Research On Stress-Strain Constitutive Relationship For Bionic Non-smooth Wearable Surface

Frictional wear can be one great problem to be solved urgently in engineering field. Investigators have paid more attention on surface antifriction technology coupled with the development of tribology and the application of many machines since Industrial Revolution. Many big progresses are made in that field in the past decades and antifriction material innovation,new process,novelty came into being. But those study work are mostly focus on the design and exploitation of new style antifriction material.In recent years, bionics develops quickly and offers a new clue to solve the problem. Bionics is a subject that studys and learns from biology which have the perfect characteristics, in order to supply innovation and new technology to solve the problem for engineering field. On the foundation of the systematic investigation of the desorption and drag reducing mechanism for lots of soil animals ,such as dung beetle,earthworm,pangolin and so on, the biology non-smooth wear resistance theory was advanced by the Key Laboratory for Terrain-Machine Bionics Engineering, Ministry of Education, Jilin university. Combining with practical engineering application, researchers of that laboratory invented the bionic non-smooth antifriction technology, which had been applied successfully to bionic plough, bionic bulldozing plate and roll etc.Researchers have made various discussions on the mechanism of the bionic non-smooth antifriction, but has not formed the perfect scientific treatment.In consideration of above, model test and computer simulation for samples were employed to discuss and study the biology non-smooth wear resistance mechanism from the view of stress-strain constitutive relationship, at the same time that can offer reference frame for its application in the future. Based on laboratory investigation, four types of samples with concave non-smooth surface and one kind of samples with smooth surface are designed. Unlubricated friction abrasion comparative test was made between samples with concave non-smooth surface and smooth surface by the method of experimental optimum design in the same test condition. The antifriction mechanism of non-smooth samples was discussed through the test data and curve of friction coefficient, mostly including analysis of the difference of friction coefficient between smooth and non-smooth surface and why the wear rate of samples with concave non-smooth surface is less than that of samples with smooth surface. Preliminary interpretation for that question was given in this paper. In author's opinion, the critical points are as follows: first, in the process of friction attrition test, because concaves exist on the non-smooth surface of sample and air can be stored in concaves. During the test, that makes partial contact surface replaced by air film, simultaneously the concave has micro distortion in the load condition. That makes the air which was stored in the concave be extruded and accelerated its flowing speed, thus results in certain degree air lubrication on the contact compound surface. Therefore compared with the smooth model, friction coefficient of the non-smooth model reduces. Second, any samples'surface can not be smooth absolutely. Microscopic shape will be produced by the processing method during the manufacture process, that is surface roughness and corrugation. When such surface contact with each other, only a few mico-convex body crown contact with another one and bear the load. More over, there will be 10 nm or more clearance exists on the rest surface. In fact, the clearance space out the contact surface completely and make no effect happened. These discrete areas formed the real contact area. Therefore, the concaves that exist on the non-smooth samples make the real contact area reduced in the test, at the same time that cause the opportunity of micro convex body participate in the friction diminished; similarly, the effect exists between frictional plate and samples in the wear test. That means convex waken the wear act between friction pair and enhance the resistance to scratch of the working surface, simultaneously, the power for the whole system overcome frictional drag reduced, therefore the abrasion reduces in per unit rotation. Then, one supposition that bionic convex alleviate partial great stress of the working surface to some extent was proposed, thus the surface abrasion reduce.Model test and computer simulation for samples were employed to study the possibility mentioned above in the following chapter. Surface stress was tested for smooth and non-smooth sample in the compression state. It shows that the stress of non-smooth model surface test point is lower than the smooth surface prominently, except test point three. In order to study the stress distribution condition roundly, ANSYS finite element simulation was carried on. Through comparison of tested data and computed one, the rationality of the latter is determined. And then, the slow-release effect of stress was proposed in the paper by stress analysis and contour study of stress. That means, compared with smooth sample, the rigidity of any concave reduces greatly in the same stress condition. That can reduce or slow release the stress strength which makes a contribution to wear. Moreover, because many concaves on the surface work together, cause the low stress distribution area extended between concaves.