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Distortions and cracking of graded components during sintering

: Riedel, H.; Kraft, T.

Kaysser W.A.:
Functionally Graded Materials 1998. Proceedings of the 5th International Symposium on Functionally Graded Materials : Held in New Town Hall, Dresden, Germany, October 26 - 29, 1998
Uetikon-Zürich: Trans Tech Publications, 1999 (Materials science forum 308/311)
ISBN: 0-87849-833-8
International Symposium on Functionally Graded Materials <5, 1998, Dresden>
Conference Paper
Fraunhofer IWM ()
constitutive equations; finite element method (FEM); powder technology; sintering; wraping crack

The aim of the project is to develop methods for predicting distortions and cracking during the fabrication of gradient materials, and to apply them to simple geometries (tubes, beams and plates). Crack formation during sintering is described as the instability of the homogeneous sintering state. It is found that a density disturbance may grow unstably, but only when the material is severly constrained in three dimensions. The equations for describing the distortions of graded beams and plates during sintering are developed. Examples are shown for plates with gradients in grain size, temperature and composition (Mo and ZrO2). If the gradient is carefully balanced, nearly planar plates can be obtained after sintering. Threedimensional finite element studies of graded circular plates show that the initially axisymmetric mode of deformation becomes unstable in favor of a warping with two symmetry planes (like a potato chip).