Effect of Low-Frequency Modulation on Deformation and Material Flow in Cutting of Metals

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Ho Yeung ◽  
Yang Guo ◽  
James B. Mann ◽  
W. Dale Compton ◽  
Srinivasan Chandrasekar
Keyword(s):  
Frequency Modulation ◽  
Chip Formation ◽  
Material Flow ◽  
High Speed ◽  
Surface Deformation ◽  
Low Frequency ◽  
High Speed Imaging ◽  
Machining Processes ◽  
Asperity Contacts ◽  
2D System

The deformation field, material flow, and mechanics of chip separation in cutting of metals with superimposed low-frequency modulation (<1000 Hz) are characterized at the mesoscale using high-speed imaging and particle image velocimetry (PIV). The two-dimensional (2D) system studied involves a sharp-wedge sliding against the workpiece to remove material, also reminiscent of asperity contacts in sliding. A unique feature of the study is in situ mapping of material flow at high resolution using strain fields and streaklines and simultaneous measurements of tool motions and forces, such that instantaneous forces and kinematics can be overlaid onto the chip formation process. The significant reductions in specific energy obtained when cutting with modulation are shown to be a consequence of discrete chip formation with reduced strain levels. This strain reduction is established by direct measurements of deformation fields. The results have implications for enhancing sustainability of machining processes and understanding surface deformation and material removal in wear processes.

A Comparative Study of Energy and Material Flow in Modulation-Assisted Machining and Conventional Machining

2014 ◽  
Author(s):  
Ho Yeung ◽  
Yang Guo ◽  
James B. Mann ◽  
W. Dale Compton ◽  
Srinivasan Chandrasekar
Keyword(s):  
Chip Formation ◽  
Material Flow ◽  
High Speed ◽  
Unique Feature ◽  
Low Frequency ◽  
Ductile Metals ◽  
Simultaneous Measurements ◽  
Formation Zone ◽  
Conventional Machining

A study has been made of deformation, forces and energy in modulation-assisted machining (MAM), wherein chip formation occurs in the presence of a controlled, low-frequency modulation superimposed on to the machining. A unique feature of the study is the use of high speed in situ imaging and image analysis to map material flow in the chip formation zone at high resolution; and simultaneous measurements of tool motions and forces, such that the instantaneous forces can be overlaid onto the chip formation process. The measurements show that the observed significant reductions in specific energy in MAM relative to conventional machining, when cutting ductile metals such as copper and Al 6061T6, are a consequence of chip formation with reduced strain levels in MAM. Additional insights into the chip formation are obtained by examining the effects of a chip aspect ratio parameter.

Primary Chip Formation During an Extremely High Speed Micromachining Process

2004 ◽  
Author(s):  
M. J. Jackson ◽  
C. H. Hamme ◽  
L. J. Hyde ◽  
G. M. Robinson ◽  
H. Sein ◽  
...  
Keyword(s):  
Shear Zone ◽  
Chip Formation ◽  
High Speed ◽  
Cutting Tools ◽  
Machining Processes ◽  
Orthogonal Machining ◽  
Shear Process ◽  
Order Of Magnitude ◽  
Cutting Zone ◽  
Secondary Shear Zone

The advent of nanotechnology has created a demand for precision-machined substrates so that ‘bottom-up’ nanomanufacturing processes can be used to produce functional products at the nanoscale. However, machining processes must be scaled down by an order of magnitude that requires very stable desktop machine tools to produce precision-machined substrates using cutting tools that are rotated at speeds in excess of one million revolutions per minute. Therefore, the mechanics of chip formation at this scale are critical when one considers the effect of chip formation on the generation of surface roughness on the substrate. The tight curl of a machined chip in orthogonal machining appears to be part of the primary shear process. It is also known that transient tight curl occurs before a secondary shear zone develops ahead of the removal of the chip from the cutting zone. However, continuum models predict that curled chips incorporate stresses due to the establishment of a secondary shear zone. A model is presented in terms of the heterogeneous aspects of continuous chip formation, which shows very good agreement with experimental data.

