Failure Investigation of a Wheel Type Ride

A Rotating Giant wheel ride at an amusement Park in Lahore went through an accident and fell on the ground, resulting into three casualties and injuries of two school kids. It was noted that the ride failed just two weeks after its installation. The central shaft which was acting as a cantilever was broken into two pieces. Onsite visual inspection along with hardness measurements was carried out within few days after the accident. It was observed by examining the broken shaft that fatigue failure occurred due to the sudden step made on peripheral of the shaft during manufacturing. This step which was machined to fit the size of bearing caused enough stress concentration to develop on the outer surface of the shaft. It was also noted that the nominal load was exceeding the maximum allowable load. It was shown by detailed calculations that the shaft itself was not able to withstand full load even in the absence of any stress raiser, and the cross-section of the axle was ‘just sufficient’ to withstand the bending force applied on the axle (shaft) when the giant wheel ride was under full load. The shaft was modeled and analyzed later on by using ANSYS workbench to simulate and verify the theoretical calculations.