Advanced Materials Research Vols. 79-82

Abstract: The fracture toughness of SLG filled phenolic composites have been determined by short bar tests. It is expensive to prepare the samples for the tests. Therefore, it is necessary to develop a mathematical model that will predict the fracture toughness of particulate filled phenolic composites. Mathematical models for tensile strength, Young’s modulus are available but not for impact strength and fracture toughness. There is no sign that it can be built up from simple mathematical model; polynomial interpolation using Lagrange’s method was therefore employed to generate the fracture toughness model using the data obtained from experiments. From experiments, it was found that the trend of the fracture toughness of the samples cured conventionally was similar to that cured in microwaves; it is therefore possible to predict the fracture toughness of the samples cured in microwaves from shifting the mathematical model generated for fracture toughness of samples post-cured in conventional oven. The shifted model represented the fracture toughness of the samples cured in microwaves vey well.

Abstract: In-service welding is a kind of important method to ensure the integrality of oil gas pipeline and the thermal cycle of which is significant for repairing. Used SYSWELD to establish model and simulate thermal cycle of in-service welding on X70 steel gas pipeline, compared thermal cycles of in-service welding and air-cooling welding, studied the influence of gas pressure and flow rate on thermal cycle. The result shows that peak temperature of the coarse grain in heat affected zone (CGHAZ) of in-service welding is similar to air cooling welding, but the cooling time of t8/5, t8/3 and t8/1 decreases at certain degree. Peak temperature of CGHAZ of in-service welding doesn’t vary match with gas pressure and flow rate either. t8/5, t8/3 and t8/1 decrease when gas pressure increases. t8/5 varies with the gas pressure linearly. When the pressure is less than 4MPa, t8/3 and t8/1 decrease rapidly while gas pressure increases. When the pressure is more than 4MPa, t8/3 and t8/1 decrease slowly while gas pressure increases. t8/5, t8/3 and t8/1 decrease when the flow rate increases. When gas flow rate is less than 10m/s, t8/5, t8/3 and t8/1 decrease rapidly while flow rate increases. When gas flow rate is more than 10m/s, t8/5, t8/3 and t8/1 decrease slowly while flow rate increases.

Abstract: Framed curing mold is subjected to an uneven thermal load, gravity force and the pressures from composite parts and auxiliary tools during autoclave processing of thermosetting composite structures. And those loads induce the warpage of framed-mold. The warpage of framed-mold during autoclave processing influences dimensional precision of composite parts. In the present work, a three-dimensional finite element model for prediction of the warpage of framed-mold during autoclave processing has been developed. This model solved the coupling problem between the deformation and the temperature distribution of framed-mold and allows analysis of all major identified deformation influencing factors. And numerical predictions compare quite well with experimental measurements. A parametric study was performed using FEM program to examine the effect of varying the thickness of framed-mold, the shape and the dimension of mold vents.

Abstract: According to the empirical electron theory of solids and molecules, the valence electron structures of GP zone, θ″, θ′ and θ phases in Al-Cu alloys are calculated out. The results show that the number of covalent electron pairs on the strongest bond A of GP zone is greater than that of of the  matrix, i.e., the obstruction of in GP zone for dislocation movement is stronger than that of in the  matrix. Only based on the bond strength of composition atoms, it can be found, , , and  phases have strengthening effects for Al-Cu alloys. The strengthening effect of  is the strongest, and  is weaker, and  is the weakest. Compared with, the bond strength of  and  is weaker than that of . From the value of nA, it is easy to reconstruct the bonds of GP zone, , and , but is difficult to reconstruct the bonds of .

Abstract: The energy released from damages may give rise to small surface displacements and cause transient elastic waves in materials. Wave propagation of thin plates usually takes the form of lamb waves, and the modes of the lowest symmetric (S0) and anti-symmetric (A0) lamb waves are called the extensional and the flexural modes, respectively. In this study, a formulation, including the effect of shear deformation and rotary inertia, was derived to valuate the velocity of plate waves. The characteristics of plate wave propagation in thin laminated plates were investigated. Acoustic emission (AE) signals were generated by function generators and lead breaks, and propagated in laminated plates. These waves would be detected by broadband AE sensors because of their high sensitivity. With wavelet transform, AE waves were analyzed and the wave velocities of A0 and S0 modes were exactly calculated. Moreover, a simple method was presented to evaluate delamination in laminated plates. The length of delamination was predicted, and agreed well with the actual length.

