PSI - Issue 13

Ali Waqas et al. / Procedia Structural Integrity 13 (2018) 2065–2070 Author name / Structural Integrity Procedia 00 (2018) 000 – 000

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The analysis of broken samples reveals the samples to be shear fracture with no signs of cleavage as shown in Fig. 4. The fracture behavior of all the samples was identical with a slanted plane of shear in both horizontal and vertical specimens. This may be because of a balance of shear and tensile forces. According to ASTM E23-07a, if the samples are not fully broken and there is no cleavage fracture seen, it should be considered as 100% shear fracture. The sample were closed at hinges only once and taken back to separate, and all of themwere separated according to the instructions given in standard.

Fig. 4. Fractured sample after separation by joining the hinges (a) Front view; (b) Top View.

Lateral expansion of the specimens has been normalized as the samples were sub-size. The normalized lateral expansion is given by the ratio of change in width to the original width of the sample multiplied by 100. The lateral expansion all the samples is also in the similar range. Higher values of lateral expansion support the idea of fracture being ductile. Fractography of samples was performed on a TESCAN Vega scanning electron microscope with depth mode for both horizontal and vertical specimens. The results in both directions are similar giving a dimpled surface appearance having a shear fibrous tearing of material as depicted by ductile materials.

Fig. 5. (a) Fracture surface of horizontal specimen; (b) Fracture surface of Vertical specimen.

The absorbed energy of the sub-size sample corresponds to the absorbed energy of full size specimen based on the area of ductile or brittle fracture. If the specimen exhibits pure ductile fracture, the energy is simply the ratio of cross sectional areas ( Nanstad &Mikhail, 1994; Lucon , Mccowan, & Santoyo, 2015). Taking into consideration the above mentioned results, it can be deducted that the fracture is pure shear and hence pure ductile fracture. So, the values of absorbed impact energy for sub-size sample were simply multiplied by the normalization factor (2 in this case) to attain the impact energy mentioned in table 1. The composition of the electrode wire melted to create the thin wall is low carbon steel having the composition as C 0.1%, Mn 1.56%, Si 0.88%, S 0.012%, P 0.011%, Ni 0.01, Cr 0.02%, Mo <0.01%, V <0.01%, Cu 0.24%. Low carbon steel with comparable hardness has lower impact toughness at room temperature (Bauccio., 2013; Davis, 1996).