the advantages of this technique. An optimization framework has been developed with the new proposed mathematical model. Two numerical optimization examples, of a space truss and a simplified satellite structure, are presented to demonstrate the feasibility and applicability of this process.     

Continuum structural topological optimizations with stress constraints based on an active constraint technique

Stress‐related problems have not been given the same attention as the minimum compliance topological optimization problem in the literature. Continuum structural topological optimization with stress constraints is of wide engineering application prospect, in which there still are many problems to solve, such as the stress concentration, an equivalent approximate optimization model and etc. A new and effective topological optimization method of continuum structures with the stress constraints and the objective function being the structural volume has been presented in this paper. To solve the stress concentration issue, an approximate stress gradient evaluation for any element is introduced, and a total aggregation normalized stress gradient constraint is constructed for the optimized structure under the r?th load case. To obtain stable convergent series solutions and enhance the control on the stress level, two p‐norm global stress constraint functions with different indexes are adopted, and some weighting p‐norm global stress constraint functions are introduced for any load case. And an equivalent topological optimization model with reduced stress constraints is constructed,being incorporated with the rational approximation for material properties, an active constraint technique, a trust region scheme, and an effective local stress approach like the qp approach to resolve the stress singularity phenomenon. Hence, a set of stress quadratic explicit approximations are constructed, based on stress sensitivities and the method of moving asymptotes. A set of algorithm for the one level optimization problem with artificial variables and many possible non‐active design variables is proposed by adopting an inequality constrained nonlinear programming method with simple trust regions, based on the primal‐dual theory, in which the non‐smooth expressions of the design variable solutions are reformulated as smoothing functions of the Lagrange multipliers by using a novel smoothing function. Finally, a two‐level optimization design scheme with active constraint technique, i.e. varied constraint limits, is proposed to deal with the aggregation constraints that always are of loose constraint (non active constraint) features in the conventional structural optimization method. A novel structural topological optimization method with stress constraints and its algorithm are formed, and examples are provided to demonstrate that the proposed method is feasible and very effective. © 2016 The Authors. International Journal for Numerical Methods in Engineering published by John Wiley & Sons Ltd.     

A level set–based method for stress-constrained multimaterial topology optimization of minimizing a global measure of stress

In multimaterial topology optimization of minimizing a global measure of stress, the maximum stresses in different materials may not satisfy the strength design requirements simultaneously if stress constraints for different materials are not considered. In this paper, a level set–based method is presented to handle the stress-constrained multimaterial topology optimization of minimizing a global stress measure. Specifically, a multimaterial level set model is adopted to describe the structural topology, and a stress interpolation scheme is introduced for stress evaluation. Then, a stress penalty-based topology optimization model is presented. Meanwhile, an adaptive adjusting scheme of the stress penalty factor is employed to improve the control of the local stress level. To solve the stress-constrained multimaterial topology optimization problem minimizing the global measure of stress, the parametric level set method is employed, and the sensitivity analysis is carried out. Numerical examples are provided to demonstrate the effectiveness of the presented method. Results indicate that multimaterial structures with optimized global stress can be gained, and stress constraints for different materials can be satisfied simultaneously.     

基于偏好与形状文法的电动汽车形态设计研究

目的 结合消费者偏好和对品牌识别的需求,分析电动汽车外形设计特征,提高用户满意度。方法 分析电动汽车的设计特征,引入原型范畴理论研究消费者偏好。将形状文法参数化,针对设计特征曲线的变化,基于原型偏好模型和品牌识别的要求制定修改性规则约束。提出偏好因子和品牌因子的概念,调节修改性规则的坐标点变化空间,利用交互式遗传算法构建计算机辅助设计系统。最后,利用计算流体动力学(CFD)分析方法,对车身形态的外部流场和表面压强进行分析,检验并优化车身造型,对设计结果进行满意度评价。结果 提出基于偏好与形状文法的电动汽车形态设计方法,通过对青年消费者的偏好调查分析,建立原型偏好模型。通过计算机辅助设计系统对原型偏好模型中的特征水平进行分析,求得分析结果的坐标值并对相关特征水平进行线形表达,建立理想低风阻体模型并进行具体样式优化。结论 以奥迪品牌的电动汽车设计为例,根据分析建立的理想低风阻体模型的模拟仿真分析结果较理想,对设计效果进行用户满意度对比评价,电动汽车外形设计的满意度有所提高,验证了该方法的可行性。     

Application of an iterative global approximation technique to structural optimizations

An iterative global approximation technique based on the Kriging method is proposed. The technique is validated through analytical test cases and then applied to solve two practical optimization problems: the optimization of aluminium-foam filled absorbers against crashworthiness requirements and the optimization of composite stiffened panels against buckling and strength constraints. The absorbers of the first application consist of two co-axial aluminium alloy tubes filled with lightweight aluminium foam. They were optimized to collapse at a controlled force level and to be the lightest possible. Explicit Finite element analyses were performed to evaluate the structural behavior of the absorbers in the sample points used to build the approximation. In the second application stiffened panels were optimized against buckling and strength constraints. The Tsai-Wu criterion was used to estimate first-ply failures as strength limit of the structure. Non-linear Riks analyses were performed with ABAQUS/Standard to evaluate the shell behavior in the sample points used to build the response surfaces. Basing on the obtained results the proposed iterative procedure seems a promising alternative to the classic a-priori building of response surface allowing better accuracy and saving of sample points.     

Multi-stage optimization method for air-intake system of hovercraft based on autonomous optimization

Abstract

In this study, an optimal structural design program was designed and developed for Computational Fluid Dynamics based on self-optimization, effectively reducing the time required for structural optimization. Through experimental design using this program, the effects of various design variables on the optimization objectives were evaluated, and an adaptive simulated annealing algorithm was used for global optimization. Furthermore, response surface methodology and a nonlinear quadratic programming algorithm were utilized to obtain a global optimum solution after repeated iterations. Moreover, using a hovercraft air-intake system as the optimized object, the total pressure loss of the system was completely optimized by using a porous medium model and Matlab analysis program, and the accuracy of the structural design optimization program was validated. After the global optimization, the total pressure loss of the air-intake system was reduced by 20.5% compared to the original model. An average nonuniformity of 4.36% of engine inlet speed and 5% local nonuniformity of 11.19% satisfy the design requirements of the hovercraft engine. This method can be directly applied to engineering optimization problems as well as multiobjective optimization tasks after improving the relevant methodologies.     

多约束条件下金刚石圆锯片结构优化研究

基于序列响应面模型和混合优化算法相结合的方式,提出一种在复杂载荷条件下降低金刚石圆锯片锯切噪声的优化方法。建立了多变量、多约束条件下金刚石圆锯片结构优化的数学模型,经计算得到了满足刚度要求的优化圆锯片。通过数学统计分析,获得了尺寸参数对锯片的声学、变形以及应力等性能影响规律。根据结果制备了金刚石圆锯片,锯切实验表明优化锯片能够有效的降低噪声,表明这种方法可为锯片或此类结构的声学优化研究提供新的方向和参考依据。