Papers by Author: Grzegorz Slawinski

Abstract: In the paper the experimental results of the dynamic tests of the MRE samples cured without and under magnetic field are presented and compared. The samples (55 mm diameter and 70 mm) were made of the polyurethane elastomer PU 70/30 with the admixture of the ferromagnetic particles (in this case – carbonyl iron spheres with the diameter of about 9 μm). The samples with ferromagnetic particles were cured without as well as under the external, parallel to the vertical axis of the sample, magnetic field of the 300 mT intensity. The experiments were carried out on the materials testing machine for static and dynamic loads INSTRON 8802. The machine was additionally equipped with the measurement head of 4kN scope and the magnetic coil that produces the magnetic field of the intensity up to 500 mT. Cycled load was applied to the MRE samples. In the case of the dynamic tests the sinusoid cyclic variable load was used. The applied load frequency was 1 Hz in each presented test. The samples were cyclically compressed of the 10, 15, 20 and 25 % of their height. On the base of the obtained results the force maximum values and the dumping coefficient (the energy dissipation coefficient) in each dynamic tests were calculated. The hysteresis loops in the load – displacement charts that were observed during the cyclic tests. The influence of the internal structure of the researched material on its strength behaviour is taken into consideration.

Abstract: Magnetorheological elastomers (MREs) are a class of so called “smart materials” which rheological and mechanical properties can be reversibly and rapidly controlled by an external magnetic field. MREs have attracted increasing attention and obtained broad application prospects recently. They can be used in valves, dumpers, brakes or sensors constructions. In the paper, the numerical models of a magnetorheological elastomers microstructure are presented. The influence of the applied magnetic field during the curing process of elastomer is taken into consideration in each model. The developed structures are built of the hyper elastic material which surrounds the iron particles. The models are first loaded with the external compression force and then with the internal forces simulating the influence of the applied magnetic field. The results of the numerical analyses are shown as the displacement, stress and strain distributions in each model. The influence of the MRE microstructure on the strength behavior of the researched material is strictly visible as the non-homogeneity in the described distributions.

Abstract: The paper deals with the numerical analysis of a tensile loaded riveted joint. Finite element simulations of the upsetting process were carried out with the use of Marc code to determine the residual stress field. The contact with friction is defined between the mating parts of the joint. The computations were performed for four cases of material and load conditions and a comparison was performed on the basis of results obtained for standard elasto plastic and Gurson material models. Moreover, the influence of material model and residual stress on the tensile loaded joint was analyzed.

Abstract: The paper deals with analysis of contact stress fields and relative displacements as well as inspection of fretting phenomena in the neighborhood of mating surfaces of the riveted joint subjected to cyclic loading. The study of micro-local phenomena follows the riveting process analysis. Numerical FE simulations of the upsetting process are carried out to determine the residual stress and strain fields. Nondestructive testing methods are used for validation of numerical results. The contact with friction is defined between the mating parts of the joint. The influence of the initial load and sheet material model is studied. Maximum values of relative displacements are comparatively small but surface condition is strongly affected by sliding movements during cyclic loading. Plastic strain energy is taken into account for more efficient numerical analysis of the fretting wear.