PSI- Issue 9

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

80 10

The tensile strength results for welded low carbon steel 0.9 mm sheet thickness are shown in Fig. 11. The high tensile strength occurring due to high heat input. In this condition all failure is pullout mode. 4.3. High strength low alloy steel Docol 500LA The HSLA sheet thickness is 0.8 mm. The specimens for this group have been welded according to the plan given by the software program (design of expert) the electrode force varied between 199-2640 N, current change from 5700 8250 Amp., and welding time 18-40 cycle. All 27 trails run welded according to the specific parameters condition. After that the specimens are tested in tensile machine and the resulted loads imported in the software table and analyzed. Model Analysis of variance is shown in table 6.

Fig.11. tensile test result for spot welded low carbon steel 0.9 mm sheet thickness

Table 6. ANOVA table model Analysis for low carbon steel with sheet thickness 0.9 mm. Source Sum of Squares df Mean Square F Value p-value Prob > F Model 206.33 4 51.58 24.98 < 0.0001

significant

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

4.69

1 1 1 1

4.69

2.27

0.1462

150.54

150.54

72.92

< 0.0001

3.53

3.53

1.71 9.48

0.2046 0.0055

B2

19.58 45.42

19.58

Residual

22

2.06

The Model F-value of 21.98 implies the model is significant. There is only a 0.01% chance that an F-value this large could occur due to noise. Values of "Prob > F" less than 0.0500 indicate model terms are significant, The "Pred R-Squared" of 0.7206 is in reasonable agreement with the "Adj R-Squared" of 0.7868. The difference is less than 0.2. "Adeq Precision" measures the signal to noise ratio. A ratio greater than 4 is desirable. Model ratio of 13.247 indicates an adequate signal. Therefore, this model can be used to navigate the design space.