Advanced Materials Research Vols. 463-464

Abstract: The variation of microstructure and properties of RE-7075 Al alloy after homogenizing annealing were studied by some modern analytical instruments which including OM(optical microscope),SEM(scanning electron microscopy),EDS(energy dispersive spectroscopy ), Brinell hardness and conductivity meter of SIGMASCOPE SMP10 type in this experiment. The results shows that the alloy′s microstructure was uniform ,reduced the volume fraction of second phase,increased supersaturation of matrix and eliminated gradually dendritic segregation in homogenizing annealing state. The primary phase of matrix microstructure contain α(Al),T(Al2Mg3Zn3) and grain boundary microstructure include α(Al),Al2Cu,AlCuMg4La4 after homogenizing annealing.Compared with as cast condition,the conductivity and the hardness reduced after homogenizing annealing.

Abstract: By measuring the surface temperature of the mould, the condition of solidified shell can be monitored by thermocouples fixed to the mould. Breakouts can be predicted and effectively avoided by monitoring the dynamic characteristics of thermocouples temperature in the casting process. A thermomechanical model was developed to analyzed the heat transfer in the mould.The breakout prediction system of continuous casting has been analyzed with consideration of the principles, model and thermocouples installation. The system has been designed and implemented in the steel plants.

Abstract: After the invention of mesoporous material, the chiral mesoporous materials had been regarded as a hot research issue. Inspired by the chiral phenomenon, in this investigation, we presented several aspect of chiral mesoporous material from its first appearance, especially stated the template that could be used to prepare chiral mesoporous material, including chiral template and achiral template, besides, the different mechanisms and several distinguished scientists’ works were introduced, and some application of these material were introduced such as catalyst, HPLC stationary phases and many other fields.

Abstract: In order to find a convenient approach to design the mix of rubberized asphalt concrete (RAC) and make full use of the properties of RAC, a kind of RAC-13 (13 is the nominal maximum aggregate size of the mixture) was designed by means of coarse aggregate void filling method (CAVF). A series of conventional tests of asphalt mixture with five asphalt-rubber aggregate ratio(ARAR) were carried out to check the target mix design and evaluate the performance of RAC. Performance evaluation tests such as Marshall and submerged Marshall stability test, moisture damage test and wheel tracking test were included. Test results show that the high temperature stability, moisture susceptibility and road performance of RAC-13 designed with CAVF method are all favorable. The recommended optimum asphalt-rubber aggregate ratio(OARAR) is 7.1% under the condition of skeleton structure. CAVF is a good means for designing RAC to ensure its stone-on-stone contact structure.

Abstract: Common river sand is expensive due to excessive cost of transportation from natural sources. The increased sand mining affects the aquifer of the river bed and causes many environmental problems. Also large-scale depletion of these sources creates environmental problems. In such a situation the manufactured sand can be an economical alternative to river sand. Manufactured sand is defined as the residue, tailing or other non-valuable material after the extraction and the processing of rocks to form fine particles less than 4.75mm. Use of manufactured sand as a fine aggregate in concrete and mortar draws serious attention of researchers and investigators. Aggregate makes up a significant portion of concrete. The physical properties of aggregate play an important role in elastic and shrinkage properties of concrete and mortar. In this paper, the effect of manufactured sand as fine aggregate in tensile, elastic and shrinkage properties of concrete and mortar are discussed.

Abstract: The ability of rapid prototyping (RP) technology to fabricate direct part of any complex shape as a sacrificial pattern in shorter lead time has benefited the foundry industries significantly. The quality of investment casting (IC) parts is directly related to the master pattern fabricated from RP process. The main objective of this study was to evaluate the quality characteristics of various RP patterns that were fabricated by various RP processes which include 3D Printer (3DP), Fused Deposition Modeling (FDM) and Multijet Modeling (MJM). Evaluation of the RP patterns was carried out on dimensional accuracy, surface roughness and pattern shrinkage. Different internal pattern designs for the RP parts were developed using Insight software for FDM process and Solidworks 2011 for other RP systems. In addition to the quality assessments, the effect of the internal pattern designs on the burn out behaviour of the RP patterns was also evaluated. Experimental results showed that FDM and MJM produced patterns with better accuracy, surface roughness and part shrinkage when compared to 3DP. It was evident that the internal pattern structure improved the accuracy of the patterns produced from all RP processes. Results showed that FDM and MJM processes were superior in terms of mold cleanliness when no residual ash was observed during the burn out stage. Significant oxidation of ceramic powder was observed on the molds of the 3DP patterns which need to be removed manually from the molds.

Abstract: In order to significantly increase not only the load carrying capacity but also the ductility of the steel tube columns filled with recycled aggregate concrete from the earthquake waste, two different strengthening methods by using externally bonded of carbon fibre reinforced polymer (CFRP) to strengthened the columns was proposed. Composite columns of CFRP reinforced and steel circular steel tube columns are studied in this study. The aims were to study the contribution of the CFRP sheets applied in enhancing the load carrying capacity and ductility of the steel tube columns with different concrete type, normal concrete and recycled aggregate concrete. The results demonstrate that the ultimate load carrying capacity and ductility of the steel tube columns filled with recycled aggregate concrete can be increased satisfactorily by full wrapping and partial wrapping arrangement of CFRP sheets. Moreover, stiffness of the columns strengthened was also increased greatly due to the restraining effect offered by CFRP and the full wrapping arrangement is better than the partial wrapping arrangement in enhancing the stiffness and the load carrying capacity.

Abstract: Two forms of reinforced concrete pier were compared by internal force analysis and nonlinear stability analysis. According to the restriction of the stability and intensity, size optimization of the high piers’ section is calculated by means of differential coefficient. The results of the calculation and analysis indicate that the parameter optimization of the piers’ section of Long-span continuous rigid frame bridges is feasible by using the optimization model, and the results are provided to the optional design of Long-span continuous rigid frame bridges.

Abstract: Cold pressure welding has been used as an industrial process with an increasing rate for several years. In this study, cold pressure welding has been applied to aluminum and copper alloy sheets having commercial purity. Hydraulic press having 150 metric-ton capacities has been used for welding process. As the surface roughness and the weld deformation ratios of aluminum sheets increased, tensile strength of the joints also increased. Purchased specimens with original roughness had the lowest weld deformation as-is and it was not possible to join these sheets at 30% weld deformations. Hardness increases due to local hardening at the interface as a result of cold deformation. Results showed that the cold pressure welding technique in lap form resulted in strong Al-Al joints and the intermetallic layer formed in Al-Cu joints did not affect the joint strength to a great extent.

Abstract: This paper reports the results of a research work aimed at examining the use of externally bonded of fiber reinforced polymer (FRP) sheets, consisting of carbon FRP (CFRP) and glass FRP (GFRP), as a strengthening solution to upgrade the shear capacities of reinforced concrete (RC) beams. A total of 7 RC beams were constructed and tested under four-point bending, i.e. two reference beams with different concrete strength and without any FRP sheets, one beam reinforced by GFRP sheets and four beams reinforced by CFRP sheets. Externally bonded FRP shear strengthening was found very effective in upgrading the shear strength of the beams strengthened. The shear strengths of RC beams strengthened were improved greatly by FRP sheets, and the strength gain caused by the FRP sheets was in the range of 31-74%. Test results also show that the more ductile behaviour and higher ultimate strength are obtained for the beams with FRP shear strengthening by using high concrete strength.