Biomimetic Geometrical Structure Surfaces With Anti-abrasion Function And Their Abrasive Wear Against Soil

The abriseve wear is one of the main failure modes for soil-engaging components of agricultural machines and construction machines. Many researches were focused on improving the abrasive wear resistance of machine components. The abrasive wear depends upon both the properties of component materials and the geometrical structures of the component surfaces. The geometrical surface structures would change the interface interaction and dynamic properties. The acting force, speed, energy distribution and its dynamic change of contact interface between abrasive and component will significantly influence the wear of soil-engaging surface. Biomimetic geometric structure surfaces with anti-abrasion function were designed learning from the geometrical biosurfaces with anti-abrasion function; their abrasive wear against soil were carried out; their experimental examination were run; and, finally, their numerical simulation and machanisim analysis in the present work.Surfaces of both the pangolin (Manis pentadactyla, a type Soil burrowing animals) scale and chlamys farreri (a species of mollusc) shell have anti-abrasion geometric structures. There are many ridges on their outside surfaces. It was found that the sections of the ridges can be expressed with sine function f ( x)= asin(bx+c) (where, a, b and c are real number, a≠0, b≠0). Biomimetic abrasive wear resistant geometric structure surface ridges were designed according to the biosurface geometry and its anti-abrasion function. It was found from the quantitative analysis of the shape of clam (Mactra) shell that the clam sheel has wearable convex shell character. The spherical segment of the shape of clam can be described by function ( ) ( )x? a 2 +y?b2+(z ?c)2=r2( r > h>0). Biomimetic wearable embossed surfaces with convex domes were designed according to this function. It was found from the quantitative analysis of the shape of the outside shell of Babylonia Areolata that the outside shell surfaces display step form geometry. The secions of the steps are right-angled triangles, which have three internal angles of 30o, 60o and 90o respectively. Based on the trigonal geometry of the outside shell of Babylonia Areolata, the bioimimetic step form geometric structure surfaces were designed. The exposed parts of pangolin scales were measured using OLYCIA P3 image analysis system and it was found that the exposed parts display symmetric hexagon geometric structure; L2/L1=1.175, where, L1 is the length of the hypotenuse of symmetric hexagon and L2 is the length of the vertical border of the symmetric hexagon; the height difference between center ridge and fringe is 2-3.5mm. Wearable biomimetic scalelike geometric structure surfaces were designed using structure biomimetics theory.The measurement method of the wear volume loss based on the reverse engineering was investigated. Two measurment methods of abrasive wear volume loss based on reverse engineering technology were compared The results showed that the reverse engineering technology can give reliable resultes with good repeatability; the precision of the two measurements are 97.35%和96.92%, respectively.The orthogonal experiments of the abrasive wear of varied biomimetic geometrical structure surfaces designed biomimetically were conducted. The results showed that the distance between two adjacent biomimetic geometrical units, abrasive particle size and related sliding speed of samples with abrasive material had significant influence on experiment results of the biomimetic embossed surfaces with convex domes with the significance levels of 0.01. The sliding speed was the primary impacting factor, the distance was the secondary and abrasive particle size was the least. It was found from the orthogonal experiment resultes of the abrasive wear of the scalelike geometric structure surfaces that the distance between two adjacent biomimetic scalelike units had no significant influence on abrasive wear property, but both of the sliding speed and abrasive particle size had significant influence on abrasive wear and the related sliding speed was the primary significant factor as well. It was found form the orthogonal experiments of the abrasive wear the ridge type biomimetic geometrical structure surfaces that the sliding speed had significant influence on the experiment results with the significant level of 0.01. The distance between two adjacent biomimetic scalelike ridges had a certain effect on experiment results with significant level of 0.01 and abrasive particle size had no significant influence on experiment results. It was found that from the test results of the abrasive wear of the common smooth plate that both abrasive particle size and sliding speed had significant effects with significant level of 0.01 and the related sliding speed was the main factor. The effect of the sliding speed on experiment results is more significant than that of abrasive particle size. Generally, four biomimetic geometrical structure surfaces, including embossed surfaces with convex domes, ridges, steps and scalelike units, have higher anti-abrasion property than the conventional smooth surface, in particularly, the anti-abrasion property of step form and ridge form biomimetic surfaces have higher anti-abrasion propery than the other structure surfaces. The the abrasive volume of the biomimetic geometrical units (convex domes, steps, ridges and scalelike units) were examined and it was found from the experimental resuls that the abrasive volume of the biomimetic geometrical units decreased along the sliding direction of abrasive material, indicating that the geometrical structure units can improve the wearability of biomimetic surface and front units have protective function to the hinder units. The experiment results showed that the wearability can be improved if the biomimetic geometric structure units are made from wearable materials.Discrete element mumerical simulation for the abrasive wear of some biomimetic geometrical structure surfaces was carried out. It was demonstrated that the results of the computer simulation were in concordance with the experimental resultes, suggesting that the discrete element method can substitute for real experiments or improve the optimization designs of biomimetic geometrical anti-abrasion surfaces. A three-particle analysis model was established. A systemic analysis of abrasive wear machanisims of biomimetic geometrical structure surfaces was carried out using discrete element method and it was concluded that shear layer effect, guidance effect and rolling effect are the main anti-abrasion mechanisms of the biomimetic geometrical structure surafacs.