Research on Chip Shear Angle and Built-Up Edge of Slow-Rate Machining EN C45 and EN 16MnCr5 Steels

Abstract

One of the phenomena that accompanies metal cutting is extensive plastic deformation and fracture. The excess material is plastically deformed, fractured, and removed from the workpiece in the form of chips, the formation of which depends on the type of crack and their propagation. Even in case of the so-called 'continuous' chip formation there still has to be a fracture, as the cutting process involves the separation of a chip from the workpiece. Controlling the chip separation and its patterning in a suitable form is the most important problem of the current industrial processes, which should be highly automated to achieve maximal production efficiency. The article deals with the chip root evaluation of two EN C45 and EN 16MnCr5 steels, focusing on the shear angle measuring and built-up edge observation as important factors influencing the machining process, because a repeated formation and dislodgement of built-up edge unfavorably affects changes in the rake angle, causing fluctuation in cutting forces, and thus inducing vibration, which is harmful to the cutting tool. Consequently, this leads to surface finish deterioration. The planing was selected as a slow-rate machining operation, within which orthogonal and oblique cutting has been used for the comparative chips' root study. The planned experiment was implemented at three levels (lower, basic, and upper) for the test preparation and the statistical method, and regression function was used for the data evaluation. The mutual connections among the four considered factors (cutting speed, cutting depth, tool cutting edge inclination, and rake angle) and investigated by the shear angle were plotted in the form of graphical dependencies. Finally, chips obtained from both steels types and within both cutting methods were systematically processed from the microscopic (chip root) and macroscopic (chip pattern) points of view.Metals 2019, 9, 956 2 of 27 of a machined surface are in many cases not achievable by mechanical working or casting processes, because the surfaces of the parts are adversely affected. This is why machining is needed.[3] Controlling the chip separation and its patterning in a suitable form is the most important problem of the current industrial processes, which should be highly automated to achieve maximal production efficiency.One of the phenomena that accompanies metal cutting is extensive plastic deformation and fracture. The excess material is plastically deformed, fractured, and removed from the workpiece in the form of chips, the formation of which depends on the type of crack and their propagation. Even in the case of so-called 'continuous' chip formation there still has to be a fracture, as the cutting process involves the separation of a chip from the workpiece. Chips at the machining are formed due to tearing and shearing, the workpiece material adjacent to the tool face is compressed and a crack runs ahead of the cutting tool and towards the body of the workpiece. Cutting takes place intermittently and there is no movement of the w...

Failure Mechanisms in Alloys

“…More specifically, the broad category of static overload includes more generic subjects also from the field of manufacturing-related topics, where the effect of deformation and fracture was studied as an important and undetached ingredient of the fabrication process per se (e.g., hot and cold working, machining). Therefore, the mostly "intense area" (Overload/Static) comprises studies concerning general deformation and fracture phenomena, as the result of instant loading/testing conditions [4,9,10,14,15,19] and studies related to manufacturing and production processes [6,7,12,13,16,20,22,25,26]. Testing and modeling procedures addressing the evolution of deformation and fracture during forming [7,13,26], the impact toughness, [4] and certain production process characteristics [25] are also included.…”

“…Testing and modeling procedures addressing the evolution of deformation and fracture during forming [7,13,26], the impact toughness, [4] and certain production process characteristics [25] are also included. Nevertheless, shear fracture processes that emerged in machining and chip formation are also part of this broader group of studies, relevant to manufacturing topics (see [12,16,20]). Fatigue and Cyclic Loading [8,9,18]; c.…”

“…(i) Casting and Metal Forming [6,7,11,13,15,19,[24][25][26] (ii) Machining [12,16,20] (iii) Chemical/Petrochemical [3,17,21,23] (iv) Heat Treatment [22] (v) General Plant Machinery [1,9,18,24] b. Fatigue and Cyclic Loading [8,9,18]; c. Corrosion and Environmentally Assisted Cracking [3,5,11,21]; d. Wear and Surface Degradation [1,24,27].…”

Failure Mechanisms in Alloys

“…Combined (experimental, analytical, numerical model, etc.) [3,[6][7][8][12][13][14][15][16][18][19][20]22,25,26] As can be readily observed, the experimental and empirical approach is the dominant methodology of failure investigation. In addition, the emergence of numerical simulation, using finite element modeling (FEM), tends to be very popular in the prediction of material behavior and potential failure prevention.…”

“…Reference Structural and pipeline steels [1,5,9,13,16,20,22,27] Cast iron [14,19] Special resistance and stainless steels [3,4,9,11,17,18,21,23,24] Wear resistant coatings and surface layers [24,27]…”