Apr 7, 2017 | By David

Researchers at LLNL (Lawrence Livermore National Laboratory) have successfully tested theoretical models for predicting the behaviour of miniaturized lattice structures under pressure. 3D printing was used to make small-scale lattices on which various tests were carried out. The results of the tests validated the researchers’ theoretical modelling of the structures’ failure behaviour, which is relevant information for their future applications in engineering and design.

You’ll probably be familiar with the lattice structure from trestle bridges, or perhaps its most famous application, the Eiffel Tower in Paris. The lattice allows for low density structures with a high level of specific strength and stiffness, making it hugely popular for all kinds of design and engineering solutions. A large body of research already exists on the various weaknesses of these lattice structures, and how they behave when they fail under pressure. However, this information is based on relatively large lattices. Advances in 3D printing technology mean that the lattice structure can now be miniaturized to a very small degree, and the researchers at LLNL wanted to find out whether the existing predictive models would still apply at a much smaller scale.

3D printed miniature lattice structures were made, and tests were conducted upon them to determine specifics about their failure behaviour. Researcher Mark Messner predicted that there would be a tradeoff between a more graceful yield-dominated and a catastrophic buckling-dominated failure mode at a critical relative density. This prediction was made using a newly developed equivalent continuum model. The critical relative density that he referred to was something that practical tests needed to determine, as it depends on several modeling assumptions that are strongly influenced by the manufacturing process. This is where the Lawrence Berkeley National Laboratory came in, as fellow researcher Holly Carlton made use of its Advanced Light Source.

The Advanced Light Source (ALS) is a specialized particle accelerator, designed to generate bright beams of x-ray light for scientific research. Costing around $99.5 million to build, its operation is funded by the U.S. Department of Energy, Office of Basic Energy Sciences, and it is crucial for observations in a variety of fields, from materials science to chemistry. Carlton used the ALS to conduct quasi-static compression tests on the 3D printed miniature lattices, coupled with in situ tomography, and the results did validate Messner’s model predicitions. The real-time deformation captured in the experiments showed a transition in failure mode from catastrophic buckling to yielding at a low relative density. This critical relative density was around 10-20 percent of bulk density.

Results of the experiments were published by Messner and Carlton in the Journal of Mechanics and Physics of Solids and Acta Materialia respectively. This is the first time that failure behaviour in miniaturized lattice structures has been predicted theoretically and tested out experimentally, and could prove to be crucial for future architecture at this scale. The easy scalability of 3D printing technology, along with the relative cheapness of its application, means that it will continue to be an indispensable tool in the advancement of this kind of research.



Posted in 3D Printing Technology



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Mechabits wrote at 4/8/2017 6:11:01 AM:

4 columns in the corners might help

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