2nd ICAI 2022

International Conference on Automotive Industry 2022

Mladá Boleslav, Czech Republic

2. Problem Formulation and Methodology

2.1 Prediction of lifetime If we move within the area of timed strength, the calculation is carried out using two possible procedures: • degree of damage – each load change causes a certain stress amplitude s a in the component, and each of these amplitudes causes some degree of damage to the part. The total degree of damage is the sum of these sub-degrees and the damage to the component occurs if the total degree of damage reaches the value of 1. This procedure is not used for gearing. • equivalent load – this procedure is used to predict the lifetime of bearings and gears because the load on the tooth is repeated (if it is not an inserted wheel). Figure 3 shows an example of a load acting on one tooth of a gearwheel at 10 RPS.

Figure 3: Typical tooth load course

Figure 4: Equivalent stress

Source: own elaboration (2022) Source: own elaboration (2022) Equivalent load σ eq is a load which on one level with the same number of cycles Σ Ni causes the same damage as the load spectrum (Fig. 4). Mathematically, this principle is described by the following equation (5). After rearranging this equation, the calculation of the equivalent load (here equivalent stress) is done following the equation (6).

where σ ai

are partial load values from schematization (Fig. 5),

N i are the schematized numbers of these amplitudes. To calculate the equivalent load using the measured data (the load spectrum), two procedures can be used in principle: • use each measured data taken for the load together with an adequate number of cycles (usually this is the number of gear revolutions during the sampling

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