Development of cutting-burnishing combined tool and its basic performance - Compressive residual stress generation within the machined surface -
 
Toshiaki Segawa*, Hiroyuki Sasahara*, Tatsuro Ishikawa**,
Hiroyuki Murase** and Masaomi Tsutsumi*
* Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology
** Department of Mechanical Systems Engineering, Tokyo University of Agriculture and Technology
 
We have developed a new tool that is called as the cutting-burnishing combined tool. Figure 1 shows its configuration. This tool can generate effective compressive residual stress within the machined surface concurrently with the milling process. It is expected to improve the mechanical properties such as the fatigue life and the resistance to stress corrosion cracking. The developed tool has two inserts for cutting and two pins for burnishing. These pins are located just inside of the outer diameter of the tool. The pins are held by disk springs, and they rubs over the machined surface by the cutting edges. This paper presents the effect of the cutting conditions of the developed tool upon surface roughness, surface hardness and residual stress of aluminum alloy.

Then we discuss the controllability of such mechanical properties of the machined surface with the setting of the machining conditions. Figure 2 shows the profile of the residual stress within the machined surface layer on the aluminum alloy A7075-T651. It also shows the residual stress profile after the shot peening. It can be seen that almost same level of comparative compressive residual stress as that by the shot peening can be generated by using the proposed tool.

Figure 3 shows the photograph of the machined surface. It can be seen that regularly generated tool marks by the travel of the pins movement, its roughness is much smaller than that obtained by the shot peening.

As a result of the evaluation tests of the machined surface layer, the feed per tooth and the cross feed width are the most important parameters affecting the compressive residual stress on the machined surface. Especially, as the feed per tooth becomes small, the residual stress on the machined surface becomes compressive as shown in Fig. 4. Therefore, the level of the compressive residual stress on the machined surface can be controlled by the setting of these machining conditions.

[Published in Journal of the Japan Society for Precision Engineering, Vol. 72, No. 7 (2006),
pp.909-913.]

Fig. 1 Configuration of developed cutting-burnishing combined tool


Fig. 2 Profile of the residual stress within the machined surface layer


Fig. 3 Photographs of the machined surface


Fig.4 Relationship between residual stress and feed per tooth