DEVICE FOR COMPARATIVE EVALUATION
OF THE HEAT RESISTANCE OF CERAMIC SPECIMENS
BY RECORDING ACOUSTIC EMISSION
E. V. Voinich
and A. A. Frolov
Translated from Novye Ogneupory, No. 5 pp. 44 – 47, May 2009.
Original article submitted June 17, 2008.
A device is described for comparative evaluation of the thermal shock resistance of ceramic specimens of
identical shape and dimensions by recording acoustic emission (AE) pulses during air cooling from 1000C.
The number of AE pulses in a unit of time, whose intensity exceeds the 10% level of maximum signal inten
sity, is used as a comparative characteristic for thermal shock resistance of ceramic materials. Comparison of
the AE pulse distribution with respect to amplitude contains additional information about the thermal shock
resistance of comparable specimens. With use of high-temperature furnaces with a considerable working vol
ume and treatment of repeated cooling conditions the measurement part of the device may be used for evaluat
ing the comparative thermal shock resistance of ceramic specimens and objects of any shape and size during
cooling from above 1000°C.
Keywords: thermal shock resistance, ceramic specimen, acoustic emission (AE), layered ceramic.
During development of objects made from ceramic mate-
rials thermal shock plays a considerable role, i.e. the capacity
to withstand rapid temperature drops during operation. It is
well known that the thermal shock resistance of ceramic ob
jects depends on that of the ceramic material, and also the
size and shape of specific objects, heat transfer coefficient,
and this is a natural physical property of the material from
which objects are manufactured. It is customary to specify it
by criteria for thermal shock resistance, and shape and di
mension factors . Standard methods for determining ther
mal shock resistance provide an idea about the properties of
the material itself, only making it possible indirectly to deter
mine the thermal shock resistance of developed objects.
Analysis of acoustic emission (AE) signals that arise during
thermal loading of ceramic specimens, is one method of esti
mating their thermal shock resistance . These studies give
a broad spectrum of information about the behavior of speci
mens with a temperature drop. During a test the required
temperature gradients are created by partial loading of re
fractory specimens in molten metal  or by creation of a
temperature gradient over the radius of a circular specimen
of standard size . However, in developing ceramic objects
a considerable role is played by estimation and comparison
of the thermal shock resistance of specific objects and speci-
mens that are not of standard shape and size manufactured
from different materials and by different procedures with a
lack of information about the effect of the shape and size fac
tor. Therefore a requirement arises for performing compara
tive evaluation of the thermal shock resistance of finished
objects and specimens of highly refractory ceramics under
conditions that approach the operating conditions for a fin
ished object. In order to obtain this information a method of
recording AE is most suitable with rapid cooling of specific
objects and specimens.
CONSTRUCTION OF A DEVICE
FOR ESTIMATING THE THERMAL SHOCK
RESISTANCE OF CERAMIC SPECIMENS
In order to obtain comparative characteristics of speci
mens made of materials with high thermal shock resistance a
device was created for recording AE pulses during cooling in
air. The device makes it possible to record AE signals and to
perform comparative evaluation of the thermal shock resis
tance of ceramic specimens and objects from the amount and
characteristics of AE pulses that arise during cooling. The
Refractories and Industrial Ceramics Vol. 50, No. 3, 2009
1083-4877/09/5003-0204 © 2009 Springer Science+Business Media, Inc.
I. N. Frantsevich Institute of Metrials Science Problems, NANU,