| Long-term,extensive exposure to hand-transmitted vibration can lead to damage or disorders of the blood vessels,nerves,muscles and skeletal joints of the hand-arm system,and these symptoms are collectively referred to as hand-arm vibration disease.Currently,hand-arm vibration disease has become a common occupational disease and a legal occupational disease in China,but its causative mechanism is not yet clear,and treatment and recovery are extremely difficult.How to prevent hand-arm vibration disease has become a hot topic at home and abroad,and the study of hand-arm system biodynamics is an important basis for hand-transmitted vibration exposure measurement,evaluation and risk assessment,therefore,this paper focuses on the vibration transmission characteristics of the hand-arm system and its modeling.In this paper,the vibration response of four different segments(wrist,two elbow ends and upper arm)of the hand arm system of 200 volunteers was tested under different grip force,thrust force and hand arm postures based on ISO 10819.Based on this,the effects of different factors on the hand-transmitted vibration transmission characteristics was investigated using statistical analysis and functional data analysis methods,and a multi-degree-of-freedom discrete dynamics model was established to describe the hand-transmitted vibration transmission characteristics.Finally,the hand-transmitted vibration characteristics under typical power tool excitation are studied for specific working conditions.The main results of this research paper are as follows.1.Based on a large sample space,the hand arm system was tested,analyzed and studied the vibration transmission characteristics of four different segments under different grip force,thrust force and hand arm posture.2.The effects of grip force,thrust force and hand arm posture on the vibration transmission characteristics of the four different segments of the hand arm system were analyzed by applying statistical analysis methods,and the results showed that most of the main and interaction effects of grip force,thrust force and hand arm posture on the vibration transmissibility of the four different segments of the hand arm system at the frequencies analyzed were significant,except for those within 10Hz.3.Based on the larger sample space,the effects of anthropometric factors on the resonance peak and resonance frequency of vibration transmissibility were analyzed using multiple stepwise regression analysis.The results showed that:weight and hand circumference had significant effects on resonance peak(P<0.05),and weight was negatively correlated with resonance peak,and hand circumference was positively correlated with resonance peak,but the effects of anthropometric factors on resonance frequency were not significant(P>0.05).4.Based on the large sample space,the effects of grip force,thrust force,anthropometric factors and gender on the vibration transmissibility of the wrist segment and elbow segment of the hand arm system were analyzed using a functional data analysis method,and the results showed that there were significant effects of weight,gender,grip force,and thrust force on the vibration transmissibility of the wrist segment and elbow segment in some frequency ranges.The frequency ranges of weight and gender were related to different hand arm postures and measurement positions,such as in the posture of arm elbow bending at 90°,the frequency ranges of weight on the vibration transmissibility of the upper arm elbow were 9-13 Hz and 16-255 Hz,where 9-13 Hz was positively correlated and 16-255 Hz was negatively correlated.In the posture of arm elbow bending at 90°,the frequency range of the effect of grip force and thrust force on the vibration transmissibility of the upper arm elbow segment is mainly distributed in two frequency bands of 8-17 Hz and 39 Hz or more,where the frequency band of 8-17 Hz is negatively correlated with the vibration transmissibility and the one above 39 Hz is positively correlated.5.Based on the structural characteristics of the human arm system and anthropometric data,the established multi-degree-of-freedom dynamics model of the hand arm system can better describe the vibration transmission characteristics of different segments of the hand arm system,and the modal analysis yields a reasonable correspondence between the intrinsic frequencies from 10 Hz to 50 Hz and the resonant frequencies of four different segments of the hand arm system.6.For the specific power tools,vibration measurement and evaluation at the workplace were completed,and the results showed that the 8-hour equal energy frequency weighted acceleration of the tested lawn mower and hedge trimmer had exceeded the vibration limit of 3.5 m/s~2as specified in the national standard,and it was expected that more than 10%of the exposed population would develop vibration white finger after 1.8～8.5 years and 1.9～5.2 years,respectively.In order to effectively reduce or avoid hand-arm vibration disease among operators,the daily exposure time of the investigated operators using lawn mowers and hedge trimmers should be limited to 2.6 hours and 2.7 hours,respectively,and necessary protective measures should be took. |
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