Effect of Severe Plastic Deformation in Machining Elucidated via Rate-Strain-Microstructure Mappings

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
S. Shekhar ◽  
S. Abolghasem ◽  
S. Basu ◽  
J. Cai ◽  
M. R. Shankar
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Strain Rate ◽  
Deformation Zone ◽  
Fine Grained ◽  
Orthogonal Machining ◽  
Deformation Parameters ◽  
Strain And Strain Rate ◽  
One To One ◽  
Surface Microstructures

Machining induces severe plastic deformation (SPD) in the chip and on the surface to stimulate dramatic microstructural transformations which can often result in a manufactured component with a fine-grained surface. The aim of this paper is to study the one-to-one mappings between the thermomechanics of deformation during chip formation and an array of resulting microstructural characteristics in terms of central deformation parameters–strain, strain-rate, temperature, and the corresponding Zener–Hollomon (ZH) parameter. Here, we propose a generalizable rate-strain-microstructure (RSM) framework for relating the deformation parameters to the resulting deformed grain size and interface characteristics. We utilize Oxley’s model to calculate the strain and strain-rate for a given orthogonal machining condition which was also validated using digital imaging correlation-based deformation field characterization. Complementary infrared thermography in combination with a modified-Oxley’s analysis was utilized to characterize the temperature in the deformation zone where the SPD at high strain-rates is imposed. These characterizations were utilized to delineate a suitable RSM phase-space composed of the strain as one axis and the ZH parameter as the other. Distinctive one-to-one mappings of various microstructures corresponding to an array of grain sizes and grain boundary distributions onto unique subspaces of this RSM space are shown. Building on the realization that the microstructure on machined surfaces is closely related to the chip microstructure derived from the primary deformation zone, this elucidation is expected to offer a reliable approach for controlling surface microstructures from orthogonal machining.

Interactive Effects of Strain, Strain-Rate and Temperatures on Microstructure Evolution in High Rate Severe Plastic Deformation

2011 ◽  
Vol 702-703 ◽  
pp. 139-142
Author(s):  
Shashank Shekhar ◽  
S. Abolghashem ◽  
S. Basu ◽  
J. Cai ◽  
M. Ravi Shankar
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Strain Rate ◽  
Interactive Effect ◽  
Material Behavior ◽  
High Rate ◽  
Interactive Effects ◽  
Continuous Dynamic Recrystallization ◽  
Deformation Parameters ◽  
Strain And Strain Rate

During high rate severe plastic deformation (HRSPD), strain and strain-rate are not the only external factors that determine microstructural transformations in materials, temperature-rise due to heat generation from deformation processes, also plays an important role. Temperature may influence the microstructure directly by controlling grain growth kinetics and it may also have an indirect effect through the interactive effect on material behavior, which in turn, influences strain and strain-rate parameters. This complex thermomechanics of HRSPD can lead to myriad of microstructure and consequently, material properties and phenomenon. These deformation parameters can be utilized as a ‘fingerprint’ for the resulting microstructure, and the properties and phenomenon related to it. Here, we capture some of these microstructural transformations by relating grain and sub-grain sizes, to the deformation parameters. In doing so, we find evidence of continuous dynamic recrystallization operative under these HRSPD conditions, where the interplay of strain, strain rate and temperatures offer varying degrees of multimodality in the grain-size distributions.

scholarly journals Dynamic High Pressure Torsion (DHPT)—A Novel Method for High Strain Rate Severe Plastic Deformation

Proceedings ◽  
2018 ◽  
Vol 2 (8) ◽  
pp. 493 ◽  
Author(s):  
Harishchandra Lanjewar ◽  
Leo Kestens ◽  
Patricia Verleysen
Keyword(s):  
Plastic Deformation ◽  
High Pressure ◽  
Severe Plastic Deformation ◽  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
High Pressure Torsion ◽  
Pure Aluminum ◽  
High Deformation ◽  
Fine Grained

Metals with a fine-grained microstructure have exceptional mechanical properties. Severe plastic deformation (SPD) is one of the most successful ways to fabricate ultrafine-grained (UFG) and nanostructured (NC) materials. Most of the SPD techniques employ very low processing speeds. However, the lowest steady-state grain size which can be obtained by SPD is considered to be inversely proportional with the strain rate at which the severe deformation is imposed. In order to overcome this limitation, methods operating at higher rates have been envisaged and used to study the fragmentation process and the properties of the obtained materials. However, almost none of these methods, employ hydrostatic pressures which are needed to prevent the material from failing at high deformation strains. As such, their applicability is limited to materials with a high intrinsic ductility. Additionally, in some methods the microstructural changes are limited to the surface layers of the material. To circumvent these restrictions, a novel facility has been designed and developed which deforms the material at high strain rate under high hydrostatic pressures. Using the facility, commercially pure aluminum was processed and analysis of the deformed material was performed. The microstructure evolution in this material was compared with that observed in static high pressure torsion (HPT) processed material.

