1,721,117 research outputs found
The Lagrange multiplier method revisited for free and forced vibration of a constrained structure
No full textNonlinear systems for vibration control
No full textPassive vibration control measures typically involve either introducing separately or in a combination changes to a system, such as adding damping or dissipation, stiffness and mass. This presentation will explore two particular application areas namely isolation and the use of a vibration absorber. For isolation the typical passive system has limitations, so research has been conducted into introducing nonlinear characteristics which include friction, nonlinear viscous damping and switchable stiffness changes. In some scenarios these provide additional benefits, albeit that the systems now become nonlinear, and the philosophy behind their consideration will be presented. The analysis of these configurations will then be accompanied with numerical simulations and experimental validation to clarify how and why things are different. More recently there has been some interest in the use of a nonlinear vibration absorber. A summary of some progress to date in this field, including theoretical and experimental work, will be given. Suggestions and guidelines for its potential will be explored as will issues that might make its general adoption difficult<br/
Modelling the vibrational characteristics and radiated sound power for a Y25-type bogie and wagon
No full textA theoretical investigation has considered the vibrational characteristics of the bogie and wagon to quantify the noise freight wagons. This study presents the analysis of the bogie by finite element methods (FEM) to cover the lower-frequency range. The wagon has been analyzed using a statistical energy analysis (SEA) approach. The accelerances on the bogie have been calculated and the sensitivity to excitation evaluated. The calculation of sound power for force inputs has also been determined. Complementary experimental results show the predictions to be in good agreement. The wagon has not been examined specifically to identify detailed response and radiated sound; instead it is possible to consider the response of larger identifiable structural areas such as the doors, walls, roof, etc. The response of these larger areas can also be used to predict the transfer functions from radiated sound power for forces applied at the connection points. Good agreement has been obtained with experimental measurements
FEM-MBS techniques for stress concentration, prediction and accelerated durability simulation under dynamic loading
No full textWavenumber estimation: further study of the correlation technique and use of SVD to improve propagation direction resolution
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Analysis of energy dissipation in an elastic moving string with a viscous damper at one end
No full textIn this paper transverse vibration of an axially moving viscoelastic string with a viscous damper at one end is investigated analytically. The string is assumed to be travelling with constant velocity and the length of string is constant or time varying. The linear and nonlinear mathematical models are derived using the Lagrangian function and implemented using a finite element method. The method considers a time varying state space function applied to the linear model, the Newmark-Beta method is used to solve the response for the nonlinear problem numerically. The case of energy dissipated by a viscoelastic damper at one end of the string for different axial string velocities is considered. When a disturbance arrives at the boundary an exact value for the damper which provides maximum energy dissipation is investigated. Finally, numerical simulations are presented to establish the feasibility of the metho
Issues and conflicts of combining MSc modules and industrial short courses
No full textIn a specialist field, such as acoustics, where noise and vibration control is promoted through legislation and competition in product refinement, etc., there is persistent
industrial demand for courses. Skills shortages in the UK workforce can only readily and practically be met by the running of graduate level short courses. In addition, for
chartered engineers such courses are very appropriate for Continuing Professional Development (CPD) requirements. This paper considers the option of postgraduate short course training in combination with MSc module provision, i.e. when the latter
can be given in a short course format and duration.
Curriculum content has to be a balance of analytical and mathematically demanding material with the underlying physical and applied principles being taught. It is complicated by the varied background of the students and the industrial delegates.
The latter often see the vocational training or skills development as the outcomes rather than education as the benefit in the longer term. Issues such as the selection of appropriate methods of assessment and the alignment or distinction of learning outcomes for different cohorts are briefly discussed. The short course format develops a different learning and cohort experience, which has also necessitated a radically different delivery. Practical work often accounts for 50% of contact time and ranges from simple demonstrations of physical phenomena to industrially relevant problems. Some discussion on forms of assessment which might be suitable or possible for the external engineers in a mixed cohort is also briefly considere
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