Methods for the design of formed metal parts with printed sensors

本研究方案旨在对印刷应变片进行塑性成形，以设计出创新产品。为此，应变计被印刷在半成品的金属零件上，然后形成。其目标是生产具有印刷应变计的成形金属产品，该应变计能够测量成形过程后的弹性应变。这些调查是为辊压成型应用而进行的。到目前为止，还没有策略来预测由成形过程引起的印刷应变片的电导率变化。此外，还没有已知的方法允许在成形过程之后对印刷应变计进行温度补偿并考虑它们的几何变形。这些空白将通过拟议的项目来填补。该项目的目标是开发设计带有印刷传感器的成形金属部件的方法和指南。K因子是应变计灵敏度的指标，它取决于几何参数(如横截面面积)和特定材料参数(如电导率)。它们会受到成型过程和环境条件的影响。特别是，必须研究下列参数对k因子的影响，并推导出一个解析关系式：温度、板材表面织构、表面准备、变形程度、应变率和应力状态。丝网印刷油墨从印刷图像的再现性、延展性、附着力和耐刮擦性等方面进行评价。此外，还设计了一种测试装置，将打印的应变片样品表征为低应变。此外，还进行了单轴和多轴塑性变形后的表征，以确定k因子随上述参数的变化。从而可以推导出带印制传感器的成形金属零件的解析关系式和设计准则。研究结果被用来设计一种滚压成型的演示装置。

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.