Advanced Materials Research Vols. 79-82

Abstract: The analyses of concrete from a bridge in Handan district shows that most bridges concrete should have cracked. The study of the technical measures against the performance deterioration of existing reinforced concrete bridges will undoubtedly become an imperative issue. In recent years, lots of bridges have been built in Handan. We choose a reinforced concrete bridge to investigate the effect of the effective member stiffness degradation and durability degradation induced by vehicle overload, vehicle overflow, rebar corrosion, and concrete deterioration on highway reinforced concrete bridges. And Static loading test was conducted at its middle span. Based on the test data in different circumstances, the seriousness of vehicle overload is discussed. In consequence, the performance of highway reinforced concrete bridges on stiffness degradation and durability degradation is more serious compared with the bridge under the condition of non-overloading. The results show that the process of rebar corrosion in highway reinforced concrete bridges is sped up under the condition of vehicle overload and vehicle overflow on the highway reinforced concrete bridges, which decreases the durability of the bridge structure, and the speed of the durability degradation increases as time goes on. The paper conclusion is instructive for the construction and maintenance of bridge.

Abstract: In the present work, biomorphic TiC/C ceramic with a woodlike structure was synthesized from wood template. The TiC coatings were formed on the surface of C-wood-template in a reaction medium consisting of Ti powder in a mixture of molten LiCl-KCl salts under an argon atmosphere. The structure and biomorph of the TiC/C ceramic were characterized by XRD, TG-DSC, SEM and EDX analyses. The results indicated that Ti powder had reacted with carbon in the cellular wall to form TiC coatings. The resulting biomorphic TiC/C ceramic retained well the structure of the original biomorph of the wood.

Abstract: Al8B4C7 should be a successful antioxidant in carbon-containing refractories, and it have excellent hydration resistance. In this paper, the synthesis process of Al8B4C7 and the mechanism have been studied. Aluminum, borax and activated carbon powders were used as starting material. Using borax as the source of B, can greatly reduce the cost of synthesis. Our experiments showed that use these materials can synthesize Al8B4C7, and the final product is closely related to the temperature and ratio of raw materials. Al8B4C7 appeared at about 1300°C, and with the temperature increased, more Al8B4C7 was generated in the heating samples. The phase compositions of these samples heated at 1700°C were Al8B4C7, Al2O3, Al4O4C and Al2OC.

Abstract: Infrared heating is featured with a high heating rate up to 50oC/s. It is a very powerful tool applied in brazing application, so infrared heating has been used to study the kinetics of brazing process in recent years. The importance of brazing Ti alloys has been increased in past twenty years due to the strong demand from chemical and aerospace industry. Based on the previous studies, the use of Ti-based brazes alloyed with Cu and Ni contents is considered as one of the best alloys in brazing Ti and its alloys due to their high bonding strength. However, the presence of Ti-Cu-Ni intermetallics in the brazed joint has a strong effect on the joint strength, and the reaction kinetics of the joint is still unclear. The purpose of this investigation is concentrated on transmission electron microscopy (TEM) study of the infrared brazed CP-Ti using Ti-15Cu-15Ni filler, and microstructural evolution of the infrared brazed joint is unveiled. It is helpful for industrial applications of Ti-based alloys.

Abstract: Using the tightly focused visible light (wavelength λ=488nm) illuminating, the ferroelectric domain patterns of the undoped lithium niobate crystal have been demonstrated. The influence of the visible light intensity on the domain nucleation field was investigated. The reduction of nucleation field decreases exponentially with increasing incident irradiation intensity. Once a domain is nucleated it can be dictated by the far-field light diffraction patterns. An assumption is proposed that the reduction of nucleation field is directly related to the defects mobility and structure of the crystals.

Abstract: Its primary purpose of this study is to provide a comprehensive investigation on its dynamic performance of MR damper under high impact load. A test had been firstly done in order to identify its high shear viscosity of MR fluid. Then, its thermal performance of MR damper under high impact load is analyzed in order to aid its structure design of MR damper intended for weapon recoil mechanisms applications and improve its performance of elimination of heat. Further, Experimental analysis and performance evaluation of MR damper under impact load have been done by numerical simulation and hardware-in-the-loop simulation, including its acceleration response and pressure response of back cavity under different flow coefficient and the same inputting current, and its acceleration response and pressure response of back cavity under the same flow coefficient and different inputting current. Based on these simulation results, the shear-thinning phenomena and its dynamic response under saturated input current are analyzed and some useful conclusions are made. Finally, experimental results indicated that the developed MR damper under high impact load can achieve a good controllability for recoil applications.

Abstract: To study rupture mechanism of structural steel, fracture experiments were tested on 12 notched plates with different thickness. The results of experiments indicated that the first crack initiated at the notched edge and expanded rapidly along the width of the plates after running through the thickness. Finally, the specimens fractured at the critical section, the fracture ductility decreased with the thickness. By numerically simulating the fracture stress field of the notched plates at initial cracking based on generalized yield model, the applicability and accuracy of the suggested fracture criterion were comparatively verified.

Abstract: Reconstituted bamboo Lumber suffers surface and mechanical properties degradation after exposure to outdoor environment. In this paper, Neosinocalamus affinis bamboo bundles was selected to thermo-treated at three temperature levels (160,180 and 200°C) for 2 hours and investigated the effect of xenon-arc light irradiation with water spray on the changes in color, thickness and mechanical properties of reconstituted bamboo lumber. The results indicated that the surface color of the samples changed rapidly during the irradiation process and the change rate decreased as the increasing of thermo-treated temperature. The mechanical properties analysis indicated that MOE wasn’t much affected by the thermo-treated and artificial weathering test, whereas MOR and shear strength decrease after exposure. The thickness swelling after exposure was improved by the thermo-treatment and decreased as the treated temperature increased.

Abstract: A commercial phenol formaldehyde based resole thermosetting resin supplied by Borden Chemical Australia Pty. was filled with ceramic-based fillers (Envirospheres or SLG) to increase its flexural strength. By performing flexural tests at a range of filler addition levels, the optimal addition level of SLG was able to be determined in terms of workability, cost and performance. The composites obtained were post-cured in conventional oven and in microwaves respectively. It was found that the maximum flexural strength of the microwave cured composites were only 5% lower than those cured in conventional oven when the percentage by weight of SLG was 24%. However, the time required for post-curing was also reduced from 10 hours (in conventional oven) to 40 minutes (in microwaves).

Abstract: In-situ spherical icosahedral quasicrystal phase (I-phase) was fabricated in Mg-Zn-Y-based alloys by metal mold casting route. The effects of Mn and/or Cu on spheroidized process, morphology and microhardness of primary I-phase were studied in this paper. The results showed that the solidified morphology of I-phase depended on the stability of spherical I-phase during the subsequent growth and critical radius Rr of the spherical I-phase. Only when actual radius smaller than critical radius Rr can spherical IQC be formed. The effects of the fourth component and degree of undercooling on Rr were studied for the first time. Amazing spherical minisize IQC had been produced by improving cooling rate using a water-cooled copper mold. Multicomponent spherical IQC is hopeful of being strengthening phase to novel metal composites.