シャルピー衝撃試験法によるアルミニウム合金およびその溶接部の破壊靱性の評価について

小林 俊郎

doi:10.2464/jilm.22.10_613

Evaluation of fracture toughness in aluminum alloys and welds by the Charpy impact test

Toshiro KOBAYASHI

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JOURNAL FREE ACCESS

1972 Volume 22 Issue 10 Pages 613-627

DOI https://doi.org/10.2464/jilm.22.10_613

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Published: October 30, 1972 Received: June 16, 1972 Available on J-STAGE: July 23, 2008 Accepted: - Advance online publication: - Revised: -
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Date of correction: July 23, 2008 Reason for correction: - Correction: TITLE Details: Wrong : Evaluation of fracture toughness in aluminum alloys andwelds by the Charpy impact test
Right : Evaluation of fracture toughness in aluminum alloys and welds by the Charpy impact test

Date of correction: July 23, 2008 Reason for correction: - Correction: ABSTRACT Details: Wrong : Standard V notch Charpy specimens with various widths were machined from T-4 treated Al-Zn-Mg and annealed Al-Mg alloy plates and effect of specimen size on impact fracture behavior at low temperatures was studied. Fracture toughness of TIG welds in these alloys and these and of Al-Mg-Si alloy plates was evaluated from load deflection curves during fracture by using fatigue pre-cracked type Charpy specimens.
Although impact values of 5 and 10mm wide specimens were reduced at low temperatures, no change of impact value of 2mm wide specimens was introduced by lowering testing temperatures. The latter fact was considered as an apparent phenomenon since similar effect as in 5 and 10mm wide specimens was also observed by recording the load-deflection curves. The real fracture energy of the specimens was apt to be masked by other energies such as specimen toss energy and energy absorbed in the testing machine. This fact should be taken into account when toughness of aluminum alloys is evaluated.
G_IC value in Al-Zn-Mg and Al-Mg-Si alloys at -196°C was estimated to be about 1kg mm/mm², which agreed well with the value obtained in the previous study for press boundary notch specimens. This shows that press boundary notch specimens can be used to evaluate fracture toughness instead of fatigue pre-cracked type specimens which require troublesome specimen preparation.
Al-Zn-Mg and Al-Mg alloy welds became singificantly brittle at -196°C and showed an unstable rapid fracture mode. G_IC value in this case was evaluated to be 0.550.80 kg•mm/mm². Further to evaluate G_IC from facture load in high stress fracture mode was considered to be questionable since large plastic deformation was introduced near the crack tip. In this case, however, crack opening displacement (COD) obtained from deflection to fracture load in Charpy impact test was considered to be more effective to know the real fracture toughness. With this method, G_IC of Al-Mg alloy plate at -196°C was estimated to be about 5.4kg mm/mm².
Right : Standard V notch Charpy specimens with various widths were machined from T-4 treated Al-Zn-Mg and annealed Al-Mg alloy plates and effect of specimen size on impact fracture behavior at low temperatures was studied. Fracture toughness of TIG welds in these alloys and these and of Al-Mg-Si alloy plates was evaluated from load deflection curves during fracture by using fatigue pre-cracked type Charpy specimens.
Although impact values of 5 and 10mm wide specimens were reduced at low temperatures, no change of impact value of 2mm wide specimens was introduced by lowering testing temperatures. The latter fact was considered as an apparent phenomenon since similar effect as in 5 and 10mm wide specimens was also observed by recording the load-deflection curves. The real fracture energy of the specimens was apt to be masked by other energies such as specimen toss energy and energy absorbed in the testing machine. This fact should be taken into account when toughness of aluminum alloys is evaluated.
G_IC value in Al-Zn-Mg and Al-Mg-Si alloys at -196°C was estimated to be about 1kg mm/mm², which agreed well with the value obtained in the previous study for press boundary notch specimens. This shows that press boundary notch specimens can be used to evaluate fracture toughness instead of fatigue pre-cracked type specimens which require troublesome specimen preparation.
Al-Zn-Mg and Al-Mg alloy welds became singificantly brittle at -196°C and showed an unstable rapid fracture mode. G_IC value in this case was evaluated to be 0.55-0.80 kg•mm/mm². Further to evaluate G_IC from facture load in high stress fracture mode was considered to be questionable since large plastic deformation was introduced near the crack tip. In this case, however, crack opening displacement (COD) obtained from deflection to fracture load in Charpy impact test was considered to be more effective to know the real fracture toughness. With this method, G_IC of Al-Mg alloy plate at -196°C was estimated to be about 5.4kg mm/mm².

