An Attestation on Equality between a Fourth-order Variational Inequality of the Second Kind and Boundary Value Problem of Biharmonic Equation

A four-order variational inequality of the second kind, deduced from plate bending problems with friction term, is considered and the boundary value problem of biharmonic equation is discussed and their equality is proved. So the high-order partial differential equation can be solved by the corresponding variational inequality. Also these works provide more methods and the theoretical basis for solving biharmonic equation.