scholarly journals Development of methods for evaluation of lubrication properties of hydraulic aviation oils

2021 ◽  
Vol 101 (3) ◽  
pp. 42-47
Author(s):  
T. Ilina
Keyword(s):  
Wear Resistance ◽  
Rheological Properties ◽  
Effective Viscosity ◽  
Shear Stresses ◽  
Visual Evaluation ◽  
Start Up ◽  
Lubricating Layer ◽  
Antiwear Properties ◽  
Boundary Films ◽  
Increasing Temperature

A method for evaluation of the lubricating and rheological properties of hydraulic oils in tribological contacts has been developed, which consists in online studying samples of commercial batches of oils on a software and hardware complex with visual evaluation of the kinetics of changes in the main tribological indicators of friction contact. Using a roller analogy, the operation of gears in the conditions of rolling with 30% sliding is simulated. Samples of AMG-10 oil from two producers are analyzed. It is established that with increasing temperature of lubricant for Sample 2 (“Kvalitet-Avia” AMG-10), a long-term restoration of protective boundary films of oil is observed and the period of their formation increases by 2.5 times, causing the implementation of a semidry mode of lubrication at start-up. The total thickness of the lubricating layer is 1.27 times less as compared with Sample 1 ("Bora B" AMG-10 oil), regardless of the lubricant temperature. Also, the rheological properties of the oils have been determined. Sample 1 exhibits low shear stresses at the level of 9.4 MPa and high effective viscosity, 4249 and 5039 Pa·s, at a volumetric oil temperature of 20 and 100 ºС, respectively. For Sample 2, with increasing oil temperature to 100 ºC shear stress increases by 1.15 times and the effective viscosity in contact decreases by 1.53 times. Additives present in Sample 1 are characterized by more effective antiwear properties and thus increase the wear resistance of contact surfaces in the conditions of rolling with sliding thanks to strengthening of the surface metal layers during operation, while Sample 2 undergoes strengthening-softening processes which reduce the wear resistance of friction pairs

The effect of extreme temperatures (70–80°C) on the effluent quality and sludge characteristics of UASB reactors

1997 ◽  
Vol 36 (6-7) ◽  
pp. 325-332 ◽  
Author(s):  
Raghida Lepistö ◽  
Jukka Rintala
Keyword(s):  
Volatile Fatty Acids ◽  
Granular Sludge ◽  
Anaerobic Sludge ◽  
Methanogenic Activity ◽  
Sludge Characteristics ◽  
Effluent Quality ◽  
Start Up ◽  
Thermomechanical Pulping ◽  
Increasing Temperature ◽  
Uasb Reactors

The study focused on the effluent quality and sludge characteristics during the start-up and operation of extreme thermophilic (70 to 80°C) upflow anaerobic sludge bed (UASB) reactors, inoculated with mesophilic and thermophilic granular sludge and fed with acetate, volatile fatty acids (VFA), and thermomechanical pulping (TMP) whitewater. Low effluent quality and long start-up periods were observed during the start-up of the 70 to 76°C, VFA-fed UASB reactors inoculated with mesophilic granulae, while better effluent quality and considerably shorter start-up periods were observed when thermophilic (55/70°C) inocula were used. With VFA feed, a significant amount of acetate was removed at 70°C and even at 80°C, while propionate removal was negligible. With TMP whitewater feed, low VFA effluent concentration was obtained at 70°C. The volatile solids (VS) and the VS/total solids (TS) content of the sludge decreased significantly during the first 2–3 months of operation when mesophilic inocula were used. The initial specific methanogenic activity (ISMA) of the extreme thermophilic sludge decreased with increasing temperature and was slightly higher on glucose than on acetate. At 70 to 80°C, various rod-like bacteria were dispersed through the granulae in either individual or in low density micro colonies surrounded with a varying degree of precipitates.

