Effects of Accelerated Tests on Shear Flow Stress in Machining

1987 ◽  
Vol 109 (3) ◽  
pp. 206-212 ◽  
Author(s):  
V. K. Jain ◽  
B. K. Gupta
Keyword(s):  
Flow Stress ◽  
Shear Flow ◽  
Shear Strain ◽  
Tool Material ◽  
Interface Temperature ◽  
Accelerated Tests ◽  
Instantaneous Values ◽  
Longitudinal Turning ◽  
Materials Behavior ◽  
Shear Flow Stress

Facing and taper turning tests (also known as accelerated cutting tests) are commonly used for the evaluation of machinability of materials. Of late, it has been reported that instantaneous values of tool-chip interface temperature, tool wear, shear angle, etc, in longitudinal turning are different from the corresponding values in accelerated cutting. This effect has been attributed to shear strain acceleration phenomenon. Materials behavior during accelerated cutting changes in a manner different than that in longitudinal turning. To test this hypothesis, experiments have been conducted using HSS as tool material and mild steel as work material. It has been concluded that shear flow stress during accelerated cutting is governed by shear strain acceleration and its governing parameters. Shear flow stress value is highest during facing, lowest in taper turning and in between the two during longitudinal turning.

Shear-Zone Size, Compressive Stress, and Shear Strain in Metal-Cutting and Their Effects on Mean Shear-Flow Stress

1960 ◽  
Vol 82 (1) ◽  
pp. 79-86 ◽  
Author(s):  
Dimitri Kececioglu
Keyword(s):  
Flow Stress ◽  
Shear Flow ◽  
Size Effect ◽  
Shear Strain ◽  
Shear Zone ◽  
Compressive Stress ◽  
Metal Cutting ◽  
Zone Size ◽  
Wide Range ◽  
Shear Flow Stress

A relationship for the calculation of the shear-zone size is given. The shear-zone size, when machining SAE 1015, 118-Bhn seamless steel tubing under a wide range of cutting conditions, is found to vary from 0.95 × 10−6 in.3 to 61.5 × 10−6 in.3 The mean shear-flow stress is found to increase significantly with a decrease in the shear-zone size and with an increase in the compressive stress in the shear zone. It is concluded that the only size effect in metal-cutting is the shear-zone size effect, and that no separate depth-of-cut size effect should be sought. An apparent decrease in the shear-flow stress with an increase in the true, mean shear strain in the shear zone is observed, and this behavior is explained.

The Effect of Workpiece Hardness and Cutting Speed on the Machinability of AISI H13 Hot Work Die Steel When Using PCBN Tooling

2002 ◽  
Vol 124 (3) ◽  
pp. 588-594 ◽  
Author(s):  
Eu-Gene Ng ◽  
David K. Aspinwall
Keyword(s):  
Flow Stress ◽  
Shear Flow ◽  
Shear Zone ◽  
Cutting Speed ◽  
Chip Morphology ◽  
Die Steel ◽  
Aisi H13 ◽  
Hot Work Die ◽  
Cutting Speeds ◽  
Shear Flow Stress

When machining hardened steel (⩾45 HRC) with polycrystalline cubic boron nitride (PCBN) tooling, the cutting speeds used produce high temperatures in the primary shear zone, which are sufficient to plasticize the workpiece. The paper initially reviews the effect of workpiece hardness and cutting speed on chip formation, workpiece surface integrity and cutting forces. Equations are detailed for determining the primary shear zone temperature, the proportion of heat conducted into the workpiece and the shear flow stress. Following on from this, experimental work is presented involving the orthogonal machining of AISI H13 hot work die steel with PCBN tooling. Tests were carried out over a range of cutting speeds with workpieces of different hardness, in order to provide cutting force, shear angle, chip morphology and primary shear zone thickness data. The shear flow stress decreased with increasing cutting speed and/or workpiece hardness. With the AISI H13 heat treated to 49±1 HRC, the stress magnitude changed more significantly with cutting speed and the proportion of heat conducted away from the workpiece approached 99 percent at 200 m/min. Shear localized chips were produced with white unetched layers due to intense heat generation followed by rapid cooling.

