PSI - Issue 34

Atefeh Rajabi Kafshgar et al. / Procedia Structural Integrity 34 (2021) 71–77 Atefeh Rajabi Kafshgar et al./ Structural Integrity Procedia 00 (2021) 000 – 000

73

3

2. Test data and optimization methodology In this section, some optimization methods are employed to investigate the effect of printing parameters on the mechanical properties of test samples made of 3D printed material. These methods are also applied for optimizing and analyzing a set of experimental data reported in Leite et al. (2018). They used different printing parameters in their experimental work and manufactured 24 groups of dog-bone tensile test samples made from PLA material printed with using different printing parameters including raster orientation, printing temperature, infill density, and thickness of layers. Using a standard testing procedure (ASTM D638-02a) the following mechanical properties were obtained from tensile tests: {Ultimate Tensile Stress-UTS, Elongation at Break, Modulus of Elasticity, Yield Strength and Toughness (i.e. the area below the load-displacement curve of each tested sample)}. Fig. 1 shows the schematic graphical abstract for the work done in Leite et al. (2018).

Fig. 1. Representation of experimental work performed by Leit et al. for manufacturing and testing 3D printed tensile test samples made of PLA.

As shown in Fig. 1. The input parameters in the work of Leite et al. (2018) were considered as variables that vary in different discrete levels. Their proposed levels for each processing parameter are summarized in Table 1, in which the selected printing parameters are noted by A, B, C, and D labels. Table 1: Printing parameters' levels (adapted from Leite M., et al. (2018)) Factors Level 1 Level 2 Level 3 A: Infill Density (%) 20 40 60 B: Extrusion Temperature(ºC) 200 220 - C: Raster Angle(º) 0/90 -45/45 - D: Layer Thickness (mm) 0.1 0.2 - The Taguchi method is applied for optimizing the experiments reported in Leite et al. (2018). This method allows reducing the number of experiments. Table 2, shows our proposed L12 orthogonal array and outputs selected from 24 experiments performed by means of standard tensile test sample and procedure in Leite et al. (2018). Since mechanical properties are maximization type, "the larger is the better" criterion is chosen as the mechanism of the Taguchi method. Equation (1) shows signal-to-noise ratio (S/N): 2 n 2.1. Taguchi method

1 n Y =  1 / i

(1)

/ S N

10 log1 /

= −

i