3D打印中的结构优化问题研究

发布时间：2018-11-11 10:47

【摘要】：传统的产品开发过程一般可分为两阶段：产品设计和制造。它们由设计工程师和制造工程师来分别负责,于是逐步形成了“我负责设计,你负责制造”的相对独立模式。这种独立模式下,设计与制造两阶段之间缺乏一些沟通与联系,导致了最终开发产品存在修改多,成本高,周期长,质量低等问题。为了避免这些问题,面向制造的设计(Design for manufacturing, DFM)模式应运而生。DFM指在产品设计阶段就从制造对产品的要求来考虑设计,使所设计的产品具有良好的制造性能,从而避免在产品制造中可能会出现的一些成本、制造和质量等问题。3D打印在面向制造的设计领域能很好地发挥其优势,它被认为是第三次工业革命的重要标志之一。它以3D数字模型为输入,利用可粘合、可固化等材料,通过分层打印、堆积成形的方式来生成所需产品,因此,它虽称“打印”,实质是以3D模型为基础的“制造”。它有效地打通了数字化模型设计与真实产品制造之间的界限,将产品设计与制造两阶段更紧密地关联在一起。因此,如何发挥3D打印的技术优势,实现面向制造的设计,将对促进我国产品开发模式转型、制造业升级有重要意义。在这一背景下,本文在总结3D打印中几何计算相关研究成果的基础上,对3D打印中的结构优化问题进行了研究。第二章对3D打印中结构优化相关研究成果,从节省材料、强度、稳定性和支撑优化等四方面进行了分类介绍,总结分析了结构优化中现有研究成果的一些优点和不足。第三章从节省材料角度出发,考虑如何能在不牺牲打印物体表面质量和满足强度要求的条件下,通过结构优化来减少打印材料消耗,降低打印成本。针对这一问题,我们给出一种面向体积极小的拓扑优化算法。该算法采用传统渐进结构优化方法来优化模型,同时根据模型力学计算所得的最大Von Mises应力与材料允许应力之比来引导模型体积减小进化。同时,我们引入多分辨率技术,由粗网格再到细网格,进行优化计算,有效地提高了计算效率。与现有其他给定结构模式的方法相比,我们的方法所得优化结果能更好地体现模型荷载受力的传递路径。针对许多个人用户设计模型所产生的结构缺陷或强度问题,第四章给出一种旨在帮助个人用户在设计模型的同时能进行结构分析和优化的方法。该方法没有采用有较大计算代价的有限元来进行结构分析,而是采用计算代价较低的截面结构分析方法。同时我们引入骨架工具来辅助模型编辑,对编辑后的模型利用骨架来进行截面结构分析。根据分析结果,对模型上的脆弱区域以骨架为工具来优化修正,以增强这些区域的强度。实验结果表明,该方法具有良好的实用性。最后一章对我们的工作进行了总结和展望。
[Abstract]:The traditional product development process can be divided into two stages: product design and manufacture. They are the responsibility of the design engineer and the manufacturing engineer respectively, and a relatively independent pattern of "I am in charge of design, you are in charge of manufacturing" has evolved. In this independent mode, there is a lack of communication and connection between the two stages of design and manufacture, which leads to the problems of many modifications, high cost, long cycle and low quality in the final product development. In order to avoid these problems, the (Design for manufacturing, DFM) pattern of manufacturing-oriented design emerges as the times require. DFM refers to considering the requirements of the product in the design stage of the product, so that the designed product has good manufacturing performance. In order to avoid some possible problems in product manufacturing, such as cost, manufacturing and quality, 3D printing can give full play to its advantages in the field of manufacturing-oriented design, and it is considered as one of the important symbols of the third industrial revolution. It takes 3D digital model as input, uses materials such as adhesive and solidification to produce the required products by layering printing and stacking forming. Therefore, although it is called "printing", it is essentially "manufacturing" based on 3D model. It effectively clears the boundary between digital model design and real product manufacturing, and links the two stages of product design and manufacturing more closely. Therefore, how to give full play to the technological advantages of 3D printing and realize manufacturing oriented design will be of great significance to promote the transformation of product development mode and upgrade of manufacturing industry in China. Under this background, the structure optimization in 3D printing is studied on the basis of summarizing the research results of geometric calculation in 3D printing. In the second chapter, the related research results of structural optimization in 3D printing are classified and introduced in terms of material saving, strength, stability and support optimization, and some advantages and disadvantages of existing research results in structural optimization are summarized and analyzed. In chapter 3, from the point of view of saving materials, we consider how to reduce the consumption of printing materials and reduce the cost of printing by optimizing the structure without sacrificing the surface quality of printed objects and meeting the requirements of strength. In order to solve this problem, we propose a topology optimization algorithm for minimal volume. The model is optimized by the traditional evolutionary structural optimization method, and the model volume reduction is guided by the ratio of the maximum Von Mises stress to the allowable stress of the material calculated by the model mechanics. At the same time, we introduce multi-resolution technology, from coarse grid to fine grid, to optimize the calculation, which effectively improves the efficiency of calculation. Compared with other existing methods for given structural modes, the optimization results obtained by our method can better reflect the load transfer path of the model. In order to solve the structural defects or strength problems caused by many individual user design models, a method is proposed in chapter 4 to help individual users to analyze and optimize the model at the same time. In this method, the finite element method with high computational cost is not used for structural analysis, but the section structure analysis method with lower computational cost is used. At the same time, we introduce skeleton tool to assist model editing, and use skeleton to analyze cross-section structure of the edited model. According to the analysis results, the skeleton is used as a tool to optimize and modify the fragile regions in the model to enhance the strength of these regions. The experimental results show that this method has good practicability. The last chapter summarizes and prospects our work.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TP391.73

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