The Role of Cutter Eccentricity on Surface Finish and Milling Forces

2004 ◽  
Author(s):  
Tony L. Schmitz ◽  
Jeremiah Couey ◽  
Eric Marsh ◽  
Michael F. Tummond
Keyword(s):  
Surface Finish ◽  
Milling Machine ◽  
Time Domain Simulation ◽  
Machined Surface ◽  
Premature Failure ◽  
Series Of Experiments ◽  
Error Motion ◽  
Milling Forces ◽  
Chip Load

In this paper, the role of milling cutter eccentricity, commonly referred to as runout, is explored to determine its effects on surface topography and milling forces. This work is motivated by the observation that commercially-available cutter bodies often exhibit variation in the teeth/insert radial locations as a result of manufacturing issues. Consequently, the chip load on individual cutting teeth varies periodically, which can lead to premature failure of the cutting edges. Additionally, this chip load variation increases the roughness of machined surfaces. This research isolates the effect of runout on cutting forces and the machined surface finish in a series of experiments completed on a precision milling machine with 0.1 μm positioning repeatability and 0.02 μm spindle error motion. The runout is varied in a controlled fashion and results compared between experiment and a comprehensive time-domain simulation.

Built-Up-Edge Formation in Micromilling

2015 ◽  
Author(s):  
V. Kovvuri ◽  
Z. Wang ◽  
A. Araujo ◽  
M. B. da Silva ◽  
S. Bukkapatnam ◽  
...  
Keyword(s):  
Surface Finish ◽  
Cutting Speed ◽  
Minimum Quantity Lubrication ◽  
Cutting Parameters ◽  
Tool Geometry ◽  
Machined Surface ◽  
Area Density ◽  
Milled Surface ◽  
Chip Load ◽  
Cutting Speeds

This paper presents experimental study on conditions for built-up-edge (BUE) formation and its effects in micromilling. Surface finish and BUE area density on a micromilled surface are used to quantify the presence of BUE. A model for surface finish is derived based on the topography of milled surface and tool geometry. Assuming no BUE formation, this empirical model shows the dependence of surface finish on chip load, tool concavity angle, and includes the effect of cutting parameters and milling modes (up-milling or down-milling). Micromilling tools of 100–400 μm diameters are used for milling stainless steel at 10–60 m/min cutting speed, 0.05–1 μm/flute chip load, in minimum quality lubrication condition (MQL). A BUE, embedded onto either a milled surface or tool cutting edge or chip, is identified by scanning electron microscopy and energy dispersive spectroscopy techniques; the severity of BUE formation is quantified as area density when observing a machined surface at high magnification with optical microscopy or interferometry. Condition for BUE formation is presented by mapping the surface finish and BUE area density against cutting speed and chip load. A microtool would fracture catastrophically at high cutting speeds and/or high chip loads due to excessive dynamic stresses on a microtool; such tool would also fail at the other extreme when low cutting speeds and chip loads promote formation and detachment of BUE on the tool surface, therefore, chipping the fragile microcutting edges of a microtool. There is an optimal zone for effective micromilling without tool failure and BUEs. The measured surface finish approaches the theoretical value when BUE is absent, i.e. micromilling in minimum quantity lubrication at cutting speed between 40–60 m/min and chip load higher than 0.15μm/tooth. The BUE area density for up-milling is lower than that for down-milling at low cutting speed; such difference gradually diminishes when selecting milling parameters in the optimal zone where BUE is practically absent.

ALCOA 2024

Alloy Digest ◽  
1998 ◽  
Vol 47 (3) ◽  
Keyword(s):  
Corrosion Resistance ◽  
Physical Properties ◽  
Surface Treatment ◽  
Tensile Properties ◽  
Surface Finish ◽  
High Strength ◽  
Machined Surface ◽  
2024 Alloy ◽  
Structural Applications ◽  
Strength Material

Abstract Alcoa 2024 alloy has good machinability and machined surface finish capability, and is a high-strength material of adequate workability. It has largely superseded alloy 2017 (see Alloy Digest Al-58, August 1974) for structural applications. The alloy has comparable strength to some mild steels. This datasheet provides information on composition, physical properties, and tensile properties. It also includes information on corrosion resistance as well as machining and surface treatment. Filing Code: AL-346. Producer or source: ALCOA Wire, Rod & Bar Division.