Rheological properties of ethylene-propylene copolymers at small shear stresses

1982 ◽  
Vol 24 (6) ◽  
pp. 1488-1494 ◽  
Author(s):  
N.P. Zoteyev ◽  
G.M. Bartenev ◽  
N.V. Yermilova ◽  
O.I. Zoteyeva
Keyword(s):  
Rheological Properties ◽  
Shear Stresses ◽  
Ethylene Propylene ◽  
Small Shear

scholarly journals Effects of WMA Additive on the Rheological Properties of Asphalt Binder and High Temperature Performance Grade

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Jiupeng Zhang ◽  
Guoqiang Liu ◽  
Li Xu ◽  
Jianzhong Pei
Keyword(s):  
Critical Temperature ◽  
Rheological Properties ◽  
Asphalt Binder ◽  
Aging Effect ◽  
Asphalt Binders ◽  
Short Term ◽  
Performance Grade ◽  
Temperature Performance ◽  
Effects Of Temperature ◽  
Increasing Temperature

Sasobit additives with different dosages were added into 70# and 90# virgin asphalt binders to prepare WMA binders. The rheological properties, includingG∗andδ, were measured by using DSR at the temperature ranging from 46°C to 70°C, and the effects of temperature, additive dosage and aging onG∗/sin⁡δ, critical temperature, and H-T PG were investigated. The results indicate that WMA additive improvesG∗but reducesδ, and the improvement on 70# virgin binder is more significant.G∗/sin⁡δexponentially decreases with the increasing temperature but linearly increases with the increasing additive dosage. Aging effect weakens the interaction between binder and additive but significantly increases the binder’s viscosity; that is whyG∗/sin⁡δis higher after short-term aging. In addition, the critical temperature increases with the increasing additive dosage, and the additive dosage should be more than 3% and 5% to improve H-T PG by one grade for 70# and 90# virgin binder, respectively.

Friction and Rheological Properties of Meso-Porous MCM-41/Unsaturated Polyester In Situ Composites

2014 ◽  
Vol 599-601 ◽  
pp. 18-21
Author(s):  
Shu Long Hu ◽  
Jian Lv ◽  
Feng Ying Lu ◽  
Hua Shan Liu ◽  
De Ming Zeng
Keyword(s):  
Wear Resistance ◽  
Rheological Properties ◽  
Cetyltrimethylammonium Bromide ◽  
Room Temperature ◽  
Polyester Resin ◽  
In Situ Polymerization ◽  
Unsaturated Polyester ◽  
Roller Milling ◽  
Mcm 41

In this paper, meso-porous MCM-41 was synthesized at room temperature using cationic surfactant cetyltrimethylammonium bromide (CTAB) as the template agent. Then MCM-41/unsatura-ted polyester resin (UPR) materials were prepared by in-situ polymerization with the meso-porous MCM-41. MCM-41/UPR in-situ composites were prepared by roller milling and molding processes. Effects of meso-porous MCM-41 on rheological properties and wear resistance of the MCM-41/UPR composites have been investigated. It is shown that MCM-41 has a diameter in range of 4-5 nm and the pores are highly ordered. MCM-41 can improve the rheological properties and wear resistance of the composites. When MCM-41 content is 2%, the mass abrasion loss is decreased by 37.4%.

What Determines the Peak-Temperature in Binary Ni3Al?

1994 ◽  
Vol 364 ◽  
Author(s):  
C. Rentenberger Karnthaler ◽  
H.P. Karnthaler
Keyword(s):  
Maximum Stress ◽  
Dynamic Recovery ◽  
Al Alloys ◽  
Shear Stresses ◽  
Compression Axis ◽  
Pronounced Change ◽  
Diffusion Controlled ◽  
Ordered Alloys ◽  
Multiple Cross ◽  
Increasing Temperature

AbstractIn Ni3Al alloys the yield stress increases with increasing temperature up to a maximum stress, reached at the temperature TP. Below TP glide occurs on primary octahedral planes whereas above TP glide on primary cube planes is dominating. Therefore this change of glide planes was considered to determine TP.TEM investigations were carried out to study the mechanisms that control TP in Ni3Al specimens with [001] compression axis. In this case no shear stresses are acting on any of the cube glide systems. The TEM results show a pronounced change of the dislocation structure on the {111} glide planes below and above the peak. The breakdown of the barriers (locked screw dipoles) starts when the diffusion is high enough to facilitate their annihilation. The dynamic recovery of the locked screws occurs by multiple cross-slip via octahedral planes. It is proposed that, in this and other ordered alloys, the value of TP is diffusion controlled.

