الفهرس 
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Abstract
Journal bearings are considered one of the most important components of the rotary equipment’s, as it is responsible for cartying the heavy rotating parts like the shafts of Gas turbines, steam turbines, cutting equipment’s, and engines in general.
Researchers began to focus on this important part, and various researches were done on it whether to improve its performance by the improvement of the oil characteristics, oil distribution, lubrication methods, and pressure inside the bearing also, decreasing the temperature inside the bearing, or to improve its dynamic performance by reducing the vibration of the bearing, as any rotating part produces vibration levels on the bearings. Various researches were done to improve the dynamic response of the journal bearing; every researcher studied it from a different way, whether the internal design, or the outer design, or the fixation method.
this research aims to study the effect of asperity journal bearing in damping the vibration levels compared to the normal one, so we cut the internal surface of the bearing as squares equal in dimensions and with depth equal to the length of the rectangle using the thread of the lathe for the ribs parallel to the circumference of the bearing and the dividing instrument of the horizontal milling machine for the vertical ribs.a cutting tool with a thickness of 0.25 mm was used because it is equal to half of the lathe thread step, also the clearance between the shaft and the bearing was set to 0.05 mm.an apparatus was made containing: an electric induction motor with 3000 r/min, two bearings, a shaft with 500 mm diameter and circular disc weighting 73.57 N fixed in the center of the shaft.
Load is changed by changing the weight attached to the disc uni formally as (112.8- 152.5 ¬191.3)N , also the speed of the shaft is changed by controlling the source voltage. Also, an oil circuit with 0.5 bar is used to deliver the oil to the bearings and to monitor the oil temperature and the metal temperature to have a suitable and constant operation. We perform various measurements on the bearings on two stages, the first one is normal journal bearing, four measurements are taken in this stage for the for weights.at the beginning, weight 73.57 N is used and weights are changed, at every weight we perform a hammer test to determine the resonance periods, also a run-up test is performed. We measure vibration from 200 r/min till 3000 r/min with step of increasing 100 rlmin, FFT Spectrums and overall measurements are taken for every speed. We measure vibration in the vertical position on the bearing near to the coupling. The second stage is the asperity journal bearing, all previous measurements are taken in this stage. finally, we compare the four readings for every stage (normal- asperity) and compare the whole readings to to compare the behavior of the two bearings to get the effect of the asperity modification.