Q2. What should be considered in piping and component design?
To adopt Mod.9Cr-1Mo steel, the individual failure mechanism (Type IV cracking) at the weld joints [6-8] should be considered in piping and component design.
Q3. What is the strain amplitude between the gauge grips?
Because the creep-fatigue test is performed by controlling the strain, the strain amplitude between the gauge grips is held constant during the holding period.
Q4. What is the important failure mode to prevent in the design?
On the other hand, with respect to failure mechanism of SFRs components, the most important failure mode to be prevented in the design is creep-fatigue.
Q5. What was the original value of q in the JSME FR code?
The elastic follow-up method was originally developed in Japan, and a value of q = 3 was defined in the code as a conservative value [4] [5].
Q6. Why was a procedure based on elastic FEA required?
Because inelastic FEA using a model with welding lines in the components was not practical in the components design, a procedure based on elastic FEA is required.
Q7. What is the evaluation method for creep-fatigue life?
Since a failure mode that originated in the HAZ was also recognized through creep-fatigue testing and the available data research, the authors have investigated the evaluation method of creep-fatigue life for the weld joints of Mod.9Cr-1Mo steel considering the HAZ.
Q8. Why was the strain amplitude in the gauge length monitored?
Because the creep-fatigue test was performed by controlling the strain amplitude, the total strain amplitude in the gauge length generated by the tension loading of the model end was monitored for each historical step in the FEA.
Q9. What is the value of qc in the equation for estimating the total strain range?
Under operating conditions with low primary stress, the equation for estimating the total strain range, εt, in the strain concentration region exhibiting elastic follow-up behavior in the JSME FRs13 / 36code is as follows:nt K ee e= , (3)where εn is the nominal strain range, and Kε is defined byeKKK ′=e , (4)wheremS3Sn > , and (5)( )( )nme SS311q1K −−+=′ . (6) In the equation (5) and (6), Sn is the nominal stress range, K is the stress concentration factor,and q = 3.
Q10. How was the specimen model used to simulate the creep-fatigue test?
To avoid the effect of boundary conditions on the stress-strain redistribution during creep relaxation, the entire specimen was modeled when simulating the creep-fatigue test.
Q11. What is the effect of the strain feedback technique on the strain distribution in the gauge length?
Without this strain feedback technique, strain amplitude within gauge length is changed by stress-strain redistribution due to creep behavior during the holding.
Q12. What is the reason for the overestimation of failure cycles in Fig.15?
The overestimation of failure cycles in Fig.15 is attributed to the fact that the estimated creep-fatigue test data were limited at 550 °C and the most of the data were obtained by the test11 / 36with 1.0 h or less holding, while there were each one data obtained with 3.0 h and 10.0 h holding.
Q13. How was the grain size of the hammer joint calculated?
Using optical microscopy, the grain size number (ASTM E 112) in the BM and HAZ of the original weld joint were estimated to be 8.0 and 10 to 12, respectively.