摘要:

This is a brief survey of some recently developed micromechanical modeling methods and certain results concerning the overall thermomechanical response and average local fields in both elastic and inelastic composite materials with extensions to laminated plates.

ISSN:0149-5739    

DOI:10.1080/01495739708956129

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Stress waves that develop following the rapid uniform heating of linear-elastic spheres and long cylindrical rods display a stress-focusing effect as they proceed radially toward the center in these geometries. The stress-focusing effect is the phenomenon that, under a rapid uniform heating, stress waves reflected from the free surface of the sphere or the cylindrical rod result in very high stresses at the center, even though the initial thermal stress might be relatively small. This phenomenon may be observed in the solid spheres subjected to the spherical symmetric heating and in the cylindrical rods subjected to the cylindrical symmetric heating. This type of heating may be caused by the absorption of infrared rays radiation or electromagnetic radiant energy. This article reviews recent extensions of the analytical methods for the problem of thermal shock in spheres and cylindrical rods, especially for the problem of the thermal stress-focusing effect in spheres and cylindrical rods. First, considering the problem of thermal shock in a hollow sphere subjected to the rapid uniform heating, if the ratio of the outer radius to the inner radius of the sphere increases, the peak tangential stress at the internal surface becomes higher and higher. In the limit case, for a solid sphere, it might be possible to observe the stress-focusing effect. Next, as for the analysis of a cylindrical rod due to the rapid uniform heating, stress waves also show the stress-focusing effect. Hence, the major accomplishment of this study is in gaining a better understanding of the thermal stress-focusing effect in solid spheres and cylindrical rods.

ISSN:0149-5739    

DOI:10.1080/01495739708956130

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

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-arid three-dimensional self-stressed two-phase compounds. The resulting boundary value problems of the stationary thermoelasticity and thermoplasticity for the cracked two- and three-dimensional bimaterial structures considered are solved using the finite element method. Furthermore, by applying an appropriate crack growth criterion based on the numerical calculation of the total energy release rate G of a quasistatic mixed-mode crack extension the further development of thermal crack paths starting at the intersection line of the material interface with the external stressfree surface of the two- and three-dimensional elastic bimaterials could be predicted. In the case of the disklike two-phase compounds, the theoretically predicted crack paths show a very good agreement with results gained by associated cooling experiments. Several specimen geometries consisting of different material combinations and subjected to uniform and nonuniform temperature distributions have been studied using the relevant methods of fracture mechanics. Thereby thermal cracks propagating in one segment of an elastic bimaterial only obey the condition GII= 0, whereas for interface cracks a mixed-mode propagation is always existent where the GIIvalues play an important role. Moreover, by applying the proposed crack growth criterion the possible crack kinking direction ϑ of an interface crack tip out of the interface could be predicted by taking into consideration the finite thickness of an interlayer (interphase). In addition, an analysis of the stress and strain fields in the vicinity of thermal interface cracks in the discontinuity area of two- and three-dimensional elastoplastic two-phase compounds has been performed by using the FE-method. Thereby a heat sourceQwas assumed in one of the two materials in the neighborhood of an interface crack tip. The corresponding stress states in the bimaterial structuresand especiallyin the vicinity of the interface crack tip have been calculated by applying the incremental I2-plasticity and using a bilinear hardening material law and based on a sequentially coupled solution of the heat transfer and the thermal stress boundary value problems. Finally, the failure assessment has been performed on the basis of the localJ-integral which, for three-dimensional interface cracks, was recently generalized by two of the authors.

ISSN:0149-5739    

DOI:10.1080/01495739708956131

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor