Analyzing the Premature Failure of Rubber Bands in Excavator Track Chains

The rubber bands used in the track chains of excavators, known as track pin rubber bands, frequently experience failures due to factors such as their heavyweight, fast speed, sharp objects on off-road paths, shocks, vibrations, accumulated heat (generated during operation), and track tension. To identify the main cause of these failures, we conducted a failure analysis by evaluating their chemical compositions, morphological, mechanical, and thermal properties. For this study, four different types of failed rubber bands, designated as RB1, RB2, RB3, and RB4, were collected from the track pins of four distinct excavator track chains. None of the selected rubber bands passed the 1000 km running trial. RB1 failed after covering 650 km, RB2 failed after 250 km, RB3 after 400 km, and RB4 after 800 km. Both mechanical and thermal properties are dependent on the chemical formulations of the rubber bands, and all the failed rubber bands exhibited poor chemical formulations. RB1 showed a Schallamach wave on the outer used surface, indicating significant plastic deformation before fracture. In contrast, the other failed rubber bands (RB2, RB3, and RB4) displayed severe mechanical degradation with surface defects such as deep grooves, catering or pitting, micro-cracks, and scars. Thermogravimetric analysis further supported the cause of failure, revealing higher total mass loss and lower residue mass percentages.