STRUCTURAL VIBRATION ANALYSIS & DAMPING BY CF BEARDS BOOK
STRUCTURAL VIBRATION ANALYSIS & DAMPING BY CF BEARDS BOOK
KINDLY SCROLL DOWN AND DOWNLOAD
short description about the book
A structure is a combination of parts fastened together to create a supporting framework, which may be part of a building, ship, machine, space vehicle, engine or Some other system. Before the Industrial Revolution started, structures usually had a very large mass because heavy timbers, castings and stonework were used in their fabrication; also the vibration excitation sources were small in magnitude so that the dynamic response of structures was extremely low.
Furthermore, these constructional methods usually pro- duced a structure with very high inherent damping, which also gave a low structural response to dynamic excitation. Over the last 200 years, with the advent of relatively strong, lightweight materials such as cast iron, steel and aluminium, and increased knowledge of the material properties and structural loading, the mass of structures built to fulfil a particular function has decreased.
The efficiency of engines has improved and, with higher rotational speeds, the magnitude of the vibration exciting forces have increased.
This process of increasing excitation by reducing the structural mass and damping has continued at an increasing pace to the present day when few if any, structures can be designed without carrying out the necessary vibration analysis, if they are dynamic performance is to be acceptable.
The vibration that occurs in most machines, structures and dynamic systems is undesirable, not only because of the resulting unpleasant motions, the noise and the dynamic stresses which may lead to fatigue and failure of the structure or machine but also because of the energy losses and the reduction in performance that accompany the vibrations. It is therefore essential to carry out a vibration analysis of any proposed structure.
All real structures consist of an infinite number of elastically connected mass elements and therefore have an infinite number of degrees of freedom; hence an infinite number of coordinates are needed to describe their motion. for more visit
This leads to elaborate equations of motion and lengthy analyses. However, the motion of a structure is often such that only a few coordinates are necessary to describe its motion.
This is because the displacements of the other coordinates are restrained or not excited, being so small that they can be neglected.
Now, the analysis of a structure with a few degrees of freedom is generally easier to carry out than the analysis of a structure with many degrees of freedom, and therefore only a simple mathematical model of a structure is desirable from an analysis viewpoint.
- Although the amount of information that a simple model can yield is limited, if it is sufficient then the simple model is aequate for the analysis.
- Often a compromise has to be reached, between a comprehensive and elaborate multi-degree of freedom model of a structure which is difficult and costly to analyse but yields much detailed and accurate information, and a simple few degrees of freedom model that is easy and cheap to analyse but yields less information.
- However, adequate information about the vibration of a structure can often be gained by analysing a simple model, at least in the first instance.
- The vibration of some structures can be analysed by considering them as one degree or single degree of freedom system; that is, a system where only one coordinate is necessary to describe the motion. Other motions may occur, but they are assumed to be negligible compared with the coordinate considered.
COMMENTS