PSI - Issue 42

Manuel Sardinha et al. / Procedia Structural Integrity 42 (2022) 1274–1281 M. Sardinha et al. / Structural Integrity Procedia 00 (2022) 000–000

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Table 2: Variables used to compute and evaluate warping.

Symbol

Formula h-dz [mm] dw h × 100%

Quantity Warping

dw

Relative Warping

w

Average Absolute Warping Average Relative Warping

dw 5&6

( dw 5 + dw 6 ) / 2 [mm] ( w 5 + w 6 ) × 50 [%] ( dw i − w 5&6 ) 2 n [mm]

w 5&6

Standard Deviation

σ

3. Results and discussion

This section gives an overview of tests performed and their respective results. As briefly explained, specimens without ironing were printed between samples, allowing a validation of the production protocol during spaced time intervals along the experimental procedure. This group of non-ironed specimens is referred to as series A. The specimens subjected to ironing on the first layers are presented as series B, di ff ering in the layer where ironing starts to be applied (B1 - B3). Series C, D, and E correspond to specimens subjected to equally spaced ironing, di ff ering in the number of ironed layers. Finally, series F and G correspond to specimens with concentrated ironing, from the 3 rd to the 8 th layer and 1 st to the 3 rd , respectively. Table 3 shows the list of tests performed and their respective ironing parameters. Note that the table shows the starting layer, the number of ironed layers, and the spacing between them. Figure 4 shows a summary of these results. Note that, as explained before, all the setups included intermediate non-ironed specimens which average is series A.

Table 3: Nomenclature of the tests performed and its relation with the study variables.

Tests

A B1 B2 B3 C D E F

G

Interval 0 0 0 0 4 2 6 3 rd to 8 th 1 st to 3 rd Start 0 1 2 3 3 3 3 Total 0 1 1 1 11 23 7 6 3

Ironing Layers

Fig. 4: Summary of warping results of series A to G. In blue average relative warping of each series of specimens and in orange the warping percentage reduction when compared with the benchmark (A series), negative values underline an increased level of warping.

A Series: The absolute warping ( dw 5&6 ) registered by the di ff erent samples of the A series, varied from 0.936 to 0.866 mm, a variation of 2.6% of the total height of the specimen.The printed specimens present consistent warping, with roughly the same intensity. Additionally, the value of the average standard deviation σ 5&6 = 0.259 mm was used as the reference value for future comparisons. B Series: The tests performed included ironing only the first (B1), the second (B2) or the third (B3) layer of the specimen. The B series results show that, on average, the absolute warping reduced 75%, from 0.953 to 0.234 mm. As shown, the highest warping reduction was achieved by ironing the second layer (B2), followed by the first and third.