PSI- Issue 9

Tareq Rahman Mahmood et al. / Procedia Structural Integrity 9 (2018) 71–85 Tareq rahman mahmood , et al./ Structural Integrity Procedia 00 (2018) 000–000

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3. Tensile shear test The tensile–shear strength has been selected to characterize the mechanical properties of spot weld. The tensile and shear stresses are playing a significant role during tension test because of the deviation (Dancette et al. 2012). The specimens were spot welded for each of the 27 welding conditions mentioned in table 3. In order to increase the accuracy and the confidence level, the experiment related to each of the parameters combinations was implemented for two times and the average values have been reported. The tensile–shear tests were carried out at a crosshead of 10 mm/min with (WDW-100 Laryee tensile machine). During the tensile tests, three types of failure mode were observed in the used steels; interfacial, partial interfacial, and pullout. These modes are common in welded joints (A.M. Al Mukhtar 2011; A. Al-Mukhtar 2013; A. M. Al-Mukhtar 2013a, 2013b, Al-Mukhtar et al. 2011, 2010; A. Al-Mukhtar and Doos 2013), see Fig. 3.

A

B

C

Fig. 3. (a) pullout failure mode, 0.9 mm thickness; (b) interfacial for HSLA 0.8 mm; (c) partial interfacial, 0.7 mm thickness.

4. Results and discussion 4.1. Low carbon sheet thickness 0.7 mm

These types of steel have been welded according to the plan given by the Design Expert Software program. The process parameters varied as follows; electrode force (1900, 2150, 2640), welding current (5250, 5700, 6750, 7200, 8250), welding time (10, 15, 25, 35). The Model F-value of 45.18 implies the model is significant.

Table 4. ANOVA table analyzed process for 0.7 mm thickness low carbon sheet steel. Source Sum of Squares df Mean Square F Value

p-value Prob>F

Model

23.20

5 1 1 1 1 1

4.64

45.18 0.036

< 0.0001

significant

A-electrode force B-welding current C-welding time

3.666E-003

3.666E-003

0.8520

21.70

21.70

211.27

< 0.0001

0.12 0.31 0.80 2.16

0.12 0.31 0.80 0.10

1.16 3.07 7.83

0.2928 0.0946 0.0108

AC BC

Residual

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