Control of vibrations in rotating mechanical elements

Abstract

We observe commonly disturbances in rotating machinery elements when driven to rotate. These disturbances present themselves as a displacement or trepidation caused by unbalanced masses. The occurrence of balancing depends on eccentricity present, which means that the center of mass and rotating element center are not coincident. The presence of these unbalanced forces - whose magnitude is proportional to the eccentricity, unbalanced mass, and the angular velocity squared - results in severe vibrations and can overload bearings with catastrophic consequences. The main origin of these unbalances is the heterogeneous distribution of the masses around the rotation axis. So, to avoid the overload on bearings and warp the shaft, some control methods such as balancing should be done. In the present work, a dynamic balancing was carried out with a specimen employing a balancer rig. In this experiment, different auxiliary equipment, computer systems, and proprietary software were used. It was possible with this software to automate the measurements, analyze, and obtain a report about balancing results as well. The specimen was made of steel and possessed two mounted nylon disks with oblong holes on them. These oblong holes permitted the fixation of trial masses and correction masses. The degree of balancing quality was determined according to the ISO standard G 6.3; these degrees of balancing guarantee an accuracy level of quality according to the specific application in rotating machines. The balancing on the specimen was correctly applied, and the results have demonstrated that this procedure, balancing, is essential to mitigating excessive vibration and preventing overload in bearings caused by unbalancing in rotating mechanical elements.

Keywords

• unbalancing
• eccentricity
• vibration