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ROZPRAWY INŻYNIERSKIE

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Abstracts of papers for

Previous issue vol. 48, no. 4 (2000)

vol. 49, no. 1 (2001)

Next issue vol. 49, no. 2-3 (2001)

Contents of issue 1, vol. 49

1. M. Lechman and P.M. Lewiński: Generalized section model for analysis of reinforced concrete chimney weakened by openings
2. N. Ait Hocine and M. Nait Abdelaziz: A simple single specimen method for measuring the fracture surface energy of rubber materials
3. A. Grzyb and M. Kowalski: Optimisation of five-link suspension mechanism of a vehicle solid tyres
4. J. Jędrysiak: A contribution to the modelling of dynamic problems for periodic plates
5. J. Miastkowski and R.Szczebiot: Yield surfaces and criteria of plastic yielding for a strain hardening material. Part 1: Experimental study
6. J. Miastkowski and R.Szczebiot: Yield surfaces and criteria of plastic yielding for a strain hardening material. Part 2: Theoretical analysis

M. Lechman and P.M. Lewiński: Generalized section model for analysis of reinforced concrete chimney weakened by openings

In the paper, the general equilibrium equation due to bending moment and normal force is formulated for RC cross-section weakened by an arbitrary number of openings. The governing equations for the normal stresses due to bending moment and normal force are derived for the case when openings are located symmetrically as well as asymmetrically to the bending direction. The normal tensile stresses in concrete are neglected, and the reinforcing steel is continuously spaced at l layers (lÎN). The constitutive equations for steel are assumed to be linear elastic, while the concrete is described as an elastic material in compression and brittle in tension. Furthermore, the strains are assumed to be small and their distribution across the section to be linear. The additional reinforcement located in the zone of the flue openings is involved. Basing on the equilibrium equation about the neutral axis, the effective moment of inertia of the cracked annular cross-section with openings is derived, and its influence on the fundamental frequency of the chimney is evaluated. The effects of different parameters on stresses in concrete and steel in the considered annular cross-sectiong are presented and discussed.

Contents

N. Ait Hocine and M. Nait Abdelaziz: A simple single specimen method for measuring the fracture surface energy of rubber materials

In this investigation, particular attention is paid to the generalized theory of fracture mechanics developed by Andrews and based on the spatial strain energy density distribution W in the case of an infinite lamina. A numerical analysis using a finite element method brings out some serious shortcomings in the fundamental equation of this theory when dealing with laboratory specimens of finite dimensions. It is proven that the J integral derived from this equation has no physical meaning. We have proposed an alternative expression of W which leads to a simplified J integral requiring measurements on one specimen only.

Contents

A. Grzyb and M. Kowalski: Optimisation of five-link suspension mechanism of a vehicle solid tyres

The paper presents a method of constructing the optimum kinematic characteristics on the basis of five-link suspension. In order to solve this issue, the perturbation method of analysing nonlinear algebraic equations was used. After assuming the decision variables, defining objective functions and appropriate limitations, a sampling method of optimisation was used. Calculations enabled us to obtain a correction of characteristics of wheel steering and camber angles with initial characteristics. The obtained results indicate that it is possible to apply the above method to form the optimum characteristics of multi-link suspension mechanisms.

Contents

J. Jędrysiak: A contribution to the modelling of dynamic problems for periodic plates

A certain problem of vibrations analysis of thin periodic plates is presented in this paper. The applied model describes the effect of the periodicity cell size on the overall plate behaviour. In the modelling procedure we use a concept of functions which describe oscillations inside the periodicity cell and have to be properly chosen approximations of solutions to eigenvalue problems for natural vibrations of a separated periodicity cell with periodic boundary conditions. In this paper we will show that for certain cases of that cell, an approximate form of those functions can be used.

Contents

J. Miastkowski and R.Szczebiot: Yield surfaces and criteria of plastic yielding for a strain hardening material. Part 1: Experimental study

The paper presents the results of experimental investigations of yield surfaces and plastic yield criteria for an aluminium alloy under complex loading. Experiments were performed on flat specimens (cut out of a sheet of metal) under uniaxial tension or compression. The proposed methodology has allowed to determine simultaneously two characteristic sections of the yield load surfaces. The first of these sections lies in the region of tensile stress while the second one is within the compressive stress area. Then, these two sections have enabled us to describe the position and dimensions of the whole yield surface in the stress space. Tests were carried out at first in the initial state and then in three other states of this material obtained under different plastic prestrains. Such a procedure allowed us to determine the quantitative changes in the yield surfaces dimensions and the position of their centres as a function of plastic prestrains.

Contents

J. Miastkowski and R.Szczebiot: Yield surfaces and criteria of plastic yielding for a strain hardening material. Part 2: Theoretical analysis

The paper presents the experimental verification of the generalized Mróz hardening hypothesis under the conditions of complex state of stress. The analysis performed takes into account the changes in size and position in the stress space of the triaxial ellipsoid illustrating the Huber-Mises-Hencky yield condition for the plane state of stress under definite plastic strains.

Contents

Abstracts for 48, 4, 2000 (previous issue)

Abstracts for 49, 2-3, 2001 (next issue)

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