Vibration Simulation Analysis And Experimental Research On Arm System Of Hand-held Rice Transplanter

Hand-transmitted vibration is one of the important factors that endanger the physical and mental health of vibrating implements.In particular,the operators of agricultural machinery and equipment are exposed to severe vibrations with long exposure time,thus the problem of hand-transmitted vibration is particularly prominent.If operators are exposed to hand-transmitted vibration for a long time,it will not only affect the blood circulation of the distal part of the hand,but also cause damage to the joints,muscles and connective tissues of the upper limbs of the human body.In severe cases,it may cause arm vibration disease.Therefore,it is necessary to effectively control the hand-transmitted vibration of the implement to minimize the adverse effects of vibration on human health and the arm system.This research focuses on the National Natural Science Foundation project"Study on the Biomechanical Model and Dynamic Response Characteristics of Arm Vibration of Agricultural Machinery Equipment Operators".Based on the biomechanical properties of arm,the hand-transmitted vibration evaluation system and the vibration dynamics theory,the existing hand-transmitted vibration evaluation systems are integrated to evaluate the hand-transmitted vibration exposure of the machine and analysis the vibration response and transmission characteristics of human arm.The relevant research results can provide a certain reference for the operator's arm vibration protection.Then,based on the CT scan image of the human arm,the biomechanical and finite element analysis models of the human arm were constructed by combining Mimics,Geomagic Studio,Creo,Hypermesh and Abaqus software.On basis of it,the finite element modal analysis of the human hand and the whole arm was performed separately,and the natural vibration characteristics of the arm were calculated.Finally,the dynamic simulation of the vibration transmission process of the human arm is carried out when grasping the handle.Specifically,by analyzing the steady-state dynamics of the arm,the vibration response and transmission characteristics of each measuring point of the arm are calculated and analyzed.The simulation analysis results are compared with the results of the preliminary test and the modal analysis.The results show that the simulation analysis is basically consistent with the vibration test and the modal analysis results.The main research contents and conclusions are as follows:(1)The hand-transmitted vibration and arm vibration transmission characteristics of the hand-held transplanter handle were analyzed and evaluated.According to the evaluation standard of ISO 5349-1:2001,the hand-transmitted vibration of the transplanter handle was tested and evaluated.The results showed that the 8 h vibration exposure of the transplanter's arm was 2.442 m/s~2,which was slightly lower than the 2.5m/s~2 value specified by the EU Directive.Although the risk of hand-borne vibration sickness is relatively low in this case,considering that the hand-held transplanting machine does not operate at full speed,the person who operates the rice transplanter all the year round should still pay attention to the arm vibration disease.In addition,the vibration response test was carried out on the handle of the transplanter as well as the different positions of the human arm.It was found that the vibration acceleration of each axial direction of the transplanting machine in the idle state and the working condition is significantly lower than that of the other two measuring points of the back of the hand and the lower arm since most vibration energy was absorbed before transmiting to the shoulder joint.An attenuating trend is presented during the transmission of vibration from the handle of the rice transplanter to the arm.Resonance occurs near 25 Hz when vibration is transmitted from the handle to the arm test point.In the x and y directions,the palm has a poor absorption of low-frequency vibration energy of less than 25 Hz,and in the z-direction,it has poor absorption of vibration energy for the intermediate frequency component of about 100 Hz.The most sensitive vibration frequency range of the human hand is 8-16 Hz,which belongs to the low frequency range.Therefore,low frequency vibrations of less than 25 Hz,especially 8-16 Hz,should be the focus of future research.Vibration reduction gloves can be used during actual operation to reduce vibration below80 Hz.In addition,the wrist absorbs most of the vibration energy.In order to avoid hand-transmitted vibration diseases and joint damage,the vibration-damping measures for the wrist are also important.For example,a wristband can be worn when using a hand-held agricultural implement.(2)Innovatively,a biomechanical and finite element analysis model of the human arm was established.Based on the CT scan image of Chinese adult male arm,the biomechanical finite element model of human arm including soft tissue,bone and joint ligament was innovatively established by combining Mimics,Geomagic Studio,Creo,Hypermesh and Abaqus software.The model defines bone as a linear elastic material,while soft tissues such as skin and subcutaneous tissue are defined as superelastic and viscoelastic materials.According to the anatomical structure of the arm,the bones and soft tissues are meshed by means of a common node.To solve the problem of excessive distortion of the unit caused by the large displacement of the unit in the bending of the finger,the mesh at the joint of the opponent is encrypted and refined during the modeling process.In addition,the model uses a hinged connection and a linear spring to simulate the knuckles and joint ligaments.(3)The simulation analysis of the natural vibration characteristics,vibration response and transmission characteristics of the human arm system was carried out.In this study,the finite element modal analysis of the human hand and the arm was performed by the block Lanczos method,and the first 6 vibration modes are extracted respectively.Observing the various modes of the arm,the vibration displacement of the finger is the largest,especially the vibration amplitude of the finger is the largest in the first-order natural frequency,which indicates that the vibration load is most likely to accumulate at the finger during the hand-transmitted vibration.This consequence is in good agreement with the experimental research and the results provided by the literature.It is reasonable to assume that the model is accurate and reliable.In the study,the dynamics simulation of the vibration process of the human arm during the gripping of the handle is conducted.Through the steady-state dynamic analysis of the arm,the vibration response and transmission characteristics of each measuring point of the arm are calculated and analyzed.It is prone to resonance when contacting with vibrations in the range of 5-10 Hz and 35-40 Hz,which causes fatigue damage to joints and soft tissues.Therefore,people should try to avoid contacting directly with vibrations of 5-10 Hz and35-40 Hz when holding the vibration handle.