A Review of Dry Particulate Lubrication: Powder and Granular Materials

2007 ◽  
Vol 129 (2) ◽  
pp. 438-449 ◽  
Author(s):  
Emmanuel Y. A. Wornyoh ◽  
Venkata K. Jasti ◽  
C. Fred Higgs
Keyword(s):  
Surface Velocity ◽  
High Shear ◽  
Shear Rates ◽  
The Past ◽  
Hard Particles ◽  
High Shear Rates ◽  
Bulk Medium ◽  
Soft Particles ◽  
Transfer Momentum ◽  
Low Shear

Research efforts related to dry particulates in sliding contacts are reviewed. In the tribology community, there are primarily two types of dry particulate lubricants that are studied—granular and powder. Granular lubricants usually refer to dry, cohesionless, hard particles that transfer momentum and accommodate surface velocity differences through shearing and rolling at low shear rates, and collisions at high shear rates. Powder lubricants refer to dry, cohesive, soft particles that accommodate surface velocity differences mostly by adhering to surfaces and shearing in the bulk medium, in a manner similar to hydrodynamic fluids. Spanning the past five decades, this review proposes a classification system for the scientific works in the dry particulate tribology literature in terms of theory, experiments, and numerical simulations. It also suggests that these works can be further categorized based on their tribosystem geometry—annular, parallel, and converging.

The Simulation of Aggregated Colloids Under Flow

1992 ◽  
Vol 289 ◽  
Author(s):  
John R. Melrose
Keyword(s):  
Shear Rate ◽  
Large Scale ◽  
Shear Thinning ◽  
High Shear ◽  
Shear Rates ◽  
Rouse Model ◽  
High Shear Rates ◽  
Structural Breakdown ◽  
Large Scale Simulations ◽  
Low Shear

AbstractAn overview is given of theories of aggregates under flow. These generally assume some sort of structural breakdown as the shear rate is increased. Models vary with both the rigidity of the bonding and the level of treatment of hydrodynamics. Results are presented for simulations of a Rouse model of non-rigid, (i.e. central force) weakly bonded aggregates. In large scale simulations different structures are observed at low and high shear rates. The change from one structure to another is associated with a change in the rate of shear thinning. The model captures low shear rate features of real systems absent in previous models: this feature is ascribed to agglomerate deformations. Quantitatively, the model is two orders of magnitude out from experiment but some scaling is possible.

Pediatric Blood Viscoelasticity Measurements

2007 ◽  
Author(s):  
Neema Nair ◽  
George M. Pantalos ◽  
M. Keith Sharp
Keyword(s):  
Oscillatory Flow ◽  
Capillary Tube ◽  
Cell Aggregation ◽  
High Shear ◽  
Red Cell ◽  
Cardiovascular Devices ◽  
Shear Rates ◽  
High Shear Rates ◽  
Low Shear ◽  
Red Cell Aggregation

Motivated by questions related to flow in pediatric cardiovascular devices, the purpose of this study was to compare pediatric and adult complex viscoelasticity η* = ηV − iηE, where ηV and ηE are viscous and elastic components, respectively, measured in oscillatory flow in a capillary tube [Thurston 1972]. For normal blood, viscosity is increased at low shear rates by red cell aggregation and reduced at high shear rates due to disaggregation, orientation and deformation of red cells. The elastic part is also normally psuedoplastic, indicative of the deformation of red cell aggregates at high shear and individual cells at low shear, respectively.

Platelet Associated Fibrinogen and ICAM-2 Induce Firm Adhesion of Neutrophils under Flow Conditions

1998 ◽  
Vol 80 (09) ◽  
pp. 443-448 ◽  
Author(s):  
P. H. M. Kuijper ◽  
H. I. Gallardo Torres ◽  
J.-W. J. Lammers ◽  
J. J. Sixma ◽  
L. Koenderman ◽  
...  
Keyword(s):  
Vessel Wall ◽  
High Shear ◽  
Flow Conditions ◽  
Shear Rates ◽  
Β2 Integrin ◽  
High Shear Rates ◽  
Wall Injury ◽  
Blocking Antibodies ◽  
Low Shear

