scholarly journals Finite Element Modeling of Brittle and Ductile Modes in Cutting of 3C-SiC

Crystals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1286
Author(s):  
Masud Alam ◽  
Liang Zhao ◽  
Napat Vajragupta ◽  
Junjie Zhang ◽  
Alexander Hartmaier

Machining of brittle ceramics is a challenging task because the requirements on the cutting tools are extremely high and the quality of the machined surface strongly depends on the chosen process parameters. Typically, the efficiency of a machining process increases with the depth of cut or the feed rate of the tool. However, for brittle ceramics, this easily results in very rough surfaces or even in crack formation. The transition from a smooth surface obtained for small depths of cut to a rough surface for larger depths of cut is called a brittle-to-ductile transition in machining. In this work, we investigate the mechanisms of this brittle-to-ductile transition for diamond cutting of an intrinsically brittle 3C-SiC ceramic with finite element modeling. The Drucker–Prager model has been used to describe plastic deformation of the material and the material parameters have been determined by an inverse method to match the deformation behavior of the material under nanoindentation, which is a similar loading state as the one occurring during cutting. Furthermore, a damage model has been introduced to describe material separation during the machining process and also crack initiation in subsurface regions. With this model, grooving simulations of 3C-SiC with a diamond tool have been performed and the deformation and damage mechanisms have been analyzed. Our results reveal a distinct transition between ductile and brittle cutting modes as a function of the depth of cut. The critical depth of cut for this transition is found to be independent of rake angle; however, the surface roughness strongly depends on the rake angle of the tool.

Author(s):  
Hardeep Singh ◽  
Anirban Bhattacharya ◽  
Ajay Batish

Powder mixed electric discharge machining (PMEDM) is one of the modern developments in electric discharge machining (EDM) process. In the present work, finite element modeling has been carried out considering randomly oriented multiple sparks during PMEDM. Transient thermal analysis is done to obtain temperature distribution, volume removal, and proportion of volume removed by melting and evaporation at different current, pulse on time and fraction of heat that enters to work piece. Gradually growing spark behavior and Gaussian distribution of heat source is used to simulate multiple craters. Temperature distribution along radial direction shows peak temperature at center of spark and thereafter a gradual decrease with increase in radial distance. Along depth direction temperature sharply decreases that forms wider craters with shallow depth in PMEDM. Peak temperature and volume removal increases with current more rapidly. Volume removal by melting is much higher than evaporation at lower current settings and with higher current almost equal amount of material is removed by melting and evaporation thus reducing the re-solidification of melted material. Current plays a significant role behind the contribution of material removal by evaporation followed by fraction of heat. Increase in pulse on duration increases the total volume of material removal however does not significantly increase the proportion of volume removal by vaporization.


2012 ◽  
Vol 505 ◽  
pp. 31-36 ◽  
Author(s):  
Moaz H. Ali ◽  
Basim A. Khidhir ◽  
Bashir Mohamed ◽  
A.A. Oshkour

Titanium alloys are desirable materials for aerospace industry because of their excellent combination of high specific strength, lightweight, fracture resistant characteristics, and general corrosion resistance. Therefore, the chip morphology is very important in the study of machinability of metals as well as the study of cutting tool wear. The chips are generally classified into four groups: continuous chips, chips with built-up-edges (BUE), discontinuous chips and serrated chips. . The chip morphology and segmentation play a predominant role in determining machinability and tool wear during the machining process. The mechanics of segmented chip formation during orthogonal cutting of titanium alloy Ti–6Al–4V are studied in detail with the aid of high-speed imaging of the chip formation zone. The finite element model of chip formation of Ti–6Al–4V is suggested as a discontinuous type chip at lower cutting speeds developing into a continuous, but segmented, chip at higher cutting speeds. The prediction by using finite-element modeling method and simulation process in machining while create chips formation can contribute in reducing the cost of manufacturing in terms of prolongs the cutting tool life and machining time saving.


2014 ◽  
Vol 1036 ◽  
pp. 259-264
Author(s):  
Nicușor Baroiu ◽  
Doina Boazu ◽  
Silviu Berbinschi ◽  
Virgil Teodor

The curved cutting edge determines a variable chip thickness that leads to various may energetically load along the cutting edge. For twist drill with curved cutting edges, the machining speed variation along the major cutting edge is significant. The points belong to the drills periphery work with an increased machining speed. The thick of the detached chip by these cutting zones downwards to the periphery, versus the thick corresponding to the zones at the drills axis, may leads, in some conditions, to the evenness of the energetically load along the cutting edge, with direct influence regarding the cutting tools wearing mechanism. In this paper are presented modeling with finite elements developed in the Ansys Workbench environment, regarding the energetically load and the temperature state along the cutting edge with variable working angle, characteristic for twist drills with curved cutting edges. The modeling was made comparative with the drill with straight lined cutting edges, for the same working conditions. In the same time, presents an experimental record of an actual process. It was recorded the temperature along the cutting edge with a variable working angle in a turning process with transversal feed. There are presented results of the finite element modeling and of the experiment that simulated the cutting process at drilling. The experimental results of the finite element modeling confirm the trend for temperature evenness along the cutting edge with variable working angle regarding the drills with straight-line cutting edge.


2003 ◽  
Vol 125 (3) ◽  
pp. 324-332 ◽  
Author(s):  
Y. Ohbuchi ◽  
T. Obikawa

A thermo-elastic-plastic finite element modeling of orthogonal cutting with a large negative rake angle has been developed to understand the mechanism and thermal aspects of grinding. A stagnant chip material ahead of the tool tip, which is always observed with large negative rake angles, is assumed to act like a stable built-up edge. Serrated chips, one of typical shapes of chips observed in single grain grinding experiment, form when analyzing the machining of 0.93%C carbon steel SK-5 with a rake angle of minus forty five or minus sixty degrees. There appear high and low temperature zones alternately according to severe and mild shear in the primary shear zone respectively. The shapes of chips depend strongly on the cutting speed and undeformed chip thickness; as the cutting speed or the undeformed chip thickness decreases, chip shape changes from a serrated type to a bulging one to a wavy or flow type. Therefore, there exists the critical cutting speed over which a chip can form and flow along a rake face for a given large negative rake angle and undeformed chip thickness.


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