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A comprehensive experimental programme has been carried out to investigate the local buckling and postbuckling strengths of aluminium alloy I-section stub columns. A total of 15 test specimens made of two heat-treated aluminium alloys (6061-T6 and 6063-T5) were fabricated by extrusion. The material properties were acquired by the tensile coupons cut directly from the extruded cross-sections. The local geometric imperfections in sections were accurately measured prior to the tests. The stub column specimens were tested under axial compression between two fixed end supports, during which the local plate buckling featured visibly for each test specimen before reaching the peak load. The critical local buckling strengths were determined from the measured out-of-plane deflections and surface strains corresponding to the plate elements, which were further compared with the theoretical and analytical values taking into account element interaction and material non-linearity. Based on the obtained experimental postbuckling strengths, the design provisions in current design standards, including the American, Australian/New Zealand, European and Chinese specifications, were all evaluated. It was revealed that the predicted compressive strengths from the four design standards were generally conservative, especially for the cross-sections made of aluminium alloys with pronounced strain hardening properties.

This paper presents twenty-eight stub columns tests on stainless steel built-up sections. The test specimens, including I-sections, square hollow sections (SHS) and rectangular hollow sections (RHS), were fabricated by shielded metal arc welding (SMAW) from hot-rolled plates of nominal thicknesses 6 mm and 10 mm. The twenty-eight stub columns, of two stainless steel alloys (austenitic EN 1.4301 and duplex EN 1.4462), were tested in pure axial compression. Both tensile and compressive material properties were obtained by means of coupon tests in three directions – longitudinal, diagonal and transverse to the rolling direction. Geometric imperfection measurements for each specimen were conducted by means of a calibrated electric guideway, and residual stress distributions in the built-up sections were determined by means of the sectioning method. The test strengths were used to evaluate the design strengths predicted by EN 1993-1-4, the Continuous Strength Method (CSM) and the direct strength method (DSM). It was demonstrated that the predicted strengths from EN 1993-1-4 provisions were generally conservative, while both the CSM and the DSM predicted values were closer to the test strengths.

The structural and magnetic properties of Fe 16 N 2 have been investigated with the help of the GGA+U method. Calculations of the magnetic properties of Fe 16 N 2 indicate that the average magnetic moment of Fe atoms increases in line with the electron correlation effects in Fe 16 N 2 . The differences of magnetic moments for non-equivalent Fe atoms in Fe 16 N 2 mainly result from interstitial N atoms, different degrees of hybridization between non-equivalent Fe atoms and N atoms, and interaction among different d electron orbits of non-equivalent Fe atoms.

This paper presents a detailed investigation into lateral-torsional stability of aluminium extruded I section beams under pure bending. Forty aluminium members of two different alloys 6061-T6 and 6063-T5, representing weak hardening and strong hardening alloys respectively, were tested. Stress–strain relationships were determined by tensile tests with 8 coupons cut from extruded flanges and web. Widths of flanges and lengths of members were herein taken as primary parameters to study lateral-torsional stability of the beams. With rigid lateral-torsional restraint on beam ends, lateral-torsional buckling resistances and load-rotation relationships were obtained by continuous loading. Comparison of numerical predictions with test results indicated that accurate and reliable replication could be achieved by the described finite element (FE) models. By means of measured material behaviour and geometric properties, the corresponding provisions in Eurocode 9 (CEN 2007) and a design method previously proposed by the authors were evaluated by the test results. It was demonstrated that the proposed calculation method could provide cross-section lateral-torsional buckling resistances that are much closer to the test results than design strengths on the basis of the Eurocode 9 provisions are. Therefore, the proposed design method could be an alternative way of predicting the lateral-torsional buckling resistances of aluminium alloy I-beams.

We report room-temperature spin valve effects in Alq3-based vertical organic spin valve (OSV) devices with direct interfaces between Alq3 and the bottom and top ferromagnetic electrodes. In contrast to conventional OSVs, where the top electrode is directly deposited on top of organic layer, we use indirect deposition method. We find this method can significantly suppress the penetration of Co atoms into Alq3 layer during deposition process, which is commonly found in conventional OSVs. The improved Alq3/Co interface is further confirmed by comparing the magnetic moment of depositing Co onto Alq3 and Si substrates by indirect and direct deposition methods. A penetration length of 12.5 nm in direct deposition Co on top of Alq3 is estimated. And the demonstration of room-temperature spin valve effects indicates the improvement of spin injection efficiency at sharp Alq3/Co interface.

