A temporary connection for an aluminium space frame

This thesis examines theoretically and experimentally the behaviour of a temporary end plate connection for an aluminium space frame structure, subjected to static loading conditions. Theoretical weld failure criterions are derived from basic fundamentals for both tensile and shear fillet welds. Direct account of weld penetration is taken by incorporating it into a more exact poposed weld model. Theoretical relationships between weld penetration and weld failure loads, failure planes and failure lengths are derived. Also, the variation in strength between tensile and shear fillet welds is shown to be dependent upon the extent of weld penetration achieved/ The proposed tensile weld failure theory is extended to predict the theoretical failure of the welds in the end plate space frame connection. A finite element analysis is conducted to verify the assumptions made for this theory. Experimental hardness and tensile tests are conducted to substantiate the extent and severity of the heat affected zone in aluminium alloy 6082-T6. Simple transverse and longitudinal fillet welded specimens of the same alloy, are tested to failure. These results together with those of other authors are compared to the theoretical predictions made by the proposed weld failure theories and by those made using Kamtekar's and Kato and Morita's failure equations, the -formula and BS 8118. Experimental tests are also conducted on the temporary space frame connection. The maximum stresses and displacements recorded are checked against results obtained from a finite element analysis of the connection. Failure predictions made by the proposed extended weld failure theory, are compared against the experimental results.

The effect of frequency and microstructure on corrosion fatigue crack propagation in high strength aluminium alloys

Fatigue crack growth in high strength aluminium alloy 7150 commercial plate material has been studied in both laboratory air and acidified aqueous salt solution. The aggressive aqueous environment enhanced fatigue crack growth rates by up to an order in magnitude compared to laboratory air. The enhancement in fatigue crack growth rate was accompanied by evidence of embrittlement in the crack path, involving both brittle intergranular and transgranular failure modes. Both the enhancement of fatigue crack growth rates and the extent of intergranular growth modes are dependent on cyclic frequency which, along with the absence of a similar frequency effect in a spray-formed version of the material with a significantly different grain structure, supports a mechanism of grain boundary hydrogen diffusion for intergranular corrosion fatigue crack growth. The convergence of corrosion fatigue crack growth rates at high ΔK in both spray-formed and conventional plate materials coincides with the operation of identical transgranular corrosion fatigue modes dependent on strain-controlled hydrogen diffusion ahead of the crack tip. © 1997 Acta Metallurgica Inc.

Comparison of crack growth behaviour between spray-formed and commercial plate Al-Zn-Mg-Cu alloy 7150

This paper compares the crack growth resistance of an experimental spray-formed extrusion with that of a commercial aluminium alloy, the two alloys having similar compositions but markedly different grain structures. Tensile and fracture behaviour is similar in both materials and is influenced by inclusion content. The two materials differ in their crack growth resistance, which is shown to be dependent upon grain size and shape. Environmentally-induced crack growth is favoured by aligned grain boundaries and small grain size.

Boron carbide reinforced aluminium matrix composite : physical, mechanical characterization and mathematical modelling

This paper investigates the manufacturing of aluminium-boron carbide composites using the stir casting method. Mechanical and physical properties tests to obtain hardness, ultimate tensile strength (UTS) and density are performed after solidification of specimens. The results show that hardness and tensile strength of aluminium based composite are higher than monolithic metal. Increasing the volume fraction of B4C, enhances the tensile strength and hardness of the composite; however over-loading of B4C caused particle agglomeration, rejection from molten metal and migration to slag. This phenomenon decreases the tensile strength and hardness of the aluminium based composite samples cast at 800 °C. For Al-15 vol% B4C samples, the ultimate tensile strength and Vickers hardness of the samples that were cast at 1000 °C, are the highest among all composites. To predict the mechanical properties of aluminium matrix composites, two key prediction modelling methods including Neural Network learned by Levenberg-Marquardt Algorithm (NN-LMA) and Thin Plate Spline (TPS) models are constructed based on experimental data. Although the results revealed that both mathematical models of mechanical properties of Al-B4C are reliable with a high level of accuracy, the TPS models predict the hardness and tensile strength values with less error compared to NN-LMA models.

