In the paper it is presented a new Euler - Bernoulli theory based on an assymetrical distribution of strains towards the median plane, the area subjected to compression has a transversal stretching, while the area subjected to tensile has a transversal contraction. This theory takes into account the transversal contraction factors and consequently the eigenpulsations of bars vibrations with rectangular section depend on the ratio between the bars width and thickness. This theory is experimentally verified for Dammar based composite bars reinforced with cotton, flax, silk and hemp fibers. For the considered bars, we have experimentally determined the eigen frequencies and the damping factor values.

The paper studies the behavior of a quarter-car suspension model under periodic road excitation: sinusoidal and bump (trapezoidal shape) for a constant vehicle speed. A theoretical and a finite element model were developed. The theoretical model has two degrees of freedom and a modal and sinusoidal excitation was performed to compare with finite model analysis. The finite element analysis consists of three parts: preload, modal analysis and deterministic external excitation. The study consists of the analysis of forces, displacements and accelerations that are transmitted to the vehicle regarding their variation in time and frequency.

The paper presents a method for studying mechanisms with deformable elements, based on overlapping the solid rigid motion over the elastic solid one, in order to identify the dynamic response of the system. Modeling was based on finite element method, so the cinematic elements were meshed in bar type finite elements and the degrees of freedom per node were settled according to the motion character (planar or spatial). A Lagrange formulation of the finite element was adopted for the deformable elements connected in multibody systems. In order to define the joints constraints, the conditions for compatibility between elements were defined using a Boolean constant matrix. Computer processed results were verified by an experimental model.

No abstract

In this paper we present a new design variant for an electric powered wheelchair for the persons with locomotor disabilities. The design novelty consist that we use two kinematic chains, one is for the straight line motion, and one for turning. Each kinematic chain is actuated by an electric motor. The turning kinematic chain has in his structure diferential power transmissions.