A review of the mechanics of metal spinning

Compared to conventional machining (CM), ultrasonic vibration-assisted machining (UVAM) with high-frequency and small-amplitude has exhibited good cutting performances for advanced materials. In recent years, advances in ultrasonic generator, ultrasonic transducer, and horn structures have led to the rapid progress in the development of UVAM. Following this trend, numerous new design requirements and theoretical concepts have been proposed and studied successively, however, very few studies have been conducted from a comprehensive perspective. To address this gap in the literature and understanding the development trend of UVAM, a critical overview of UVAM is presented in this study, covering different vibration-assisted machining styles, device architectures, and theoretical analysis. This overview covers the evolution of typical hardware systems used to achieve vibratory motions from the one-dimensional UVAM to three-dimensional UVAM, the discussion of cutting characteristics with periodic separation between the tools and workpiece and the analysis of processing properties. Challenges for UVAM include ultrasonic vibration systems with high power, large amplitude, and high efficiency, as well as theoretical research on the dynamics and cutting characteristics of UVAM. Consequently, based on the current limitations and challenges, device improvement and theoretical breakthrough play a significant role in future research on UVAM.

Review of ultrasonic vibration-assisted machining in advanced materials

The demand for increasing productivity when machining heat resistant super alloys has resulted in the use of advanced cutting tools such as ceramics and cubic boron nitride (CBN). However, the effects of these tools on the surface integrity, especially the residual stresses created, in the high speed facing operation of Inconel 718 has not been dealt with. In this paper, the residual stresses and the surface roughness when facing age hardened Inconel 718 using CBN and mixed ceramic cutting tools at their respective optimum performance based on productivity has been investigated. The residual stress and surface finish generated during facing with CBN cutting tools have been investigated as a function of speed, depth of cut, coolant, tool geometry and nature of the tool coating. In addition, mixed ceramic cutting tools have been investigated for comparison. The results show that mixed ceramic cutting tools induce tensile residual stresses with a much higher magnitude than CBN cutting tools. The residual stresses and the surface roughness generated by CBN cutting tools are more sensitive to cutting speeds than depth of cut. The use of coolant results in either compressive residual stresses or lowers the magnitude of the tensile residual stresses, whereas dry cutting always resulted in tensile residual stresses. From this investigation, it is suggested that round CBN cutting tools should be used at slow cutting speeds (150 m/min) and small depths of cut (0.05 mm) and with the use of coolant to achieve compressive or minimal tensile residual stresses and good surface finish.

Residual stress and surface roughness when facing age hardened Inconel 718 with CBN and ceramic cutting tools

Considerable attention has been given to the use of ceramic cutting tools for improving productivity in the machining of heat resistant super alloys (HRSA). However, because of their negative influence on the surface integrity, ceramic tools are generally avoided particularly for finishing applications. As a result the main high end manufacturers are more or less dependent on carbide cutting tools for finishing operations. Still the improper use of carbide cutting tools can also result in poor surface integrity. The objective of this investigation is to develop a set of guidelines, which will assist the selection of the appropriate cutting tools and conditions for generating favorable compressive residual stresses. This paper specifically deals with residual stresses and surface finish components of surface integrity when machining (facing) age hardened Inconel 718 using two grades of coated carbide cutting tools specifically developed for machining HRSAs. The cutting conditions were obtained from investigations based on optimum tool performance. The effect of insert shape, cutting edge preparation, type and nose radius on both residual stresses and surface finish was studied at this optimum cutting condition. This investigation, suggested that coated carbide cutting tool inserts of round shape, chamfered cutting edge preparation, negative type and small nose radius (0.8 mm) and coolant will generate primarily compressive residual stresses.

Surface integrity when machining age hardened Inconel 718 with coated carbide cutting tools

Finite element analysis of the effect of sequential cuts and tool-chip friction on residual stresses in a machined layer

Roller-burnishing is used in place of other traditional methods to finish 6061-T6 aluminum alloy. How to select the burnishing parameters to improve surface integrity (reduce surface roughness, increase surface microhardness and produce compressive residual stress) is especially crucial. This paper presents an investigation of the effect of roller-burnishing upon surface roughness, surface microhardness and residual stress of 6061-T6 aluminum alloy. The residual stress distribution in the surface region that was burnished is determined using a deflection-etching technique. Mathematical models correlating three process parameters: burnishing speed, burnishing depth of penetration and number of passes, are established. A Group Method of Data Handling Technique, GMDH, is used. It is shown that low burnishing speeds and high depths of penetration produce much smoother surfaces, whereas a combination of high speed with high depth leads to rougher surfaces because of chatter. The optimum number of passes that produces a good surface finish was found to be 3 or 4. The maximum value of compressive residual stress decreases with an increase in burnishing speed. The maximum compressive residual stress increases with an increase in burnishing depth of penetration and/or number of passes.

Experimental techniques for studying the effects of milling roller-burnishing parameters on surface integrity

The effects of cutting speed, feed rate and depth of cut on the residual stress distribution in the machined surface region caused by milling of five different materials are determined using an electrolytic etching-deflection technique. The analysis of the experimental data is carried out using response surface methodology (RSM). The results show that the residual stress is low tensile at the machined surface and increases with an increase in depth beneath the surface reaching a maximum tensile, then decreases with a further increase in depth, eventually becoming vanishingly small. The peak residual stress is found to be strongly dependent on both milling conditions and tensile strength of work material. A mathematical model correlating the process input parameters and their interactions with the residual stress is proposed.

Residual stress distribution caused by milling

The residual stress distribution in the surface region of solution treated and aged 7075 aluminium alloy workpieces that are orthogonally burnished under lubricated condition is determined using a deflection etching technique. The residual stress at the surface is low compressive and increase rapidly with an increase in depth beneath the burnished surface to a maximum compressive then decreases gradually with further increase in depth becoming vanishingly small tensile or compressive. The maximum residual stress and depth of the stressed region increase in burnishing speed, force and an increase, to some extent, in burnishing time. The results are interpreted qualitatively in terms of the variations in the amount of surface region deformation produced by changes in burnishing conditions.

Residual stress distribution in burnishing solution treated and aged 7075 aluminium alloy

In this work, a study into the conventional simple spinning of cylindrical aluminium cups was carried out. The effects of roller face angle, feed rate and roller nose radius on each of wall thickness variation, cup inner diameter uniformity, spinning ratio, roundness uniformity, surface roughness, and spinning forces during simple spinning under dry conditions were investigated. Theoretical relationships for axial and radial components of the spinning force are determined and their validity is experimentally examined. The results show that decreasing both roller angle and feed rate, and increasing roller nose radius improve most of the spinning characteristics of the spun cup for the range of parameters considered. The results could be interpreted in terms of temperature rise in the deformation zone, over-rolling and spring-back phenomena, spinning forces, and the variations of contact area between the roller and the spun metal.

M.M. El-Khabeery

Papers

Experimental techniques for studying the effects of milling roller-burnishing parameters on surface integrity

Residual stress distribution caused by milling

Residual stress distribution in burnishing solution treated and aged 7075 aluminium alloy

On the conventional simple spinning of cylindrical aluminium cups