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Subject of the present work is the enhancement of the buckling load of beam-type structures under a compressive force by means of active feedback control. The focus of this paper lies on experimental aspects that show the feasibility of the proposed approach. For this purpose, a cantilever beam loaded by a compressive force is considered. The compressive force is applied with the help of a cable which is fixed at the tip of the free end and passes through the foundation of the cantilever. A laser displacement sensor is used to measure the structural displacements at the beam's tip. For actuation, piezoelectric transducers are attached on each side of the cantilever beam. Two kinds of constant gain feedback control approaches are investigated on the experimental setup. The buckling load could be increased by a factor of 2.05. The experimental results agree very well with the performed numerical simulations. As a theoretical basis, a consistent theoretical formulation is presented using the Bernoulli-Euler beam theory. The formulation of the system includes also a general feedback controller with discrete displacement measurements and distributed piezoelectric patches. The influence of the controller on the buckling load, control amount by means of applied voltage and limits of the investigated active buckling control approaches are emphasized. [ABSTRACT FROM AUTHOR]

The aim of this paper is to highlight and identify the influencing parameters of the nonlinear behavior of highly deformable structures. Therefore, as an example, a large deformable square frame consisting of four slender members of equal length has been investigated experimentally. Based on highly resolving measurements using the digital image correlation method (DIC), the inverse problem of nonlinear system identification has been solved by an automatic parameter identification algorithm. For this purpose, a numerical model is set up with a beam finite element model using the absolute nodal coordinate formulation (ANCF), which enables the modeling of geometrical and possible material nonlinearities. The influencing parameters as well as the system properties have been determined by using a genetic optimization algorithm. The impact of the main influencing parameter is carved out by an included sensitivity study. The final model with automatically identified parameters shows high agreement with the experimental setup. With this approach the influences and nonlinearities, e.g. material parameters, rigid behavior, real boundary conditions, etc., come up to surface leading to a deeper understanding of the structural behavior of the system itself. Therefore, the present approach can be utilized for further investigations of nonstandard structures undergoing large deformations. [ABSTRACT FROM AUTHOR]

In this paper the influencing factors of the nonlinear behavior of a highly deformable square frame are aimed to highlight and identify. Therefore, in a first step a square frame consisting of four slender members of equal length has been investigated experimentally. Subsequently to these investigations, a numerical model is set up with a beam finite element model, which is based on the absolute nodal coordinate formulation (ANCF), including geometrical and possible material nonlinearities. The influencing factors as well as the system properties are identified by using a genetic optimization algorithm. The final results show that the highly nonlinear behavior of the square frame can be reproduced accurately in case the nonlinear characteristics of the joints are taken into account carefully. The numerical model combined with the system parameter identification can be utilized for further numerical investigations of non-standard structures undergoing large deformations. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]