Peening apparatus and method of peening using the same

A peening apparatus for generating a compressive residual stress on a pipe member including at least one curved round portion and having a hollow inside formed therein in which a first fluid is accommodated on one side and a second fluid, which is in a gas phase, is accommodated on an other side, the apparatus comprising:

• a probe which is disposed such that it is submerged in the first fluid supplied to the hollow inside, and which is configured to apply a wave to the first fluid, and
• a power unit which is connected to the probe and the pipe member, and which is configured to rotate the probe and the pipe member together,
• wherein the first fluid and the second fluid have different acoustic impedances, so that the wave is totally reflected on a reflection surface where the first fluid and the second fluid are in contact, and forms a standing wave, wherein a cavity generated and grown in the a pressure antinode of the formed standing wave is exploded and emits a shock wave or microjet, which generates a compressive residual stress to an inner surface of the pipe member surrounding the hollow inside, and
• wherein as the probe and the pipe member are rotated together while keeping a pressure of the second fluid constant, a position of the reflection surface relative to the inner surface of the pipe member is adjusted while the angle between the reflection surface and the inner surface of the pipe member is maintained at a predetermined angle.