Space Lattice Structures Research Articles

Mechanical behavior of single-layer reticulated shell connected by welded hollow spherical joints with considering welding residual stress

The welded hollow spherical joints (WHSJ) have been widely used in space lattice structures. There have been many researchers investigating the mechanical behavior of WHSJ. But few literatures that considered the influence of welding residual stress can be found, let alone the integral structure analysis considering welding residual stress. In this paper, welding residual stress of WHSJ was firstly obtained by conducting thermal elastic–plastic analysis. Then, influence of welding residual stress on mechanical behavior of WHSJ was investigated. Secondary development of finite element software ANSYS was conducted, and the welding residual stress was applied as initial load. Finally, the mechanical behavior of a single-layer reticulated shell was investigated by considering residual stress. By using the method proposed in this paper, the simulation of welding process needs to be conducted only once to get the residual stress field of the integral structure. Amazing computational cost was avoided, and it makes it possible to investigate the influence of welding residual stress on integral structures.

Max von Laue and the discovery of X‐ray diffraction in 1912

From today’s perspective, only a few discoveries are regarded to be as exciting and as ground-breaking as the discovery of X-ray diffraction by crystals. “The undersigned are engaged since 21 April 1912 with experiments about the interference of X-rays passing through crystals,” a one-page report announced the discovery to the Bavarian Academy of Science. It was signed by Walter Friedrich, Paul Knipping and Max Laue (then still without the “von”) and deposited by Arnold Sommerfeld on 4 May 1912 in order to ascertain the discovery before it was officially communicated in the form of an elaborate paper. “The guiding idea was that interferences arise in consequence of the space lattice structure of the crystals, because the lattice constants are ca. 10 times greater than the conjectured wavelengths of the X-rays.” A simple drawing sketched the experimental arrangement. As evidence for the discovery some exposures were attached.1

Reliability and Sensitivity Analysis of Double-Layer Spherical Latticed Shell

In the reliability and sensitivity analysis of space structures, the traditional reliability index approach (RIA) becomes much more difficult to convergence in some cases, even divergent. To overcome these shortcomings, the Performance Measure Approach (PMA) is introduced to deal with the above problem in space lattice structures. The reliability and sensitivity of four double-layer spherical latticed shell are discussed. Numerical results show that PMA is robust and efficient. With the decrease of height-to-span ratio of reticulated shell, the maximal vertical deformation gradually increases, which is the reason why the reliability index inclines markedly. Concentrated loads, which surrounded the node where the maximal deformation occurs, markedly influence the maximal deformation.

Species doublers as super multiplets in lattice supersymmetry: exact supersymmetry with interactions for D = 1 N = 2

We propose a new lattice superfield formalism in momentum representation which accommodates species doublers of the lattice fermions and their bosonic counterparts as super multiplets. We explicitly show that one dimensional N=2 model with interactions has exact Lie algebraic supersymmetry on the lattice for all super charges. In coordinate representation the finite difference operator is made to satisfy Leibnitz rule by introducing a non local product, the ``star'' product, and the exact lattice supersymmetry is realized. The standard momentum conservation is replaced on the lattice by the conservation of the sine of the momentum, which plays a crucial role in the formulation. Half lattice spacing structure is essential for the one dimensional model and the lattice supersymmetry transformation can be identified as a half lattice spacing translation combined with alternating sign structure. Invariance under finite translations and locality in the continuum limit are explicitly investigated and shown to be recovered. Supersymmetric Ward identities are shown to be satisfied at one loop level. Lie algebraic lattice supersymmetry algebra of this model suggests a close connection with Hopf algebraic exactness of the link approach formulation of lattice supersymmetry.

Dynamic equivalent continuum modeling of beamlike space lattice structure

Dynamic equivalent continuum modeling of beamlike space lattice structure

Spectral element modeling for extended Timoshenko beams

Periodic lattice structures such as the large space lattice structures and carbon nanotubes may take the extension-transverse shear-bending coupled vibrations, which can be well represented by the extended Timoshenko beam theory. In this paper, the spectrally formulated finite element model (simply, spectral element model) has been developed for extended Timoshenko beams and applied to some typical periodic lattice structures such as the armchair carbon nanotube, the periodic plane truss, and the periodic space lattice beam.

Modeling of Triangular Lattice Space Structures with Curved Battens

Techniques for simulating an assembly process of lattice structures with curved battens were developed. The shape of the curved battens, the tension in the diagonals, and the compression in the battens were predicted for the assembled model. To be able to pe rform the assembly simulation, a cable-pulley element was implemented, and geometrically nonlinear finite element analyses were performed. Three types of finite element models were created from assembled lattice structures for studying the effects of desi gn and modeling variations on the load carrying capability. Discrepancies in the predictions from these models were discussed. The effects of diagonal constraint failure were also studied.

