Investigation of the stress-strain state of balls under deformation in a closed die

The paper presents the results of the study of the production process of balls in a special closed die, which performs a full compression due to the alternate insertion of rams. The possibility of implementing the proposed method is proved experimentally, and the presence of high compressive stresses in the deformation center is shown using the method of sliding lines and mathematical computer modeling. Due to the alternate insertion of rams, the process of plastic deformation is intensified, which makes it possible to obtain high-quality balls. The maximum average stress in the deformation center obtained by the theoretical calculation method of sliding lines is – 436,94 MPa, and the values obtained by mathematical computer modeling is – 500 MPa. Metallographic analysis showed that the grain diameter of the obtained ball samples in the central part, compared to the initial samples, was crushed 3 times (up to 5 μm)

Recycling of stainless steel bar scrap by radial-shear rolling to obtain a gradient ultrafine-grained structure

The paper presents the results of the conducted experiments confirmed not only the possibility of processing bar scrap from stainless metals to produce a marketable product, but also confirmed the possibility of obtaining highquality bars with a gradient fine-grained structure and an increased level of mechanical properties. In the course of the research conducted on deformed bar scrap in the form of pins from 12X18N9T austenitic stainless steel at the radial-shear rolling mill the microstructure of two different types was obtained: on the periphery - equiaxed ultrafine- grained structure with a grain size of 0,4 – 0,6 μm; in the axial zone - oriented striped texture. This discrepancy in the structure of the peripheral and axial zones, together with the results of microhardness measuring across the cross section of samples with a total degree of deformation of 44,4 %, indicates the gradient nature of the formed microstructure

Strain state and microstructure evolution of AISI-316 austenitic stainless steel during high-pressure torsion (HPT) process in the new stamp design

The investigation of strain state and microstructure evolution of AISI-316 austenitic stainless steel during highpressure torsion process in the new stamp design was performed. The study using Deform-3D program was conducted. The deformation was carried out at ambient temperature. The results of strain state study showed that after 4 passes the processed workpiece is obtained the level of equivalent strain more than 5. But the distribution of strain has a gradient view in the cross section. The simulation results of the microstructure evolution showed that after 4 passes of deformation the initial grain size of 12 μm can be reduced up to 0,8 μm. But the distribution of grain size in the cross section also has a non - uniform gradient view

Investigation of the effect of combined thermomechanical processing on the brass microstructure evolution and the microhardness change

The article investigates the effect of combined thermomechanical processing, including pre-heat treatment and radial-shear rolling on the brass microstructure evolution and the microhardness change. The microstructure analysis of heat-treated samples according to various modes showed that the most optimal heat treatment before radialshear rolling for L63 brass is annealing at a temperature of 500 °C. As a result of combined thermomechanical processing, a gradient structure was obtained, so in the resulting rods with a diameter of 16 mm in the surface layer, a structure with an average grain size of 9 μm was obtained. In rods with a diameter of 12 mm, a fine–grained, equalgrained structure of 3 μm was obtained in the surface layer

Bone remodeling markers after experimental augmentation of trabecular bone defects with resorbable and non-resorbable osteoplastic materials in rabbits

To study the effect of bone defect augmentation on the dynamics of bone remodeling markers. Material and methods The effect of resorbable xenoplastic material (RXM), synthetic beta-tricalcium phosphate (b-TCP), porous titanium implant (PTI) and nanostructured carbon implant (NCI) on the markers of bone remodeling (osteocalcin, OC; bone alkaline phosphatase, BALP; C-terminal telopeptide of type I collagen, CTX-1) and inflammation marker (C-reactive protein, CRP) was investigated using bone defect model in rabbits. 24 animals were divided into 4 groups (n = 6 in each group) according to the type of osteoplastic material. Control group (n = 6) was without augmentation. An impression fracture of the proximal tibia was modeled. Blood samples were taken on days 1, 3, 7, 14, 45, 90, 180 after surgery. Results CTX-1was not detected in the control, b-TCP, PTI, and RXM groups after 90 days, but in the NCI group CTX-1 remained elevated until the end of the study. OC in the control, b-TCP, PTI groups reached a maximum at 14-45 days. No significant increase in OC was found in the NCI group. The BALP in the control group peaked at 90 days. In the b-TCP and PTI groups the concentration of BALP increased more rapidly. The dynamics of CRP in the RXM, b-TCP and PTI groups was similar to the dynamics in the control group, in the NCI group an increased level of CRP remained until the end of the study. Conclusion When a bone defect was augmented with both resorbable b-TCP and nonresorbable PTI, high osteogenesis activity and low osteoresorption activity were detected. The use of xenoplastic material did not reveal any advantages in comparison with surgery performed without augmentation. An increase in osteoresorption and a low level of osteogenesis were found by using NCI. © Yildiz K., Yildiz V., 2020

Analysis of the Influence of New Combined Process "Equal Channel Angular Pressing-drawing" on the Microstructure and Properties of Deformed Wire

This article is devoted to analysis of the influence of new combined process "Equal channel angular pressing-drawing" on the microstructure and properties of deformed wire. From the result of investigation, figures of microstructure of deformed wire after third cycle of deformation and graphs of mechanical properties were obtained. It is shown that proposed combined method of deformation of “pressing-drawing” has a significant advantage compared with the existing technology of wire production