Velocity and Strain Distributions in Two-Dimensional Orthogonal Machining

2004 ◽  
Author(s):  
Seongeyl Lee ◽  
Jihong Hwang ◽  
M. Ravi Shankar ◽  
Srinivasan Chandrasekar ◽  
W. Dale Compton
Keyword(s):  
Strain Rate ◽  
Deformation Zone ◽  
High Speed ◽  
Imaging System ◽  
Large Strain ◽  
Cutting Edge ◽  
Two Dimensional ◽  
Intimate Contact ◽  
Orthogonal Machining ◽  
Strain And Strain Rate

A study has been made of the primary deformation zone and tool-chip interface in two-dimensional (plane strain) orthogonal machining of commercially pure metals. The use of a high-speed, Charge-Coupled Device (CCD) imaging system in conjunction with an optically transparent, sapphire cutting tool, has enabled characteristics of the deformation field such as velocity, strain, and material flow, to be obtained at high spatial and temporal resolution. The velocity distributions in the primary deformation zone and along the tool rake face have been obtained by applying a Particle Image Velocimetry (PIV) technique to sequences of high-speed images of the chip-tool interface taken through the transparent tool, and of the primary deformation zone recorded from a side of the workpiece. A procedure is presented and demonstrated for determining the strain and strain rate distributions in the primary deformation zone. The measurements have provided data about the variations of strain, strain rate and velocity, in and around the cutting edge and primary deformation zone; confirmed the existence of a region of retarded sliding in the region of intimate contact between tool and chip; and highlighted the occurrence of a region of dead metal ahead of the cutting edge when cutting with a negative rake angle tool. The implications of these results to the use of machining as a controlled test for studying very large strain deformation, and for estimating material properties under extreme conditions of deformation are discussed.

Severe Plastic Deformation Technologies for Ultra Fine Grained Alloys

2007 ◽  
Vol 23 ◽  
pp. 33-38
Author(s):  
Traian Canta ◽  
Dan Frunză
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Strain Rate ◽  
Grain Refinement ◽  
Equal Channel Angular Extrusion ◽  
Contact Friction ◽  
Channel Geometry ◽  
Fine Grained ◽  
Deformation Processes

Some of new severe plastic deformation processes as equal channel angular extrusion, and strip shearing are presented as very efficient techniques for grain refinement. Channel geometry, contact friction, strain rate and multi-pass processing versus microstructure and mechanical properties are shown.

Reference values for two-dimensional myocardial strain echocardiography of the left ventricle in healthy children

2019 ◽  
Vol 29 (3) ◽  
pp. 325-337
Author(s):  
Laurens P. Koopman ◽  
Bas Rebel ◽  
Devi Gnanam ◽  
Mirthe E. Menting ◽  
Willem A. Helbing ◽  
...  
Keyword(s):  
Left Ventricle ◽  
Strain Rate ◽  
Longitudinal Strain ◽  
Circumferential Strain ◽  
Left Ventricular ◽  
Myocardial Deformation ◽  
Healthy Children ◽  
Deformation Parameters ◽  
Strain And Strain Rate ◽  
Echocardiographic Parameters

AbstractBackgroundMyocardial deformation by speckle tracking echocardiography provides additional information on left ventricular function. Values of myocardial deformation (strain and strain rate) depend on the type of ultrasound machine and software that is used. Normative values for QLAB (Philips) are scarce, especially for children. It is important to evaluate the influence of age and body size on myocardial deformation parameters, since anthropometrics strongly influence many standard echocardiographic parameters. The aim of this study was to provide comprehensive normal values for myocardial deformation of the left ventricle using a Philips platform and to evaluate the association with anthropometric and standard echocardiographic parameters.MethodsHealthy children between 1 and 18 years of age were prospectively examined using a standard echocardiographic protocol. Short-axis and apical four-chamber, two-chamber, and three-chamber views were used to measure peak systolic circumferential and longitudinal strain and systolic and early diastolic strain rate of the left ventricle using dedicated software.ResultsA total of 103 children were included with a mean age of 10.8 and inter-quartile range 7.3–14.3 years. Global circumferential strain values (±SD) were −24.2±3.5% at basal, −25.8±3.5% at papillary muscle, and −31.9±6.2% at apex levels. Global left ventricular longitudinal strain values were −20.6±2.6% in apical four-chamber view, −20.9±2.7% in apical two-chamber, and −21.0 ±2.7% in apical three-chamber. Age was associated with longitudinal strain, longitudinal systolic and early diastolic strain rate, but not with circumferential strain.ConclusionsNormal values for left ventricular deformation parameters in children are obtained using a Philips platform. Age partly explains normal variation of strain and strain rate.

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