A constraint solver for discrete lattices, its parallelization, and application to protein structure prediction

AbstractThis paper presents the design, implementation and application of a constraint programming framework on 3D crystal lattices. The framework provides the flexibility to express and resolve constraints dealing with structural relationships of entities placed in a 3D lattice structure in space. Both sequential and parallel implementations of the framework are described, along with experiments that highlight its superior performance with respect to the use of more traditional frameworks (e.g. constraints on finite domains and integer programming) to model lattice constraints. The framework is motivated and applied to address the problem of solving the protein folding prediction problem, i.e. predicting the 3D structure of a protein from its primary amino acid sequence. Results and comparison with performance of other constraint‐based solutions to this problem are presented. Copyright © 2007 John Wiley & Sons, Ltd.

Horizontal Earthquake Loading and Linear/Nonlinear Seismic Behaviour of Double Layer Barrel Vaults

Lattice space structures are one of the most common choices for covering large areas. These structures are also used as temporary shelters after strong and destructive earthquakes. Nevertheless, there are not enough available research results on the seismic behaviour of these structures. In the current work, the dynamic characteristics of the double layer barrel vaults are studied. Linear and nonlinear behaviour of the barrel vaults are investigated. It is shown that the barrel vaults are vulnerable to earthquakes and show brittle behaviour and therefore need to be designed carefully. For simplifying the assessment procedure of the earthquake equivalent loading on the barrel vaults some formulae are presented.

Analytical evaluation of lattice space structures for accuracy

Analytical evaluation of lattice space structures for accuracy

Teaching Lattice Space Structures at Rutgers University, USA

Teaching Lattice Space Structures at Rutgers University, USA

Continuum plate finite elements for vibration analysis and feedback control of space lattice structures

A variety of research projects are being pursued involving the dynamics and control of large space platforms made up of lattice-type truss structures. A method involving finite element modeling of an equivalent continuum formulation based on matching the strain energy and kinetic energy is developed. The method is shown to give modal results consistent with those obtained using detailed finite element modeling of the space lattice structure, even for structures with fairly small numbers of repetitions of an identical unit cell. Feedback controllers designed using reduced system models derived from these modal results using Modal Cost Analysis are shown to perform as well as controllers designed using the detailed analysis results.

Waxes: Colloidal properties and systems

AbstractColloidal systems formed by waxes with nonpolar organic solvents, in particular white spirit are discussed. The four principal wax/solvent systems, which are semisolid at room temperature, are termed paste, optimum paste, gel, and mixture‐mass. In their customary use, the terms paste and gel have slightly different meanings. Wax paste represents a crystalline, two‐phase system, a solid space lattice structure of paraffin wax crystals (mechanically not very strong), the interstices of which are filled with saturated paraffin wax solution (called free solution, because it can be separated by mechanical pressure). It is characterized by opacity, poor solvent binding, and low solvent absorption (i.e., low mass hardness). During solvent evaporation, which is of a high rate, it exhibits blooming, creeping, and drying‐up phenomena (subsiding from top to bottom in the evaporation vessel); the residue is a carpet of wax crystals. The paraffin wax possesses no swelling capacity. Wax gel may be regarded almost a one‐phase system, consisting of particles of colloidal dimensions. There is no (rigid) structure and no free solution. (Genuine ozokerite and high‐grade microcrystalline wax, both refined, are insoluble in white spirit at room temperature, but exhibit limited swelling.) The gel may be described as a multitude of swollen particles of microcrystalline wax or of most minute droplets of solvent isolated by films of wax. The gel has translucency, excellent solvent binding, and low solvent absorption (due to the lack of a rigid structure). On evaporation, which proceeds at a very high rate, it exhibits shrinking (top‐to‐bottom and towards the mass‐center), lack of blooming, and creeping; the residue is a nonporous, shrunken wax slab (taking the shape of the evaporation vessel). The mixture‐mass system consisting of two or more phases can be considered a random accumulation of comparatively coarse particles of carnauba (or another ester) wax held together by mechanical support; the comparatively wide interstices contain waxless solvent. The waxes concerned are little soluble to completely insoluble in white spirit at room temperature; there is no swelling. As in the case of a paste, a mixture‐mass contains a free liquid phase. It is characterized by pronounced opacity, as a rule very poor solvent binding, and absorption. Evaporation proceeds at a high rate often without blooming and, as a rule, without creeping. It exhibits the drying‐out phenomenon (solvent loss by almost constant outer volume); the residue is spongelike and friable. Optimum paste is virtually a one‐phase system of the border region crystalline/colloidal and results from a mixture of paraffin wax with an optimum amount of microcrystalline wax or ozokerite resulting in optimum solvent retention. It is characterized by moderate opacity, excellent solvent binding, and somewhat increased solvent absorption. On evaporation, the rate of solvent loss is extremely low (i.e. there is optimum solvent retention); drying‐up is very much slowed down. There is neither blooming nor creeping, and the evaporation residue is a dense wax slab, showing the contours of the evaporation vessel; there is no shrinking. The theory of retention is also discussed.