Research On Multi-precision Numerical Modeling Method Of Aggregate Based On Real Shape In Asphalt Mixture

With the development of computer graphics and image technology,mesomechanics numerical simulation technology,as an analysis technology based on the mesomechanics structure of asphalt mixture,has effectively improved the prediction accuracy of pavement performance of asphalt mixture and obtained extensive applications.The numerical model of mixtures is the basis and premise for reliable simulation.Aggregate takes the largest proportion in the material composition of mixtures,and its numerical representation has a very important influence on the accuracy and scale of the simulation.Based on the X-ray CT sectional scanning image of aggregate,this paper reconstructs the three-dimensional solid modles of aggregates by computer graphics image technology.Based on this,an adaptive numerical modeling algorithm for aggregate was developed to realize the automatic parameterization construction of three-dimensional discrete element and finite element numerical model.The main contents are as follows:(1)The two-dimensional pixel of aggregate in the X-ray CT image was detected to construct the aggregate contour wireframe model and determine the mapping relationship between the aggregate and its contour in each layer.The three-dimensional solid models of aggregate was constructed by ACIS,which is the three-dimensional modeling engine.(2)A sphere generation algorithm for fitting the aggregate surface was developed.The spherical element was used to fit the three-dimensional surface of the aggregate solid model under the precision control,and the internal space of the model was enriched to obtain the aggregate shape fitted by the spherical element.The quality attribute calibration algorithm is developed,and the fitting result is calibrated with the mass attribute of the aggregate to obtain the aggregate three-dimensional discrete element model.(3)By means of the triangular patch discrete algorithm of the aggregate surface,the three-dimensional surface of the aggregate solid model is discretized into triangular patches under the controllable surface deviation.The tetrahedral unit splitting algorithm was developed based on element quality control.The formation,subdivision and optimization of tetrahedral elements are completed based on the triangular surface of the aggregate surface to obtain a three-dimensional finite element model of aggregate.The 3D reconstruction and numerical modeling experiments of a large number of real aggregates prove that the proposed discrete element adaptive modeling method can generate discrete element models under the premise of controlling the surface fitting accuracy.The volume of the discrete element model occupies more than 99% of the original aggregate volume.Compared with the existing discrete element modeling method,this method greatly reduces the number of elements of the model and can be imported into the mainstream discrete element simulation software PFC 3D;The finite element adaptive modeling method proposed in this paper can also generate high quality tetrahedral elements under the premise of controlling the fitting accuracy of the aggregate surface.Compared with the meshing module of the general finite element software,this method can greatly reduce the number of tetrahedral elements and can be imported into the finite element mainstream simulation software ANSYS.This method effectively improves the automation,reliability and efficiency of numerical modeling of the mixture.