Applied Mechanics and Materials Vols. 105-107

Abstract: Phytic acid coatings were formed on 6063-Al alloy during immersion in phytic acid solution with various pH and phytic acid concentration for different time. The corrosion resistance of the coated samples was investigated using Tafel polarization technique. The results show that the effect of technological parameters on corrosion resistance of phytic acid coatings is great. With the increase of pH, the corrosion resistance of the coated sample is firstly increased and latterly decreased; it is optimum when pH was 3.0. The corrosion resistance of phytic acid coatings is increased largely with phytic acid concentration and immersion time. The anodic and cathodic corrosion processes of the coated 6063-Al alloy are inhibited markedly, and the corrosion current density is decreased for more than two orders of magnitude.

Abstract: The aim of this study is to investigate the influence of EPS content on failure mode, stress-strain relationship and elastic modulus of expanded polystyrene aggregate concrete (PAC) with density lower than 900 kg/m³ under uniaxial loading. The results show that PAC performs a good compressibility in the compression failure process. Apparent oblique crack appears in the case of uniaxial compression specimen damage; the lower the density is, the smaller the tilt angle of oblique cracks will be. Stress-strain curve of PAC with density larger than 422 kg/m³ maintains a straight line relationship on ascending segment but varies with the density on the descent segment. The lower the density is, the larger PAC residual relative stress will become. Elastic modulus of PAC is proportional to 5.85 times index of relative density.

Abstract: This paper is referred to other literature on properties of metal fatigue testing methods and data analysis procedure methods. According to high cycle fatigue testing, double-wall-brazed-tube is loaded with different stimulated vibration force by shaking table and is forced to vibrate. In the experience, strain of key parts is measured with Electrical resistance Strain measurement Methods. By curve fitting of experimental data, we gain the fitting function of the specimen’s fatigue life and draw its S-N curve. In accordance with the analysis of experimental data and S-N curves, it is concluded that fatigue properties of metallic materials can not fully reflect fatigue properties of a specimen and that the cross-sectional size of a specimen has much effects on its fatigue life.

Abstract: The multi-hit of armor piercing projectiles (APPs) is one of the main treats to lightweight vehicles. Based on published ballistic experiments of Al2O3/Al2024 laminated composite armors against 7.62mm APP, the debonding of ceramic tiles was successfully simulated by setting reasonable material model and contact algorithm. A method named Geometric Intervals Method (GIM) was developed for simulation of multi-hit and its feasibility and rationality were investigated with the finite element code LS-SYNA. The numerical results shows that GIM has taken into account the effects of target damage caused by former APP impact on the target responds to later APP penetration. GIM can be used to simulate composite amours against multi-hit.

Abstract: Phytic acid coatings were formed on AZ91D-Mg alloy during immersion in 5.0 g/L phytic acid solution for different time. The corrosion resistance of the bare and coated samples was investigated using Tafel polarization and Electrochemical Impedance Spectroscopy (EIS) methods, and the corresponding electrochemical corrosion parameters were analyzed. The results show that the anodic and cathodic corrosion processes of AZ91D-Mg alloy are conspicuously inhibited with phytic acid coatings; the overall corrosion resistance index of AZ91D-Mg alloy is increased with immersion time; and the corrosion protection efficiency of phytic acid coatings is up to 97.8%.

Abstract: A high temperature vulcanized (HTV) silicone rubber/octavinyl polyhedral oligomeric silsesquioxane (POSS) hybrid was prepared. The micromorphology of the cured hybrid was investigated by scanning electron microscopy (SEM); the thermal degradation stability of this hybrid was studied by means of thermal gravimetric analyses (TGA); the degradation kinetics of this hybrid was also studied using Doyle method and Coats-Redfern method. Results showed that aggregation of self-cross-linked octavinyl POSS appeared in the HTV silicon rubber/POSS hybrid. The incorporation of POSS into silicon rubber networks enhanced the thermal degradation resistance of the matrix. Activation energy derived by the Coats-Redfern method (142.24 kJ/mol) showed a good agreement with the mean value derived by the Doyle method (146.51 kJ/mol); the thermal degradation reaction of the hybrid followed a three-dimensional diffusion law (D₄).

Abstract: In this paper, silicon direct bonding was performed by two different cleaning processes, and the bonding quality was obtained by tensile test and IR test. For (100) P-type double side polished wafer, the optimum process condition was established with respect to the results of two different cleaning processes. The cleaning process of NH3•H2O/H2O2/H2O (Standard Cleaning 1, SC1) after the H2SO4/H2O2 (piranha solution) was found to be better suited for high bonding quality. The bonding strength of the SC1-cleaned samples is about 5.4 MPa with partially crack but no more than 0.7 MPa for the only piranha solution cleaned samples.

Abstract: With the purpose of decorative bright nickel plating process, nano-nickel and ordinary bright nickel coatings were prepared by applying the electro-deposition method with DC and PRC respectively. The grain sizes, organizational structures and surface morphologies of samples were characterizated by X-ray diffraction(XRD) and scanning electron microscopy (SEM) analysis. The corrosion resistance of the samples were determined by immersion corrosion test, salt spray corrosion test and electrochemical methods. The results showed that the corrosion resistance of reverse pulsed electrodeposition nano-nickel coating is superior to the DC electrodeposition nickel coating.

Abstract: In this paper, the experimental results on the fixed end supported PFRP channel beams subjected to three-point loading are presented. The aims of this study are to evaluate the effects of the span (L) on the structural behaviors, the critical buckling moments and the modes of failure of the beams, and to compare the obtained critical buckling moments with those obtained from the modified LFRD steel design equation in order to check the adequacy of the equation. The beam specimens have the cross-sectional dimensions of 76x22x6 mm, with span-to-depth ratio (L/d) ranging from 13 to 52. A total of twenty-six specimens were tested. Based on the experimental results, it was found that the loads versus mid-span vertical deflection relationships of the beams are linear up to the failure. On the contrary, the load versus mid-span lateral deflection relationships are geometrically nonlinear. The general modes of failure are the flexural-torsional buckling. Finally, the modified LFRD equation can satisfactorily predict the critical buckling moment for L/d exceeds 20. However, for L/d < 20, the equation overestimates the critical buckling moment of the beams and more development is needed.

Abstract: This paper describes a series of flexural tests conducted on the H-section beams fabricated from SM490 plate of thickness 0.6mm with nominal yield stress 315 MPa. Flexural members with large width-to-thickness ratios in the flanges or the web may undergo local buckling before lateral-torsional buckling. The local buckling has a negative effect on the moment capacity based on the lateral-torsional buckling. Simple bending moment capacity formulas for flexural members were calibrated to the test results to account for interaction between local buckling and lateral-torsional buckling. The ultimate flexural strengths predicted by the proposed formulas for direct strength method were compared with the AISC (2005) and Eurocode3 (2003). The comparison showed that the moment formulas proposed can predict conservatively the bending moment capacity of H-section flexural members with local buckling.