Seznam abstraktů 2022: POSTEROVÁ SEKCE B

The paper deals with the design of the technology for the production of the cover stamping to achieve the minimum cost of one piece of the produced component. By calculation, the minimum values of the radius of curvature of the edge of the draw die and the edge of the draw punch were determined to eliminate the calibration operation. The shape and dimensions of the blank for the cover stamping were determined by several methods and then compared. Simulations of the drawing process allowed the locations with the greatest thinning to be analyzed and the drawability of the stamping from each alternative of the blank shape to be verified. The results of the simulations showed the highest suitability of the blank determined by the Autodesk Inventor program and also by the BSE module in Dynaform. The simulation results further demonstrated the necessity to increase the radii of curvature of the drawing edge of both the draw die and the draw punch to a value of 4 mm, which allows the fabrication of a defect-free cover stamping without the need for subsequent calibration. The use of the simulation program in the technological preparation phase of production allowed one to optimise the drawing process by a suitable design of the shape of the blank and also allowed one to design a change in the shape of the stamping which eliminated the formation of cracks at its bottom during drawing.

The tests were carried out on high-Mn of 27Mn-4Si-2Al-Nb type steel. The steel was solution heat-treated at different temperatures in a range from 900 to 1200°C. The tensile testes has performed at room temperature under a strain rate of 2.5·10−3 s−1 on of the flat specimens were 6,3 mm in length and 3 mm in diameter and a gauge length of 25 mm. Effect of different grain size on microstructure and strain hardening behavior of high-Mn steel solution heat-treated was analyzed. The strength properties increase considerably with a decrease of grain size from 360 μm to 20 μm, where in the critical grain growth took place between 1000°C and 1100°C. The inverse relationship was confirmed between the grain size and ductility. The uniform elongation was increasing from 35% to 45% along with the increasing of grain size in the temperature range from 900°C to 1100°C and dramatically decreasing at the temperature 1200°C to the 23% by grain size 360 μm. Aluminium has segregated on the austenite grain boundaries in steel was solution heat-treated at 1200 °C and the intermetallic phase of Fe2Al5 type was observed. The morphological examination after stretching was carried out in a light microscope and high-resolution scanning electron microscope and EBSD analysis.

This paper, the scientific basics for the production of ultra-fine grained titanium using the technology of Equal Channel Angular Pressing (ECAP) deformation to manufacture medical implants for their wide use in trauma treatment and dentistry are presented. Special attention is paid to the physics and mechanics of methods of ECAP deformation leading to the formation of ultra-fine grained structures in titanium. The influence of fine grained on the mechanical and biomedical properties of titanium is studied, and the advantages of applying ultra-fine grained titanium for medical implants are considered in detail.

The technology severe plastic deformation was applied on austenitic steel AISI 316. It was verification of severe plastic deformation application possibility on steel AISI 316 importantly for following applying on similar kinds of steel, because SPD technology influence on fatigue properties was confirmed. It can be predicted on the basis of obtained results that, contrary to low-cycle fatigue the ultra-fine grained material will manifest at fatigue load in the mode of constant amplitude of stress higher fatigue characteristics, particularly fatigue limit.

The paper presents laboratory physical modeling of the seamless tubes production, specifically the first step of the Mannesmann production process, the so-called punching. A “Universal rolling mill” at MATERIAL & METALLURGICAL RESEARCH Ltd. was used for experiments. The experimental material was micro-alloyed steel. The tests were carried out at four different heating temperatures and at different rpm speeds of the working rolls. The other settings of the rolling mill remained the same. In terms of the geometrical parameters, the biggest necking of the punched sample (preferably at both ends) was observed with increasing temperature and strain rate. The torque decreased with increasing temperature and with lower roller speeds. The punching time and the total current power consumption decreased with increasing temperature and with a higher deformation rate.

