Abstract
The pebble shape is a critical factor that affects the bearing characteristics of truck escape ramps. In this paper, a reconstruction method was proposed for randomly shaped pebbles used in truck escape ramps, and statistical analysis was conducted on the results of pebble compression tests. First, 100 pebble samples were randomly selected, and the pebble outlines were fitted in three views. The overlapping method was implemented to fill the three views with ball elements, and the ball elements were then extended into three-dimensions. The results demonstrated that the proposed method satisfactorily monitored the real pebble shapes. Second, statistical analyses were conducted on the parameters of the outlines, and corresponding data sets were built. The key parameters of the pebble DEM model, such as the friction coefficient, were calibrated based on the compression test results, and repeated simulation results verified the feasibility of the proposed pebble DEM model. Next, statistical analysis was conducted on the probability distribution of the contact forces. Third, simulations were conducted with different pressing plate velocities and pebble shapes. The results indicated that the pressing plate velocities had minor effects on the contact forces. As the pressing plate velocity increased, the slope of the contact forces correspondingly increased. The particle shape was a critical factor affecting the simulation results. With the same contact parameters, the simulation results of different pebble shapes varied greatly, which further indicated the importance of the proposed pebble shape reconstruction method. The proposed pebble DEM model could be further used in the design of truck escape ramps.
Highlights
Previous studies on truck escape ramps have mainly focused on the following aspects: (1) vehicle conditions, such as truck velocity and break-drum temperature predications [1]; (2) affiliated facilities, such as the approach length [2] and setting locations [3]; and (3) experimental arrester bed tests [4] and alternative arresting systems [5]
To reduce computing amount and maintain a good shape of the pebbles used in a truck escape ramp, this paper proposed a three-dimensional pebble shape reconstruction method based on the data measured from outlines of 100 pebble samples
The results indicate that the tests could be performed repeatedly, and the results of different testing coefficients are separated, which indicates that dynamic compression tests could be used as the pebble discrete element method (DEM) model calibration method
Summary
Previous studies on truck escape ramps have mainly focused on the following aspects: (1) vehicle conditions, such as truck velocity and break-drum temperature predications [1]; (2) affiliated facilities, such as the approach length [2] and setting locations [3]; and (3) experimental arrester bed tests [4] and alternative arresting systems [5]. The DEM basic element shape construction method could reduce the computational amount and maintain good calculation accuracy. Zhou et al [28] simulated randomly shaped coal particles based on STL files obtained with a scanner The advantages of this method lie in the particle shape accuracy, and the coordinates of the ball elements were comparatively easy to calculate. Liu et al [15] proposed a pebble shape construction method for irregularly shaped pebbles and selected compression tests to calibrate the pebble DEM model parameters. The construction method for randomly shaped pebbles and the corresponding pebble DEM model contact algorithm are not well recorded. Where α is the damping coefficient, and vi is the generalized velocity
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