PSI - Issue 43

Jaroslav Polák et al. / Procedia Structural Integrity 43 (2023) 197–202 Jaroslav Polák, Alice Chlupová / Structural Integrity Procedia 00 (2022) 000 – 000

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Provided the normal component of the primary Burgers vector b G in the slip plane is oriented in the direction towards the grain boundary (Fig. 6a), the PSB lamella producing the surface extrusion also produces an extrusion on the grain boundary. The lamella producing surface intrusion produces also a grain boundary intrusion. This case corresponds to the detail of the grain boundary crack showing grain boundary extrusions and intrusions in Fig. 3 and Fig. 4. Present findings allow to propose a novel mechanism of the grain boundary crack initiation based on the weakening of grain boundary by void-like defects stemming from grain boundary intrusions and on the production of internal compression stresses by grain boundary extrusions acting as external tensile stress. Under the action of external stress, void-like defects link and grain boundary crack initiates. References Antolovich, S. D., Armstrong, R. W., 2014. Plastic strain localization in metals: origins and consequences. Prog. Mater. Sci. 59, 1-160. Boettner, R., C., McEvily, A. J., Liu Y. C., 1964. On the formation of fatigue cracks at twin boundaries. Philos. Mag. 10, 95-106. Essmann, U., Gosele, U., Mughrabi, H., 1981. A Model of Extrusions and Intrusions in Fatigued Metals. 1. Point Defect Production and the Growth of Extrusions. Philos. Mag. A. 44, 405-26. Figueroa, J. C., Laird, C. 1983. Crack initiation mechanisms in copper polycrystals cycled under constant strain amplitudes and in step tests. Mater. Sci. Eng. 60, 45-58. Heinz, A., Neumann, P., 1991 Fatigue Crack Initiation Due to Incompatibility Stresses at Grain-Boundaries. In: Brandon D. G., Chain, P., Rosen, A., (Eds) Strength of Metals and Alloys, Vol 1. Haifa1991. p. 11-29. Chlupová , A. , Šulák , I. , Babinský , T. , Polák , J., 2022. Intergranular fatigue crack initiation in polycrystalline copper. Mater. Sci. Eng. A, submitted for publication. Christ, H. J. 1989.. On the orientation of cyclic-slip-induced intergranular fatigue cracks in face-centered cubic metals. Materials Science and Engineering: A. 117, L25-L9. Kim, W.H., Laird, C. 1978. Crack Nucleation and Stage-I Propagation in High Strain Fatigue .1. Microscopic and Interferometric Observations. Acta Metallurgica. 26, 777-87. Liang, F. L., Laird, C. 1989. Control of intergranular fatigue cracking by slip homogeneity in copper I: Effect of grain size. Materials Science and Engineering A. 117, 95-102. Liu, W. B., Liu, Y., Sui, H. N., Chen, L. R., Yu, L., Yi, X., et al. 2020. Dislocation-grain boundary interaction in metallic materials: Competition between dislocation transmission and dislocation source activation. Journal of the Mechanics and Physics of Solids. 145, 18. Man, J., Valtr, M., Petrenec, M. , Dluhoš , J. , Kuběna , I. , Obrtlík , K., et al. 2015. AFM and SEM-FEG study on fundamental mechanisms leading to fatigue crack initiation. Int J Fatigue. 76, 11-8. Mazánová , V., Heczko, M. , Polák , J. 2022. On the mechanism of fatigue crack initiation in high-angle grain boundaries. Int J Fatigue. 158. 106721. Mughrabi, H. 1982. A model of high-cycle fatigue-crack initiation at grain boundaries by persistent slip bands. In: Sih G. C., Provan,J.W. (Ed.). Defects Fracture and Fatigue. Mont Gabriel, Canada: Martinus Nijhoff; 1982. p. 139. Polák , J., 1969. Electrical resistivity of cyclically deformed copper. Czech. J. Phys. 19, 315-22. Polák , J., 1987. On the role of point defects in fatigue crack initiation. Mater. Sci. Eng. 92, 71-80. Polák , J., Man, J. 2014. Mechanisms of extrusion and intrusion formation in fatigued crystalline materials. Materials Science and Engineering A. 596, 15-24. Polák . J. , Mazánová , V., Heczko, M. , Petráš , R. , Kuběna , I. Casalena L., et al. 2017. The role of extrusions and intrusions in fatigue crack initiation. Eng Fract Mech. 185:46-60. Polák , J. , Mazánová , V., Heczko, M. , Kuběna , I., Man, J. 2017. Profiles of persistent slip markings and internal structure of underlying persistent slip bands. Fatigue Fract Eng M. 40,1101-16. Tanaka, K., Mura, T. 1981. A Dislocation Model for Fatigue Crack Initiation. J Appl Mech-T Asme. 48, 97-103.