Methods for the design of formed metal parts with printed sensors

本课题旨在对印刷应变片进行塑料成型，设计创新产品。为此，应变片印在半成品金属部件上，然后再成形。目标是生产成型金属产品与印刷应变片，能够测量弹性应变后的成形过程。该调查是为滚压成形应用程序进行的。到目前为止，还没有预测由成形过程引起的印刷应变片电导率变化的策略。此外，没有已知的方法允许在成形过程后对印刷应变片进行温度补偿并考虑其几何畸变。这些空白将由拟议的项目填补。该项目的目标是开发具有打印传感器的成形金属部件的设计方法和指导方针。k因子是应变片灵敏度的指标，取决于几何（例如横截面积）和材料特定参数（例如电导率）。它们会受到成形过程和环境条件的影响。特别需要研究以下参数对k因子的影响，并推导出解析关系：温度、板材表面纹理、表面制备、变形程度、应变速率和应力状态。丝网印刷油墨的评价标准包括印刷图像的再现性、延展性、附着力和抗刮擦性。此外，设计了一种测试装置，使印刷应变片样品在低应变下具有特征。此外，通过对单轴和多轴塑性变形后的表征，确定k因子随上述参数的变化情况。由此可以推导出一种具有打印传感器的金属成形件设计的解析关系和指导方针。研究结果被用于设计一种通过辊压成形生产的演示器。

This research proposal aims for plastic forming of printed strain gauges to design innovative products. For this purpose strain gauges are printed on semi-finished metal parts which are formed afterwards. The goal is the production of formed metal products with printed strain gauges that are able to measure elastic strains after the forming process. The investigations are performed for a roll forming application. So far, no strategies for the anticipation of the change in conductivity of the printed strain gauges caused by the forming process are available. Furthermore, no approaches are known which permit temperature compensation of the printed strain gauges after the forming process and take into account their geometric distortion. These gaps will be filled by the proposed project. The goal of the project is the development of methods and guidelines for the design of formed metal parts with printed sensors. The k-factor, which is an indicator for the sensitivity of the strain gauges, depends on geometrical (e.g. cross-sectional area) and material-specific parameters (e.g. conductivity). They can be influenced by the forming process and the environmental conditions. In particular, the influences of the following parameters on the k-factor have to be investigated and an analytical relation has to be derived: temperature, surface texture of the sheet, surface preparation, degree of deformation, strain rate and stress state. The screen printing inks are evaluated in terms of reproducibility of the printed image, the ductility, the adhesion and the scratch resistance. In addition, a test device is designed in which printed strain gauges samples are characterized at low strains. In addition, a characterization after single and multi-axis plastic deformation is performed to determine the variation of the k-factor as function of the above mentioned parameters. Thus an analytical relationship and a guideline for the design of formed metal parts with printed sensors can be derived. The findings are used to design a demonstrator which is produced by roll forming.