ENGINEERING TRANSACTIONS
ROZPRAWY INÆYNIERSKIE
A QUARTERLY JOURNAL
- B.K. Sharma, R.C. Chaudhary:
Hydromagnetic unsteady mixed convection and mass transfer flow past a vertical porous plate immersed in a porous medium with the Hall effect
- G. Cieplok:
The first half-turn of an inertial vibrator
- M. Lechman:
Resistance of RC annular cross-sections with openings subjected to axial force and bending
- £. Figiel, B. Lauke, M. Kamiński:
Sensitivity analysis in a fatigue delamination problem of an elastic two-layer composite
- B.K. Sharma, R.C. Chaudhary:
Hydromagnetic unsteady mixed convection and mass transfer flow past a vertical porous plate immersed in a porous medium with the Hall effect
- The present work is concerned with unsteady mixed convection and mass transfer flow with
Hall effect of an electrically conducting incompressible viscous fluid through a porous medium
bounded by an infinite vertical plate subjected to suction/injection velocity in the presence of a
constant magnetic field. The magnetic field is applied transversely to the direction of the flow.
The resulting problem has been solved analytically and the solutions are found for velocity,
temperature, concentration of the species, skin-friction, surface heat flux and mass flux. The
effects of material parameters on the flow characteristics are expressed and illustrated/discussed
by graphs and table.
Contents
- G. Cieplok:
The first half-turn of an inertial vibrator
- The paper concerns the starting of an inertial vibrator which, due to a high value of
static unbalance, is unable to perform the first half-turn in the gravitational field of force.
The problem plays an essential role in the selection of driving units for the wide class of
over-resonance machines.
- On the basis of the Pontryagin's Maximum Principle the problem was formulated in terms
of a dynamic optimisation. Thus, the driving moment performs the function of control - which
is being looked for - while equations of motion and start-end conditions related to the position
of a vibrator, act as constrains equations and boundary conditions. The possible simplifications
in description of the motion of the vibrator, as well as the influence of the variable asynchronous
motor driving moment on the optimal solutions, are discussed in the paper. On the basis of the
work-energy equivalence principle, the minimum values of the driving moment - which warrants
the performance of the first half-turn of the vibrator at a given number of the moment switchovers
- were determined. The problem of thermal loads of the motor during the first half-turn
was also considered. The theoretical results were confirmed by the computer simulations.
Contents
- M. Lechman:
Resistance of RC annular cross-sections with openings subjected to axial force and bending
- This paper presents ultimate limit state analysis of the resistance of reinforced concrete
(RC) annular cross-sections with openings, subjected to the axial force and the bending moment.
Based on nonlinear material laws for concrete and reinforcing steel and using the method
of mathematical induction, analytical formulae are derived in the case when the cross-section
is weakened by an arbitrary number of openings located symmetrically with respect to the
bending direction. In this approach, the additional reinforcement at openings is also taken
into account. The results of numerical calculations are presented in the form of interaction
diagrams with the design values of the normalized cross-sectional forces nu and mu for the
sections weakened by openings as well as for the closed ones. This approach has been applied
to investigate the influence of different parameters such as the size and the number of openings,
the reinforcement ratio, the additional reinforcement at the opening, the form of stress-strain
relationships for concrete and the thickness/radius ratio, on the section resistance.
Contents
- £. Figiel, B. Lauke, M. Kamiński:
Sensitivity analysis in a fatigue delamination problem of an elastic two-layer composite
- Several parameters can affect the fatigue delamination growth in laminates - these include
e.g. constituent material properties and/or composite shape. Knowledge about effects
of these parameters can lead to a better understanding of the fatigue delamination behaviour
and can also pinpoint directions for optimum composite design. These effects can be elucidated
by carrying out an appropriate sensitivity analysis. A FEM-based computational approach to
sensitivity analysis is proposed in this work to study composite parameter effects in a fatigue
delamination problem of an elastic two-layer composite. It is used to calculate and analyse sensitivity
gradients of the fracture parameter and fatigue cycle number with respect to composite
design parameters such as layer elastic constants. It is observed that sensitivities computed
from this approach are generally numerically stable. Obtained sensitivities pinpoint quantitatively
the most and least important composite parameters that govern a fatigue delamination
process. Sensitivity results are verified by another computational approach and a very good
agreement is found.
Contents
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