On the variational foundations of the substitute shape function technique

In this paper, an element recently developed by Whitcomb (Comput. Struct. 22, 387–398, 1986) along the lines of the so-called substitute shape function technique (SSFT) has been re-examined. It is shown that a varialional basis can be found for this element in the form of a modified version of the variational theorem due to Hellinger and Reissner. On the basis of this theorem, a two-dimensional element has been developed using separate trial functions for the displacements and the shear strain. The element is identical to Whitcomb's element; however, the proposed approach appears to have certain advantages over SSFT.     

Uncertainty analysis of the use of a retailer fidelity card scheme in the assessment of food additive intake

The feasibility of using a retailer fidelity card scheme to estimate food additive intake was investigated in an earlier study. Fidelity card survey information was combined with information provided by the retailer on levels of the food colour Sunset Yellow (E110) in the foods to estimate a daily exposure to the additive in the Swiss population. As with any dietary exposure method the fidelity card scheme is subject to uncertainties and in this paper the impact of uncertainties associated with input variables including the amounts of food purchased, the levels of E110 in food, the proportion of food purchased at the retailer, the rate of fidelity card usage, the proportion of foods consumed outside of the home and bodyweights and with systematic uncertainties was assessed using a qualitative, deterministic and probabilistic approach. An analysis of the sensitivity of the results to each of the probabilistic inputs was also undertaken. The analysis identified the key factors responsible for uncertainty within the model and demonstrated how the application of some simple probabilistic approaches can be used quantitatively to assess uncertainty.     

Nonlinear buckling analysis of two-dimensional frames composed of curved non-prismatic members

A novel finite element methodology is presented for the analysis of arbitrarily shaped two-dimensional frames composed of curved non-prismatic members. The method utilizes a hybrid-mixed approach in conjunction with an updated Lagrangian formulation. The proposed methodology goes beyond existing modelling capabilities for it enables a more realistic analysis of the nonlinear response of thin-walled frames undergoing large deflections (displacements and/or rotations) in the pre- and postbuckling range. Efficiency, accuracy and reliability of the proposed method are demonstrated on the basis of numerical experiments carried out on several typical examples.     

Estimation of biometric parameters from cattle rump using free-hand scanning and a 3D data processing algorithm

The quantity and quality of phenotypic data recovered from farm animals became a bottleneck for breeding programmes, and new tools are required to overcome this problem. This study evaluated the use of a portable structured light scanner and a 3D modelling to recover biometric information of the rump region in cattle. Virtual 3D models were created based on coordinates extracted from the points-cloud obtained through reverse engineering. A MATLAB algorithm was implemented to identify reference points, which were used to automatically calculate rump width, length, and angle. Results were compared to measurements performed directly in vivo and in the 3D models. There was no difference among rump parameter values obtained among biometry methods, though an interaction with body condition score was observed for rump width. The algorithm allowed evaluating correlations within biometric parameters, as well as extracting silhouettes of selected areas to evaluate differences caused by the mobilisation of subcutaneous fat.     

A novel approach to investigating frictional electrification and charge decay on woven textile fabrics treated with ionic antistatic and hydrophilic surface finishes

The results of a study of charge generation and decay for range of woven fabrics from ring spun cotton yarns, ring spun polyester yarns, and flat continuous filament polyester yarns treated with topical finishes are reported. The topical finishes include commercially available ionic antistatic finishes, one commercially available hydrophilic finish, and a new experimental moisture management finish. The fabrics were rubbed against surface of steel and Polytetrafluoroethylene (PTFE; Teflon^®) and their frictional electrification and charge dissipation were monitored. It is shown that fabrics from cotton have a more rapid inherent charge decay than fabrics from polyester. Ionic antistatic finishes are shown to be effective in reducing charge generation and promoting charge decay and this is particularly true for the fabrics made from filament polyester. When commercially available and experimental hydrophilic finishes were applied on fabrics made from filament polyester, less charge was generated and the generated charge decayed quickly compared to the control untreated fabrics. In an attempt to understand the mechanism of charge decay, two probes were used with one placed on the top of the rubbed area and the other placed some distance from the rubbed area. It was found that the generated charge migrated from the rubbed areas to other parts of the sample. This behavior is more pronounced for fabrics treated with hydrophilic and moisture management finishes, which cause the charge to decay exponentially.     

Quantitative validation of the discrete element method using an annular shear cell

The discrete element method (DEM) is often used as the “gold standard” for comparison to continuum-level theories and/or coarse-grained models of granular material flows due to its derivation from first-principal constructs, like contact mechanics. Despite its prevalence, the method is most often validated against experiment in only qualitative ways - comparison of mixing rates, gross features of concentration profiles, etc. - for exactly the reason it has found its popularity; detailed experimental measurements are difficult and often expensive. In this paper, we outline work aimed at using detailed, particle-level experimental measurements to quantitatively validate DEM simulations. Specifically, we examine the flow in a horizontally-aligned annular shear cell. Measurements are performed using digital particle tracking velocimetry (DPTV) so that the velocity, granular temperature, and solids fractions profiles may be extracted. Computationally, we attempt to match the experimental measurements as closely as possible and study the impact of a variety of contact mechanics-inspired force laws as well as perform sensitivity analysis on device and particle geometry and material properties employed.     

Process‐Driven Microstructure Control in Melt‐Extrusion‐Based 3D Printing for Tailorable Mechanical Properties in a Polycaprolactone Filament

3D printing techniques are utilized to produce biomaterial scaffolds with porous architectures that enable cell attachment, biological factors, and appropriate mechanical strength. As the basic building block of a scaffold, the individual filaments should have sufficient mechanical properties, comprising high compressive loading, and fracture resistance to mimic the natural tissue organisation. In this contribution, process–structure–property relationships in melt extruded polycaprolactone filaments are investigated by considering crystalline features, tensile properties, and an array of processing parameters. The tensile properties of the filaments are improved significantly with relatively higher screw rotational speed and relatively lower processing temperature resulting in considerable increase in Young's modulus. The favorable properties are attributed to the increased crystal volume fraction and anisotropy. Thus, this study provides initial pathways for the potential control of mechanical properties of bioscaffolds via engineering crystalline structural features in printed filaments.     

Geometrically nonlinear finite element analysis of tapered beams

A novel finite element methodology is developed capable of analyzing the geometrically nonlinear behavior of thin-walled framed structures composed of non-prismatic members. The pertinent element matrices are formulated on the basis of a modified version of the variational theorem of Hellinger and Reissner. Finite geometry changes are consistently described by using an updated Lagrangian (U.L.) formulation. Validity, accuracy and reliability of the proposed scheme are examined on the basis of several well-selected test examples.     

Design and analysis of perforated MEMS resonator

Microsystem Technologies - In this paper, we have designed an optimal design of microelectromechanical (MEMS) resonator. The paper explains the idea of suitable design, modeling and optimization of...