2nd ICAI 2022

International Conference on Automotive Industry 2022

Mladá Boleslav, Czech Republic

3.3 Equivalent load For each journey made, it is possible to calculate the equivalent load according to the equation (6) modified to torque, i.e.:

where T i are the centres of the schematization levels (Fig. 10 first column), n i are partial relative numbers of shaft rotations (Fig. 10 second column). Due to the use of relative values for the number of revolutions in the equation (7), there is the expression ∑ h i=1 = 1. When quantifying the example in Fig. 10, it is: • for exponent q G = 3 (bearing) is T eq,G = 75.94 Nm, • for exponent q H = 5 (contact) is T eq,H = 92.52 Nm, • for exponent q F = 9 (bend) is T eq,F = 114.71 Nm. 3.4 The principle of recalculation the lifetime according to equivalent load The given values of the equivalent moment can then be used to calculate the service life of gears from a given load spectrum, where each gear has a different torque calculation value for contact inspection and another for bending. If the calculation is made from combinations of different measured routes, it is necessary to: • select or find a suitable combination of these routes, for example, 50% of motorways, 30% B-roads and 20% in town, • reduce the frequency (see Table 2 column 2) for individual schematizations by the indicated percentage and then add up the route frequencies, • from the schematization obtained that way, relevant equivalent moments must be calculated. 4. Conclusion The above data show that for the gear lifetime as well as for other parts of cars (and not only cars), where there is considerable stochastic (random) load, it is necessary to know the actual load spectrum for optimization as best as possible, to avoid inadequate dimensioning of these parts. Using the maximum torque moment of the drive for these calculations is completely inappropriate. Compare the maximum torque T max , which is in the record approx. 200 Nm to the calculated equivalent values according to paragraph 3.3. In this context, it should be noted that the service lifetime of the parts is exponentially dependent on the load due to the exponent of the S-N curve. For example, when changing the calculation load using the above-stated example, it is from T max = 200 Nm to T eq,H = 92.52 Nm, it means an increase Δ of a calculated lifetime:

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