Advanced Materials Research Vols. 631-632

Abstract: The polymethymethacrylate (PMMA) plate was adopted as the test samples. The effects of impact angle, impact velocity, sand size on the erosion wear of the PMMA plates were experimentally investigated. The erosion mechanisms were also analyzed. The results showed that, the erosion volume increased nonlinearly with the increase of impact velocity, the inflection point appeared at around 13 m/s, and then the erosion volume increased rapidly. The erosion volume decreased nonlinearly as the impact angle increased. In our experiments, under the impact angle less than 60°, the smaller sand size could result in higher erosion wear. However, at 90°, the erosion volume by larger sands produced higher erosion. In fact, the erosion mechanism depends on the impact angle, at small impact angles, the main erosion mechanism is micro-cutting, and the erosion mechanism will mainly be impacting fatigue at large impact angles. At the medium impact angles, the erosion mechanism is the combination of the micro-cutting and impacting.

Abstract: Isothermal compression of the TiNiFe shape memory alloy has been carried out on a Gleeble-3500 thermal simulation machine at the deformation temperature ranging from 1023K to 1323K, the strain rate ranging from 0.01s-1 to 10s-1 with total strain of 0.8. On the basis of dynamic material model, the processing map is established with two instability regions and a desirable domain which demonstrate optimum hot working conditions within the experimental parameters. By means of Electron Back Scattering Diffraction, we come to the conclusion that both dynamic recovery and dynamic recrystallization exist in the desirable domain with deformation temperature ranging 1123 K and strain rate 0.1s-1. The uneven deformation exits in the low deformation temperature with high strain rate area, such as 1023 K and10 s-1. And with 1323K and 0.01s-1 strain rate, the recrystallized grains are abnormal grow up.

Abstract: Propagation properties of TE mode for the symmetric waveguide made of left-handed material surrounded by metal substrate- and coat- layers are studied. The guidance conditions of TE mode is deduced by transmission matrix. Using graphical method, different propagation modes and corresponding transverse profiles of electric field are analyzed. It is found that the fundamental mode TE0 does not exists, such waveguide can support surface wave modes. There is a significant effect on transverse profile of order m and so on. This result will play a theoretical guidance for the research of waveguide containing left-handed materials.

Abstract: In order to study dynamic mechanical properties of float glass under blast and ballistic/fragmentation impacts, the curves of stress- strain are obtained in higher ranges by using the modified Split Hopkinson Pressure Bar (SHPB) techniques. Experimental results indicate that float glass is nonlinear elastic-brittle materials, and its dynamic curves of stress-strain are nonlinear and can be divided into three stages: elastic, nonlinear strengthening and stress drop. The dynamic Young’s modulus and the dynamic compressive strength of float glass increase with the increasing of strain rate. Finally, an explanation was given according to principle of energy equilibrium of Griffith.

Abstract: In order to ensure the reliability of the fatigue design, the dispersion of S-N data obtained by ultrasonic fatigue test is usually researched by statistical assessment. Life distribution of fatigue strength of steel materials follows the lognormal distribution or Weibull distribution in general. In this paper, 50 axle steel is researched under symmetric tension and compression loading, and the ultra-high cycle fatigue test data of 50 axle steel are researched by the Weibull distribution, 50 axle steel is described by equation of Basquin, the mode of probability S-N curve are established. The results shows that very high cycle fatigue S-N data of 50 axle steel under symmetric tension and compression loading obey the Weibull distribution. Similar to the S-N curve of 50 axle steel, the probability S-N curves display the characteristic of “the multi-stage type” under the Weibull distribution.

Abstract: With high pressure spraying refinement technology of explosive, we obtain ultrafine powder of TATB and HMX. The middle diameter of them is 746 and 242 , that is to say those two kinds explosives belong to ultrafine explosive. Impact test indicate that the impact sensitivity of ultrafine TATB and HMX is decreasing in some degree. However the shock sensitivity is increased and the increased range is big. The end, we analyze this phenomenon and explain the reason that the ultrafine explosives` sensitivity is different form usual explosive in theory.

Abstract: Sm, Zr doped nanocrystalline TiO2 powers were prepared successfully by a facile ultrasonic assisted sol-gel method. The products were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. X-ray diffraction peaks could be assigned to anatase TiO2, which confirms the crystallinity of the as-prepared samples. The SEM images demonstrated that the crystalinity is formed with spherical aggregates with average diameters ranging from 10 to 20 nm. The photocatalytic activity was studied on the photocatalytic degradation of methyl orange (MO) aqueous solution irradiated with UV-visible light. Under UV-visible light irradiation, the photocatalytic performances of the doped samples were much better than that of pure TiO2, and the co-dopant showed highest. It demonstrated that a strong Sm-Zr synergistic interaction might play a decisive role in driving the excellent photocatalytic performance of TiO2.

Abstract: The ingots were rolled by 550 mills in laboratory to obtain dual-phase steels. The influence of the morphology and distribution of ferrite and martensite on mechanical properties of dual-phase steel was investigated. The results indicated that some amount of acicular ferrite transformed in DP steel is available for decreasing the size and homogenizing the distribution of martensite in ferrite base. Meanwhile, the values of yield strength, tensile strength and impact toughness increases apparently, the value of elongation decreases to 22.5% .

Abstract: The stress-strain curves of 2A16 under different strain rate range (10-3s-1-103s-1) and different temperature range (293K-673K) were obtained through the quasi-static compression test and SHPB test by experimental method. The parameters were determined based on Johnson-Cook model and the strain rate hardening term in them was modified. The results show that 2A16 is a kind of strain rate and sensitive temperature materials. The flow stress increases with strain rate increasing, while that decreases with temperature increasing. The deviation is large between the unamended Johnson-Cook constitutive model and test data, while the modified constitutive model is a good agreement with experimental results. And the study is a preparation for the numerical simulation of 2A16 rivet electromagnetic riveting.

Abstract: Thanks to many industrial benefits that it exhibits, induction heating process is very promising for its potential application in manufacturing production. To understand the industrial context, it is necessary to investigate the process by focusing on simulation and experimental aspects. In fact, this paper presents an original approach able to predict the overtempering zone with analyzing the temperature curves resulting from simulationand the hardness profile achieved by experimental validation. The proposed approach combines experimental validation and numerical simulation applied to 4340 steel disc in order to investigate the overtempering phenomenonand develop a very simplified and practical model able to predict the hardness curve with a fairly good accuracy. The developed model is validated by experimental tests and is used to evaluate the effect of machine parameters on the overtempering.