In our present work, Ag2S nanowires and Ag2S/CdS heterostructures have been successfully prepared in anhydrous ethanol through a simple solvothermal route. From the transmission electron microscopy (TEM) analysis, it is found that the factors influenced the final product are the concentration of Ag+, reaction temperature, reaction time, and solvent. Ag2S nanowires are formed by complete Ag+ cation exchange. Because of the selectivity for partial cation exchange, the reaction starts preferentially at the ends of the CdS nanowires to produce novel Ag2S/CdS heterostructures. In addition, as the two end facets of wurtzite CdS nanowires are crystallographically nonequivalent, the produced Ag2S/CdS heterostructures are asymmetric.

Abrasive composite bulks consisting of polycrystalline cubic boron nitride (PCBN) grains, Cu-Sn-Ti alloy and graphite particles were sintered at the heating temperature of 920 °C for the dwell time of 30 min. The bending strength of abrasive composite bulks was measured. The interfacial microstructure and the phases were characterized. In addition, the dressing experiment was carried out to detect the self-sharpening behavior of the composite bulks. Results obtained show that the abrasive composite bulks in this investigation give higher bending strength than that of the vitrified abrasive wheels. The compounds of TiN, TiB2were formed and the PCBN grains were embedded firmly. Strong fixing of the bulks to the PCBN grains led to the breakage of the PCBN grains when the abrasive composite bulks fractured. The intergranular fracture mode of the PCBN grains ensured the self-sharpening effect of the grains.

Friction stir lap linear welding is conducted on overlapped AZ31 magnesium plates with different welding tools. Welds are made mainly with the orientation such that the weld retreating side on the upper plate is to be placed under load. Welding tools consist of a concave shoulder and a pin having a cylindrical, or triangular, or pie shape. This work addresses the effects of tool geometry and process condition on lap shear strength of welds. The shape of the hook formed due to upward bending of the plate interface on the retreating side and the strength of friction stir processed material are quantitatively characterized. Compared to the cylindrical tool, the triangular tool effectively suppresses the hook on the retreating side due to enhanced horizontal material flow. This primarily leads to a 78% increase in optimized weld strength. A ‘pure’ shear surface present on the tool pin significantly reduces weld strength.

The electronic structure and elastic properties of YCu, YAg, and DyCu were studied by full-potential linearized augmented plane wave method (FP LAPW) on the basis of the density functional theory (DFT). The generalized gradient approximation (GGA) is applied for YCu, YAg, and the LDA+U is applied for DyCu. The density of states at the Fermi energy, NðEFÞ, are 1.08, 1.09, and 1.04 states/(eV unit cell) for YCu, YAg and DyCu, respectively. The elastic constants were calculated. The values for Pugh’s criterion are 2.30, 2.05 and 3.00 for YCu, DyCu and YAg, respectively. All of them are larger than 1.75, indicating the ductile manner of these materials. The calculated value of the anisotropy is close to 1, indicating highly isotropic behavior. [doi:10.2320/matertrans.MB200816]

Through reasonably designing the chemical composition and effectively optimizing the heat treatment techniques for a series of low carbon ultra-high strength bainitic steels (UHSBS), the combination of plasticity and toughness are excellent and the impact energy absorption (A KV ≥200 J) has been tripled compared to the previously advanced martensitic steel with the same strength level (>1470 MPa). It is confirmed that the microstructure is significantly refined, the average size of bainitic ferrite (BF) sub-grains is less than 20 nm and the average thickness of shear units in a BF lath is only about 1.6 nm by the atomic-force microscope (AFM) and scanning tunnelling microscope (STM). The refinement of sub-grains and enrichment of interstitial atom carbon in the bainitic ferrite, increase of dislocation density and retained austenite are the main factors that gover the steel's tensile strength and austenite stability or the impact energy absorption. Furthermore, the physical mechanism on the improvement of the combination of strength and toughness is discussed.

Residual stress magnitudes and distributions in structural stainless steel built-up sections have been comprehensively investigated in this study. A total of 18 test specimens were fabricated from hot-rolled stainless steel plates by means of shielded metal arc welding (SMAW). Two grades of stainless steel were considered, namely the austenitic grade EN 1.4301 and the duplex grade EN 1.4462. Using the sectioning method, the test specimens were divided into strips. The residual stresses were then computed by multiplying the strains relieved during sectioning by the measured Young׳s moduli determined from tensile and compressive coupon tests. Residual stress distributions were obtained for 10 I-sections, four square hollow sections (SHS) and four rectangular hollow sections (RHS). Peak tensile residual stresses reached around 80% and 60% of the material 0.2% proof stress for grades EN 1.4301 and EN 1.4462, respectively. Based upon the test data, simplified predictive models for residual stress distributions in stainless steel built-up I-sections and box sections were developed. Following comparisons with other available residual stress test data, the applicability of the proposed models was also extended to other stainless steel alloys. The proposed residual stress patterns are suitable for inclusion in future analytical models and numerical simulations of stainless steel built-up sections.