Minimum work as a possible criterion for determining the frictional conditions at the tool/chip interface in machining

1976 ◽  
Vol 282 (1310) ◽  
pp. 565-584 ◽  
Keyword(s):  
Flow Stress ◽  
Shear Flow ◽  
Plastic Zone ◽  
Approximate Theory ◽  
Angle Of Friction ◽  
Average Coefficient ◽  
Average Shear ◽  
Work Done ◽  
Minimum Work ◽  
Shear Flow Stress

An approximate theory of machining is described in which the average shear flow stress in the plastic zone in the chip adjacent to the tool/chip interface, which is allowed to vary with strain rate and temperature, is used as the friction parameter and this is shown to be far more effective than the normally used average coefficient (or angle) of friction. It is proposed that the average thickness of the tool/chip interface plastic zone is determined by a minimum work criterion, its value being such that for given cutting conditions the average shear flow stress within the plastic zone will be minimized, thus minimizing both the frictional and total work done in chip formation. A comparison is made between results predicted by assuming minimum work and experimental results.

The Effect of Workpiece Hardness and Cutting Speed on the Machinability of AISI H13 Hot Work Die Steel When Using PCBN Tooling

1999 ◽  
Author(s):  
Eu-Gene Ng ◽  
David K. Aspinwall
Keyword(s):  
Flow Stress ◽  
Shear Flow ◽  
Shear Zone ◽  
Cutting Speed ◽  
Chip Morphology ◽  
Die Steel ◽  
Aisi H13 ◽  
Hot Work Die ◽  
Cutting Speeds ◽  
Shear Flow Stress

Abstract When machining hardened steel (≥ 45 HRC) with polycrystalline cubic boron nitride (PCBN) tooling, the cutting speeds used produce high temperatures in the primary shear zone, which are sufficient to plasticise the workpiece. The paper initially reviews the effect of workpiece hardness and cutting speed on chip formation, workpiece surface integrity and cutting forces. Equations are detailed for determining the primary shear zone temperature, the proportion of heat conducted into the workpiece and the shear flow stress. Following on from this, experimental work is presented involving the orthogonal machining of AISI H13 hot work die steel with PCBN tooling. Tests were carried out over a range of cutting speeds with workpieces of different hardness, in order to provide cutting force, shear angle, chip morphology and primary shear zone thickness data. The shear flow stress decreased with increasing cutting speed and/or workpiece hardness. With the AISI H13 heat treated to 49±1 HRC, the stress magnitude changed more significantly with cutting speed and the proportion of heat conducted away from the workpiece approached 99% at 200 m/min. Shear localised chips were produced with white unetched layers due to intense heat generation followed by rapid cooling.

Effects of Machining Parameters on the Microhardness of Chips

1989 ◽  
Vol 111 (3) ◽  
pp. 220-228 ◽  
Author(s):  
V. K. Jain ◽  
S. Kumar ◽  
G. K. Lal
Keyword(s):  
Shear Strain ◽  
Cutting Tools ◽  
Cutting Speed ◽  
Shear Angle ◽  
Interface Temperature ◽  
Machining Parameters ◽  
Machining Conditions ◽  
Temperature Shear ◽  
Longitudinal Turning ◽  
Microhardness Tester

It has been found that the shear strain acceleration governs the machining parameters like tool-chip interface temperature, shear angle, tool wear, etc. It is therefore speculated that microhardness of the chips for the same machining conditions but for different shear strain accelerations would be different. To test this hypothesis, experiments have been conducted using mild steel as work material and cemented carbide bits as cutting tools. Experiments were performed in two ways: longitudinal turning and accelerated cutting. Chips were collected at the same machining conditions but at different shear strain acceleration. Microhardness of the chips has been measured using the Leibtz-microhardness tester and the results have been analyzed using a computer program CADEAG-1. Using the responses (i.e., microhardness), mathematical models have been evolved. Effects of different parameters (cutting speed, feed, etc.) on the microhardness of the chips in all the three cases (i.e., longitudinal turning, facing, and taper turning) have been studied. It has been concluded that the microhardness of the chips obtained during accelerated cutting is governed by the shear strain acceleration and its governing parameters.

Finite Element Modeling of Diamond Indentation Creep in MgO

2011 ◽  
Vol 393-395 ◽  
pp. 106-109
Author(s):  
Jin Hua Hu ◽  
Leslie Henshall
Keyword(s):  
Activation Energy ◽  
Finite Element ◽  
Flow Stress ◽  
Low Temperature ◽  
Single Crystal ◽  
Creep Model ◽  
Dislocation Creep ◽  
Indentation Creep ◽  
Low Temperature Creep ◽  
Shear Flow Stress

The modified dislocation creep model and the power law breakdown creep model were proposed to be used in the indentation creep deformation analyses for single crystal MgO at low temperature varying from 293K to 873K. A FE indentation creep modeling procedure was proposed and implemented. The activation energy and the shear flow stress for low temperature creep in single crystal MgO were predicted based on the analytical indentation creep analyses.

