A hole is drilled at the wrong place on a beam web subject to high cycle fatigue in a non-corrosive environment. Assume that the hole is far away from any end connection and has a theoretical stress concentration factor that give a notch fatigue factor of 1.4. Which of the following actions will yield the highest fatigue strength: Fill the hole with welding, deburr the weld toe and peen. Leave the hole as it is.

The action that will yield the highest fatigue strength is to leave the hole as it is.

Here's why:

1. Filling the hole with welding can introduce additional stress concentrations, especially if the welding process is not done perfectly. This can lead to the formation of micro-cracks which can propagate under high cycle fatigue loading, reducing the fatigue strength.

2. Deburring the weld toe can help to reduce stress concentrations, but it is not a guarantee that all stress risers will be eliminated.

3. Peening is a process that introduces compressive residual stresses into the material, which can help to increase fatigue strength. However, the effectiveness of peening can be limited if the initial stress concentration (due to the hole and the welding) is high.

4. Leaving the hole as it is does not introduce any additional stress concentrations. The theoretical stress concentration factor that gives a notch fatigue factor of 1.4 is already accounted for in the design. Therefore, if the hole is far away from any end connection (as stated in the question), the stress concentration due to the hole will not significantly reduce the fatigue strength of the beam.

Therefore, leaving the hole as it is will yield the highest fatigue strength.