Study on lamellar tearing generated by corner joint welding in box column of ultrathick plate

Abstract

In an attempt to reduce the risk of lamellar tearing during welding of ultrathick plates, the present study has evaluated the susceptibility to lamellar tearing of steel structures in relation to welding stress rather than metallurgical properties, and eventually attempted to determine the optimum groove shape and welding procedure by computer simulation based on the finite element method. Based on the simulation, it has been identified that controlling the shape of the deposited weld metal in the anticipated position of the occurrence of lamellar tearing is the most favourable method of preventing lamellar tearing by minimising welding residual stress and strain. Owing to the difference in weld deposited area, the cooling rate for the partial penetration condition is more rapid than for full penetration. Furthermore, in terms of welding residual stress, the full penetration condition is preferable to the partial penetration condition.     

Theoretical analysis of SAW propagation characteristics in (100) oriented AlN/diamond structure

In this study, the finite element method is employed to calculate SAW characteristics in (100) AlN/diamond based structures with different electrical interfaces; i.e., IDT/ AlN/diamond, AlN/IDT/diamond, IDT/AlN/thin metal film/ diamond, and thin metal film/AlN/IDT/diamond. The effects of Cu and Al electrodes as well as the thickness of electrode on phase velocity, coupling coefficient, and reflectivity of SAWs are illustrated. Propagation characteristics of SAWs in (002) AlN/diamond-based structures are also presented for comparison. Simulation results show that to retain a large reflectivity for the design of RF filters and duplexers, the Cu IDT/(100) AlN/diamond structure possesses the highest phase velocity and largest coupling coefficient at the smallest AlN film thickness- to-wavelength ratio.     

Cell adhesion on modified polyethylene

Polyethylene (PE) was irradiated with 10 and 63 keV Ar⁺ ions to fluences of 1 × 10¹⁷ to 3 × 10¹⁹ m^–2 and then it was grafted with aminoacid (alanine). The changes of surface polarity, electrical conductivity, and oxygen concentration were examined on pristine, as-irradiated, and irradiated-grafted PE. The in vitro adhesion of mice fibroblasts on the modified PE was evaluated 24 hours after inoculation. It was proved that for the PE irradiated at 10 keV ion energy, the presence of chemically bound alanine increases cell adhesion and its homogenity. For PE irradiated with 63 keV ions, however, the alanine grafting leads to a reduction of the number of adhering cells. It was found that a rising surface polarity increases cell adhesion, but when its value is too high the cell adhesion starts to decrease. No correlation between electrical conductivity and cell adhesion was observed. In general, higher cell adhesion is observed on modified PE in comparison with pristine one.     

Energy transfer mechanisms in LMR rod bundles under mixed convection conditions

The energy transfer mechanisms operative under mixed convection conditions in heated rod arrays are identified. The relative importance of these various mechanisms of energy transfer has been assessed and is presented in regime maps which allow the designer and experimentalist to rapidly assess the characteristics of an operating regime and the capabilities needed in an analysis tool to treat such a regime. Azimuthal heater rod conduction is important for boron nitride insulated rods typically utilized in out-of-pile sodium tests. Therefore the comparison of energy transfer mechanisms necessitated the development of a correlation for azimuthal heater rod conduction. This correlation has been derived from a physical model formulated to describe this conduction effect. The proposed correlation has been tested against experimental data from out-of-pile tests and has been proven accurate for predicting the azimuthal heater rod conduction effect in LMR rod bundles.     

Studies on capillary waves generated by light pulses of Nd3+ - glass laser with ultrasonic Q-switch

In the paper some results of the studies on parameters of capillary waves generated in 18H2N4WA type steel by means of light pulses of Nd³⁺ - glass laser with ultrasonic modulation of Q-factor of the optical resonator have been presented.     

De-Mail und Bürgerportale

Trotz der wachsenden Bedeutung des Internet für die Kommunikation zwischen Bürgern, Beh?rden und Unternehmen sind die Sicherheit, Vertraulichkeit und Rechtsverbindlichkeit des elektronischen Rechts- und Gesch?ftsverkehrs bislang nicht gew?hrleistet. Die geplanten Bürgerportale sind ein wichtiges Instrument zur L?sung der bestehenden Probleme.     

Microstructural evolution and mechanical properties of Cr-Ru alloys

In an effort to enhance ductility and strength of Cr-base alloys, a series of Cr-Ru alloys with Ru contents ranging from 3 to 30 at. pct were made to study their microstructure evolution and mechanical properties. The microstructure of the alloys with 6 to 20 at. pct Ru showed signs of a eutectic structure. However, no corresponding eutectic reaction is indicated in the published Cr-Ru phase diagram. The yield strength of the Cr-Ru alloys increased with increasing Ru content at both room temperature and 1200 °C. The tensile ductility of Cr-3 at. pct Ru is about 1.5 pct at room temperature, while the alloys containing 6 at. pct or more Ru showed zero tensile elongation. The deformation mechanisms of the Cr-Ru alloys are discussed in terms of the microstructure and fracture behavior. This article is based on a presentation made in the symposium entitled “Beyond Nickel-Base Superalloys,” which took place March 14–18, 2004, at the TMS Spring meeting in Charlotte, NC, under the auspices of the SMD-Corrosion and Environmental Effects Committee, the SMD-High Temperature Alloys Committee, the SMD-Mechanical Behavior of Materials Committee, and the SMD-Refractory Metals Committee.     

Identification of airway characteristics using the input impedance

To understand how the input impedance determined at the throat correlates with changes in the dynamic characteristics of the airways, a simplified 5-lobe model is developed and simulated. The model takes into account some realistic conditions such as varying cross-sectional areas, flexible wall properties and branching. The lobe terminal impedances are implemented in the model to predict the input impedance at the throat. The effects of airway constrictions and wall elastance variations on this impedance are determined for a range of frequencies. It is concluded that the developed model is capable of predicting various physiological changes in the airway passages.