Applied Mechanics and Materials Vols. 152-154

Abstract: The activate effect of various activator on fly ash was studied according to the comparative tests of cement strength. The result shows that the sulfate activator and alcohol amine activator composite mixture has the best activate effect under the reasonable mix ratio. The composite mixture can obviously affect fly ash cement strength, and under the 50% mixing amount of fly ash, the 3d strength of cement is improved by 30% to 50%, and the 7d strength of cement is improved by 20% to 30%. Activate mechanism of the composite activator was studied through the XRD, SEM and other microscopic testing methods.

Abstract: The coupling effect of physics, chemistry and mechanics is through charring layer in the process of ablation of the insulation material. Description of the structure and mechanical properties of charring layer is the critical factor to numerical computation for foretelling the ablation of insulation material. The characteristic of charring layer structure of EPDM insulation at sorts of ablating condition were analyzed, and based on characteristic of porous medium of charring layer, the mechanical model with porosity as parameter was modeled by using theory of solid porous medium. According to the intensity determination of charring layer, the coefficient of intensity model was determined, then, the failure criterion of charring layer was set up, which can provide the mechanical parameters of charring layer for numerical computation to foretell the ablation of insulation material.

Abstract: The electrochemical corrosion inhibitions of potassium zinc phosphate were studied by polarization, open circuit potential measurements, electrochemical impedance of the pigment extract and coating immersion test. Dynamic analysis shows that in pH=7 3.5% NaCl extract, KZn₂(PO₄)(HPO₄) functions as a cathodic inhibitor on steel and its efficiency is even superior to other phosphates. The inhibiting efficiency of the pigments on steel decrease in the order: KZn₂(PO₄)(HPO₄) > aluminum zinc phosphate > zinc phosphate ≧ aluminum triphosphate The coating tests show that potassium zinc phosphate can efficiently enhance the inhibition properties of coating and prevent the erosion of the corrosive medium by improving the barrier and hydrophobicity of the coating. The anticorrosive property of the pigments decrease in the order: KZn₂(PO₄)(HPO₄)> aluminum zinc phosphate > zinc phosphate ≈APW-1.

Abstract: The effect of MgO on performance of belite-barium calcium sulphoaluminate cement (B-CBAS) was investigated through orthogonal tests. The results show that the formation of C₃S can be improved at low temperatures by mixing MgO. SO₃ decreasing the viscosity of fused mass in sintering process was beneficial to solid solution of MgO in B-CBAS clinker. The solid solubility of MgO in B-CBAS was higher than that of Portland cement, which indicated that high-magnesium limestone can be used in B-CBAS. Even MgO content reached 5.14%, the soundness of B-CBAS was still in safe, whose compressive strength at 3d and 28d curing age were 49.1MPa and 81.9MPa. This indicated that this kind of cement has good mechanical properties.

Abstract: In cutting aluminum alloy 6061, continuous chips have a negative influence on the machining operation. Usually, Pb is added in order to break continuous chips. However, from the standpoint of environmental protection, it is necessary to improve chip breakability without adding Pb. One effective measure to improve chip breakability is by adding Si to aluminum alloy 6061. However, the influence of Si content on tool wear has not been fully examined. In this study, in order to clarify the influence of a diamond-like carbon (DLC) coating layer with a Cr-based interlayer, namely (Al,Cr)N, on cutting performance, aluminum alloys having different Si contents were turned. The substrate of the tool material was high-speed steel (1.4%C). The tool wear and the surface roughness were experimentally investigated. The following results were obtained: (1) In cutting two kinds of Al-Si alloys, namely the Al-2%Si alloy and Al-4%Si alloy, the progress of wear of the DLC/(Al,Cr)N-coated tool was slower than that of the DLC-coated tool. Therefore, the (Al,Cr)N interlayer was effective for decreasing the tool wear of the DLC-coated tool. (2) The wear progress of the two kinds of DLC-coated tools in cutting of Al-4%Si alloy was faster than that in cutting of Al-2%Si alloy. (3) In cutting of Al-2%Si alloy with the (Al,Cr)N/DLC-coated tool, the surface roughness was almost constant in the range of a cutting distance from 0.1 km to 9.5 km.

Abstract: A model high-Tc Super-conducting Magnet Energy Storage (SMES) magnet, which is winded with high-Tc super-conducting Bi-2223 trip, is cooled by GM cryo-cooler. The SMES cooling feature is investigated. It took about 17 hours to reach the minimum temperature for the SMES cooling, and its axial temperature difference is 2.8 K, the radial temperature difference is less than 1 K. The thermal contact resistance results in the resource of larger axial direction temperature difference. By improved, the cooling time is about 25 hours for the cryo-cooler cooled 35kJ SMES magnet, its axial direction temperature difference is 0.4 K. At loading 140 A direction current, the magnetic density is 4.5 T, no temperature rise is observed. At loading 60 A alternating current, the upside temperature rise of 35kJ SMES magnet is about 5 K. The 35kJ SMES magnet has been operated stably 480 hours.

Abstract: Polymer derived SiC ceramics usually present a relatively low thermal conductivity for the large porosity and complex phases. In order to obtain condensed SiC ceramic with low thermal conductivity, a preceramic precursor polycarbosilane (PCS) was selected as the raw materials. And hot press sintering processes were performed at 1600 °C under Ar atmosphere with the holding time in the range of 20 to 40 min for consolidation. The microstructures and phases were analyzed by scanning electron microscopy (SEM) with energy disperse X-ray spectroscopy (EDS), X-ray diffraction (XRD) and high-resolution transmission electron microscope (HRTEM). The specific heat, thermal diffusivities and thermal conductivities were measured and investigated from room temperature to 650 °C. A minimum thermal conductivity of 4.13 W•m-1•K-1 was obtained at 650 °C with a holding time of 30 min.

Abstract: The 1st, 2nd and 3rd generations of hydroxyl-terminated hyperbranched polyesters (HBPE-1, HBPE-2, and HBPE-3) were synthesized. A3rd generation hyperbranched polyester (HBPE-3) was used as original crosslinking agent to prepared hyperbranched waterborne polyurethane dispersions (HPU). FTIR spectra confirmed that this reaction really took place. The experimental data indicated that, compared with the linear one, the hyperbranched HPU aqueous dispersions exhibited lower viscosity, and larger particle size. For the hyperbranched HPU films, mechanical properties were obviously enhanced.

Abstract: Based on the view of relative movement, the group settlement was considered as a movement of current moving up in the suspended particle layer. The expressions of Reynolds number and drag coefficient were set up by the analysis of dimension and stress of dynamic equilibrium state. The theoretic formulae on group settlement of uniform sediment in the laminar region and turbulent region are proposed. It is verified by measured data, and shown that the calculated value by the theoretic formula and measured value agree with each other fairly well.

Abstract: The damaging factor was defined firstly, mean while the fatigue character of metal rubber was discussed. Then the relationship between damaging factor and cyclic loading times had been summarized through fatigue tests. Finally observed the pattern of fracture face, cavities and flaws of the fatigue wires inner the metal rubber components with electronic scanning microscope, some technical methods of improving the wearing resistivity of metal rubber material had been brought forward.