ENGINEERING TRANSACTIONS
ROZPRAWY INŻYNIERSKIE
A QUARTERLY JOURNAL
- Z. Kotulski, W. Szczepiński:
On a model for prediction of the movements of a crowd in narrow exits
- B. Gambin, A. Gałka, J.J. Telega, S. Tokarzewski:
Influence of anisotropy induced by microcracks on effective elastic properties
- J.M. Fragomeni, R. Wheeler, K.V. Jata:
The effect of aging on the microstructure, precipitation response, and fatigue behavior in an
Al-Li-Cu alloy
- W. Bodaszewski:
Analyses of plane stress discontinuity lines systems in Oyane porous media
- I. Ecsedi:
Bounds for the effective shear modulus
- Z. Kotulski, W. Szczepiński:
On a model for prediction of the movements of a crowd in narrow exits
- In the paper a method of simulation of the movement of a crowd in narrow exits is presented. The
stochastic model applied is based on the concepts proposed by J. Litwiniszyn concerning the analysis
of movements of earth masses caused by underground mining works. The main part of the paper contains
the results of mechanical simulation of the crowd movement in several geometrical configurations of
the exits. The concluding sections of the paper present the diffusion interpretation of the obtained
experimental results and a proposition of further research based on several practical models of
movement of granular material.
Contents
- B. Gambin, A. Gałka, J.J. Telega, S. Tokarzewski:
Influence of anisotropy induced by microcracks on effective elastic properties
- The influence of microcracks distribution on macroscopic elastic properties of composites with
a specific structure is studied. The model predicts the properties of laminates made of materials
in which fracture process leads to appearance of many microcracks distributed practically uniformly.
The method of solution is based on the so-called reiterated homogenization with two different scales
of inhomogeneities. The smaller scale is connected with microcracks size. After homogenization performed
with the help of FEM an anisotropic homogeneous elastic material is obtained. The anisotropy is implied
by directional distribution of microcracks. On the second larger scale, random mixture of two or more
different anisotropic elastic materials is considered.
Contents
- J.M. Fragomeni, R. Wheeler, K.V. Jata:
The effect of aging on the microstructure, precipitation response, and fatigue behavior in an
Al-Li-Cu alloy
- The interrelationships between precipitate characteristics and mechanical properties of an Al-Li-Cu
alloy was quantified. The microstructure, precipitation response, and fatigue crack growth rates in the
Al-Li-Cu alloy AF/C458 were studied following single and duplex aging treatments for varying aging times
on specimens that were given a six percent stretch after solution heat treatment. Aging response was
studied using hardness and compression yield strength measurements. Quantitative transmission electron
microscopy methods were used to characterize average size, volume fraction, number density, and interparticle
spacing of strengthening precipitates, δ' (Al3Li) and T1 (Al2CuLi).
Strength and fatigue crack growth rates for select heat treatments were obtained and were related to the
precipitate microstructure and yield strength data.
Contents
- W. Bodaszewski:
Analyses of plane stress discontinuity lines systems in Oyane porous media
- The paper presents the results of numerical analyses of certain properties of plane stress
discontinuity lines systems, which are specific for the Oyane condition, and do not appear when
one assumes other yield conditions, such as Huber-Mises or Tresca conditions.
- The results have been obtained by applying general algorithms that do not require formulating
any individual relationships. The algorithms aid solving problems for any boundary conditions, of
practically any type, which can be met in the problems of construction of discontinuous statically
admissible fields, mainly the limit fields. In the assumed formulation, the solution consists in
finding initially the fields arising around isolated nodes of stress discontinuity lines, and then
integrating the fields into two-dimensional complex fields.
- Application of these algorithms makes it possible to quickly find all the existing solutions of
the stress discontinuity lines around the nodes, at the same time eliminating the need of forecasting
(guessing the solution), which until recently was the main difficulty in solving each new complex field.
- Physical justification of the Oyane condition is beyond the scope of this work.
Contents
- I. Ecsedi:
Bounds for the effective shear modulus
- This paper deals with the uniform torsion of nonhomogeneus elastic beams. The concept of the effective
shear modulus is deduced from torsional rigidity. Upper and lower bounds are derived for the effective shear
modulus. It is proven that the effective shear modulus of a~compound beam is between the weighted arithmetic
and harmonic means of shear moduli of the beam components.
Contents
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