Dear students, the purpose of this textbook is to give you an insight into the area of measuring vibrations and the use of measuring vibrations in vibration diagnostics. Vibration diagnostics is one of the non-destructive methods used for condition monitoring of machines in operation. All the machines while operating vibrate more or less, and with most of them the vibrations are unwanted and the effort is to minimize them. Only with some types of machines, vibrations are directly a working principle of the machine and are caused deliberately (e.g. vibrating screeners). Though, this group of machines is not of interest to vibration diagnostics. Diagnostic work can be thought of by analogy with activities of a practising physician who during preventive inspection detects and evaluates one's medical condition. Basically, three situations can occur: You will learn that 1) you are healthy and you can live as before, 2) you have high blood pressure and you should start taking the medication for its reduction and/or change your lifestyle, or 3) your condition requires hospitalization and a more detailed examination and/or a surgery. Machines are at exactly the same situation. Based on a diagnostician’s assessment they can either continue in operation, or a tiny intervention is necessary, or they need to be shut down and repaired thoroughly. Purpose of all this is, in case of both humans and machines, to save the cost of repair or to prevent a disaster and its associated costs. As the name vibration diagnostics suggests, machine condition is diagnosed on the base of an analysis of vibration. Successful application of vibration diagnosis requires in practice staff with considerable degree of knowledge and experience. Routine work in data collection may be carried out by trained personnel without academic qualifications, but data processing and assessment of the state of a machine is a task for an engineer who has knowledge in various areas (design of machines, dynamics, mathematics, signal processing, etc.) and who is able to use this knowledge in context. A graduate in Applied Mechanics specialization is an ideal candidate for becoming a skilled vibration diagnostician after several years of practice. This text is almost your first encounter with the experimental mechanics. We believe that we will convince you that it is a beautiful and promising area which should become an integral part of your engineering practice and mastering of which will contribute to your becoming a full member of the team of experts addressing complex technical problems
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DRAG (from un modele de la Demande Routiere, des Accidents et leur Gravite) is a complex computer model that simulates accident propensities under detailed conditions. The DRAG approach constitutes the largest road accident modelling effort ever undertaken. Gaudry is the creator and developer of DRAG and this work explains its nature, purpose and value. Such a model, which explains accidents for a whole region, province or country, has advantages in answering many questions asked about accidents (such as the role of the economic cycle, weather, prices, insurance etc.) that other models fail to take fully into account.
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Fractured rocks extend over much of the world, cropping out in shields, massifs, and the cores of major mountain ranges. They also form the basement below younger sedimentary rocks; at depth; they represent a continuous environment of extended and deep regional groundwater flow. Understanding of groundwater flow and solute transport in fractured rocks is vital for analysis of water resources, water quality and environmental protection, geotechnical and engineering projects, and geothermal energy production. Book chapters include theoretical and practical analyses using numerical modelling, geochemistry, isotopes, aquifer tests, laboratory tests, field mapping, geophysics, geological analyses, and some unique combinations of these types of investigation. Current water resource and geotechnical problems in many countries—and the techniques now used to address them—are also discussed. The importance of geological interpretation is re-emphasised in analysing the hydrogeology of fractured, mostly crystalline rocks and in how critical this is for understanding their hydrology and the wise utilisation of resources. This is indeed hydrogeology in its broadest sense. The importance of, but great difficulty in, extending or upscaling fractured rock hydraulic properties is also made clear.
This book is aimed at practicing hydrogeologists, engineers, ecologists, resource managers, and perhaps most importantly, students and earth scientists not yet familiar with the ubiquity and importance of fractured rock systems.
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There have been stability theories developed for beams, plates and shells the most significant elements in mechanical, aerospace, ocean and marine engineering. For beams and plates, the theoretical and experimental values of buckling loads are in close vicinity. However for thin shells, the experimental predictions do not conform with the theory, due to presence of small geometric imperfections that are deviations from the ideal shape.
This fact has been referred to in the literature as 'embarrassing', 'paradoxical' and 'perplexing'. Indeed, the popular adage, "In theory there is no difference between theory and practice. In practice there is", very much applies to thin shells whose experimental buckling loads may constitute a small fraction of the theoretical prediction based on classical linear theory; because in practice, engineers use knockdown factors that are not theoretically substantiated.
