The frequent occurrence of cracks in the turbine blades poses a significant threat to the safe operation of the unit and causes tremendous economic losses to the power plant. Therefore, analyzing the causes of crack formation and performing non-destructive testing on areas prone to cracking are essential for timely defect handling and eliminating potential accident hazards.
The cause of crack formation is stress concentration. Through finite element analysis, it has been determined that under the effects of water pressure and centrifugal force, the high-stress zones mainly concentrate on the periphery of the turbine blades. The equivalent stress distribution along the blade perimeter is calculated according to the third strength theory. Generally, there are four high-stress areas on the turbine blades:
1. The leading edge's front side (pressure distribution surface) near the upper crown.
2. The middle part of the trailing edge's front side.
3. The trailing edge's backside near the upper crown.
4. The region where the blade connects with the lower ring.