Papers by Keyword: Tension

Abstract: In this paper, the implementation and testing of multilayer graphene/epoxy resin nanocomposites are discussed. Firstly, the epoxy resin hardener is mixed with the multilayer graphene, and then mixed with the main agent, then poured into the mold, and the low temperature cooling system is used. The curing time of the epoxy resin is slowed down, and the bubble is removed before the complete hardening by the vacuum defoaming method, and the mechanical properties such as tensile strength and toughness are compared with the pure epoxy resin after being sufficiently hardened. In this paper, we investigated the effect of multilayer graphene content on mechanical properties by using the tensile test and impact test. We discussed the effect of multilayer graphene content on the coefficient of elasticity of the multilayer graphene/epoxy resin composites at different stretching rates. And the toughness of the multilayer graphene/epoxy resin composites was evaluated by impact test. After the experiment, it was found that the stretching rate has a certain degree of influence on the grapheme/epoxy resin composite material. And that the addition of 2% multilayer graphene to epoxy resin had the best effect and could effectively improve the coefficient of elasticity and toughness.

Abstract: Many of the complex reinforced Autoclaved Aerated Concrete characteristics under shear and flexure are yet to be identified to employ this material advantageously and economically, as it has many advantages of low weight, fire resistance, acoustic and thermal insulation. It is observed in the article that under two-points loading system, diagonal cracks are usually the first cracks to be observed in the deep beam clear span. The diagonal cracks first are developed in relatively deep beams and the flexural cracks are first developed in shallower beam. The principal mode of failure in the deep beams having adequate reinforcement is diagonal tension cracking. The shear failure is a common type for all beams. This indicates a weak the bond strength between lightweight concrete and reinforcing steel. There are many factors affecting the bond strength between the lightweight concrete and reinforcing steel, where the compressive strength plays an important role in bond strength, and the bond strength is increased by increasing the compressive strength. The AAC beams have the potential to be an excellently energy-saving construction material and is believed to emerge as an alternative to traditional reinforced concrete beam in the near future. This is proved by the experimental analysis.

Abstract: The uniaxial tensile tests were conducted at different temperatures to explore the coupled influence of stacking fault energy (SFE) and short-range clustering (SRC) on the plastic deformation behavior of Cu-Ni alloys. The results demonstrate that the ultimate tensile strength and uniform elongation decrease with increasing temperature due to the competitive influence of SFE and SRC. Dynamic strain aging (DSA) effect is observed at 200 and 250°C, and such an effect becomes more notable with increasing Ni content. The occurrence of DSA effect is thought to be caused by pinning of moving dislocations by SRC and diffusing solute atoms. The plastic deformation mechanisms for Cu-Ni alloys is mainly governed by wavy slip of dislocations at different temperatures, since the SFE of Cu-Ni alloys are very high especially at high temperatures, and the effect of SRC can be nearly ignored.

Abstract: Nowadays, a change of material properties is evaluated on the basis of the results of "traditional" methods (for example, tensile testing and impact bending test). Unfortunately, "traditional" mechanical testing requires quite large samples, that leads to a damage of studied objects integrity. That is why testing with the application of compact samples, which allows converting obtained results into regular parameters, such as tensile properties and fracture resistance, was developed. Due to the novelty of this method, influence of different factors on testing results is understudied. Here arises the aim to study the influence of the level of accumulated damage on testing results. Regular changes of small punch testing tensile diagrams, depending on the number of worked out cycles, are under study in the present paper. Based on the study results, algorithm for determination of mechanical properties of steel 20 with different levels of cumulative fatigue damage with the application of compact samples was developed.

Abstract: In the article some considerations to optimize the cross-sections of prefabricated-monolithic combined reinforced bent elements are given. The analytical dependence that allows more economical design of the structures in question taking into account the strength and quantity parameters, as well as the geometric dimensions of the individual components of the prefabricated-monolithic section and their relationships is proposed.

Abstract: Nowadays a concept of a beam with a corrugated wall in construction mechanics does not exist. Such designs do and they are used in construction. Definition of the intense deformed condition of a beam with a corrugated wall is a relevant task. In this article the task of tension distribution nature assessment in the cross section of a beam in a corrugation height variation was discussed. The task was solved in the course of the numerical experiments with application of the finite element method (FEM). The problem was solved for beams with different shapes of the lines forming a corrugation. It was established that the geometrical form of a corrugation practically didn't influence the nature of tension distribution on a beam section and tension distribution on the cross section of beams with a corrugated wall depends generally on the corrugation height relation to its width.

