PSI - Issue 37

Rogério Lopes et al. / Procedia Structural Integrity 37 (2022) 115–122 R. F. Lopes et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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3. Results

• Strain The first results are related to the acquired strain data. According to the Fig. 2, it is possible to state that the acquisition of strain variation signals was performed in 6 different places by 6 strain gauge. According to the data provided by the manufacturer, this system has 3 different materials: alloy steel S355 J2H; allow steel EN 10130 DC01 and the aluminum panel EN AW 5754 H111. The acquisition of the signals was performed at a frequency of 5 being successful, for their analysis it is possible to split them according to the material where they are located. From all strain gauge only 4 of them are located in S355 J2H whose yield stress is 345 , while the remaining 2 are located in EN 10130 DC01 whose yield stress is 140 . The plots shown in the Fig. 4 evidences that only two strain gauges suffered permanent deformation and they are located in the material EN 10130 DC01, represented by N2 and N3. The remaining elements kept in an elastic behavior.

-0.006 -0.005 -0.004 -0.003 -0.002 -0.001 0 0.001 0.002 0.003 0.004 0.005 0.006

-0.0005 -0.0004 -0.0003 -0.0002 -0.0001 0 0.0001 0.0002 0.0003 0.0004 0.0005

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300 600 900 1200 1500

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500

1000

1500

Strain

Strain

Time [s]

Time [s]

N2

N3

N1

N4

N5

N6

b)

a)

Fig. 4. a) Plot of strain variation in alloy steel S355 J2H and b) plot of strain variation in allow steel EN 10130 DC01

• PSD algorithm According to what was presented above, an algorithm was developed in Matlab language that composes a set of equations. Through this algorithm is possible to present a set of values, real and virtual. In the Fig. 5, there are two plots, where a) encompasses two curves. The impactor strikes the door at 8.56 / and at each increment it is updated with the decay variation of velocity. It should be noted that this curve is obtained by virtual values, since is a static test, however, it allows the user to simulate the dynamic behavior. On the other hand, it is possible to observe the impactor displacement curve, this causes an intrusion of the door of about ≈ 40 . The experimental test duration is an irrelevant parameter, however, having calculated the ∆ and the number of performed steps, it was possible to determine the collision would take approximately 8.5 . On the plot b) the extracted values come from directly the load cell. As can see, this structure suffers buckling, after this phenomenon occurs the door absorbs almost the same energy by increasing displacement. In other words, the stiffness of the system remains similar in the plastic behavior of the structure. Another relevant aspect to mention is the absorbed energy by the door, which should be close to the initial kinetic energy, calculated by the velocity and mass of the impactor. The absorbed energy by the system is given by the area under the curve in curve b). In the system of equation (7) the theoretical and experimental energy is calculated, whereas in equation (8) the deviation, which as seen is quite low, being a positive point for the success of the test. { = 1 2 2 = 1 2 ∙ 45 ∙ 8.56 2 ≈ 1648.7 = ∑ +1 + 2 ∙ ( +1 − ) ≈ 1650.1 17 =1 (7)