Materials Science Forum Vol. 952

Abstract: Stress concentration in thread roots and nonuniform load distribution along thread turn are the major disadvantages of bolted joints. Under changing cyclic loads on areas of high stress concentration crack formation and destruction of parts occur. In addition, the fretting corrosion processes activate in the areas of contact between thread turns. The purpose of the work is to increase rupture strength of bolted joints under the action of cyclic forces by decreasing stress concentration and reducing movements in contact zone of mating parts in case of assembly with implementation of anaerobic materials. Modelling of bearing strength of bolted joints is conducted according to finite element method, with theory of contact interaction between mating surfaces being used. The results of experimental research are given. Anaerobic materials which polymerize in area of thread contact of parts are used. It was established that assembly with implementation of anaerobic material allows unloading of thread turns because the part of external load is received by elastic layers of the polymerized anaerobic material. In this case the level and the concentration of stress in thread roots reduce, relative movements are decreased, the joint becomes more rigid and its cyclic robustness grows.

Abstract: Technological processes have a significant influence on the properties of the metallic formed pieces during production. Due to the plastic deformation, the shape of the component is changed and the degree of the structural anisotropy is increased - the orientation of the grain boundaries in the different parts of the component. It is important to identify these changes, to analyse them and optimize the technological processes. We get an important knowledge of relationship “technological parameters – microstructure – properties”. The article presents the results of the solution of a partial task from this area. It deals with changing of the geometric shape of the component when it is deformed. Specifically, the tubes (material EN SPT 360, STN 411 353) were drawn through the dies with different reduction angles. The dimensions (length and angle), roundness, cylindricity, coaxiality and surface roughness were evaluated.

Abstract: The final machining and component forming operations have a considerable impact on final state of the surface layers in the machining process. These also include the technological operation of ultrasonic dynamic strengthening of the component surface layers. It is a specific surface-forming technology due to which the component properties can be effectively influenced, especially in their surface layers. Correct implementation of this technology can improve efficiency and extend the life span of both the produced components and the technical equipment. The article deals with the methods of special simulation of ultrasonic dynamic strengthening of metallic materials. Based on the results of the simulation, the technological parameters of the process of metallic material strengthening and ultrasonic concentrator design can be determined.

Abstract: The paper deals with the problems of austenitic chrome-nickel steels and their behavior in plastic deformation processes. These steels cannot be hardened by thermal processes due to a stable austenitic structure, therefore the increase of strength is achieved only by cold forming. The deformation mechanisms of the slip or twinning are activated by the effect of the forming force in the steel. Mainly, there is formed deformation-induced martensite whose structure is different from the martensite created by the heat treatment. As the intensive hardening of austenitic chrome-nickel steels under the effect of plastic deformation is beneficial, it adversely affects the machining of these materials.

Abstract: This paper is a study of rheological analysis of magnesium alloys of groups Mg-Zn-Al and Mg-Zn-RE. It presents the results of high-temperature measurements of magnesium alloys, along with rheological analysis of their behaviour. Magnesium alloys are a very attractive material, due to their light weight and good plastic properties; on the other hand this material is very reactive in a liquid (semi-solid) state, which is challenging from a testing and forming perspective. The findings obtained were compared with five types of rheological models describing rheological characteristics of viscous systems. The analysis was carried out using Rheoplus software. As a result of the conducted work, the mathematical descriptions which are best for characterising rheological behaviour of semi-solid magnesium alloys containing 20% of the solid phase have been proposed.

Abstract: The engineering production is currently characterized by frequent changes. These changes are caused because the life cycle of products is shortened. Producers must introduced the upgraded products in a shorter interval. In this article we will focus on identifying the possibilities of production innovation in the flexible manufacturing system. An analysis of the production possibilities of one of the production machines in the flexible production system will be carried out. This production machine is a lathe that produces one basic part of the finished product. We will determine what variants of this component can be manufactured without changing the physical configuration of the machine.

Abstract: This research paper deals with the influence analysis of the conventional metal spinning parameters (tool path profile tpp, tool feed f and mandrel rotational speed n) on the wall heights and the surface roughness Ra of the cylindrical-shaped spun parts measured in various directions with respect to the material rolling direction. Experimental research was carried out according to the 3-level full factorial design of experiment (DoE). Experimental study was also statistically analyzed by the ANOVA method. It was observed that tool path profile is a process parameter which has the most significant impact on the spun cup height and the surface finish, as well.

Abstract: The kinematic versions and applied tools of milling allow for the machining of several surfaces and surface combinations, making it a versatile and widely applied procedure. Face milling for cutting is used for the high productivity manufacturing of prismatic components. Naturally, the enhancement of productivity is a primary goal for manufacturing companies; this study analyzes the efficiency of material removal, which directly influences the time parameters characterizing production performed by face milling. The focus of the paper is to identify the selection of technological data (feed, feed rate, cutting speed, diameter of milling head) that can reduce the machining time or increase the values of material removal rate. Cutting experiments were carried out for machining prismatic components from AlSi9Cu3(Fe) aluminum alloy by diamond tools. It was found that within the performance limits of the manufacturing system it is possible to save a significant amount of manufacturing time while retaining the specified geometric accuracy and surface quality of the component.

Abstract: The effect of natural pre-aging time (from 0.1 to 10000 h) on mechanical response during subsequent artificial aging of EN AW 6063 aluminium alloy at 170°C was investigated using Vickers microhardness measurements, tensile test analysis and transmission electron microscopy characterization. The microhardness and tensile strength of EN AW 6063 alloy increased slightly with natural aging time. Afterward, the artificial ageing from 18 to 20 hours induced the maximum increasing of hardness and strength for variously naturally pre-aged states of alloy. But, it was found that when pre-aging time was prolonged from 0.1 h to 10000 h, the mechanical response of artificial aging applied for the pre-aged alloy states was slightly improved. It was suggested, that as pre-aging time was increased, the size of β'-phase particles formed in solid solution of pre-aged alloy state during artificial aging was decreased and their amount was increased.