In Situ Analysis of Deformation Mechanics of Constrained Cutting Towards Enhanced Material Removal

2019 ◽  
Author(s):  
Yang Guo ◽  
Jisheng Chen ◽  
Amr Saleh
Keyword(s):  
Free Surface ◽  
Surface Finish ◽  
Simple Shear ◽  
Chip Formation ◽  
Material Removal ◽  
High Speed ◽  
Image Correlation ◽  
High Speed Imaging ◽  
Deformation Mechanics

Abstract Chip formation in conventional cutting occurs by deformation that is only partially bounded by the cutting tool. The unconstrained free surface is a complication in determining the deformation of chip formation. The constrained cutting employs a constraining tool in the cutting process to confine the otherwise free surface and enable direct control of the chip formation deformation. A study has been made on the deformation mechanics of plane-strain constrained cutting using high speed imaging and digital image correlation (DIC) methods. For different constrained levels (including unconstrained free cutting), material flow of chip formation is directly observed; strain rate and strain in the chip as well as the subsurface region are quantified; cutting forces are measured; and surface finish are examed. The study shows that chip formation in constrained cutting can occur in two different deformation modes, i.e., simple shear and complex extrusion, depending on the constrained level. Constrained cutting in simple shear regime can reduce strain, reduce cutting force and energy, and improve surface finish compared to free cutting, therefore it is more efficient for material removal than free cutting. Constrained cutting in the complex extrusion regime imposes a significant amount of surface / subsurface deformation and consumes a very high cutting energy, and therefore is not suitable for material removal. Furthermore, the mechanics of chip formation in both free cutting and constrained cutting, especially the roles played by the free surface and the constraining tool, are discussed.

scholarly journals Vocal state change through laryngeal development

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Yisi S. Zhang ◽  
Daniel Y. Takahashi ◽  
Diana A. Liao ◽  
Asif A. Ghazanfar ◽  
Coen P. H. Elemans
Keyword(s):  
Motor Control ◽  
High Speed ◽  
Neural Circuits ◽  
Low Frequency ◽  
Vocal Folds ◽  
Vocal Development ◽  
High Speed Imaging ◽  
State Changes ◽  
Material Tests ◽  
Excised Larynx

Abstract Across vertebrates, progressive changes in vocal behavior during postnatal development are typically attributed solely to developing neural circuits. How the changing body influences vocal development remains unknown. Here we show that state changes in the contact vocalizations of infant marmoset monkeys, which transition from noisy, low frequency cries to tonal, higher pitched vocalizations in adults, are caused partially by laryngeal development. Combining analyses of natural vocalizations, motorized excised larynx experiments, tensile material tests and high-speed imaging, we show that vocal state transition occurs via a sound source switch from vocal folds to apical vocal membranes, producing louder vocalizations with higher efficiency. We show with an empirically based model of descending motor control how neural circuits could interact with changing laryngeal dynamics, leading to adaptive vocal development. Our results emphasize the importance of embodied approaches to vocal development, where exploiting biomechanical consequences of changing material properties can simplify motor control, reducing the computational load on the developing brain.

Application of Proper Orthogonal Decomposition to High Speed Imaging for the Study of Combustion Oscillations

2017 ◽  
Author(s):  
Siddhartha Gadiraju ◽  
Suhyeon Park ◽  
David Gomez-Ramirez ◽  
Srinath V. Ekkad ◽  
K. Todd Lowe ◽  
...  
Keyword(s):  
Proper Orthogonal Decomposition ◽  
High Speed ◽  
Equivalence Ratio ◽  
Flame Structure ◽  
Low Frequency ◽  
Orthogonal Decomposition ◽  
Pressure Measurements ◽  
High Speed Imaging ◽  
Flame Structures ◽  
Proper Orthogonal

