Key Engineering Materials Vol. 684

Abstract: Here results of computer analysis of sinking pass of aluminum alloys in the one and two dies are widely used in aircraft construction and engineering. As a method of computer simulation of finite element method used in the program DEFORM - 2D.

Abstract: The dimensions calculation methods of one-channel dies operating corbels for solid profiles pressing are described, these methods are based on similarity theory and dimensional analysis. According to these methods, setting dimensions of the operating corbel on the K profile section, it is possible to calculate operating corbels dimensions on each other section of the i profile, depending on their position relative to the die center, ensuring the outflow evenness. Calculation example of the die operating corbels for the pressing of the ribbed profile made of AV alloy is given.

Abstract: In this article we perform comparative analysis of the criteria of fracture during blade machining simulation, characterized by high intensity of the strain rate (about 10^-6 s^-1). For each 3D virtual experiment a milling processing model has been developed in DEFORM software package. The character of chip segmentation during the simulation was determined the accepted failure criterion. The adequacy of the model was evaluated by full-scale experiment based on geometry of real chips.

Abstract: In this paper was conducted the dichotomous principle analysis, which based on the results comparability of calculation method and the computer simulation results of forming double curvature sheet shells using new scheme stretch forming and program PAM-stamp. The new scheme involves initially perform shaping the central part of the shell with the press jaws of the straight line. Then press clips installed on the contours, which corresponding with curves of stretch die end sections, and performed extension stretch forming up to a point. The results of the calculation method allows to compare the formation stage and extension stretch forming on the results of computer simulation and quickly find the practical applicability of the new scheme extension stretch forming on modern stretch forming press such as FEL. Key words: extension stretch forming process, double curvature shell, computer simulation results, calculation method, stretch forming press FEL.

Abstract: The influence of temperature, strain rate, and sheet thickness on the mechanical properties of twin-roll cast, rolled and heat-treated AZ31 was investigated under tensile loading from different directions (0°, 90°). To assess the forming behaviour of different sheet thicknesses (0.6 mm, 1 mm), tensile tests were performed with an electromechanical testing device between 20 °C and 300 °C at strain rates of 10⁻⁴ s⁻¹ and 10⁻² s⁻¹. With rising temperature, the flow stress decreased while the elongation to failure (A₈₀) increased, which may be related to the enhanced dislocation motion and the activation of additional nonbasal slip systems at T > 200 °C. It can be seen that the anisotropy of flow stress and elongation to failure was influenced by the temperature, the strain rate, and the sheet thickness.

Abstract: The deformation behavior of 1565ch alloy under the plane-strain conditions in the temperature range of 350–490 ^оС and strain rates range of 0,1–10 s^-1 is studied. The expression for steady flow stress as the functions of temperature of deformation and strain rate is obtained. It is established that 1565ch alloy with zirconium addition shows higher strain resistance and less tendency to dynamic and static recrystallization than AMg6.

Abstract: Magnesium and magnesium alloys offer high potential as lightweight materials. Current works are mainly focused on the metal forming technologies and material development for sheet and strips to provide magnesium flat products for industrial applications. However, the technology for the production of magnesium long products for fasteners or other connecting elements is exclusive the extrusion process. A cost-efficient alternative can be the caliber rolling technology for magnesium rods and wire with regard to refined microstructure and specific required properties. But this whole process is rarely applied up to now and all material-specific as well as deformation relevant basics must be developed and additionally validated under industrial conditions. This paper gives the overview for a magnesium-specific wire rolling technology under consideration of chemical composition (AZ31, AZ61, AZ80) and their influence to final mechanical properties in correlation with the microstructure evolution along the whole process line. Therefore, the process-and material-dependent microstructural evolution during rolling process was investigated. The structural constitution is detailed by the grain size and the precipitation conditions. For the determination of the mechanical properties hardness measurement as well as tensile testing was carried out. To preliminary design and determine the material flow, the temperature distribution, and the logarithmic strain, a commercial numerical simulation tool was applied on base of the implemented material-specific deformation and recrystallization behavior. Hence, it was possible to design a magnesium specific caliber sequence for the production of fine-grained magnesium wires with Ø 8 mm and excellent mechanical properties.

Abstract: The invariant characteristics of stress state arising on the sheet metal forming operations are considered. Using the trigonometric presentation of stresses, the stress state is constructed. In this case the trajectories of principal stresses are presented by the help of the arcs of circles, that confirms the nonmonotonicity of the processes of deformation.

Abstract: Magnesium and its alloys have high potential for lightweight applications in the automotive and aerospace industries. In order to design parts for new applications with optimized mechanical properties and higher, more economic production rates, the forming limit behaviour of thin sheets (t < 1.0 mm) has to be known for different temperatures and loading rates. In this study, forming limit curves of 0.8 mm thick AZ31 sheet were measured for deformation at 200 °C and 250 °C and at loading rates of 1 mm/s and 10 mm/s with the Nakajima test. The investigations showed that an increase in temperature from 200 °C to 250 °C tends toward higher forming limit values for all stress states. In contrast, an increase in the loading rate from 1 mm/s to 10 mm/s induces a reduction in formability. It can be seen that the temperature, loading rate, and stress state influence the force-distance curves, the distribution of the local major strains, and the sheet thickness reduction.