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Showing 2 results for Pre-Stress
, , , , ,
Volume 13, Issue 2 (5-2013)
Abstract
Terfenol-D, known as a giant magnetostrictive material, is used in many sensors such as force sensor. In these sensors, external force is measured due to variation of magnetic flux density passing through Terfenol-D. To improve the performance, Terfenol-D is exposed to bias magnetic field and mechanical pre-stress. In this paper, Effects of bias magnetic field and mechanical pre-stress on sensitivity and linear measurement range of a force sensor are studied and optimum values of them are recognized. Initially based on magnetomechanical coupling equations, theoretical model of sensor that includes effective parameters on sensitivity and linear measurement range is developed. Then using experimental set-up, magnetomechanical properties of Terfenol-D are investigated and values of essential parameters for theoretical model are extracted. Finally, employing theoretical model and experimental results, the response of sensor under dynamic external forces is simulated and effects of bias magnetic field and mechanical pre-stress on sensitivity and linear measurement range of the sensor are studied. Based on the obtained results, to increase sensitivity and linear measurement range of sensor, values of bias magnetic field and mechanical pre-stress should be relatively determined considering the amplitude of external force.
Shirko Faroghi, Mahdi Bamdad,
Volume 14, Issue 14 (3-2015)
Abstract
In this paper, a new formulation is developed for nonlinear dynamic analysis of 2-D truss structures. This formulation is based on dynamics of co-rotational 2-D truss. The idea of co-rotational approach is to separate rigid body motions from pure deformations at the local element level. Using this approach, internal force vector and tangent stiffness matrix, inertia force vector and the tangent dynamic matrix are derived. Furthermore, the inertia force vector, tangent dynamic matrix, mass matrix and gyroscopic matrix are directly derived from the derivation of current orientation matrix with respect to global displacements or orientation matrixes. Using this new formulation, nonlinear response of any 2-D truss structures can be examined. Here, for example the response of tensegrity structures under dynamic loads are investigated. Tensegrity structures are a class of structural system composed of cable (in tension) and strut (in compression) components with reticulated connections, and assembled in a self-balanced fashion. These structures have nonlinear behaviour due to pre-stress forces. And their integrity is based on a balance between compression and tension. Two numerical examples are presented to illustrate the new formulation and results show that the new formulation has more convergence rate than the existing models.