Variable modal parameter identification for non-linear mdof systems. Part II: Experimental validation and advanced case study

The purpose of Part II is to provide an experimental validation of the meth odology presented in Part I and to consider a representative engineering ca se, the study of which requires a relatively large numerical model. A beam system with cubic stiffness type non-linearity was used in the experimental study. The non-linear response was measured at three locations and the und erlying linear system was obtained via linear modal analysis of low-excitat ion response data. The non-linear parameter variations were obtained as a f unction of the modal amplitude and the response of the system was generated for other force levels. The results were found to agree very well with the corresponding measurements, indicating the success of the non-linear modal analysis methodology, even in the presence of true experimental noise. An advanced numerical case study that included both inherent structural dampin g and non-linear friction damping, was considered next. The linear finite e lement model of a high-pressure turbine blade was used in conjunction with three local non-linear friction damper elements. It was shown that the resp onse of the system could be predicted at any force level, provided that tha t non-linear modal parameters were available at some reference force level. The predicted response levels were compared against those obtained from re ference simulations and very good agreement was achieved in all cases.