Advanced Materials Research Vols. 1025-1026

Abstract: For designing the wheelchair structure under the seat loading, the stresses and failure indexes in each ply of the composite laminate are obtained by the finite element analysis. Using the Tsai-Wu criterion and delamination criterion, the stacking sequence [0₄/90₄/45₄/-45]_s is the final optimal design for the wheelchair frame. On the contrary, the uni-directional laminates, i.e. [90₁₃] s, [45₁₃] s and [-45₁₃] s, are bad designs.

Abstract: Wood is a renewable source of structural material with high relative strength/weight, low energy production, which kidnaps and stores carbon in its production. The large use of wood is due to its special qualities as raw material for other products manufactured in residential construction or major works such as bridges, has been widely used in roofing for industrial and commercial buildings. Commercially there are limitations on the length of the wood, resulting from the extraction of tree trunks, thus requiring the adoption of binding elements is the use of self-tapping screws efforts required by side and which can be axial, shear, tensile or compression. Whereas in Brazil does not yet exist and the promising future of the product, this research aims to study the behavior of self-tapping screws together with Brazilian reforestation species of Pinus oocarpa and Lyptus (softwood and hardwood). Rothoblaas self-tapping screws had a good penetration in both woods without requiring pre-drilling, the species of Lyptus wood showed the highest values of strength and the inclination of the screws, at 45 degrees showed the best results on either species of wood.

Abstract: Secondary cast Al-Si alloys containing more of additions elements and forming various structural parameters (intermetallic phases). The optimization of structure parameters morphology is necessary because the mechanical properties depend on changes in morphology of eutectic Si and intermetallic phases in Al-Si cast alloy. This article describes changes of eutectic Si morphology after heat treatment T4 and T6. The morphology changes were observed using combination different analytical techniques - light microscopy (upon black-white etching) and scanning electron microscopy - SEM (upon deep etching). For the experiment was used recycled (secondary) aluminium cast alloy AlSi9Cu3.

Abstract: The work of this paper proposes a new technique for estimating and predicting erosion corrosion rate for laminar and turbulent flow in pipes. The technique depends on the neural networks Artificial Intelligent algorithms. Based on experimental results, which was applied to A 106 carbon-steel pipes, the networks are trained. Four velocities (Reynolds numbers) are used for laminar and four for turbulent regimes. The experiments also used seawater containment three different concentrations of sand. For each experiment the iron losses were measured six times in three hours’ time interval. The proposed estimating/predicting system managed to find values between the readings as well as predict the behavior of the erosion corrosion rate for extra three hours. The estimated/predicted results have been developed to find the transient zone between the Laminar and Turbulent flow regimes and investigating its effects on the erosion-corrosion behavior.

Abstract: The Necessity of taking into account the ability of cold-formed steel thin-walled profiles to gradually change its cross section shape proportionally to the load acting on it is considered. Free torsion constants Jt value for cold-formed profiles is justified. Underestimation of beam torsion due to ignoring of the cross-section contour deformation is assessed. The thin-walled Z and C-shaped cold formed steel sections recently are becoming more and more popular in the constructions of low-rise buildings. A characteristic feature of cold-formed thin-walled profiles in these structures is the need to consider not only the longitudinal and bending deformations, but also the deformations of torsion. Presently there are two approaches to analysis of structures of thin-walled cold-formed steel sections. One of them is based on the thin-walled beam theory designed by V.Z. Vlasov, another one is based on the super-critical load-carrying capacity theory. In the first approach the contour of the cross-section is non-deformable, in the second caseanalysis is carried out on the basis of a reduced cross-section, caused by local buckling of the compressed cross-section elements. Both approaches do not take into account the ability of cold-formed steel thin-walled profiles to change itscross section shape proportionally to the load acting on it. In this connection it is necessary to conduct theoretical and experimental studies of the cross-section deformation effect on behavior of cold-formed steel profiles.First of all,it is important to find out the range of section-length characteristics for cold-formed profiles in which the fact of not taking into account of contour deformation of the cross-section leads tothe significant, from an engineering point of view, error in the calculations. Also it is needed to estimatehowload types and connections applied on cross section influence on cross-section form changing.

Abstract: Gelcasting is a widely
used method for manufacturing ceramic components. Currently the research on drying process is limited to qualitative analysis for drying process. In order to reveal the mechanism of the gelcast bisque’s drying process, the one-dimensional dynamics model for drying process has been formulated, based on the microscopic quantitative description of the evaporation process and mass transferring process through the gelcast bisque. Then the model has been modified with the consideration of the capillarity effect and the bisque’s drying shrinkage influence. By comparing with the experimental results the one-dimensional dynamic model of drying process can be proved to accurately describe the bisque’s drying process.

