Tribological Characterization of Machining at Very Small Contact Areas

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Michael R. Lovell ◽  
P. Cohen ◽  
Pradeep L. Menezes ◽  
R. Shankar
Keyword(s):  
High Speed ◽  
Friction Mechanisms ◽  
High Speed Steel ◽  
Small Scale ◽  
Machining Processes ◽  
Macroscopic Theory ◽  
Contact Areas ◽  
Tribological Characterization ◽  
Physical Phenomena

When machining miniaturized components, the contact conditions between the tool and the workpiece exhibit very small contact areas that are on the order of 10−5 mm2. Under these conditions, extremely high contact stresses are generated, and it is not clear whether macroscopic theories for the chip formation, cutting forces, and friction mechanisms are applicable. For this reason, the present investigation has focused on creating a basic understanding of the frictional behavior in very small scale machining processes so that evaluations of standard macroscale models could be performed. Specialized machining experiments were conducted on 70/30 brass materials using high-speed steel tools over a range of speeds, feeds, depths of cut, and tool rake angles. At each operating condition studied, the friction coefficient and the shear factor τk were obtained. Based on the experimental results, it was determined that the standard macroscopic theory for analyzing detailed friction mechanisms was insufficient in very small scale machining processes. An approach that utilized the shear factor, in contrast, was found to be better for decoupling the physical phenomena involved. Utilizing the shear factor as an analysis parameter, the parameters that significantly influence the friction in microscale machining processes were ascertained and discussed.

On the Modeling of Friction in Micromachining Processes

2007 ◽  
Author(s):  
M. R. Lovell ◽  
P. H. Cohen ◽  
R. Shankar
Keyword(s):  
Friction Mechanisms ◽  
Machining Process ◽  
Micro Machining ◽  
Machining Processes ◽  
Macroscopic Theory ◽  
Contact Conditions ◽  
Macro Scale ◽  
Scale Models ◽  
Basic Understanding ◽  
Physical Phenomena

When machining miniaturized components, the contact conditions between the tool and workpiece exhibit very small contact areas that are on the order of 10−5 mm2. Under these conditions, extremely high contact stresses are generated and it is not clear whether macroscopic theories for the chip formation, cutting forces, and the friction mechanisms are applicable. For this reason, the present investigation has focused on creating a basic understanding of the frictional behavior in micro machining processes so that evaluations of standard macro-scale models could be performed. Specialized machining experiments were conducted on 70/30 brass materials using steel tools over a range of speeds, feeds, depths of cut and tool rake angles. At each operating condition studied, the friction coefficient and the shear factor, τk, were obtained. Based on the experimental results, it was determined that standard macroscopic theory for analyzing detailed friction mechanisms was insufficient in micro machining processes. An approach that utilized the shear factor, in contrast, was found to be better for decoupling the physical phenomena involved. Utilizing the shear factor as an analysis parameter, the parameters that significantly influence the friction in microscale machining process were ascertained and discussed.

Thermal Spraying Applied Onto High Energy Railway Braking: Characterization of Friction Performances

1998 ◽  
Author(s):  
H. Bartys ◽  
J.D. Guerin ◽  
J.P. Bricout ◽  
J. Oudin
Keyword(s):  
High Speed ◽  
Wear Behavior ◽  
Energy Levels ◽  
Thermal Spraying ◽  
High Energy ◽  
Coated Steel ◽  
High Speed Trains ◽  
To Come ◽  
Tribological Characterization

Abstract Optimization of constitutive friction materials of braking devices for high speed trains is endlessly on delicate increase by reason of the large energy levels to dissipate, and the lightening more and more required by generations to come. Low thermal diffusivity materials such as coated steel discs in one of the research themes in this field. Proposed study is relative to tribological characterization of the wear behavior of stellite coatings, based on cobalt or nickel alloys against aluminum titanate pad. This one has ever been tested and prooved good behavior against cermet coated steel discs. Stellite coating performances are evaluated in term of friction coefficient, contact temperature and wear in comparison with this type of disc.

