Applied Mechanics and Materials Vols. 217-219

Abstract: Mg2Si reinforced hypereutectic Al-Si composite was prepared and the effects of electro- magnetic stirring on Mg2Si particle in the composite were researched. The results indicated that there were the important effects of electromagnetic stirring on size and morphology of the particle in the composite. The morphology and size of the particle in the composite were obviously improved by electromagnetic stirring. In comparison with the sample without isothermal holding, the size of the particle isothermally held slightly increased under the same stirring condition, but the roundness of the particle was improved. After isothermal holding, the mechanical properties of the composite prepared by electromagnetic stirring were improved to some extent.

Abstract: The method of using efficient inert projectile with highly efficient propulsion has great potential for the rapid and efficient excavation of rocks and ore in both surface and underground. In this paper, a series of numerical experiments were performed to simulate rock fragmentation resulted from steel fiber reinforced concrete (SFRC) projectile by using hydrodynamic finite element code AUTODYN. The fully coupled method was been adopted, in which the limestone, molded using Lagrangian mesh, is coupled to SFRC projectile molded using smoothed particle hydrodynamics (SPH) method. The numerical model was verified by comparing the simulation results with the field experiment data. Furthermore, the effect factors of geometric parameters of SFRC projectile and fibers content on the muck production were also discussed. The results of this study suggest that numerical simulation could be substituted for field experiment used for performance assessment of SFRC projectile.

Abstract: With good vibration alleviating properties, resin mineral composite (RMC) has been used to produce precision machine tool beds to satisfy the requirements of machining accuracy. Aggregate is one of the key components in RMC to bear loads, its gradation design determines the overall mechanical properties of the composite directly. In this article, an optimal method to determine critical dimension of screen holes is proposed based on Euclidean geometry and Particle interference theory, and the corresponding proportion of each component is adjusted on the basis of fractal theory. Variation tendency of porosity corresponding to different fractal dimension is obtained by using simulation method. On this basis, image processing technology is used to validate the aforementioned assumptions. Experimental results show that the optimal design has smaller porosity performance, which is consistent with the simulation results.

Abstract: Closed cell aluminum–fly ash floating beads composite foam was fabricated by stirring casting method. The reasonable processing parameters are: the foaming temperature is 750°C, the amount of foaming agent is 2%, and the foaming time is 8 min. Quasi-static compression tests shows that stress and strain curve of closed cell aluminum–fly ash floating beads composite foam have three regions, i.e. the elastic region, the stress platform region and the compression region.

Abstract: Advanced composite material not only is widely applied in aerospace, automobile and other industry fields, but also is one of the best materials for developing sport equipments. This paper introduces the advantages of carbon fiber composite material application in sport equipments and clarifies that application of this kind of high-tech material in sport equipments can greatly improve sport achievement by use of typical examples. Carbon fiber composite material has become one of essential novel materials for developing modern sport equipments.

Abstract: Tensile behavior of C fiber reinforced amorphous SiCN ceramic matrix composites (C/SiCN ) were investigated by tensile machine. The microstructure morphologies were observed by scanning electron microscope. The results indicate that the tensile stress-strain curves of C/SiCN composites dispaly typical elastic deformation and cracks propagation stages. The 1500°C pre-sabilization treatment of C/SiCN in vacuum facilitates room temperature tensile stress growth. The higher treated temperature such as 1900°C is yet opposite. The reasons were attributed to thermal stress relaxation of C/SiCN after pre-stabilization treatment in vacuum.

Abstract: Iron matrix composite reinforced with VC reinforcements was produced by in situ synthesis technique. The microstructure of the composites was characterized by X-ray diffraction and scanning electron microscopy. The micrographs revealed the morphology and distribution of the reinforcements. The results show that the composite consists of VC carbide as the reinforcing phase and α-Fe as the matrix. The distribution of spherical VC particulates in iron matrix is uniform, and the matrix microstructure of Fe-VC composite is pearlite.

Abstract: The CNTs have been incorporated in PET/PTT matrix and PET/PTT-CNTs composites have been prepared. The CNTs can act an effective nucleating agent in the PET/PTT matrix and the percolation threshold in PET/PTT-CNTs composites is about 6 wt%. SEM graphs indicated that the CNTs are well dispersed in the PET/PTT matrix.

Abstract: A combined model taking account of the dislocation strengthening effects and particle cracking during tensile straining based on Eshelby equivalent inclusion method is presented to model the deformation behavior of SiCp/Fe composites. Stress-strain curves of the composites were simulated and it is found that the curves vary obviously with the volume fraction and particle size. The yield stress is increased significantly by increasing the volume fraction and decreasing the particle size. Stress in particles is very high during straining and the fraction of cracked particles increased obviously with increasing the particle size. These results indicate that higher volume fraction and finer particles can give better mechanical properties of the composites attributed to the increased load sharing effect and dislocation strengthening effects of the matrix.

Abstract: Si and C of rice rusk were used as silica source and pore-forming agent to prepare cordierite-mullite ceramics at 1380°C for 5 h soaking. The Nd2O3 additive was added to improve the sintering properties. The bending strength, porosity, and thermal expansion coefficient were measured. The composition was characterized by X-ray diffraction (XRD). The microstructures of the sintered samples were observed by scanning electron microscopy (SEM). The cordierite-mullite ceramic doped with 2% Nd2O3 have high prorosity and low thermal expansion coefficient, its bending strength reaches 20.55 MPa. The addition of Nd2O3 decreases the mullite formation temperature to 1200 °C