Ingenieur Vol 76 ingenieur 2018 October | Page 20

INGENIEUR Figure 2: Badly rusted structure of the 16-year- old bus Figure 1: Collapsed roof of the bus flattened the passengers’ cabin Figure 3: Pillars welded together by manufacturer Figure 4: The rusted structure at the welded section Figure 5: SEM image of sample from the bus superstructure Figure 6: Grain structure of sample from the bus superstructure ring system (Figure 3 and Figure 4). The welding section was identified as the weakest area, serving as the failure modes at the time of the accident. Further material analysis using Scanning Electron Microscope (SEM) revealed that the bus superstructure was constructed with much lower grade material: cast iron (Figures 5 and 6). In this case, it can be stipulated that cast iron was chosen to save cost. In addition, there was no evidence to establish that the bus structure had been coated to prevent rusting. In another case involving a bus, eight of out 33 passengers died when the bus collided into the rear end of a tanker. The main cause of the crash 6 18 VOL 2018 VOL 76 55 OCTOBER-DECEMBER JUNE 2013