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

340

8

one for predicting Ra has an R 2 equal to 97.29% and the one for predicting Rt, has an R 2 equal to 96.76%. This implies that the prediction models are capable of explaining the variation in terms of cutting conditions as successfully as their coefficients of determination. This outcome obviously displays that the aforementioned predictive models may be utilized for predicting the objectives studied in this work, at least in the specific operational range of parameters.

Fig. 8. Comparison of experimental and predicted results for Fc.

(a)

(b) Fig. 9. Comparison of experimental and predicted results for: (a) Ra and (b) Rt.

5. Conclusions and future perspectives

In this study an experimental investigation on machinability parameters in turning of CuZn39Pb3 brass alloy was conducted. Machinability was studied in terms of arithmetic mean surface roughness Ra ( μ m) , maximum surface roughness Rt ( μ m) and main cutting force Fc (N) as responses affected by the cutting conditions; rotational speed n (rpm) ; feed rate f (mm/rev) and depth of cut a (mm). An L18 mixed-level Taguchi design of experiments was estab lished to formulate the design space as per the operational range of machining parameters and their corresponding levels. According to the results obtained, it was concluded that cutting conditions as well as their interactions differ ently affect the aforementioned machinability objectives. Main cutting force is minimized by employing low speeds and low-to-moderate feeds whilst roughness parameters Ra and Rt can be minimized by applying high speeds combined with moderate feeds for a depth of cut equal to 1.0 mm. Full quadratic predictive models were generated via regression analysis and good correlation was achieved between experimental and predicted results for all responses. Experimental results have shown that depth of cut holds dominant effect of cutting force whilst its contribution equals to 73.61%. Rotational speed and feed rate have just as important effect on arithmetic surface roughness average with 38.85% and 32.15% contributions respectively. For the maximum height of the profile, rotational speed has a