Nitric oxide decreases lung liquid production via guanosine 3′,5′-cyclic monophosphate

2001 ◽  
Vol 280 (5) ◽  
pp. L923-L929 ◽  
Author(s):  
James J. Cummings ◽  
Huamei Wang
Keyword(s):  
Nitric Oxide ◽  
Pulmonary Epithelium ◽  
Fetal Sheep ◽  
Cgmp Analog ◽  
Pulmonary Arterial ◽  
Series Of Experiments ◽  
Lung Liquid ◽  
Tracer Dilution ◽  
Induced Changes

We studied the role of cGMP in nitric oxide (NO)-induced changes in lung liquid production ( J v ) in chronically instrumented fetal sheep. Forty-five studies were done in which J v was measured by a tracer dilution technique. Left pulmonary arterial flow (Qlpa) was measured by a Doppler flow probe. There were two series of experiments. In the first, we gave 8-bromo-cGMP, a cGMP analog, by either the pulmonary vascular or intraluminal route; in the second, we used agents to inhibit or enhance endogenous cGMP activity. When infused directly into the pulmonary circulation, 8-bromo-cGMP significantly increased Qlpa but had no effect on J v. Conversely, when instilled into the lung liquid, 8-bromo-cGMP had no effect on Qlpa but significantly reduced J v. Inhibition of guanylate cyclase activity with methylene blue totally blocked, whereas phosphodiesterase inhibition with Zaprinast significantly enhanced, the effect of instilled NO on J v. Thus the reduction in lung liquid caused by NO appears to be mediated by cGMP, perhaps through a direct effect on the pulmonary epithelium.

Ti-6Al-4V Surfaces in SiC Powder Mixed Electrical Discharge Machining

2013 ◽  
Vol 856 ◽  
pp. 226-230 ◽  
Author(s):  
Hamidullah Yaşar ◽  
Bülent Ekmekci
Keyword(s):  
Electrical Discharge ◽  
Electrical Discharge Machining ◽  
Dielectric Liquid ◽  
Operational Parameters ◽  
Electrical Parameters ◽  
Machined Surface ◽  
Optical Scanning ◽  
Surface Topographies ◽  
Powder Suspension

The role of suspended particles on Ti-6Al-4V surface in Powder Mixed Electrical Discharge Machining (PMEDM) is studied using SiC powder mixing in water dielectric liquid. Surface modifications due to the additives in dielectric liquid are investigated by means of optical, scanning electron microscopy and energy dispersive spectroscopy. The attachment of added powders and surface topographies interrelated with powder suspension concentration, particle size and electrical parameters such as pulse on duration and current. The influence on discharge transitivity with respect to SiC additives is noticed with pock like features on the surface. The geometry and size of these features indicated a robust dependency with respect to operational parameters and indicated the role of secondary discharges during PMEDM. SiC particles severely transferred from di-electric liquid to machined surface at critical operational parameters and implied that the process could be also used as a surface alloying technique.

Beaumont's Contribution to Gastric Psychophysiology: A Reappraisal

1988 ◽  
Vol 33 (7) ◽  
pp. 650-653 ◽  
Author(s):  
François M. Mai
Keyword(s):  
Gastric Emptying ◽  
Delayed Gastric Emptying ◽  
Bile Reflux ◽  
Emotional Arousal ◽  
Gastric Fistula ◽  
Physiological Changes ◽  
Digestive Process ◽  
Psychophysiological Research ◽  
Series Of Experiments

William Beaumont's monograph on the physiology of digestion which was first published in 1833, has become a classic in its field. In a series of experiments over a 10 year period on Alexis St. Martin, a 19 year old Canadian voyageur with a traumatic gastric fistula, Beaumont was the first to describe many important aspects of the digestive process. In two of the 238 experiments Beaumont noted gastric physiological changes induced by emotional arousal, these being bile reflux and delayed gastric emptying. Elsewhere in the book, but not in experimental context, Beaumont referred to non-specific changes in coloration and secretion of the mucous membrane induced by emotion. Modern gastric psychophysiological research has shown that emotional arousal increases, and withdrawal decreases, gastric acid secretion. It has also been shown conclusively that emotion can cause a reflux of bile into the stomach and it may delay gastric emptying. Although the main thrust of Beaumont's work was physiological, he must be credited with being the first investigator to draw attention to the role of emotional arousal in the digestive process.

