Original article Experimental investigations and statistical modeling of surface roughness during ultrasonic-assisted turning with self-lubricating cutting inserts Varun Sharma 1,2 and Pulak Mohan Pandey 1 Abstract The present paper describes the effect of cutting and vibration parameters on the surface roughness of specimen machined by ultrasonic-assisted turning with self-lubricating cutting inserts. The selected process has been based on comparative analysis between conventional turning and ultrasonic-assisted turning using plane and textured cutting inserts. An improvement of the order of 35.89% is observed during ultrasonic-assisted turning with textured cutting insert as compared to conventional turning with plane tool. The latter part of the paper uses response surface meth- odology for performing the experimentation during ultrasonic-assisted turning with textured cutting insert. The experi- mental data have been analyzed using analysis of variance to highlight significant contributions of depth of cut, feed rate, cutting speed, and percentage intensity of ultrasonic power on surface roughness. The significant interactions among process parameters have also been analyzed to explain the possible alteration in the mechanism of material removal during ultrasonic-assisted turning using self-lubricating inserts. The best surface finish of the order of 0.431 mm has been found under optimal cutting and vibration parameters as evaluated by optimization of the developed statistical model using genetic algorithm. Keywords Vibration, feed rate, cutting speed, self-lubricating, ultrasonic-assisted turning Date received: 9 January 2017; accepted: 17 September 2017 Introduction In machining processes, surface roughness can be taken as one of the criteria to evaluate the machining performance. In order to meet functional require- ments of an object, surface roughness plays a signifi- cant role. The reliability of the machined part not only depends upon material but also on the conditions of machining. Several properties like wear resistance, endurance limit, fatigue life are highly dependent upon state of machining. 1,2 It has been reported that grinding can be replaced with turning process while performing finishing operation of difficult to cut materials. 3,4 This not only reduces the manufacturing cost by 30 times but also enhances the productivity. Turning is the most extensively used machining pro- cess in manufacturing industry. However, in order to meet the environmental obligations, industry has focused on dry or near dry machining processes. 1–4 Recently, ultrasonic-assisted turning (UAT) has been developed to machine difficult to cut mater- ials. 5–10 It involves imparting high frequency and low amplitude vibrations to cutting tool. This in turn helps to have a periodic separation between cutting tool and workpiece. 5–7 Several researchers 7–9 have reported that UAT resulted in low cutting forces, better surface finish, generation of compressive residual stresses, etc. This process has also been found to be beneficial in terms of suppression of burrs and to attain better dimensional accuracy of machined specimen. 8–14 In this regard, Wang and Zhao 12 found surface finish was improved by four times during UAT as compared to conventional turning (CT) process. This was accounted due to the reason that UAT resulted in more stable machining regime with no built up edges (BUE). Lin and Chang 13 reported ultrasonic frequency and amplitude to significantly Proc IMechE Part E: J Process Mechanical Engineering 0(0) 1–14 ! IMechE 2017 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0954408917738127 journals.sagepub.com/home/jpme 1 Department of Mechanical Engineering, IIT Delhi, Delhi, India 2 Department of Mechanical Engineering, BITS Pilani, Pilani, Rajasthan, India Corresponding author: Pulak Mohan Pandey, Department of Mechanical Engineering, IIT Delhi, Delhi, India. Email: pmpandey@mech.iitd.ac.in