PSI - Issue 38

Nitish Shetye et al. / Procedia Structural Integrity 38 (2022) 538–545 Shetye et al. / Structural Integrity Procedia 00 (2021) 000 – 000

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beam during one drive cycle ( W T ) multiplied by the number of drive cycles ( N ). The use phase energy is given by (Bouchouireb, 2019): EU = NW T (4) The total drive cycle energy ( W T ) consists of 3 components: the energy needed to overcome rolling resistance ( W R ), the energyneeded toovercome inertial resistance to acceleration ( W A ), and the energy needed to overcome aerodynamic drag ( W D ). The total drive cycle energy is given by (Bouchouireb, 2019): W T = W R + W A + W D (5) The energy needed to overcome rolling resistance ( W R ) is given by: W R = (1 − r ) gc R C R m (6) where r is the fraction of kinetic energy regained during deceleration (assumed to be 15%), g is the acceleration due to gravity, c R is rolling resistance coefficient (assumed to be 0.20), C R is drive cycle dependent given by equation 9 and m is the mass of the bogie beam.

The energy needed to overcome inertial resistance to acceleration ( W A ) is given by: W A = C A m

(7)

where C A is drive cycle dependent given by equation 10.

The energy needed to overcome aerodynamic drag ( W D ) is given by: W D =0.5( ρ a c D C D A)

(8)

where ρ a is the air density, c D is the drag coefficient, C D is drive cycle dependent given by equation 11 and A is the projected area of the bogie beam contributing to air resistance (taken as 0, since the bogie is an internal component of the articulated hauler). Therefore, the energy needed to overcome aerodynamic drag ( W D ) is taken as 0 regardless of the drive cycle. The useful life of an articulated hauler is up to 20,000 hours. It was assumed that out of the total hours of usage, the articulated hauler would be stationary for 25% of the time for activities such as loading, unloading, refuelling, etc. It was estimated that the articulated hauler took 2 s to reach a speed of 10 km/h (2.78 m/s). The speed profile for the time in motion for one drive cycle can be seen in Figure 3. The drive cycle dependent terms ( CR , CA and CD ) were calculated based on the assumed drive cycle using Equations 9, 10 and 11 respectively.

Figure 3. Articulated hauler drive cycle.