Date of correction: July 23, 2008 Reason for correction: - Correction: CITATION Details: Wrong : 4) J. C. Radon and C. E. Turner: J. I. S. I., 204 (1966), 842.
5) G. M. Orner and C. E. Hartbower: Welding J., 40 (1961), 405s.
6) A. T. D'Annessa: Welding J., 44 (1965), 509s.
7) ASTM Committee E-24 on Fracture Testing of Metals: ASTM Designation E399-70T.
10) G. R. Irwin: Encycl. of Physics, 6 (1958), Berlin (Springer-Verlag).
11) W. F. Brown, Jr. and J. E. Srawley: Plane Strain Crack Toughness Testing of High Strength Metallic Materials, ASTM STP 410 (1966).
12) C. N. Freed and J. M. Krafft: J. Materials, 1 (1966), 770.
15) A. A. Wells: Brit. Weld. J., 11 (1963), 563., 13 (1965), 2.
16) A. A. Wells: Symposium on "Crack propaga-tion", Paper No. B4, Cranfield, 1961.
17) G. Ford, J. C. Radon and C. E. Turner: J. I. S. I., 205 (1967), 854.
18) R. Pettit and M. J. Neaves: Met. Const. & Brit. Weld. J., 18 (1970), 157.
19) A. P. Green and B. B. Hundy: J. Mech. Phys. Solids, 4 (1956), 128.
20) G. D. Fearnehough and R. W. Nichols: Int. J. Fract. Mech. 4 (1968), 245.
22) A. Q. Mowbray: Mat. Res. & Std., 4 (1964), 103: ASTM Committee: Mat. Res. & Std., 4 (1964), 107.
23) G. R. Irwin: Welding J., 41 (1962), 519s.
24) W. S. Pellini, L. E. Steele and J. R. Hawthone: Welding J., 41 (1962), 455s.

Right : 4) J. C. Radon and C. E. Turner: J. I. S. I., 204 (1966), 842.
5) G. M. Orner and C. E. Hartbower: Welding J., 40 (1961), 405s.
6) A. T. D'Annessa: Welding J., 44 (1965), 509s.
7) ASTM Committee E-24 on Fracture Testing of Metals: ASTM Designation E399-70T.
10) G. R. Irwin: Encycl. of Physics, 6 (1958), Berlin (Springer-Verlag).
11) W. F. Brown, Jr. and J. E. Srawley: Plane Strain Crack Toughness Testing of High Strength Metallic Materials, ASTM STP 410 (1966).
12) C. N. Freed and J. M. Krafft: J. Materials, 1 (1966), 770.
15) A. A. Wells: Brit. Weld. J., 11 (1963), 563., 13 (1965), 2.
16) A. A. Wells: Symposium on "Crack propagation", Paper No. B4, Cranfield, 1961.
17) G. Ford, J. C. Radon and C. E. Turner: J. I. S. I., 205 (1967), 854.
18) R. Pettit and M. J. Neaves: Met. Const. & Brit. Weld. J., 18 (1970), 157.
19) A. P. Green and B. B. Hundy: J. Mech. Phys. Solids, 4 (1956), 128.
20) G. D. Fearnehough and R. W. Nichols: Int. J. Fract. Mech. 4 (1968), 245.
22) A. Q. Mowbray: Mat. Res. & Std., 4 (1964), 103: ASTM Committee: Mat. Res. & Std., 4 (1964), 107.
23) G. R. Irwin: Welding J., 41 (1962), 519s.
24) W. S. Pellini, L. E. Steele and J. R. Hawthone: Welding J., 41 (1962), 455s.

Date of correction: July 23, 2008 Reason for correction: - Correction: PDF FILE Details: -

Abstract

Standard V notch Charpy specimens with various widths were machined from T-4 treated Al-Zn-Mg and annealed Al-Mg alloy plates and effect of specimen size on impact fracture behavior at low temperatures was studied. Fracture toughness of TIG welds in these alloys and these and of Al-Mg-Si alloy plates was evaluated from load deflection curves during fracture by using fatigue pre-cracked type Charpy specimens.
Although impact values of 5 and 10mm wide specimens were reduced at low temperatures, no change of impact value of 2mm wide specimens was introduced by lowering testing temperatures. The latter fact was considered as an apparent phenomenon since similar effect as in 5 and 10mm wide specimens was also observed by recording the load-deflection curves. The real fracture energy of the specimens was apt to be masked by other energies such as specimen toss energy and energy absorbed in the testing machine. This fact should be taken into account when toughness of aluminum alloys is evaluated.
G_IC value in Al-Zn-Mg and Al-Mg-Si alloys at -196°C was estimated to be about 1kg mm/mm², which agreed well with the value obtained in the previous study for press boundary notch specimens. This shows that press boundary notch specimens can be used to evaluate fracture toughness instead of fatigue pre-cracked type specimens which require troublesome specimen preparation.
Al-Zn-Mg and Al-Mg alloy welds became singificantly brittle at -196°C and showed an unstable rapid fracture mode. G_IC value in this case was evaluated to be 0.55-0.80 kg•mm/mm². Further to evaluate G_IC from facture load in high stress fracture mode was considered to be questionable since large plastic deformation was introduced near the crack tip. In this case, however, crack opening displacement (COD) obtained from deflection to fracture load in Charpy impact test was considered to be more effective to know the real fracture toughness. With this method, G_IC of Al-Mg alloy plate at -196°C was estimated to be about 5.4kg mm/mm².

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