Notch stress analyses of high‐frequency mechanical impact‐improved welds by using ρf = 1 mm and ρf = ρ + 1 mm approaches

This paper presents further assessments of the previously reported round‐robin fatigue data obtained from high‐frequency mechanical impact (HFMI)‐improved longitudinal welds. A detailed statistical analyses of geometry measurements of HFMI‐treated weld toe profiles are presented. The fatigue analyses based on notch stress as defined by the International Institute of Welding are performed using the finite element method. Notch stresses are assessed based on both the fictitious weld toe radius and the addition of measured actual notch radius to the fictitious radius. While no large differences are observed between the results of methods, the former one is found to be more practical and faster to implement from the end‐user point of view.     

Two‐Dimensional Self‐Organization of an Ordered Au Silicide Nanowire Network on a Si(110)‐16 × 2 Surface

A well‐ordered two‐dimensional (2D) network consisting of two crossed Au silicide nanowire (NW) arrays is self‐organized on a Si(110)‐16 × 2 surface by the direct‐current heating of ≈1.5 monolayers of Au on the surface at 1100 K. Such a highly regular crossbar nanomesh exhibits both a perfect long‐range spatial order and a high integration density over a mesoscopic area, and these two self‐ordering crossed arrays of parallel‐aligned NWs have distinctly different sizes and conductivities. NWs are fabricated with widths and pitches as small as ≈2 and ≈5 nm, respectively. The difference in the conductivities of two crossed‐NW arrays opens up the possibility for their utilization in nanodevices of crossbar architecture. Scanning tunneling microscopy/spectroscopy studies show that the 2D self‐organization of this perfect Au silicide nanomesh can be achieved through two different directional electromigrations of Au silicide NWs along different orientations of two nonorthogonal 16 × 2 domains, which are driven by the electrical field of direct‐current heating. Prospects for this Au silicide nanomesh are also discussed.     

Residual strength at −40 °C of a precracked cold‐formed rectangular hollow section made of ultra‐high‐strength steel – an engineering approach

This study investigated the residual strength of a precracked cold‐formed rectangular hollow section made of novel ultra‐high‐strength steel. The primary goal was to experimentally discover the residual strength of the structure when used in low temperature service conditions. The secondary goal was to predict the residual strength by using a J‐integral approach with nonlinear finite element calculations and to compare these predictions with measured results. The experimental tests were carried out with a beam in four‐point bending loading. The test specimens were taken from a cold‐formed rectangular hollow section fabricated from direct quenched (untempered) ultra‐high‐strength steel S960 QC omitting the annealing in the fabrication process. The tests for final failure were carried out at ?40 °C, with the exception of the first pilot test. There were two kinds of tests: (1) the beam was cyclically loaded until the final fracture or the fatigue precrack was first introduced and (2) the specimen was then subjected to a quasistatic bending loading condition until it failed. The new experimental results matched well with our predictions, and both confirmed the high toughness of ultra‐high‐strength steel in beam construction studied, even at a low ambient temperature.     

Technical note – effects of seaming conditions on external and internal double‐seam characteristics in round metal cans

Canning is the major packaging technology for fully preserved food products. To obtain safe canned foods with extended shelf‐life, the closed cans have to be hermetic. The consistency and quality of the seaming process are crucial to food safety. This note investigates the effects of different seaming conditions (base‐plate pressure and seaming‐roller pressure) on external (seam thickness, seam height) and internal (body hook length, overlap, lid hook length, seam gap and body hook butting) double‐seam characteristics in round metal cans. External double‐seam characteristics were significantly affected by the seaming‐roller pressure during the final closure of the cans. Generally, there were small effects of base‐plate pressure on the external double‐seam characteristics. In contrast, all the investigated double‐seam characteristics were affected significantly by the seaming‐roller pressure, whereas only body hook length and seam gap were significantly affected by the base‐plate pressure. This note illustrates the importance of close control and optimization of the seaming conditions during production of canned foods as a means to reduce the processing induced variability in double‐seam characteristics, and subsequently to obtain safe and high‐quality canned products. Copyright © 2005 John Wiley & Sons, Ltd.     

Microstructure and Mechanical Properties of Al25 − xCr25 + 0.5xFe25Ni25 + 0.5x (x = 19, 17, 15 at%) Multi‐Component Alloys

A series of Al_{25 ? x}Cr_{25 + 0.5x}Fe₂₅Ni_{25 + 0.5x} (x = 19, 17, 15 at%) multi‐component alloys are prepared by arc‐melting and rapid solidification of copper molds. The technique of thermal‐mechanical processing is further applied to the master alloys to improve their mechanical properties. These alloys consist of face‐centered cubic (FCC) and body‐centered cubic (BCC) structure. The volume fraction of the BCC phase increases as Al content increase and Cr and Ni contents decrease, accompanied with a microstructural evolution from dendritic structure to lamella‐like structure. Due to the increase of volume fraction of BCC phase, the master alloys exhibit an increased strength and a declined ductility as Al content increases. The rapid solidified alloys have more BCC phase compared with the master alloys, which enhances the strength and decreases the ductility. After homogenization, hot‐rolling, and annealing at 1000 °C, the Al₈Cr_33.5Fe₂₅Ni_33.5 alloy displays excellent combination of strength (yield strength is ～635 MPa and fracture strength is ～1155 MPa) and ductility (tension strain is ～11%).