Zhanara Mussina

This study investigates a method for the rotational turning of external cylindrical surfaces with a particular focus on evaluating the quality of the machined surface and its stress state during the turning of 45 steel, using experimental methods and the Finite Element Method (FEM). The influence of the cutting modes on the quality indicators during rotary turning was analyzed, and their optimal values for the processing of steel 45 were determined. The results indicate that an increase in the spindle speed has a positive impact on the roughness of the machined surface, but a negative effect on hardness. Increasing the feed rate has an ambiguous impact on the quality indicators of the machined surface: it improves the roughness but reduces the hardness. With an increase in the cutting depth, both quality indicators deteriorate. In addition, using the ANSYS/LS-DYNA (Ls Pre-Post) software package, the stress-strain state of the steel 45 workpiece was calculated, and the temperature change in the cutting zone, in the chips, and on the machined surface during rotational turning was determined. This revealed that the maximum equivalent Mises stress is 1.1 MPa and the maximum temperature in the cutting zone is 287 °C. It was observed that when the cutting force fluctuates within the range of 4.8 kN-5.1 kN, the vibration occurring in the cutting zone is reduced. The results of this study indicated that rotary machining allows for increased feed, depth, and cutting speed without critical tool wear, which directly increases the productivity. It also reduces the tooling, energy, machining time, and rework costs, resulting in significant economic benefits.

This study investigates the effect of surfacing with Sv-10Х17Т welding wire on the tribological properties of steel samples. The research is motivated by the need to extend the service life of components operating under frictional loads while reducing the maintenance and repair costs. The focus is on a key element of the pipeline shut-off valves, the wedge of a wedge gate valve, which experiences high contact stresses and severe wear during operation. Laboratory tests were conducted under various friction conditions, involving dry friction, water-based media, and oil-based media. Parameters, such as the coefficient and moment of friction, contact temperature, mass loss, wear depth, surface microhardness (both before and after testing), and surface roughness (Ra), were systematically measured. Experiments with steel samples surfaced using Sv-10Х17Т welding wire were designed to replicate actual valve working conditions. The results showed that Sv-10Х17Т surfacing significantly increased wear resistance, reduced friction, and enhanced surface microhardness, particularly under prolonged dry friction. The microstructural analysis confirmed the formation of a hardened riveted surface layer with deformation strengthening and partial thermal treatment. These findings indicate that Sv-10Х17Т surfacing not only restores, but also improves the performance of the steel components, offering an effective method to extend the operational life. The outcomes of this research have practical value for mechanical engineering, as well as the repair and maintenance of pipeline equipment, turbines, gearboxes, bearings, valves, and other critical components.

This article focused on improving the quality of hole machining using a new design of a metal-cutting tool, referred as reamer-broach. Before conducting experimental studies, fixtures were designed, a turning and screw-cutting machine was tested for geometric accuracy, and methods for evaluating the quality of the processed surface were developed. A full-factorial experiment of the 22 type was conducted to determine the influence of technological factors (rotation speed, supply) on hole accuracy, roughness, and shape deviations when machining with both a machine reamer and a reamer-broach. Additionally, an analysis of the microstructure of hole surface was performed, to prove the machinability of the material. The results indicated that an increase in feed led to an increase in the radial forces, a stabilized tool position, and a decrease in hole breakdown. An increase in rotation frequency resulted in the rise of hole breakdown as well as in an increase in surface roughness. These findings demonstrated an increase in accuracy by 1-2 quality grades compared to machine reamer and a decrease in surface roughness by 1-2 grades when processing holes using a reamer-broach.

Instrumental production is a crucial component of industrial and innovative development in the metalworking industry, where the drilling process plays a key role. Traditional twist drills with conventional cutting-edge designs, including a transverse edge, face several issues during drilling, such as difficult chip evacuation and high friction between the tool and the workpiece. These phenomena, in turn, lead to a deterioration in the quality of machined holes and a reduction in tool life. Existing methods of drill geometry modification only partially address these problems by reducing axial forces and increasing tool durability, but they do not provide a comprehensive improvement of the drilling process overall. The aim of this study is to develop and examine a new drill design—a double-point twist drill without a transverse edge, which ensures favorable cutting conditions, reduces tool wear, and increases tool durability during the drilling process. In the course of the study, experimental samples of the double-point drill were manufactured at the machine-building company LLP «Format Mach Company» (Pavlodar). For the experimental tests, a setup was developed that included the ZET 058 strain gauge system and Kistler piezoelectric force sensors. This combination allowed for a detailed investigation of cutting forces in a dynamic mode and recorded the loads acting on the tool in various directions, contributing to an objective evaluation of its performance. The experimental results showed that the double-point drill without a transverse edge significantly improves the drilling process by reducing axial and radial cutting forces, which helps to reduce tool wear and increase drill durability. This confirms the feasibility of applying this drill design to enhance the quality of hole machining and the efficiency of production processes in the metalworking industry. An increase in the durability of the new tool - a double-point twist drill without a transverse edge - was established at 2.2 times.