Search results

The purpose of this paper is to investigate on the behaviour of a delaminated stiffened panel; the delamination growth is simulated via fracture elements implemented in B2000++® code based on the Modified Virtual Crack Closure Technique (MVCCT), matrix cracking and fibre failure have been also taken into account.

In order to correctly apply the MVCCT on the delamination front a very fine three-dimensional (3D) mesh is required very close to the delaminated area, while a 2D-shell model has been employed for the areas of minor interest. In order to couple the shell domain to the solid one, shell-to-solid coupling elements based on kinematic constraints have been used.

Results obtained with the global/local approach are in good correlation with those obtained with experimental results.

The global/local approach based on kinematic coupling elements in conjunction with fracture elements allows to investigate and predict the behaviour of a stiffened delaminated composite panel in an efficient and effective way.

The purpose of this paper is to investigate and to assess the capabilities of the most common finite element (FE)‐based tools to deal with global‐local analysis. Two kinds of coupling were investigated: shell to shell and shell to solid.

The issue of connecting non‐matching FE global and local models, characterized by different mesh refinements and/or different element types, was addressed by introducing appropriate kinematic constraints on the nodes at the interfaces. The coupling techniques available in the three FE‐based codes (ABAQUS^®, NASTRAN^® and ANSYS^®), were assessed by applying them on a common numerical test case (non‐linear buckling analysis of a square plate). Results of the global‐local simulations were compared to the results obtained for relevant reference solutions.

The continuity of displacements and stresses across the interface between global and local models and the influence of the presence of the local model on the global model solution were used as parameters to test the quality of the results. It was observed that the tools implemented in the different codes provide different results. The results characterized by a higher quality were found by using the Multi Point Constraint available in ABAQUS^®.

When dealing with complex structures, multi‐scale (global‐local) approaches are commonly adopted to optimize the computational cost by increasing mesh refinements and/or introducing elements with different formulations in specific region of the structures identified as “local model”. In this paper an overview of the coupling tools available in the main commercial FE code is given.

The main objective of this work is to assess the current capabilities of different commercial finite element (FE) codes in simulating the progressive damage of composite structures under quasi-static loading condition in post-buckling regime.

Progressive failure analysis (PFA) methodologies, available in the investigated FE codes, were applied to a simple test case extracted from literature consisting in a holed composite plate loaded in compression.

Results of the simulations are significantly affected by the characteristic parameters needed to feed the degradation models implemented in each code. Such parameters, which often do not have a physical meaning, have to be necessarily set upon fitting activity with an experimental database at coupon level. Concerning the test case, all the codes were found able to capture the buckling load and the failure load with a good accuracy.

This paper would to give an insight into the PFA capabilities of different FE codes, providing the guidelines for setting the degradation model parameters which are of major interest.

This paper aims to present recently published resources on library instruction and information literacy providing an introductory overview and a selected annotated bibliography of publications covering all library types.

This paper introduces and annotates English-language periodical articles, monographs, dissertations, reports and other materials on library instruction and information literacy published in 2018.

The paper provides a brief description of all 422 sources, and highlights sources that contain unique or significant scholarly contributions.

The information may be used by librarians and anyone interested as a quick reference to literature on library instruction and information literacy.

The purpose of this paper is to improve knowledge of the water impact phenomenon from both the experimental and numerical points of view.

A drop test campaign on water was carried out on semi‐cylindrical steel structures. Therefore, an experimental database for validation purpose was generated. Subsequently, a finite element model was developed in LS‐DYNA in order to reproduce the tests. The behaviour of water was modeled by using the smoothed particle hydrodynamics (SPH) methods. Numerical simulations were compared to experimental data and the influence of some numerical parameters on the simulations was investigated.

The FE model was found to be able to reproduce the tests, at least in terms of acceleration peak and distribution of plastic deformation. Acceptable prediction was also found for the pressure peak in soft areas.

In case of low velocity impact, the water model was found to be too rigid and the acceleration peaks were over‐predicted by the simulations. Further investigations are needed to adjust the water model in order to obtain better results also in the case of low velocity impact.

The experimental database could be very useful to the crashworthiness community to validate their numerical models. Moreover, the present paper provides guidelines to modelling the water impact correctly.

The purpose of this study is to examine the effects of self-affirmation on African American smokers' intentions to quit smoking sooner and desire to stop smoking altogether in response to viewing graphic cigarette warning labels. It also tested the mediating role of perceived susceptibility and self-efficacy in explaining the impact of self-affirmation.

African American smokers (N = 158) were recruited to participate in a controlled experiment. Participants first completed a short questionnaire about their demographic background and smoking-related attitudes and behavior. They were then randomly assigned to engage in either a self-affirmation task or a control task and viewed two graphic cigarette warning labels subsequently. Participants then responded to a questionnaire about their perceived susceptibility to smoking-related diseases, perceived self-efficacy to quit smoking, intentions to quit smoking and desire to stop smoking altogether.

Results showed that engaging in self-affirmation prior to exposure to graphic cigarette warning labels increased African American smokers' perceived susceptibility to smoking-related diseases, but decreased their perceived self-efficacy to quit smoking. Furthermore, self-affirmation indirectly enhanced smokers' intentions to quit smoking sooner and desire to stop smoking altogether through increased perceived susceptibility. It also had an unexpected negative indirect effect on intentions to quit smoking sooner through decreased self-efficacy.