κ- but not δ-opioid receptors mediate effects of ischemic preconditioning on both infarct and arrhythmia in rats

2001 ◽  
Vol 280 (1) ◽  
pp. H384-H391 ◽  
Author(s):  
Guan-Ying Wang ◽  
Song Wu ◽  
Jian-Ming Pei ◽  
Xiao-Chun Yu ◽  
Tak-Ming Wong
Keyword(s):  
Infarct Size ◽  
Opioid Receptors ◽  
Ischemic Preconditioning ◽  
Antiarrhythmic Action ◽  
Perfused Rat Heart ◽  
Calphostin C ◽  
Kinase C ◽  
Series Of Experiments ◽  
Pkc Inhibitors

Two series of experiments were performed in the isolated perfused rat heart to determine the role of κ- and δ-opioid receptors (OR) in cardioprotection of ischemic preconditioning (IP). In the first series of experiments, it was found that IP with two cycles of 5-min regional ischemia followed by 5-min reperfusion each reduced infarct size induced by 30-min ischemia, and the ameliorating effect of IP on infarct was attenuated with blockade of either 5 × 10−6 mol/l nor-binaltorphimine (nor-BNI), a selective κ-OR antagonist, or 5 × 10−6 mol/l naltrindole (NTD), a selective δ-OR antagonist. The second series showed that U50,488H, a selective κ-OR agonist, ord-Ala2-d-leu5-enkephalin (DADLE), a selective δ-OR agonist, dose dependently reduced the infarct size induced by ischemia, which mimicked the effects of IP. The effect of 10−5 mol/l U50,488H on infarct was significantly attenuated by blockade of protein kinase C (PKC) with specific PKC inhibitors, 5 × 10−6 mol/l chelerythrine or 8 × 10−7 mol/l calphostin C, as well as by blockade of ATP-sensitive K+ (KATP) channels with blockers of the channel, 10−5 mol/l glibenclamide or 10−4 mol/l 5-hydroxydecanoate. IP also reduced arrhythmia induced by ischemia. Nor-BNI, but not NTD, attenuated, while U50,488H, but not DADLE, mimicked the antiarrhythmic action of IP. In conclusion, the present study has provided first evidence that κ-OR mediates the ameliorating effects of IP on infarct and arrhythmia induced by ischemia, whereas δ-OR mediates the effects only on infarct. Both PKC and KATP channels mediate the effect of activation of κ-OR on infarct.

Role of adenosine in postprandial and reactive hyperemia in canine jejunum

1992 ◽  
Vol 263 (4) ◽  
pp. G487-G493 ◽  
Author(s):  
D. R. Sawmiller ◽  
C. C. Chou
Keyword(s):  
Blood Flow ◽  
Oxygen Consumption ◽  
Adenosine Deaminase ◽  
Reactive Hyperemia ◽  
Concentration Difference ◽  
Adenosine Concentration ◽  
Anesthetized Dogs ◽  
Series Of Experiments ◽  
Increased Blood Flow

The role of adenosine in postprandial jejunal hyperemia was investigated by determining the effect of placement of predigested food into the jejunal lumen on blood flow and oxygen consumption before and during intra-arterial infusion of dipyridamole (1.5 microM arterial concn) or adenosine deaminase (9 U/ml arterial concn) in anesthetized dogs. Neither drug significantly altered resting jejunal blood flow and oxygen consumption. Before dipyridamole or deaminase, food placement increased blood flow by 30-36%, 26-42%, and 21-46%, and oxygen consumption by 13-22%, 21-22%, and 26-29%, during 0- to 3-, 4- to 7-, and 8- to 11-min placement periods, respectively. Adenosine deaminase abolished the entire 11-min hyperemia, whereas dipyridamole significantly enhanced the initial 7-min hyperemia (45-49%). Both drugs abolished the initial 7-min food-induced increase in oxygen consumption. Dipyridamole attenuated (14%), whereas deaminase did not alter (28%), the increased oxygen consumption that occurred at 8-11 min. Adenosine deaminase also prevented the food-induced increase in venoarterial adenosine concentration difference. In separate series of experiments, luminal placement of food significantly increased jejunal lymphatic adenosine concentration and release. Also, reactive hyperemia was accompanied by an increase in venous adenosine concentration and release. This study provides further evidence to support the thesis that adenosine plays a role in postprandial and reactive hyperemia in the canine jejunum.

