shear zone in metal cutting

shear zone in metal cutting

Material behaviour in conditions similar to metal cutting : flow stress in the primary shear zone . the deformation zone in macro-cutting such as shear plane [1], parallel-sided shear zone [12], or curved shear zone [13]. Heat is produced due to the requirement of energy to shear the metal. This leads shear along the shear plane and cutting off the chip from the workpiece. Cutting tools commonly used in machining operations are never ideally sharp but always have some bluntness. The aim is to analyse how the tool geometry effects on the angle of the shear plane. Study of Damage distribution over the Primary Shear Zone in the Metal Cutting using Nanoindentation M. Saket Kashani*, V. Madhavan Department of Industrial and Manufacturing Engineering,,College of Engineering. Dr. V.K.jain, IIT Kanpur. The primary result is that the unique high strain, high strain rate, large free surface characteristics of the metal cutting process can result in qualitatively different deformation behavior across the shear zone. • Shear strength of Metal along shear plane is not affected by Normal stress. Forces in Metal Cutting •Equations can be derived to relate the forces that Combining the information on the deformation conditions in the primary shear zone with the measured constitutive behaviour, the flow stress of the metals in the primary shear zone is found. In this paper this spread of deformation away from its cause is studied from the viewpoint of how information about the imposed deformation is … The pros and cons of Trend model, Oxley model, and other models on mechanical behaviors of the second shear zone (SSZ) were reviewed. Experiments showed that the primary shear zone in cutting process wasn’t an absolutely parallel-sided zone. Cutting factors have much to do with sheet metal edges, for example a larger burnish zone would be indicative of a better edge surface quality. Dautzenberg. Shear zone models, a) single-shear plane model, b) parallel-sided shear plain model, c) pie-shaped shear plain model [14] In this paper, the aim is to concentrate the initial steps of cutting. Y1 - 2002. The approach is to quantify the modulus degradation via nanoindentation and use this as a measure of damage. The model included heat generation and temperature induced workpiece material property changes. AU - Dautzenberg, J.H. The bluntness can often be approximated as a circular radius between the flank and the rake faces of the tool. From measurements with this SHPB facility, it appeared that both strain rate and temperature have a considerable influence on the flow stress of metals. BibTex; Full citation; Abstract. The shear zone can be simplified to a shear plane (the Shear Plane theory). As the name suggests, Primary Shear Zone occurs surrounding the shear plane where the uncut chip (which is actually a part of work material) is converted into chip. To make an orthogonal cut in a metal work piece, a cutting tool applies a horizontal cutting force (fc) and a vertical force (ft). Assumptions:-• Orthogonal Cutting. Mechanics of Metal Cutting : Merchant's Circle Diagram; Co-efficient of Friction: Determination of stress, strain and strain rate; Measurement of shear angle; Thin Zone model: Lee and Shaffer's Relationship; Thick Zone model: Okushima and Hitomi Analysis Strategies to investigate the primary shear zone in metal cutting are largely based on chip root examinations. • Neglect energy of chip separation. The shear zone: About 80-85% heat is generated in this region. For all mathematical analysis this shear zone is treated as a plane and is called a shear-plane. When the cutting tool is forced against the work, the metal layer which is just ahead of tool is compressed. A plane strain extrusion of a short aluminum billet through straight-sided dies is presented and characteristic features of the formation of dead metal zone are observed. Jaspers and J.H. Poor edge quality. Orthogonal metal cutting . Question: Details pertaining to an orthogonal metal cutting process are given below. T1 - Material behaviour in conditions similar to metal cutting : flow stress in the primary shear zone. Temperature on metal cutting and cutting fluids 1/4/2013 Caused dimensional change in work piece , making of control dimensional accuracy difficult Heat generation in metal cutting 3 a) Region AB is Primary shear zone-plastic deformation ( ) b) Region BC is Secondary shear zone friction ( … PY - 2002. 