Investigation of Vibrations During International Turning - An Experimental and Numerical Study

Abstract: This thesis deal with vibration problem in a cutting process. The cutting process is internal turningwith a relatively stiff tool and the work-piece and clamping sets the stability limit. During theoperation some work-pieces are subjected to chatter. Previous research have derived numerousways to calculate stability limits and theories about chatter elimination. In this thesis single degreeof freedom models are used to model the system behaviour for different modes.The main goal is to investigate the cause of chatter and give suggestions for improvements toeliminate chatter. Experimental modal analysis of the work-piece – clamping and tool system wasdone in order to analyse the system behaviour and derive SDOF models for stability calculation.Measurement of the sound during operation was also analysed but without any applicability. Finiteelement modelling of the work-piece was used to calculate the eigen-frequensies and frequencyresponse function. Measurement of chatter wavelength in finished work-pieces gave usefulinformation about the dominating vibration mode for this problem.The chatter frequency, from the work-piece, consist with the chatter stability calculation of thework-piece – clamping system's lowest mode. The results from finite element calculation does notshow this mode and it strongly imply that this mode is a property of the work-piece clamping. Thestability calculation shows that the current operation conditions are close to optimal, but a smallchange is recommended. The main result is that the chatter is due to insufficient clamping and thatthe easiest way to eliminate the problem is most likely to change clamping.v