Vibration and shock of engineered structures occur due to dynamic loads arising during operation, e.g. in transportation vehicles, motors/generators and buildings. Analytical and numerical prediction tools are required during virtual prototyping to design structures to withstand their in-service loads, whilst experimental techniques are generally applied to scale models, components and assembled structures for model validation, parameter estimation and trouble-shooting purposes. By the end of this module you will have gained an appreciation for commonly occurring vibration and shock phenomena and the predictive and experimental tools available to design and mitigate against them.
Whilst focussed on industrial tools of the trade, this module begins briefly with analytical descriptions of beams and plates. Such simple structural components often prove useful qualitative models in practical situations and provide helpful insight into vital concepts. For quantitative predictions, finite element (FE) analysis is universally used to obtain mass and stiffness matrices of distributed and complex structures. FE analysis is introduced briefly but the emphasis is on analysis options available in commercial software for condensing such models, computing modal and harmonic solutions and incorporating damping.
Common sources of vibration are discussed, and methods are met for characterising and modelling sources. Two specific and ubiquitous examples are considered in detail: random excitation, which has implications for structural fatigue, and rotating machinery.
The most commonly used experimental technique is that of transfer function measurement, from which modes of vibration can be inferred. Almost invariably, transfer functions are measured using either an instrumented hammer test or a shaker test, both of which enable the structure to be excited in a controlled and measurable way. Both techniques are discussed in detail, and you will become competent at hammer testing through a practical laboratory. Another type of vibration testing concerns the structural integrity of components and structures that are subjected to large dynamic loads, such as electronic equipment during a rocket launch. Commonly used standards for such tests are outlined, and a visit to a commercial test facility may be possible.
Pre-requisites: FEEG2002 or ISVR6141