scholarly journals Dynamics of a large population of red blood cells under shear flow

2019 ◽  
Vol 864 ◽  
pp. 408-448 ◽  
Author(s):  
C. Minetti ◽  
V. Audemar ◽  
T. Podgorski ◽  
G. Coupier
Keyword(s):  
Flow Stress ◽  
Shear Flow ◽  
Red Blood Cells ◽  
Blood Cells ◽  
Rate Increase ◽  
Large Population ◽  
Experimental Studies ◽  
Hysteresis Loops ◽  
Fluid Viscosity ◽  
Characteristic Parameters

An exhaustive description of the dynamics under shear flow of a large number of red blood cells in a dilute regime is proposed, which highlights and takes into account the dispersion in cell properties within a given blood sample. Physiological suspending fluid viscosity is considered, a configuration surprisingly seldom considered in experimental studies, as well as a more viscous fluid that is a reference in the literature. Stable and unstable flipping motions well described by Jeffery orbits or modified Jeffery orbits are identified, as well as transitions to and from tank-treading motion in the more viscous suspending fluid case. Hysteresis loops upon shear rate increase or decrease are highlighted for the transitions between unstable and stable orbits as well as for the transition between flipping and tank-treading. We identify which of the characteristic parameters of motion and of the transition thresholds depend on flow stress only or also on suspending fluid viscosity.

Deformation Behavior of Natural Wood Having Hierarchical Structure Under A Compression State

2011 ◽  
Vol 1304 ◽  
Author(s):  
Tsunehisa MIKI ◽  
Hiroyuki SUGIMOTO ◽  
Kozo KANAYAMA
Keyword(s):  
Plastic Deformation ◽  
Flow Stress ◽  
Hierarchical Structure ◽  
Deformation Behavior ◽  
Elevated Temperatures ◽  
Longitudinal Direction ◽  
Metallic Materials ◽  
The Hierarchical Structure ◽  
Natural Wood ◽  
Shear Flow Stress

ABSTRACTA large deformation of bulk wood using slipping between the wood cells has been found just like a plastic deformation generated by slip band in metallic materials. This phenomenon is caused by the hierarchical structure of the wood cell, and the intercellular layer becomes selectively softened in moistened states of wood. In such conditions, bulk wood subject to compression at elevated temperatures can easily be deformed perpendicular to the longitudinal direction of the cells by shear flow stress after being collapsed.

Machinability Assessment in High Speed Turning of High Strength Temperature Resistant Superalloys

2019 ◽  
Vol 18 (04) ◽  
pp. 595-623
Author(s):  
Raju Pawade ◽  
Avinash Khadtare ◽  
Dhanashree Dhumal ◽  
Vishal Wankhede
Keyword(s):  
Surface Roughness ◽  
Shear Strain ◽  
Cutting Force ◽  
Compression Ratio ◽  
Cutting Tool ◽  
Cutting Speed ◽  
Tool Material ◽  
High Strength ◽  
Inconel 600 ◽  
Chip Compression Ratio

The paper discusses the effect of cutting parameters and cutting tool material on chip compression ratio, cutting forces and surface roughness in turning of high strength temperature resistant superalloys (HSTR). The experiments were performed in dry cutting environment on precision CNC lathe with fixed depth of cut of 0.5[Formula: see text]mm. Analytical model is developed to determine chip segmentation frequency, shear angle and shear strain and it is correlated with the machining parameters. The machinability of the selected superalloys is assessed in terms of cutting force, chip compression ratio and surface roughness. It is found from the experimental analysis cutting force magnitude is less at higher cutting speed for all the superalloys. Chip compression ratio is found maximum in case of Inconel 718 due to precipitation hardening of alloy and followed by Inconel 600 and Inconel 800. The chip segmentation frequency is high at lower cutting speed for Inconel 600 due significant strain hardening. Serrated chips are produced during machining of three selected superalloys and it is found that serrated tooth spacing decreases with cutting speed. Shear plane angle increases on cutting speed increases which effect tool workpiece contact length during machining resulted thin, short and snarled chips was produced. From analytical modeling it shows that shear strain decreases with cutting speed which indicate that at higher cutting speed material deformed elastically than plastically. The effect of cutting tool material is observed on the surface roughness. The better surface finish is obtained with coated carbide inserts as compared to ceramic inserts for all the selected superalloys. However, Inconel 800 shows higher surface roughness due to combination of (Ni–Cr–Fe) alloying element which is responsible for carburization of surface layer during machining.

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