Study On Dynamic Analysis And Design Of Compacting System Of Asphalt Paver

The development of our country’s highway places higher demand on performance ofasphalt paver. Performance of paver’s screed directly determines the paving quality, whichis one of the important factors affecting pavement quality. Most of pavers used inconstruction posses double tampers and single vibrator, which have advantage of highdensity and planeness and would reduce compaction times. Because of the complexity ofscreed’s structure, the inertial force arose from operation of tampers causes adverse effectson screed box. The resultant moment of force of the inertial force and vibration force ofvibrators result in fluctuating of the working elevation of screed, which reduce theplaneness of pavement. As the paving width of paver increasing, the difference of dynamicresponse along the length direction of screed becomes notable, which will affect the flatness of thepaving layer.Although the issue about dynamic behavior of screed has been addressed in somerecent researches, there still lack of full study on this problem because screed is treated as asingle degree of freedom rigid body in those literatures, without considering the elasticdeformation of screed itself and its coupling with vibration. These lead to the results farbeyond the truth. In addition, uneven of dynamic responses caused by some parameters isnot considered during the design phase. In conclusion, it has theory significance andengineering application value to develop the dynamic behavior and dynamic designresearches on screed.Screed of the paver which is mechanically widened and the paving width is has9meters is studied in this dissertation. The theoretical study and numerical simulationcombined with experimental research methods are applied to get characteristics of dynamicresponse of screed, and the dynamic optimal design method is used to improve operationperformance of paver.The screed box is taken as rigid body with two DOFs (degrees of freedom), and multiDOF dynamic model for double tamper-single screed system of asphalt paver is established.Influence of movement of tamper mechanism on vibration response of screed box is studied. Variation of amplitude of response due to different phase relations between each tampers isanalyzed to determine the appropriate phase angle; Relationship between the position ofvibrator and uniformity of longitudinal vibration response of screed is simulated to obtainthe best installation location of the vibrator. Characteristics of the vibration response underthe condition that stiffness coefficient of paving material becomes larger is simulated.The screed is thought as flexible body, while tampers are taken as rigid body, coupledrigid and flexible model for compacting system of paver is established. Finite elementmethod is used to make the screed be discrete, governing equations are derived based onLagrange’s equations. Distribution of amplitude of dynamic response on screed along thedirection of paving width is simulated numerically, and the affect of such parameters asfrequency of movement of vibrator and tampers, mass and stiffness and moment of inertiaof screed, phase angle between tampers, phase difference between vibrator’s eccentricshafts on degree of non-uniformity of response of screed is analyzed. The comparisonbetween test and simulation shows that the dynamics model presented in this dissertation iscorrect and feasible. The results provide reference for dynamic modification of screed toimprove lateral vibration uniformity.Based on the above work, the optimization parameters are selected through thesensitivity analysis of dynamic response of key points on screed to design parameters.Functional expression about optimization parameters and difference between the amplitudeand mean of amplitude in screed are built through response surface method based onorthogonal design and numerical calculation. The design parameters are optimized based onmean amplitude constraint with target of minimal difference between the amplitude inscreed. The optimal results show that the uniformity of amplitude improved effectively anddifference between the amplitude in screed decreased greatly.An experiment research on paver prototype is carried out, effect of phase angle oftampers on the uniformity and amplitude of vibration response of screed and influence oflocation of vibritor on longitudinal niformity of vibration response of screed and responseof screed distribution characteristics in paving width are studied. The results verify thecorrectness of the theoretical research and numerical simulation.