Failure of a Trunnion Axle on a Hard Suspension Multi-axle Trailer

The failure analysis of a trunnion axle on a hard suspension multi-axle trailer is presented. All reported failures have occurred in an unloaded state very shortly after being put into service at or near the top of the trunnion axle in close proximity to a welded round plate. Analyses indicated a pre-existing flaw in the heat-affected zone near the weld. The unloaded state of the trailer, which may have exacerbated the dynamic loading, coupled with the limited damping provided by the hard suspension was likely the driving force for this failure.