Tribological characterization of diamond-like carbon films on nonledeburitic high-speed steels

2000 ◽  
Vol 45 (3) ◽  
pp. 233-239 ◽  
Author(s):  
J Richter ◽  
I.M Hutchings ◽  
T.W Clyne ◽  
D.N Allsopp ◽  
X Peng
Keyword(s):  
High Speed ◽  
Carbon Films ◽  
Diamond Like Carbon ◽  
Tribological Characterization

Feasibility Study of the Effectiveness of Cryogenically Treated Ceramic Inserts for Pocket Milling Maneuvers

2009 ◽  
Author(s):  
Justin L. Milner ◽  
Jeffrey A. Beers ◽  
John T. Roth
Keyword(s):  
Wear Resistance ◽  
Tool Wear ◽  
Feasibility Study ◽  
High Speed ◽  
Cryogenic Treatment ◽  
Cutting Speed ◽  
High Speed Steel ◽  
Initial Study ◽  
Machining Processes ◽  
Cutting Speeds

Machining is a popular and versatile manufacturing process that is widely used in today’s industry when producing metallic parts; however, limited tool life can make this an expensive and time consuming fabrication technique. Consequently, methods that decrease the rate of tool wear and, thus, increase tool longevity are a vital component when improving the efficiency of machining processes. To this end, cryogenically treating cutting tools (especially high-speed steel tooling) is becoming more commonplace since research has shown that the treated tooling exhibits significantly higher wear resistance. At this point, however, the effect of cryogenic treatments on ceramic tooling has not been established. Considering this, the research herein presents a feasibility study on the effectiveness of using cryogenic treatments to enhance the wear resistance of WG-300 whisker-reinforced ceramic cutting inserts. To begin, the effect of the cryogenic treatment on the insert’s hardness is examined. Subsequently, tool wear tests are conducted at various cutting speeds. Through this study, it is shown that cryogenically treating the ceramic inserts decreases the rate of tool wear at each of the cutting speeds that were tested. However, the degree of wear resistance introduced by cryogenically treating the inserts proved to be highly dependent on the cutting speed, with slower speeds exhibiting greater improvements. Thus, based on this initial study, the cryogenic treatment of ceramic tooling appears to produce beneficial results, potentially increasing the overall efficiency of machining processes.

Microstructure, thermal, and mechanical characterization of rapidly solidified high strength Fe84.3Cr4.3Mo4.6V2.2C4.6

2010 ◽  
Vol 25 (6) ◽  
pp. 1164-1171 ◽  
Author(s):  
A. Schlieter ◽  
U. Kühn ◽  
J. Eckert ◽  
H-J. Seifert
Keyword(s):  
Mechanical Properties ◽  
High Speed ◽  
High Speed Steel ◽  
High Strength ◽  
Cast State ◽  
High Fracture ◽  
Complex Carbides ◽  
Rapidly Solidified ◽  
Heating Up

Systematic microstructural and mechanical investigations of the Fe84.3Cr4.3Mo4.6V2.2C4.6 alloy cast under special manufacturing conditions in the as-cast state and after specific heat treatment are presented to point out that the special manufacturing of the alloy led to high compression strength (up to 4680 MPa) combined with large fracture strain (about 20%) already in the as-cast state. One select chemical composition of the alloy, which was mentioned previously [Kühn et al., Appl. Phys. Lett.90, 261901 (2007)] enhanced mechanical properties already in the as-cast state. Furthermore, that composition is comparable to commercial high-speed steel. By the special manufacturing used, a high purity of elements and a high cooling rate, which led to a microstructure similar to a composite-like material, composed of dendritic area (martensite, bainite, and ferrite) and interdendritic area (e.g., complex carbides). The presented article demonstrates an alloy that exhibits already in the as-cast state high fracture strength and large ductility. Furthermore, these outstanding mechanical properties remain unchanged after heating up to 873 K.

scholarly journals Novel Mechanical Characterization of Austenite and Ferrite Phases within Duplex Stainless Steel

Metals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1352
Author(s):  
Hossein Besharatloo ◽  
Marcel Carpio ◽  
José-María Cabrera ◽  
Antonio Manuel Mateo ◽  
Gemma Fargas ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
High Speed ◽  
Mapping Technique ◽  
Small Scale ◽  
Processing Conditions ◽  
Excellent Correlation ◽  
Electron Backscattered Diffraction ◽  
Interphase Boundaries

The microstructure and micromechanical properties of the constitutive phases of a particular duplex stainless steel in various processing conditions have been characterized. Hardness (H), elastic modulus (E) and H/E cartography maps were obtained by using a high-speed nanoindentation mapping technique. Small-scale H and E evolution at different processing conditions has been investigated by statistical analysis of a large number of nanoindentations (10,000 imprints per sample). Two mechanically distinct phases, ferrite (α) and austenite (γ), were deconvoluted from this dataset using Ulm and Constantinides’ method, with the remaining values assigned to a third mechanical phase linked to composite-like (containing α/γ interphase boundaries) regions. These mechanical property phase assessments were supplemented by overlaying crystallographic phase maps obtained by electron backscattered diffraction. An excellent correlation between microstructure and small-scale mechanical properties was achieved, especially when considering the ratio H/E.

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