Local buckling behaviour of steel plate elements supported by a plastic foam material

Sandwich panels comprising steel facings and a polystyrene foam core are increasingly used as roof and wall claddings in buildings in Australia. When they are subjected to loads causing bending and/or axial compression, the steel plate elements of their profiled facing are susceptible to local buckling. However, when compared to panels with no foam core, they demonstrate significantly improved local buckling behaviour because they are supported by foam. In order to quantify such improvements and to validate the use of available design buckling stress formulae, an investigation using finite element analyses and laboratory experiments was carried out on steel plates that are commonly used in Australia of varying yield stress and thickness supported by a polystyrene foam core. This paper presents the details of this investigation, the buckling results and their comparison with available design buckling formulae.

Socioeconomic differences in food choices : deficiencies in nutrition knowledge or simply too much on your plate?

Nutrition knowledge is associated with dietary choices in the general population and has been proposed to contribute to socioeconomic differences in food choices and corresponding socioeconomic gradients in mortality and morbidity for a number of diet-related illnesses. This paper explores current evidence regarding socioeconomic differences in nutrition knowledge, reviewing the components of nutrition knowledge that have been assessed, the dietary intake or food choice outcomes considered, and the socioeconomic indicators used. In addition, this paper considers how socioeconomic differences in nutrition knowledge may arise, and potential determinants of inequalities in the application of nutrition knowledge. It highlights issues to consider when developing strategies to improve nutrition knowledge and facilitate knowledge application among those of lower socioeconomic position.

Computational strategies for surface fitting using thin plate spline finite element methods

Thin plate spline finite element methods are used to fit a surface to an irregularly scattered dataset [S. Roberts, M. Hegland, and I. Altas. Approximation of a Thin Plate Spline Smoother using Continuous Piecewise Polynomial Functions. SIAM, 1:208--234, 2003]. The computational bottleneck for this algorithm is the solution of large, ill-conditioned systems of linear equations at each step of a generalised cross validation algorithm. Preconditioning techniques are investigated to accelerate the convergence of the solution of these systems using Krylov subspace methods. The preconditioners under consideration are block diagonal, block triangular and constraint preconditioners [M. Benzi, G. H. Golub, and J. Liesen. Numerical solution of saddle point problems. Acta Numer., 14:1--137, 2005]. The effectiveness of each of these preconditioners is examined on a sample dataset taken from a known surface. From our numerical investigation, constraint preconditioners appear to provide improved convergence for this surface fitting problem compared to block preconditioners.

Improving the shear capacities of lipped channel beams with web openings using plate stiffeners

Cold-formed steel lipped channel beams (LCB) are used extensively in residential, industrial and commercial buildings as load bearing structural elements. Their shear capacities are considerably reduced when web openings are included for the purpose of locating building services. Past research has shown that the shear capacities of LCBs were reduced by up to 70% due to the inclusion of these web openings. Hence there is a need to improve the shear capacities of LCBs with web openings. A cost effective way of eliminating the detrimental effects of large web openings is to attach suitable stiffeners around the web openings and restore the original shear strength and stiffness of LCBs. Hence detailed experimental studies were undertaken to investigate the behaviour and strength of LCBs with stiffened web openings subject to shear, and combined bending and shear actions. Both plate and stud stiffeners with varying sizes and thicknesses were attached to the web elements of LCBs using different screw-fastening arrangements. Simply supported test specimens of LCBs with aspect ratios of 1.0 and 1.5 were loaded at mid-span until failure. Numerical studies were also undertaken to investigate the strength of LCBs with stiffened web openings. Finite element models of LCBs with stiffened web openings under shear, combined bending and shear actions were developed to simulate the behaviour of tested LCBs. The developed models were then validated by comparing their results with experimental results and used in further studies. Both experimental and finite element analysis results showed that the stiffening arrangements recommended by past research and available design guidelines are not adequate to restore the original shear strengths of LCBs. Therefore new stiffener arrangements were proposed based on screw fastened plate stiffeners. This paper presents the details of this research study and the results.

