| 摘要 |
PROBLEM TO BE SOLVED: To carryout a work hardening of a surface to be processed and to enhance a fatigue strength by generating a cavitation around a jet stream and applying a cavitation bubble to a workpiece. SOLUTION: After a workpiece W is placed in a first container 1, the container 1 is closed by an openable/closable cap 2 and a high pressure water is sprayed from a nozzle 4. A cavitation 9 is generated around a jet stream and a cavitation bubble is applied to the workpiece W. A collapse impact force of the cavitation bubble is applied to a surface to be machined and a work hardening of the surface to be machined, an improvement of a residual stress and an enhancement of a fatigue strength are brought. In order to increase the collapse impact force of the cavitation bubble 9, a flow rate of a pressure water flowing from a nozzle 4 into the first container 1 is controlled by a flow rate control valve 6 and a flow rate thereof flowing out from the first container 1 is controlled by a pressure control valve 8, thereby a liquid pressure in the first container 1 is controlled.
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