Publications

Validation of finite element models using experimental data with unknown boundary conditions proves to be a significant obstacle. For this reason, the boundary conditions of an experiment are often limited to simple approximations such as free or mass loaded. This restriction means that vibration testing and modal analysis testing have typically required separate tests since vibration testing is often conducted on a shaker table with unknown boundary conditions. If modal parameters can be estimated while the test object is attached to a shaker table, it could eliminate the need for a separate modal test and result in a significant time and cost savings. This research focuses on a method to extract fixed base modal parameters for model validation from driven base experimental data. The feasibility of this method was studied on an Unholtz-Dickie T4000 shaker and slip table using a mock payload and compared with results from traditional modal analysis testing methods. © The Society for Experimental Mechanics, Inc. 2012.

In modal testing, the most popular tools for exciting a structure are hammers and shakers. This paper reviews the applications for which shakers have an advantage. In addition the advantages and disadvantages of different forcing inputs (e.g. sinusoidal, random, burst random and chirp) that can be applied with a shaker are noted. Special considerations are reported for the fixtures required for shaker testing (blocks, force gages, stingers) to obtain satisfactory results. Various problems that the author has encountered during single and multi-shaker modal tests are described with their solutions.