Papers by Author: X. Peng

Abstract: A scanning electron microscope (SEM) was used for observing the microstructures of a Mactridae shell. It showed that the shell is a kind of natural bioceramic composite, which consists of aragonite sheets and organic matrix with laminated structure. It also showed that there are various reinforced microstructures in the shell, which include a kind of lambdoidal one. The maximum pullout force of the lambdoidal reinforced microstructure, which is related to the fracture toughness of the shell, was analyzed and compared with that of a conventional 0°-structure based on their representative models. The result indicated that the maximum pullout force of the lambdoidal reinforced microstructure is markedly larger than that of the 0°-structure, which was experimentally verified.

Abstract: As a typical biological material, bone possesses high fracture strength and fracture toughness, which are closely related to its exquisite microstructure. SEM observation of a cannon bone shows that the bone is a kind of layered bioceramic composite consisting of hydroxyapatite sheets and collagen matrix. The hydroxyapatite sheets are of long and thin shape, distributing in parallel. The fracture toughness of the bone is analyzed with the representative model of the hydroxyapatite sheets and the concept of maximum pullout energy. It is shown that the lathy shape as well as the parallel distribution of the hydroxyapatite sheets increases the pullout energy and endows the bone with high fracture toughness.

Abstract: Casting magnesium alloys are heterogeneous materials containing numerous voids. Assuming the voids are spherical, in the present investigation, the evolution equations of the growth and nucleation of the voids have been presented. Combining the evolution equation of the void growth with that of the void nucleation, the evolution rule of the voids was obtained. Based on the void evolution rule a nonclassical elastoplastic constitutive model involving void evolution was developed. The corresponding numerical algorithm and finite element procedure were developed and applied to the analyses of the elastoplastic response and the porosity of casting magnesium alloy. The calculated results show the satisfactory agreement with experiments.