OBRABOTKAMETALLOV Vol. 26 No. 3 2024 technology best microhardness and roundness. With this view, in this study, roller burnishing was carried out on the Al6061-T6 alloy workpiece to model and optimize the process to obtain high microhardness, lowest roundness deviation and lowest surface roughness. The roller burnishing of Al6061 alloy specimens was evaluated under dry-cutting conditions, considering factors like cutting speed, feed, and number of passes. Mathematical models to predict the surface roughness, microhardness, and deviation in roundness were developed based on the experimental results. Materials and Design The aluminum alloy 6061 (Al6061-T6), which is widely used in general purpose applications, is used in this investigation. This alloy is renowned for its strength-to-weight ratio, corrosion resistance, and weldability, making it suitable for various structural components and popular in manufacturing processes. It is a precipitation hardening aluminum alloy. Magnesium and silicon are the two most important constituents. The main advantage of aluminum 6061 is its weldability. The selected specimen had a diameter of 30 mm, a length of 160 mm. The length of each machined surface was 50 mm. This representative part is very common in aircraft structures. The properties and chemical composition of 6061 aluminum alloy are shown in Table 1. Ta b l e 1 Chemical composition of Al6061-T6 alloy Element Al Cu Cr Mg Mn Si Zn Fe Ti Amount (wt. %) 95.8 0.15 0.2 1.1 0.15 0.75 0.25 0.19 0.15 Single roller burnishing tool with a carbide roller was used in the present study. The carbide roller is spring-loaded in the two axial directions to provide the required pressure during the burnishing operation. The worn-out carbide roller can be restored by regrinding/lapping, which will prolong the tool life. The tool with carbide roller is suitable for all outside surfaces of shafts, tapered shaft, radii, shoulders etc. and can be used on CNC lathes, turret or conventional lathes. The turned surface can be burnished up to 0.1 to 0.2 µm. Roller burnishing tool used in the present study is shown in Fig. 1. The experiments were carried out by varying the feed, cutting speed, and number of passes and at a constant depth of penetration of 0.5 mm. A design of experiment approach (DOE) was used to understand critical factors promoting consequences on sustainability indicators (surface roughness, microhardness, and roundness error). Central composite design (CCD) was used to develop empirical models and analysis of all responses. Central composite rotatable design (CCRD) test matrix with an alpha value of 1.6817 was used for the design of experiments. Each numeric parameter was varied at five levels: plus, and minus alpha (axial points), plus and minus 1 (factorial points) and the center point. In this study, twenty roller burnishing experiments were performed varying with the process parameters to develop a surface roughness, microhardness, and roundness error models. The coded levels and corresponding actual values of cutting parameters are given in Table 2. Fig. 1. Roller burnishing tool used in the present study
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