Multi-Physics Modeling of Laser Beam Drilling with Temporally Shaped Pulses

• Applicant: Professor Dr.-Ing. Michael Schmidt
• Subject Area: Production Automation and Assembly Technology
• Term: from 2015 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 278627194

Due to its high efficiency laser drilling with short pulses is widely applied in industry. However, for quality sensitive applications the limited processing accuracy increasingly necessitates the use of ultrashort laser pulses with drastically lower efficiency. Drilling with temporally shaped pulses offers an appealing alternative combining high efficiency with enhanced precision. However, although the efficacy of temporal pulse shaping of short laser pulses in terms of increasing ablation efficiency and surface quality has been experimentally proven, experimental investigations have not yet led to an in-depth understanding of the process. Therefore, in the proposed research project we would like to combine numerical and experimental investigations in order to increase process understanding and to develop an analytical process model. Understanding the process and the mechanisms of material removal in more detail, we would like to use this acquired knowledge to tailor pulse shapes depending on case-specific process parameters and the drilling strategy. Finally, the results will be combined to develop practical guidelines for current and potential industrial users.To meet these objectives, the project will be divided into two phases. In the first phase, an in-house predeveloped transient fluiddynamic numerical model for the simulation of laser beam material processing will be developed further to enable accurate modeling of the drilling process. Therefore, a multi-phase description and compressibility will be included into the model. To ensure accuracy of the model under development, verification experiments will be conducted in parallel to the simulations, enabling constant iterative comparison of simulative and experimental results. Several experimental methods, comprising metallographic grindings, Schlieren photography, pump-probe setups and drilling of sandwiched layers will be used providing deep insight into both material and the area above the sample.In the second project phase, simulations and experiments will be used to conduct parameter studies for both temporally shaped and Gaussian laser pulses. With these investigations, the influence of various process parameters onto process dynamics, processing results and efficiency will be systematically analyzed for single pulse and percussion drilling. These results will be combined to develop an analytic process model for process dynamics and efficiency of laser beam drilling with arbitrarily shaped pulses. This model will then be used to adjust pulse shapes such that an optimized drilling result is obtained depending on the process parameters and strategies, leading to application-specific pulse shape tailoring. In the final step, the main results will be summarized in a set of user guidelines, which will comprise practical advice for industrial users to optimize process efficiency and drilling quality depending on the individual application and process parameters.

• DFG Programme: Research Grants