Shell Model

Steel storage racks are three-dimensional framed structures fabricated from cold formed steel sections, wherein hook-in end connectors are used to make beam–column connections which are basically boltless and semi-rigid in nature. Different types of beam end connectors with different geometry of the connected members are available, making it impossible to develop a generalized analytical model. Only very few theoretical models are available to evaluate the performance of the joints for some typical connectors. More often experimental evaluation and numerical studies are needed to predict the behaviour of every different type of connectors. In the present study eighteen experiments were conducted on a commercially available pallet rack connection by varying the most influencing parameters such as thickness of the column, depth of the connector and the depth of the beam. The main objective of this work is to quantify the beam to column joint, flexibility of commonly used pallet rack frame and to develop a general Frye–Morris type/three parameter power model type moment versus relative rotation relationship. A companion finite element shell model that simulates the experimental behaviour closely is developed using ABAQUS finite element software, which is also used for further parametric studies. Using the three major variables as size parameters, a Frye–Morris type of equation has been proposed. Some calibration studies have also been carried out. Using the ultimate moment capacity, initial connection stiffness and the shape parameter obtained, a three parameter power model has also been proposed to represent the moment–rotation behaviour of the boltless connections.

The paper deals with the modelling of riveted joints in aircraft structures with Finite Element Method. Presented works were carried out within Eureka project No. E!3496 called IMPERJA. The goal of the IMPERJA project is to increase the fatigue life of riveted joints, which will lead to an increase of the aircraft service life, a smaller number of inspections and lower operation costs of an aircraft. The project assumed FEM modelling of the operating aircraft 's structure at three different complexity levels, namely considering the complete structure, a structural detail and a single riveted joint. The paper presents analyses of various rivet models and calculations of a structure and a riveted joint. In the first part examples of various models, at global and local level, were presented and usefulness of them was discussed, influence of the following simplification was analysed; • neglection of rivets in a model (elements are jointed continuously) • rivet as a rigid element (MPC) • neglection of contact phenomenon • neglection of secondary bending • neglection of residual stresses after riveting process The basis of the analysis was the asymmetric butt joint model with 14 rivets. The model which took into account secondary bending and contact phenomenon was analysed as well. The method of modelling residual stresses with temperature and thermal coefficient was used. In the second part, the example of analysis of riveted joint was demonstrated for a wing of PZL M28 Skytruck aircraft. It 's is a twin-engine, high-wing, cantilever monoplane of all-metal structure with maximum take-off and landing weight 7500 kg. A submodeling technique was used there. At first, part of the wing model, based on a CAD model, was built. It includes 7 ribs and 6 bulkheads between them. Dimensions of the model eliminate stress perturbation, connected with boundary conditions, in the area near the middle rib. It was a shell model. The boundary conditions were taken on a basis of operation data. Presence of rivets wasn't taken into account. Instead of this, parts were connected continuously (nodes were merged). The Linear model of material was used. The purpose of the part of the wing model was to gain accurate boundary conditions for next model of riveted joint on the middle rib. The behaviour of whole model is correct but stress distribution around rivets is not correct. A shell model of riveted joint was build. A boundary conditions were set on a basis of result from previous analysis. Forces, instead of displacements, were used, as boundary conditions, on account of a large stiffness difference between part models (part of wing and riveted joint model). The nonlinear model of material was used. A contact effect and secondary bending were taken into account. Thanks to that, phenomena around rivets were represented considerably better. Results from this analysis could be used as boundary conditions in a detailed calculation of one or few rivets with solid elements. Such a model was considered as well. The presented method allows to analyse phenomena that appear around a rivet in a real structure, during operation. Analyses were performed with MSC PATRAN, NASTRAN and MARC software.

