PSI - Issue 10

N.M. Vaxevanidis et al. / Procedia Structural Integrity 10 (2018) 333–341 N.M. Vaxevanidis et al. / Structural Integrity Procedia 00 (2018) 000 – 000

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Fig. 2. Indicative graph of the cutting forces measurement from a turning experiment.

3. Results and discussion

3.1. Experimental observations

The variations of the measured Ra , Rt and Fc values in correspondence to experimental runs are presented in Figs. 3(a,b), respectively. It is seen that surface roughness decreases with increasing cutting speed and decreasing depth of cut and feed rate in the case of steels (Vaxevanidis et al. (2010); Galanis and Manolakos (2010)); such a behavior was not observed for the CuZn39Pb3 brass alloy. During the present series of experiments it is observed that high values for rotational speed in relation to moderate feeds are necessary to minimize roughness, whilst combinations of low speeds and low-to-moderate feeds favor the minimization of main cutting force (Figs.3(a,b) with reference to Table 2). These observations are, in general, in agreement with previous reports; see Gaitonde et al. (2012) and Klocke et al. (2016).

(a)

(b) Fig. 3. Results corresponded to experimental runs: (a) Roughness parameters Ra and Rt ; (b) Main cutting force Fc .

For constant rotational speed 800 rpm, Fc reduces when using lower values for depth of cut. As far as feed rate is concerned, Fc increases for f =0.1 mm/rev and f =0.33 mm/rev whilst for f =0.18 mm/rev seems to reduce Fc for all three levels of depth of cut (Fig.4a). For the same constant rotational speed n =800 rpm, Ra is reduced when operating with the middle level of cutting depth a =1.0 mm. Feed rate equal to 0.18 mm/rev is beneficial to Ra when using depth of cut a =0.5 mm and a =1.0 mm. For the second level of depth of cut, i.e., a =1.0 mm, increase of Ra is less profound under f =0.33mm/rev. The opposite trend in terms of Ra is observed when cutting with depth of cut a =1.5 mm. Ra in creases for depth of cut a =1.5 mm and f =0.1 mm/rev and reaches its highest value for f =0.18 mm/rev (Fig.5a). Rt exhibits reduced values under f =0.18mm/rev for the second and the third level of cutting depth; 1.0mm and 1.5mm whereas a different trend is experienced under a =0.5 mm. Rt seems to gradually increase towards higher values of feed rate under a =0.5mm (Fig. 6a).