PSI - Issue 23

Barbara Nasiłowska et al. / Procedia Structural Integrity 23 (2019) 577– 582 Nasiłowska B. / Structural Integrity Procedia 00 (2019) 000 – 000

581

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Table 1. Results of the fatigue life test for specimens welded with a laser and TIG method, additionally strengthened with surface shot peening with division for initiation N i and in conditions of fractures development N R (N i - a number of cycles to initiation of fractures, N R - a number of cycles under conditions of fractures development)

σ an [MPa]

N f

N i

N R

N i /N f *100%

Average value N i /N f *100%

500

108220 119 300 149 778 265 700 304 360 274 550 531 000 582 100 27 177 25 530 26 050 75 899 71 709 118 395 108 774 20 463 16 087 12 949 12 479 31 066 44 695 39 309 100 128 93 721 51 006 40 114 114 790 114 778 254 192 215 500 26 295 35 828 99 077 131 425 76 077 182 575 241 080 199 805

106 133 100 000 125 000 250 000 290 000 259 000 470 000 480 000 21 000 15 800 17 500 62 000 46 500 88 000 84 000 11 500 10 700 15 000 17 500 15 800 50 000 45 000 39 000 32 000 103 500 86 500 233 001 190 000 19 000 29 500 52 000 82 500 71 500 132 000 179 000 140 000 7 800 4 500

2 087

98.07 83.82 83.45 94.09 95.28 94.33 88.51 82.46 77.27 61.88 67.17 81.68 64.84 74.32 77.22 56.19 66.51 60.23 36.06 56.33 35.35 38.15 49.93 48.01 76.46 79.77 90.16 75.36 91.66 88.16 72.25 82.33 52.48 62.77 93.98 72.29 74.24 70.06

90.76

19 300 24 778 15 700 14 360 15 550 61 000 102 100

430

94.21

370

85.48

Parent material

490

6 177 9 730 8 550

68.77

438

13 899 25 209 30 395 24 774

73.26

375

75.77

Shot-peened

490

8 963 5 387 5 149 7 979

54.75

TIG

438

13 566 28 895 24 309 50 128 48 721 12 006 11 290 28 278 21 191 25 500 8 114

43.28

375

48.97

Non-shot-peened 490

78.11

438

82.76

375

89.91

Shot-peen

490

7 295 6 328

77.29

laser

438

47 077 48 925

69.74

4 577

375

50 575 62 080 59 805

72.20

Non-shot peen

Based on the read-out of the research results in Excel programme, a percentage share of fatigue life to fatigue fractures initiation N i and under conditions of fractures development N R was defined. The greatest difference between a number of cycles to failure and a number of cycles to initiation was observed in the case of the specimens made of the parent material for which a number of cycles in the fatigue fracture conditions was N R = 81 550 (for Δσ an = 370 MPa) on average. For the specimens with a weld made with TIG method ( Δσ an = 375 MPa) – N R = 49 429 cycles; for the specimens made with a laser beam – N R = 57 487 cycles. Experimental tests showed that initiation of a fatigue fracture in the parent material occurred after exceeding 90,