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Study on the Anti-wear Characteristics of Bionic Structure under Oil Lubrication

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Tutor: CongZuo
School: Jilin University
Course: Agricultural Mechanization Engineering
Keywords: Bionic coupling,Through-hole structure,Lubrication,Friction pairs,Wear law,Anti-
CLC: TH117
Type: PhD thesis
Year:  2007
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Abstract:
Wear is the main failure form and the initial failure causes of the mechanical equipments. Statistic data about the mechanical equipment failure causes show that 70% of the failure is directly due to wear. Therefore, the "wear" is vividly termed "chronic cancer" in the machinery industry. As the result of the friction, under the premise of mechanical equipment can not avoid friction, wear is an inevitable phenomenon. Nowadays, mankind is faced with a lack of resources, serious pollution and other environmental problems, so that some efficient, energy-saving, environmentally sustainable strategies had been proposed. Dating back to the specific link, the main thing is to solve the energy consumption caused by friction resistance in the industry, and to resolve the environmental pollution, resources waste, security risks, and reliability and life issues caused by mechanical wear.Based on the bionic non-smooth wearable theory and typical surface wear properties of the soil animals, the wear bionic wearable technique was studied by means of friction pairs of the mechanical equipment. Due to the complexity of tribological system, it is very difficult to obtain accurate, quantitative wear mechanism, furthermore, there are a lot of assumptions in the theoretical analysis and simulation, so there is no way to really simulate the friction and wear behavior under the lubrication conditions. Therefore, combining sample tests with worn appearance analysis for weared samples, the basic theory of bionic technology for mechanical friction pairs was studied. According to the working conditions and characteristics of the mechanical friction pairs, it was proposed that both anti-wear characteristics of the double pairs was taken as the anti-wear characteristics of the mechanical friction pairs, and based on it anti-wear characteristics index and the research project were established.The anti-wear characteristics of typical sliding friction pairs (piston-cylinder system) were analyzed by means of the test for selecting and optimizing the influence factors of the bionic unit using JF150D friction tester. The main purpose of the paper was to provide new ideas, methods and experimental basis for the development of anti-wear technique of mechanical friction pairs in the mechanical engineering.According to anti-wear surfaces of typical soil animals, some bionic specimen surfaces were designed: hollow pit surface, through-hole surface, through-hole surface with leading angle, and through-hole surface with chamfer groove, and the wear and friction experiments were performed respectively. The experiment results showed that except the wear of hollow pit surface, the wear of through-hole surface, through-hole surface with leading angle, and through-hole surface with chamfer groove samples significantly reduced compared with the wear of flat surface sample. Under the conditions of lubrication experiment of once drip (stress of 245N) and continuous drip (stress of 490N), through-hole surface sample possessed obvious lubrication and anti-wear characteristics. Compared with the flat surface samples, in the same experimental conditions the wear of the through-hole surface was reduced by more than 80%. Even in the dry friction conditions (stress of 306N), the wear was also reduced by 30%. According to the experiment, through-hole surface samples were selected.Under the condition of continuous drip lubrication and the pressure of 612N, the orthogonal test was performed by using the selected through-hole surface sample, and the purpose was to study the influence of diameter and spacing of the through-hole surface samples on the wear. The results showed that the bionic through-hole surface possessed the best lubrication and wear-resistance. Compared with the flat surface samples, in the same experimental conditions the wear of the through-hole surface was reduced 48-60%. On the basis of orthogonal regression analysis the relationship between independent variable ( z1 -diameter/mm, z 2- spacing/mm) and wear ( y|^_m /mm) was obtained, that was.The influence of the load on the wear was studied, which was under the condition of continuous drip and the pressure of 0.39-1.82MPa, the influence of the pressure of the through-hole surface samples and flat surface samples on their wear. Test results showed that with the increase of pressure, the wear was gradually increasing. Based on observation to the wear of the sample surface, it was seen that the best work load of the through-hole surface sample made of LY12 hard aluminum alloy materials was less than1.0MPa. Compared with the flat surface sample, its wear was significantly reduced, and its wear surface has no significant wear and dry friction marks. Under the higher pressure of 1.82MPa, the wear-resistance of the through-hole surface sample with diameter of 3.5mm was of 44% higher than that of the flat surface sample. However, because the wear interface had obvious wear grain and deeply anxious traces, the experiment condition was not suitable for application in practice.Then due to the cylinder surface with flatten peak mesh texture had good anti-wear characteristic, three kinds of mesh textures on the through-hole surface sample were designed and tested. The test results show that with the low-load, the mesh texture has little contribution to the wear-resistance, and with the high load, the contribution of the mesh texture was shown. Because the influence of the through-hole structure on lubrication is bigger than that of the mesh texture, it was concluded that mesh texture was suitable to the application in fixed friction pairs, and it was not fit for application in sliding friction pairs.The experiment results showed that through-hole structure was characterized by stable and credible anti-wear, and was suitable to resolve friction and wear problem in mechanical wear pairs.The worn appearance of the samples was observed. The results indicated that the wear feature was slight adhesive grain on the sample tail and slight adhesive loss on the foreside of the through-hole. Compared with flat surface samples, the wear surface of the through-hole surface samples had no obvious wear accumulation and spread phenomenon.By using the software ANSYS the stress of the through-hole surface samples was simulated. The simulation results show that the interior stress and interface pressure of the through-hole surface samples distribute evenly. It was seen that the through-hole of samples increased the contact area of the interface friction, and ultimately reduced the wear. Through the observation of worn appearance, the influence of through-hole structure on lubrication process was analyzed. It indicated that under the lubrication conditions the existence of the through-hole reduced dry friction, and avoided the continuous partial dry friction.By analyzing the worn appearance, contact stress and interface lubrication, the wear-resistance mechanism of the through-hole surface samples were revealed. Based on the factors coupling relations in friction process, it was indicated that the reason that through-hole structure reduced the wear was the interaction of other affecting factors reduced the wear indirectly or directly.In short, on the basis of bionic theory the basic study on anti-wear ability of the mechanical wear pairs was performed. The basic study not only verified that the bionic structure had effective anti-wear ability, but also provided a bionic wear-resistance model which was suitable for mechanical friction and wear application, resolving the wear problem of the mechanical wear pairs. The method was not dependent on material improvement, surface enhanced, but only to use of low-cost, simple implementation process, and these were the original intention of this paper. As a brand new solution to the wear problem, the conclusion of this paper can provided a new method for solving wear and friction problem in the machinery industry.
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