Effect of material, geometry, surface treatment and environment on the shear strength of single lap joints

The single lap joint is the most studied type of adhesive joint in the literature. However, the joint strength prediction of such joints is still a controversial issue as it involves a lot of factors that are difficult to quantify such as the overlap length, the yielding of the adherend, the plasticity of the adhesive and the bondline thickness. The most complicated case is that where the adhesive is brittle and the overlap long. In any case, there is still a problem that is even more difficult to take into account which is the durability. There is a lack of experimental data and design criteria when the joint is subjected to high, low or variable temperature and/or humidity. The objective of this work is to carry out and quantify the various variables affecting the strength of single lap joints in long term, especially the effect of the surface preparation. The Taguchi method is used to decrease the number of experimental tests. The effect of material, geometry, surface treatment and environment is studied and it is shown that the main effect is that of the overlap length. In order to quantify the influence of the adhesive (toughness and thickness), the adherend (yield strength and thickness), the overlap, the test speed, the surface preparation and durability on the lap shear strength, the experimental design technique of Taguchi was used in the present study. An experimental matrix of eighteen tests was designed and each test was repeated three times. The influence of the eight previously-mentioned variables could be assessed using the statistical software Statview®. In this paper a simple predictive equation is proposed for the design of single lap joints

Numerical simulations of adhesive squeeze flow: A review

Debonding on demand structural adhesives is becoming a relevant topic for, in particular, recycling strategy issues. A debonding methodology has been developed by the FEUP using Thermally Expandable Particles (TEP). In order to enhance the properties of the material, it is expected to control the distribution of the TEPs in the uncured adhesive. After dosage and mixing, the adhesive is applied manually or automatically on a substrate. At this point starts the fluid structure interaction (FSI), where the substrates are approached and fixed before the last step, when the adhesives becomes solid, by the process of curing. To optimize the on demand debonding, it is first necessary to control the distribution of the fillers in this uncured phase. We are interested here in evaluating the different numerical methods that are used or could be used to simulate the approach of substrates and the squeezing process of charged uncured adhesive. Grid-based numerical methods are widely used for fluid simulations, either using Lagrangian or Eulerian reference frame, including the finite difference method (FDM), finite volume method (FVM) or the finite element method (FEM). In this study, we also consider the Smooth Particle Hydrodynamics (SPH) method which is meshfree method associated with particulate discretization of the matter and the movement. The knowledge of these methods allows addressing the squeeze flow problem in order to obtain the final distribution of the adhesive and inclusions in the joint

Mygalomorphae spiders (Araneae) recorded by the Sistema de Notificação de Animais Peçonhentos (SINAP) in the state of Paraná

ABSTRACT Despite their large size and intimidating appearance, most mygalomorph spiders do not cause severe envenomation in Brazil. “Programa Estadual de Vigilância de Acidentes por Animais Peçonhentos da Secretaria de Estado da Saúde do Paraná”, through the “Sistema de Notificação de Animais Peçonhentos” (SINAP), documents the occurrence of synanthropic species captured by the public and reported to municipal health services. In this study, we present a list of the mygalomorph species received by Secretaria de Saúde do Estado do Paraná (SESA) and their distribution across the state of Paraná, based on the SINAP reports. A total of 575 mygalomorph specimens were identified, originating from all 22 Regional Health Centers (RS) of SESA-PR. We identified species of four families: Actinopodidae (on species: Actinopus itapitocai); Dipluridae (1 species: Diplura catharinensis; Pycnothelidae (two species: Psalistopoides emanueli, and P. fulvimanus); and Theraphosidae (10 species in four genera: Acanthoscurria paulensis, Eupalaestrus campestratus, Grammostola actaeon, Pterinopelma longisternale, Tekoapora wacketi, Vitalius dubius, V. lucasae, V. paranaensis, V. sorocabae and V. vellutinus). Of the aforementioned species, Vitalius paranaensis has the widest distribution, occurring in all Regional Centers of Health except Paranaguá. The other most frequently collected species were Pterinopelma longisternale, Vitalius sorocabae, and Psalistopoides emanueli. In total, the 575 records resulted in only 12 accidents. The results highlight the broad distribution of some species; contributes to the identification of the main species encountered by the population and reported to SINAP in Paraná; and helps to bring attention to the low number of accidents caused by these large-sized spiders

A recursive theta body for hypergraphs

The theta body of a graph, introduced by Grötschel, Lovász, and Schrijver (in 1986), is a tractable relaxation of the independent-set polytope derived from the Lovász theta number. In this paper, we recursively extend the theta body, and hence the theta number, to hypergraphs. We obtain fundamental properties of this extension and relate it to the high-dimensional Hoffman bound of Filmus, Golubev, and Lifshitz. We discuss two applications: triangle-free graphs and Mantel’s theorem, and bounds on the density of triangle-avoiding sets in the Hamming cube

Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS

The chi_b(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb^-1, these states are reconstructed through their radiative decays to Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes. This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table, corrected author list, matches final version in Physical Review Letter