ON FATIGUE CRACK PATH DEVIATION AT ELEVATED TEMPERATURE IN ELECTRON BEAM REPAIRED WELDMENTS OF TURBINE DISK
来源期刊：Acta Metallurgica Sinica2004年第4期
论文作者：L.H.Li Y.H.Zhang X.A.Zhang H.Y.Zhao H.Q.Zhang
Key words：fatigue crack growth; crack path deviation; electron beam weld-ing; inhomogeneity of mechanical performance;
Abstract: Fatigue crack growth behaviors in electron beam weldments of a nickel-base superalloy are studied. The objective of this paper is to discuss effects of the inhomogeneity of mechanical performance on fatigue crack growth (FCG) rate and crack path deviation (CPD). The base metal served in a turbine disk of aerospace engine was selected to fabricate bead-on-plate weldments by using electron beam welding. Some wedge-type opening loading specimens, notched in three different zone of weld metal, HAZ and base metal, were employed and performed fatigue crack growth tests at 650℃. The results show that the fatigue crack growth of electron beam welded joints is instable due to the influence of mechanical heterogeneities. Owing to the crack deviation at the weld metal and hcat-affected-zone (HAZ), the effective growth driving force at the tip of fatigue crack was reduced with the reduction of the effective stress intensity factor (SIF) which finally causes fatigue crack rate decrease. Fatigue crack was strongly affected by size and the symmetrical characteristics of the plastic zone at the crack tip, which means that the integrity of the welded structure containing the fatigue crack mainly depended on the toughness of the low strength zone.
L.H.Li1，Y.H.Zhang1，X.A.Zhang2，H.Y.Zhao3，H.Q.Zhang3
(1.School of Mechanical Engineering and Automation, Beijing University of Aeronautics and Astronautics,Beijing 100083, China;
2.Beijing Institute of Aeronautical Materials, Beijing 100095, China;
3.Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China)
Abstract:Fatigue crack growth behaviors in electron beam weldments of a nickel-base superalloy are studied. The objective of this paper is to discuss effects of the inhomogeneity of mechanical performance on fatigue crack growth (FCG) rate and crack path deviation (CPD). The base metal served in a turbine disk of aerospace engine was selected to fabricate bead-on-plate weldments by using electron beam welding. Some wedge-type opening loading specimens, notched in three different zone of weld metal, HAZ and base metal, were employed and performed fatigue crack growth tests at 650℃. The results show that the fatigue crack growth of electron beam welded joints is instable due to the influence of mechanical heterogeneities. Owing to the crack deviation at the weld metal and hcat-affected-zone (HAZ), the effective growth driving force at the tip of fatigue crack was reduced with the reduction of the effective stress intensity factor (SIF) which finally causes fatigue crack rate decrease. Fatigue crack was strongly affected by size and the symmetrical characteristics of the plastic zone at the crack tip, which means that the integrity of the welded structure containing the fatigue crack mainly depended on the toughness of the low strength zone.
Key words:fatigue crack growth; crack path deviation; electron beam weld-ing; inhomogeneity of mechanical performance;
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