Using the sophisticated MAXStrain II unit, part of the HDS-20 simulator, the effect of intensive cumulative hot deformation on the final structural properties of non-alloyed low carbon steel was investigated. In the case of the MAXStrain II unit, the specimens are deformed by compression in two axes, which allows to achieve large cumulative strains. This fact, together with the possible course of suitable softening processes, represents a potential for research and development of materials with fine-grained structures. The microstructure of all samples of low-carbon alloy steel, deformed at MAXStrain II unit, was composed of a mixture of ferrite and pearlite; in the case of samples after accelerated cooling, hardening components were also detected in the microstructure (share up to 5 %). In all cases, during the MAXStrain II tests, the resulting ferritic grain of the steel under test was refined, with the finest microstructure showing an average ferritic grain size of 6.8 m. The resulting ferritic grain size decreased with decreasing deformation temperature and, in the case of lower overall equivalent strain, also with longer interpass time. However, the chosen cooling rate had a dominant effect on the resulting ferritic grain size.

Typical metal expansion joints (MEJ) are made nowadays by plastic cold working, using roller systems, hydroforming methods, etc. There will be presented a concept to manufacture MEJ with the hybrid mechanically assisted laser forming method (HMALFM). Classical laser forming method uses the phenomenon of distortion in the material as a result of the element's local temperature change. The element is heated by the energy from the laser beam acting on it. The appropriate geometry and trajectory of the laser beam leads to the desired shapes of the element. MEJ with combined bellow-lens shape, are made of a metal tube with an appropriate diameter and wall thickness. The concept assume the use of a CO2 laser to implement such a expansion joints. The laser beam heats selected area of the rotating tube, which is mounted on swivel handle on one side and in the actuator handle with the other end. After reaching the plasticizing temperature, the actuator compresses the element. As a result, a bellow-lens shape like is formed at plasticization area. Initial experimental studies confirmed the validity of the concept. As a final result, bellow-lens metal expansions joint was obtained - DN20 type. ACKNOWLEDGEMENTS: The research reported herein was supported by a grant from the National Centre for Research and Development. Program title: Lider XI, grant title: "Development of new type metal expansion joints and their manufacturing technology", contract number: LIDER/44/0164/L-11/19/NCBR/2020.

Severe hot forming methods are effective in grain refinement and controlled development of microstructure. One of these methods is the cumulative deformation on the MAXStrain simulation module. The current state of the issue is briefly discussed in the literary analysis. In the presented research, the basic parameters of the simulation module MAXStrain II cooperating with the Gleeble 3800 hot deformation simulator as well as a new methodology for calculating the equivalent strain value during the cyclic multi-pass multi-axis deformation are introduced. The procedure for development of a unique computational model is presented in the individual steps.

Artificial neural networks (ANN) embody the wide family of various brain-inspired approaches finding their utilization at the solution of many up-to-date issues, e.g., voice, picture and video processing and recognition or regression analysis. The ANN-based regression analysis is able to provide a functional relationship between the high number of predictors and high number of outcomes. This ANN ability has been in the frame of the submitted research applied to offer an alternative methodism for the forecasting of hot flow curve global maximum coordinates under a wide range of thermomechanical circumstances. The research is aimed to evaluate three types of ANN - a Multi-Layer Perceptron (MLP), Radial Basis Neural Network (RBNN) and Generalized Regression Neural Network (GRNN). The results have showed that considering the description of both peak point coordinates simultaneously, the RBNN two-outputs model offered the best performance from the point of view of achieved accuracy, forecasting ability and even feasible computing time.

