Predicting Continuous Chip to Segmented Chip Transition in Orthogonal Cutting of C45E Steel through Damage Modeling

Machining process modeling has been an active endeavor for more than a century and it has been reported to be able to predict industrially relevant process outcomes. Recent advances in the fundamental understanding of material behavior and material modeling aids in improving the sustainability of industrial machining process. In this work, the flow stress behavior of C45E steel is modeled by modifying the well-known Johnson-Cook model that incorporates the dynamic strain aging (DSA) influence. The modification is based on the Voyiadjis-Abed-Rusinek (VAR) material model approach. The modified JC model provides the possibility for the first time to include DSA influence in chip formation simulations. The transition from continuous to segmented chip for varying rake angle and feed at constant cutting velocity is predicted while using the ductile damage modeling approach with two different fracture initiation strain models (Autenrieth fracture initiation strain model and Karp fracture initiation strain model). The result shows that chip segmentation intensity and frequency is sensitive to fracture initiation strain models. The Autenrieth fracture initiation strain model can predict the transition from continuous to segmented chip qualitatively. The study shows the transition from continuous chip to segmented chip for varying feed rates and rake angles for the first time. The study highlights the need for material testing at strain, strain rate, and temperature prevalent in the machining process for the development of flow stress and fracture models.

ANALISIS RADIUS PEMUTUS BERAM (CHIP BREAKER) TERHADAP KEKASARAN PERMUKAAN PADA PROSES BUBUT

In the cutting process on the tirning machine the shape of chips generatedvaries among long chip (continuous chip) and a dashed chip, chip shape isinfluenced by the geometry of the tool including chip breaker radius appliedcutting tool, and the radius of the breaker chip thought to have an influence onworkpiece surface roughness and tools durabulity. The influence of the radius ofthis chip breaker needs to be analyzed for how it effect the value of the surfaceroughness. The goal of my research is to find the optimal surface roughness isgenerated by certain radius enabling have to be used for guidance for thetoolmaker in turning machine in metal manufakturing. The conclusion from thisstudy is the difference in roughness significant value to the amount of burr givenradius breaker.

Study of the Shear Strain and Shear Strain Rate Progression During Titanium Machining

Machining is among the most versatile material removal processes in the manufacturing industry. To better optimize the machining process, the knowledge of shear strains and shear strain rates within the primary shear zone (PSZ) during chip formation has been of great interest. The objective of this study is to study the strain and strain rate progression within the PSZ both in the chip flow direction and along the thickness direction during machining equal channel angular extrusion (ECAE) processed titanium (Ti). ECAE-processed ultrafine-grained Ti has been machined at cutting speeds of 0.1 and 0.5 m/s, and the shear strain and the shear strain rate have been determined using high speed imaging and digital image correlation (DIC). It is found that the chip morphology is saw-tooth at 0.1 m/s while continuous at 0.5 m/s. The cumulative shear strain and the incremental shear strain rate of the saw-tooth chip morphology can reach approximately 3.9 and 2.4 × 103 s−1, respectively, and those of the continuous chip morphology may be approximately 1.3 and 5.0 × 103 s−1, respectively. There is a distinct peak shift in the shear strain rate distribution during saw-tooth chip formation while there is a stable peak position of the strain rate distribution during continuous chip formation. The PSZ thickness during saw-tooth chip formation is more localized and smaller than that during continuous chip formation (28 versus 35 μm).

