PSI - Issue 38

472 Isabel Huther et al. / Procedia Structural Integrity 38 (2022) 466–476 Huther et al./ Structural Integrity Procedia 00 (2021) 000 – 000 = ∙ (1) with = 1.94 , stress concentration factor at the weld toe evaluated by calculation. Then the overload to apply in force is equal to (2). = ∙ = ∙ ( ∙ ) (2) 5.2. Local plasticity and residual stress Firstly, two overload levels between 1.05YS and 1.67YS are investigated on three specimens to evaluate the effect on local plasticity and residual stresses 5.2.1. Strain results On one specimen (ep 3), the static test was performed applying charge/discharge cycles from F n = 120 kN to 2 F n , = 240 kN by step of 15 kN; 2 F n = 240 kN corresponds to a local stress at the weld toe (  l ) equal to 1.67 YS. The Figure 7 shows the strain state mapping according to the X axis for a load of 215.4 kN (1.5 YS). The maximum local deformation is 0.7-0.8%. It may be noted that the growth of virtual and physical strain measures on J5b and J5 or on J6b and J6 is similar. 7

Figure 7 Strain mapping and virtual gages J5b and J6b for a load of 215.4 kN, [5] On the second specimen (ep 2), the static test was performed applying the load until 2 F n (1.67 YS) at one go. The Figure 8a shows the strain state mapping for the maximal load of 240 kN. Fringes are observed, there are perhaps shear bands with an orientation related to the welding process, weld direction from B to A. For a maximal load of 150 kN, fringes are also observed [5], [6]. The Figure 8b shows the values of the strain gages. The load-displacement curves for the two static tests show a residual displacement similar of the order of 0.3 mm (Figure 9), corresponding to strain values between 5000 and 8000 µd (ex. Figure 8b), resulting of a local plasticity. There is not difference between overload step by step or at one go. On the third specimen (ep 1), the static test was performed applying the load until 1.25 F n (1.05 YS) at one go. The Figure 9 shows the strain state mapping