Advanced Materials Research Vols. 690-693

Abstract: A review of the recent study on w-Sc_xAI_1-XN alloy is presented in this paper. w-Sc_xAI_1-XN alloy is a high temperature piezoelectric material, which exhibits a good balance between high maximum use temperature and large piezoelectricity. The experiment results have shown the piezoelectric modulus d₃₃ for Sc_xAI_1-XN with x=0.43 reached up to 27.6pCN^-1, which is at least 400-500% larger than AIN. This piezoelectric alloy thin film material can be grown on various substratesCe.g. silicon (001), AI₂O₃ (0001), MgO (111), TiN(111), etc.Cby dual radio frequency magnetron reactive co-sputtering system. The origin of the anomalous piezoelectric response based on quantum mechanical calculation and the dielectric properties based on experimental measurement in w-Sc_xAI_1-XN alloy have been also reviewed in this paper.

Abstract: NiZn-ferrite thin films were deposited onto silicon and glass substrates by radio frequency magnetron sputtering at room temperature. The effects of the relative oxygen flow ratio on the structure and magnetic properties of the thin films were investigated. The study results reveal that the films deposited under higher relative oxygen flow ratio show a better crystallinity. Static magnetic measurement results indicated that the saturation magnetization of the films was greatly affected by the crystallinity, grain dimension, and cation distribution in the NiZn-ferrite films. The NiZn-ferrite thin films with a maximum saturation magnetization of 151 emucm^-3, which is about 40% of the bulk NiZn ferrite, was obtained under relative oxygen flow ratio of 60%.

Abstract: Zinc selenide (ZnSe) quantum dot thin films have been deposited onto microscope glass through chemical bath deposition both from original amonia free alkaline precursors and modified precursors with the adding of sodium citrate as complexing agents. The growth and optical properties of samples from original and modified precursors have been investigated. Its shown that the samples obtained with sodium citrate precursors are uniform and with stable index of refraction. And with the adding of sodium citrate, there is an increase in transmittance.

Abstract: In this paper, a series of bending cyclic tests under stress controlled were conducted at room temperature on Zircaloy-4 (Zr-4) to investigate its bending ratcheting behavior. The effects of mean stress and stress amplitude on the bending ratcheting behavior were experimentally studied, respectively. The experimental results show that the ratcheting strain of the material is very sensitive to mean stress and stress amplitude. It can be concluded that ratcheting strain level increases with increasing mean stress and stress amplitude.

Abstract: Low cycle and high cycle fatigue tests of 35CrMo steel at different pretorsional angles were conducted and cyclic hardening and softening curves, hysteresis loops and S-N curves were obtained of 35CrMo steel after the torsional prestrain. Scanning electron microscopy (SEM) analysis was also made of the fatigue fracture. The results show that: 35CrMo steel features obvious cyclic softening with basically the same law and degree at different torsional prestrains. The area surrounded by the stress-strain hysteresis loop decreases with the increment of the pretorsional angle; the torsional prestain reduces the fatigue life of the materials.

Abstract: First-principles calculations are performed to investigate the Young’s modulus, bulk modulus, shear modulus and Poisson’s ratio of hexagonal phase ScA_x (A=H, He), where x=0, 0.0313, 0.125 and 0.25, represent the ratio of interstitial atoms A (A=H, He) to Sc atoms. The influences of hydrogen concentrations and helium concentrations on elastic modulus and Poisson’s ratio of ScA_x (A=H, He) have been studied. The results indicate that hydrogen and helium have different effects on the elastic modulus of hexagonal phase scandium. The change mechanism of the Poisson’s ratio with the variation of the x ranging from 0 to 0.25 has also been studied in hexagonal phase ScA_x (A=H, He). In addition, the changes in the charge densities of ScA_x due to the presence of hydrogen and helium have been calculated.

Abstract: Fatigue is the most common failure mechanisms in many engineering structures with inherent defects under variable amplitude loading, Such as lifting structures, airplanes, bridges and so on have to endure for a long term cycle loadings in the actual service. For such structures, fatigue life is dominantly predicted by crack growth analysis, using the stress intensity factor range. In this paper, an improved extend finite element method is proposed for stress intensity factor calculation, which can overcome the limitation of the level set method in judge the element types. Numerical experiment is provided to demonstrate the utility and robustness of the proposed method.

Abstract: Model test is one of the most effective methods to understand the mechanical behavior for complicated bridge structures. In this paper, the model test and the construction technology are described, and analysis specialized in the tower column and the cross beam are done based on the finite element analysis software ANSYS, then compare with the result of the model test. It is proved by both the theory and the test that the design of the tower is safe and reasonable.

Abstract: The mechanical properties of granite experiencing high temperatures under uniaxial compression condition were simulated in this paper. Numerically simulated stress-strain curve, peak stress, peak strain and the tangent elastic modulus were compared with the corresponding physical tests. Simulated results agree well with physical tests results, it is shown that Abaqus is suitable for the analysis of the temperature effect on rock fracture.

Abstract: The test on fatigue crack growth rate of ADB610 steel is completed. The standard compact tension specimen is loaded by cyclic loading, whose stress ratio is constant at a value of R=0.1. Crack growth rates in the form of Paris formula at different survival levels are obtained by using three methods. After a simple comparison it is clear that crack growth rates obtained by three methods are generally same and the method based on (da/dN, delta K) has better effects on data analysis.