PSI - Issue 47

Andre Hartawan Mettanadi et al. / Procedia Structural Integrity 47 (2023) 168–175 Mettanadi et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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experimental displacement which tended to become unstable when passing 80 mm. If observed from the number of lobes found at t = 8 ms, the lobes formed for Cyl-1 are 8 lobes, and the lobes formed from BBT-1 are also the same as many as 8 lobes. 4.2. Mesh convergence study A mesh convergence study is carried out to determine the appropriate number and size of mesh for further studies. The results of a simulation are influenced not only by the geometry and material properties but also by the shape and size of the mesh. If a curve is made with the horizontal axis being the number of elements and the vertical axis being the simulation results, a logarithmic curve will usually be formed. On the logarithmic curve, the number of elements and the size of the mesh that can be used can be determined. The determination can be made by looking at the number of elements that have started to converge (if the elements are multiplied it does not have a big effect on the result). The results of the convergence mesh curve can be seen in Figure 8a. The figure shows that the greater the number of elements, the smaller the absorbed force. In the number of elements 4320, the value of energy absorption reaches 22.5 kJ/kg. This value decreases as the number of elements increases. However, when it comes to element 23402, the energy absorptions tend to stabilize at 9.5 kJ/kg. Mesh convergence is achieved at an energy absorption value of 8.17 kJ/kg with a number of elements of 93148. The opposite is true for displacement where the bigger the number of elements, the greater the displacement that occurs, can be seen from Figure 8b, the mesh convergence is achieved when the displacement is 115.552 mm with the number of elements 93148

Convergence Line

Convergence Line

(a) (b) Figure 8. Results of the convergence study based on the given parameters: (a) energy absorption; and (b) displacement.

5. Conclusions The results showed that finite element analysis for Cyl-1 has been proven. The results show that for mesh convergence, which was carried out using element number analysis, the energy absorption obtained tended to be stable when reaching element 23402. Mesh convergence was obtained at energy absorption values of 8.17 kJ/kg and displacement of 115.552 mm with a number of elements of 93148. Peak crushing force (PCF) obtained was 92.38 kN, and the mean crushing force (MCF) obtained was 79.09 kN. The contour formed in the simulation results has shown that the deformation of Cyl-1 is axially regular and the most deformed part is the surface close to the contact of the moving rigid wall. The lobes formed from the numerical results of 8 lobes are the same as the lobes obtained from the benchmark data. Furthermore, there is a need for related analysis regarding variations in the compression speed used so that the object can be known at the collision speed at which it succeeds in absorbing the maximum force. Material variations and receiving angles also need further investigation as well as the inertial weights used.