SummarySurface-bound platelets support selectin-mediated rolling and β2-integrin-mediated firm adhesion of neutrophils (PMN) under flow conditions. We examined which ligands on platelets mediate this firm adhesion. Surface-bound platelets express ICAM-2 and GPIIbIIIa-bound fibrinogen, which are ligands for LFA-1 and MAC-1. In a well defined model for vessel wall injury, blood from an afibrinogenemic patient was perfused over ECM-coated coverslips to obtain fibrinogen-free platelet surfaces. At high shear rates, PMN-adhesion to fibrinogen-free platelet surfaces decreased compared to fibrinogen-containing controls. Under these conditions, firm adhesion and not rolling was blocked demonstrating the importance of fibrinogen in this process. In addition, MAC-1 and LFA-1 on PMN and ICAM-2 on platelets played a role in firm adhesion; the effect of blocking antibodies was most evident at high shear. The effects of fibrinogen depletion and ICAM-2 blocking were additive. In conclusion, multiple redundant ligands, like ICAM-2 and fibrinogen, induce firm and shear resistant PMN adhesion to platelets under flow conditions. Individually these ligands become critical at higher shear. Blocking of two or more interactions also interferes with low shear adhesion.

Morphological Evolution of SCN Crystals in a Shear Flow

2014 ◽  
Vol 217-218 ◽  
pp. 83-90
Author(s):  
Mehdi Reisi ◽  
Behzad Niroumand ◽  
Ebrahim Shirani
Keyword(s):  
Shear Flow ◽  
Morphological Evolution ◽  
Solid Particles ◽  
High Shear ◽  
Shear Rates ◽  
High Shear Rates ◽  
Cluster Morphology ◽  
Size And Morphology ◽  
Low Shear

Morphological evolution of a transparent model succinonitrile (SCN) material during solidification was investigated in an apparatus resembling a shearing-disc viscometer. The in situ microscopic observations showed that fragmentation decreased the average particles size, but did not result in transition of dendritic to spherical morphology. At low shear rates, the degenerated dendrites and at high shear rates, the pseudo-cluster morphology was observed. It was revealed that coarsening has the most important effect on the final morphology of solid particles. The quantitative influences of shearing rate and intensity on the size and morphology of solid crystals were also discussed based on the measurements on the microstructures.

Pre-Treatment Steady-State Rheology Predicts Response to Hydroxyurea in Patients with Sickle Cell Disease

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 3661-3661
Author(s):  
Alessandro Baldan ◽  
Carly Ginter Summerall ◽  
Loretta James ◽  
Bogdan R. Dinu ◽  
Jonathan M. Flanagan ◽  
...  
Keyword(s):  
Steady State ◽  
Blood Rheology ◽  
High Shear ◽  
Cell Disease ◽  
Shear Rates ◽  
High Shear Rates ◽  
Baseline Values ◽  
The Mean ◽  
Pre Treatment ◽  
Low Shear