This study is one of the few studies that investigates the effect of self-affirmation on African American smokers' responses toward graphic cigarette warning labels.

Powder bed fusion processes are common due to their ability to build complex components without the need for complex tooling. While additive manufacturing has gained increased interest in industry, academia and government, flaws are often still generated during the deposition process. Many flaws can be avoided through careful processing parameter selections including laser power, hatch spacing, spot size and shielding gas flow rate. The purpose of this paper is to study the effect of shielding gas flow on vapor plume behavior and on final deposition quality. The goal is to understand more fully how each parameter affects the plume and deposition process.

A filtered-photodiode based sensor was mounted onto a commercial EOS M280 machine to observed plume emissions. Three sets of single tracks were printed, each with one of three gas flow rates (nominal, 75% nominal and 50% nominal). Each set contained single-track beads deposited atop printed pedestals to ensure a steady-state, representative build environment. Each track had a set power and speed combination which covered the typical range of processing parameters. After deposition, coupons were cross-sectioned and bead width and depth were measured. Finally, bead geometry was compared to optical emissions originating in the plume.

The results show that decreasing gas flow rate, increasing laser power or increasing scan speed led to increased optical emissions. Furthermore, decreasing the gas cross-flow speed led to wider and shallower melt pools.

To the best of the authors’ knowledge, this paper is among the first to present a relationship among laser parameters (laser power, scan speed), gas flow speed, plume emissions and bead geometry using high-speed in situ data in a commercial machine. This study proposes that scattering and attenuation from the plume are responsible for deviations in physical geometry.

This paper aims to analyze the steady two-dimensional stagnation-point flow of an electrically conducting Newtonian or micropolar fluid when the obstacle is uniformly heated.

The governing boundary layer equations are transformed into a system of ordinary differential equations using appropriate similarity transformations. Some analytical considerations about existence and uniqueness of the solution are obtained. The system is then solved numerically using the bvp4c function in MATLAB.

If the temperature of the obstacle T_w coincides with the environment temperature T₀, then the motion reduces to the usual orthogonal stagnation-point flow; if T_w = T₀, then it is necessary to include in the similarity function describing the velocity an oblique part due to the temperature. Also, the presence of a uniform external magnetic field orthogonal to the obstacle is examined. In all cases, the motion is reduced to a system of nonlinear ordinary differential equations with boundary conditions, whose solution is discussed numerically when the Prandtl and the Hartmann number varies.

The present results are original and new for the problem of magnetohydrodynamic mixed convection in the plane stagnation-point flow of a Newtonian or a micropolar fluid over a vertical flat plate. At infinity, the motion approaches the orthogonal stagnation-point flow of an inviscid fluid; the effect of an uniform external magnetic field is considered, and the obstacle has a uniform temperature.

This paper aims to discuss the physical and thermal properties of the three-dimensional (3D) printing natural composite filament, as well as the tensile behaviour of the printed composites to get an insight of its possibility to be used as an ankle–foot orthosis (AFO) material.

Physical test that was conducted includes scanning electron microscopy analysis, thermogravimetric/differential scanning calorimetry analysis as well as the effect of fibre load after extrusion on the filament morphology. Tensile test was conducted with different amounts of fibre loads (0, 3, 5 and 7 Wt.%) on the printed specimens.

There is an increment of strength as the fibre load is increased to 3 Wt.%; however, it decreases significantly as it is increased to 5 and 7 Wt.% because of the presence of voids. It also shows that the extrusion temperature severely affects the structure of the filaments, which will then affect the strength of the printed composites. Based on the results, it is possible to use kenaf/polylactic acid (PLA) filament to print out AFO as long as the filament production and printing process are being controlled properly.

The unique aspect of this paper is the investigation of kenaf/PLA filament as a material for 3D printing, as well as its material consideration for AFO manufacturing. This paper also studies the effect of extrusion temperature on the morphological structure of the filament and its effect on the tensile properties of the printed kenaf/PLA specimen.

The present study aims to trace out the science research output of top Indian universities from 2015 to 2019, as reflected in the Web of Science (WOS) database.

The present study has selected the Science Citation Index (SCI) of WOS core collection for selecting top Indian universities in terms of total publications in the last five years (2015–2019). The University of Delhi (DU), Banaras Hindu University (BHU), Anna University (AU), Jadavpur University (JU) and Punjab University (PU) have been selected. The study identified the most prolific authors, collaborating countries, collaborating institutions and the impact of their output in terms of citations per paper (CPP) and relative citation impact (RCI). For visualizing purposes, VOSviewer was used. The study also identified frequently used keywords and channels used for communicating research results.

The authors retrieved 26,173 documents consisting of journal articles, review papers and proceeding papers. The consistent growth of science research output has been observed. The University of Delhi (DU) has the maximum science publications. The study reflects that multi-authored papers have more research impact in terms of citation received. The USA, South Korea and Germany are the most collaborating countries. The top Indian Universities have a major collaboration with Anna University, Indian Institute of Technology, Center for Scientific and Industrial Research (CSIR) of India.

The present study reveals how the science research output of top Indian universities has grown in the last few years. The findings of the study can be used for identifying specific science research areas where special attention can be given.