Micro-blanking can be an effective method of producing preforms for microforming if proper shape accuracy is ensured, and especially burr is eliminated. A new micro-blanking method meeting these requirements is presented. The process is called Micro-Blanking with Mutual Calibration - MBMC. It involves performing micro-blanking and then pushing the disk back through the resulting hole using a counter-punch. The product shape is corrected and the burr is eliminated. It is possible with proper selection of slack. A method has been proposed to determine the appropriate clearance value based on the results of FEM modeling assessed using the proposed parameters. FEM models are created based on the analysis of the results of only one specially designed MBMC process replacing a number of costly experiments. It is a process in which, with a nominal clearance of 5%, the punch axis is shifted in relation to the matrix axis by about 1/3 of the clearance. This results in a smoothly changing clearance in the range of 1.5 - 8.5%. Modeling parameters are adjusted to the separation surface shapes and burr occurrence obtained for individual clearances. In the analyzed case of the MBMC process concerning a disk punched with a 1 mm diameter and 0.25 mm thick CuZn37 brass in hardened condition. A method of assessing the broadly understood quality of a punched micro-product was proposed, based on the analysis of the geometry of the cross-sectional outline of the punched disc and hole. Using this method, it was shown that the MBMC process increases the quality of the product in relation to the punching alone in the range of 0.7 to 2.2% of clearance

The DRECE method is a very promising method for forming sheet metal sheet using the severe plastic deformations (SPD) principle. The DRECE method is characterized by the continuous extrusion of the sheet metal strip by the forming die, which creates a forming angle of 108 ° in the deformation zone. In the case of materials formed by a given method, there is a substantial increase in the mechanical properties, in particular the yield strength, already after the first pass through the forming device, while maintaining sufficient ductility of the materials. An important technological parameter of the forming equipment is the feed speed of the sheet metal strip. The forming device allows to regulate the feeding speed of the sheet metal strip in the range of 10 - 100 mm/s. The device enables continuous sensing and recording of torque, extrusion force and feeding speed of the sheet metal strip during the forming process. These facts are very important for the subsequent use of the method in industrial practice. In order to study the possibility of applying the DRECE method in industrial practice, this work presents proposals for design solutions for industrial use. The proposed design solution is also supplemented by mathematical simulations of the forming process.

In the last decades, equal channel angular pressing (ECAP) process is used for grain refinement of the metallic materials which leads to improvement of the mechanical and physical properties. Using ECAP method significant strains can be imposed into material. However, for practical use, homogeneous distribution of the strain is very important. Usually, ECAP processing parameters are applied to distribute strain homogeneously inside processing sample. In this study, commercially hot extruded AZ61 magnesium alloy was processed by equal channel angular pressing (ECAP) method. Experiments were conducted to evaluate the microstructural characteristics after individual ECAP passes (up to 4 passes). The results show that by ECAP produces excellent grain refinement with average grain size of bellow 5 μm after processing at 200°C. Grains were formed as a result of dynamic recrystallization originated by fine Mg17Al12 phase particles having 100-200 nm diameter dynamically-precipitated during ECAP processing.

The creation of UFG (ultra-fine grain) materials is a new and promising way to improve metals and alloys for advanced structural and functional application. To date, it is common knowledge that UFG materials can be successfully produced by intense plastic deformation. Severe plastic deformation (SPD) is one of the most effective techniques to improve the physical and mechanical properties of metallic materials through structural refining for UFG and nano-crystalline (NC) states. One of the approaches that has been the subject of basic and applied research for two decades is the preparation of materials with UFG structure with a grain size below 1000 nm. In the case of such materials, especially steels, as well as alloys of non-ferrous metals, the achievement of a substantial mechanical properties of the same materials are reconstructed in a classical way and their application in practice, a great economic effect. Such materials will find use primarily where they use high fortresses, while preserving the required plasticity, it will be due to the reduction of the weight of the structure, which will also contribute to the preservation of its safety (steel using lived in the automotive industry, steel for engineering, alloys of non-ferrous metals in the aerospace industry), or high strength and hardness in combination with biocompatibility ensures greater life of the products (titanium implants, etc.). Some ultra-fine-grained steels are already introduced in mass production, while the expected properties are achieved by methods of plastic deformation. These materials include, for example, DC01 and DC03, which will be analyzed in the following article after several passes through the DRECE method. The DRECE forming process is based on extrusion technology with zero change in cross-section dimensions with the ultimate goal of achieving a high degree of deformation in the formed material. With the help of severe plastic deformation of the material, a substantial refinement of the structure of the material is achieved.