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| A STUDY ON MECHANISM OF SURFACE DEFORMATION INDUCED BY STRESS CORROSION CRACKING |
| Zhang Baiwei; Li Shuqing (Institute of Metal Research; Academia Sinica; Shenyang) |
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Cite this article:
Zhang Baiwei; Li Shuqing (Institute of Metal Research; Academia Sinica; Shenyang). A STUDY ON MECHANISM OF SURFACE DEFORMATION INDUCED BY STRESS CORROSION CRACKING. Acta Metall Sin, 1982, 18(5): 612-658.
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Abstract Stress corrosion cracking (SCC) experiments were conducted with steel D6AC (σ_b=203.5 kgf/mm~2) and 24CrMnSiNi (σ_b=161kgf/mm~2) by dropping water onto the crack opening mouth. The phenomenon of surface deformation induced by SCC has been observed by means of optical and interference microscopes. It was shown that the surface deformation started at the tip of fatigue precrack, then stretched separately into two branches with an angle of 45° to tbe direction of crack propagation and finally turned to parallel to it. For steel D6AC, the width between two deformation bands distributed on both sides of crack propagating direction was narrower and two deformation bands stretched forward by joining together and separating apart alternately. However, for steel 24CrMnSiNi, the two deformation bands, the width between which was found to be wider, did not join together even after stretching forward a long distance. It can be seen from the interference photographs that the fringes were largely displaced at deformation bands, indicating that the surface deformation was mainly concentrated within the deformation bands. In contrast, the fringes corresponding to the area between two deformation bands maintained nearly parallel to each other. The optical microscope observation certified that this area was contracted along the thickness direction. The cracking paths on specimen surface were observed to extend mostly either along the deformation band on one side or the confluence of deformation bands on both sides. The mechanism of surface deformation was discussed. It is considered to be related with the tongue shape expansion of stress corrosion crack over the specimen thickness. Apparently, the uncracking thin surface layers of specimen were subjected to a shear deformation under the action of applied force, resulting in the observed phenomenon of surface deformation.
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Received: 18 May 1982
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