Advanced Materials Research Vols. 217-218

Abstract: The fracture behavior of a brittle coating on an elastic substrate under residual stress is investigated. Using a mechanical model, the analytical solutions for the distribution laws of the tensile stress developed in the coating, the shear stress developed along the interface and the relationship between the crack density of the coating and the residual stress can be obtained. The analytic relationship between the crack density and the residual stress can also be taken as a new expression to estimate the magnitude of the residual stress. A numerical example is presented to show how the crack density varies versus the residual stress.

Abstract: The problem of delay-probability-distribution-dependent stability analysis for a class of discrete-time stochastic delayed neural networks (DSNNs) with mixed time delays is investigated. Here the mixed time delays are assumed to be discrete and distributed time delays and the uncertainties are assumed to be time varying norm bounded parameter uncertainties. The information of the probability distribution of the time-varying delay is considered and transformed into parameter matrices of the transferred DSNN model, in which the time-varying delay is characterized by introducing a Bernoulli stochastic variable. By constructing a new augmented Lyapunov-Krasovskii functional and introducing some new analysis techniques, a novel delay-probability-distribution-dependent stable criterion for the DSNN to be stable in the mean square sense are derived. These criteria are formulated in the forms of linear matrix inequalities.

Abstract: This study is devoted to investigate the effects of wood fiber content on structure and properties of wood fiber /poly(lactic acid) bio-composites (WF/PLA bio-composites). The WF/PLA bio-composites with WF from 30% to 60% and from 70% to 90% were prepared using melt extrusion and high-speed mixing methods respectively. The physical, mechanical, thermal, and macromolecular properties of WF/PLA bio-composites were evaluated. The results are as follows: Density of WF/PLA bio-composites increased when WF increased from 30% to 60%, and decreased when WF increased from 70% to 90%. Water resistance of bio-composite decreased with increasing WF content. The flexural strength of WF/PLA bio-composites were lowered when adding WF into PLA. The flexural strength decreased when WF increased from 30% to 50%, and then increased when WF increased from 60% to 80%. The flexural modulus of the bio-composite was higher than that of PLA without WF. Both n and w of PLA in WF/PLA bio-composite were decreased more than 70% with WF increased. The Tg, Tm values of PLA in the bio-composites were decreased with the WF increased. The cold crystal temperature (Tcc) was decreased with WF increased at low WF content. All the property changes were related to the decreasing of molecular weight of PLA in WF/PLA bio-composites.

Abstract: For getting good passive self-adaptability, the model for single wheel system contacting with the terrain is established, and the degree of freedom (DOF) needed is studied when the system has good passive self-adaptability; further more, the model of one sided wheel-suspension is set up, and the DOF is obtained by analyzing with corresponding proof is given; several relative features of some common passive self-adaptive rovers are concluded, and these information testifies the universalism of this paper’s conclusions.

Abstract: Springback is the prominent problem in bending forming of sheet metal, which is difficult to control accurately, especially for the complex shaped bending parts. The change of friction conditions will cause significant changes of bending springback amount. The theoretical analytical model of quadrangle parts bending, which takes into account of the harden ability, anisotropy and elastic deformation of material, is proposed in this paper based on the plane deformation assumption and the bending theory of sheet metal, the quadrangle parts bending of wide sheet is analyzed theoretically, the approximate calculation relational expression is derived between friction coefficient and springback angle, and the influence of friction on springback is discussed. In the same conditions, the springback result deduced from theoretical formula is basically consistent with numerical simulation and experiment result.

Abstract: High speed steel based ceramic preforms with three-dimensionally interpenetrated micropores were fabricated using the mixture of TiH2, CaCO3 and stearic acid as pore-forming agent. A self-made vacuum high pressure infiltration furnace was used to infiltrate the preforms with Pb-Sn based solid lubricants to create almost fully dense self-lubrication composites. The microstructure and properties of HSS-based self-lubrication composites were investigated as a function of sintered porosity. A quantitative analysis of microstructure was correlated with crushing strength，microhardness and wear rate to understand the influence of pore size, shape and distribution on mechanical and tribological behavior. Crushing strength and microhardness decreased with an increase in porosity. Meanwhile the decrease in microhardness with increasing porosity was slightly. The friction coefficient of HSS-based self-lubrication composites decreased with increasing the volume fraction of lubricant due to the self-lubrication and unique micropore structure. Within the range of lubricant volume fraction from 0% to 14%, the wear rate of the composites decreased steadily with the increase of lubricant content in the composites. Micropore structure and lubricant volume fraction play an important role in determining wear resistance of the composites whereas the measured bulk properties seem to be of minor importance.

Abstract: This paper, analyzes some parameters with the help of Cone Calorimeter (CONE) for the time to ignition, smoke extinction area, heat release rate, carbon monoxide yield and mass loss rate. The results show that the fire retardant agents affect KVV’s flame retardant property. Such as TTI ( time to ignition ) is prolonged to nearly two times, and the average HRR ( heat release rate ) reduces about 18% compared with the ordinary one and the maximum HRR down about 33%of its counterpart.

Abstract: Bulk metallic glass Ti42Cu37.1Co4Zr8Sn2Ag2Be4.9 that can be cast into a fully amorphous rod of more than 6 mm in diameter by copper molder casting has been developed through systematic alloy design. The bulk metallic glass exhibits high fracture strength (f＝2071 MPa) and good ductility (f＝5.83％) under compression.

Abstract: In order to realize the real particles’ irregular shape representations, which considering the real particles’ deformable and non-deformable characteristic. Firstly, we extracted the three dimensional coordinate information of real ballasts by dealing with ballast’s X-ray tomography imagines. Secondly, considering the deformable and non-deformable characteristic, two mdoelling methods were introduced based on real particles’ three dimensional coordinates. The deformable particle models are generated by non-overlapping combined basic-spheres, while the generation process is controlled by the extraction accuracy of real particles’ three dimensional coordinates. The non-deformable particle models are generated by overlapping combined basic-spheres, while the generate process is controlled by two parameters. Both two modelling method are initial conditions unrelated, and the model generation process can be repeatedly. Finally, in the condition that two methods’ basic-sphere numbers are approximately equally, the conclusion that non-deformable modelling method represents the real particles’ shape more efficiently can be drawn by error analysis.

Abstract: The hollow silica was fabricated by using monodispersed polystyrene microspheres as core template and tetraethyl orthosilicate as silica source, and polyimide nanocomposite films with different hollow silica concentration were successfully prepared via in situ polymerization. The hollow silica and nanocomposite films were characterized. The results indicated that the diameter of the hollow silica is around 30nm and the dielectric constant of the nanocomposite films enhance with the increase of the concentration of the hollow silica.