Showing papers on "Built up edge published in 1997"

An experimental design for surface roughness and built‐up edge formation in lathe dry turning

Abstract: Investigates the effects of the most influential cutting parameters (cutting speed, feed rate, depth of cut, tool nose radius, tool length and work piece length) on surface roughness quality and on the formation of built‐up edge in a lathe dry turning process of mild carbon steel samples. A full factorial design (384 experiments), taking into account the three‐level interactions between the independent variables has been conducted. The results show that the following three‐level interactions: feed rate × cutting speed × depth of cut, feed rate × cutting speed × tool nose radius and tool nose radius × depth of cut × tool length have significant effects on surface roughness in this type of machining operation. Shows that the analysis of main effects alone and even two‐level interactions could lead to a false interpretation of the results. The analysis of variance revealed that the best surface roughness is achieved with a low feed rate, a large tool nose radius and a high cutting speed. The results also show that the depth of cut has no significant effect on surface roughness when operating at cutting speeds higher than 160m/min. Furthermore, it is shown that built‐up edge formation deteriorates surface roughness when machining mild carbon steel at specific feed rate, tool nose radius and cutting speed levels. Proposes a new model for evaluating the limiting cutting speed to avoid the built‐up edge formation. Finally, shows through experimentation that an increase in depth of cut would lead to improved surface roughness when tool vibration is increased.

Fracture mechanisms in chip formation processes

Abstract: Metal cutting is accompanied by extensive plastic deformation and fracture. Quick stop sectional specimens of the chip formation of medium carbon and resulphurised free cutting steel have been studied in order to determine the nucleation and growth mechanism of cracks during machining and their relation to the fracture process. During machining two main types of cracks were observed: internal crack formation in the primary shear zone and cracks associated with the formation of the built up edge (BUE). Internal crack formation is due to void formation either at MnS inclusions or on the ferrite/pearlite interface, while cracks associated with the BUE were formed below the flank face and ahead of the rake face of the tool. The type of chip formation was classified according to the mechanism of crack formation. In both of the steels used, quasicontinuous chips and chips with BUEs were obtained. Although, the quasicontinuous chips contained cracks and voids, they did not propagate right through the she...

Growth model of built-up edge based on inhomogeneities in microstructure of steel

Abstract: The proposed model simulates the built-up edge formed when single- and multi-phase steels are machined. The microstructure that forms the built-up edge are summarized as follows: the number of phase is two or more, and each phase has a high enough deformability to form a multi-phase layer and cracks propagate between the different phases in the layer. No built-up edge forms in the single- and dual-phase such as ferrite and spherodized cementite, and tempered martensite and cementite having a low deformability. The built-up edge forms in dual- and multi-phase such as ferrite and pearlite, ferrite and graphite, and ferrite and manganese sulphide having a high deformability.