Abstract: Advanced fabrication techniques to miniaturize electromechanical systems have brought us into the regime of nanoelectromechanical systems (NEMS). Understanding the mechanical properties of NEMS components is of fundamental importance in the operation of these devices. In this paper, we have reported the deformation behavior of a single-crystal simply supported nano-beam under the uniformly distributed load. By using the molecular dynamics simulation, we have investigated the influence of span the nano-beam on the bending characters. Due to surface effect, the nano-beam shows a different behavior under the uniformly distributed load.

Abstract: Shot peening is a complex cold working process used to improve the fatigue life of metallic parts. This investigation is devoted to the modeling and simulation of the residual stress field resulting from the shot peening process, in which the finite element method was employed using a rate sensitive material. The history of energies during explicit dynamic analysis was discussed and the solution time for explicit analysis was analyzed. For the single shot impact model, the effect of shot velocity, shot size, incident angle was studied. In addition, the effect of repeated impacts on the residual stress within the target plate was studied. Furthermore, the multiple shot impacts of shot peening process were accomplished and the effect of peening coverage was investigated based on different shot models.

Abstract: The reaction of maleic anhydride ring-opening was calculated by Gaussian03. The Density Function Theory (DFT) method were employed to study the geometries of maleic anhydride and ethanol on the base of B3LYP/6-31G in the paper. The transitional states(Ts1,Ts2) of maleic anhydride ring-opening reaction were found by TS method and were proved by IRC calculation. The results showed that from the reactant to product, the energy reduced about 129.25337kJ/mol,The computation results showed that the reaction was exothermic and matched up well with experiment. Nowadays the MAH multipolymers were studied extensively.Because of C=C double bond has double substitutions and the great Spatial steric hindrance, MAH was always regarded as representative that couldn’t carry out homopolymerization[1,2]. Much attention has been paid to MAH polymerization(Homopolymerization[4] and Copolymerization[5-15])gradually Long and his colleagues[3] published papers on MAH homopolymerization in 1963. The related reports have been increased since MAH multipolymer was found to possess anti-tumor and biological activity[16]. According to the polymerization mechanism，epoxide ring-opening esterification were divided into three kinds: cationic polymerization, anionic polymerization and coordination polymerization.The saturated polyesters were prepared through maleic anhydride and alkene oxide reaction, generally using anionic polymerization initiated by hydroxyl compound such as alcohol, water and carboxylic acid. maleic anhydride ring-opening reaction initiated by alcohol(Eq. 1) was discussed in this paper.

Abstract: Residual potential is a very important performance index of organic photoconductor (OPC). At present, research shows that the purity of charge transport material will seriously influence residual potential of OPC. But in past research we found that some OPC used charge transport material with very high purity still has very high residual potential. With quantum calculation and x-ray diffraction we found that some materials are optical isomer and some have cis-trans isomerism. So in order to improve performance of OPC we should separate isomerism.

Abstract: In this paper, both geometrical and electronic properties of rutile TiO2 (110) surfaces have been investigated using First-Principles Density-Functional calculations with CASTEP code, the model of stoichiometric surface is a (2x1) super-cell which has 12 atomic-layer slabs with the bottom 6 held fixed, the bridging-oxygen vacancy surface has been constructed by removing a neutral bridging oxygen atom from this surface. For the stoichiometric surface, the atom relaxations are: Ti6f (+0.2865Å), Ti5f (-0.1039Å), O3f (+0.2433Å) and Ob (+0.0075Å), we find no reconstruction and no surface states in the band gap, the density of states (DOS) is similar to the bulk except the lower conduction band intensity, in accord with recent experiments. Whereas, as a result of bridging-oxygen vacancy, the atom relaxations exchanged and reconstruction occur. The 2 excess electrons left behind removal of one bridge O atom are localized on the Ti-t2g conduction band orbitals, convert some of the Ti4+ ions into Ti3+ ions and result a compensatory shift in the Fermi level. The band gaps we calculated for stoichiometric surface is similar to the bulk, but its increase can be found for Ob vacancy surface.