Kearns texture parameters, mechanical properties and damageability of titanium sheet after alternating bending

This work aims to determine the Kearns texture parameters and evaluate on their basis the elastic moduli, mechanical properties (ultimate tensile strength, conditional yield stress), as well as damageability parameters of the sheets commercial titanium (CT-grade 1: 0.04% Fe; 0.015% C; 0.05% N 0.05% c; 0.009% H) as delivered after rolling and annealing at 840°C (original sheet) and further alternating bending (AB) in the amount of 0.5; 1, 3 and 5 cycles. Damageability parameters characterizing damage accumulation were determined from the elastic modulus change after the above-mentioned number of AB cycles relative to the values ​​of the elastic modulus in different directions of the original sheet of the studied titanium. The elastic constants of the single crystal and the Kearns texture parameters were used to estimate the elastic modulus in the rolling direction (RD) and transverse direction (TD) of the original sheet, and sheets after an above number of AB cycles. The deviation of the calculated and experimental values ​​of the elastic modulus did not exceed 5%. The deviation of the calculated and experimental values of the ultimate tensile strength and yield stress in the RD and TD both in the initial state and after the corresponding number cycles of the AB did not exceed 10%.

THE USE OF EXTERNAL PHYSICAL INFLUENCE TO REGULATE THE FORMATION OF THE STRUCTURE OF STEEL INGOTS

В настоящей работе исследовано влияние температурных и силовых параметров внешнего воздействия на кристаллизацию и структурообразование слитков из модельных и реальных сплавов. Показано, что скоростью зарождения и роста кристаллов, а также размерами структурных зон в слитках можно управлять, изменяя температурный градиент, возникающий в жидкой фазе перед границей затвердевания. Управлять градиентом температур по сечению затвердевающего расплава можно, регулируя интенсивность теплоотвода, а также дифференцируя теплоотвод по периметру формирующегося слитка. Установлено, что от соотношения градиента температуры к скорости кристаллизации - G/R зависит формирование той или иной структурной зоны слитков. Наглядно доказана эффективность влияния вибрации на формирование структуры исследуемых слитков. Определен механизм воздействия вибрации на процессы кристаллизации и формирования структур слитков, который заключается в проявлении следующих эффектов: в разрушении и дроблении дендритов, растущих на фронте кристаллизации, под действием знакопеременных изгибающих давлений упругой волны; в зарождении кристаллов в объеме кристаллизующегося расплава вследствие кавитации; в разрушении дендритов в расплаве и на фронте кристаллизации под действием давлений, возникающих в результате схлопывания кавитационных каверн. In this paper, the influence of temperature and force parameters of external influence on the crystallization and structure formation of ingots from model and real alloys is investigated. It is shown that the rate of crystal nucleation and growth, as well as the size of the structural zones in the ingots, can be controlled by changing the temperature gradient that occurs in the liquid phase before the solidification boundary. You can control the temperature gradient along the cross-section of the solidifying melt by adjusting the intensity of the heat sink, as well as differentiating the heat sink along the perimeter of the forming ingot. It is established that the ratio of the temperature gradient to the crystallization rate - G/R depends on the formation of a particular structural zone of ingots. The effectiveness of the influence of vibration on the formation of the structure of the ingots under study is clearly proved. The mechanism of vibration influence on the processes of crystallization and formation of ingot structures is determined, which consists in the manifestation of the following effects: in the destruction and crushing of dendrites growing at the crystallization front under the action of alternating bending pressures of an elastic wave; in the nucleation of crystals in the volume of the crystallizing melt due to cavitation; in the destruction of dendrites in the melt and at the crystallization front under the action of pressures resulting from the collapse of cavitation cavities.

Bending Steel Billet on Presses of Tube Electrical Welding Aggregation

At the production of the steel thick-walled large-diameter pipes according to UOE-technology at the tube electrical welding aggregation 1020 (TEWA 1020), the steel sheet is in series bent on the flanging press, the pre-forming press and the final-forming press. When the steel sheet is deformed on the final-forming press, the excessively curved sections of the sheet are partially unbent in the opposite direction. The calculation of sheet’s curvature at the alternating bending causes the significant difficulties because of Bauschinger’s effect at bending, in which the mechanical characteristics of the steel change significantly. In this paper, the analytical method for calculating the final curvature of steel pipe billet at the alternating bend at UOE-technology is proposed. The results of the paper can be applied in metallurgy.

Investigation of the Influence of Non-Flatness and Runout of Friction Discs on the Service Life of Machine Clutches

In the manufacture of discs, it is important not only to ensure their specified geometric accuracy and correct shape, but to maintain geometric parameters during operation. The method of testing disks on the IKS-T inertial test bench is described. The main units of the test bench and the loading parameters of the disks are indicated. Research has been carried out on the influence of the runout and non-flatness of friction discs on the service life of the clutches. Bench tests made it possible to determine the optimal runout range of discs up to 0.8 mm, which ensures an increase in the reliability of the clutches by 30 % due to a decrease in the wear of the friction discs. In addition, the test results show that with a decrease in non-flatness from 1.2 mm to 0.3 mm, the service life of the friction discs increases by 16 %, i.e. wear of discs in the running-in mode with distortions in geometry occurs more intensively than for discs with a flat surface. With an out-of-flatness value of 0.3 mm, the discs acquire improved elastic characteristics. It was possible to determine that increased values of disc wear are observed mainly along the outer diameter, due to the runout and higher sliding speed compared to the sliding speed on the inner diameter. Calculated dependences of the limiting number of loading cycles on the beating and non-flatness of discs are presented. It was found that when testing discs with the non-flatness less than 0.3 mm, disc wear appears with the formation of “poppet” disc shape. For the purpose of imparting the correct shape to the products with the exclusion of “poppet” discs, a dynamic straightening with combined loading is proposed. The resulting calculated dependencies will be used in the design of industrial universal installations for cyclic alternating bending of friction discs.

