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The aim of this investigation is to identify the Al2O3-(W, Ti)C ceramic fracture modes and failure mechanisms under different cutting speeds and feed rates during intermittent turning of hardened 20CrMnTi steel. The failure surfaces of the cutting tools were examined by digital optical microscope and scanning electron microscope. The cutting forces and transient temperature in the intermittent turning process were measured during the entire life cycle. The experimental results showed that the cutting forces exhibited an increasing trend with the tool failure progression, which in turn accelerated the tool failure progression. The main failure modes of ceramic tools were wear and micro-chipping in the initial stage and final fractures, resulting from mechanical damage and thermal damage in intermittent turning processes. And the cutting temperature increased with the increase in cutting speed. The cutting speeds and feed rates were closely correlated with ceramic tool fracture modes and failure mechanisms. Furthermore, the combination of cutting parameters was divided into four regions with different fracture modes and failure mechanisms of cutting tools according to the fracture morphology of cutting tools. This partitioning analysis can provide a basis for the design and development of different ceramic cutting tools with the desired properties for different applications. [ABSTRACT FROM AUTHOR]

This paper presents the findings of experimental investigations into the effects of tool path strategies on fatigue life of high-speed ball-end-milled AISI H13 steel. Milling operations were conducted under three different tool path strategies with four levels of feed per tooth 0.1-0.4 mm/z. Fatigue life of machined samples was tested by three-point bending fatigue tests. Results show that the fatigue performance is susceptible to tool path strategies. Different tool path strategies bring the difference in microscopic stress concentration induced by the orientational surface topography and the effective residual stress defined as the residual stress component along the applied tensile stress direction. These two aspects can alter the real maximum tensile stress suffered by the milled surface and then influence the fatigue performance. Moreover, optimization methods for the tool path selection are put forward based on the findings that the effective residual stress has more significant influence on fatigue performance than the microscopic stress concentration and the more compressive the residual stress is, the longer the fatigue life will be. This study indicates that the fatigue performance for a ball-end-milled surface can be improved from the tool path control point of view. [ABSTRACT FROM AUTHOR]