Advanced Materials Research Vols. 399-401

Abstract: First-principles calculation based on the density functional theory in the generalized gradient approximation was adopted to systematically investigate the α-Al₂O₃(0001) surface structure and the adsorption of H atom on the α-Al₂O₃(0001) surface. The calculations show that the O atop site is the energetically most favorable adsorption site at low coverage: at the H coverage of 1/6 ML (monolayer), the adsorption energy reaches up to7.61eV; in the regime of higher H coverages, the H atoms prefer to form atom cluster on the α-Al₂O₃(0001) surface, and the adsorption energy on the α-Al₂O₃(0001) with a pre-adsorbed H atom gets smaller, which illustrates that α-Al₂O₃ that can prevent the penetration of hydrogen. With the increase of H coverage, the dipole moment reduces, which leads to a large decrease in the work function.

Abstract: Abstract:TiB₂/Al composites were prepared by the melt in situ reaction fabrication using Al-3B master alloy and Ti powder as the reactive materials. The phase composition and the microstructure of the as-prepared composites were investigated by XRD, SEM. The results indicate that the reinforcements are TiB2 and a small amount of Al₃Ti. TiB₂ particles are in the shape of irregular polygon or rectangle, and its size is 0.5-2μm. Compared with the matrix material, the ultimate tensile strength, microhardness of as-prapred composites increase by 51%, 68.8%, 85.2%, and 33.4%, 43.8%, 55%, respectively. However, the elongation decrease with the volume fraction of the reinforcements increased.

Abstract: The process of injection mould design and manufacture was introduced by taking the cover as an example. Firstly, the 3D model of the part and the injection mould structure were designed based on SolidWorks software. Secondly, the injection molding progress was analyzed and simulated based on Moldflow software. Finally, the toolpaths of cavity and core were designed based on MasterCAM software, and its manufacture process and numerical control programming was simulated. The period of product development was shortened effectively and the quality of design and manufacture was improved by CAD/CAE/CAM integrated technology.

Abstract: Plain fatigue and fretting fatigue tests of sensitized SUS304 stainless steel under pressurized hot water at 7.3MPa and 288°C have been carried out. Fatigue strengths for both fatigue tests almost coincided. Fretting contact could nucleate small SCC cracks near the contact edge in the direction perpendicular to cyclic loading. High R–ratio reduced fatigue strength due to longer exposure time to corrosive environment at high mean stress. From the constant load SCC tests of the specimen with small SCC pre–crack induced by fretting contact, it was found that the threshold stress intensity factor for growth of small SCC precrack was 4.1MPa·m^1/2, which was significantly lower than that for long crack (10MPa·m^1/2).

Abstract: By using a new type of photo-acoustic tomography spectroscopy with non-damage and weak signals detection, the normalized photo-acoustic tomography spectroscopy (PAS-CT) and optical absorption characteristic of the green and yellow leaves of the cabbage are measured. The results show that: the leaves of the cabbage could get different levels of photo-acoustic spectroscopy from different chopping frequency. The chloroplast number in the yellow leaves was less than that in the green leaves, so the photosynthesis in the yellow leaves was significantly weakened compared with the green leaves. The more the chloroplast number in the cabbage leaves were, the stronger the photosynthesis was and the higher the photosynthetic efficiency was. The chopping frequency of 24Hz could activate more chloroplasts than 34Hz and improve the photosynthetic efficiency of the cabbage leaves. What’s more, it could improve the yield of cabbage. Photo-acoustic tomography spectroscopy is a new way of studying photosynthesis. It has a bright and far-reaching future.

Abstract: Based on the finite element analysis, the general mechanical property tests and the CTOD (crack tip opening displacement) test of the penstock in the third deviated hole, the GB/T19624-2004, that is the criterion of safety assessment for in-service pressure vessels containing defects suggested by China, is applied to assess the five weld defects in the penstock, which experienced the failure of the pressure test. The assessment results indicate that 1# defect and 5# defect could be accepted, while the other defects should be repaired. According to the assessment results, the defects over criterion in the penstock must be repaired. After the penstock was repaired, it was checked by the ultrasonic flaw detection again. And the results indicate that all weld joints including circumferential and longitudinal weld joints in the penstock around the pipe close in the third deviated hole are acceptable, what provides a scientific basis for the second pressure test and the safe operation of the High head hydropower station.

Abstract: This paper presents an optimization method for optimal engineering structure design. An interface procedure is essentially developed to combine the intelligent optimization algorithm and computer aided engineering (CAE) code. An optimization example is carried out to minimize the interlaminar normal stress of a laminate which affect the delamination failure of a laminate via arranging the stacking sequence. The analytical solution is calculated to validate the accuracy of optimization results.

Abstract: Recrystallization law was investigated at different annealing processes. The results showed that the annealing temperature was a main effect factor on the properties of Ti-IF steel. Nominal recrystallization temperature of the samples was evaluated as 620 °C. Simulated batch annealing was performed by two-stage heating. Determined recrystallization temperature was 660 °C, the recrystallization of samples heated at 660 °C was completed in 68min. For 800 °C, the equiaxial recrystallized grains were obtained. Simulated continuous annealing by rapidly heating to different temperatures, samples were held for 100s and then cooled in air. Recrystallization nucleation was not observed until 660 °C. The occurrence of secondary recrystallization was observed at 900 °C.

Abstract: Three dimension temperature fields and stress-strain fields of the 6110-type diesel engine piston were analyzed by using the program ANSYS. The simulating tests of crack propagation under high temperature low cycle fatigue were carried out with pre-crack notched specimens. According to the theory of high temperature strength and fracture, the equivalent J-integral range ΔJf were induced to predict the surplus fatigue life of diesel engine piston. It was concluded that this approach is suitable and provides valuable reference for designers of diesel engine.

Abstract: Abstract: Fe₄₁Co₇Cr₁₅Mo₁₄C₁₅B₆Y₂ (at%) bulk metallic glass was prepared by copper mold casting. Nano-crystalline Fe₄₁Co₇Cr₁₅Mo₁₄C₁₅B₆Y₂ alloys were obtained by annealing. The influence of heat treatment at different temperatures in the alloy microstructure was identified by X-ray diffraction (XRD), and a comparative study of the electrochemical corrosion behaviors of amorphous and amorphous/nanocrystalline alloys was performed by potentiodynamic polarization method and electrochemical impedance spectroscopy (EIS) in 1.5M HCI solution, and the corrosion morphologies of the samples were observed by scanning electron microscopy (SEM). The results show amorphous alloy plays excellent anti-corrosion ability than that of the heat-treated samples, and the anti-corrosion ability of amorphous/nanocrystalline alloys decrease with the increasing of heat-treatment temperature.