Development of a method and equipment for testing materials for alternating bending during piercing in screw rolling mills

Hot-rolled pipe production is complicated process of metal treatment by pressure and as a rule it has three operations of form charging: piercing, plugging, calibration or reduction. Each of them is characterized by complex schemes of stress-deformed state which promotes either formation or detection of various defects. Hot billet piercing at screw piercing rolling mill is widely used for pipe production for its high output and getting the shells of long length. But this operation of form charging of the metal is realized under the conditions of complicated stress-deformed state with cyclic alternating bending of all metal layers. Defects appearing on the outside surface of the shell such as captures and cracks is caused by plastic bending of shell wall, which is followed by alternating stress and deformation at the inlet and outlet cone of deformation zone in consequence of four times plastic bending of the wall. Shell wall is influenced by compression stress of the working rolls and guides. The less favorable scheme of stress state with tensile stress arises on the shell surface between the rolls and the guide. And as a results it generates and increases the defects on the outside surface. Theoretical and experimental research of deformation and speed conditions of billet piercing process for screw piercing rolling mill is presented in the work. Statistic data of production mills which operate in TRA 50-200 and TRA 159-426 lines were used for the research. All the calculations were done with use of applied software and test machine of original design with crank and connecting rod mechanism was constructed. The machine carries out the process of alternating plastic bending which is in maximum close to the conditions taking place in deformation zone of screw piercing rolling mill. Definition of rational configuration of sample shape was determined. Process plasticity of the metal of hot samples was analyzed as well. The samples were made from hot-rolled bars of different steel grades.

Improvement of rubber recipe for massive tires by addition of non-traditional fillers

We investigated the effect of new fillers on the properties of rubbers for solid tires. Modified by fullerenes and unmodified iron oxide fillers were used as new fillers. Fatigue characteristics were determined by two methods: multiple tension on the UR-500 device in accordance with GOST 261-79; alternating bending with rotation on the device SZPI in accordance with GOST 10952-75. The main tasks of constructing fatigue curves were to assess the compliance of the results of strength tests (tension at a constant speed to break) with fatigue in terms of fatigue life, fatigue strength, and fatigue energy density of fracture. In addition, the task was to verify the possibility of plotting on one Weller curve points obtained on different devices - UR 500 and ZPI. The ranking of rubbers in static does not coincide with each other. Since the fatigue loading conditions are closer to the actual operating conditions than the static ones, in order to predict the behavior of rubber goods in operation, one should focus on the results of fatigue tests. Combining the results of fatigue tests with repeated tension and with alternating bending with rotation showed that this procedure is valid, but only in cases where the temperature of self-heating on the ZPI device does not exceed a certain critical value when thermal decomposition begins. The results of fatigue tests showed that the use of the studied fillers with small degrees of filling (up to 30 mass parts) can be justified. An example is Ferrocolor fraction 0–20 ?m with a mass fraction of 5 m.h. In this case, the fatigue properties practically do not deteriorate in comparison with industrial rubber for solid tires, in which new fillers are not added.

Effect of Kind of Deformation on Young's Modulus, Damage Parameter, Texture and Structure of Alloy Mg – 5% Li (wt)

Effect of deformation by extrusion, rolling after extrusion (in combination with annealing and changing the rolling direction), and subsequent alternating bending (AB) with the number of cycles 0.5, 1, 3, and 5 on the elastic modulus (E), damage accumulation parameter (damage parameter ω), crystallographic texture, and substructure parameters of the binary Mg-5%Li alloy have been studied. The damage parameter (0 ≤ ω ≤ 1), which is interpreted as the relative reduction in the effective load-bearing cross-sectional area due to damage accumulation, was found by the change in the elastic modulus after various above types of deformation. At this, we used to compare equivalent deformation and equivalent elastic energy models. The substructure parameters (crystalline domains sizes D, lattice distortion ε, dislocation density ρ) were estimated by analyzing the physical broadening of the lines diffraction on the crystal lattice of studied alloy of the penetrating hard X-ray synchrotron radiation. It was found that in the studied alloy, sheet forms a texture, at which the hexagonal prism axis is 90° deviated from the normal direction (ND) to the sheet up to transverse direction (TD) after extrusion of the ingot at 350°C in combination with its further rolling in the direction of extrusion axis (rolling direction RD) to a thickness of 4.5 mm and annealing at 350°C after each pass. At this the crystallographic directions and coincide with RD. The texture, at which the hexagonal prism axis is deviated from ND to TD by angles ranging from 15 to 70° (unlike from texture of basal type of the pure magnesium) is formed after further rolling of studied alloy to a thickness of 1 mm with the changing of the RD on 90° in combination with annealing at 350°C after each pass. The crystallographic direction coincides with RD. The anisotropy of above mentioned characteristics was found. Correlation and regression analysis showed that the anisotropy and the values of E, D, ε, and ρ, are decreased, and the values of ω are increased with an increase of alternating bend cycles’ number. It is shown that changes in the above characteristics are mainly due to the crystallographic texture formed during thermomechanical processing and subsequent alternating bending of Mg-5%Li alloy sheets, which is confirmed by data of correlation and regression analysis.