What type of holes does cold working primarily apply to?

Cold working primarily applies to fastener holes in metal components because the process involves mechanically deforming the material at room temperature to improve strength and fatigue resistance. Fastener holes are critical points in structures where bolts or screws are inserted, and cold working can enhance the properties of the material around these holes, helping to prevent issues like cracking or wear over time. The localized deformation improves the residual stress state around the fastener holes, which is essential in maintaining the integrity of the metal components during operation.

The choice indicating it applies to only structural holes is too limiting, as cold working can be beneficial for various holes in metal parts, not just those classified as structural. Similarly, while cold working can affect any hole in a metal part, the specific benefits and emphasis are most apparent with fastener holes due to their use in load-bearing applications. The option referring to holes in composite materials is not applicable, as cold working is primarily a technique used for metals rather than composite materials, which often require different processing techniques.