On the Effect of Oil Contamination on the Performance of Plain Journal Bearings

Peer reviewed: YesNRC publication: Ye

Comparison of the steady-state and dynamic performance of two fixed-geometry journal bearings

This paper evaluates two different journal bearings: a cylindrical bore plain journal bearing and a tri-lobe taper land bearing. Each bearing has the same nominal diameter (89 mm) and aspect ratio (L/D = 0.7). The shaft rotational speed ranged from 6krpm to 14krpm and the bearing specific load from 700kPa to 2800kPa. The bearings' steady-state performance is evaluated according to relative bearing and shaft displacement, bearing operating temperature and power loss. A frequency-domain analysis is used to determine bearing rotordynamic coefficients - it treats the bearing as a mass-spring-damper system. Excitation frequencies range between 20Hz and 350Hz. Ultimately, the tri-lobe taper land bearing offers better stability whereas the cylindrical bore plain journal bearing has a lower eccentricity and runs cooler for a given operating condition. The dynamic properties of the two bearings are found to be similar, although the higher stability of the tri-lobe taper land bearing is also reflected in the dynamic coefficients. Copyright \ua9 2011 by ASME.Peer reviewed: YesNRC publication: Ye

A comparison study between acoustic sensors for bearing fault detection under different speed and load using a variety of signal processing techniques

The use of ultrasonic sensor technology to detect incipient and evolving defects in rotating components such as bearings and gears is more desirable due to their high resolution. In a previous study, the sensitivity of a variety of sensors including an air-coupled ultrasound transducer to bearing faults was analyzed and thoroughly discussed. This article investigates the effectiveness of two ultrasonic sensors, namely, air-coupled and piezoelectric ultrasound transducers for rolling element bearings damage diagnostics. The former is a noncontact sensor and the latter is a contact sensor. An accelerometer was also used as the baseline sensor for comparison purposes. A series of tests was carried out on a laboratory test rig running with defective and undamaged healthy bearings under variable shaft speeds and several radial loads. The data were analyzed using selected signal processing techniques covering time, frequency, and advanced joint time-frequency domains. The results showed that certain acoustic features were responsive to the variation of operational condition and the damage; the detection capability of the sensors varied depending on the defect size, its location, as well as the applied signal analysis technique. \ua9 2011 Crown Copyright.Peer reviewed: YesNRC publication: Ye

Sensitivity of tilting pad journal bearing performance characteristics to manufacturing tolerances

Peer reviewed: YesNRC publication: Ye

Characteristics of a Hydrodynamic Fixed Geometry Thrust Bearing: Comparison Between Experimental Data and Numerical Results

Peer reviewed: YesNRC publication: Ye

Tribological characterization of plasma sprayed CoNiCrAlY-BN abradable coatings

The processing conditions, microstructural and tribological characterizations of plasma sprayed CoNiCrAlY-BN high temperature abradable coatings are reported in this manuscript. Plasma spray torch parameters were varied to produce a set of abradable coatings exhibiting a broad range of porosity levels (34-62%) and superficial Rockwell hardness values (0-78 HR15Y). Abradability tests have been performed using an abradable-seal test rig capable of simulating operational wear at different rotor speeds and seal incursion rates. These tests allowed determining the rubbing forces and quantifying the blade and seal wear characteristics for slow and fast seal incursion rates. Erosion wear performance and ASTM C633 coating adhesion strength test results are also reported. For optimal abradability performance, it is shown that coating hardness needs to be lower than 70 and 50 HR15Y for slow and fast blade incursion rate conditions, respectively. It is shown that the erosion wear performance, as well as, the coating cohesive strength is a function of the coating hardness. The current results allow defining the coating specifications in terms of hardness and porosity for targeted applications.Peer reviewed: YesNRC publication: Ye

Numerical Study of the Sensitivity of Tilting Pad Journal Bearing Performance Characteristics to Manufacturing Tolerances: Steady State Analysis

NRC publication: Ye

Sensitivity of Tilting-Pad Journal Bearing Performance to Manufacturing Tolerances: Dynamic Properties

Peer reviewed: YesNRC publication: Ye

Probabilistic analysis of slope stability towards the slip by the kinematic method

AbstractThe analysis of slope stability or a slope is a complex problem that requires careful reflection and common sense. In effect because of the diversity of sites and especially their heterogeneity, each case is unique, the stability check is done by studying the general failure along the slip surface that is superficial, shallow, deep or very deep by conventional methods found in the literature such as the Bishop method, Jumbu, Fellenius etc. ... based on the determination of global minimum factor of safety.In this paper, we propose a mechanical model for calculating the failure along the sliding surface based on the kinematic method of rigid solids (Limit analysis).The statistical-probabilistic concept of safety is a very useful tool for comparison because it reflects the dispersion of random parameters (geometry, intrinsic characteristics of the soil load, etc. ...) will be applied to this model, the reliability of the system will expressed using the reliability index.The introduction of the concept of reliability index Geotechnical is a valuable tool capable of giving the engineer a greater objectivity in the design of slopes.We determine the critical slopes and the corresponding costs from the state equation R-S=0 limit of the present mechanism. Finally recommendations will be given for modeling the failure along the sliding surface [10]