| Summary: | 碩士 === 淡江大學 === 土木工程學系 === 89 === The joint roughness is consisted of many components of asperities in different size. This roughness has predominant role in the shear behavior under lower stress levels. Usually, the secondary asperity controls the shear behavior at lower stress conditions and the primary asperity dominate at the higher stress conditions. This research employs the Fourier series concept to resolve the joint profile into several harmonics. Then, superimposing the first five and forty harmonics generates two synthetic joint surfaces in 2D and 3D models by superimposing the first five and forty harmonics. One aims to model a profile with the primary asperity. The other is for a profile with the primary and secondary asperity. The purpose is to investigate the relationship of the joint shear behavior and real contact areas, and thus the key factors of wear between joint surfaces. A CCD photo of the shearing area after shearing is taken for analysis.
The main conclusions are drawn as follows. (1) The LOM (laminated object manufacturing) technique is well developed to generate the three-dimensional joint surface. (2) The shape, size and spatial distribution of wear areas primarily depended upon the shearing direction, initial roughness degree (roughness index, D) and stress levels ; (i) The asperity with higher asperity angle predominates the contact mechanism between joint surfaces. (ii) The orientation of wear area likely arranges parallel to the strike direction of joint asperity distribution. (iii) At moderate stress levels, the ratio of wear areas (as ) ranges from 4 to 13% .(3) At very low stress levels, the secondary asperity has a remarkable effect on the joint strength, but not on the dilation. The dilation behavior is mainly controlled by the large-scale primary asperity. (4) To represent the geometrical characteristic for a 3D joint surface by several 2D profiles, the profiles perpendicular to the foliation direction is favored.
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