### Contents of Journal of Mechanical Engineering *52,* 2 (2001)

M.-F. ROBBE, N. VIVIEN, M. VALETTE, E. BERGLAS: Use of thermalhydraulic
and mechanical linked computations to estimate the mechanical
consequences of a steam explosion 65
B. SAMANTA, K. R. AL-BALUSHI, S. A. AL-ARAIMI: Application of wavelets
and artificial neural network in fault diagnosis of rolling
element bearings 91
M. MUSIL: Crack localisation and quantification in a vibrating
structure 103
M. KOMPIS, K. B. NIELSEN: Inverse determination of constitutive
parameters from deep drawing experiment 117

# Abstracts

###
Use of thermalhydraulic and mechanical linked computations to estimate the
mechanical consequences of a steam explosion

M.-F. ROBBE, N. VIVIEN, M. VALETTE, E. BERGLAS

The safety studies of the Pressurised Water Reactors consider severe accidents
such as steam explosions. If the reactor core melts partially and falls into
the water laying below, the heat transfer between the hot corium and the cold
water may be energetic enough to vaporise violently the water and create a
steam explosion. The precision of the evaluation of the explosion mechanical
consequences depends on the premixing phase preceding the explosion and on the
explosion escalation and propagation. This paper presents the method used to
link the thermalhydraulic code MC3D devoted to the steam explosion premixing
phase and the fast dynamics code EUROPLEXUS dealing with the explosion and the
structure response. An application concerning the computation of an in-vessel
steam explosion resulting from a large central core degradation is also
described.

###
Application of wavelets and artificial neural network in fault diagnosis of
rolling element bearings

B. SAMANTA, K. R. AL-BALUSHI, S. A. AL-ARAIMI

A procedure for fault diagnosis of rolling element bearings through wavelet
transforms and artificial neural network (ANN) is presented. The time domain
vibration signals of a rotating machine with normal and defective bearings are
processed through discrete wavelet transform to decompose in terms of
low-frequency and high-frequency components. The extracted features from the
decomposed signals are used as inputs to an ANN based diagnostic approach. The
ANN is trained using backpropagation algorithm with a subset of experimental
data for known machine conditions and tested using the remaining set of data.
The procedure is illustrated through experimental vibration data of a pump.

###
Crack localisation and quantification in a vibrating structure

M. MUSIL

The possibility of localising and quantifying a crack in a vibrating
structure, based on measured vibration amplitudes of the first and second
harmonic in some locations of the structure and utilizing the mathematical
model of an undamaged system, is the focus of this paper. The effect of the
crack is modelled by a non-linear (fractional) stiffness of the element with
the crack. The excitation of the system is characterized by the simultaneous
effect of static and dynamic harmonic load. The method is documented on
elementary examples, in which simulated measured data are determined by the
use of the numerical solution of the non-linear analytical model of a
structure with a crack.

###
Inverse determination of constitutive parameters from deep drawing experiment

M. KOMPIS, K. B. NIELSEN

Constitutive material parameters obtained from different experimentalmethods
can differ. In order to get higher accuracy of identified material parameters
for the deep drawing process, an inverse method is employed. Inverse methods
enable to use deep drawing experiment for inverse determination of material
parameters from the load-displacement curve. Principle of the method presented
is minimization of error between experimentally achieved and calculated
load-displacement curves in the least square sense. The core of the inverse
module used is optimization based on Levenberg-Marquardt algorithm where the
constants of Hollomon material model are taken as design variables.
Convergence of the inverse method connected with deep drawing experiment is
examined and good results are achieved.