Modification of a mouldboard plough surface using arrays of polyethylene protuberances

Surface design modifications have recently exhibited a means of reducing soil-tool adhesion. The tribological characteristics of soil-burrowing animals were employed on tillage machinery to study the effect on adhesion. Considering the characteristics of dung beetles, ultra high molecular weight polyethylene (UHMW-PE) protuberances were mounted as embossed arrays on a mouldboard plough. To investigate a suitable geometry of such protuberances, five shapes were studied (flat, semi-spherical, semi-oblate, semi short-prolate and semi long-prolate) using a combination of base diameters and protrusion heights. The dimensionless height to diameter ratio (HDR) was used to characterize the geometry. Experiments were conducted to evaluate the resultant influence of various geometrical shapes and sizes of the protuberances (base diameter: 20–50 mm; protrusion height: 0–50 mm) on lowering the ploughing resistance of the mouldboard plough in Bangkok clay soil. A comparison was made between the modified and the conventional plough in dry (21.8% (d.b.)), sticky (37.2% (d.b.)), wet (49.1% (d.b.)) and flooded (64.3% (d.b.)) Bangkok clay soil at 1, 3 and 5 km/h forward speeds. Percent reduction in ploughing resistance of bionic mouldboard plough in these soil conditions with HDR = 0 was 1–6% in dry soil, 16–22% in sticky soil, 14–20% in wet soil and 8–12% in flooded soil. With HDR = 0.25 the ploughing resistance was reduced by 2–7% in dry soil, 18–36% in sticky soil, 17–33% in wet soil and 15–28% in flooded soil. Similarly with HDR = 0.5, it reduced by 10–16% in sticky soil, 6–17% in wet soil and 12–26% in flooded soil. Whereas, HDR > 0.5 increased the ploughing resistance by 7–29%.