Failure analysis of heavy truck trailer axles
A combined analytical/experimental approach was utilized to analyse failures of steel axles in a fleet of refrigeration semi-trailers equipped with dual rear axle air-ride suspensions. Experimental data were used in combination with an analytical model to identify the cause of the axle failures, estimate time to failure, and evaluate the relative effectiveness of proposed design changes to minimize future axle failures. The centrepieces of the program were finite element and fracture mechanics models of the axles. Experiments conducted in support of the analytical models consisted of: (1) field and laboratory inspection of failed axles to determine failure mode and the size of pre-existing flaws; (2) full scale trailer road testing to determine the service load spectrum; (3) fatigue tests on laboratory specimens to determine material properties; and, (4) full scale axle fatigue testing to calibrate and verify the ability of the analytical methods to predict axle lifetimes, and also to evaluate empirically the effect of design and manufacturing process changes. Focus is on the analytical models. Two potential solutions were evaluated, including an axle reinforcing jacket, and replacement of the original axle with a thicker walled axle. The analytical models were a vital tool in determining that both of these solutions effectively extend axle lives so that they have adequate design margins.