The shear behavior of rock joints is important in solving practical problems of rock mechanics. Three group rock joints with different morphologies are made by cement mortar material and a series of CNL(constant norma...The shear behavior of rock joints is important in solving practical problems of rock mechanics. Three group rock joints with different morphologies are made by cement mortar material and a series of CNL(constant normal loading) shear tests are performed. The influences of the applied normal stress and joint morphology to its shear strength are analyzed. According to the experimental results, the peak dilatancy angle of rock joint decreases with increasing normal stress, but increases with increasing roughness. The shear strength increases with the increasing normal stress and the roughness of rock joint. It is observed that the modes of failure of asperities are tensile, pure shear, or a combination of both. It is suggested that the three-dimensional roughness parameters and the tensile strength are the appropriate parameter for describing the shear strength criterion. A new peak shear criterion is proposed which can be used to predict peak shear strength of rock joints. All the used parameters can be easily obtained by performing tests.展开更多
In the case of braking,a diversity of friction mechanisms occurs at the interface,caused by the heterogeneity of the composition,properties,and thermal phenomena.After friction,the obtained surfaces of the brake linin...In the case of braking,a diversity of friction mechanisms occurs at the interface,caused by the heterogeneity of the composition,properties,and thermal phenomena.After friction,the obtained surfaces of the brake lining materials are highly heterogeneous.Load-bearing plates which are also called contact plateaus are formed with a compacted third body and constitute the sites of energy dissipation and sliding velocity accommodation.Their arrangement and preferential localizations in the contact constitute a key factor for the understanding of frictioninduced phenomena and braking performance.Within this framework,a morphological characterization method has been set up based on several measurement techniques to explore the macroscopic and microscopic contact situation of the pad-disc system.The results show that exploiting Abbott curve parameters combined with roughness parameters is an effective way to give a detailed and comprehensive morphological description of the brake pad friction surface.It can be seen that the contact plateaus have preferential locations which give a particular load-bearing arrangement in the pad-disc interface which can be explained by friction and wear mechanisms.Results reveal also the main encountered difficulties,especially regarding the significance of scales and parameters describing the morphology of the friction material surface and the load-bearing plates disposition.展开更多
基金Project(41130742)supported by the Key Program of National Natural Science Foundation of ChinaProject(2014CB046904)supportedby the National Basic Research Program of China+1 种基金Project(2011CDA119)supported by Natural Science Foundation of Hubei Province,ChinaProject(40972178)supported by the General Program of National Natural Science Foundation of China
文摘The shear behavior of rock joints is important in solving practical problems of rock mechanics. Three group rock joints with different morphologies are made by cement mortar material and a series of CNL(constant normal loading) shear tests are performed. The influences of the applied normal stress and joint morphology to its shear strength are analyzed. According to the experimental results, the peak dilatancy angle of rock joint decreases with increasing normal stress, but increases with increasing roughness. The shear strength increases with the increasing normal stress and the roughness of rock joint. It is observed that the modes of failure of asperities are tensile, pure shear, or a combination of both. It is suggested that the three-dimensional roughness parameters and the tensile strength are the appropriate parameter for describing the shear strength criterion. A new peak shear criterion is proposed which can be used to predict peak shear strength of rock joints. All the used parameters can be easily obtained by performing tests.
文摘In the case of braking,a diversity of friction mechanisms occurs at the interface,caused by the heterogeneity of the composition,properties,and thermal phenomena.After friction,the obtained surfaces of the brake lining materials are highly heterogeneous.Load-bearing plates which are also called contact plateaus are formed with a compacted third body and constitute the sites of energy dissipation and sliding velocity accommodation.Their arrangement and preferential localizations in the contact constitute a key factor for the understanding of frictioninduced phenomena and braking performance.Within this framework,a morphological characterization method has been set up based on several measurement techniques to explore the macroscopic and microscopic contact situation of the pad-disc system.The results show that exploiting Abbott curve parameters combined with roughness parameters is an effective way to give a detailed and comprehensive morphological description of the brake pad friction surface.It can be seen that the contact plateaus have preferential locations which give a particular load-bearing arrangement in the pad-disc interface which can be explained by friction and wear mechanisms.Results reveal also the main encountered difficulties,especially regarding the significance of scales and parameters describing the morphology of the friction material surface and the load-bearing plates disposition.
