The paper “ Theory of Unbalanced Vibration, Theory of Balancing, Determination of Unbalanced Mass” is a meaty version of a lab report on engineering and construction. Balancing is a crucial aspect of all mechanical systems particularly rotating mechanical elements, such as wheels, flywheels, shafts, pulleys, and gears among others. Unbalance in rotating elements of machines is usually a primary source of unbalanced vibrations, due to the development of unbalanced forces in rotating systems. Unbalanced forces create excessive vibrations that ultimately lead to premature failure of machine components and the entire machine system especially when unbalanced vibrations from rotating elements are transmitted to other parts of the machine system.
For example, vibrations from an unbalanced propeller shaft of an automotive can be transmitted to the body of the automotive, which will result in wearing out of the entire automotive. The magnitude of unbalanced forces and hence the intensity of unbalanced vibrations increases with an increase in rotation speeds. This project seeks to study the impact of unbalanced mass, eccentricity, and speed on unbalanced vibrations. Theory of Unbalanced VibrationThere are various sources of unbalanced vibrations in machine components including nonuniform machine wear, repairs, and production defects. Nonuniform machine wears: the occurrence of nonuniform wearing of machine components result in unbalanced masses within the respective component, which leads to unbalanced forces when the component is rotating.
This is usually prominent in automotive wheel rims where nonuniform wear, which leads to unbalanced vibrations, result from impact with hard objects. Repairs: repairs should be properly carried out to avoid unbalanced masses after the repair work. During several instances, vibrations from unbalanced forces usually begin after the first repair work on a machine component, such as a shaft.
These vibrations intensify with subsequent repair works wherein the rate of repair work on the respective component increases due to unbalanced vibrations. For example, repairing a broken shaft through welding can result in unbalanced vibrations especially if the shaft is not checked for balance. Production flaws: especially when a production unit does not have sufficient equipment for checking and ensuring that machine components are balanced. Unbalanced vibrations are usually eliminated through balancing, which is usually done on rotating machine elements, such as wheels.
During balancing, the existence of unbalanced vibrations is established and the masses causing unbalanced vibrations, alongside their relative position from the component’ s center of rotation. Technically, the distance between the unbalanced mass and the center of rotation of the component is known as eccentricity (e). The determination of unbalanced mass and eccentricity is followed by the addition of well-determined masses at strategic positions relative to the center of rotation of the component. The added mass (balancing mass) helps to distribute the mass of the component evenly to eliminate or reduce unbalanced vibrations. The intensity of unbalanced vibrations is not only dependent on the unbalanced mass and its distance from the center of rotation of the component, but also on the angular speed of rotation of the rotating component (Haddow 28).
Research experiments have shown that steady-state vibrations arising from unbalanced masses are proportional to the amount of the unbalanced mass (m) and its eccentricity (e) (Srinivas and Srinivas 95). Research experiments also show that steady-state unbalanced vibrations arising from unbalanced masses are proportional to the square of the rotation speed of the component under consideration (Haddow 28).
This means, therefore, that unbalanced vibrations increase with an increase in rotation speed. This is perhaps the concept of critical speed of rotation beyond which machine operation can be dangerous because it can lead to mechanical breakdown due to excessive vibrations. This is especially the case when unbalanced vibrations are beyond the bearing capacity of the rotating component, which depends on material properties and component geometry.
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