Refining real site TKPH (tonne-kilometer-per-hour) of ultra-large off-the-road tires at mine sites
Creators: Ma, Shaosen
Publisher: name: University of Alberta Library
Year: 2023

<p>The objective of this PhD program is to refine the real site TKPH (tonne-kilometer-per-hour) of ultra-large off-the-road (OTR) tires at mine sites. To achieve this, a novel HLSRT model (a Hysteresis Loss model considering Strain levels, strain Rates, and rubber Temperatures) was first developed as per the experimental results from cyclic tensile tests; it was used to predict the hysteresis loss of OTR tire rubbers. Then this model was used to develop a mathematical equation that predicted the heat generation rates of OTR tire rubbers. Based on this mathematical equation, a new finite element OTR tire thermal (OTRTire-T) model was built to predict the temperatures in OTR tires. As per the results from the OTRTire-T model, the cycle length coefficient K1 and the site ambient temperature coefficient K2 in the real site TKPHs were refined under different site operating conditions (i.e., payloads, cycle speeds, ambient temperatures, and cycle lengths) and the effects of these site operating conditions on the real site TKPHs were investigated.<br>
The results showed that the hysteresis loss of OTR tire rubbers was affected by strain levels, strain rates, and rubber temperatures. A large strain level (e.g., 100%) increased the hysteresis loss considerably. Rubber hysteresis loss increased with a rise in strain rates, and the increasing rates became greater at larger strain levels (e.g., 100%). In addition, a rise of rubber temperatures caused a decrease in hysteresis loss; however, the decrease became less significant when the rubber temperatures were above 10 ℃. The HLSRT model can predict the hysteresis loss of OTR tire rubbers with average mean absolute percent errors (MAPEs) of less than 13.6%. This model characterized the exponential increase of hysteresis loss at rising strain levels and identified the linear growth of hysteresis loss when the strain rate rose.<br>
The OTRTire-T model predicted the temperatures of OTR tires that deviated by less than 8.63% from the on-site monitoring tire temperatures. The model results showed that the temperature in OTR tires increased significantly when the tire was subjected to a large vertical load (e.g., 104 tonnes). The tire temperature increased with a rise in truck speeds, and the increase became more significant at these large vertical loads (e.g., 104 tonnes). Moreover, the model results showed that the tire temperature increased relatively rapidly at rising ambient temperatures from -30 to 40 ℃. <br>
As per the results from the OTRTire-T model, the cycle length coefficient K1 and the site ambient temperature coefficient K2 in the real site TKPH were refined. These refined coefficients provided insights into tire use at long cycle lengths and at cold ambient temperatures. For example, as per the refined K1 coefficients, at an ambient temperature of 38 ℃ and an average cycle speed of 30 km/h, the real site TKPH increased from 2849 to 3049 tonne×km/h at rising cycle lengths from 10 to 20 km. Due to this increment in the real site TKPH, the truck payload was recommended to decrease by 31.8 tonnes when the cycle length was extended from 10 to 20 km. <br>
At cold ambient temperatures of below 0 ℃, as per the real site TKPH with refined site ambient temperature coefficient K2, the loading capacity of the truck increased (compared with its rating payload of 363 tonnes) at mine sites. For example, at an ambient temperature of -5 ℃ and an average cycle speed of 38 km/h, the average vertical tire load was 89 tonnes, which indicates that the truck payload can be considered to be increased by 20.1% (i.e., having a recommended payload of 436 tonnes) during the haulage operations.</p>