Slip-line field modeling and analysis of orthogonal cutting with rounded edge worn tool

Cutting tools used in machining operations have slight roundness on the cutting edge regardless of their manufacturing methods. In some cases, edge of cutting tools is specially rounded. In machining operations with those rounded edge cutting tools having extensive application area is used, it is seen that a small region called as dead metal zone is formed in front of the tool and this region is very influence on the plastic flow of workpiece material. Besides cutting tools continue the metal cutting operations as worn tool after being used for a period of time on the contrary to the models in literature in which cutting tools are accepted as perfectly sharp.In this study, a slip-line model for rounded edge worn tool, which considers the dead metal zone, was developed and analyzed by experimental studies. Firstly, a slip-line model for rounded edge tools and then a slip-line model for sharp worn tools were established and analyzed. Finally, a slip-line model for rounded edge worn tools was developed and analysis of the model was obtained by experiments.Micromachining experiments carried out by quick-stop orthogonal cutting device as using sharp and three different rounded edge cutting tools on values of three different flank wear rates, uncut chip thickness, cutting speeds and two different rake angles and cutting force, thrust force and resultant force values were obtained. As results of experiments it was seen that cutting force, thrust foce and thus resultant force values increased when flank wear rate, cutting edge radius and uncut chip thickness were increased. Increasing of cutting speed and rake angle caused to decreasing of force values.Developed slip-line models were analyzed with established algorithms by using experimental results and were controlled their accuracy. Ploughing force, friction force, thickness of primary shear zone, chip curl radius and chip thickness were theoretically calculated by solving developed slip-line models and analyzed their changing with machining parameters. It was seen that ploughing force increased when cutting edge radius, flank wear rate and uncut chip thickness decreased and ploughing force decreased when cutting speed and rake angle increased. It was observed that friction force increased when flank wear rate and uncut chip thickness increased and it decreased when cutting speed and rake angle increased. On the other hand effect of friction force to resultant force decreased when cutting edge radius was increased. It was seen that thickness of primary shear zone increased when cutting edge radius and flank wear rate increased and it was not too much affected from cutting speed and rake angle. It was determined that chip curl radius increased by increasing of flank wear rate and cutting edge radius and decreased by increasing of uncut chip thickness. When cutting speed and rake angle also increased, chip curl radius slightly decreased. When chip thickness was analyzed it was determined that chip thickness slightly increased by increasing of flank wear rate and it slightly decreased by increasing of cutting edge radius.Micro structures of samples obtained from quick-stop orthogonal cutting device were investigated to research the changing of dead metal zone with cutting edge radius and flank wear rate and it was seen that dead metal zone became bigger when cutting edge radius increased and ploughing force and cutting forces also increased by increasing of dead metal zone. It was specified that cutting edge radius, which caused to formation of dead metal zone, decreased and dead metal zone became smaller when flank wear rate increased. Decreasing of dead metal zone caused the decreasing of ploughing force, but friction force increased by increasing flank wear rate. In this case, cutting forces increased.