Papers by Keyword: Plastic Properties

Abstract: The study reveals the effect of Mn and Mg content on mechanical and technological properties during the bending of thin sheets of aluminum alloy 3005. For experimental research the ingots were cast through an out-of-furnace refining unit, homogenized at a temperature of 590°C, during 6 hours. Further ingots were hot rolled to a thickness of 3.5 mm and subsequently cold rolled into sheets of thickness 0.33 and 0.25 mm. Annealing of rolls was provided at temperatures 230...285°C for 1.5 hour in air-circulation annealing furnaces with a protective atmosphere and on a continuous heat treatment line. The change in the tensile strength, yield stress, elongation as a dependence on the content of alloying elements and annealing modes was shown. Technological properties were evaluated by performing bend tests. It has been established that an increased content of magnesium and manganese in the AA3005 alloy results in lower values of the elongation for all annealing temperatures. Annealing in the air-circulation annealing furnaces resulted to higher plasticity values and lower values of strength compared to annealing at continuous heat treatment line for all annealing temperatures and magnesium and manganese temperatures. The plasticity of samples 0.25 mm thick raises evenly throughout the annealing temperature range. For specimens 0.33 mm thick, the effect of the magnesium and manganese content, as well as the type of heat-treatment equipment on the samples’ plasticity during annealing is more pronounced than for samples 0.25 mm thick. In sheet samples from the AA3005 alloy annealed on continuous heat treatment line, with an increased content of magnesium and manganese, cracks are observed at the inflection point for both thicknesses. When annealing in air-circulation annealing furnaces, cracks are not observed for both increased and reduced magnesium and manganese content.

Abstract: Analytical models and the basic preconditions for analysis of concrete and reinforced concrete structures should be established based on actual plastic properties of concrete and reinforcement, as well as consideration of presence of cracks in the concrete. It is known that the relationship between stress and strain in reinforced concrete is significantly different in the stage of work with cracks and without them. Development of computational method opens wide prospects in this direction. In this work the calculation of strength and definition of forces in constructive elements of structure from operational loadings are made on the basis of the finite element method. Analysis is carried out with the use of quadrangular isoparametric and beam elements by the method of level-by-level plasticization. Analytical model contains the nonlinear properties of concrete and reinforcement. Method and algorithm of calculation have been developed taking into account of real stress-strain diagrams from experiment. Method and algorithm of calculation of reinforced concrete designs include the limiting condition of deformation on the basis of known stress-strain diagram both for reinforcement and concrete. An example of analysis involving a tunnel structure for an underground station to determine internal forces using the proposed method was shown.

Abstract: Actuality of study of the problem of longitudinal crack formation along reinforcement taking into account concrete nonlinear strain is pointed out in this article. It is known that at collaboration of steel and concrete plastic strains occur in concrete surrounding bar. Previously, in the work [6], solution on determination of splitting cracks at elastic work of concrete in the area of active bond to steel was proposed. In this article, theoretical solution on determination of longitudinal cracks both in supporting area and in the area of collaboration of steel and concrete between cracks along element is suggested. For establishing equations taking into account inelastic work of concrete, the theory of plastic properties suggested by G.A. Geniev was used. Component stress-strain relation is recorded by analogy with studies performed by G.A. Geniev and N.N. Malinin. At that, design dependencies are linked with normative factors of concrete, such as concrete ultimate tensile strength, Poisson ratio and concrete elastic strain ratio at stretching. All this allowed to significantly simplify the use of expressions offered.

