Towards stiffness prediction of cellular structures made by electron beam melting (EBM)

Abstract

Additive manufacturing is a novel way of processing metallic cellular structures from a powder bed. However, differences in geometry have been observed between the CAD and the produced structures. Struts geometry has been analysed using X-ray microtomography. From the 3D images, a criterion of ‘mechanically efficient volume’ is defined for stiffness prediction. The variation of this criterion with process parameters, strut size and orientation has been studied. The effective stiffness of struts is computed by finite element analysis on the images obtained by X-ray tomography. Comparison between the predicted stiffness and the effective one tends to show that the efficient volume ratio leads to a slight underestimation of the stiffness. Finally, the effective stiffness is used at the scale of a unit cell. This can help define the build orientation and loading direction that lead to the highest stiffness.

Keywords:

• Electron beam melting
• Additive manufacturing
• X-ray tomography
• Stiffness
• Cellular structure
• Finite element method

Acknowledgements

The authors would like to thank Luc Salvo for his help in the X-ray tomography experiments at ESRF (ID15 and ID19 lines, Grenoble, France) and Jérome Adrien for his help in the X-ray tomography at INSA Lyon (Lyon, France). They also gratefully acknowledge the support of Grenoble Institute of Technology for its SEI funding.