Jan T. Sehrt

Mechanical Properties of Laser Beam Melting Components Depending on Various Process Errors

Additive Manufacturing processes are constantly gaining more influence. The layer-wise creation of solid components by joining formless materials allows tool-free generation of parts with very complex geometries. Laser Beam Melting is one possible Additive Manufacturing process which allows the production of metal components with very good mechanical properties suitable for industrial applications. These are for example located in the field of medical technologies or aerospace. Despite this potential a breakthrough of the technology has not occurred yet. One of the main reasons for this issue is the lack of process stability and quality management. Due to the principle of this process, mechanical properties of the components are strongly depending on the process parameters being used for production. As a consequence incorrect parameters or process errors will influence part properties. For that reason possible process errors were identified and documented using high resolution imaging. In a next step tensile test specimens with pre-defined process errors were produced. The influence of these defects on mechanical properties were examined by determining the tensile strength and the elongation at break. The results from mechanical testing are validated with microscopy studies on error samples and tensile specimens. Finally this paper will give a summary of the impact of process errors on mechanical part quality. As an outlook the suitability of high resolution imaging for error detection is discussed. Based on these results a future contribution to quality management is aspired.

Dynamic strength and fracture toughness analysis of beam melted parts

Todays advancement of the market requires innovative thoughts and further development of additive manufacturing processes like beam melting (Direct Metal Laser-Sintering). Among the huge number of additive fabrication methods, the direct manufacturing of metal parts in a powder bed using a laser or electron beam is called beam melting. This neutral term is relatively new and was used in the VDI Guideline 3404 for the first time. In general the additive fabrication differs from conventional technologies by its layerwise and additive joining together material to a physical part. For the construction and the use of beam melted parts and in order to reduce the risk of mechanical defects in a part, a comprehensive material understanding is essential. Cracks caused by dynamic loads can be avoided in advance by dynamic analysis, appropriate design and correct manufacturing of the parts. For this reason, dynamic strength analysis (using a rotating bending test) of beam melted parts made of stainless steel has been applied and Woehler curves for different survivabilities determined. To highlight the resistance of beam melted parts to operation and production damage, the fracture toughness (stress intensity factor) of beam melted parts has also been investigated.

Flow Characteristics of Porous Metal Structures for Specified Permeability Manufactured by Laser Beam Melting Technology

The characteristic additive build-up at the laser beam melting technology provides the opportunity to freeform porous and defined structures at specific areas in one part. By adjusting the process parameters specific characteristics of the manufactured part such as density, permeability, pore size, porosity and shear strength can be realized. The manufacturing process of a test body is described in detail.The permeability of the manufactured parts is investigated experimentally. In addition a numerical model is build and the flow structure inside of the test body is illustrated. The numerically obtained results are compared to the experimentally obtained results.To show the advantages of this technology for future applications a numerical model of a porous blade surrounded by a hot gas flow and cooled from inside of the porous structure is investigated. The results show that the method to define the characteristics during the laser beam melting process has to be optimized.© 2014 ASME