Understanding the Prime Factors Driving Distortion in Milled Aluminum Workpieces

了解导致铣削铝工件变形的主要因素

• 批准号: 1663341
• 负责人: Barbara Linke
• 金额: $ 32.01万
• 依托单位: University of California-Davis
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-04-15 至 2021-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1663341&HistoricalAwards=false
• 关键词: Understanding; Prime; Factors; Driving; Distortion

Rework or rejection of metallic components due to component shape errors resulting from machining distortion reflect a significant economic loss. The cost of machining distortion is estimated to be billions of dollars annually, with a large part borne in the aerospace sector, so the control of machining distortion is a significant industrial challenge. Existing engineering approaches address the problem, but provide only point solutions to specific circumstances and rely on empirical trials at high cost. The collaborative research between the University of California, Davis (USA) and the University of Kaiserslautern (Germany) focuses on understanding the main factors and mechanisms that drive machining distortion, and subsequently explores the use of models for prediction and control. Distortion will be analyzed by analytical and experimental methods across variations of its main drivers: initial residual stress and geometry of the workpiece and parameters used in machining. The work will advance sustainable manufacturing in aerospace and other metal working industries by studying approaches that can lead to reduced losses from rework and rejection of parts. Along with graduate students directly involved, graduate and undergraduate students working in research laboratories at the two partner institutions will benefit from the international communication and exchange. Research results will be used to educate undergraduate and graduate students at both universities in existing courses in manufacturing and engineering (mechanical and aerospace), and the general public will learn about machining distortion and compensation through publications, conferences, and institutional websites. New knowledge will be gained and shared on how part geometry, symmetry, and stress levels affect machining distortion. The main objective of this project is to understand how workpiece deformations can be forecast and controlled by predictive or compensative techniques for more economical and sustainable manufacturing. The research plan relies on unique expertise and facilities at two partner institutions, and synergizes metal-cutting experiments and residual stress measurements with analytical and numerical modeling. The deep understanding of residual stress at the University of California, Davis is complemented by the expertise in milling assessment at the University of Kaiserslautern. The hypothesis to be tested is: the effects of bulk residual stress (from material processing) and machining residual stress (from milling) each create distinct effects on workpiece deformation and can be separated. Therefore, bulk residual stress and machining residual stress are first analyzed separately. In work task 1 at UC Davis, different input models for bulk residual stress will be investigated, in particular process models from the University of Kaiserslautern and the eigenstrain model from UC Davis. Furthermore, different methods (simultaneous or incremental material removal) to simulate geometry changes in workpieces with bulk residual stress are analyzed. UC Davis is responsible for defining the bulk material stress levels and characterizing bulk residual stresses with established mechanical techniques. Complementary, work task 2 is performed at the University of Kaiserslautern and different input models and their quality for machining residual stress will be investigated. Comprehensive milling experiments will help to understand the distortion of thin-walled monolithic workpieces from machining residual stress and serve as a database for the combined bulk and machining residual stress distortion. At the University of Kaiserslautern, X-ray diffraction is used to characterize the surface residual stresses. Based on the new knowledge, in work task 3 both research partners will analyze how the machining residual stresses depend on the bulk residual stresses, for example by machining within different stress regimes. In addition, boundary conditions such as effects of workpiece setup and constraint and the geometric criteria for three regimes will be explored: where both types of residual stresses or one individually have major impact on machining distortion. Finally, in work task 4 compensation techniques will be investigated and summarized first in a best practice model. The possibility to compensate the bulk induced distortion via a deliberate machining induced distortion will be explored.

由于加工变形引起的零件形状误差而导致的金属零件返工或报废是一项重大的经济损失。据估计，每年加工变形的成本高达数十亿美元，其中很大一部分是由航空航天部门承担的，因此加工变形的控制是一个重大的工业挑战。现有的工程方法解决了这个问题，但只针对特定情况提供了点解决方案，并依赖于高成本的经验试验。加州大学戴维斯分校(美国)和德国凯泽斯劳滕大学(德国)的合作研究重点是了解驱动加工变形的主要因素和机制，并随后探索使用模型进行预测和控制。变形将通过分析和实验方法分析其主要驱动因素的变化：初始残余应力和工件的几何形状以及加工中使用的参数。这项工作将通过研究减少返工和零件报废损失的方法，推动航空航天和其他金属加工行业的可持续制造。除了直接参与的研究生，在两个合作机构的研究实验室工作的研究生和本科生将从国际沟通和交流中受益。研究成果将用于两所大学现有制造和工程(机械和航空航天)课程的本科生和研究生教育，普通公众将通过出版物、会议和机构网站了解加工变形和补偿。将获得并分享有关零件几何形状、对称性和应力水平如何影响加工变形的新知识。这个项目的主要目标是了解如何通过预测性或补偿性技术预测和控制工件变形，以实现更经济和可持续的制造。该研究计划依赖于两个伙伴机构的独特专业知识和设施，并将金属切割实验和残余应力测量与分析和数值建模相结合。加州大学戴维斯分校对残余应力的深入了解与凯泽斯劳滕大学在铣削评估方面的专业知识相辅相成。要检验的假设是：主体残余应力(来自材料加工)和机械加工残余应力(来自铣削)各自对工件变形产生不同的影响，并且可以分开。为此，首先对整体残余应力和加工残余应力分别进行了分析。在加州大学戴维斯分校的工作任务1中，将研究主体残余应力的不同输入模型，特别是来自凯泽斯劳滕大学的过程模型和来自加州大学戴维斯分校的本征应变模型。此外，还分析了不同的方法(同时去除材料和增量去除材料)模拟具有大体积残余应力的零件的几何变化。加州大学戴维斯分校负责定义主体材料应力水平，并用成熟的机械技术表征主体残余应力。作为补充，工作任务2在凯泽斯劳滕大学进行，将调查不同的输入模型及其加工残余应力的质量。综合的铣削实验将有助于了解薄壁整体零件在加工残余应力时的变形情况，并可作为整体和加工残余应力组合变形的数据库。在凯泽斯劳滕大学，X射线衍射被用来表征表面残余应力。在新知识的基础上，在工作任务3中，两个研究伙伴将分析加工残余应力如何取决于整体残余应力，例如通过在不同应力状态下进行加工。此外，还将探讨边界条件，如工件设置和约束的影响以及三个区域的几何准则：其中两种类型的残余应力或一种单独的残余应力对加工变形有重大影响。最后，在工作任务4中，我们将首先在最佳实践模型中调查和总结薪酬技巧。通过刻意加工引起的变形来补偿体诱导变形的可能性将被探索。

项目成果

Two-dimensional Mapping of Bulk Residual Stress Using Cut Mouth Opening Displacement

使用切割口张开位移进行体积残余应力的二维映射

• DOI: 10.1007/s11340-021-00745-2
• 发表时间: 2021
• 期刊: Experimental Mechanics
• 影响因子: 2.4
• 作者: Chighizola, C. R.;Hill, M. R.
• 通讯作者: Hill, M. R.

Intermethod Comparison and Evaluation of Measured Near Surface Residual Stress in Milled Aluminum

铣削铝近表面残余应力测量的方法间比较和评估

• DOI: 10.1007/s11340-021-00734-5
• 发表时间: 2021
• 期刊: Experimental Mechanics
• 影响因子: 2.4
• 作者: Chighizola, C. R.;D’Elia, C. R.;Weber, D.;Kirsch, B.;Aurich, J. C.;Linke, B. S.;Hill, M. R.
• 通讯作者: Hill, M. R.