Advanced Materials Research Vols. 538-541

Abstract: A kind of white massive microstructure in weld joint of P91 steel was first discussed by OM, SEM and EDS analysis. Results indicated that it is a kind of substance with low melting temperature other than the conventional delta ferrite. It contains high content of Cr due to improper choice of weld electrode and weld heat treatment. The existance of the abnormal microstructure will result in cracking under large stress for poor toughness. Solutions are suggested to prevent the formation of the white massive microstructure.

Abstract: Laser-MAG hybrid, GMAW and SAW welding experiment were carried out for the new low CE 600MPa grade steel, and hardness survey on the welded joints was performed. Laser-MAG hybrid welding has the highest speed with the least filling weld metal, and its joint exhibits almost no softening with higher harness in weld than base metal. SAW welding has high efficiency but most significant softening effect on the HAZ. For SAW, on the HAZ 4 ~ 5 mm apart from the fusion line peak hardness exists. For GMAW, on the HAZ about 2mm away from the fusion line a softened zone appears, but the softening degree is lower than for SAW. The results showed that the hardness of the welded joint of this type of steel seems much subjected to the welding heat input.

Abstract: In recent years, super duplex stainless steel has been widely used in offshore platform for its excellent corrosion resistance. The key point of welding super duplex stainless steel is to ensure the phase ratio of welded joints. In this paper, the weldability, welding method, welding material, groove of SAF2507 were introduced. Then the test content of welding procedure qualification was described.

Abstract: By method of TIG, and under certain welding craft conditions,1Cr18Ni9Ti and 2Cr13 were welded. By (ZEISS) OM,SEM,the microstructure of two kinds of 2Cr13 and 1Cr18Ni9Ti welding joints were observed and analyzed, Through seawater immersion test, polarization curves and AC impedance spectroscopy of 1Cr18Ni9Ti and 2Cr13 welding joints were obtained. The results show that 2Cr13 and 1Cr18Ni9Ti welded joints is typical columnar crystal, the microstructure is lath martensite + austenite + carbide; polarization curves and AC impedance spectroscopy show that corrosion resistance of welding joint from strong to weak is: austenite base metal>HAZ near austenite>welded joint>HAZ near martensite>martensite base metal; corrosion resistance of welded joint is between martensite base metal and austenite base metal.

Abstract: Brazing Mo/Mo and Mo/porous W using 60Mo-40Ru in weight percent braze alloy are evaluated in the experiment. Sound Mo/60Mo-40Ru/Mo joint is obtained from brazing at 1970 and 2000 °C for 600 s, respectively. The brazed joints are comprised of σ and Mo-rich phases. For Mo/60Mo-40Ru/porous W joint, sound bonding is achieved only from brazing at 2000 °C for 600 s, and similar microstructure of the joint is obtained. The 60Mo-40Ru braze alloy shows potential in bonding refractory metal(s) for high-temperature applications.

Abstract: This paper, conducted through the literature reviews of safety culture models and safety culture dimensions and the application of the management mechanism of the Taiwan Occupational Safety and Health Management System (TOSHMS), proposes a new Omnidirectional Safety Culture Model (OSCM). Four railway companies in Taiwan served as the questionnaire survey subject, and the safety culture of the current railway industry was profoundly investigated. Furthermore, utilizing AMOS analysis software, the thesis verifies the hypotheses by inspecting the structure model with Structural Equation Modeling (SEM).It was indicated in the research that the railway employees’ evaluation of safety culture Significant differences are noted between age and most safety culture dimensions other than “Safety Encouragement and Punishment,” “Performance Measurement,” and “Procurement Management.” In addition, job satisfaction, working environment satisfaction, safety and health policy satisfaction, working efficiency, and possibilities of workplace injuries bear obvious relevance to many safety culture dimensions. The goodness of fit of four safety factors and eighteen safety culture dimensions are confirmed to be acceptable, considering the evaluation result of safety culture structure on all models and synthesizing overall fit indexes. It is ascertained that this model fits better and the result is effective.

Abstract: The mortar cube specimens and anchorage specimens are corroded under the sulfate solution and dry-wet cycle method is used to accelerate the corrosion process. The compressive strength of cub specimens and bond strength of anchorage specimens of different corrosion time are tested and the corresponding relationship between mortar corrosion degree and mortar anchorage strength is established。The test result shows that: the curve that strength of mortar specimens changes with corrosion time fitted with quadratic curve significantly, and the high water cement ratio is , the faster the strength loss. After mortar corrosion, the bond strength decreases with corrosion time linearly, the high water cement ration is , the low initial bond strength the specimens has, and the little bond strength loss at the same corrosion time. The changes of bond strength with coefficient of compressive corrosion resistance coefficient is approximately lineally.

Abstract: Abstracts: Fused deposition modeling (FDM), a representative prototyping technology with no use of toxic materials, has been widely used in offices. The reason of interlayer stress and warpage deformation are analyzed in this paper. Under certain conditions, the calculating formula of interlayer stress and the stress-distributing diagram in cut planes are provided, and the mathematical model for warpage deformation calculation is also established. Besides, the influence of the various process parameters on the deformation, such as the number of deposition layers, scanning line length, chamber temperature, and layer thickness, is quantitatively analyzed with measurements provided to minimize deformation.

Abstract: According to the concept of sustainable development, the environmental load of a building must be evaluated throughout its life cycle, from design to construction, maintenance or repair, demolition, and rubble disposal. Therefore, from a holistic point of view, sustainable construction means designing a reinforced concrete structure with proper durability during a specified service life. This paper discusses the effect of partial and full replacement of natural aggregates by recycled concrete aggregates (RCA) in a fly ash concrete. Engineering properties and durability performance have been examined for mixtures designed with various proportions of the RCA by mass. Results obtained showed that the addition of RCA lowers concrete performance, but the combined use of RCA and fly ash could allow to achieve adequate engineering properties and durability.

Abstract: Using finite element method, models of different element mesh density for the center hole in flat plate were established according to one actual steel plate with central circular hole. The stress concentration coefficients of these models were calculated by means of numerical method. Then the calculated results were compared with the theoretical solution results of Elastic Mechanics. And it was analyzed subsequently that the influences which were caused by different element mesh density on the stress concentration coefficients around the hole in flat plate. The relationship between the element mesh density and the stress concentration coefficients around the hole in flat plate was proposed finally. Results show that the element mesh density for calculation affects the stress concentration coefficients around the hole in flat plate significantly, but the influence is few when the mesh density increases to a certain extent.