The last decade has witnessed both quantitative and qualitative progresses in Shell Model studies, which have resulted in remarkable gains in our understanding of the structure of the nucleus. Indeed, it is now possible to diagonalize matrices in determinantal spaces of dimensionality up to 10^9 using the Lanczos tridiagonal construction, whose formal and numerical aspects we will analyze. Besides, many new approximation methods have been developed in order to overcome the dimensionality limitations. Furthermore, new effective nucleon-nucleon interactions have been constructed that contain both two and three-body contributions. The former are derived from realistic potentials (i.e., consistent with two nucleon data). The latter incorporate the pure monopole terms necessary to correct the bad saturation and shell-formation properties of the realistic two-body forces. This combination appears to solve a number of hitherto puzzling problems. In the present review we will concentrate on those results which illustrate the global features of the approach: the universality of the effective interaction and the capacity of the Shell Model to describe simultaneously all the manifestations of the nuclear dynamics either of single particle or collective nature. We will also treat in some detail the problems associated with rotational motion, the origin of quenching of the Gamow Teller transitions, the double beta-decays, the effect of isospin non conserving nuclear forces, and the specificities of the very neutron rich nuclei. Many other calculations--that appear to have ``merely'' spectroscopic interest--are touched upon briefly, although we are fully aware that much of the credibility of the Shell Model rests on them.

This paper will explore the human factors involved in automated aircraft to include the SHEL model, human centered approach, situational awareness and fatigue.  These examples will show how inter related they can be and how they can affect flying whether its general aviation or in military drones.  As defined by the Federal Aviation Administration (FAA), Human Factors is a “multidisciplinary effort to generate and compile information about human capabilities and limitations and apply that information to equipment, systems, facilities, procedures, jobs, environments, training, staffing, and personnel management for safe, comfortable, and effective human performance ("Role of Human Factors," 2014, p. 1).  Aircraft automation is designed to improve the operation of flight systems as it provides an enhanced safety environment and more precise vehicle control.  The research will explore the potential hazard conditions during automated flight and the various potential obstacles to relying on automated conditions. 
Keywords: automation, SHEL model, human centered approach, situational awareness and fatigue

AN ATLAS OF [N ii] AND [O iii] IMAGES AND SPECTRA OF PLANETARY NEBULAE Arsen R. Hajian, 1 Steven M. Movit, 1, 2 Denis Trofimov, 1, 3 Bruce Balick, 4 Yervant Terzian, 5 Kevin H. Knuth, 6, 7 Domhnull Granquist-Fraser, 8 Karen A. Huyser, 9 Andre Jalobeanu, 10 ...

Backbending properties of well-deformed (beta 0.25) nuclei at high spin are often described in terms of the Cranked Shell Model (CSM) [1]. However, weakly deformed and transitional N = 57 isotones around A 100 nuclei provide an excellent testing ground for the limits of the CSM approach, since these nuclei can be adequatley described at low spins as anharmonic vibrators [2,3]. With increasing spins however, alignment processes associated with rotational motion are obserbed, specifically assoated with crossing a a broken (h11/2) neutron pair. Somewhat paradoxically, the Coriolis effects which are associated with alignment processes in deformed nuclei are largest in systems with small deformations (beta0.15), and as such, nuclei in this region make excellent laboratories for probing the interface between vibrational and rotation motion [2-4]. In the current study [5], the near-yrast states of 101Ru were investigated via the fusion-evaporation reaction 96Zr(9Be,4n)101Ru at a beam energ...

This paper presents a unified formulation for the modelling of doubly curved composite shell structures. Via this approach, higher-order, zig-zag, layer-wise and mixed theories can be easily formulated. Classical theories, such as Love’s and Mindlin’s models, can be obtained as particular cases. The governing differential equations of the static linear problem are derived in a compact general form, tackling the difficulties due to the higher than classical terms. These equations are solved via a Navier-type, closed form solution. Shells are subjected to distributed and localised loadings. Displacement and stress fields are investigated. Thin and moderately thick as well as shallow and deep shells are accounted for. Several stacking sequences are considered. Conclusions are drawn with respect to the accuracy of the theories for the considered loadings, lay-outs and geometrical parameters. The importance of the refined shell models for describing accurately the three-dimensional stress state is outlined. The proposed results might be useful as benchmark for the validation of new shell theories and finite elements.

We discuss a theoretical formulation of shell model accounting for through-the-thickness stretching, which allows for large deformations and direct use of 3d constitutive equations. Three different possibilities for implementing this model within the framework of the finite element method are examined: one leading to 7 nodal parameters and the remaining two to 6 nodal parameters. The 7-parameter shell model with no simplification of kinematic terms is compared to the 7-parameter shell model which exploits usual simplifications of the Green–Lagrange strains. Two different ways of implementing the incompatible mode method for reducing the number of parameters to 6 are presented. One implementation uses an additive decomposition of the strains and the other an additive decomposition of the deformation gradient. Several numerical examples are given to illustrate performance of the shell elements developed herein.