Rotary Cutting with Ultrasonic Vibration of Hardened Steel

We propose ultrasonic rotary cutting, in which ultrasonic vibrations are imparted to a rotating cemented carbide cylindrical tool to cut hardened steel to reduce the cutting resistance and improve the properties of the machined surface, and investigate the machining characteristics. Machining experiments were conducted under dry and wet conditions to verify the effects of the ultrasonic vibrations. The surface produced via ultrasonic rotary cutting was intermittently machined, which is characteristic of ultrasonic cutting. In dry machining, the cutting resistance was reduced by approximately 20%, and the surface roughness of the machined surface was reduced by approximately 30% when the cutting speed was below the critical speed. We also demonstrated that the surface roughness was improved by ultrasonic vibrations when the cutting speed was equal to or above the critical speed. A similar tendency was observed in wet machining with longer cutting lengths. We then applied ultrasonic rotary cutting to machine a straight R groove in hardened steel and showed that the cutting resistance was reduced, and the tool engagement was improved.

Special Issue on High Performance Abrasive Technologies

Demand for the high-precision and high-efficiency machining of hard ceramics, such as silicon carbide for semiconductors and hardened steel for molding dies, has significantly increased for optical and medical devices as well as for powered devices in automobiles. Certain types of hard metals can be machined by deterministic precision-cutting processes. However, hard and brittle ceramics, hardened steel for molds, and semiconductor materials have to be machined using precision abrasive technologies, such as grinding, polishing, and ultrasonic vibration technologies that use diamond super abrasives. The machining of high-precision components and their molds/dies using abrasive processes is very difficult due to their complex and nondeterministic natures as well as their complex textured surfaces. Furthermore, the development of new cutting-edge tools or machining methods and the active use of physicochemical phenomena are key to the development of high-precision and high-efficiency machining. This special issue features 11 research papers on the most recent advances in precision abrasive technologies. These papers cover the following topics: - Characteristics of abrasive grains in creep-feed grinding - Quantitative evaluation of the surface profiles of grinding wheels - ELID grinding using elastic wheels - Nano-topographies of ground surfaces - Novel grinding wheels - Grinding characteristics of turbine blade materials - Polishing mechanisms - Polishing technologies using magnetic fluid slurries - Application of ultrasonic vibration machining - Turning and rotary cutting technologies This issue is expected to help its readers to understand recent developments in abrasive technologies and to lead to further research. We deeply appreciate the careful work of all the authors, and we thank the reviewers for their incisive efforts.

Effect of sphere configurated particle damper on tribological properties during boring of hardened steel

Tool vibration is the most unfavourable element in the boring operation, as it contributes to poor surface finish, excessive tool wear, and progressive cutting force. Tool vibration mainly occurs due to the overhanging length of the boring tool and to overcome this factor an appropriate mechanism has to be established which helps to increase the production and quality of the product in manufacturing sector. An impact particle damper with variable material spheres, sphere diameter, and sphere location in a boring tool is fabricated in this work. A 27 run experiments were conducted to find the effect of impact particle damping on tribological properties during boring process. The results shows that impact particle damper increases the rigidity of the tool holder which enhances the tribological properties. The sphere in the boring tool will collide with one another thereby suppressing the tool vibration efficiently.

Study on Performance of PVD AlTiN Coatings and AlTiN-Based Composite Coatings in Dry End Milling of Hardened Steel SKD11

Dry milling of hardened steel is an economical and environmentally friendly machining process for manufacturing a mold and die. Advances in coating technology makes the dry milling a feasible approach instead of a traditional grinding process. However, the cutting condition is particularly severe in a dry machining process. High-performance coating is desired to meet the requirement of green and highly efficient manufacturing. This study concerned the performance of AlTiN-based coatings. The effect of Al content, and the AlTiN composite coating on the cutting performance of tools are investigated in terms of friction force at the tool–chip interface, specific cutting energy, cutting temperature on the machined surface, tool wear pattern and mechanism, and surface integrity. The results show that advanced AlTiN-based coatings reduce the force and cutting energy and protect the cutters from the high cutting temperature effectively. The main wear mechanisms of the coated tools are adhesive wear, chipping induced by fatigue fracture and abrasive wear. In general, the dry milling of hardened steel with AlTiN-based coatings gains a quite satisfactory surface quality. Furthermore, AlTiN-WC/C hard-soft multilayer coating performs well in reducing cutting force, preventing adhesion wear and isolating the cutting heat, being suitable for dry milling of hardened SKD11.

Селективный магнитный контроль толщины и степени упрочнения поверхностных слоев на стальных объектах

The dependences of measured locally magnetic characteristics of surface-hardened steel objects on the thickness and physical properties of their surface layers are studied. It is shown theoretically and experimentally that a change in the thickness of the hardened layer on the surface of steel objects affects on the magnitude of the tangential field component on the surface of the object in the interpolar space significantly , as well as the change in the strength properties of the layer affects the magnitude of the magnetic flux in the "transducer-object" circuit. It is proposed to use this difference in magnetic parameters for selective testing of the surface hardening quality. It is shown that the coercive force measured locally by the internal field and the maximum value of the magnetic flux, which can be measured using a single transducer in single measuring cycle, can be used as diagnostic parameters.