The flame structure and characteristics generated by an industrial low emission, lean premixed, fuel swirl nozzle were analyzed for understanding combustion oscillations. The experimental facility is located at the Advanced Propulsion and Power Laboratory (APPL) at Virginia Tech. The experiments were carried out in a model optical can combustor operating at atmospheric pressures. Low-frequency oscillations (<100 Hz) were observed during the reaction as opposed to no reaction, cold flow test cases. The objective of this paper is to understand the frequency and magnitude of oscillations due to combustion using high-speed imaging and associate them with corresponding structure or feature of the flame. Flame images were obtained using a Photron Fastcam SA4 high-speed camera at 500 frames per second. The experiments were conducted at equivalence ratios of 0.65, 0.75; different Reynolds numbers of 50K, 75K; and three pilot fuel to main fuel ratios of 0%, 3%, 6%. In this study, Reynolds number was based on the throat diameter of the fuel nozzle. Since the time averaged flame images are not adequate representation of the flame structures, proper orthogonal decomposition (POD) was applied to the flame images to extract the dominant features. The spatiotemporal dynamics of the images can be decomposed into their constituent modes of maximum spatial variance using POD so that the dominant features of the flame can be observed. The frequency of the dominant flame structures, as captured by the POD modes of the flame acquisitions, were consistent with pressure measurements taken at the exit of the combustor. Thus, the oscillations due to combustion can be visualized using POD. POD was further applied to high-speed images taken during instabilities. Specifically, the instabilities discussed in this paper are those encountered when the equivalence ratio is reduced to the levels approaching lean blowout (LBO). As the equivalence ratio is reduced to near blowout regime, it triggers low-frequency high amplitude instabilities. These low-frequency instabilities are visible as the flapping of the flame. The frequencies of the dominant POD modes are consistent with pressure measurements recorded during these studies.

scholarly journals The dynamics of centromere motion through the metaphase-to-anaphase transition reveal a centromere separation order

2019 ◽  
Author(s):  
Jonathan W. Armond ◽  
Katie L. Dale ◽  
Nigel J. Burroughs ◽  
Andrew D. McAinsh ◽  
Elina Vladimirou
Keyword(s):  
Chromosome Segregation ◽  
High Speed ◽  
Daughter Cell ◽  
Mitotic Chromosome ◽  
Low Frequency ◽  
The Other ◽  
Bayesian Modelling ◽  
High Speed Imaging ◽  
Chromosome Dynamics ◽  
Sister Chromatids

AbstractDuring cell division, chromosomes align at the equator of the cell before sister chromatids separate to move to each daughter cell during anaphase. We use high-speed imaging, Bayesian modelling and quantitative analysis to examine the regulation of centromere dynamics through the metaphase-to-anaphase transition. We find that, contrary to the apparent instantaneous separation seen in low-frequency imaging, centromeres separate asynchronously over 1-2 minutes. The timing of separations negatively correlates with the centromere intersister distance during metaphase, which could potentially be explained by variable amounts of cohesion at centromeres. Depletion of condensin I increases this asynchrony. Depletion of condensin II, on the other hand, abolishes centromere metaphase oscillations and impairs centromere speed in anaphase. These results suggest that condensin complexes have broader direct roles in mitotic chromosome dynamics than previously believed and may be crucial for the regulation of chromosome segregation.

In Situ Analysis of Deformation Mechanics of Constrained Cutting Toward Enhanced Material Removal

2019 ◽  
Vol 142 (2) ◽  
Author(s):  
Yang Guo ◽  
Jisheng Chen ◽  
Amr Saleh
Keyword(s):  
Free Surface ◽  
Surface Finish ◽  
Simple Shear ◽  
Chip Formation ◽  
Material Removal ◽  
High Speed ◽  
Image Correlation ◽  
High Speed Imaging ◽  
Chip Flow ◽  
Deformation Mechanics

Abstract Chip formation in conventional cutting occurs by deformation that is only partially bounded by the cutting tool. The unconstrained free surface makes it difficult to determine and to control the deformation of chip formation. The constrained cutting employs a constraining tool in the cutting process to confine the otherwise free surface and enable direct control of the chip formation deformation. The presented work is a study of the deformation mechanics of plane strain constrained cutting using high-speed imaging and digital image correlation (DIC) methods. For different constrained levels (including unconstrained free cutting), the material flow of chip formation is directly observed; the strain rate and strain in the chip as well as the subsurface region are quantified; cutting forces are measured; and surface finish is examined. The study shows that chip formation in constrained cutting can occur in two different deformation modes, i.e., simple shear and complex extrusion, depending on the constrained level. Constrained cutting in the simple shear regime can reduce strain, reduce cutting force and energy, and improve surface finish compared to free cutting; therefore, it is more efficient for material removal than free cutting. Constrained cutting in the extrusion regime imposes a high resistance to the chip flow and causes a significant amount of subsurface deformation, and therefore is not suitable for material removal. Furthermore, the mechanics of chip formation in both free cutting and constrained cutting, especially the roles played by the free surface and the constraining tool, are discussed.