Three-dimensional printing in the construction industry: A review

3D printing (3Dp) has long been used in the manufacturing sector as a way to automate, accelerate production and reduce waste materials. It is able to build a wide variety of objects if the necessary specifications are provided to the printer and no problems are presented by the limited range of materials available. With 3Dp becoming cheaper, more reliable and, as a result, more prevalent in the world at large, it may soon make inroads into the construction industry. Little is known however, of 3Dp in current use the construction industry and its potential for the future and this paper seeks to rectify this situation by providing a review of the relevant literature. In doing this, the three main 3Dp methods of contour crafting, concrete printing and D-shape 3Dp are described which, as opposed to the traditional construction method of cutting materials down to size, deliver only what is needed for completion, vastly reducing waste. Also identified is 3Dp’s potential to enable buildings to be constructed many times faster and with significantly reduced labour costs. In addition, it is clear that construction 3Dp can allow the further inclusion of Building Information Modelling into the construction process - streamlining and improving the scheduling requirements of a project. However, current 3Dp processes are known to be costly, unsuited to large-scale products and conventional design approaches, and have a very limited range of materials that can be used. Moreover, the only successful examples of construction in action to date have occurred in controlled laboratory environments and, as real world trials have yet to be completed, it is yet to be seen whether it can be it equally proficient in practical situations. Key Words: 3D Printing; Contour Crafting; Concrete Printing; D-shape; Building Automation.

Creation and copyright law: The case of 3D printing

The Australian Law Reform Commission is conducting an inquiry into copyright law and the digital economy in 2012 and 2013.The President, Rosalind Croucher, stated: “While the Copyright Act has been amended on occasion over the past 12 years to account for digital developments, these changes occurred before the digital economy took off. The Australian Law Reform Commission will need to find reforms that are responsive to this new environment, and to future scenarios that are still in the realm of the imagination. It is a complex and important area of law and we are looking forward to some robust debate and discussion during the course of this very important Inquiry.”

A semiautomatic method to identify vertebral end plate lesions (Schmorl's nodes)

Background Context There are differences in definitions of end plate lesions (EPLs), often referred to as Schmorl’s nodes, that may, to some extent, account for the large range of reported prevalence (3.8 to 76%). Purpose To develop a technique to measure the size, prevalence and location of EPLs in a consistent manner. Study Design/Setting This study proposed a method using a detection algorithm which was applied to five adolescent females (average age 15.1 years, range 13.0 to 19.2 years) with idiopathic scoliosis (average major Cobb angle 60°, range 55 to 67°). Methods Existing low-dose, computed tomography scans were segmented semi-automatically to extract 3D morphology of each vertebral endplate. Any remaining attachments to the posterior elements of adjacent vertebrae or endplates were then manually sectioned. An automatic algorithm was used to determine the presence and position of EPLs. Results EPLs were identified in 15 of the 170 (8.8%) endplates analysed with an average depth of 3.1mm. 11/15 of the EPLs were seen in the lumbar spine. The algorithm was found to be most sensitive to changes in the minimum EPL gradient at the edges of the EPL. Conclusions This study describes an imaging analysis technique for consistent measurement of the prevalence, location and size of EPLs. The technique can be used to analyse large populations without observer errors in EPL definitions.

Identifying vertebral end plate lesions (schmorl's nodes) using a semi-automatic method

