VIBRATIONS

Author: CORREA VELEZ SANTIAGO.
Year: 2005.
University: POLITÉCNICA DE MADRID [www.upm.es].
Place of defense: E.T.S. ING. INDUSTRIALES.
Place of preparation: E.T.S. ING. INDUSTRIALES.

Summary: This thesis presents the development of acoustic elements in movements based on a principle Variacional Parametrizado for domains in two and three dimensions. Items made with this technique have a high reliability in predicting numerical acoustic phenomena, especially the problem of interaction fluido-estructura. This assertion has been corroborated through laboratory experiments that establish a correlation between the experimental results and numerical which is within the margin of error accepted engineering. These elements have been developed based on a specific need. The stranding and deaths of cetaceans (especially Zifios Cuvier) coincident with military exercises is a recurring phenomenon in recent years in different parts of the world. The use of mid-range sonar, which is common during the execution of the maneuvers, it has been linked to deaths, as they have been found syndromes possibly derived from acoustic trauma. This research provides, through the development of numerical models of the external auditory organs of the animal data supporting this hypothesis. These models have been developed using the finite element method, and more specifically the elements presented in this investigation.

Author: ECHAVARRI OTERO JAVIER.
Year: 2005.
University: POLITÉCNICA DE MADRID [www.upm.es].
Place of defense: E.T.S. ING. INDUSTRIALES.
Place of preparation: E.T.S. ING. INDUSTRIALES.

Summary: This thesis has been developed in the Division of Engineering Machinery belonging to the Higher Technical School of Industrial Engineers of the Polytechnic University of Madrid and has been promoted and financed by Repsol-YPF, interested in having a tool for predicting the behavior of their dampers in commercial lubricants, in order to develop lubricants where unlisted noise adherencia-deslizamiento. In a system buffer contacts tribológicos that there may introduce vibrations into the system, under certain operating conditions. A high friction in these contacts can generate vibrations adherencia-deslizamiento and very annoying noises. There is insufficient information on how these phenomena occur and there is no specific evidence, between the multiple trials are conducted dampers before marketing. In the thesis is presented initially behavior contacts dry, to see how there is the phenomenon of adherencia-deslizamiento and how focuses his study on the precedents studied. The better understanding of the causes of this phenomenon and the possibility of occurrence in some systems, aims to discern which of the noise produced shock absorbers are due to an inadequate friction, and to study the influence that corresponds to such noises and lubricant the attributable to the designs of the shock absorbers. Of the different types of contacts in the business dampers, is the scion in his movement lubricated contact with the main roadblock agent that can produce adherencia-deslizamiento with successive periods of grip and take-off of the lip of the oil seal to the stem. The study was conducted by esquematización of the elements involved (rod, catch the lip and body damper), and presents a model of conduct applicable to any movement of the stem of a hydraulic shock absorber. The force of friction on contact between stem and catch is through modeling curve Stribeck. It explores on the one hand curve Force Base and transmitted by another force ripple that overlaps with the previous one to know the possibility of occurrence of adherencia-deslizamiento in the movement of the shaft damper. For a general case, the result is composed of three sections of differential behavior, corresponding to the path of the rod between two points in zero speed: initial area, middle and the end zone. Besides analyzing the possibility of changing stretch of behavior during sliding given by the curve Stribeck, and the effect it produces. For the model is easily applicable, it works in the middle of moving rod, which can be assumed that he has a constant speed. This area used to characterize the fundamental properties of the lubricant from a few simple tests. Moreover, through tests or catch the lip of the entire damper oil can be extracted without the fundamental characteristics of the shock involved in the phenomenon. With these two types of data (and the oil shock), you can implement the proposed model to predict the behavior before adherencia-deslizamiento a pair of shock and oil. You can predict the interval velocity that occurs, its breadth and frequency. The model was validated experimentally using different lubricants, checking the outcomes measured in them and those projected by the model. As a result, it was finally exposed the major contributions of the thesis and lines of research proposals for the future.

Author: MATEOS PRIETO JUAN BORJA.
Year: 2005.
University: POLITÉCNICA DE CATALUÑA [www.upc.edu].
Place of defense: ETSEIB.
Place of preparation: ETSEIB, PAVELLÓ D Campus SUD.

Author: MATEOS PRIETO JUAN BORJA.
Year: 2005.
University: POLITÉCNICA DE CATALUÑA [www.upc.edu].
Place of defense: ETSEIB.
Place of preparation: ETSEIB, PAVELLÓ D Campus SUD.

Author: CORTÉS MARTÍNEZ FERNANDO.
Year: 2006.
University: MONDRAGÓN UNIBERTSITATEA [www.mondragon.edu].
Place of defense: MONDRAGON GOI ESKOLA POLITEKNIKOA.
Place of preparation: GOI ESKOLA POLITEKNIKOA-MONDRAGON UNIBERTSITATEA.

Summary: In memory of this thesis summarizes research on the reduction in the structural vibration, particularly in systems that employ techniques of passive damping through surface coatings with visco-elastic materials. In this context, we have developed a series of numerical methods, both for the time domain to the frequency, including uniform models for structural beams, coated viscoelástico, which are intended to simplify the work of engineers who faced with the challenge of improving the performance of their products in terms of the durability of the components, the reduction of radiation noise, the increased comfort or security enhancements. It has also proposed an experimental technique that facilitates the identification of the mechanical properties of materials viscoelásticos.