This book presents a uniform approach that tames this prima-donna-like and capricious behavior of structures that has been dubbed the 'imperfection sensitivity' thus resolving the conundrum that has occupied the best minds of elastic stability throughout the twentieth century.
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The goal of the Detailed Analysis is to use all available tools to develop accurate projections of potential ground-borne vibration impact and, when necessary, to design mitigation measures. This is appropriate when the General Assessment has indicated impact and the project has entered the final design and engineering phase. It may also be appropriate to perform a Detailed Analysis at the outset when there are particularly sensitive land uses within the screening distances. Detailed Analysis will require developing estimates of the frequency components of the vibration signal, usually in terms of 1/3-octave-band spectra. Analytical techniques for solving vibration problems are complex and the technology continually advances. Consequently, the approach presented in this chapter focuses on the key steps usually taken by a professional in the field.
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REVIEW OF VIBRATION ANALYSIS METHODS FOR GEARBOX DIAGNOSTICS AND PROGNOSTICS
Author: Mitchell Lebold, Katherine McClintic, Robert Campbell, Carl Byington, and Kenneth Maynard Applied Research Laboratory The Pennsylvania State University | Size: 455 KB | Format:PDF | Quality:Unspecified | Publisher: Proceedings of the 54th Meeting of the Society for Machinery Failure Prevention Technology, Virginia Beach, VA, May 1-4, 2000, p. 623-634. | pages: 12
Vibration analysis for condition assessment and fault diagnostics has a long history of application to power and mechanical equipment. The interpretation and correlation of this data is often cumbersome, even for the most experienced personnel, and thus automated processing and analysis methods are sometimes sought. As such, statistical features are commonly used to provide a measure of the vibration level that can be compared to a threshold value indicative of a failed cond ition.
Many feature vectors have been developed over the years and are well documented in the literature. What is not clear from the literature is the details associated with each feature so that the results are consistent among users. Preprocessing is vaguely stated and terms, such as “residual signal”, are commonly used yet can mean different techniques. An attempt has been made to define the terms, establish the preprocessing needed for each feature, and provide the details needed to produce consistent results.
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The vibration response of piled foundations to inertial and underground railway induced loadings
Author: Pieter COULIER | Size: 5.1 MB | Format:PDF | Quality:Unspecified | Publisher: ENGINEERING DEPARTMENT MECHANICS, MATERIALS AND DESIGN DYNAMICS AND VIBRATION TRUMPINGTON STREET CB2 1PZ CAMBRIDGE UK | pages: 123
Vibrations and re-radiated noise in buildings induced by (underground) railway traffic are a major environmental concern. Vibrations are generated at the wheel-rail interface and propagate through the soil into buildings, where they cause annoyance to inhabitants. During the last decades, a lot of research has been performed to search for efficient and cost-effective vibration countermeasures. This dissertation is concerned with the dynamic behaviour of piled foundations. A model for piled foundations which accounts for the fundamental behaviour of each pile and the interaction between neighbouring piles, through wave propagation in the soil, is developed. It is a boundary element
model, formulated in the frequency domain, based on an existing single pile model.
The model is used to validate the Pipe-in-Pipe (PiP) model for piles, a computationally efficient model
for piled foundations based on the homonymic model for vibrations from underground railways. The
models are found to be in good agreement, which offers great perspectives to use the PiP model as an
engineering tool.
The influence of adjacent piles on the response of a certain pile is investigated by means of a power
flow analysis. It will be demonstrated that the effect is strongly dependent on the relative positions
of the piles compared to the position of the load applied. Moreover, a tendency to wave scattering is
revealed when the wavelength approaches the distance between piles and load.
Ultimately, the response of piled foundations to underground railway induced loadings is investigated.
Uncoupling of source (railway track) and receiver (piled foundations) is assumed, resulting in a two-step approach. The model is once more used to validate the PiP model for piles. Several aspects, such as the effect of the foundation design, the contribution of horizontal and rotational motion, the importance of pile-soil-pile interactions and the isolation performance of base isolation are examined. Results suggest that steel springs are preferred to rubber bearings, as the isolation frequency can be lowered more significantly. Moreover, it will become clear that the current boundary element model has the ability to reveal the complexity of the situation, which cannot be achieved by means of simplified
models.
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