3D printing has enabled new avenues to design and fabricate diverse structures for engineering applications, including simple and complex lattice structures. Lattice structures are useful as implants for spinal fusion treatments, by providing mechanical scaffolding while supporting biological tissue growth.  However, inconsistencies in the printing process lead to variable mechanical responses in part performance and motivate a need to quantify uncertainties contributing to mechanical failure using probabilistic analysis. Here, we conduct a reliability analysis by assessing the quasi-static response of a biocompatible stereolithography printed lattice in compression with a repeating unit cell topology. The purpose of the reliability analysis is to determine the influence of the manufacturing process on mechanical lattice response.  50 cubic unit cell lattice samples designed with 50% porosity, 500-micron beam diameters, and dimensions of 3.5mm by 3.5 mm by 3.5 mm were fabricated and tested. Compression testing was conducted on all lattice samples to measure their force-displacement response.  Lattice Elastic moduli ranged from about 298 MPa to 311 MPa, with a mean of 305 MPa.  The distribution of Elastic moduli followed a Gaussian curve. The average length, width, and height measurements ranged from 3.47mm to 3.48mm. The precision in printing with a 95% confidence level was greater than 99.7%. Analyses were conducted with NESSUS software. The distributions of the input parameters were determined using (i) Chi-square test, and (ii) Maximum entropy method. The maximum entropy method was used on two different sample sizes of 20 and 50 samples. The 20 samples were chosen from the larger set of 50 samples randomly to reduce biases. The findings demonstrate that there was no significant difference in the distributions for the two different sample sizes. Whereas the distributions were similar for most of the random variables, the Elastic moduli had a value of 2.01 from a Z-test that suggests there was a marginal difference in two samples. All 50 samples were used to reduce biases for the maximum entropy distribution. To verify whether the sample size is adequate a convergence test was conducted. The First-order reliability method was used to calculate the probability of failure and sensitivity of each input parameter. The Elastic modulus was the most sensitive among all input parameters, with 31% of the total sensitivity. Findings demonstrate the precision of biocompatible stereolithography printing and the foundations for uncertainty quantification failure in 3D printed lattices.  Overall, the study is (i) a significant step forward for investigating consistencies and differences in printed parts when comparing lattice structures, and (ii) provides a basis for further reliability analyses when considering the vast design space enabled by 3D printing designs and processes


Mechanical Testing and Reliability Analysis for 3D Printed Cubic Lattices

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

IMECE2020 - Virtual Conference

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.