# Integrated Image Processing Toolset for Tracking Direction of Metal Grain Deformation
## 2 Data Acquisition Procedures  
In this study, two variations of the specimen were utilized for the experiment, namely raw and weld specimens. A metallographic observation, including processes to prepare the specimen such as cutting, mounting, grinding, polishing, and etching based on ASTM E3-11, was used to acquire the dataset [48]. The experiment was conducted using a 9 \(\times\) 25 \(\times\) 25 mm (width \(\times\) length \(\times\) height) specimen made from structural carbon steel (ASTM A36) (Figure 2). The specimen was mounted on phenolic mounting resin that was 35 mm in diameter and 27 mm in height. The specimen was then subjected to medium and fine wet-grinding processes using silicon carbide grinding paper in successive steps: P200, P400, P800, P1200, and P2000 (with ultrasonic distilled water cleaning between each step). An automatic rotation grinding machine was used to maintain a constant pressure and angle at each stage. Wet grinding was utilized in this study to avoid potential side effects owing to frictional heating, such as melting, tempering, and grain transformation. Finally, fine polishing was performed for 20 s using a polycrystalline diamond paste with a grid size of 1 \(\upmu\)m. The preparation was completed by chemically etching the specimen for 5 s in 6 g of nitric acid (concentration of 4.41%) diluted with 30 g of ethanol, followed by cleaning with distilled water using an ultrasonic cleaner for 30 s and ethanol cleaning for 10 s. The etchant process was repeated four times to obtain a clear grain image upon a microscopic examination. Microscopic examination was performed using the optical microscopy method with two scope lens variations, i.e., 50- and 200-scope lenses with spatial resolutions of 370 and 92.5 nm, respectively. The microscope was paired with two external devices: a 12 MP CMOS camera with a 1.7-in. sensor size and a 3-axis stage motor to control the specimen movement. The 50-scope lens was used to inspect all the surfaces of the specimen consisting of 19-by-10 images. The stage motion was controlled using the stage motor, with the imaging intervals of 14 and 10 mm in the \(x\) and \(y\) directions, respectively, covering up to 312.4 mm\({}^{2}\) of the surface area. Similarly, the 200-scope lens was used to inspect 190 locations with a random start point inside the range covered by the 50-scope lens image. The imaging intervals were 3.6 mm and 2.7 mm in the \(x\) and \(y\) directions, respectively, covering up to 19.5 mm\({}^{2}\) of the surface area. Using this approach, the time required to examine the specimen was considerably reduced, with a high flexibility in tracking specific target locations as the analysis required high spatial resolution images to track the microscopic deformation of the grain. If micrographs covering an area of 312.4 mm\({}^{2}\) were obtained using the 200-scope lens, up to 3.040 images would have been required to cover the entire surface area. However, in this study, the objective of the tracking of the exact location of a specific grain while capturing the entire area of the specimen was achieved with only 190 images. Thus, integrating low- and high-scope lens images facilitated extracting the grain location while flexibly picking a specific target to analyze the deformation. Metallographic observations and assessments were performed to visualize and analyze the grain geometry during the 4-point bending test (\(\delta\) = 0.2 mm), as shown in Figure 3. This experiment was prepared using a 150 \(\times\) 9 \(\times\) 49 mm (width \(\times\) length \(\times\) height) specimen made from structural carbon steel (ASTM A36) subjected to the same metallographic treatment steps as previously described: grinding, polishing, etching, and a microscopic examination. The observation was conducted on compressive, tensile, and a combination of compressive and tensile stress areas. This dataset contained the deformation of metal grains owing to external forces, thereby indicating the performance when analyzing the direction of the grain deformation.