Jacek Snamina

Modeling of an Adaptive Beam with MR Fluid

This paper is devoted to modeling of a three-layered cantilever beam filled with magnetorheological (MR) fluid. The beam consists of two aluminium outer layers and an MR fluid layer placed between them. The study covers description of MR fluid behavior in the pre-yield regime, analysis of strain and internal forces, formulation of differential equations of motion and finite element model (FEM) and numerical calculations. The aim of the study is to determine maximal amplitudes up to which the MR fluid operates in the pre-yield regime.

Dynamic Similarity of Wind Turbine's Tower-Nacelle System and its Scaled Model

A paper presents analysis of dynamic similarity between full-scale wind turbines tower-nacelle system and its laboratory model. As a reference real-world structure, Vensys 82 wind turbine was assumed. Complete and partial similarity criteria were both introduced. Considering laboratory model to be equipped with tuned mass damper horizontally arranged at the top, partial similarity of one pair of points (tower tips) motions will be satisfactory. On the basis of similarity conditions, laboratory model parameters were determined so that data acquired for the model may be referred to real-world structure.

Energy Dissipation in Three-Layered Plate with Magnetorheological Fluid

In the paper a sandwich plate, of rectangular form, with magnetorheological (MR) fluid core is investigated. The plate consists of two outer layers made of aluminium and an MR fluidlayer in between. The plate edges are clamped. It was assumed that the aluminium layers are pure elastic. The energy is dissipated only in the MR fluid layer. Additional assumptions concerning displacements, deformations and stresses are introduced in the calculations. The average power dissipated per unit area of the plate for selected modes of vibrations was determined. A simple method of energy assessment was presented. The results of the calculations can be useful in a semiactive control of continuous systems.

Identification of Complex Shear Modulus of MR Layer Placed in Three-Layer Beam – Part 2: Algorithm

The paper presents the procedure of identification of a complex shear modulus which describes properties of MR fluid in the pre-yield regime as a function of magnetic field. Data necessary for identification were collected basing on measurements of free vibrations of a three-layered cantilever beam at a special laboratory stand. Magnetic field exerting on MR fluid placed in the beam was generated by electromagnet. In the next step, complex modes of beam vibrations for various places of applying the magnetic field and its strength were calculated.

Identification of Complex Shear Modulus of MR Layer Placed in Three-Layer Beam – Part 1: Finite Element

The paper presents the finite element, which can be used to analyse the vibration of a three–layer beam with magnetorheological (MR) fluid layer. The MR fluid layer was sealed with silicone rubber. On the basis of the analysis of displacements, deformations of each layer has been established. Next, potential and kinetic energy of the three–layer beam were calculated. Because of the complexity of the beam with MR fluid, efficient solutions can be obtained only after discretization of the system. The finite element method was used in the study. For this purpose the mass and stiffness matrices were determined for the proposed linear finite element of two nodes and four degrees of freedom in each node.

Active Control Strategy for Reduction of Vibrations in Mast Exposed to Ground Motions

The paper presents an experimental study of active mass damper control strategy based on analysis of energy dissipation. The reduced model of telecommunication mast was built in laboratory. Using the special laboratory setup the verification of the proposed strategy was carried out for free and forced vibrations. Uniaxial and biaxial reduction systems were considered. Experiments confirmed that the proposed algorithm is effective. The best vibrations reduction was obtained using biaxial reduction system.

A Comparison of Active and Semi-Active Sliding Mode Controllers Applied in Vibration Reduction Systems

The paper presents active and semi-active vibration reduction systems applying sliding mode control systems. Calculations were completed for a laboratory system with two masses moving in a vertical direction. Support of the system is connected with the moving part of the exciter. The proposed system may be a simple model of many vibroisolated objects. In order to apply the control system of vibrations in the suspension of the upper mass, an actuator was implemented together with a spring. The role of the actuator was played by a linear inductive motor.Active and semi-active sliding mode controllers are proposed for the vibration reduction system. Theoretical analysis focused on applying of the sliding mode control in this system was carried out and, moreover, conditions to be met by the controllers were determined. The results of simulations and experiments are presented in tables and plots.

Application of Piezoelectric Dynamic Force Sensor for Tool State Assessment in Manufacturing Process

In the paper the problem of examining of a damaged tool in the manufacturing process is presented by the example of the identification of a damaged die for creating a screw drive on a screw head. The operation of the screw head production is known as cold heading. One of the production stage is when a die cuts the head of the screw blank into an appropriate shape. Unfortunately, the die is often damaged before reaching its limit. In this case, the faulty semi-finished products are further processed because the cold heading is only the first operation required to produce a screw. If screws made of high-quality pure stainless steel are considered the economic loss is significant.The measurement automatic systems for identification of damaged dies can be found in the newest machines but they are in minority in comparison to the older ones which work without such systems. It was the reason why attempt was made to construct the prototype diagnostic system for die state assessment, which is presented in the article.Copyright

Analysis of an automotive vehicle engine mount based on a squeeze-mode magnetorheological damper

Analysis of an automotive vehicle engine mount based on a squeeze-mode magnetorheological damper

Wave Packet as a Model of Localised Disturbances Propagating along the Cables

In the paper localised disturbances propagating along the cables are modelled by wave packets. The motion of the cable was described in relation to its equilibrium state. The linear equations were used. Typically disturbances associated with sudden gust of wind are modelled by kinematic generator exciting oscillations in the specified frequency range, concentrated around the central frequency. The packet of binormal waves and coupled packets of normal and tangent waves were considered. The description of the evolution of the wave packets during their motion was presented analytically and numerically in the form of plots.