Optimierung des Temperaturfeldes beim Laserstrahlhärten

• Optimization of the temperature field during laser hardening

Schulz, Martin; Bergs, Thomas (Thesis advisor); Loosen, Peter (Thesis advisor)

1. Auflage. - Aachen : Apprimus Verlag (2022)
Book, Dissertation / PhD Thesis

In: Ergebnisse aus der Produktionstechnik 22/2022
Page(s)/Article-Nr.: 1 Online-Ressource : Illustrationen, Diagramme

Dissertation, RWTH Aachen University, 2021

Abstract

Since its first industrial application in the mid-1960ties laser technology has developed into a cross-sectional technology used in various manufacturing processes. Martensitic hardening through laser radiation is one of the first processes where laser technology was used in industrial production. Closed loop control by pyrometers and efficient and powerful sources such as diode lasers are considered to be the most significant milestones in the development of laser technology up to the present day. The achievable process results also have continually improved due to the technical capabilities to manipulate the intensity profile. While homogenized intensity distribution devices currently are state of the art in industrial applications, more powerful beam shaping devices are tested in research and development. These systems allow for new degrees of freedom in the shaping of the intensity distribution. How these new degrees of freedom can be utilized to optimize the laser hardening process still is unknown and its further research is the topic of this thesis. The present work is not focusing on the analysis of the different new techniques of beam shaping but explores the possible ways and means to optimize the temperature field generated by them during the process. The numeric solution of the inverse heat conduction problem allows to calculate the necessary intensity distribution which may be realized with different beam shaping techniques. To obtain optimal temperature fields the thesis is structured as follows: Chapter 2 begins with a short outline of the topic and then discusses the temperature dependence of the process. Thereafter the currently producible beam profiles are de-scribed. The influence of the beam profile on the temperature profile in the process and the effects on the production process are analysed. In chapter 3 the research hypothesis is deduced on the basis of the scientific discussions in the chapter State of the art. Based on generic requirements for laser hardened products, evaluation parameters for optimized temperature fields are concluded in chapter 4.A model is developed in chapter 5 describing the dependence of the evaluation parameters on the temperature field. Subsequently, the model is in chapter 6 verified by means of the homogenous intensity distribution. The capability of this distribution is discussed. Based on the model assumptions, potential temperature fields are inferred in chapter 7 with the objective of optimizing the process in accordance with the evaluation parameters. Chapter 8 covers the final verification of the model as well as the validation of optimized temperature fields implemented on the basis of empirical studies with freeform mirrors.