A.V. Mitrofanov

Bio: A.V. Mitrofanov is an academic researcher from Loughborough University. The author has contributed to research in topics: Cutting tool & Machining. The author has an hindex of 13, co-authored 19 publications receiving 1129 citations. Previous affiliations of A.V. Mitrofanov include University of the Sciences.

Analysis of material response to ultrasonic vibration loading in turning Inconel 718

Abstract: The paper is focused on the analysis of the surface layer formed on a workpiece treated with ultrasonically assisted turning (UAT) in comparison to conventional turning (CT). Various experimental methods are used to study the difference between the two machining techniques: nanoindentation, light microscopy and scanning electron microscopy (SEM). The experimental part of the paper studies the material response to CT and UAT in terms of material's hardness, residual stresses, and changes in the microstructure. The difference in the distribution of residual stresses in the machined surface layer is further studied by means of numerical (finite element) simulations. A three-dimensional thermomechanically coupled finite element (FE) model of both UAT and CT is used to study temperature distributions in the process zone and thermally induced stresses. Numerical results are compared with the obtained experimental data.

Machining induced surface integrity in titanium and nickel alloys: A review

Abstract: Titanium and nickel alloys represent a significant metal portion of the aircraft structural and engine components. When these critical structural components in aerospace industry are manufactured with the objective to reach high reliability levels, surface integrity is one of the most relevant parameters used for evaluating the quality of finish machined surfaces. The residual stresses and surface alteration (white etch layer and depth of work hardening) induced by machining of titanium alloys and nickel-based alloys are very critical due to safety and sustainability concerns. This review paper provides an overview of machining induced surface integrity in titanium and nickel alloys. There are many different types of surface integrity problems reported in literature, and among these, residual stresses, white layer and work hardening layers, as well as microstructural alterations can be studied in order to improve surface qualities of end products. Many parameters affect the surface quality of workpieces, and cutting speed, feed rate, depth of cut, tool geometry and preparation, tool wear, and workpiece properties are among the most important ones worth to investigate. Experimental and empirical studies as well as analytical and Finite Element modeling based approaches are offered in order to better understand machining induced surface integrity. In the current state-of-the-art however, a comprehensive and systematic modeling approach based on the process physics and applicable to the industrial processes is still missing. It is concluded that further modeling studies are needed to create predictive physics-based models that is in good agreement with reliable experiments, while explaining the effects of many parameters, for machining of titanium alloys and nickel-based alloys.

Review of vibration-assisted machining

Abstract: Vibration-assisted machining (VAM) combines precision machining with small-amplitude tool vibration to improve the fabrication process. It has been applied to a number of processes from turning to drilling to grinding [9] , [36] . The emphasis on this literature review is the turning process where VAM has been applied to difficult applications such as diamond turning of ferrous and brittle materials, creating microstructures with complex geometries for products like molds and optical elements, or economically producing precision macro-scale components in hard alloys such as Inconel or titanium. This review paper presents the basic kinematic relationships for 1D (linear vibratory tool path) and 2D VAM (circular/elliptical tool path). Typical hardware systems used to achieve these vibratory motions are described. The periodic separation between the tool rake face and uncut material, characteristic of VAM, is related to observed reductions in machining forces and chip thickness, with distinct explanations offered for 1D and 2D modes. The reduced tool forces in turn are related to improvements in surface finish and extended tool life. Additional consideration is given to the intermittent cutting mechanism and how it reduces the effect of thermo-chemical mechanisms believed responsible for rapid wear of diamond tools when machining ferrous materials. The ability of VAM to machine brittle materials in the ductile regime at increased depth of cut is also described.

State-of-the-art in surface integrity in machining of nickel-based super alloys

Abstract: Nickel-based super alloys are gaining more significance, now-a-days, with extensive applications in aerospace, marine, nuclear reactor and chemical industries. Several characteristics including superior mechanical and chemical properties at elevated temperature, high toughness and ductility, high melting point, excellent resistance to corrosion, thermal shocks, thermal fatigue and erosion are primarily responsible for wide domain of application. Nevertheless, machined surface integrity of nickel-based super alloys is a critical aspect which influences functional performance including fatigue life of the component. This review paper presents state-of-the-art on various surface integrity characteristics during machining of nickel-based super alloys. Influence of various cutting parameters, cutting environment, coating, wear and edge geometry of cutting tools on different features of surface integrity has been critically explained. These characteristics encompass surface roughness, defects (surface cavities, metal debris, plucking, smeared material, redeposited material, cracked carbide particles, feed marks, grooves and laps), metallurgical aspects in the form of surface and sub-surface microstructure phase transformation, dynamic recrystallisation and grain refinement and mechanical characteristics such as work hardening and residual stress. Microstructural modification of deformed layer, profile of residual stresses and their influence on fatigue durability have been given significant emphasis. Future research endeavour might focus on development of new grades, advanced processing techniques of the same to ensure their superior stability of microstructure and thermo-mechanical properties along with advanced manufacturing processes like additive manufacturing to achieve highest level of fatigue durability of safety critical components while maintaining acceptable surface integrity and productivity.

Effect of machining parameters and cutting edge geometry on surface integrity of high-speed turned Inconel 718

Abstract: Stringent control on the quality of machined surface and sub-surface during high-speed machining of Inconel 718 is necessary so as to achieve components with greater reliability and longevity. This paper extends the present trend prevailing in the literature on surface integrity analysis of superalloys by performing a comprehensive investigation to analyze the nature of deformation beneath the machined surface and arrive at the thickness of machining affected zone (MAZ). The residual stress analysis, microhardness measurements and degree of work hardening in the machined sub-surfaces were used as criteria to obtain the optimum machining conditions that give machined surfaces with high integrity. It is observed that the highest cutting speed, the lowest feedrate, and the moderate depth of cut coupled with the use of honed cutting edge can ensure induction of compressive residual stresses in the machined surfaces, which in turn were found to be free of smeared areas and adhered chip particles.