Abstract:

The basic equations of elastic mechanics include not only the equilibrium differential equations，the geometric equations and the physical equations，but also the stress boundary conditions and the displacement boundary conditions. Various objects in different forces，different constraints boundary conditions are often different，because of practical problems in changing boundary conditions constitute a complex elasticity problem. It’s difficult to establish the stress boundary condition for beginners to solve the problem of elastic mechanics. Based on the induction of the existing knowledge，the main stress boundary conditions and the secondary stress boundary conditions are summarized respectively. The main method of the former is the comparison method and the formula method. The latter is the equivalent static method and the equilibrium condition method.

Key words: elastic mechanics, the stress boundary condition, saint venant principle, solving method