ENGINEERING TRANSACTIONS
ROZPRAWY INŻYNIERSKIE
A QUARTERLY JOURNAL
- A. Pielorz:
The investigation of the influence of a local elastic nonlinearity on vibrations of plane truss members
- J. Madej:
Influence of damage on variations of material thermal properties
- M. Królak, K. Kowal-Michalska, J. Świniarski:
Optimisation regarding local stability and strength of long multilayered plates subjected to compression
- W. Dornowski:
Numerical simulation of finite deformations of a dynamically loaded elasto-viscoplastic circular membrane
- U. Andreaus, P. Casini, and F. Vestroni:
Frequency reduction in elastic beams due to a stable crack: numerical results compared with measured test data
- A. Pielorz:
The investigation of the influence of a local elastic nonlinearity on vibrations of plane truss members
- The paper concerns theoretical investigations of plane
trusses subject to longitudinal deformations, using nonlinear
discrete-continuous models. An external excitation is applied to a
rigid body located in a truss joint. In this joint a visco-elastic
discrete element with a spring having a nonlinear symmetric
stiffness is also located. It is assumed that the spring
characteristic is of a soft type. Four nonlinear functions
describing this characteristic are proposed. In the considerations
the wave method is applied similarly to the case of a hard
characteristic in [1]. The numerical analysis focus on the
investigation of the effect of the local nonlinearity with a soft
characteristic for two examples of plane trusses.
Contents
- J. Madej:
Influence of damage on variations of material thermal properties
- The aim of this paper is presentation of an attempt of
identification of the changes of thermal properties of the
material in correlation with changes of its structure during the
damage process. The review of the most frequently used methods of
damage detection in constructional materials has been enclosed. In
comparison to these approaches, a new method is presented - namely
the method of assessment of the level/stage of damage based upon
changes/fluctuations of heat transmission property of the
material, which occur in the damage cumulation regions. In the
considerations, the continuum mechanics of damage was assumed. The
assumption is supported by numerical calculations, which are in
full agreement with experimental investigations made by means of
thermo-vision techniques. Experiments performed and suitable
numerical simulation confirms the essential connection between the
state of damage and thermal transmission properties of the
investigated materials.
Contents
- M. Królak, K. Kowal-Michalska, J. Świniarski:
Optimisation regarding local stability and strength of long multilayered plates subjected to compression
- In this paper the method of optimal selection of
orthotropic layers thickness is presented. The considerations
concern long rectangular plates subjected to uniform compression
in the direction of longer edges. Such plates (or cylindrical
panels) of increased local buckling resistance could be applied as
components of thin-walled columns of closed
cross-sections.
Contents
- W. Dornowski:
Numerical simulation of finite deformations of a dynamically loaded elasto-viscoplastic circular membrane
- The present paper deals with theoretical modeling and
numerical simulation of a thin circular plate subjected to
impulsive loading. To this end, the convective description is
applied. The kinematical hypothesis used for theoretical
description of the transient response includes membrane
deformations only. This assumption is valid in the range of large
deformations. The dynamical response of the material is described
by Perzyna's elasto-viscoplastic constitutive relations. The
theory is completed by an algorithm of the explicit finite
difference method. With respect to the conditional stability of
that method, the stability criterion is given. Basing on
experimental data, an identification of material parameters is
carried out. Some comparisons with the corresponding theoretical
and experimental results are presented. Satisfactory agreement of
the results has been found. Finally, an example of the plastic
strain localization in a membrane is presented.
Contents
- U. Andreaus, P. Casini, and F. Vestroni:
Frequency reduction in elastic beams due to a stable crack: numerical results compared with measured test data
- The presence of a crack could not only cause a local
variation in the stiffness, but it could affect the mechanical
behaviour of the entire structure to a considerable extent. The
frequencies of natural vibrations, amplitudes of forced vibrations
and areas of dynamic stability change due to the existence of such
cracks. The vibration characteristics of cracked structures can be
useful for non-destructive testing. In particular, the natural
frequencies and mode shapes of cracked beams can provide insight
into the extent of damage. The beam has been schematized as a 2-D
continuous medium and discretized by means of quadrilateral finite
elements. The lowest three natural frequencies (and the associated
mode shapes) of the cracked cantilever beam, were obtained via
both the modal and spectral analyses, and were compared with
experimental data from literature in order to assess the
reliability of different models of crack state, namely open crack
and contact crack. Both the experimental and numerical results
reveal the significant influence of the opening and closing
conditions of the crack on the frequency reduction; namely this
reduction decreases as more realistic contact phenomena are
considered at crack interfaces.
Contents
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