INTRODUCTION There is a large range in the reported prevalence of end plate lesions (EPLs), sometimes referred to as Schmorl's nodes in the general population (3.8-76%). One possible reason for this large range is the differences in definitions used by authors. Previous research has suggested that EPLs may potentially be a primary disturbance of growth plates that leads to the onset of scoliosis. The aim of this study was to develop a technique to measure the size, prevalence and location of EPLs on Computed Tomography (CT) images of scoliosis patients in a consistent manner. METHODS A detection algorithm was developed and applied to measure EPLs for five adolescent females with idiopathic scoliosis (average age 15.1 years, average major Cobb 60°). In this algorithm, the EPL definition was based on the lesion depth, the distance from the edge of the vertebral body and the gradient of the lesion edge. Existing low-dose, CT scans of the patients' spines were segmented semi-automatically to extract 3D vertebral endplate morphology. Manual sectioning of any attachments between posterior elements of adjacent vertebrae and, if necessary, endplates was carried out before the automatic algorithm was used to determine the presence and position of EPLs. RESULTS EPLs were identified in 15 of the 170 (8.8%) endplates analysed with an average depth of 3.1mm. 73% of the EPLs were seen in the lumbar spines (11/15). A sensitivity study demonstrated that the algorithm was most sensitive to changes in the minimum gradient required at the lesion edge. CONCLUSION An imaging analysis technique for consistent measurement of the prevalence, location and size of EPLs on CT images has been developed. Although the technique was tested on scoliosis patients, it can be used to analyse other populations without observer errors in EPL definitions.

Numerical analysis for the interlayer toughening of piezoelectric smart composite plate

The piezoelectric composite material could engender stress concentration resulting from small cracks during layers easily, as the cracks growth will lead to the failure of the whole structure. In this paper, a finite element model for piezoelectric composite materials by ABAQUS including interlayer crack was established, and the J integral and crack tip stress of different types PZT patches were calculated by using the equivalent integral method. Then, the J integral for adhesive layers with different thickness, elastic modulus considering and not considering piezoelectricity was investigated. The results show that the J integral of mode I, II reduces with thicker adhesive layer and lower elastic modules, and the J integral of mode II decreases more sharply than that of mode I.

Ink-jet printing of graphene for flexible electronics: An environmentally-friendly approach

Mechanical flexibility is considered an asset in consumer electronics and next-generation electronic systems. Printed and flexible electronic devices could be embedded into clothing or other surfaces at home or office or in many products such as low-cost sensors integrated in transparent and flexible surfaces. In this context inks based on graphene and related two-dimensional materials (2DMs) are gaining increasing attention owing to their exceptional (opto)electronic, electrochemical and mechanical properties. The current limitation relies on the use of solvents, providing stable dispersions of graphene and 2DMs and fitting the proper fluidic requirements for printing, which are in general not environmentally benign, and with high boiling point. Non-toxic and low boiling point solvents do not possess the required rheological properties (i.e., surface tension, viscosity and density) for the solution processing of graphene and 2DMs. Such solvents (e.g., water, alcohols) require the addition of stabilizing agents such as polymers or surfactants for the dispersion of graphene and 2DMs, which however unavoidably corrupt their properties, thus preventing their use for the target application. Here, we demonstrate a viable strategy to tune the fluidic properties of water/ethanol mixtures (low-boiling point solvents) to first effectively exfoliate graphite and then disperse graphene flakes to formulate graphene-based inks. We demonstrate that such inks can be used to print conductive stripes (sheet resistance of ~13 kΩ/□) on flexible substrates (polyethylene terephthalate), moving a step forward towards the realization of graphene-based printed electronic devices.

Can we safely deform a plate to fit every bone? Population-based fit assessment and finite element deformation of a distal tibial plate

Anatomically precontoured plates are commonly used to treat periarticular fractures. A well-fitting plate can be used as a tool for anatomical reduction of the fractured bone. Recent studies highlighted that some plates fit poorly for many patients due to considerable shape variations between bones of the same anatomical site. While it is impossible to design one shape that fits all, it is also burdensome for the manufacturers and hospitals to produce, store and manage multiple plate shapes without the certainty of utilization by a patient population. In this study, we investigated the number of shapes required for maximum fit within a given dataset, and if they could be obtained by manually deforming the original plate. A distal medial tibial plate was automatically positioned on 45 individual tibiae, and the optimal deformation was determined iteratively using finite element analysis simulation. Within the studied dataset, we found that: (i) 89% fit could be achieved with four shapes, (ii) 100% fit was impossible through mechanical deformation, and (iii) the deformations required to obtain the four plate shapes were safe for the stainless steel plate for further clinical use. The proposed framework is easily transferable to other orthopaedic plates.