Advanced Materials Research Vols. 97-101

Abstract: Least squares support vector machines (LS-SVM) were developed for the analysis and prediction of the relationship between the cutting conditions and the corresponding fractal parameters of machined surfaces in face milling operation. These models can help manufacturers to determine the appropriate cutting conditions, in order to achieve specific surface roughness profile geometry, and hence achieve the desired tribological performance (e.g. friction and wear) between the contacting surfaces. The input parameters of the LS-SVM are the cutting parameters: rotational speed, feed, depth of milling. The output parameters of the LS-SVM are the corresponding calculated fractal parameters: fractal dimension D and vertical scaling parameter G. The LS-SVM were utilized successfully for training and predicting the fractal parameters D and G in face milling operations. Moreover, Weierstrass-Mandelbrot（W–M ）fractal function was integrated with the LS-SVM in order to generate an artificially fractal predicted profiles at different milling conditions. The predicted profiles were found statistically similar to the actual measured profiles of test specimens and there is a relationship between the scale-independent fractal coefficients(D and G).

Abstract: Crack propagation in practical engineering problems is often of mixed-mode type. The analysis of mixed-mode I–II crack initiation angles under different loading conditions is presented using stress invariants criteria. Where I1 and I2 are the first and the second stress invariants, IP-criterion postulates that crack will propagate along the direction defined by a maximum value of IP along the elastic–plastic boundary defined by von Mises. The mixed-mode I-II crack initiation angle is predicted successfully and is agree well with experimental data.

Abstract: Zn1-xCuxO films were prepared by radio frequency (RF) magnetron sputtering method. The wurtzite ZnO crystal can be well retained up to a Cu composition of 10% and doped Cu ions substituted into Zn sites of ZnO host lattice. All the samples show high transparency over the wavelengths from 400 to 1000 nm. The room temperature (RT) resistivity shows an increase in Mn doping samples, which indicates that the doped element is at the status of deep donor levels. The decrease in the bandgap in Cu doped ZnO films rather than in pure ZnO film indicates that there are impurity bands created by Cu 3d orbital or strong d-p coupling between Cu and O in our samples. In addition, photoluminescence (PL) spectra show UV emission at ~3.19 eV shifts to lower energy side with Cu doping, indicating the possibility of band-gap engineering in Zn1-xCuxO films.

Abstract: The reactionary trend of the triethanolamine and cobalt in cemented carbide and the mechanism of cobalt leaching have been investigated by soaking experiments, friction experiments and electrochemical gaging experiments. The experimental results reveal that triethanolamine is prone to form coordination compound with cobalt ion .The amount of cobalt’s element leaching from cemented carbide is added up with the increase of time and triethanolamine concentration. So when using cemented carbide cutting tool, the water-based cutting fluid containing triethanolamine addictive should be avoided.

Abstract: The stresses, strains, and deformations produced by repeated, two-dimensional non-steady state rolling-sliding contact were analyzed using an elastic-plastic finite element model. An advanced cyclic plasticity model was used. The non-steady state rolling contact was restricted to a harmonic variation of the normal Herztian contact pressure. Repeated rolling and sliding were simulated by multiple translations of a set of varying normal and tangential surface tractions across an elastic-plastic semi-infinite half space. The non-steady state loading considered results in a wavy contact surface profile. The surface displacements and wave depth of the wavy deformation increase with increasing rolling passes, but the increases in wave depth per rolling pass (ratchetting rate) decay. The residual stresses and strains near the wave trough of the residual wavy deformation are higher than those near the wave crest. The results are in agreement with the experimental observations. The tangential force has a greater influence on the residual strains than on the residual stresses.

Abstract: Fe-Cr binary model alloys (Cr: 25 wt %) with additions of 0.09 wt% lanthanum were subjected to cyclic oxidation experiments at 700oC. All model alloys were exposed in five different gases; Ar-20O2, Ar-20O2-5H2O, Ar-5O2-20H2O, Ar-10H2-5H2O (pO2 = 3.64 x 10-22 atm) and Ar-10H2-20H2O (pO2 = 7.37 x 10-21 atm) all in volume %. Very low weight gains were observed in all gases of Fe-25Cr-0.09La. However, breakaway oxidation occurred on La-free alloy experienced increased weight gain in Ar-5O2-20H2O due to formation of iron-rich oxide. The addition of La (<0.1 wt%) to the Fe25Cr retarded the growth of iron-rich oxide in Ar-5O2-20H2O.

Abstract: According to the current situation of acicular chip and high-frequency chattering of the NC rotary table while gear milling, rigidity and damping performances of the table were analyzed and the damping program of Coulomb friction was bring up. Online test of the gear milling cutting force can be used to establish dynamic model of circumferential vibration of the table with Coulomb friction. Then mechanism of restraining gear cutting chatter by damping of Coulomb friction and acicular chip generating mechanism were exposed. Furthermore, relationship between backlash and rotary rigidity of the table was also analyzed. A kind of floating apparatus with friction damping was designed to optimize circumferential damping of the table by adjusting Coulomb friction force, which reduces the influence of high-frequency chattering on gear milling. As a result, efficiency of gear milling was increased 1.5 times and the noise was reduced from 105dB to 91dB.

Abstract: The problem of orthotropic composite materials semi-infinite interfacial crack was studied, by constructing new stress functions and employing the method of composite material complex. In the case that the secular equations’ discriminates the and theoretical solutions to the stress fields and the displacement fields near semi-infinite interface crack tip without oscillation and inter-embedding between the interfaces of the crack are obtained, a comparison with finite element example was done to verify the correction of theoretical solution.

Abstract: External bonding of fibre reinforced polymer (FRP) composites has become a common way for strengthening concrete members. The performance of the interface between FRP and concrete is one of the key factors affecting the behaviour of the strengthened structure. For this FRP-concrete structure, there are two types of debonding failures: plate end debonding and intermediate crack (IC) induced debonding. This paper presents an analytical solution for the second type debonding failures in FRP-concrete bonded joint model where the FRP plate is subject to tension at both ends. Both the strengthened beam and strengthening FRP are modeled as two linearly elastic Euler–Bernoulli beams bonded together through a thin adhesive layer. The debonding process of the FRP–concrete interface is discussed in detail, and closed-form solutions of bond slip, interface shear stress, and axial force of FRP in different stages are obtained. Parametric studies are further carried out to investigate the effect of the thickness of adhesive layer on the bond behavior of FRP–concrete interface.

Abstract: Ni-Y2O3 nanocomposite coating was electrodeposited from a nickel sulfamate solution containing Y2O3 particles and ultrasonic was applied during the process of the electrodeposition. The surface morphology and microstructure of the composite coatings were analyzed by a scanning electronic microscope (SEM) and a high-resolution transmission electron microscope (HRTEM). The corrosion resistence of the coatings was evaluated in the solution of 10 wt.% HCl aqueous solution. The results indicate that the Ni-Y2O3 nanocomposite coating shows a refined crystal grain and improved corrosion resistance compared with pure Ni coating. The Ni-Y2O3 nanocomposite coating prepared under ultrasonic condition exhibits a superior corrosion resistance due to the formation of denser structure and finer-grain scale.