# The Key Role of Laser Ultrasonics in the Context of Sustainable Production in an I 4.0 Value Chain
## 5 Conclusions and Outlook  
The LUS method offers an immense variety of applications, whether in production, R&D, the laboratory or an interface, a so-called Smart Manufacturing Lab or SPL. In each of these areas, the method benefits from being applicable in-situ, contactless, at high temperatures, in harsh environments. By analyzing the resulting signals, a variety of different material or product characteristics can be derived in a rapid manner. Due to the constant further development, either of the internal systematics, for example, to increase the measuring frequency, or the more precise development of the models for the evaluation of any materials and alloys, the LUS will be indispensable for almost any scenario in the future. The possibility to reduce the development time of a microstructure model, including the whole required parameter set by about half, provides an enormous advantage. By implementing this methodology, it renders such microstructure models applicable, even in sectors where integration was not feasible for financial reasons. This development can provide a springboard for more economical and efficient production, since the effects of process conditions on the microstructure can be analyzed in advance.  
Of course, the advantages on the production line are also of enormous importance. The possibility to inspect not only geometric parameters for tolerances in-line, but also to monitor the prevailing microstructure significantly, contributes to increasing efficiency and reducing scrap.  
Especially the application as a CPPS in a digitalized production environment contributes to a considerable benefit. When combining the lab-scale utilization for a production facility, unimagined possibilities can still be considered with the assistance of the enablers of I 4.0. The interaction of DM, DS, and DTs and real-time process data integration with ML along the value chain can be a substantial contribution to the sustainable production of the future.  
The main shortcomings in the implementation of the LUS in a SPL are that the evaluation of the obtained data is not yet mature for a variety of different materials. Even though a large number of investigations have already been carried out for microstructural changes of some various materials, it is necessary to investigate the behavior using the LUS for additional materials and alloys in a large-scale, creating a sub-ordinate database including microstructural data.  
Conceptualization, K.H. and M.S. ([PERSON]): writing--original draft preparation, K.H. and M.S. ([PERSON]); writing--review and editing, M.S. ([PERSON]), K.H. and M.S. ([PERSON]); visualization, M.S. ([PERSON]); supervision, M.S. ([PERSON]); project administration, K.H. and M.S. ([PERSON]); funding acquisition, M.S. ([PERSON]). All authors have read and agreed to the published version of the manuscript.  
The authors gratefully acknowledge the financial support by the Austrian Promotion Agency (FFG) under the scope of the BRIDGE program (grant no. 880577).  
Not applicable.  
The authors declare no conflict of interest.