Paper 13: Cavitation and Viscosity between Plain Annular Thrust Surfaces

1967 ◽  
Vol 182 (14) ◽  
pp. 107-111
Author(s):  
B. S. Nau
Keyword(s):  
Shear Rate ◽  
Effective Viscosity ◽  
Thrust Bearing ◽  
Threshold Value ◽  
Mineral Oil ◽  
Operating Conditions ◽  
Shear Stresses ◽  
Face Seal ◽  
Lubricating Film ◽  
The Mean

The configuration investigated corresponds to that of a face-seal or ungrooved parallel-face thrust bearing. Film thicknesses and temperatures, and shear stresses were measured for various operating conditions with mineral oil supplied at low pressure to the inner edges of the annuli. Analysis of the experimental results confirms the importance of the bearing parameter, 6ηω02/ h02, in determining the load carried hydrodynamically. At a given temperature the mean effective viscosity of the lubricating film depends on the shear rate, for values in the range 106–107 s–1, decreasing linearly above a threshold value. The cause of this phenomenon is believed to be cavitation occurring in the film.

scholarly journals Textures in Pure Shear Deformed Rock Salt

1995 ◽  
Vol 24 (1-3) ◽  
pp. 133-141 ◽  
Author(s):  
W. Skrotzki ◽  
K. Helming ◽  
H.-G. Brokmeier ◽  
H.-J. Dornbusch ◽  
P. Welch
Keyword(s):  
Rock Salt ◽  
Room Temperature ◽  
Pure Shear ◽  
Deformation Texture ◽  
Shear Stresses ◽  
Face Centered Cubic ◽  
Taylor Model ◽  
Cubic Metals ◽  
Face Centered ◽  
Increasing Temperature

Texture formation in pure shear deformed rock salt has been studied by neutron diffraction. The textures developed are comparable to those of rolled face-centered cubic metals with high stacking fault energy. At room temperature the texture consists of a strong S and copper and a weaker brass component. It is replaced by static and/or dynamic recrystallization by a strong cube and a subordinate Goss component. Comparison of the experimental textures with simulations based on different models shows that the low temperature high strain deformation texture can be qualitatively well explained by the Taylor model using slip on {110}〈110〉, {100}〈110〉 and {111}〈110〉 systems with equal critical resolved shear stresses. Relaxation with increasing temperature introduces the cube and Goss component, which may represent the nuclei for recrystallization. The study shows that texture simulations on salt without considering recrystallization lead to misleading conclusions.

Tube Transportation of Highly Concentrated Emulsions

2006 ◽  
Author(s):  
Irina Masalova ◽  
Alexander Ya. Malkin
Keyword(s):  
Shear Rate ◽  
Rheological Properties ◽  
Rheological Behavior ◽  
Flow Curve ◽  
Careful Examination ◽  
Shear Stresses ◽  
Time Effects ◽  
Cape Peninsula ◽  
Multi Phase ◽  
Concentrated Emulsions

Tube transportation of highly concentrated emulsions is an important technological process in mining works. Emulsions used for this particular type of application are so-called “liquid explosives” — highly concentrated dispersions of aqueous droplets in a continuous oil phase. The concentration of droplets reaches 96w. %. The width of the inter-phase layers in such a multi-phase system is of the order of nano-level. The length of tube transportation in a real manufacturing process can be of the order of several miles. Hence, the design of the transportation line is of primary technical interest. The practical calculations are based upon comprehensive studies of the rheological properties of highly concentrated emulsions, including an understanding of the role of droplet size, concentration of disperse phase, temperature and time effects (stability of emulsions). Direct measurements were carried out in a wide shear rate range. The results of the measurements indicated that the emulsions under study are rheopectic liquids (viscosity increases over time at a constant shear rate). Their steady flow curve is typical for a visco-plastic medium and is well fitted by the Hershel-Bulkley model. The yield stress is of the order of several tens Pa. The choice of a rheological model is however not crucial for application, since transportation in real technological regimes takes place at high flow rates where the power-type model of flow curves dominates. Systematic studies demonstrated that wall slip is absent over the entire range of the shear stresses under study. This type of rheological behavior was then used for tube transportation design. A more careful examination (based on rheological as well as direct optical observations) also showed that inflation could be observed on the flow curve. It was proven that this type of rheological behavior is related to the two-step mechanism of the flow of a multi-phase liquid. Measurements of normal stresses in shear flows are in accordance with this model of flow. Aqueous droplets in the emulsions under study are super-cooled water solutions of nitrate salts, with the concentration of the latter being of the order of 85%. This system is thermodynamically unstable. The study of time effects (“aging”) showed that slow crystallization in dispersed droplets takes place. This leads to the evolution of the rheological properties of emulsions that can be treated as an emulsion-to-suspension transition. The work was carried out in the Flow Process Research Center, Engineering Faculty, Cape Peninsula University of Technology, Cape Town, Republic of South Africa.

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