Quantization Of Cracking Characteristics Of Asphalt Concrete Based On DIC Technology

Cracks in asphalt concrete pavement will cause the asphalt pavement to be affected by more external conditions such as rain erosion and solar radiation.Chinese current asphalt pavement design specification uses the low temperature cracking index as the asphalt pavement design index.This index does not clearly give the quantitative index of asphalt pavement cracks.The fracture mechanics R-curve method is an important method to study material cracking at the present stage,and it has good applicability in fracture analysis in many material fields.The construction of the R-curve requires quantification of crack propagation.This study used digital image technology(DIC)to measure the displacement of asphalt concrete during crack propagation.Compared with displacement sensors,DIC technology has the advantages of non-contact,full-field and post-processing capabilities.Therefore,the DIC full-field displacement measurement technology can accurately capture the fracture process of crack tip of asphalt concrete.The concept of the opening displacement matrix is proposed,and the displacement analysis is performed based on the opening displacement matrix and the R-curve is constructed.This article has the following three main research contents:(1)The SC(B)test was used to study the cracking characteristics of asphalt concrete,and the influence of test variables such as asphalt classification,test temperature,loading rate and aggregate size on the cracking characteristics of asphalt concrete was analyzed.(2)Using DIC technology to measure the displacement of the test piece,compare the data obtained by the technology with the displacement sensor data,verify the accuracy and precision of the digital image technology and the feasibility of the semi-circular bending test piece.The image post-processing stage performs displacement analysis on the selected points and performs analysis of variance.(3)Based on DIC technology,the concept of open displacement matrix is proposed,and the crack quantitative index is selected,and the R-curve of asphalt concrete is constructed accordingly.The application of R-curve deepens the study of cracking characteristics of asphalt concrete.After research,the following three main conclusions were drawn:(1)It is more feasible to study the cracking characteristics of asphalt concrete by semi-circular bending test.The classification of asphalt,test temperature,loading rate and aggregate size affect the deformation of the cohesive zone of asphalt concrete.The deformation of the cohesive zone at the tip of the crack complicates the cracking characteristics of asphalt concrete.(2)The cohesive zone deformation is closely related to the crack,and the crack initiation is the result of the deformation accumulation in the cohesive zone.By taking the point displacement curve analysis,it can be roughly obtained that the lateral dimension of the cohesive force region is in the range of ODM(5,0).Since the position of the cohesive force zone moves as the crack expands,the longitudinal dimension is for further study.(3)The test variables have a greater influence on the R-curve,and the fracture energy rate is more reflective of the influence of the test variables on the cracking of asphalt concrete than the fracture energy.By analyzing the variance of each index in this paper,ODM(5,0)can reflect the influence of test parameters on the cracking characteristics of asphalt concrete more than CTOD.