In order to study the scale characteristics of heterogeneities in complex media, a random medium is constructed using a statistical method and by changing model parameters （autocorrelation lengths a and b）, the scal...In order to study the scale characteristics of heterogeneities in complex media, a random medium is constructed using a statistical method and by changing model parameters （autocorrelation lengths a and b）, the scales of heterogeneous geologic bodies in the horizontal and the vertical Cartesian directions may be varied in the medium. The autocorrelation lengths a and b represent the mean scale of heterogeneous geologic bodies in the horizontal and vertical Cartesian directions in the randQm medium, respectively. Based on this model, the relationship between model autocorrelation lengths and heterogeneous geologic body scales is studied by horizontal velocity variation and standard deviation. The horizontal velocity variation research shows that velocities are in random perturbation. The heterogeneous geologic body scale increases with increasing autocorrelation length. The recursion equation for the relationship between autocorrelation lengths and heterogeneous geologic body scales is determined from the velocity standard deviation research and the actual heterogeneous geologic body scale magnitude can be estimated by the equation.展开更多
The indentation test is a localized testing technique;therefore,the role of the material size-effect and local non-uniformity is of much importance.The influence of the heterogeneity in size-independent materials has ...The indentation test is a localized testing technique;therefore,the role of the material size-effect and local non-uniformity is of much importance.The influence of the heterogeneity in size-independent materials has been studied previously.The present work detailedly investigated the influence of the material size-effect and heterogeneity(inclusions near the indenter tip)on the indentation hardness using a size-dependent strain gradient plastic theory.And it was found that when considering the material size-ffect,shallow hard inclusions in the heterogeneous materials more significantly enhance the material indentation hardness compared with the size-independent materials which are based on the conventional plastic theory.This hardening effect is be-lieved to be related to the elevation of the load and local constraints of large deformation.The effect of material inhomogeneity mainly comes from the non-uniformity of the structure rather than the inclusion modulus itself especially when the size-effect is involved,and the transition range of the inclusion modulus'influence is pretty narrow.The effect of non-uniformity becomes negligible after the initial inclusion depth is larger than its diameter.The horizontal offset of the indenter from the inclusion is also of much sensitivity to the influence of the heterogeneous indentation.This paper focuses on the scaling relationships in micro-and nanoindentation,the influence of non-uniformity in microscopic materials is studied and supplemented as well.展开更多
基金sponsored by the 973 Program (No. 2009CB219505)the Talents Introduction Special Project of Guangdong Ocean University (No. 0812182)
文摘In order to study the scale characteristics of heterogeneities in complex media, a random medium is constructed using a statistical method and by changing model parameters （autocorrelation lengths a and b）, the scales of heterogeneous geologic bodies in the horizontal and the vertical Cartesian directions may be varied in the medium. The autocorrelation lengths a and b represent the mean scale of heterogeneous geologic bodies in the horizontal and vertical Cartesian directions in the randQm medium, respectively. Based on this model, the relationship between model autocorrelation lengths and heterogeneous geologic body scales is studied by horizontal velocity variation and standard deviation. The horizontal velocity variation research shows that velocities are in random perturbation. The heterogeneous geologic body scale increases with increasing autocorrelation length. The recursion equation for the relationship between autocorrelation lengths and heterogeneous geologic body scales is determined from the velocity standard deviation research and the actual heterogeneous geologic body scale magnitude can be estimated by the equation.
基金the National Natural Science Foundation of China(Grant Nos.11890681,12032001,and 11521202).
文摘The indentation test is a localized testing technique;therefore,the role of the material size-effect and local non-uniformity is of much importance.The influence of the heterogeneity in size-independent materials has been studied previously.The present work detailedly investigated the influence of the material size-effect and heterogeneity(inclusions near the indenter tip)on the indentation hardness using a size-dependent strain gradient plastic theory.And it was found that when considering the material size-ffect,shallow hard inclusions in the heterogeneous materials more significantly enhance the material indentation hardness compared with the size-independent materials which are based on the conventional plastic theory.This hardening effect is be-lieved to be related to the elevation of the load and local constraints of large deformation.The effect of material inhomogeneity mainly comes from the non-uniformity of the structure rather than the inclusion modulus itself especially when the size-effect is involved,and the transition range of the inclusion modulus'influence is pretty narrow.The effect of non-uniformity becomes negligible after the initial inclusion depth is larger than its diameter.The horizontal offset of the indenter from the inclusion is also of much sensitivity to the influence of the heterogeneous indentation.This paper focuses on the scaling relationships in micro-and nanoindentation,the influence of non-uniformity in microscopic materials is studied and supplemented as well.
