Off-the-road tires (OTR) are a category of vehicle tires that use deep tread to provide more traction on unpaved surfaces such as loose dirt, mud, sand, or gravel. This type of tires is often deployed in severe operating environments such as construction and mining industry. Consequently, their development is quite laborious and costly. In general, their sheer size and weight make them unsuitable for drum endurance tests, and as a result, places a high demand on OTR tire developers to design with precision and for longevity. As such, it is crucial that the developers of OTR tires be aware of the load intensities and damage on the material planes of the various tire components right at the design stage of the production process. Computer modeling and analysis has advanced in recent times and for this particular case, it offers plausible solution to the problem.
Generally, off-road ultra-large tires experience different modes of heat-related fatigue failure in operation due to inherent material defects that grow into visible cracks under service loads. Literature has it that crack nucleation and growth rates in rubber depend largely on their constitutive behavior in response to imposed loads. To this note, a number of material testing and characterization approaches have been presented. Nonetheless, further research is need.
In this context, Missouri University of Science and Technology researchers Dr. Wedam Nyaaba and Professor Samuel Frimpong from the Mining and Nuclear Engineering Department in collaboration with Dr. Angelina Anani from Pontifical Catholic University of Chile implemented the cracking energy density theory to predict nucleation life of selected components of a 56/80R63 tire. More so, the sought to compare the fatigue life estimates of the tire components with and without SIC effect. Their work is currently published in the research journal, International Journal of Fatigue.
In brief, the multiaxial strain histories needed for the damage calculation on each material plane were obtained via Abaqus/Explicit finite element analysis (FEA). The team then implemented a rainﬂow counting algorithm to identify and count strain reversals associated with each deforming plane. Per se, crack nucleation life estimates were compared between purely mechanical and combined thermal-mechanical loading histories in selected components of the tire.
The authors reported that the computed energy release rates relied on the orientation of a cracking plane relative to the axis of applied loads. Moreover, the local plane loading signals were seen to be very intricate and varied in amplitude across a cycle. Altogether, the researchers established that the fatigue damage was severe under high axle load and speed conditions.
In summary, a critical plane analysis procedure was applied to predict failure planes in the sidewall, belt, and tread components of a 56/ 80R63 tire. On a light note, the method considers the nominal multiaxial strains, material constitutive model, and fatigue crack growth rate properties of the rubber to compute the energy release rates on the tire’s material planes via the cracking energy density (CED) fatigue predictor. Overall, the authors highlighted in their study that the combined effect of thermal and mechanical loads had a negative effect on the tire fatigue performance.
Wedam Nyaaba, Samuel Frimpong, Angelina Anani. Fatigue damage investigation of ultra-large tire components. International Journal of Fatigue, volume 119 (2019) page 247–260.Go To International Journal of Fatigue