Mechanics of Modulation Assisted Machining

2013 ◽  
Author(s):  
Ho Yeung ◽  
Yang Guo ◽  
Narayan K. Sundaram ◽  
James B. Mann ◽  
W. Dale Compton ◽  
...  
Keyword(s):  
Energy Dissipation ◽  
Specific Energy ◽  
Frequency Modulation ◽  
Chip Formation ◽  
Low Frequency ◽  
Contact Condition ◽  
Force Measurements

The controlled application of low-frequency modulation to machining — Modulation Assisted Machining (MAM) — effects discrete chip formation and disrupts the severe contact condition at the tool-chip interface. The role of modulation in reducing the specific energy of machining with ductile alloys is demonstrated using direct force measurements. The observed changes in energy dissipation are analyzed and explained, based on the mechanics of chip formation.

Subsurface Microstructure and Crystallographic Texture in Surface Severe Plastic Deformation Processes

2017 ◽  
Author(s):  
Zhiyu Wang ◽  
Christopher Saldana ◽  
Saurabh Basu
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Crystallographic Texture ◽  
Deformation Process ◽  
High Speed ◽  
Surface Deformation ◽  
Electron Backscatter Diffraction ◽  
High Speed Imaging ◽  
Strain And Strain Rate ◽  
Deformed State

Severe plastic burnishing was investigated as a promising surface severe plastic deformation technique for generating gradient microstructure surfaces. The deformed state of oxygen free high conductivity copper workpieces during the surface deformation process was determined with high-speed imaging, this complemented by microstructure characterization using orientation image microscopy based on electron backscatter diffraction. Varying deformation levels in terms of both magnitude and gradient on the processed surface were achieved through control of the incident tool angle. Refined microstructures, including laminate grains elongated in the velocity direction and equiaxed sub-micron grains were observed in the subsurface and were found to be controlled by the combined effects of strain and strain rate in the surface deformation process. Additionally, crystallographic texture evolutions were characterized, showing typical shear textures predominately along the <110> partial fiber. The rotation of texture from original ideal orientation positions was related directly to the deformation history produced by sliding process. Based on these observations, a controllable framework for producing the processed surface with expected mechanical and microstructural responses is suggested.

Modulation of Gear Tooth Loading Due to Traveling Wave Vibration

2003 ◽  
Author(s):  
Paul B. Talbert ◽  
Richard R. Gockel
Keyword(s):  
Strain Gage ◽  
Frequency Modulation ◽  
Dynamic Load ◽  
Traveling Wave ◽  
High Speed ◽  
Gear Tooth ◽  
Low Frequency ◽  
Wave Theory ◽  
Reduction Gear ◽  
Nodal Diameter

The first reduction gear set in a turboprop engine gearbox was changed from a spur configuration to helical in order to reduce dynamic load and tooth stress. During initial strain gage testing, a low frequency modulation (approximately 70 Hz) of the tooth engagement strain was observed. The modulation had not been present during previous strain gage tests of the gears in their original spur configuration. The expected decrease in dynamic load and tooth stress was not realized due to the low frequency modulation. Post test inspection revealed indications of end loading on both the forward and aft ends of the gear teeth. Additionally, a 22/rev standing wear pattern developed on the aft face of the bull gear rim where it contacts the high-speed pinion bearing thrust collar. Detailed analysis of the strain gage data coupled with traveling wave theory identified the source of the modulation as 19/rev response of a forward traveling three nodal diameter mode of the bull gear at approximately 2,500 Hz. An analytical simulation of the high-speed pinion tooth mesh multiplied by a signal representing a forward traveling three nodal diameter response of the bull gear exactly matched the observed modulation. Design-of-experiment engine tests using proximity probes to measure bull gear vibration identified improper contact at the bull gear thrust collar as the excitation of the three nodal diameter mode. A verification strain gage test with proper contact showed no modulation in tooth engagement.

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