Advanced Materials Research Vols. 150-151

Abstract: Under the acid rain corrosion condition, the shear-bearing capacity of the pretension prestressed concrete beam will attenuate gradually with the stirrup corrosion and concrete deteriorate. Moreover, the stress corrosion cracking failure and the bond force degradation of the prestressed wires that caused by the aggravated corrosion mediator ingress will further increase the shear failure risk of the pretension prestressed concrete structure without any symptom. The paper presents a shear bearing capacity calculation model of the pretension prestressed concrete beam bridge and discuss the time-variation model of the stirrup corrosion considering the effective prestress attenuation under the acid rain corrosion condition. The analysis method on anti-shear reliability of existing pretension prestressed concrete beam bridges under the sodium sulfate corrosion condition is proposed then. The method will be used in the durability and safety evaluation of the shear-bearing capacity of the existing pretension prestressed concrete beam bridges in the corrosion environment with acid rain.

Abstract: Reinforcement technology is widely used in rock-fill dams in high seismic hazard zones. The evaluation of reinforcement on deformation and safety is concerned and it is one of the major study objectives in rock-fill engineering. The residual deformation behaviors of reinforced rock-fill materials were experimentally studies by use of a triaxial apparatus. The effects were analyzed of intervals of reinforcement layers, confining pressures and the conditions of cyclic loading on residual deformation. Results show that reinforcement improves the residual deformation behaviors of rock-fill materials. Both the residual shear strain and the residual volumetric strain are deduced. Based on the test results, the mechanism of the influence of reinforcement on residual deformation is proposed tentatively.

Abstract: Polyvinylamine (PVAm) and polyvinylamine chloride (PVAm•HCl) were synthesized by Hofmann degradation of polyacrylamide (PAM). The reaction condition is gentle and the operation is safe, simple and economical so that it is a good reaction method. The chemical structures and thermal properties of the polymers were studied by Fourier transform infrared spectrometer (FTIR), nuclear magnetic resonance spectrometer (NMR), X-ray diffractmeter (XRD) and thermogravimetric analyzer (TGA). Synthesis of PVAm•HCl was confirmed by the intensities of the characteristic peak of -CONH2 decreased and the appearance of a new absorption peak at 1530cm-1 (due to N-H bond of -NH3+ ) in the FTIR spectrum, the appearance of the characteristic absorption peaks of carbon atoms in the 13C NMR spectrum, the appearance of chemical shift assignments of proton in 1H NMR spectrum and the appearance of characteristic dispersing diffraction peak between 22.5° to 25.2° in the XRD spectrum, respectively. PAM had three decomposing stages, but PVAm•HCl had two decomposing stages. TG curve of PAM and PVAm•HCl showed that the initial decomposition temperature were 190oC and 140oC, respectively. The thermal stability of PVAm•HCl was poorer than that of PAM.

Abstract: Polystyrene (PS) was synthesized by emulsion polymerization. 1,4-bis(chloromethoxy)butane (BCMB) was synthesized using 1,4-butanediol, formaldehyde and phosphorus trichloride as raw material. The linear poly(p-chloromethyl styrene) (PS-Meyl-Cl) was prepared high effectively using BCMB and anhydrous aluminium trichloride as the chloromethylation reagent and catalyst, respectively. In this method, carcinogenic compound (chloromethyl ether etc.) was avoided. The resultant polymers were characterized by gel permeation chromatography (GPC), Fourier transform infrared spectrometer (FTIR) and thermogravimetric analyzer. The results show that the molecular weight (Mw) of PS is big. BCMB has been prepared because of the strong absorption band observed at 1130cm-1 (due to C-O-C bond stretching vibration) and two new bands at 640 and 1315cm-1 (due to the bending vibration of C-Cl bond and stretching vibration of C-H bond in -CH2Cl, respectively). Chloromethyl groups were introduced into benzene ring of PS because of the appearance of the absorption peaks at 676 and 1419cm-1 (due to the bending vibration of C-Cl bond and stretching vibration of C-H bond in -CH2Cl, respectively) in the FTIR spectra. The thermal stability of PS-Meyl-Cl was decreased with increasing chloromethyl group. Moreover, there are two decomposing stages. The reaction condition is gentle and the operation is safe, simple and economical.