Tris[4,4,4-trifluoro-1-(2-thienyl)butane-1,3-dionato]aluminium(III)-tris[4,4,4-trifluoro-1-(2-thienyl)butane-1,3-dionato]iron(III) (3/1)

In the title compound, [Al(C8H4F3O2S)3]3[Fe(C8H4F3O2S)3], the metal centre is statistically occupied by AlIII and FeIII cations in a 3:1 ratio. The metal centre is within an octahedral O6 donor set defined by three chelating substituted acetoacetonate anions. The ligands are arranged around the periphery of the molecule with a mer geometry of the S atoms.

In vivo confocal microscopy of the palpebral conjunctiva and tarsal plate

Purpose The aim of this work is to develop a more complete understanding of the in vivo histology of the human palpebral conjunctiva and tarsal plate. Methods. The upper eyelids of 11 healthy human volunteer subjects were everted, and laser scanning confocal microscopy was used to examine the various tissue layers of the palpebral conjunctiva and tarsal plate. Results The superficial and basal epithelial layers are composed of cells with gray cytoplasm and thick, light gray borders.Nuclei can not be seen. The stroma has a varied appearance; fibrous tissue is sometimes observed, interspersed with dark,amorphous lacunae, and crevases. Numerous single white or gray cells populate this tissue, and fine blood vessels are seen traversing the field. Occasional conjunctival microcysts and Langerhans cells are observed. The tarsal plate is dark and amorphous, and meibomian gland acini with convoluted borders are clearly observed. Acini are composed of an outer lining of large cuboidal cells, and differentiated secretory cells can be seen within the acini lumen. Conclusions Laser scanning confocal microscopy is capable of studying the human palpebral conjunctiva, tarsal plate, and acini of meibomian glands in vivo. The observations presented here may provide useful supplementary anatomical information relating to the morphology of this tissue.

Synchronous fluorescence and UV–vis spectroscopic studies of interactions between the tetracycline antibiotic, aluminium ions and DNA with the aid of the Methylene Blue dye probe

Synchronous fluorescence spectroscopy (SFS) was applied for the investigation of interactions of the antibiotic, tetracycline (TC), with DNA in the presence of aluminium ions (Al3+). The study was facilitated by the use of the Methylene Blue (MB) dye probe, and the interpretation of the spectral data with the aid of the chemometrics method, parallel factor analysis (PARAFAC). Three-way synchronous fluorescence analysis extracted the important optimum constant wavelength differences, Δλ, and showed that for the TC–Al3+–DNA, TC–Al3+ and MB dye systems, the associated Δλ values were different (Δλ = 80, 75 and 30 nm, respectively). Subsequent PARAFAC analysis demonstrated the extraction of the equilibrium concentration profiles for the TC–Al3+, TC–Al3+–DNA and MB probe systems. This information is unobtainable by conventional means of data interpretation. The results indicated that the MB dye interacted with the TC–Al3+–DNA surface complex, presumably via a reaction intermediate, TC–Al3+–DNA–MB, leading to the displacement of the TC–Al3+ by the incoming MB dye probe.

Fit optimisation of a distal medial tibia plate

An iterative method for the fit optimisation of a pre-contoured fracture fixation plate for a given bone data set is presented. Both plate shape optimisation and plate fit quantification are conducted in a virtual environment utilising computer graphical methods and 3D bone and plate models. Two optimised shapes of the undersurface of an existing distal medial tibia plate were generated based on a dataset of 45 3D bone models reconstructed from computed tomography image data of Japanese tibiae. The existing plate shape achieved an anatomical fit on 13% of tibiae from the dataset. Modified plate 1 achieved an anatomical fit for 42% and modified plate 2 a fit for 67% of the bones. If either modified plate 1 or plate 2 is used, then the anatomical fit can be increased to 82% for the same dataset. Issues pertaining to any further improvement in plate fit/shape are discussed.