Abstract: The article proposes applying energy from law deformation mechanics of the rigid body to deformation method for calculating the strength of reinforced concrete constructions with the use of diagrams illustrating the deformation of concrete and reinforcement. In terms of the energy theory of strength, concrete and rebar accumulate potential energy in the section of the construction component under stress; based on the contours of the diagram used in calculation it is possible to distinguish a stress diagram for concrete of the compressed zone. The value of the strains is equivalent to the force used for the deformation of the concrete specimen under stress (prism-or cylinder-shaped); the force is equal to the area used in the calculation of the normable diagram. The resolving balance equations are deduced with the use of the flat section hypothesis. The conditions of the stress balance in the section of the construction component are tested with the method of the successive approximation. The variable parameter of approximation is the construction component bending. General deformations (deflections) of the construction components are significantly higher than their limit stress values permitted for safe operation.

Abstract: The article is devoted to the investigation of the technology of the wood-glued structures manufacture with strengthening the supporting zones by a prepreg on the basis of the fiberglass and the glued oligomer with the addition of the carbon nanotubes (CNTs). The peculiarities of the wooden beams cross-sections have been presented. The main types of fiberglass have been reviewed. The article describes strengthening the supporting zones of wooden and glued-wood beams. The method of nanoparticles application in adhesive compositions to improve their physical mechanical properties has been considered. The technological process of manufacturing the glued-wood structure and its strengthening has been developed.

Abstract: This paper presents a constitutive relationship to describe the uniaxial response in statics of brick and mortar samples of Adobe, a traditional masonry whose components are made of sundried soil mixture reinforced with fibres. Only recently Adobe has been attracting scientific attention, primarily as a consequence of the dramatic failures these structures have suffered in regions prone to earthquakes. Furthermore, it possesses eco-friendly material properties which are attractive features for western countries forced to reduce the environmental impact of modern building industry. Nevertheless, the mechanical properties of Adobe are still largely neglected, especially with regards to the influence of soil mixture components. The study of the structural performance of masonry starts from the assessment of the material performance of its components. Thus, an extensive characterization campaign was performed by Delft University of Technology and the Military Engineering Laboratory of the Netherlands. Three types of bricks and one type of mortar with different mixture components proportions, were subjected to granulometry, moisture content, density tests and uniaxial compressive and three point bending tests. Predictive formulations for compressive and tensile strength and deformation values have been proposed by the authors. These relations include the dependency of mixture components and moisture content. In this paper, constitutive laws are developed for Adobe in pure compression and tension validated by experimental results. In compression, the force-displacement curves were interpolated according to several existing constitutive laws and the model originally developed by Priestley for concrete masonry elements was finally selected as best fitting. Despite the differences in terms of mechanical parameters, the analytical assessment revealed that the experimental force-displacement graphs of all the different types of bricks could be interpolated using the same model with the same calibrating values. Furthermore, the uniaxial response in tension was derived according to an inverse approach. A numerical model recently developed by the authors and calibrated with respect to the compressive and bending tests was used to simulate uniaxial tensile tests. Also in tension, a common trend among types was observed. The results of the constitutive modelling frames components of Adobe within the class of quasi brittle (geo) materials, with particular reference to concrete. This paper presents the experimental results of the tested samples and the related analytical and numerical modelling.

Abstract: To study microstructure and texture evolution of 2024 aluminum alloy sheet under different loading conditions, thermal tensile and compression experiments of 2024 aluminum alloy rolled sheets were carried out at temperatures ranging from 300 °C to 450 °C and under strain rates ranging from 0.001 s^-1 to 0.1 s^-1. During tensile deformation, the HABs of original grains are directly elongated until abruption. DRX process occurs during compression. Dislocations appear during deformation, migrate and accumulate into LABs, and then rotate into HABs to form new grain.The three-dimensional orientation distribution functions (ODFs) in different stress states were measured, with related texture types and distribution laws compared. According to ODFs with a constant φ₂, the deformation texture of {011} <100>Goss texture is gradually strengthened during thermal tension at high temperature and low strain rate (450°C/0.001s^-1). The deformation texture of {011} <100>Goss texture is weakened with the strain increasing. Furthermore, the increase of deformation temperature or the decrease of strain rate slows down the weakening process of {011} <100> Goss texture, which is attributed to the recrystallization behavior during tensile deformation. Besides, since the recrystallization process proceeds more completely during hot compression, it produces a quasi-random texture.