scholarly journals An Investigation To Achieve a Good Surface Integrity in WEDM of Ti-6242 Super Alloy

2021 ◽  
Author(s):  
Sonia Ezeddini ◽  
Wajdi Rajhi ◽  
Mohamed Boujelbene ◽  
Emin Bayraktar ◽  
Sahbi Ben Salem
Keyword(s):  
Surface Roughness ◽  
Pulse Duration ◽  
Surface Integrity ◽  
Surface Finish ◽  
Feed Rate ◽  
Cutting Parameters ◽  
Machined Surface ◽  
Good Surface ◽  
Pulse On Time ◽  
Super Alloy

Abstract Ti-6242 is a super alloy which exhibits the best creep resistance among available titanium alloys and is widely used in the manufacture by WEDM of aircraft engine turbomachinery components. However, the final quality of wire EDMed surface is a great challenge as it is affected by various factors that need optimization for surface integrity and machine efficiency improvement. The aim of this study is to investigate the effect of a set of cutting process parameters such as pulse on time (Ton), servo voltage (U), feed rate (S) and flushing pressure (p) on surface roughness (SR) when machining Ti-6242 super alloy by WEDM process using a brass tool electrode and deionized water as a dielectric fluid. WEDM experiments were conducted, and SR (Ra) measurement was carried out using a 3D optical surface roughness-meter (3D–SurfaScan). As a tool to optimize cutting parameters for SR improvement, Taguchi's signal‐to‐noise ratio (S/N) approach was applied using L9 (3^4) orthogonal array and Lower-The-Better (LTB) criteria. Substantially, the findings from current investigation suggest the application of the values 0.9 µs, 100V, 29 mm/min, and 60 bar for Ton, U, S and p cutting parameters, respectively, for producing a good surface finish quality. Percent contributions of the machining parameters on SR (Ra) assessed based on ANOVA analysis are 62.94%, 20.84%, 11.46% and 4.74% for U, S, Ton and p, respectively. Subsequently, accurate predictive model for SR (Ra) is established based on response surface analysis (RSA). The contour plots for SR (Ra) indicate that when flushing pressure p converges to a critical value (80 bar), a poor-quality surface finish is highly expected with the excessive increase in U and S. Electron microscope scanning (SEM) observations have been performed on machined surface for a wide range of cutting parameters to characterize wire EDMed surface of Ti-6242. SEM micrographs indicate that the machined surface acquires a foamy structure and shows white layer and machining-induced damage that the characteristics are highly dependent on cutting parameters. At high servo-voltage, the decrease in pulse on time Ton and feed rate S results in a large decrease in overall machining-induced surface damage. Moreover, for high servo-voltage and feed rate levels, it has been observed that pulse on time could play a role of controlling the surface microcracks density. In fact, the use of a low pulse duration of cut combined with high servo-voltage and feed rate has been shown to inhibit surface microcracks formation giving the material surface a better resistance to cracking than at high pulse duration.

scholarly journals Roles of gene transcription and PKA subtype activation in maturation of murine oocytes

Reproduction ◽  
2002 ◽  
pp. 799-806 ◽  
Author(s):  
KF Rodriguez ◽  
RM Petters ◽  
AE Crosier ◽  
CE Farin
Keyword(s):  
Gene Transcription ◽  
Cumulus Cell ◽  
Cumulus Cells ◽  
Type I ◽  
Type Ii ◽  
Germinal Vesicle Breakdown ◽  
Series Of Experiments ◽  
And Control ◽  
Alpha Amanitin