Split Cutter Method for Contact Stresses Research over Flank Surface of a Cutter

The paper presents a method for of contact load (stress) research over a flank land of a cutter by a “split cutter” (sectional cutter) method which is more preferable in cutting steels and durable materials in industrial cutting mode. The research of contact stresses distribution over surfaces of a cutter must be carried out on the special rigid four-component dynamometer for the “split cutter” with inspection of total components of cutting force Pz and Py. However, the investigation of contact loads distribution over the flank land faces the problem due to elastic deformation of measuring elements and penetration of work material into a slit between the two parts of the “split cutter”. The research of contact stresses distribution over a face of a cutter should be carried out on a lathe with horizontal radial feed, while the research of contact stresses distribution over a flank land should be done on a horizontal-milling machine with vertical radial feed of a table. The distributions of contact stresses over the flank land of the cutter in free orthogonal turning of a disk made from ductile brass (63Cu-37Zn), brittle brass (57Cu-39Zn-1Al-3Mn) are described. In machining ductile brass with formation of a continuous chip, extreme pattern of normal σh and tangential τh contact stresses epures (curves of distribution) over a flank land is observed, i.e. the highest contact stress is at some distance from the cutting edge. In machining brittle brass with formation of a discontinuous chip, the highest contact stress is observed, on the contrary, near the cutting edge. The character of normal contact stresses over a flank-land depends on the type of the chip formation due to a sag of the transient surface under the act of a radial component of the cutting force on the rake surface.

In situ analysis of flow dynamics and deformation fields in cutting and sliding of metals

The flow dynamics, deformation fields and chip-particle formation in cutting and sliding of metals are analysed, in situ , using high-speed imaging and particle image velocimetry. The model system is a brass workpiece loaded against a wedge indenter at low speeds. At large negative rake angles, the flow is steady with a prow of material forming ahead of the indenter. There is no material removal and a uniformly strained layer develops on the workpiece surface—the pure sliding regime. When the rake angle is less negative, the flow becomes unsteady, triggered by formation of a crack on the prow free surface and material removal ensuing—the cutting regime. The strain on the prow surface at crack initiation is found to be constant. Chip morphologies, such as discrete particle, segmented chip and continuous chip with mesoscale roughness, are shown to arise from a universal mechanism involving propagation of the prow crack, but to different distances towards the indenter tip. The simple shear deformation in continuous chip formation shows small-angle oscillations also linked to the prow crack. Implications for material removal processes and ductile failure are discussed.

Investigation on the Elemental Chip Formation Process in Hard-to-Machine Material Cutting

The mechanism of discontinuous chip formation has been studied less than the mechanism of continuous chip formation. However, when most modern materials having specific physical and mechanical properties are subject to machining, such processes are featured by discontinuous chip formation. The paper describes the basic dependencies of discontinuous chip parameters on machining modes. This is a trial undertaken to introduce an explanation of how the basic factors of the cutting process influence over parameters of chip formation.

Morphological Analysis of Chip Generated by the Process of Turning on Bronze Aluminium Industry Used in Aeronautics via Electronic Scanning Microscopy

In machining processes the chip is considered the disposal of no interest and so little analysis of the morphology observed as the types and forms submitted. The machining does not equal the composition of the physical properties of metal forming, it involves forces or active and inactive stocks. The combination of parameters, conditions and variables of the machining is a means of speculating and trying to explain the phenomena. Such actions reflect directly on the wear of tooling, and structural integrity. The experimental study of machining is of essential importance for the theory of plasticity can not explain satisfactorily the observed phenomena. The speed and the deformations are very large in the machining process, compared with those treated in this theory. This material may reveal why this chip segmented nature which are characterized by continuous large deformation in narrow bands between segments with little or no strain in their interiors. This is a very different from the continuous chip. With the aid of a tool in the expanding area of technology and scientific processing and analysis of images could provide a better analysis of the chips. The goal of this study was to relate the microstructure of the chips of superalloy Aluminum Bronze (C 63020) with milling parameters used in the process of turning on a CNC lathe Nardini - LOGIC 175, in order to analyze the behavior of even through a mechanical process.

Hole Accuracy during Deep Hole Drilling for Hydraulic Cylinder Application

Deep-hole drilling is a process in which the hole length will be very high when compared to diameter of the drill hole (i.e. length to diameter ratio will be greater than 5). Drilling a deep hole with very high accuracy is difficult process. The current project is about the production of deep hole with the aim to produce a chip which is not a continuous chip and also not a powdery chip. These conditions can be attained by varying the spindle speed and the tool feed rate.