ENGINEERING TRANSACTIONS
ROZPRAWY INŻYNIERSKIE
A QUARTERLY JOURNAL
- K. Kędzior:
Professor Jan Oderfeld
- M. Massenzio, S. Pashah, E. Jacquelin, A. Bennani:
Rigid body assembly impact models for adiabatic cutoff equipments
- Z. Nowak:
Constitutive modelling and parameter identification for rubber-like materials
- S.K. Kourkoulis, E. Ganniari-Papageorgiou:
Bending of fragmented architraves restored with bolted titanium bars: A numerical analysis
- K. Kędzior:
Professor Jan Oderfeld
- The Laudatio speech delivered during the ceremony
of awarding Prof. Jan Oderfdeld an honorary doctorate
by Warsaw University of Technology
and on the occasion of his 100th birthday
Contents
- M. Massenzio, S. Pashah, E. Jacquelin, A. Bennani:
Rigid body assembly impact models for adiabatic cutoff equipments
- This paper is concerned with systems consisting of components colliding with each other.
In particular, a high velocity adiabatic impact cutoff machine is investigated. For general
understanding of the impact dynamics (affected by a large number of parameters), the mechanisms
are modelled in a simplified and accurate manner. Two simple models are developed:
the energy-balance model and the spring-mass model. The energy-balance model is based on
the principle of total energy conservation. It provides only the punch minimum kinetic energy
required for efficient cutting. Concerning the spring-mass model, the different components are
represented by rigid masses and their deformations are modelled by springs (linear or nonlinear
in the case of contact stiffness). The resulting non-linear equations are solved using
the Newmark numerical technique. The impact force, velocity, displacement and acceleration
histories are calculated what makes possible a fine description of the cutoff cycle steps. The
two models are helpful for both the design and tuning of the mechanisms involving impacts
between their components.
Contents
- Z. Nowak:
Constitutive modelling and parameter identification for rubber-like materials
- The aim of the paper is to determine the phenomenological model to characterize the
stress-strain relation and to simulate the behaviour of solid polyurethane (PUR) rubbers used
in civil engineering, as well as to present the process of identification of model parameters for
such materials. For the material studied the strain energy density function was established
and a general constitutive relationship for the second-order tensor of Piola-Kirchhoff stress for
elasticity is determined. Constitutive relationships for engineering stress in terms of the principal
stretches are also specified. The paper presents the method of identification of parameters
for constitutive models of hyperelasticity and hypoelasticity for the accessible experimental
data. The applied identification procedure is based on the feature of two-phase structure of
polyurethane material and is supported by the experimental data from uniaxial quasi-static
tension and compression tests. In the analysis, the material behaviour was considered both
for the case of incompressible deformation and also for the case of slightly compressible, nonlinearly
elastic materials that are homogeneous and isotropic. The change of volume was admitted
too, in range of large deformations in a tension and compression test. The attempt of
description of stress-softening phenomenon was undertaken in rubber-like materials, for a given
level of strain, under unloading (the Mullins effect) caused by the damage of microstructure
of this material. Different descriptions of the stress-softening phenomenon were already proposed
in the literature but they fail to give fully satisfactory conformity of experimental data
with theoretical predictions. The phenomenological model by Elias-Zúñiga and Beatty,
A new phenomenological model for stress-softening in elastomers, ZAMP, 53, 794-814, 2002,
for such materials was modified by different softening functions and a simplified version of this
model was identified, based on the experimental data. In the proposed model, the damage of
microstructure was described by a new exponential function, which depends on the current
magnitude of intensity of strain and its earlier maximum value during the process of material
loading. In this paper, a suitable analysis of existent models and their verification based on
experimental data for polyurethane rubber is presented for uniaxial experiments. It is shown
that the magnitude of stress-softening varies with strain and this phenomenon increases with
the magnitude of the pre-strain and the type of loading: monotonic tension, compression or
cyclic loading. The obtained results are presented graphically for uniaxial tension and compression.
Contents
- S.K. Kourkoulis, E. Ganniari-Papageorgiou:
Bending of fragmented architraves restored with bolted titanium bars: A numerical analysis
- The mechanical behaviour of restored structural members of ancient monuments is studied
in the present paper with the aid of the Finite Element Method. The study is motivated by
the needs of the conservation project in progress on the Parthenon Temple of the Acropolis of
Athens; the results however could be valuable for various stone monuments under conservation.
Centrally fractured prismatic marble architraves (epistyles) of rectangular cross-section
restored with either threaded or smooth titanium bars are modelled. The architraves are resting
on marble blocks simulating the capitals (abacuses) of the columns of the temple. They
are subjected to bending under uniformly distributed loading along their span, following the
results of earlier studies, concerning the influence of the loading mode on the overall behaviour
of restored structural members. The method used for determination of the reinforcement
required is the one introduced recently by the scientists working for the restoration of the
Acropolis monuments. All the loads that could be applied on the member after it is replaced
in its initial position in the monument were taken into account, including the own weight of
the member, the weights of the members that will rest on it after the restoration, as well as
possible dynamic (earthquake) loads. Emphasis is laid on the influence of the threads of the
bolted bars in comparison to the results for the unbolted ones, in an effort to quantify the
maximum anchoring length required in order to minimize the intervention on the authentic
stones. The distribution of the stress and strain fields all over the architrave-abacus-reinforcing
bar system is investigated and conclusions are drawn concerning the extreme stresses and the
points where they are developed.
Contents
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