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IMPROVEMENT OF THE RELIABILITY OF DIFFERENT SILICON CARBIDE GRADES FOR AUTOMOTIVE APPLICATIONS

Objective

It is presently not possible to predict the failure of ceramic components on the basis of simple microstructural and fracture mechanical parameters. In this work, computational (finite elements, simulation of microstructure and fracture) as well as fracture mechanical and metallographical methods are used in conjunction with model considerations.
Reliability of polycrystalline ceramics was looked into as a volumetric effect resulting from the distribution in volume of single microcracks (defects) or from the coalescence of microcracks. They may also induce generalised damage under load or arise at the tip of a moving crack exhibiting an R-curve, before catastrophic failure. A general methodology, based on experimental and computational work in conjunction with fracture mechanical model considerations, has thus been developed.

In the case of posthipped alpha-silicon carbide, it was shown that the distribution of the rupture stresses is the image of the microstructure only if the internal stresses are considered. Experimentally the Weibull modulus varies with temperature. The reliability of posthipped alpha-silicon carbide may thus be enhanced by improvement of powder sieving.

Often microcracks are induced by mechanical loading. Their size and density depends on the material, the processing route and the resulting microstructure.

Finite element methods, taking into account the specific reliability of each part of a complex structural piece, like a rotor, have been developed. In addition, simulation of predefined grain size distributions and their damage under load or during cooling have been studied formally.

Provided the constitutive laws of damage of given microstructures are correlated experimentally, the possibility to forecast failure by a deterministic approach is now available.
IT IS PRESENTLY NOT POSSIBLE TO PREDICT THE FAILURE OF CERAMIC COMPONENTS ON THE BASIS OF SIMPLE MICROSTRUCTURAL AND FRACTURE MECHANICS PARAMETERS.

IN THIS WORK, CONSTITUTIVE EQUATIONS ACCOUNTING FOR THE DAMAGE PROCESS WILL BE DEVELOPED AND ADAPTED TO COMPUTATIONAL (FINITE ELEMENT METHOD) TECHNIQUES. THE PURPOSE OF THIS IS TO FORECAST THE FAILURE OF COMPONENTS ON THE BASIS OF EXPERIMENTAL AND THEORITICAL CONSTITUTIVE MODELLING IN CONJUNCTION WITH COMPUTATIONAL WORK.

AS A RESULT OF THE PROPOSED RESEARCH, IT IS EXPECTED TO IMPROVE CONSIDERABLY THE ECONOMIC POTENTIAL OF FABRICATED CERAMICS. THIS WILL BE ACHIEVED BY THE DEVELOPMENT OF A METHODOLOGY FOR THE DETERMINATION OF AN OPTIMAL MICROSTRUCTURE WITH RESPECT TO DAMAGE AND OF AN OPTIMAL SHAPE OF THE STRUCTURAL COMPONENT WITH RESPECT TO RELIABILITY.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Institut des Sciences de la Matière et du Rayonnement de Caen
Address
Boulevard Du Maréchal Juin
14050 Caen
France

Participants (2)

Elektroschmelzwerk Kempten GmbH
Germany
Address
Herzog-wilhelm-straße 16
80331 München
UNIVERSITAET STUTTGART
Germany
Address
Holzgartenstrasse 17
70049 Stuttgart