Parameter Analysis And Optimization Design Of An Eccentric Retractable Finger Type Conveyor

Eccentric retractable finger type conveyor is an important part of the 4FZ-2000A self-propelled straw bundling machine.To prevent the straw in the straw box from being brought back to affect the subsequent tasks,this kind of conveyor could be used to transport the straw on the chain-and-slat type conveyor to the feed box.At present,scholars at home and abroad had applied more research on the use of eccentric retractable finger type mechanism for picking of mulching plastic film and caragana korshinskii.And the design was mainly based on retractable finger type mechanism of the screw conveyor on the header of the combine harvester.However,there were no clear design theory and method for the application of straw transport.(1)The main problems existing are as follows:The retractable finger have a greater impact on crops and forage,which could cause serious damage on crops and forage with seeds.(2)It was no clear of matching the working parameters and structural parameters to achieve more convenient transportation.(3)The main parts were subjected to large loads and the reliability was unknown.For the above problems,in order to study design theory of eccentric retractable finger type conveyor,theoretical analysis and kinematics simulation are carried out.The transport performance was optimized in order to find the optimum matching relationship between the structural parameters and the operating parameters.And the fatigue life of key component was predicted.(1)The retractable finger rotary center was determined in the fourth to meet the conveying requirements by using the theoretical analysis of the transport working.The equation of the intersection area between the end of the retractable finger and the longitudinal section of moving material is established,and an equation for the transport capacity in a single transport cycle was established based on it.The motion equation of the end of retractable finger was established.The dynamic equation of retractable finger was established,and the retractable finger was the key component to bear the heavy load.(2)The transport performance evaluation index of eccentric retractable finger conveyor was defined through analysis.And the working parameters and structural parameters affecting the transport performance were determined as:roller speed,the mounting height of the roller,material thickness,the length of retractable finger,roller radius,eccentricity of rotary center of retractable fingers,and the angle between two rotary centers'connection and plumb direction etc.(3)The structure was designed and optimized by using the virtual prototype technology which took the structural parameters and operating parameters of affecting transport performance as design variables,and both the maximum transport capacity in a single transport cycle and the least of maximum acceleration at end of retractable finger as the objective.Firstly,the single-objective optimization was carried out.Then,a weighted combination method was used to build a multiple-objective function,and multiple-objective optimization design was performed based on it.The results showed that another objective didn't met the conveying requirements although the single-objective optimization results was significant.The transport capacity increased from 0.58 kg to 0.79 kg after multiple-objective optimization,which was 36.2%higher than its initial value.And the acceleration reduced from 40.59m/s~2 to 8.18m/s~2 after multiple-objective optimization,which was 5.9%lower than its initial value.So the transport performance had achieved a comprehensive optimization effect.(4)Modal and resonance analysis of retractable finger after the conveying performance had been optimized showed that the external excitation frequency was much smaller than the natural frequency of the retractable finger,and no resonance would occur.The statics analysis of the retractable finger showed that it met the requirements of static strength in operating limits,and the main failure mode was multi-axial fatigue in high cycle fatigue.(5)The S-N curve of the retractable finger was obtained by surface modification and stress gradient correction using nCode.The stress combination method of Critical Plane was used.The fatigue life of retractable finger corrected by Goodman and improved Gerber mean stress correction method was calculated by using Linear Miner Damage Rule when the survival rate was 50%,90%and 99%,respectively.The calculation results showed that when the survival rate is 90%,the fatigue life of the retractable finger corrected by the improved Gerber average stress correction method was consistent with actual design life,which proved that the numerical prediction method and the results were reliability.The retractable finger had enough anti-fatigue performance and could work normally and safely during the design life.