Issue34

E. Marcisz et alii, Frattura ed Integrità Strutturale, 34 (2015) 379-386; DOI: 10.3221/IGF-ESIS.34.42 382 T EST R ESULTS he 2024 aluminum alloy specimens were tested under bending with range frequency of 11-14 Hz and a given amplitude parameter in the range of W a = 0.2-0.4 MJ/m 3 . During the tests, histories of stress, strains, energy parameters and hysteresis loops, (  -  ), were measured and registered. Fatigue test with controlled bending moment amplitude have been conducted in range  a = 187.5 – 255 MPa. Fig. 5 shows the exemplary history of energy parameter, W(t), and in Fig. 6 the history of stresses, σ(t), and strains, ε(t), (the first 6 blocks cover from 0 to 64000 cycles, the next 2 blocks represent cycles from 64000 to 166000 cycles). The example, shown in Fig. 5 concerns the results of the amplitude of the energy parameter W a = 0.30 MJ/m 3 , the specimen, which was failured after N f = 348100 cycles. Based on the present course of W(t), it can be seen slight fluctuations in the amplitude W a , which are the result of periodic (non-continuous) calculations of this amplitude in the control system for the new values of stresses and strains. Relative error, ∆W, in this example was below 10%. Figure 5 : Exemplary history of the energy parameter, W(t), under bending in the function of time, t = n  t, n - number of discrete history values,  t = 1.2987  10 -5 s - sampling time a) b) Figure 6 : An exemplary history: a) - the stress σ(t), b) - strain ε(t) under bending in the function of time, t = n  t, n - number of discrete history values,  t = 1.2987  10 -5 s - sampling time T