WEB Mechanical in-situ CT studies combined with digital volume correlation on lattice structures manufactured by selective laser melting
Additive manufacturing is a recent trend in many fields of engineering. One of the greatest advantages of additive manufacturing is that the structure can be highly adapted to the load case that is relevant for the application. Lattice structures support this trend: There are optimized geometries for pressure, tension, shear, torsion, and combinations of these load cases. On a larger scale, the lattice structures can also be designed to be graded to increase the local volume fraction or cell size of the material and with it its strength and stiffness.
In the present contribution, a lattice structure was manufactured additively and tested using a micro computed tomography (CT) in-situ stage. Tensile tests were conducted in order to evaluate the local and global stiffness. Digital volume correlation (DVC) was utilized to match CT images from different load steps and to calculate the geometrical transformation from one load step to the other. This geometrical transformation was then used to evaluate the predominant strain tensor on different scales of the structure. The local strain was mapped on a finite element (FE) mesh in order to validate the results of FE simulations in a latter step.
Our study shows that the strain tensor can be derived from DVC tests and used to calculate the local stiffness of the structure. The stiffness is compared with an analytical solution for the structure at hand for validation. Moreover, DVC proves to be superior in detecting damage, such as. cracks and other singularities that appear during testing.