Issue 45

L. Zou et alii, Frattura ed Integrità Strutturale, 45 (2018) 53-66; DOI: 10.3221/IGF-ESIS.45.05 61 Figure 8 : Stress results of 5A06+5083 T-joint . Figure 9 : Stress results of 5A06+5A06 T-joint . According to the results of nodal force, Verity module in the FE-SAFE software is used for structural stress computation and equivalent structural stress transformation at weld toe. Computation results of the 5A06+5083 T-joint and 5A06+5A06 T-joint are obtained as shown in Tab.8. Material Specimen number max  MPa Structural stress ( MPa ) Equivalent structural stress range ( MPa ) Cycle numbers when crack （ ×10 6 ） 5A06+5083 1-1 75 51.99 81.19 0.4521 1-3 80 55.45 86.61 0.2257 1-5 70 48.52 75.78 2.08 1-7 60 41.59 64.95 4.3542 1-9 60 41.59 64.95 3.7642 1-11 60.1 42.28 66.04 5.7485 5A06+5A06 2-1 80 74.75 129.69 0.2729 2-2 60 56.06 97.27 1.3366 2-3 50 46.72 81.06 2.3358 2-4 40 37.38 64.85 8.7281 2-7 40 37.38 64.85 4.3287 2-11 40 37.38 64.85 6.3685 Table 8 : Computation results of structural stress and equivalent structural stress range . R ESULTS Master S-N curve for fatigue design ccording to the results of three-point bending fatigue test and the data collected from related literatures [22-25], fatigue database of aluminum alloy welded joints is established. Some of the data in the database are shown in the following Tab.9. There are 76 samples in the database including 7 types of materials, 4 kinds of welding methods, 6 types of plate thickness whose range is from 2.5mm to 16mm, three cases of stress ratio including 0, 0.1 and 0.5, 3 kinds of loading type including tensile(T), four point bending (4B) and three-point bending(3B), 3 kinds of joint type including T-joints, lap joints and butt joints. The fatigue test data of aluminum alloy welded joints is analyzed by using MATLAB software, and S-N curve is expressed in the form of . On bi-logarithmic coordinate , mean S-N curve of the test samples based on lg lg S A B N = + A