Issue 38

M. Lutovinov et alii, Frattura ed Integrità Strutturale, 38 (2016) 237-243; DOI: 10.3221/IGF-ESIS.38.32 240 Figure 1: Results of estimations carried out on the round specimen (a, b) and the hollow tube (c, d) [3].  red is equivalent nominal net stress and S y is yield strength. For maximum principal stresses, Hoffmann–Seeger’s method seemed to be a better upper bound limit than Moftakhar’s method with Neuber’s rule. As in case of stresses obtained on the hollow tube, elastic–plastic strains from the FEM simulation and from the prediction by Moftakhar’s method with the ESED rule are closer than presented in [3]. Maximum principal strain could be well predicted with using Hoffman–Seeger’s method as the upper limit and Moftakhar’s method with the ESED rule as the lower limit. Minimum and middle principal strains could be obtained by using Hoffman–Seeger’s method. All methods however are slightly non-conservative in case of minimum strain at round bar. Non-proportional loading Estimates of stress components  22 and  33 according to Singh’s method are more precise than estimates presented originally in [6]. In case of shear stress component, once the yield stress is exceeded, all four estimations provide non-conservative results. Estimates according to Buczynski’s and Singh’s methods are identical in this region. In the end of the load sequence, Buczynski’s method with the ESED rule provides the most accurate estimate. Shear strain component calculated in the elastic–plastic FEM model with the fine mesh result in substantially higher values than those referred to in [6]. It is possible to use Singh’s methods as the upper and the lower limit. The use of average values of those two methods would lead to a slightly non-conservative solution for the component. Other components are predicted quite well.