15 zone rather than shear plane. b-) Force is circle to determine various forces acting in the cutting zone. Chip thickness ratio = 0.4; Undeformed thickness = 0.6 mm; Rake angle = +10° Cutting speed = 2.5 m/s; Mean thickness of primary shear zone 25 microns. Shear plane is locatedwhere least energy is required for shear. If the tool is forced further, a condition will be reached, in which the stress exceeds ultimate shear strength of the given work material. Cite . Fig.1: Sources of heat in metal cutting For example, in a typical study of machining mild steel at 30 m/min at about 750 deg of cutting temperature at tool-chip interface, the distribution of total energy developed at the shear zone is as follows Energy at chip – 60 percent Energy to … Secondary deformation zone (2) at the chip – tool interface where further heat is generated due to rubbing and / or shear. • Continuous chip without BUE. temperature in the cutting zone • in the shear zone • strain rates in machining operations are very high • along the tool-chip interface • Possibly where a dull tool rubs against the machined surface • Increased temperatures: • Adversely affects strength, hardness, and wear resistance of cutting tool During shearing, material initially deforms plastically in a very small region (H), causing a residual deformation.Afterwards, the upper blade penetrates the material forming a clean zone (I) where cutting is neat and regular. For same feed and depth of cut the force which shears the metal acts on smaller areas. The fraction of heat generated in the primary shear zone that is conducted into the workpiece is a key factor in the calculation of the shear plane temperature and in calculating the cutting forces based on material flow stress. The final application is a numerical simulation of the formation of a discontinuous chip in the orthogonal metal cutting. The deformation zone which produces the chip and finished surface in metal cutting extends away from the cutting tool into the workpiece. N2 - This paper is aimed at determining the flow stress in metal cutting. This paper presents an analytical method based on the unequal division shear-zone model to study the machining predictive theory. This paper is aimed at determining the flow stress in metal cutting. A new modified model based on the non-parallel primary shear zone is presented in this paper. BALERMANN metal container shear is applicable for cutting the metal shaped in different cross section like round, square, channel, angle, I shape, plate and various waste structural metal at cold state. 4 . Using this information and applying the principles of the theory of plasticity, heat transfer, and mechanics of the orthogonal metal cutting, a new distributed primary zone deformation model is developed to describe the distributions of the effective stress, effective strain, effective strain rate, and temperature in the primary shear zone. A large variety of deburring, chamfering, bending and other secondary processing operations may be employed to produce sheet metal product with edges of the desired geometry and quality. Sources and Causes of heat generation in Machining During machining, heat is generated at the cutting point from three sources, Primary shear zone (1) where the major part of the energy is converted into heat. Abstract In our effort to develop metal cutting as a high strain rate test, we are interested in mapping the damage distribution over the It brings convenience to the baling, storage and transportation of scrap metal materials, also offers qualified furnace charge for smelting plant. The region between the lines AB and CD is called shear-zone. The amount of generated heat strongly depends on the process forces and, thus, on the shear flow stress, which, inter alia, They are as follows. After passing out the shear-zone, the deformed metal slides along the tool face due to the velocity of the cutting tool. - The heat generated in metal cutting operation is generated in three individual regions. Note that the resultant forces, R, must be collinear to balance the forces. Anyone who is even casually involved with a machining process knows that cutting tools generate large amounts of heat. ISE 316-Manufacturing Processes Engineering Higher shear plane angle means smaller shear plane which means lower shear force Result: lower cutting forces, power, temperature, all of which mean easier machining Figure 21.12 ‑ Effect of shear plane angle : (a) higher with a resulting lower shear plane area; (b) smaller with a corresponding larger shear plane area. In our effort to develop metal cutting as a high strain rate test, we are interested in mapping the damage distribution over the primary shear zone (PSZ). Cutting occurs using a shearing action in a shear zone. The rake angle of the tool is . The direction of chip flow is perpendicular to the cutting edge. By S.P.F.C. a-) Forces is acting on a cutting tool in two-dimensional cutting. The chip coils in a tight flat spiral . HEAT GENERATION IN CUTTING TOOLS . The proposed model only requires workpiece material properties and cutting conditions to predict the cutting forces during the orthogonal cutting process. 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