The concept of virtual material was developed for the first time when the flexible joint interface may be considered as a virtual material with the same cross area. The virtual material is rigidly connected with two components situated in both sides of flexible joint interface. By adding an element, a complex assembled part including a joint interface could be equaled as a simple component without any joint interface in order to simplify the complicated problem about flexible joint interface. The interaction between normal and tangential characteristics of fixed interface taken into account, a series of exact analytical solutions of elastic modulus, shear modulus, Poisson ratio and density were deduced from virtual material through Hertz contact theory and fractal theory. By using experimental results about a series of test specimens, the exact analytic expressions for virtual material’s parameters were verified in terms of qualitative comparison principle of resembling vibration shapes and quantitative comparison principle of the natural frequencies. The virtual material model vibration shapes are in excellent agreement with the experimental results. The relative errors between the virtual material model natural frequencies and the experimental ones are between -3% and 10%.