MODELING OF THERMAL-CRACKING IN ELASTIC AND ELASTOPLASTIC 2-PHASE SOLIDS

A review is given about fracture mechanical investigations concerning the thermal crack initiation and propagation in one of the segments or in the material interface of two- and three-dimensional self-stressed two-phase compounds. The resulting boundary value problems of the sta tionary thermoelasticity and thermoplasticity for the cracked two-and three-dimensional bimaterial structures considered are solved using th e finite element method. Furthermore, by applying an appropriate crack growth criterion based on the numerical calculation of the total ener gy release rate G of a quasistatic mired-mode crack extension the furt her development of thermal crack paths starting at the intersection li ne of the material interface with the external stressfree surface of t he two-and three-dimensional elastic bimaterials could be predicted In the case of the disklike two-phase compounds, the theoretically predi cted crack paths show a very good agreement with results gained by ass ociated cooling experiments. Several specimen geometries consisting of different material combinations and subjected to uniform and nonunifo rm temperature distributions have been studied rising the relevant met hods of fracture mechanics. Thereby thermal cracks propagating in one segment of an elastic bimaterial only obey the condition G(II) = 0, wh ereas for interface cracks a mired-mode propagation ir always existent where the G(II) values play an important role. Moreover, by applying the proposed crack growth criterion the possible crack kinking directi on theta of an interface crack tip out of the interface could be pred icted by taking into consideration the finite thickness of an interlay er (interphase). In addition, an analysis of the stress and strain fie lds in the vicinity of thermal interface cracks in the discontinuity a rea of two- and three-dimensional elastoplastic two-phase compounds ha s been performed by using the Fe-method. Thereby a heat source Q was a ssumed in one of the two materials in the neighborhood of an interface crack tip. The corresponding stress states in the bimaterial structur es and especially in the vicinity of the interface crack tip have been calculated by applying the incremental J(2)-plasticity and using a bi linear hardening material law and based on a sequentially coupled solu tion of the heat transfer and the thermal stress boundary value proble ms. Finally, the failure assessment has been performed on the basis of the local J-integral which, for three-dimensional interface cracks, w as recently generalized by two of the authors.