3D finite element analysis of ultrasonically assisted turning
Introduction
Turning is a type of metal cutting where a single-point tool is used to remove unwanted material to produce a desired product, and is generally performed on a lathe machine. Turning techniques have been improved considerably to achieve easy machining of difficult-to-cut materials and better surface finish. Methods such as high speed turning have been in use now for considerable time. But still machining of high-strength aerospace alloys, composites and ceramics causes high tool temperatures and fast wear of cutting edges, lacks dimensional accuracy and requires a considerable amount of coolant. These deficiencies of conventional turning necessitate the development of new cutting techniques.
Ultrasonically assisted turning (UAT) has proved to bring significant benefits to machining of hard-to-cut alloys. It is an advanced cutting technique, where high-frequency vibration (frequency f ≈ 20 kHz, amplitude a ≈ 15 mm) is superimposed on the movement of a cutting tool. Compared to conventional turning (CT), this technique allows significant improvements; a multifold decrease in cutting forces, as well as an improvement in surface finish can be achieved with the use of UAT [1], [2].
Despite all its advantages, this technique has not yet been widely introduced in the industry. Problems such as instability of the cutting process that resulted in poor surface finish prevented the full implementation of this process. The development of an autoresonant control system [3] added stability to the system by making the vibrations regular, thus opening the way to the industrial introduction of UAT.
A prototype of the UAT system has been designed at Loughborough University, UK, and a program of experimental tests has been implemented confirming advantages of UAT in comparison to CT. Dynamics of UAT as a non-linear vibro-impact process was studied in [4], and the amplitude response of the cutting tool under loading was analysed for this cutting technique.
However, thermomechanics of the tool–workpiece interaction, which is of special importance for the regime with multiple microimpacts in the process zone, and other specific features of the cutting process in UAT have not been fully understood. The finite element method (FEM) is a main computational tool for simulation of the process zone and of the tool–workpiece interaction in metal cutting. A detailed review of FE models of conventional cutting can be found in the monographs [5], [6]. In order to understand the mechanics of tool–chip interaction in UAT, and to analyse distributions of stresses and strains in the cutting region, heat transfer in the workpiece material and in the cutting tool and also to estimate the cutting forces, a 2D finite element model was developed. An initially purely mechanical finite element model was further improved, resulting in a transient, fully thermomechanically coupled one for both UAT and CT. Some computational results obtained with this mode were discussed in [7].
The current paper discusses the 3D FE model of UAT that was developed as extension to the 2D model. Up to now, 3D FE models were used to simulate conventional cutting processes. The majority of the suggested schemes employ the method of chip separation along a predefined surface, “unzipping” adjoining finite elements in the initial discretization of the area, hence reducing flexibility (and adequacy) of the analysis. Only a few schemes use other techniques, such as elements deletion based upon penetration of cutting tool tip into the elements of workpiece [8], adaptive remeshing of elements in the workpiece [9], and combination of both the manual deletion and remeshing [10].
A FEA analysis of heat generation in machining of isotropic materials was conducted in [11] in order to study the effects of the convective heat transfer. A different approach, using an orthogonal FE model coupled with an analytical 3D model of cutting, was developed in [12] to predict a chip flow angle and three-dimensional forces in the tool. Another 3D model was introduced in [9] that took into account dynamic effects, thermomechanical coupling, constitutive damage law and contact with friction in order to study the cutting forces and plastic deformation.
With 3D modelling of CT being used for the study of tool forces and chip flow for the last two decades, this paper presents the first three-dimensional FE model of UAT. It has been recently developed and the computational results, emerging from this 3D formulation, are discussed.
Section snippets
General features
A detailed description of our previously developed 2D numerical model can be found elsewhere [7], [13]. The current FE model utilizes the MSC MARC/MENTAT FE code [14] and is based on the updated lagrangian analysis procedure that provides a transient analysis for an elasto-plastic material and accounts for the frictional contact interaction between the cutter and workpiece as well as material separation in front of the cutting edge.
The relative movement of the workpiece and cutting tool in CT
Results of simulations and discussion
All variants of numerical (finite element) simulations below are performed for two cutting techniques (CT and UAT) with identical parameters so that results for CT could serve as a reference for UAT. Two contact conditions are considered at the tool–chip interface: (a) a frictionless contact, and (b) a contact with friction (coefficient of friction μ = 0.5). The former case corresponds to the well-lubricated cutting process, with heat generation occurring only due to plastic deformation
Conclusion
3D thermomechanically coupled FE approach is used to model ultrasonically assisted turning (UAT), with conventional turning (CT) being a basis of comparative analysis. The use of the 3D model allowed the study of three-dimensional chip formation predicting distributions of stresses, strains, cutting forces and temperatures in the workpiece and cutting tool. This model allows studying various 3D effects in turning, such as oblique chip formation, as well as the influence of the tool geometry on
Acknowledgements
The authors would like to acknowledge the help of Dr. Alan Meadows and Mr. Peter homas in conducting experiments on the UAT prototype.
References (18)
- et al.
J. Mater. Process. Technol.
(2004) - et al.
J. Mater. Process. Technol.
(2003) - et al.
Mechatronics
(2004) - et al.
Ultrasonics
(1998) - et al.
J. Mater. Process. Technol.
(2004) - et al.
Comput. Methods Appl. Mech. Eng.
(2004) - et al.
J. Mater. Process. Technol.
(1999) - et al.
Int. J. Heat Mass Transfer
(1999) - et al.
Int. J. Mach. Tools Manuf.
(2002)
Cited by (69)
A transient cutting temperature prediction model for high-speed ultrasonic vibration turning
2022, Journal of Manufacturing ProcessesCitation Excerpt :Similar with [9], Zhang et al. [11] built a transient time-varying temperature model, who also took the flank face extrusion effect into concern and calculated the effect of the tool coating [12]. As for ultrasonic vibration cutting temperature modeling, based on the above theoretical development, the finite element method [13,14] was utilized to help calculate the cutting temperature fields and the research was mainly focused on milling by adding the influence of ultrasonic vibration. Liu XF et al. [15] developed an axial ultrasonic vibration-assisted milling temperature model in which cutting force and cutting heat generation were discussed as a whole and the accuracy was validated by measuring the workpiece temperature.
Surface integrity and microstructure changes in 3D elliptical ultrasonic assisted turning of Ti–6Al–4V: FEM and experimental examination
2020, Tribology InternationalCitation Excerpt :As a result, it was seen that the grain size has been reduced in UAT less than CT process. Although the simulation of linear and 2D elliptical vibration turning (excluding grain size) were carried out in different papers [6,18,27,28], the simulation of grain size were mostly exerted in conventional turning (as it was reviewed). Therefore, in the present work, the simulation of 3D elliptical vibration turning (including grain size) is carried out in 3D turning of Ti–6Al–4V alloy.
Processing technologies for Nomex honeycomb composites (NHCs): A critical review
2020, Composite StructuresStudy on the performances of the drilling process of nickel-based superalloy Inconel 718 with differently micro-textured drilling tools
2020, International Journal of Mechanical SciencesTool wear modeling in rotary turning modified by ultrasonic vibration
2018, Simulation Modelling Practice and TheoryCitation Excerpt :Amini and Kazemiyoun [13] claimed that sticky zone in tool-chip contact length was reduced in UAT, due to existence of cooling cycle during each tool-chip disengagement time. Ahmed et al. [14] showed that the value of friction factor is very effective on heat generation in the cutting zone where they simulated UAT in two-dimension. By adding ultrasonic vibration, about 40% reduction in cutting force was reported by Patil et al. [15].