Incipient Plastic Strain Fields in Material Removal Processes

2014 ◽  
Author(s):  
F. Du ◽  
C. Moreno ◽  
Z. Wang ◽  
C. Saldana
Keyword(s):  
Flow Field ◽  
Chip Formation ◽  
Material Removal ◽  
Transient Flow ◽  
Surface Texturing ◽  
Shear Plane ◽  
Image Correlation ◽  
Removal Processes ◽  
Mechanical Surface

Knowledge of the plasticity associated with the incipient stage of chip formation is important for understanding the flow field underlying transient material removal processes. The transition from an incipient state of strain to steady-state was investigated in chip formation of copper. Characterization of the flow field was made by image correlation, hardness mapping and microstructure measurement. A framework for describing the incipient straining length in chip formation as a function of process parameters was established and explained by effects of the deformation on shear plane morphology. The present results are potentially useful for enabling better informed design of processing configurations wherein transient flow fields contribute significantly to the overall deformation process, such as in grain refinement methods for bulk materials and micro-mechanical surface texturing methods based on machining.

Modulation-Assisted Machining: A New Paradigm in Material Removal Processes

2011 ◽  
Vol 223 ◽  
pp. 514-522 ◽  
Author(s):  
James B. Mann ◽  
Yang Guo ◽  
Christopher Saldana ◽  
Ho Yeung ◽  
W. Dale Compton ◽  
...  
Keyword(s):  
Tool Wear ◽  
Chip Formation ◽  
Material Removal ◽  
Surface Texturing ◽  
Low Frequency ◽  
Contact Condition ◽  
New Paradigm ◽  
Machining Performance ◽  
Removal Processes ◽  
Conventional Machining

Modulation Assisted Machining (MAM), based on controlled superimposition of low-frequency modulation to conventional machining, effects discrete chip formation and disrupts the severe contact condition at the tool-chip interface. The underlying theory of discrete chip formation and its implications are briefly described and illustrated. Benefits such as improved chip management and lubrication, reduction of tool wear, enhanced material removal, particulate manufacturing and surface texturing are highlighted using case studies. MAM represents a new paradigm for machining in that it deliberately employs ‘good vibrations’ to enhance machining performance and capability.

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.

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.

scholarly journals Geomorphological characterization of the 2014–2015 Holuhraun lava flow-field in Iceland

2021 ◽  
pp. 107278
Author(s):  
Joana R.C. Voigt ◽  
Christopher W. Hamilton ◽  
Stephen P. Scheidt ◽  
Ulrich Münzer ◽  
Ármann Höskuldsson ◽  
...  
Keyword(s):  
Flow Field ◽  
Lava Flow ◽  
Lava Flow Field

MECHANICAL CHARACTERIZATION OF MATERIALS AND DIAGNOSIS OF STRUCTURES BY INVERSE ANALYSES: SOME INNOVATIVE PROCEDURES AND APPLICATIONS

2014 ◽  
Vol 11 (03) ◽  
pp. 1343002 ◽  
Author(s):  
GIULIO MAIER ◽  
VLADIMIR BULJAK ◽  
TOMASZ GARBOWSKI ◽  
GIUSEPPE COCCHETTI ◽  
GIORGIO NOVATI
Keyword(s):  
Structural Analysis ◽  
Digital Image Correlation ◽  
Residual Stresses ◽  
Mechanical Characterization ◽  
Image Correlation ◽  
Alkali Silica Reaction ◽  
Compression Tests ◽  
Material Models ◽  
Characterization Of Materials

A survey is presented herein of some recent research contributions to the methodology of inverse structural analysis based on statical tests for diagnosis of possibly damaged structures and for mechanical characterization of materials in diverse industrial environments. The following issues are briefly considered: identifications of parameters in material models and of residual stresses on the basis of indentation experiments; mechanical characterization of free-foils and laminates by cruciform and compression tests and digital image correlation measurements; diagnosis, both superficially and in depth, of concrete dams, possibly affected by alkali-silica-reaction or otherwise damaged.

A new dynamic mesh algorithm for studying the 3D transient flow field of tilting pad journal bearings

2016 ◽  
Vol 230 (12) ◽  
pp. 1470-1482 ◽  
Author(s):  
Mengxuan Li ◽  
Chaohua Gu ◽  
Xiaohong Pan ◽  
Shuiying Zheng ◽  
Qiang Li
Keyword(s):  
Flow Field ◽  
Equilibrium Position ◽  
Transient Flow ◽  
Journal Bearings ◽  
Dynamic Mesh ◽  
Static Equilibrium ◽  
Time Step ◽  
Tilting Pad ◽  
Grid Nodes ◽  
Tilting Pad Journal Bearings

A new dynamic mesh algorithm is developed in this paper to realize the three-dimensional (3D) computational fluid dynamics (CFD) method for studying the small clearance transient flow field of tilting pad journal bearings (TPJBs). It is based on a structured grid, ensuring that the total number and the topology relationship of the grid nodes remain unchanged during the dynamic mesh updating process. The displacements of the grid nodes can be precisely recalculated at every time step. The updated mesh maintains high quality and is suitable for transient calculation of large journal displacement in FLUENT. The calculation results, such as the static equilibrium position and the dynamic characteristic coefficients, are consistent with the two-dimensional (2D) solution of the Reynolds equation. Furthermore, in the process of transient analysis, under conditions in which the journal is away from the static equilibrium position, evident differences appear between linearized and transient oil film forces, indicating that the nonlinear transient calculation is more suitable for studying the rotor-bearing system.

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