Papers by Keyword: Material Interface

Abstract: Civil engineers like to use complex construction systems which resist mechanical strain well. Complex material and structural arrangement is possible to see in biological materials as wood but as bone or dentin too. This paper deals with a property trend of biological material, dentin, and can serve as an inspiration for designing resistant constructions. The analysis was carried out by a method of nanoindentation. The differences of property values depending on location of indents in dentin structure were surveyed. Especially, the differences of hardness and reduced modulus were important. The huge number of indents was made during the experiment. The indents were divided into categories according to the distance from the nearest material interface. The upward trend was found out for both observed properties. The category which was the closest to the material interface showed the average value of hardness ~ 965 MPa, whereas the furthest ~ 1222 MPa. It was growth more than 20%. Reduced modulus showed similar trend. These results are different from these which have been performed by other authors so far.

Abstract: This paper deals with a description of the crack behaviour in the layered alumina-zirconia ceramic laminate. The main aim is to investigate the crack behaviour in the compressive layer. The crack propagation was investigated on the basis of linear elastic fracture mechanics. Two dimensional finite element models were developed in order to obtain a stress distribution around the crack tip. The stress intensity factors were computed numerically employing the direct method. The change in the crack propagation direction was estimated using criterion based on the strain energy density factor. Sharp crack deflection in the compressive layer was predicted by mentioned approach. The determined crack behaviour is qualitatively in a good agreement with experimental observations.

Abstract: This paper deals with the fracture behaviour of layered ceramic composite with residual stresses. The main goal is to investigate the effect of residual stresses and material interfaces on crack propagation by more complex 3D finite element models. The crack behaviour was described by analytical procedures based on linear elastic fracture mechanics (LEFM) and generalized LEFM. The influence of laminate composition with residual stresses on critical values for crack propagation through the laminate interfaces was also determined. Good agreement has been found to exist between numerical results and experimental data. The results obtained can be used for a design of new layered composites with improved resistance against crack propagation.

Abstract: In order to solve the problem of three-dimensional two medium transportation problems of fluid dynamics, the transportation principles of a metal ball moving in constant velocity fields were given. The space district was dispersed into some cuboid Euler cells in the directions of three coordinate axes, along which mediums were transported by turns. The continuous boundary condition was adopted to simulate infinite boundary. The interface reconstruction method in the mixture cells was the volume fractions method. The numerical simulation result indicates that the shape and size of the medium cuboid can keep unchanged basically during the medium transportation. The overspeed transportation problem of the volume fractions method in the course of transportation is pointed out. The research may provide certain reference and guidance for solving the multi-material fluid dynamics problems.

Abstract: Failure of layered materials is frequently caused by the existence of interfaces between single layers. In structures loaded by long-term constant stress the damage can be described on micro-scale by material changes due to active creep mechanism and at the macro-level by a corresponding change of the stress and strain field. In the contribution the behavior of a crack propagating through the interface is analyzed. Primary attention is devoted to a crack with its tip at the interface under creep exposition. The step change of material properties at the bi-material interface means that standard fracture mechanics access is not applicable and a modified approach based on generalization of the classical concept has to be used. The approach is illustrated on the damage of a plastic pipe with protective layer.

Abstract: For nanoscale devices and structures, interface phenomena often dominate their overall thermal behavior. The feature scale of material interfaces usually originate from nanometer length and present a hierarchical nature. Considering to the limitations of the continuum mechanics on the characterization of nano-scale, the multiscale model featuring the interface could be very important in materials design. The purpose of this review is to discuss the applications of multiscale modeling and simulation techniques to study the mechanical properties at materials interface. It is concluded that a multi-scale scheme is needed for this study due to the hierarchical characteristics of interface.