ENGINEERING TRANSACTIONS
ROZPRAWY INŻYNIERSKIE
A QUARTERLY JOURNAL
- P. Ranachowski, F. Rejmund, J. Fleszyński:
Acoustic method of on-site examination of ceramic long-rod insulators
- A. Kapelko:
The quality of high-performance concretes as a function of their hardening time
- W. Bodaszewski:
Algorithms of the method of statically admissible discontinuous stress fields (SADSF)
Part 1. Idea of the SADSF method, basic conditions and application version
- Z.H. Żurek:
Comparison of selected methods of stress measurements in ferromagnetic materials
- V. Pauk, M. Woźniak:
Rolling contact of long elastic cylinders with surface roughness described
by a two parameter model
- P. Ranachowski, F. Rejmund, J. Fleszyński:
Acoustic method of on-site examination of ceramic long-rod insulators
- This paper presents the new nondestructive ultrasonic method for
investigation of long-rod insulators working as the element of
station isolating switches. The 110/6kV stations belonged to
domestic industrial power engineering. The main aim of the
research was to establish a close correlation between the degree
of defectiveness of electrotechnical porcelain and parameters of
ultrasonic wave propagation and attenuation. In addition, the
causes of breakage of insulator SWZPAK-110 from the year 1975 were
ascertained. This ceramic element underwent detailed structural
and comparative acoustic measurements. The experimental
investigations were performed using a specially designed and
constructed measuring equipment. Besides founding the original
technological and also direct causes of breakage of the insulator
mentioned above, the most significant achievement of the work was
elaboration of the methodology of ultrasonic measurements applied
directly to objects in exploitation. The presented method was used
for the analysis of quality of the group of 43 insulators after
long-term exploitation on isolating switches.
Contents
- A. Kapelko:
The quality of high-performance concretes as a function of their hardening
time
- In the paper, the results of the author's investigations on the
long-term variation of some technological properties of cement
concrete are presented. The experiments were carried out using
basalt aggregate, natural sand, Portland cement CEM I 42.5 R,
acrylic superplasticizer and silica fume. By adding
superplasticizer, the amount of water in the concrete mix was
reduced by 19-22% whereby the water-binder ratio was reduced
from 0.40 to 0.29-0.32. All the tested concretes meet the
compressive strength requirements of the adopted classification of
HPCs (compressive strength of at least 60 MPa after 28 days of
hardening). Long-term testing has confirmed that compressive
strength as a function of time is steadily increasing. The
increase is rapid in the first days of hardening. Logarithmic
curves are a good approximation of the relationship between
compressive strength and hardening time. The investigations have
demonstrated that superplasticizer and silica fume significantly
reduce the water absorption of the concrete. Also increasing in
time is the modulus of elasticity. The concrete modified with
superplasticizer and silica fume seems to be more brittle than the
reference concrete.
Contents
- W. Bodaszewski:
Algorithms of the method of statically admissible discontinuous stress
fields (SADSF)
Part 1. Idea of the SADSF method, basic conditions and application version
- Summary of the whole paper: By now, the SADSF method is
practically the only tool of shape design of complex machine
elements that provides an effective solution even to the problems
of 3D distribution of the material, and at the same time it is
still enough user friendly to be useful for engineers. This unique
property of the method is due to the existence of its simple,
application version. When using it, a design engineer does not
need to solve by oneself any statically admissible field - which
could be very difficult - but obtains such a solution by
assembling various ready-made particular solutions. The latter are
in general obtained by means of individual and complex analyses
and provided to a designer in a form of libraries.
- The algorithms presented in this paper break up with the
individual approach to a particular field. The algorithms are the
first ones of general character, as they apply to the fundamental
problems of the method. The algorithms aid solving practically any
boundary problem that one encounters in the tasks of construction
of 2D statically admissible, discontinuous stress fields, first of
all the limit fields. In the presented approach, one deals first
with the fields arising around isolated nodes of stress
discontinuity lines (Parts II and III), then integrates these
fields into 2D complex fields (Part IV).
- The software, created on the basis of the algorithms, among other
things, allows one to quickly find all the existing solutions of
the discontinuity line systems and present them in a graphical
form. It gives the possibility of analysing, updating and
correcting these systems. In this way, it overcomes the greatest
difficulty of the SADSF method following from the fact that the
systems of discontinuity lines are not known a priori, and
appropriate relationships are not known either, so that they could
only be found in an arduous way by postulating the line systems,
and verifying them.
- Application version of the SADSF method is not described in this
paper; however, a reference is given to inform the reader where it
can be found.
- Summary of Part I: As a form of introduction, the author presents
in a broad outline the general concept of the SADSF method, its
fundamentals, basic conditions, typical formulation of boundary
problems and the essence of difficulties in problem solving. These
are not only nonlinearities, singularities, and conditions
expressed by complex functions (i.e. given in a form of
algorithms), but first of all the structure of the condition
system - that is not a priori known - which cause
difficulties. As it turns out, the structure depends on boundary
conditions, but the relations that express this dependence are not
known. In the physical space, it refers to the problems with
unknown discretization that is dependent on boundary conditions.
- Also, as a form of introduction, it will be shown that the
investigation of mentioned dependence is possible, anyway.
However, it is possible not for two-dimensional fields as a
whole, but at least for their component fields around nodes.
Thereby fundamental ideas of algorithms are presented in broad
outline. Such algorithms are discussed in detail in Parts II and III.
- The application version of this method, attractive for practical
purposes, is briefly described in this part. Numerical examples,
also included here, illustrate the position and the possibilities
of the method in solving practical problems of shape design of
complex thin-wall structures.
Contents
- Z.H. Żurek:
Comparison of selected methods of stress measurements in ferromagnetic
materials
- Change in magnetisation of a ferromagnetic subjected to mechanical
stress is known as Vilarie's effect. The paper describes
contactless measurement of stress based on this effect. The
measurement signals generated by magnetoresistive transducer were
compared to measurements of deformation conducted with strain
gauge transducer at the same time. Qualitative and quantitative
similarities have been observed in the recorded signals. The
simplicity of the contactless stress and vibration measurement
with magnetoresistive transducer has been demonstrated. This
method makes possible measurements even if the material is
characterised by low magnetostriction coefficient.
Contents
- V. Pauk, M. Woźniak:
Rolling contact of long elastic cylinders with surface roughness described by
a two parameter model
- Rolling contact problem for rough cylinders is considered. A new
model of the surface roughness is proposed. The problem is reduced
to the system of singular integral equations which is solved
numerically.
Contents
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