Modern manufacturing processes require high surface quality output. The growing requirements products have to meet are creating the perception that surface finishing processes are often an essential process in meeting product specifications. Surface finishing methods play a key role in achieving strict quality and tolerance requirements. Burnishing is a process which produces a fine surface finish on a workpiece and commonly applied to improve the surface integrity, i.e. surface roughness, residual stress and hardness of a mechanical components. Burnishing has long been used in the automotive industry to finish a wide variety of car and heavy equipment components. Ultrasonic burnishing is a modern, effective method for improving surface quality. The method is based on forging the surface of the workpiece at an ultrasonic frequency with more than 20,000 impacts per second. However, in order to investigate how the method affects the surface quality of the material, a better understanding of surface integrity is required. The aim of this study was to find out how the ultrasonic burnishing method affects the surface integrity and form: surface roughness, hardness, residual stresses and out-of-roundness and diameter changes in different material surfaces. The research analysed the characteristics of the ultrasonic burnishing method of surface finishing, in particular by means of experiments, and its impacts on metal parts made of different materials. The results were evaluated to investigate the optimal process parameters for AM-material. In conclusion, the outcomes of this study show that ultrasonic burnishing improves the surface integrity effectively. The method was found to be highly suitable for finishing different materials, such as AM produced metal components, according to the results of the experiments in this study. The findings show, that method not only affects the top surface efficiently, but also deforms the material more deeply, producing compressive residual stresses in the workpiece. Furthermore, the roundness of a cylindrical workpiece is improved and the dimensional changes are minor. These improvements are achieved without long processing times from the point of view of the resulting surface quality. The conclusions of the dissertation indicate that ultrasonic burnishing is a fast, simple and economical finishing process that provides an improved surface quality and hardness. To this end, future research is proposed on the capabilities the method offers on workpieces with diverse contours, such as finishing double-curved surfaces. In addition, further research is recommended to find the optimal burnishing process parameters with different types of AM materials. Furthermore, the results of this study encourage the greater use of ultrasonic burnishing in diverse industrial fields, which will provide added opportunities for research in the future.
|Publication status||Published - 2018|
|MoE publication type||G5 Doctoral dissertation (article)|
- ultrasonic burnishing, surface integrity, residual stress, surface quality, 3D printing, additive manufacturing