Investigations Of The Construction Of Potato-Screen Model Under Dropping And Its Kinematic Response Characteristics

To establish the potato-screen model for the potato under drop impact and analyze its kinematic response characteristics,with the aim of enriching the theory of potato model construction and providing a reference for optimizing the structural parameters of the separating screen design.This thesis employs a combination of theoretical analysis,laboratory test and field test to investigate the visco-elastic-plastic mechanical model of the potato,the vibration mechanical model of the separating screen,and the kinematic relationship between the potato and separating screen.The main contents are as follows:1.By incorporating the Hysteretic Spring contact model theory,a viscoelastic-plastic mechanical model for potatoes was established and analyzed to establish the correlation between model parameters and potato collision deformation.High-speed cameras were utilized to record the drop image of potatoes under different experimental factors such as drop height,potato quality,drop direction,and potato variety and the curve of the collision deformation of potato and separation sieve with time was obtained.Based on the curve of potato collision deformation over time,the parameters of the potato visco-elastic-plastic model were obtained.The potato drop test was carried out using potato damage volume and plasticity ratioλ_pas test indices,to explore the relationship between different factors and potato damage volume and plasticity ratioλ_p.The results indicated that the potato damage volume and plasticity ratioλ_pincreased with the increase in drop height.When the potato falls along the length direction,the damage volume and plasticity ratioλ_pare the largest.Additionally,the greater the hardness of the potato variety,the smaller the damage volume and the greater the plasticity ratioλ_p.2.By incorporating the theory of mechanical vibration,a vibration mechanics model for the separating screen was established,and the correlation between the vibration displacement of the separating screen and the model parameters was deduced.The vibration test system was used to collect the vibration acceleration of the separating screen under various experimental factors such as drop height,potato mass,drop direction,and potato variety.Subsequently,the vibration displacement-time curve of the separating screen was obtained,and the vibration mechanical model parameters of the separating screen were derived accordingly.Based on these findings,the relationship between different experimental factors and attenuation coefficientαwas further explored.The results indicated that the attenuation coefficientαincreased with the increase in drop height and potato quality.When the potato falls along the width direction,the attenuation coefficientαis the smallest.Additionally,the attenuation coefficientαincreased with the increase in potato hardness.3.Using the potato drop image and separating screen vibration signal acquisition system,data on potato deformation,potato impact acceleration,separating screen vibration displacement,and acceleration were collected.Subsequently,the potato-separating screen peak difference and acceleration peak difference were calculated,and the correlation between the displacement peak difference,acceleration peak difference,and test factor levels was established.The results showed that the displacement peak difference increases with the increase in drop height and potato mass,whereas the acceleration peak difference increases with the increase in drop height but decreases with the increase in potato mass.4.Through field experiments,the correlation between the crank speed,forward speed of the machine,and the peak acceleration difference was examined,and the relationship between the performance index of the separating screen and the peak vibration acceleration of the separating screen,peak impact acceleration of the potato,and the peak acceleration difference was determined.The results indicate that the peak acceleration difference increases first and then decreases with an increase in the crank speed.Furthermore,the peak acceleration difference gradually decreases with an increase in the forward speed of the machine.The greater the crank speed,the greater the obvious rate,and the obvious rate is related to the vibration acceleration peak of the separation sieve.The greater the forward speed,the greater the skin breaking rate,and the skin breaking rate is related to the peak acceleration and the peak acceleration difference of the potato.