Proceedings of SerbiaTrib '13

Serbian TribologySocietySERBIATRIB ‘1313 th International Conference onTribologyKragujevac, Serbia, 15 – 17 May 2013Faculty of Engineeringin KragujevacPREDICTION OF COATED TOOLS PERFORMANCE INMILLING BASED ON THE FILM FATIGUE AT DIFFERENTSTRAIN RATESK.D. Bouzakis 1,2,a , R. Paraskevopoulou 1,b , G. Katirtzoglou 1,2,c , S. Makrimallakis 1,2,d , E. Bouzakis 1,2,e ,P. Charalampous 1,f1 Laboratory for Machine Tools and Manufacturing Engineering, Aristoteles University of Thessaloniki, Thessaloniki, Greece2 Fraunhofer Project Center Coatings in Manufacturing, in Centre for Research and Technology Hellasin Thessaloniki, Greece and in Fraunhofer Institute for Production Technology in Aachen, Germanya bouzakis@eng.auth.gr, b paraskeu@auth.gr, c gkatirz@auth.gr, d makrimallakis_s@eng.auth.gr, e E.Bouzakis@certh.gr,f paschalischaralampous@gmail.comAbstract: The knowledge of coated tool wear mechanisms in milling is pivotal for explaining the filmfailure and selecting the appropriate cutting strategy and conditions. In this paper, tool wear experimentswere carried out in milling of four different steels using coated cemented carbide inserts. The variablestress, strain and strain rate fields developed in the tool during cutting affect the film-substratedeformations and in this way the resulting coating’s loads and its fatigue failure. For investigating theinfluence of cyclic impact loads magnitude and duration on the films’ fatigue of coated speciments, animpact tester was employed which facilitates the modulation of the force signal. The attained tool life upto the films’ fatigue failure was assosiated to a critical force for the film fatigue endurance and to thecutting edge entry impact duration. These factors converge sufficiently to the tool life in all examinedmilling kinematics and workpiece material cases.Keywords: milling, tool wear, entry impact duration1. INTRODUCTIONMilling operations are often associated withcomplicated cutting edge-workpiece contact andintensive tool impact loads. These facts render theprediction of the tool wear development a difficultto be achieved task [1, 2]. Recent investigationswith coated cemented carbide inserts revealed thatthe milling up or down kinematic, as well as thecutting parameters, significantly affect the stressfield developed in the cutting edge during thematerial removal and consequently the cuttingperformance [3, 4].The present paper introduces a method forcalculating the coated tool wear evolution inmilling. In such cutting procedures, repetitiveimpact loads with variable duration and magnitudesare exerted on the coated cutting edge, caused bythe interrupted material removal. Hence, it wasnecessary to quantify the effect of the cutting edgeentry impact duration on the coated tool fatiguefailure at various cutting loads. This was enabled bya developed impact tester, facilitating the appliedimpact force modulation [5].2. EXPERIMENTAL DETAILSIn the conducted investigations, peripheral andface milling experiments were conducted by a 3-axis numerically controlled milling center applyingmilling cutters of 17, 35, 57 and 90 mm effectivediameters. The geometry of the cutters and theemployed cutting inserts is exhibited in Figure 1.The cemented carbide inserts are coated by a TiAlNPVD film of ca. 3 μm thickness.13 th International Conference on Tribology – Serbiatrib’13 13