FINITE ELEMENT ANALYSIS OF A TI6AL4V (ELI) MEDICAL IMPLANT PRODUCED THROUGH ADDITIVE MANUFACTURING

Published ThesisMedical implants created by Ti6Al4V (ELI) through Additive Manufacturing (AM) processes have a very positive impact on the quality of life of patients who have undergone skeletal reconstructive surgery. The effectiveness of medical implant design for AM processes would be significantly improved if finite element analysis (FEA) could be established as an accepted design tool. This study is aimed at validating FEA as a tool for predicting the strain distribution in a Ti6Al4V (ELI) medical implant produced through a selective laser melting (SLM) process by comparing the FEA results with strain gauge measurements. The approach followed was to demonstrate the correlation between an FEA model and strain gauge measurements performed on a human mandibular implant. For the design of the mandibular implant the geometrical data of an adult human mandible obtained from a computer tomography (CT) scan was transferred to a computer-aided design (CAD) software package. A CAD model based on this data, which was suitable for experimental validation, was used for FEA when subjected to typical static mastication load condition. Through this FEA simulation the distribution of strain in the implant under basic functional condition was determined. Using the same CAD model, an implant was manufactured through SLM and strain gauges were mounted on the implant at locations corresponding to the areas of significant strain as determined on the FEA model. The results obtained from both FEA and strain gauge measurements were compared and a correlation within a deviation of less than 10% for most of the measurements was obtained. Requirements for achieving this level of correlation were determined. It was concluded that FEA is indeed a powerful tool for improving the effectiveness of design for AM of medical implants

Towards Qualification in the Aviation Industry: Impact Toughness of Ti6Al4V(ELI) Specimens Produced through Laser Powder Bed Fusion Followed by Two-Stage Heat Treatment

Laser powder bed fusion (L-PBF) has the potential to be applied in the production of titanium aircraft components with good mechanical properties, provided the technology has been qualified and accepted in the aviation industry. To achieve acceptance of the L-PBF technology in the aircraft industry, mechanical property data needed for the qualification process must be generated according to accepted testing standards. The impact toughness of Ti6Al4V extra low interstitial (ELI) specimens, produced through L-PBF followed by annealing, was investigated in this study. Charpy impact testing complying with American Standard Test Method (ASTM) E23 was performed with specimens annealed and conditioned at low temperature. On average, the toughness recorded for the specimens with 3D-printed and machined V-notches was 28 J and 31 J, respectively. These results are higher than the 24 J required in the aerospace industry. Finally, fractographic analyses of the fracture surfaces of the specimens were performed to determine the fracture mechanism of the Ti6Al4V(ELI) impact specimens