S., SLÁDEK, J., SLÁDEK, V., STAŇÁK,
analysis in functionally
graded magnetoelectroelastic solids 239
J., CHMÚRNY, R.: Comparison
of phenomenological methods for dry-friction
simulation of an oscillatory system under random excitation 261
L., PEŠEK, L., CIBULKA, J., BULA, V.:
Temperature processes at two sliding
surfaces subjected to dry friction 277
HAFIZ HARUN, M., HUDHA, K., AHMAD, F., HANIF HARUN, M., ZAMORDIN, A. Z.:
Modelling and validation of magnetorheological damper for lateral
suspension of railway vehicle
using interpolated sixth order polynomial 293
M., ESMAEILNEJAD, M., GHASEMI,
thin-walled tube subjected to
combined internal pressure and axial load under different loading paths 307
Crack analysis in functionally graded magnetoelectroelastic solids
S. KRAHULEC, J. SLÁDEK, V. SLÁDEK, P. STAŇÁK
The paper discusses the crack analysis with a central crack in a magnetoelectroelastic solid. A 2D crack problem is considered. The finite element method is applied to solve static problem of a functionally graded magnetoelectroelastic strip. Material properties are continuously varied along the crack from the centre of the strip to the lateral side. Various electromagnetic boundary conditions are applied on the crack faces. The specification of the electromagnetic boundary conditions on the crack faces plays an important role in the crack analysis of magnetoelectroelastic materials. Two extreme cases are analysed: fully permeable and fully impermeable crack surfaces. Various gradations of the material properties and various electromagnetic boundary conditions are considered to investigate their influence on crack opening displacements, electric and magnetic potentials and intensity factors.
Comparison of phenomenological methods for dry-friction simulation of an oscillatory system under random excitation
J. STEIN, R. CHMÚRNY
The paper deals with phenomenological description of dry-friction influence in single degree of freedom oscillatory systems excited with low intensity random excitation. Three different simulation methods are described on the basis of the analytical Den Hartog’s approach. Two simulation methods: the signum approach and the continuous signum approach are a benchmark against the physically correct stick-slip approach. It is shown that under certain circumstances the standard signum approach furnishes false results. Criteria are developed that enable to determine, whether the standard signum approach suffices, or it is necessary to use the continuous signum approximation, or revert to the physically correct stick-slip approach. The stick-slip approach rigorously tests the stick to slip and vice versa transient conditions on the dry-friction interface.
Temperature processes at two sliding surfaces subjected to dry friction
L. PŮST, L. PEŠEK, J. CIBULKA, V. BULA
Application of dry friction damping contact is very often used for damping of turbine blades vibration. This problem is intensively studied in our Institute for several years, but the deficiency of knowledge of special material’s friction characteristics introduces serious uncertainty into the results of research, particularly for the friction connection with periodic relative motion. Therefore, laboratory experimental equipment has been designed and realized. Results of the first set of measurement are presented and discussed. Friction of double steel blade material and overlay of tungsten carbide was investigated for various thrust forces and frequencies of relative motion at the simultaneous measurement of temperatures in three points near the friction surface. An increase of temperature after 25 s of friction run, friction coefficient, friction force, dissipated energy in one cycle during 1 s, entire energy during the friction run, lost power, and energy for 1 oC temperature increase in various conditions were ascertained.
Modelling and validation of magnetorheological damper for lateral suspension of railway vehicle using interpolated sixth order polynomial
M. HAFIZ HARUN, K. HUDHA, F. AHMAD, M. HANIF HARUN, A. Z. ZAMORDIN
Railway vehicle ride comfort is affected by the vibration due to track irregularities. It will be critical when the track is exposed to prolonged sun’s heat. This means that the optimization of passive suspension parameters alone cannot cope with the cases. Semi-active suspension system for railway vehicles has been developed as a way to solve this problem. The use of semi-active suspension is wide spread, especially in the railway vehicle technology. Magnetorheological (MR) damper is one of the applications of the concept of semi-active suspension. However, there are a variety of criteria for MR dampers based on usage. To meet the requirements of railway vehicle suspension system, a MR damper has been developed. Criteria for the MR damper are obtained by experiment. Then, the model for the MR damper is developed using Interpolated Sixth Order Polynomial and validated by experiment. MR damper model has shown improvement, especially in the railway vehicle dynamics performance.
A thin-walled tube subjected to combined internal pressure and axial load under different loading paths
M. SHAHABI, M. ESMAEILNEJAD, A. GHASEMI
Plastic deformation is associated with energy dissipation. So it is irreversible. Due to this irreversibility, one of important features of the plastic deformation process is its history or path-dependence. This feature is one of the principles of the plastic deformation and affects constitutive equations for simulating material behavior under plastic deformation. According to this, because of an importance of this concept, the validity of this vital feature is illustrated in the paper by considering three different loading paths for a thin-walled tube to be more perceptible and more tangible. The stresses and strains in the tube are investigated for these loading paths separately. The results confirm the validity of this concept.