Acoustic Emission During Deformation and Fracture of Ceramics

Gogotsi, G. A.; Drozdov, A. V.; Negovskii, A. N.

doi:10.1016/b978-0-408-22163-4.50016-7

Ultrasonics International 83 1983

DOI: 10.1016/b978-0-408-22163-4.50016-7

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Acoustic Emission During Deformation and Fracture of Ceramics

G. A. Gogotsi¹,

A. V. Drozdov²,

A. N. Negovskii³

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1986

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Cited by 6 publications

(8 citation statements)

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“…3b). In this case uniform data was obtained both for the measurement of bending and also the AE-registration [8]. where Pb is the destructive load, a, b, h are the shoulder of bending, the width, and height of the specimen respectively.…”

mentioning

confidence: 99%

“…To study the R-curves (the relationship between the coefficient of stress intensity and the length of the developing crack) we used both the well-known method of pliability [7], and also a method of assessing the length of such cracks with respect to the registration of AE [8]; we also made optical measurements of the length of the cracks. Sharp cracks were formed in specimens under rapid static loading conditions, using a special device designed in IPP.…”

mentioning

confidence: 99%

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Partially stabilized ZrO2 ceramic and its behavior under load

1991

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Ceramics based on zirconia are finding increasing use as materials in various areas of technology, and in medicine. As a result more attention is being paid to improving and investigating such products in many developed countries [i, 2, etc.], including the USSR where the problem has been dealt with in Ogneupory [3, enc.], Problemy Prochnosti [4], and a number of other articles.However, in almost all the articles that have presented data on the mechanical behavior of zirconia, somewhat limited data is given, since normally complex studies have not been carried out, although such results would yield valid (especially comparative) all-round information on the ceramic; this enables us to assess with confidence the expected working capacity and form general ideas on the actual behavior under load.One reason for the above situation is the fact that complex investigations require a sufficient number of identical specimens which it is impossible to obtain in an industry which does not possess a good production control procedure for ceramics. Such investigations also require standard testing equipment (preferably concentrated in one place) which will facilitate the production of various test parameters that show low measurement errors. These conditions were observed in the present work in which we selected zirconia ceramics that had proved themselves in practice, and in previous research [5]; these were partially stabilized with magnesium oxide. It was used by Nilcra Ceramics Pty. Ltd (Australia) to prepare ball valves for the chemical and petroleum industries, also components in experimental diesel engines, artificial dentures, etc. (Fig. I). A feature of this ceramic is that it passes through additional technical processing, depending on its purpose (like steel).In our investigations we concentrated on TS-grade ceramic (subsequently referred to as Mg-ChSTs) designed for working in thermal conditions. Dies, for example, and other components for high-temperature drawing of copper wire were made from it.Plate-like blanks were obtained by using a method in which 3% MgO (mass) was added to the starting powder. Then it was ballmilled (grinding medium made of ZrO 2) in distilled water to an average particle size of 1-3 pm. Then the powder was dried in a stream of heated air. The blanks were preformed by dry pressing with synthetic plasticizer, and then hydrostatically pressed at 200 MPa. They were fired in a furnace heated with gas at 1700~ Af-

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Partially stabilized ZrO2 ceramic and its behavior under load

1991

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“…As was shown in the previously published papers, the method of AE can also be used for evaluating the characteristics of crack resistance [12,14,15] and thermal shock resistance [I0, 15,16] of ceramics. However, in this case, it is necessary to consider the specific features of deformation of ceramic materials (just as in the case of strength evaluation) and for for this purpose, the magnitude of their brittleness index can be used successfully.…”

mentioning

confidence: 98%

“…This fact made it possible to evaluate the average value of o b for a group of specimens and its scatter on the basis of the distribution parameters of the stresses OA [5,12]. For evaluating the strength characteristics of the relatively brittle ceramics, the AE method (just as the active acoustic methods [l])is significantly more effective.…”

mentioning

confidence: 99%

Effectiveness of the acoustic-emission method for evaluating the strength properties of ceramics and refractories depending on the specific features of their deformation

Gogotsi

Negovskii

1988

Refractories

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Active acoustic methods are being successfully used for evaluating the strength characteristics of ceramics and refractories [i]. These methods are based on recording the parameters of propagation of ultrasonic waves in the materials. The effectivenees of their application is not the same in all materials and depends on the structural features. There are situations where the largest (coarsest) structural inhomogeneities alone are revealed by ultrasonic control whereas the strength is determined by the considerably smaller cracklike defects that cannot be recorded during such a control. This leads to a decreased reliability of the data of ultrasonic control and to an increased probability of obtaining inadmissibly large errors when evaluating the strength characteristics of the materials.In view of this, Sadowska-Boczar et al. [2] and the authors attempted to use a passive acoustic method, i.e., an acoustic emission (AE) method that makes it possible to reveal only those defects that are developed during the loading process and are, consequently, the most danterous ones (for the given type of the stress'-strain state of the body). In view of the fact that AE is caused by the deformation and fracture processes of materials under the action of an applied stress, its nature is closely related to the specific features of these processes. In order to take these features into account, we used the structure-sensitive brittleness index X [i, 3] which was determined on the basis of the deformation diagrams of the materials and was found to be a fairly effective parameter for predicting the behavior of the ceramics subjucted to mechanical and thermal loads [4]. The conducted experiments showed the differences in the degrees of effectiveness of the AE method when testing brittle (X = I) and relatively brittle (X < i) materials [3].In order to evaluate the strength levels of ceramics and refractories, AE was recorded during bend tests of the specimens of these materials (according to the four-point bending scheme) using an AF-II apparatus fitted with a wide-band receiving transducer having a band frequency ranging from 0.02 up to 2.0 MHz. In contrast to the previously followed procedure [5], numerous measures were taken in the present study to improve the accuracy of the AE measurements.Incorporating a SA-100 multichannel analyzer of the spectrum of the AE signals in the measuring circuit made it possible to determine the frequenzy ranges in Which AE is observed in different types of ceramics and to establish the corresponding ranges of measurements of the AF-II apparatus.In this case, the obtained data indicate that in the majority of brittle ceramics (such as boron and silicon carbides, silicon nitride, and aluminum oxide), fairly wide-band AE signals emerge (within the measuring range 0.02-2.0 MHz of the SA-100 device). The spectrum of the AE signals of relatively brittle materials and most of-,the coarse-grained materials (such as luminoboron nitride, aluminosilicates, and magnesites) is narrower and, as a rule, its limit...

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“…To reveal the features of deformation and microdamages of ceramic materials attempts have been made to use the acoustic emission method [2,4], which is based on the detection and recording of the elastic waves occurring in local rearrangements of the structure of the material [5]. This work is devoted to an investigation of the features of deformation and the acoustic emission process in bending of CZ and MZ corundum refractories [6] to the charge of which was added monoclinic unstabilized zirconium dioxide for formation of microcracks in them.…”

mentioning

confidence: 99%

Acoustic emission in the deformation and failure of corundum refractories

Gogotsi¹,

Drozdov²

1986

Refractories

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Acoustic Emission During Deformation and Fracture of Ceramics

Cited by 6 publications

References 1 publication

Partially stabilized ZrO2 ceramic and its behavior under load

Partially stabilized ZrO2 ceramic and its behavior under load

Effectiveness of the acoustic-emission method for evaluating the strength properties of ceramics and refractories depending on the specific features of their deformation

Acoustic emission in the deformation and failure of corundum refractories

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