From single asperity to real scale in the wear of agricultural tine

Abstract

One of the main challenges in tribology of agricultural tools is establishing a relationship between lab-scale testing and real applications. Nevertheless, the wear micro-mechanism stands as an effective mediator amid different test scales. In this research, different scale of testing (1) in-field testing of agricultural tines (real scale), (2) intermediate test using ASTM G132 tester (macro scale/multi-asperity test) and (3) single asperity testing using scratch tester (micro-scale) were performed. A relationship was established between different scales based on the qualitative output (wear micro-mechanism) and validated using the quantitative data (degree of penetration (Dp) using 3D profiles and wear). Test variables such as particle geometry/nose radius (22 µm − 200 µm), attack angle (90°–120°) and normal force (4.5–24.2 N) were adapted to achieve various micro-mechanisms. From real scale tests, co-existing micro-mechanisms were observed, amongst which micro-cutting was the dominant mechanism responsible for material removal. Dp value 0.4 representing micro-cutting at the cutting edge contributes significantly to the reduction in service life of the tines. Dp corresponding to micro-cutting was prevalent in the intermediate test, and in the single asperity test micro-cutting was experienced with samples tested at 25 µm nose radius. The cross-sectional analysis revealed the tribo-layer formation in the test material for both real scale and multi-asperity testing. The in-situ vision observations on single asperity testing elucidate the transition in micro-mechanism. Considering the three scales of testing, it is evident that the degree of penetration, wear micro-mechanism and wear rate are in-line with each other. This novel approach in linking different scales can be extended to other abrasion prone applications such as mining, drilling, etc for material selection.