Abstract: In this paper, we utilize the deformation transformation optics (DTO) method to design electromagnetic beam bender, which can change the direction of electromagnetic wave propagation as desire. According to DTO, the transformed material parameters can be expressed by deformation tensor of the spatial transformation. For a beam bender, since the three principal stretches at each point induced by the spatial transformation are independent to each other, there are many possibilities to simplify the transformed material parameters of the bender by adjusting the stretches independently. With the DTO method, we show that the reported reduced parameters of the bender obtained by equivalent dispersion relation can be derived as a special case. An isotropic bender is also proposed according to this method, and it is fabricated by stacking dielectric materials in layered form. Experiments validate the function of the designed isotropic bender for a TE wave; it is also shown that the isotropic bender has a broadband with low loss, compared with the metamaterial bender. The isotropic bender has much easier design and fabrication procedures than the metamaterial bender.

Abstract: In this paper, the strength characteristics of magnesium phosphate cement (MPC) under the sub-zero temperature environment had been researched, the main factors of the strength development had been analyzed. The results show that: the MPC has high early strength under the sub-zero temperature environment, but the compressive strength dropped as the temperature decreased. The way of pre-curing the MPC for 30min at 20 could improve the strength of the MPC significantly. The strength of the MPC is influenced greatly by water-cement ratio under the sub-zero temperature environment, and the amount of the mixing water should be controlled strictly.

Abstract: The buckling-restrained braces(BRBs) with low yield strength(LYS) steel make good use of ductility and hysteretic energy dissipation of the low yield strength steel and are gradually applied in structural vibration. To foster BRBs with low yield strength steel in China mainland, the domestic LYS160 was used in BRB. The cross section was a simple shape. A static cyclic test was carried out, and the finite element analysis was conducted. The results show that the BRB with domestic low yield strength steel has good ductility, hysteretic energy dissipation and resistance to fatigue. A shaped cross section is simple and easy to promote application in China mainland.

Abstract: A systematic study has been carried out to investigate matrix properties by introducing nmSiO2 fillers into an epoxy resin matrix. The study has revealed that with shock wave method, nanoparticle infusion brings about superior mechanical properties to the matrix than what is usually given by the other method. The nmSiO2 is dispersed in a high-energy liquid shock wave pressure processing. The resulting structural composites have been tested under tensile loads to evaluate mechanical properties. Shock wave mixing utilized high-energy, high voltage transient shock wave in the water medium to process the material lying in the focal area. Nanoparticles tend to reduce void content of the nanocomposites and thus translate into increased mechanical properties. Focused, the influence of the high-energy shock wave method on the mechanical properties of nanocomposite were systematic studied. Using different processing conditions, the experiments were done to find the best processing. Overall, shock wave method is shown as a promising methode for preparation of aerospace epoxy composites.

Abstract: By the method of severe plastic deformation at high strain rate of coarse-grained copper under explosively dynamic loading, nanocrystalline(NC) copper was fabricated. The deformation process were simulated recur to Ls-Dyna3d finite element program , the effects of the strain on the degree of grain-refining were analysed. Finally, the dynamic mechanical properties of the NC copper were researched recur to split Hopkinson pressure bar(SHPB). The results show that it is feasible to fabricate nanocrystalline copper by explosively dynamic plastic deformation of coarse-grained copper and the grain size of the NC copper can be controlled less than 100 nanometer; higher strain at high strain rate is beneficial to the grain refining; the distribution of the grain size is not uniform along the loading direction; dynamic yield strength of the NC copper enhences with the decreasing of the average grain size and increasing of the strain rate.

Abstract: Copolymers of styrene (St) and vinyltrimethoxysilane (VTMS) have been synthesized by emulsifier-free emulsion copolymerization using ammonium persulfate (APS) as initiator. Acrylic acid used as functional monomer was also added into the emulsion. The effects of varying the concentrations of initiator and VTMS as well as the polymerization temperature on the polymerization conversion and rate were investigated in detail. The copolymer was characterized by Fourier transform infrared spectrometer (FTIR). Copolymerization of VTMS with St was confirmed by the appearance of an absorption peak between 1000 cm-1 to 1200 cm-1 (due to Si-O-C bonds) in the IR spectrum. The siloxane segments in the copolymer chain underwent hydrolysis and self-condensation, resulting in a change in the structure of the copolymers from linear into a cross-linked network. As a result, the organic and inorganic hybrid materials were formed. The polymerization rate increased with increasing polymerization temperature, molar concentration of initiator and decreased with increasing molar concentration of VTMS. The apparent activation energy and kinetic features of the polymerization system were also obtained.