The number is called the zero-padding factor.
The zero-padding factor is the interpolation factor for the spectrum, i.e., each FFT bin is replaced by bins, interpolating the spectrum.
Taking the real behavior of a friction brake pad as the example of Fig. 12 [14] 14], the following considerations arise: the brake pad friction factor is clearly dependent on three parameters: the speed, the dissipated energy that mainly depends on clamping forces and starting speed, and the clamping forces applied to the pad.
An accurate identification of the influence of the braking pad friction factor on braking performances allowed obtaining reliable results.
Open image in new window Fig. 14 Number of satisfactory simulation results as a function of the admissible value of es (variable pad friction factor is implemented).
Open image in new window Fig. 12 Measured behavior of brake pad friction factor [12, 14], test performed on test rig [23] according UIC test program [22] Open image in new window Fig. 13 Variable braking pad friction factor implemented on TTBS01 for the validation on EMU V250.
As a consequence, by adopting the measured data of the friction [19] and using a narrower population of tests on the train (four braking tests over a population of 50), we identified a feasible behavior of the pad friction factor as a function of the traveling speed and the loading condition of the train (Fig. 13).
Two demographic variables (age and gender) and 4 PAD-risk factors (hypertension [HTN], systolic blood pressure [SBP], and diastolic blood pressure [DBP]), dyslipidemia, high-density lipoprotein [HDL] and low-density lipoprotein [LDL], diabetes, and cigarette smoking) were examined for each group.
Therefore, the proposed method that calculates train braking performances by taking into account the variability of brake pad friction factors has a high feasibility.
