Papers by Author: An Min Tang

Abstract: The experimental procedures of mixed mode fracture of several ductile materials are investigated. The position and direction of crack initiation are determined according to a new method. The variations of fracture caused by different physical mechanisms are analyzed. Through studying the changing regularity of different fracture mechanisms, it is believed that the main ways of the fracture in ductile materials can be divided into three groups. They are traction fracture and two different types of shear fracture. Void nucleation, expansion and coalescing are the dominant mechanism of traction fracture. The formation and development of localized shear bands are the dominant mechanism of the two different types of shear fracture. Localized large plastic deformation will cause damage within the material. The fundamental factor, which causes the occurrence of fracture in the material, is a certain stress parameter at the dangerous point has reached the critical fracture value of the material. Based on those phenomena listed above, several fracture controlling parameters for different fracture forms have been discussed, and several new parameters, which affect various fracture forms, have been proposed.

Abstract: Based on fundamental ideas in tribology and basic concept of stress state in solid mechanics, the existence of frictional force on shear plane is discussed under uniaxial compression of brittle materials. On account of macroscopic fracture forms and mesoscopic fracture mechanisms, the key factors influencing shear fracture angle are analyzed. The results show that, when brittle materials are compressed and shear fracture occurs, shear fracture surface at the crack initiation point is consistent with the maximum shear stress. But the reason of shear fracture angle examined in experiment greater than 45º lies in that, the existence of frictional force between endface of specimen and pressure head of testing machine, and additional tensile stress produced in the materials when harder crystalline grain wedge in softer medium have changed original uniaxial compression stress state and the direction of maximum shear stress on next fracture path.

Abstract: During the process of elastic deformation, based on first law of thermodynamics, deformation energy value equals to the work done by external forces moving through elastic deformation, which can determine the amount of elastic deformation. According to second law of thermodynamics, the true deformation energy value should be the minimum of all possible deformations, which can determine the distribution rule of elastic deformation. From this, it can be realized that there are some problems existed in the derived process of the minimum potential energy principle. The total potential energy of system remains constant in all of possible elastic deformation. Applying the two characteristics of elastic deformation, a few application problems could be solved expediently.