Stress estimation method for machine structure and monitoring method for machine structure

A monitoring method for a machine structure, the machine structure including a rotary device that rotates in response to pressure from a fluid, the method monitoring a state of an evaluation target position provided in the rotary device of the machine structure during operation of the machine structure, the method comprising:

• a calculation step of calculating a relationship between the stress generated at the evaluation target position and a physical quantity including a sound pressure or vibration generated at a detection position located away from the rotary device during vibration of the machine structure;
• a determination step of determining a notification threshold value of the physical quantity during operation of the machine structure on the basis of the relationship calculated in the calculation step and allowable stress of the evaluation target position having been set;
• a detection step of detecting the physical quantity generated at the detection position during operation of the machine structure;
• and
• a notification step of notifying that the physical quantity detected in the detection step has exceeded the notification threshold value.