ENGINEERING TRANSACTIONS
ROZPRAWY INŻYNIERSKIE
A QUARTERLY JOURNAL
- N.M. Auciello:
Vibrations of Timoshenko beams on two-parameter elastic soil
- D. Jasińska, M. Janus-Michalska:
Material design of anisotropic elastic cellular bodies with respect to contact problem
- G. Socha:
Changes of the yield condition due to accumulation of damage of metal alloys
- J. Konieczny:
Modelling of the electrohydraulic full active vehicle suspension
- W. Burzyński:
Theoretical foundations of the hypotheses of material effort
- N.M. Auciello:
Vibrations of Timoshenko beams on two-parameter elastic soil
- In this paper the influence of the two-parameter elastic soil on the dynamic behaviour of
a beam with variable cross-section is examined, in the presence of conservative axial loads. The
beams are assumed to follow the well-known Timoshenko hypotheses, in order to take into account both the rotary inertia and shear deformation effect. The Rayleigh-Ritz approach is used
and Boundary Characteristic Orthogonal Polynomials are chosen as trial functions; (BCOPs
method [2]). The theory is concisely presented in a matrix form, so that the contribution of
the rotary inertia and of the soil can be easily recognized. Various examples and comparisons
are illustrated, in order to emphasize the influence of the soil properties and of the beam taper
ratio. Finally, the results are also compared with the results given by other authors, using exact
and approximate approaches.
Contents
- D. Jasińska, M. Janus-Michalska:
Material design of anisotropic elastic cellular bodies with respect to contact problem
- Two-dimensional contact problem formulated for anisotropic, elastic bodies is considered.
As an example of anisotropic medium, the cellular material is taken. The idea of two-scale
modeling is adopted for formulation of an equivalent continuum, on the basis of which elastic
properties can be obtained [2, 3]. Typical cellular microstructures with various types of symmetries are considered. Special attention is paid to cell structures giving negative Poisson's ratio
in some directions (re-entrant cells). Application of the energy-based criterion for equivalent
continuum gives macroscopic yield condition [2, 5]. Condition for the energy coefficient defined
as a sum of weighted energies stored in elastic eigenstates ensures that the material works in
elastic state. Unilateral frictional contact problem is analyzed using FEM. Calculations are
performed for rough contact of square block subjected to normal load. Numerical solutions
show differences in deformation type and contact stress distributions for different types of
microstructures of the analyzed medium. The study enables the optimal choice of material
structure topology, which ensures the reduction of peak contact pressure and friction stress,
and applicability of anisotropic material to the given problem.
Contents
- G. Socha:
Changes of the yield condition due to accumulation of damage of metal alloys
- The results of the experimental investigations of fatigue damage accumulation and redistribution of residual stresses are reported in this paper. Local measurements of the inelastic
response under constant stress amplitude were used to observe two phenomena for selected
alloys. It was found that fatigue damage accumulation and redistribution of residual stress affect the yield condition for the investigated materials. Yield condition with damage parameter
and the parameter representing residual stress state are proposed. The damage parameter is
calculated, basing on the definition given in the author's previous paper. It was also found that
the yield condition and damage parameters are different for dynamic (cyclic loading) and for
static (for unloaded material) conditions. Physical interpretation for the observed experimental results is given in this paper. Fatigue damage accumulation is divided into three phases:
cyclic stabilisation, local increase of crystal defects density, formation and propagation of the
crack. Local methods of strain measurements, together with dynamic measurements of damage
parameter, were found to be crucial for proper observation of fatigue damage accumulation.
Contents
- J. Konieczny:
Modelling of the electrohydraulic full active vehicle suspension
- The study investigates various models of vehicle suspensions. A quarter-vehicle full active
suspension is chosen for further analysis. A mathematical model, governed by nonlinear differential equations, is proposed that takes into account dynamic properties of an electrohydraulic
actuator. The mathematical model being implemented, it was expressed in terms of the state
variables. In part two, the physical model was implemented and parametric identification procedure was applied. Phenomenological model simulation data are compared with results of
experimental testing of a full, active vehicle suspension. The final section is focused on static
and dynamic properties of an open-loop system (without a controller) determined on the basis
of obtained models.
Contents
- W. Burzyński:
Theoretical foundations of the hypotheses of material effort
- Translated from the original paper in Polish: ''Teoretyczne podstawy hipotez wytężenia'' by Anna Stręk;
scientific editor Ryszard B. Pęcherski
Contents
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