Methods for the design of formed metal parts with printed sensors

本研究计划旨在将印刷应变片进行塑性成形，以设计创新产品。为此，应变片被印刷在随后成型的半成品金属部件上。我们的目标是生产带有印刷应变片的成型金属产品，这些应变片能够在成型过程后测量弹性应变。研究是针对辊轧成形应用进行的。到目前为止，还没有用于预测由成形过程引起的印刷应变片的电导率变化的策略。此外，没有已知的方法允许在成形过程之后对印刷的应变片进行温度补偿并且考虑其几何变形。这些空白将由拟议的项目填补。该项目的目标是开发用于设计带有印刷传感器的成型金属零件的方法和指南。K系数是应变片灵敏度的指标，取决于几何参数（如横截面积）和材料特定参数（如电导率）。它们可能受到成形过程和环境条件的影响。特别是，以下参数对k因子的影响必须进行调查，并推导出一个分析关系：温度，表面纹理的板，表面处理，变形程度，应变速率和应力状态。根据印刷图像的再现性、延展性、粘附性和耐刮擦性来评价丝网印刷油墨。此外，设计了一种测试装置，其中印刷的应变片样品在低应变下表征。此外，进行单轴和多轴塑性变形后的表征，以确定作为上述参数的函数的k因子的变化。由此可导出一个解析关系式，并为带印刷传感器的金属成形件的设计提供指导。研究结果被用来设计一个演示，这是由辊压成型。

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.