The aims of this study were to examine the role of transcription and the coincident involvement of type I and type II protein kinase A (PKA) in the resumption of meiosis in murine cumulus-oocyte complexes (COCs) using the transcriptional inhibitors 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB) and alpha-amanitin. The first series of experiments was designed to: (i) characterize the role of transcription in gonadotrophin-mediated and spontaneous maturation of murine oocytes; (ii) examine the roles of specific gonadotrophins (FSH versus hCG) and cumulus cells in transcriptionally mediated oocyte maturation; and (iii) determine the reversibility of the transcriptional arrest of meiosis. In the presence of FSH, transcriptional inhibitors arrested germinal vesicle breakdown (GVBD) (DRB: 2 +/- 2% and control: 76 +/- 2%; alpha-amanitin: 4 +/- 4% and control: 70 +/- 4%). Furthermore, cumulus cells were required for transcriptional inhibitors to arrest GVBD (DRB with cumulus cells: 0 +/- 15%; DRB without cumulus cells: 94 +/- 13%; alpha-amanitin with cumulus cells: 15 +/- 2%; alpha-amanitin without cumulus cells: 99 +/- 2%). Thus, in mice, FSH-mediated GVBD uses a transcriptional mechanism, which probably occurs within the cumulus cell compartment. In a second series of experiments, the role of transcription in mediating the resumption of meiosis after activation of either type I or type II PKA was examined. Activation of type I PKA in murine COCs resulted in an arrest of GVBD that was independent of a transcriptional event (with DRB: 7 +/- 9% GVBD; without DRB: 11 +/- 9% GVBD). In contrast, activation of type II PKA resulted in a resumption of meiosis, which required the occurrence of gene transcription (with DRB: 12 +/- 9% GVBD; without DRB: 80 +/- 9% GVBD). As FSH binding to cumulus cells activates the PKA second messenger system, our results indicate that, in cultured murine COCs, FSH binding to cumulus cells results in the activation of type II PKA, which, in turn, mediates a downstream transcriptional event required for the initiation of GVBD.

The role of ultimobranchial bodies in the modulation of the response of chick embryos to 1,25-dihydroxycholecalciferol

Development ◽  
1986 ◽  
Vol 97 (1) ◽  
pp. 87-94
Author(s):  
Roberto Narbaitz ◽  
Jaffar Soleimani Rad
Keyword(s):  
Bone Resorption ◽  
Ethyl Alcohol ◽  
Inorganic Phosphate ◽  
Histological Study ◽  
Chorioallantoic Membrane ◽  
Chick Embryos ◽  
Series Of Experiments ◽  
Ultrastructural Characteristics ◽  
Bone Trabeculae

Ultimobranchial bodies (UBBs) were dissected from 17-day-old chick embryos and grafted onto the chorioallantoic membrane of 8-day-old embryos. The embryos with UBB grafts as well as sham-grafted controls were injected on the 10th day of incubation with 100 ng 1,25(OH)2D3 dissolved in ethyl alcohol or with an equal volume of ethyl alcohol alone; embryos were sacrificed on the 13th day. Grafted UBBs showed ultrastructural characteristics typical of actively secreting glands. A histological study of the tibiae from all embryos showed that while the grafted embryos responded to the injection of 1,25(OH)2D3 with a peripheral rim of undermineralized bone trabeculae, sham-grafted embryos never did so. These results confirm the original hypothesis that the presence of differentiated UBBs is a precondition for the production of undermineralized bone (osteoid) by 1,25(OH)2D3. In a second series of experiments, similarly treated embryos were sacrificed on the 10th, 11th, 12th and 13th day; the levels of calcium and inorganic phosphate were determined in their blood. The injection of 1,25(OH)2D3 produced in all embryos hypercalcaemia and hypophosphataemia. However, the hypophosphataemic response was more prolonged in the embryos with UBB grafts than in sham-grafted ones. These results suggest that the grafted UBBs prolonged the hypophosphataemic response, probably by secreting calcitonin and thus reducing the rate of bone resorption. It is also probable that the prolonged hypophosphataemia produced or contributed to the undermineralization of the peripheral (subperiosteal) trabeculae.

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