Sample geometry transformation for mechanical tests of constructional materials in an FDM structure

Abstract

The aim was to obtain a rough determination of the dimensions and shape of a sample for an experimental study of the mechanical characteristics of filamentary FDM-printing structures with a low filling at central tension. The sample geometry was designed based on the dimensions and shape provided in the GOST 17370-2017 “Cellular rigid plastics. Tension testing method”. The research methods included the finite element analysis of stress state parameters in an automated environment, elements of the stiffened shell theory and experimental testing of samples. The theory of stiffened shells was used to simplify the geometry of the finite element model for the studied samples. Finite element analysis was carried out in a linear formulation and, based on the results of its combination with the analysis of the technological model of a designed sample, a decision on transforming the sample geometry was made. The samples were produced using a “line” template with an orientation along the longitudinal axis of the sample. According to the results of testing the samples, a conclusion about the success of implied transformation was made. The success criterion involves the destruction of an FDM sample within the limits of the working part. As a result, both external and internal geometries of the prototype sample were transformed. This allowed the main emphasis in the work of the stretchable FDM sample to be shifted to its working part and the trajectory of power flows to be adjusted according to the FDM-printing specifics. Experimental testing of FDM samples with a low “line” template filling showed a consistently satisfactory result: fractures occurred in the working part of test samples. In the course of the studies, the general trend in the dependence of the force flow distribution over the sample volume on the combination of the printing thread trajectory with external and internal geometries of the sample was determined. Future work will focus on a more detailed analysis and formalisation of the obtained results with regard to various printing templates.