Abstract Background: Patients with sickle cell disease (SCD) have altered blood rheology due to erythrocyte abnormalities, such as increased aggregation and RBC density. The hematocrit to viscosity ratio (HVR) is a measure of RBC oxygen carrying capacity, and is reduced in SCD. Higher percent dense red blood cells (%DRBC) and lower HVR have been associated with higher rates of disease related complications. The aim of this study was to elucidate the effects of hydroxyurea (HU), fetal hemoglobin (HbF) and transfusion therapy (TF) on the rheology of patients with SCD. Methods: We measured whole blood viscosity of samples from children with SCD at low shear (45 s-1) and high shear (225 s-1) using a Brookfield cone and plate viscometer under oxygenated conditions. Venous blood samples in EDTA were analyzed within 4 hours of phlebotomy. Laboratory values were obtained with a Siemens ADVIA120 Hematology System; Hb profiles by high performance liquid chromatography. Samples were collected at routine clinic visits from SCD patients prior to initiation of therapy (n=105 for HbSS, n=77 for HbSC), then on HU at MTD, (n=30 for HbSS, n=13 for HbSC), or at least one week after TF (n=32). A paired T-test was used to assess treatment changes; correlation/trend tests were used to test association of hematological and rheology parameters. Results: Blood viscosities at low and high shear rates were significantly higher in untreated patients with HbSC compared to untreated patients with HbSS (p<0.001), while HVR was similar between patients with HbSC or HbSS. High endogenous HbF levels were significantly associated with higher HVR 225 s-1 in patients with HbSS but not HbSC. Patients with HbSS after TF had a significant improvement (rise) in their HVR at high shear (p=0.04) but not at low shear. This TF mediated rise in HVR 225 s-1 correlated with increased Hb (r=0.56, p<0.002), and decreased WBC and ANC (r= - 0.46 and r=- 0.36 respectively, p<0.05). Patients with greatest decreases in %HbS had most improvement in their HVR 225 s-1 (r = -0.36, p=0.15). HbSS patients treated with HU also had a rise in their HVR 225 s-1 (p=0.01) but not HVR 45 s-1. This improved HVR 225 s-1 was associated with typical HU induced changes in Hb, Hct, HbF and decreases in WBC and ANC. For HbSS patients treated with either HU or TF, a baseline HVR (at either shear rate) below the group mean experienced a greater rise in HVR, while a baseline HVR above the mean experienced a decline (p<0.001; Figure 1). HbSS patients with a pre-treatment %DRBC above the mean experienced a decline in %DRBC on HU at MTD, while those with a %DRBC below the mean did not (p=0.001).A similar trend was seen in HbSC patients treated with HU to MTD, but did not reach statistical significance. Patients with HbSC had significantly higher %DRBC compared to patients with HbSS (p<0.001). HbSC patients placed on HU had significantly higher baseline %DRBC than HbSC patients not treated with HU (15.8 ±13 versus 8.2± 6.5, p=0.001). However, HbSC patients treated to HU MTD did not experience a significant reduction in %DRBC. Individuals with HbSS and high endogenous HbF had significantly lower %DRBC (r= -0.36, p=0.002), and greater production of HbF on HU also resulted in lower %DRBC (p=0.036) in HbSS (n=25), but not HbSC patients (n=13). Conclusions: In HbSS patients, high endogenous HbF levels were significantly associated with higher HVR at high shear and with lower %DRBC, but not in HbSC patients. In HbSS patients, HU and TF therapy improved HVR at high shear rates but not low shear, possibly indicating persistent red cell adhesion at low shear rates. This improvement correlated with HbF levels in HU treated patients, and HbS levels in TF treated patients. Patients with SCD and greater than average impairment of whole blood rheology at pre-treatment steady-state experienced greater rheological improvement, demonstrated clinically by a reduction in %DRBC or a rise in HVR on HU. A cohort of 13 HbSC patients treated prospectively with HU did not demonstrate statistically significant rheological improvement, either a result of small sample size or the minimal rise in HbF despite HU therapy. Figure 1. Effect of baseline rheology on rheological changes at MTD of HU. Horizontal dotted line denotes mean baseline values. A. Patients with HbSS and a baseline HVR 45 s-1 below the mean showed an increase in HVR 45 s-1 at MTD (green dots). B. Patients with HbSS and a baseline HVR 225 s-1 below the mean showed an increase in HVR 225 s-1 at MTD (green dots). Figure 1. Effect of baseline rheology on rheological changes at MTD of HU. Horizontal dotted line denotes mean baseline values. A. Patients with HbSS and a baseline HVR 45 s-1 below the mean showed an increase in HVR 45 s-1 at MTD (green dots). B. Patients with HbSS and a baseline HVR 225 s-1 below the mean showed an increase in HVR 225 s-1 at MTD (green dots). Disclosures No relevant conflicts of interest to declare.

Effects of oxygenation and the stress hormones adrenaline and cortisol on the viscosity of blood from the trout Oncorhynchus mykiss

1995 ◽  
Vol 198 (4) ◽  
pp. 953-959
Author(s):  
B Sørensen ◽  
R E Weber
Keyword(s):  
Oncorhynchus Mykiss ◽  
Stress Hormones ◽  
Blood Rheology ◽  
Hypoxic Exposure ◽  
High Shear ◽  
Shear Rates ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
High Shear Rates ◽  
Fish Blood ◽  
Low Shear

Although the concentrations of the stress hormones adrenaline and cortisol in rainbow trout (Oncorhynchus mykiss) blood increase upon hypoxic exposure, the combined effects of these hormones and O2 lack upon fish blood rheology have not been investigated. Deoxygenated blood taken by caudal puncture exhibited lower viscosities than oxygenated samples at low shear rates, whereas the opposite was true at high shear rates. However, blood from cannulated trout had similar viscosities in its deoxygenated and oxygenated states. In the deoxygenated state, addition of adrenaline lowered viscosity at low shear rates and increased it at high shear rates, resembling the effects of deoxygenation observed in blood taken by venepuncture. In oxygenated blood on the contrary, no marked adrenaline effects were observed. In deoxygenated blood, addition of cortisol lowered viscosity at all measured shear rates compared with blood without cortisol. In oxygenated blood, however, no cortisol effects were observed. The viscosity effects observed in the presence of cortisol could not be attributed to concomitant changes in haematological variables, However, the effects in the presence of adrenaline manifested in deoxygenated 'cannula' blood and in uncannulated blood without added hormones appear to result from parallel increases in haematocrit and cell volume.

