PSI - Issue 47

Andreal Muhammad Naufal et al. / Procedia Structural Integrity 47 (2023) 133–141 Naufal et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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5. Results and Discussion 5.1. Comparison of the laboratory testing and numerical calculation

The specimen experiment used a universal testing machine with ASTM D7264 standard. From the test results, a graph of point load vs elongation was also obtained (Figure 7). The fault characteristics due to testing form a fault on the facing side that is directly exposed to contact by the stroke. After that, the core will be damaged as the engine stroke deepens. However, until the test ends, there is no damage at all to the lower facing (lower facing is not directly hit by the hammer). When this pattern is compared with numerical results (see Figure 8), it has similarities in the fault section. It can be seen in the red section located right in the middle of the specimen, where the hammer/stroke presses on the workpiece. Benchmarking is carried out by comparing simulation results with three-point bending laboratory test results (see Figure 7). The results of numerical simulation (black line) should not differ by more than 10% when compared to laboratory tests (red line). Benchmarking is important to know the suitability of the aspects in numerical simulation following the results obtained. Aspects that affect numerical simulation results include mesh configuration, material properties, contact, and boundary conditions. When compared using graphs, laboratory tests and numerical simulation has the same trend line. However, the graph of numerical simulation results is above the graph of the testing laboratory. In addition, in numerical simulation, there is a temporary increase in point load at the beginning of numerical simulation before returning to the original graph, in addition of that, the numerical simulation graph flattens for a while when touching the ultimate strength before a fault finally occurs. In the numerical simulation, a maximum point load of 195.91 N is obtained (see summary in Table 3 and Figure 9), where the maximum point load in the laboratory testing is 200.27 N or has a difference of 2% smaller when compared to the laboratory test results. Meanwhile, the results of elongation data in the numerical simulation were obtained at 6.35 mm while elongation in the laboratory testing was obtained at 6.88 mm or had a difference of 7.7% smaller than laboratory testing. Based on those results, the current studies can be concluded that the numerical simulation results already resemble laboratory tests and the configuration of numerical simulations can be used for future research.

Table 3. Results of the three-point bending: test vs. simulation. Methods

Max. Point Load (N)

Max. Point Stress (MPa)

Elongation (mm)

Laboratory testing Numerical simulation

200.27 195.91

67.97 66.09

6.88 6.35

2.50E+02

Laboratory Testing

Numerical Simulation

2.00E+02

1.50E+02

1.00E+02

Point Load (N)

5.00E+01

0.00E+00

0

1

2

3

4

5

6

7

8

Elongation (mm)

Figure 7. Comparison Results Between the laboratory testing and numerical simulation.