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Open die hot forging has a wide industrial application on deforming ingot into billet with desired dimension and qualified internal microstructure. An example open die forging process of Ti-6Al-4V ingot is selected herein. A 3D FE-based numerical method was used to investigate the open die forging process with respect to the real working conditions. The simulation results were validated by the collected experimental process parameters from the forging system. Moreover, design of experiment method is adopted regarding the variation of process parameters to reveal the effects of critical factors on product deformation and quality characteristics. Results show that the process parameters including press speed, feed and reduction has significant effect on the workpiece deformation and effective strain which represents the forged billet formability and quality. Improved process parameters method is suggested with respect to the experienced benchmark based on the sensitivity analysis. Keywords: Open die forging; Ti-6Al-4V alloy; Sensitivity analysis; Process parameter; Numerical simulation

This paper presents an analytical study on the stress concentration problem due to a cuboid hole in structures. Base on the theory of elasticity and the finite element method, the governing equation with cyclic periodicities in three directions is established. By using the U-transformation technique, the nodal displacement solutions are given out in analytical form. Once the nodal displacements of the cuboid hole are derived, it is easy to discus the stress distribution around the hole. As an example, the paper discusses the problem that a cube hole in structure which is under x-direction tension loading, and obtains the stress concentration factor is 1.90. The research process can be extended to study the stress concentration problems under other loading conditions