The paper is aimed at studying the motion conditions of the vibratory compacting machine equipped with the crank excitation mechanism characterized by the changeable geometrical parameters. Unlike numerous scientific publications devoted to similar subject, the novelty of the present research consists in the improved design of the vibro-impact plate compactor and the developed mathematical model describing the motion conditions of the compactor’s oscillatory system. It is proposed to use the crank mechanism to excite the oscillations of the impact body acting upon the frame of the compacting plate at a certain angle to the surface being compacted. The main idea of this improvement is to provide the self-propelling locomotion conditions of the compactor and to reduce the pushing force that must be applied by the operator. The research results obtained by means of the numerical modeling in Mathematica software describe the dynamic behavior of the compactor’s oscillatory system under different geometrical parameters of the crank excitation mechanism (crank eccentricity, impact gap, etc.). The material of the paper can be of significant practical interest for the designers and engineers dealing with the development of new vibratory compactors and the improvement of compacting technologies.

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Kinematic and dynamic analysis of three-mass oscillatory system of vibro-impact plate compactor with crank excitation mechanism

Using an AMPT tester and based on laboratory tests, this paper performed a comparative study on the dynamic characteristics of different asphalt mixtures, analyzed the influence of different asphalt binders on the characteristic parameters of the dynamic modulus master curve and the phase angle master curve of asphalt mixture, and expounds the evaluation function of the phase angle master curve for mixture relaxation characteristics. The results show that the modulus master curve parameters of the asphalt mixture are closely related to voids in the mineral aggregate, mixture density, and asphalt content of the asphalt mixture. For the same kind of asphalt mixture, because the gradation of mineral aggregate is fixed and the volume parameters are almost the same, the ultimate modulus of the mixture at different temperatures is unique; when the temperature changes or the asphalt changes, the shape parameter β of the modulus master curve changes regularly, which brings different dynamic responses, and the lower β will show the characteristics of a higher modulus. Asphalt is the source of the viscoelasticity of the asphalt mixture. Although the influence of particle gradation of the mixture will bring about the change of modulus, the phase angle of the mixture depends on the viscoelastic properties of asphalt, and the initial phase angle in the main curve is positively correlated with asphalt penetration and negatively correlated with the softening point and viscosity, while the peak phase angle A is negatively correlated with penetration, and the softening point viscosity is positively correlated. The viscoelastic interval, represented by ω, is negatively correlated with penetration but positively correlated with the softening point and viscosity. The peak position, parameter ωc, of the phase angle master curve can evaluate the relaxation characteristics of the mixture, and the crack resistance of different mixtures can be compared without complex model calculation. In the comparison of the relaxation time of asphalt mixture, the relaxation time of foam cold-recycled mixture is the largest, which is significantly higher than that of other forms of cement mixture; the emulsified asphalt cold-recycled mixture is equivalent to AC20 and LSPM30 mixtures; the SBS-modified asphalt mixture has the best relaxation characteristics.

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Dynamic Characteristic Master Curve and Parameters of Different Asphalt Mixtures

The operating parameters of the asphalt-paver vibration-screed system (AP-VSS)
 including the excitation frequencies of the tampers and vibratory screed
 (ft
  and fs
 ) and the angular deviations of the tampers (α
 1 and α
 2) affect not only the pavement quality but also compaction
 efficiency. Based on the dynamic model of the AP-VSS and the interaction model
 of the tamper and hot-mixed asphalt, the experimental and numerical simulation
 studies of AP-VSS are performed to analyze in detail the influence of operating
 parameters of the AP-VSS on AP-VSS pavement quality and compaction efficiency.
 The maximum value of the root-mean-square acceleration
 (ar.m.s
 ) of the AP-VSS and the maximum value of the root-mean-square
 compaction force (Fr.m.s
 ) of the tampers are selected as the objective functions. The
 experimental and simulation results indicate that by using the AP-VSS design
 parameters, the pavement quality and compaction efficiency of the AP-VSS are
 quite low. To enhance the AP-VSS performance, the operation parameters are then
 optimized by the multi-objective optimization algorithm. The optimal result
 shows that the compression energy of the tampers and hot-mixed asphalt
 interaction is greatly increased by 36.2% in comparison without the
 optimization. Concurrently, both the values of ar.m.s
  and Fr.m.s
  are also increased and uniformly distributed over the length of the
 screed floor and surface of the hot-mixed asphalt in comparison without the
 optimization. Therefore, the pavement quality and compaction efficiency of the
 AP-VSS are remarkably improved.

Optimization of Operating Parameters of the Asphalt-Paver
 Vibration-Screed System in Improving Compaction Efficiency and Pavement Quality
 for Driving Vehicle Performance

Dynamic Behavior of a Vibratory Plate Compactor Working on a Horizontal Elastic-Viscous-Plastic Surface


 Asphalt mixture is composed of asphalt binder with aggregates of different sizes and compacted under static or dynamic forces. In practical engineering, compaction is a critical step in asphalt pavement construction to determine the quality and service life of pavement. Since the dynamic response characteristics of asphalt pavement can reflect the compaction state of asphalt mixture in the process of compaction, the establishment of the relationship between dynamic response characteristics and compaction degree is definitely significant. In this paper, a series of vibration sensors were adopted to capture the dynamic response signal of the vibration drum and asphalt mixture in the process of vibrating compaction for different surface courses of pavement. Then, the change regulations of vibration acceleration of vibrating drum and asphalt mixture were analyzed, and the quantitative linear relationship was established between accelerations of vibrating drum and asphalt pavement compactness. Further, the concept of evaluation unit (i.e., within 2 meters along the driving direction of the roller) and prediction method of compaction degree were proposed as well. The results showed that under the same vibration compaction condition, the compaction degree values of the top, middle and bottom layers have obvious differences, which should be taken seriously into consideration in the compaction process. Meanwhile, there is little difference which respectively are 2.8, 1.3 and 0.82% for the top, middle and bottom layers between the compaction degrees obtained by the proposed method and measured test. Therefore, the average value of the acceleration peak value of vibration drum within the evaluation unit can be adopted as the characterization index of the compaction degree of asphalt pavement. The investigation of this study can provide the technical reference for compaction control of asphalt pavement to a large extent.


Honghai Liu

Papers

Modeling of asphalt mixture-screed interaction: A nonlinear dynamic vibration model for improving paving density