Abstract: In the modern design theory on the hydraulic press, reloaded composite frame becomes preferred structure of hydraulic press. The pre-tension force directly affects the stability of the structure of whole press. Through the analysis of the pre-stressed frame’s working process with and without deformation of beam by using the mechanical analysis and numerical simulation, vertical post and tension rod deformation calculation formulas are derived; At the same time, the theory formula of frame residual pre-tightening force after loading is given, and be compared with finite element calculation results. In order to reflect the tension rod preload degree effect on the vertical post’s residual stress, residual pre-tightening coefficient definition and calculation formula are given, and its scope is also given. New method for the force parameters of pre-stressed structure is provided.

Key words: finite element, hydraulic press, pre-stress, pre-tension force, residual preload