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.     

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%).

     

Micro‐Macroporous Composite Materials – Preparation Techniques and Selected Applications: A Review

Pores, on several orders of magnitude in size, control the properties of a solid material to a large extent. This is just as true for materials containing pores in the sub‐nanometer range like zeolites as for cellular foam structures with pores of several millimeters in size. All these porous materials have their distinct potential application ranging from heterogeneous catalysis to metal melt filtration. In many cases, the (hierarchical) combination of pores with different size regimes can improve the performance of the respective porous material or can lead to entirely new properties and applications. This review addresses the preparation and properties of microporous‐macroporous composite materials based on cellular foam supports (ceramic, metal, polymer) with a coating of a microporous compound (zeolite, zeotype framework, metal‐organic framework). The manufacturing of these materials can either be performed by dispersion‐based techniques, where the microporous coating is applied from a dispersion onto the cellular support (ex situ), or in situ by crystallization of the microporous compound directly onto the struts of the foam structure. In both cases, the general procedure can be modified by a pretreatment of the cellular support in order to improve the coating layer adherence, the overall amount of deposited material, or to control of the crystal morphology of the microporous compound.

     

Automatically inf − sup compliant diamond‐mixed finite elements for Kirchhoff plates

We develop a mixed finite‐element approximation scheme for Kirchhoff plate theory based on the reformulation of Kirchhoff plate theory of Ortiz and Morris [1]. In this reformulation the moment‐equilibrium problem for the rotations is in direct analogy to the problem of incompressible two‐dimensional elasticity. This analogy in turn opens the way for the application of diamond approximation schemes (Hauret et al. [2]) to Kirchhoff plate theory. We show that a special class of meshes derived from an arbitrary triangulation of the domain, the diamond meshes, results in the automatic satisfaction of the corresponding inf ? sup condition for Kirchhoff plate theory. The attendant optimal convergence properties of the diamond approximation scheme are demonstrated by means of the several standard benchmark tests. We also provide a reinterpretation of the diamond approximation scheme for Kirchhoff plate theory within the framework of discrete mechanics. In this interpretation, the discrete moment‐equilibrium problem is formally identical to the classical continuous problem, and the two differ only in the choice of differential structures. It also follows that the satisfaction of the inf ? sup condition is a property of the cohomology of a certain discrete transverse differential complex. This close connection between the classical inf ? sup condition and cohomology evinces the important role that the topology of the discretization plays in determining convergence in mixed problems. Copyright © 2013 John Wiley & Sons, Ltd.     

Microstructures and corrosion resistance of as‐cast aluminum‐10 wt.% silicon and aluminum‐20 wt.% silicon alloys

The microstructures and corrosion resistance of two as‐cast alloys, aluminum‐10 wt.% silicon hypoeutectic alloy and aluminum‐20 wt.% silicon (weight percent) hypereutectic alloy are investigated by conventional casting, the scanning electron microscope equipped with oxford X‐ray energy dispersive spectroscopy system and transmission electron microscope are applied for analysis. The results show that the microstructures change from the strip‐like into lump shape with the increase of silicon content from 10 % to 20 %. The electrochemical polarization curves prove that the aluminum‐20 wt.% hypereutectic silicon alloy had the better resistance with the corrosion potential of ?1.414 V and corrosion current density of 5.41 ? 10^?5 ampere compared with the aluminum‐10 wt.% silicon hypoeutectic alloy.     

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.     

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.