Advanced Materials Research Vols. 160-162

Abstract: An allowable design method is presented, along with its experimental validation, to obtain engineering-standard design allowable for fatigue life evaluation of advanced composites. A small sample test method for stress/life curves was established to overcome these issues based on the regression analysis theory. Statistically-based design values, such as the B-basis value, the Anderson-Darling test statistic and the observed significance level, were obtained depends on the characteristics of the composite material test data. For evaluation of the fatigue life of advanced composites, the S-N curve-fitting parameters are obtained using the linear heteroscedastic regression method based on experimental data. Another advantage of this method is that all the test data at different stress levels can be analyzed coinstantaneously, which greatly saved the experimental efforts and specimen for confidential statistical results. Finally, an experimental test program has been conducted on typical laminate composites to generate statistically meaningful data for durability design. The numerical results show that the proposed method can be used as a guide to obtaining design allowable for durability analysis of advanced composite structures.

Abstract: The effects of nano-particles (CaCO3, SiO2 and organic modified montmorillonite (OMMT) on the suppression of DOP migration from PVC matrix and mechanical properties of PVC composites were evaluated. The results indicated that the three kinds of nano-particles could improve the ability of anti-migration of DOP in flexible PVC. A certain content of nano-particle could decrease the migration rate of DOP. The addition of 5 phr SiO2 decreased the extraction rate of DOP to 15.6%, and SiO2-5/PVC composite film possessed superior anti-extraction property. The introduction of 5 phr OMMT reduced the volatilization of DOP to 0.067%, and OMMT-5/PVC exhibited the lowest volatilization of DOP. Inorganic nano-particles with high surface energy were easy to aggregate, and the influences of aggregation on the properties of composites were clearly detrimental, which results in a drastic decrease of polymer anti-migration and mechanical performance.

Abstract: The effect of ammonia etching (AE) pretreatment on the formation of catalyst nanoparticles from homogeneous Ni films deposited by sputtering coater for carbon nanotubes (CNTs) growth is investigated systematically. It is shown that the size and distribution of the nanoparticles depend mainly on the AE pretreatment temperature and time. It is observed that Ni catalyst film is agglomerated by AE pretreatment, resulting in the formation of Ni nanoparticles. We have found a critical temperature and time for AE pretreatment processes to obtain catalyst nanoparticles with the appropriate size and high density. The densely aligned CNTs were successfully grown at 800-850 °C on such nanoparticles by thermal Chemical vapor deposition (CVD).

Abstract: The effects of heat treatment on morphology of primary α and hardness of B-refined Al-7 wt% Si alloy are investigated. In addition, the optimum heat treatment procedure is also determined. It is shown that, at 450°C with different holding time from 3h to 12h, morphology of primary α phase is converted from irregular dendrite to granular homogeneous equiaxed grains then to rosette structure. The primary α phase is gradually converted from dendrite into the rosette dendrite and then into particle crystal with increasing of temperature by holding 8h at 300~540°C. One can find fine and uniform distributed particle α phase at 400°C or 450°C. However, the primary α phase has changed into large and irregular shape when the temperature increases up to 450°C. The orthogonal analysis shows that the optimum heat treatment parameters are 540±10°Cand 6h.

Abstract: The fabrication of the single-negative (SNG) metamaterials involving the tunable SNG metamaterials based on coplanar waveguide is investigated. First, the SNG metamaterials are fabricated by periodically loading lumped-element series capacitors and shunt inductors on coplanar waveguide. Moreover, based on it, the tunable SNG metamaterials in which the center frequency and frequency region of the SNG gap can be tuned conveniently is also realized through loading the varactor diodes in place of the lumped-element capacitors.

Abstract: Feldspar-alumina dental ceramics were produced by impressed sintering method and characterized by X-ray diffraction and scanning electron microscope techniques. The machinability of the obtained alumina ceramics was evaluated by grinding capacity in the simulative grinding experiment. The results show that an appropriate amount of feldspar additive can reduce the sinter temperature and improve density, bending strength and machinability of alumina dental ceramics. Under 10 wt% feldspar and 1450 °C sinter temperature, the relative density and bending strength of ceramic reached 93.62% and 235MPa, respectively.

Abstract: Three different CeO2 sphere nanomaterials (hollow sphere, flowerlike sphere, spherical cluster) were controllably synthesized by carbon sphere template method, hydrothermal and solvothermal method respectively. Then 2.5 wt% Au was doped on the supports by the deposition precipitation method and Au/CeO2 catalysts with three different morphologies were obtained. Composition, morphology and structure of these catalysts were characterized by the techniques of XRD, Raman, TPR, SEM and TEM, and the activity for CO oxidation of the catalysts was investigated. The catalytic test results indicated that the addition of Au could remarkably improve catalytic performance on CO oxidation. The activities of the three catalysts differ largely, the flowerlike Au/CeO2 catalyst had the highest activity for CO oxidation and its T100% was 29°C. The mechanism for the different activity of the catalysts was investigated. H2-TPR result indicated flowerlike had a more intensive peak at 125°C than others and it implied more reducible Au species in this case, that plays a vital role in the CO oxidation.

Abstract: The evolution of microstructure and the mechanical response of ultrapure aluminum subjected to plastic deformation using plate-impact loading was investigated. For the High Purity Aluminum (99.999%), disk sample was shock impacted by a light gun. Observations by transmission electron microscopy reveal that the inside of the early voids consists of nanometer aluminum; it is proposed that they are the result of recrystallization occurring during localization. And some texture may come from the high temperature annealing the secondary grain crystallization behavior and crystallization when the tensile stress effect. This discovery is helpful to the study on the mechanism during the early stage of void nucleation and growth which produced by tensile fracture.

Abstract: The modular design principle is that much more products are composed by fewness module, and the products should be stable, and have high precision, simple structure, and also lower cost based on the customer requirements, therefore, dividing and treating the level, size and number of the module scientifically and reasonably is an important guarantee for the successful modular design. And now the modular design based on the different thought, for the marine work-over rig, and scientifically rational module partition scheme are offered based on the principle and theory of the module design and module division, which has important significance for the design and development of the module rig.

Abstract: In order to solve spring-back problem of the stamping forming process, A method for stamping forming and spring-back process simulation of automotive panel by finite element technologies was proposed. The solid model of automobile right side strengthening panel was created in UG software and transmitted to Dynaform. The stamping forming and spring-back process simulation were realized by using Dynaform. The distribution of strain, the variety of the sheet thickness and the spring-back were analyzed. The maximum stress or strain, the minimum thickness and the maximum spring-back were obtained. The simulation results can reflect the real stamping forming of the strengthening panel, and forecast the possibly spring-back value in stamping process. This research can optimize the stamping process and provide strong references for the design of the automotive panel die.