Relative Involvement of GPIb/IX-vWF Axis and GPIIb/IIIa in Thrombus Growth at High Shear Rates in the Guinea Pig

1997 ◽  
Vol 17 (5) ◽  
pp. 919-924 ◽  
Author(s):  
Patrick André ◽  
Patricia Hainaud ◽  
Claire Bal dit Sollier ◽  
Leonard I. Garfinkel ◽  
Jacques P. Caen ◽  
...  
Keyword(s):  
Guinea Pig ◽  
High Shear ◽  
Shear Rates ◽  
High Shear Rates

scholarly journals Microfluidic rheology: A new approach to measure viscosity of ceramic suspensions at extremely high shear rates

Open Ceramics ◽  
2021 ◽  
Vol 5 ◽  
pp. 100052
Author(s):  
V. Carnicer ◽  
C. Alcázar ◽  
M.J. Orts ◽  
E. Sánchez ◽  
R. Moreno
Keyword(s):  
High Shear ◽  
New Approach ◽  
Shear Rates ◽  
High Shear Rates ◽  
Ceramic Suspensions

Flow curves of mixtures of acrylonitrile–styrene copolymers with different molecular weights at extremely high shear rates (abstract)

1991 ◽  
Vol 35 (4) ◽  
pp. 706-706
Author(s):  
Hideroh Takahashi ◽  
Yoshinori Inoue ◽  
Satoru Yamamoto ◽  
Osami Kamigaito
Keyword(s):  
High Shear ◽  
Flow Curves ◽  
Shear Rates ◽  
Molecular Weights ◽  
Styrene Copolymers ◽  
High Shear Rates

Comparison of antithrombotic efficacy between edoxaban, a direct factor Xa inhibitor, and fondaparinux, an indirect factor Xa inhibitor under low and high shear rates

2011 ◽  
Vol 106 (12) ◽  
pp. 1062-1068 ◽  
Author(s):  
Naoki Tsuji ◽  
Yuko Honda ◽  
Chikako Kamisato ◽  
Yoshiyuki Morishima ◽  
Toshiro Shibano ◽  
...  
Keyword(s):  
Shear Rate ◽  
Arterial Thrombosis ◽  
Factor Xa ◽  
High Shear ◽  
Shear Rates ◽  
Thrombosis Model ◽  
Perfusion Chamber ◽  
High Shear Rates ◽  
Antithrombotic Effects ◽  
Antithrombotic Efficacy

SummaryEdoxaban is an oral, direct factor Xa (FXa) inhibitor under late-phase clinical development. This study compared the antithrombotic efficacy of edoxaban with that of an indirect FXa inhibitor, fondaparinux, in in vivo venous and arterial thrombosis models and in ex vivo perfusion chamber thrombosis model under low and high shear rates in rats. Venous and arterial thrombi were induced by platinum wire insertion into the inferior vena cava and by application of FeCl3 to the carotid artery, respectively. The perfusion chamber thrombus was formed by blood perfusion into a collagen-coated capillary at 150 s-1 (low shear rate) and 1,600 s-1 (high shear rate). Effective doses of edoxaban that reduced thrombus formation by 50% (ED50) in venous and arterial thrombosis models were 0.076 and 0.093 mg/kg/h, respectively. In contrast, ED50 of fondaparinux in the arterial thrombosis model (>10 mg/kg/h) was markedly higher compared to ED50 in the venous thrombosis model (0.021 mg/kg/h). In the perfusion chamber thrombosis model, the ratio of ED50 under high shear rate (1.13 mg/kg/h) to that under low shear rate (0.63 mg/kg/h) for edoxaban was 1.9, whereas that for fondaparinux was more than 66. While the efficacy of fondaparinux markedly decreased in arterial thrombosis and in a high-shear state, edoxaban exerted consistent antithrombotic effects regardless of flow conditions. These results suggest that shear rate is a key factor in different antithrombotic effects between edoxaban and fondaparinux.

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