Abstract: Copper beryllium (CuBe)is materials that are widely used for mechanical applications. In this paper,the use of copper beryllium for cantilever spring of a vibration sensor will beinformed. Cantilever spring plays important role in a vibration sensor, becauseit transfers vibration energy of the measured system into the sensor.Therefore, it is important to know the dynamic characteristics of thecantilever spring. An optical method, called Levitation Mass Method (LMM), isproposed to measure the dynamic characteristic of the cantilever. In themethod, the force of cantilever spring is measured as the inertial force workedon a mass. A pneumatic linear bearing is used to realize a linear motion withsufficiently small friction acting on the mass, i.e., the moving part of thelinear bearing. The inertial force acting on the mass is calculated from thevelocity of the mass, and the velocity is determined highly accurately by meansof measuring the Doppler shift frequency of the laser light beam reflecting onthe mass using an optical interferometer. It is shown that the proposed methodshows the dynamic characteristic of the vibration sensor well.

Abstract: The use of appropriate forming processes allows to obtain materials of required quality, which are fulfill different technological criteria. The basic type of properties, which are fundamental for material use in specific operating conditions, are mechanical ones. They directly depend on the microstructure. Model of microstructure evolution allows for multi-criteria optimization of technological processes in view of final product properties, taking into account technological conditions. The objective of this study is development a multiscale model of microstructure evolution during the shape rolling process and presentation the finite element modeling results for 5 mm round bars rolled in diamond, oval and round grooves. The model allows to obtain parameters of technological process (by means of finite element model - FEM) and microstructural parameters (with use cellular automata - CA). FEM is used for design and selection of the grooves on the first stage [1] and for the simulations of shape rolling process in macro scale on the second stage. The next stage includes the use of FEM modeling results for simulation of microstructure evolution by cellular automata. The article presents the simulation results of shape rolling (5 mm round bars in diamond - oval scheme) with used the finite element method. This stage is the second one in the calculation sequence of the developed multiscale model. The basic process parameters such as temperature, components of strain and strain rate tensors and strain rate intensity at arbitrary points of deformed material are the modeling results. Selected FEM simulation results are presented in the article.

Abstract: One of the problems that often occurred during orthodontic treatment is bracket failure. This is usually the result either of the patient’s accidentally, applying inappropriate forces to the bracket or of a poor bonding technique. Thus, a significant number of teeth have to be rebonded in an orthodontic practice. Objective: The aim of this study was to evaluate the in vitro initial repeated shear bond strength of the three adhesive systems at two and five minutes after placement of a bracket. Materials and Methods: The three bonding agent adhesives are System1+, Rely-a-bond, Unite. Two hundred and forty human premolar teeth were divided into two groups, a control and an experimental group. Each group was further divided into three subgroups for bonding brackets with the three different adhesives. Only the teeth in the experimental group were sequentially bonded and debonded two times with the same adhesive. The teeth in control and experimental groups were tested for shear bond strength (at two and five minutes after the bracket was bonded) with an Instron testing machine. Results: The studies were found that : (1) there were differences between the shear bond strength of each adhesive in the control and experimental group. Unite had the highest shear bond strength followed by Rely-a-bond and System1+ at two minutes and five minutes, (2) the experiment group ( rebonded brackets) had higher shear bond strength than control group and Unite had in significant difference (p<0.05) of initial repeated bond strength with System1+ and Rely-a-bond at two minutes and five minutes and (3) there were mostly significant difference (p<0.05) between repeated shear bond strength at two minutes and repeated shear bond strength at five minutes. Conclusion: There were significant difference of the initial repeated shear bond strength of each adhesive. The orthodontists should be aware of applying force for tooth movement into the repeated bonding brackets.

Abstract: In this paper, the finite element analysis (FEA) of the fine blanking process was conducted for the seat recliner plate holder of recreation vehicle. Because the plate holder was a complex part with the various dimple shapes, it was formed and blanked with a three-station progressive fine blanking tool. The fine blanking tool was optimally designed, manufactured and performed the fine blanking experiments. The shear surface of the outer contour, the stress and strain of the part, and the loads of the tool elements were estimated by the results of the fine blanking simulation. Because the plate holder samples from fine blanking experiments had the good accuracy of the dimples’ position and dimension, it would be noticed the fine blanking simulation was conducted without error.