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Application of Cold Expansion on Different Materials: A Review
T. Damla, M. B. Toparlı and P. Demırcıoglu

Cold expansion or cold-hole expansion is one of the mechanical surface treatment methods applied to circular holes of engineering structures for improved service performance. The main mechanism is to induce nonhomogenous plastic deformation by oversized mandrels or balls leading to beneficial compressive residual stress fields and hardness increase around the applied holes. Cold expansion is an important method to enhance fatigue life of particularly lightweight materials and components in aviation industry. In addition, to aluminium and titanium alloys, different materials such as steels were also treated via cold expansion for fatigue life improvement. In this paper, characteristics of different methods used in cold expansion were introduced/reviewed in detail. In addition, the review was presented according to application of cold expansion to different materials. Readers can navigate to materials of interest and find previous studies conducted on the same and/or similar materials. Therefore, this review shows a new direction along with an established process that has not been investigated before.

Keywords: Cold expansion, hole edge expansion, direct mandrel expansion, ball expansion, split sleeve expansion, residual stress, fatigue

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