| Cotton is an important economic crop and strategic supplies in China.It plays an important role in national defense,medicine and industry.The mechanized harvest of cotton has become an effective way to promote the development of cotton industry in China.As a large cotton harvesting equipment,the cotton picker has been widely used in Xinjiang due to its advantages such as fast,convenient,and low labor intensity.Spindle is the most used key core component of the cotton picker.Hook tooth is the key structure of the spindle hook and winding cotton,which is easy to wear.Aiming at the problem that the spindle hook teeth are easy to wear,this thesis explored the wear failure process of the spindle hook teeth and analyzed the wear failure mechanism of the spindle hook teeth.The passivation modification of the spindle hook teeth was carried out.And the effects of the modification of the hook teeth on the picking performance and wear resistance were verified by field experiments.The main research contents of this thesis are as follows:(1)Experimental study on wear failure process of spindle hook teeth under field operation conditions.In order to explore the wear failure process of spindle hook teeth under field operation conditions,the spindle samples obtained under different working areas were cut and prepared,the wear morphology of the spindle hook teeth was characterized,and the wear area and coating thickness of the spindle hook teeth were extracted.The results show that there are structural defects such as microcracks,pits and pits on the surface of the new spindle coating.After a certain area of field operation,scratches appeared on the coating of the spindle hook teeth.With the increase of the working area,the coating peel off,scratches and oxide particles are exposed on the surface of the substrate,and the wear rate is accelerated.The wear of the spindle hook teeth begins to appear from the front tooth tip and the rear tooth tip,extends to the tooth edge and the back of the tooth,and then extends to the doffering edge to form a’long boot’-like wear area.With the increase of the working area,the wear area of the spindle hook teeth gradually increases,and the rate of rise in wear area increases.The coating thickness of new spindle hook teeth decreases with the rise of the number of the hook teeth.With the rise of the working area,the coating thickness of the no.1～12 hook teeth decreases.(2)Wear failure mechanism and structural modification of spindle hook teeth.Based the analysis of the cotton picking mechanism of the cotton picker,the stress analysis and finite element simulation analysis of the spindle picking and the cotton removal process were carried out.The wear failure mechanism of the spindle hook teeth was revealed,the hook teeth structures were modified.And the cross-section morphology of the hook teeth of the unmodified and modified spindles was characterized,and the radius of the teeth edge was extracted.The results show that the radius of the teeth edge of unmodified spindle hook tooth is about 0.025-0.036 mm,and the radius of the teeth edge of modified spindle hook tooth is about0.045-0.060 mm.(3)Experimental study on the effect of hook tooth modification on picking performance.In order to explore the influence of hook tooth modification on picking performance,the collect rates of the two kinds of spindles under different working areas were measured.The results show that,compared with the new spindle,the collect rate of the modified spindle is 0.2%lower than that of the unmodified spindle.With the increase of the working area of the cotton picker,the rising rate of the collect rate of the modified spindle is greater than that of the unmodified spindle.When the working area reaches about 200 hectares,the collect rate of the two spindles is not much different.However,when the working area is more than 200 hectares,the collect rate of the modified spindle is greater than that of the unmodified spindle,and the two kinds of spindles continue to rise.When the working area reaches about 450 hectares,the collect rate of the unmodified spindle and the modified spindle reaches the maximum,which is about 96.4%and 96.7%respectively.When the working area reaches 600 hectares,the collect rate of the modified spindle is 0.5%higher than that of the unmodified spindle.From the perspective of collect rate,the passivation spindle has more excellent picking performance.(4)Experimental study on the effect of hook tooth modification on the wear resistance of spindle.In order to explore the effect of hook tooth modification on wear resistance,the samples of two kinds of spindles were obtained under different working areas,and the samples were cut and prepared,the surface micro-morphology of the spindle hook teeth were characterized,the wear area and coating thickness were extracted.The results show that the front tooth tip of the unmodified spindle hook teeth is easy to break,and the peeling of the hook tooth coating is earlier than that of the modified spindle.Under the same working area,the wear area of the modified spindle hook teeth is smaller,and the coating thickness at the test position is higher;when the working area reaches 600 hm~2,the wear area of the unmodified spindle no.1 hook teeth reaches 9×10~5μm~2,which is about 2.3 times that of the modified spindle no.1 hook teeth,and the coating of no.1,no.2 hook teeth of the unmodified spindle and no.1 hook teeth of the modified spindle is peeled off.Compared with the wear morphology,wear area and coating thickness,the passivation ingot has better wear resistance. |
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