Experimental Evaluation of the Size Effect on the Ductile and Brittle Fracture Toughness of a Steel Pressure Vessel

Abstract:

Experiments of fracture toughness with non-standard SENB specimens of five different thicknesses were performed to investigate the size effect on the ductile and brittle fracture for different temperatures. From the experimental results it is found that size effects both brittle and ductile fracture with the same trend but for different mechanical reasons. The ductile fracture toughness increases firstly with increased plastic deformation zone size and plastic fracture strain under general yielding conditions, and then drops down due to the plastic deformation zone size not changing much which is less than the residual ligament width and the increase of the proportion of the high stress triaxiality zone to the whole specimen. The fracture toughness of the lower shelf increases with increasing thickness of the plastic deformation zone size under small scale yielding conditions, and then drops down due to the increase of the high out-of-plane constraint.

• Periodical: Materials Science Forum (Volume 614)
• Pages: 41-46
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.614.41
• Online since: March 2009
• Authors: Zhao Xi Wang, Hui Ji Shi, Jian Lu
• Keywords: Fracture Affect Volume, Fracture Toughness, Size Effect, Stress Triaxiality

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[5] [10] [15] [20] [25] [30] [35] Load (KN) CMOD(mm) 22mm 16mm 12mm 8mm 4mm Fig. 1 Fracture toughness VS specimen size schematically Fig. 2 Load/unload method Fig. 3 typical brittle fracture surface Fig. 4 typical ductile fracture surface -70 -60 -50 -40 -30 -20 -10 23. 5 24. 0 24. 5 25. 0 25. 5 26. 0 26. 5 Model: Boltzmann y = A2 + (A1-A2)/(1 + exp(x-x0)/dx) A1: 23. 80473(± 0. 08969) A2: 26. 03424(± 0. 10511) x0: -32. 76767(± 1. 00961) dx: 4. 15624(± 0. 91436) Fracture toughness J integral(KJ/m2) Temperature(o C) -80 -60 -40 -20 0 20.

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[28] [30] [32] [34] [36] [38] [40] [42] Model: Boltzmann y = A2 + (A1-A2)/(1 + exp(x-x0)/dx) A1: 28. 57703(± 1. 51119) A2: 38. 88737(± 0. 96654) x0: -34. 43068(± 4. 58903) dx: 9. 50417(± 4. 95119) Fracture toughness J integral (KJ/m 2) Temperature( o C) Fig. 5 J versus Temperature (4mm) Fig. 6 J versus Temperature (8mm) -80 -60 -40 -20 0 20.

[25] [30] [35] [40] [45] [50] [55] Model: Boltzmann y = A2 + (A1-A2)/(1 + exp(x-x0)/dx) A1: 24. 96454(± 2. 45683) A2: 49. 62719(± 2. 25519) x0: -37. 08256(± 3. 25614) dx: 8. 53(± 3. 3152) Fracture toughness J integral (KJ/m2 ) Temperature( o C) -70-60-50-40-30-20-10.

[20] [30] [40] [50] [60] Model: Boltzmann y = A2 + (A1-A2)/(1 + exp(x-x0)/dx) A1: 22. 83142(± 1. 58537) A2: 54. 32069(± 0. 54431) x0: -55. 85876(± 0. 67396) dx: 3. 69983(± 0. 59356) Fracture toughnes J integral(KJ/m 2) Temperature(o C) Fig. 7 J versus Temperature (12mm) Fig. 8 J versus Temperature (16mm) -70 -60 -50 -40 -30 -20 -10.

[20] [25] [30] [35] [40] [45] [50] [55] Model: Boltzmann y = A2 + (A1-A2)/(1 + exp(x-x0)/dx) A1: 20. 09944(± 1. 997) A2: 45. 38342(± 0. 963) x0: -56. 6391(± 1. 008) dx: 2. 32058(± 0. 829) Fracture toughness J integral(KJ/m.

[2] ) Temperature(o C).

3 6 9 12 15 18 21 24.

[14] [21] [28] [35] [42] [49] [56] uppershelf lowershelf Fracture toughness J integral(KJ/m2) Thickness(mm) Fig. 9 J versus Temperature (22mm) Fig. 10 J versus thickness original crack tip current crack tip crack propagation path Fig. 11 typical brittle fracture surface.

DOI: 10.1017/cbo9780511623127.005