Multi-response optimization of tensile strength and total elongation of aluminum 7075 plate after surface grinding

Abstract

Aluminum 7075 (AA7075) thin plates are used extensively in engineering industries for manufacturing of parts. The tensile strength and total elongation of the thin plates may be altered after dry surface grinding operation. The main goal of this work is to obtain optimal settings for the tensile strength and total elongation of AA7075 thin plates after surface grinding. AA7075 thin plate samples were ground at room temperature with respect to the design of experiment schedule and their tensile strength and total elongation were determined from the DI-CP/V2 Servo-hydraulic testing machine. It was found that the most influencing factor for tensile strength is grinding depth with a p-value of 0.000. It was also discovered that increasing the grinding depth increases the tensile strength and vice versa. The rest of the factors such as table speed and feed were discovered to be insignificant with p-values of 0.937 and 0.820, respectively. It was found that there is a linear relationship between the grinding parameters and the tensile strength. The most influencing main effect factor for the total elongation is table speed with a p-value of 0.053. It was found that as the table speed increases the total elongation also increases and vice versa. The two-way interactions for total elongation are significant with the most influencing interaction being the feed-grinding depth interaction with a p-value of 0.011. It was also found that there is a non-linear relationship between the predictor variables and the total elongation. The model for predicting tensile strength is significant and has R-squared of 87.01 % and this shows that the model fits the data well. The R-squared (adj) shows that the model accounts for 85.36 % of the variation in tensile strength. The model for total elongation is significant with an R-squared of 56.88 % and this denotes that the model moderately fits the data. The R-squared (adj) denotes that the model accounts for 34.70 % of the variation in total elongation. The poor predicting ability of the model for total elongation may be attributed to the presence of non-linear relationships between the independent variables and the total elongation (ductility). The optimal settings for tensile strength and total elongation were found to be moderate table speed (15 spm), high feed (5 mm) and high grinding depth (1.0 mm).