SteBLife – A new short-time procedure for the evaluation of fatigue data

Thermodynamic entropy as a marker of high‐cycle fatigue damage accumulation: Example for normalized SAE 1045 steel

“…24,26,37 The constant W p is given as a default constant, since the above parameters are determined constantly for a fatigue test. However, numerous studies [38][39][40][41][42][43][44][45][46][47] have shown that the temperature evolution of a specimen or a component that had been exposed to a load amplitude higher than its fatigue limit appears in three stages, which is schematically represented in Figure 2. This can be divided into an initial temperature increase (Stage 1), a predominant temperature stabilized stage (Stage 2) and a sudden temperature increase stage close before fracture (Stage 3).…”

SteBLife, a New Approach for the Accelerated Generation of Metallic Materials’ Fatigue Data

“…Following this strategy, three different SteBLife modules were developed up to this date. The first one is SteBLifestc (stc: single test, trend curve) allowing to calculate a trend S-N curve based on one single test with a duration of 2-3 h. The full procedure of the SteBLifestc approach can be seen in Figure 6 [24,27]. For the calculation, generalised Morrow [32] and Basquin [17] equations are combined in order to calculate the fatigue life and an S-N dataset for the material investigated.…”

“…Following this strategy, three different SteBLife modules were developed up to this date. The first one is SteBLife stc (stc: single test, trend curve) allowing to calculate a trend S-N curve based on one single test with a duration of 2-3 h. The full procedure of the SteBLife stc approach can be seen in Figure 6 [24,27]. The third module SteBLifemsb (msb: multiple tests, scatter bands) offers the possibility to calculate scatter bands for different failure probabilities, which is an important feature even in the case of more inhomogeneous materials like, e.g., cast irons., therefore, 4-5 SteBLife tests are performed at the same stress amplitude and the obtained lifetimes Nf can be interpreted by a Gaussian distribution allowing to determine the lifetimes for different failure probabilities, as, e.g., 5%, 50% and 95% (or others).…”

“…The third module SteBLife msb (msb: multiple tests, scatter bands) offers the possibility to calculate scatter bands for different failure probabilities, which is an important feature even in the case of more inhomogeneous materials like, e.g., cast irons., therefore, 4-5 SteBLife tests are performed at the same stress amplitude and the obtained lifetimes N f can be interpreted by a Gaussian distribution allowing to determine the lifetimes for different failure probabilities, as, e.g., 5%, 50% and 95% (or others). The procedures of SteBLife mtc and SteBLife msb are explained more in detail in [25,27,33] as well as based on the results discussed in Section 3.…”

“…The SAE 1045 steel in the normalisation condition has a Vickers hardness HV10 of 218, a 56 J m cm −2 KCU (impact energy for Charpy U-notched specimens) and a mostly ductile behaviour under (quasi)static and cyclic loading. The material's properties are summarised in Table 2, comparing [24][25][26][27]. The investigated quenched and tempered SAE 4140 (42CrMo4) steel is in accordance with DIN EN 10083-3 and its chemical composition is given in Table 3.…”