Abstract: New technology of micro-jet welding could be regarded as a new way to improve plastic properties of welds. The main purpose of that paper was analysing of plastic properties of welds made by MIG welding method with micro-jet cooling. The main reason of it was investigate possibilities of getting better plastic properties of welds made by MIG welding method with micro-jet cooling than plastic properties of welds made by ordinary welding method. It is possible for steel because higher amount of acicular ferrite (AF) in weld metal deposit (WMD) is obtained in MIG welding method with micro-jet cooling in relation to ordinary welding method (example: MIG welding method without micro-jet cooling). Moreover, it is possible to steering of weld structure and properties of the weld. During research Erichsen cupping tests and bending tests were carried out for welds made by MIG welding method with micro-jet cooling and ordinary welding method (MIG). Different kind of cooling gases were used to weld cooling. In this case comparison of plastic properties for different cooling gases was done. High amount of acicular ferrite influences positively on plastic properties. Higher values of plastic parameters were observed for welds made by MIG method with micro-jet cooling than for ordinary welding method. Different plastic properties were obtained for different cooling gases. In this research welds made by new method of welding (welding with micro-jet cooling) were compared witch welds made by ordinary welding method. New method of welding is very promising and capable of industrial application, mainly due to the significant improvement of weld properties and quality. That research was made only for steel welding with using MIG welding method. Another method of welding and another material were not tested. Other methods of welding have not been tested, but it is suspected that similar phenomena are taking place. Practical implications MIG method with micro-jet cooling it is way to get better plastic properties of welds in relation to welds made by ordinary welding method. It is very important because it could be used to steering of mechanical properties of welded constructions. This may have a positive impact on the parameters of the welding process (example: welding speed) and the quality of welded joints.

Abstract: The aim of this paper is to identify, in addition to elastic properties, inelastic properties of tiny aluminium foam cell walls that can be directly deduced from the loaddepth curves of spherical indentation tests using formulations of the representative strain and stress. Constitutive parameters related to plastic material with linear isotropic hardening, the yield point (122 ± 17 MPa) and tangent modulus (950 ± 377 MPa), were obtained in this work. Spherical indentation and uniaxial tension experiments have also been performed on a standard aluminium alloy EN AW 6060 to explore the accuracy of the analytical models used to predict the uniaxial stressstrain in wide strain ranges. Some deviations received from different tests arose and, therefore, their effect on the evaluation of inelastic properties was discussed.

Abstract: Steel alloyed by nickel, chromium and molybdenum reach according to normative standards (EN) yield point about 900 MPa and contraction about 25% after heat treatment. Authors of this paper noticeably increase the strength properties of that steel without changes in plastic properties with using of electroslug remelting refining technology (ESR). Subject of research are forgings of very large mass and dimensions. The forgings are used in special armament technology as (tank gun barrels). Very negative influence on mechanical properties of final product has content of nanodimensioned impurities.

Abstract: The paper presents the results of studies on the effect of the A390.0 (AlSi17Cu5) alloy overheating to a temperature of 920°C and modification with phosphorus (CuP10) on the resulting mechanical (HB, R_m, R_0.2) and plastic (A₅ and Z) properties. It has been shown that, so-called, "time-thermal treatment" (TTT) of an alloy in the liquid state, consisting in overheating the metal to about 250÷300°C above T_liq, holding at this temperature and rapid cooling, refines the structure and improves the mechanical properties. It has also been found that strong overheating of alloy above T_liq "enhances" the process of modification, resulting in the formation of fine-grain structure. The primary silicon crystals uniformly distributed in the eutectic and characteristics of the α (Al) solution supersaturated with alloying elements present in the starting alloy composition (Cu, Fe) provide not only an increase of strength at ambient temperature but also at elevated temperature (250°C), which is of particular importance for the automotive applications, especially as regards cast pistons operating in IC.

Abstract: The research of the nano-mechanical properties on mono-crystalline silicon by nanoindention technology is reported in this paper . Using the calculation method given by Oliver and Pharr, the hardness and the elastic modulus of mono-crystalline silicon are gained from the load-penetration depth curve. The simulation on mono-crystalline silicon in the plastic phase is carried out by ABAQUS. Based on the bilinear constitutive law and approximate relationship between the hardness and the yield strength, the obtained load-penetration depth curve through the finite element method is compared with the materials actual load-penetration depth curve and good correlation is achieved.