Average values of the test constants for 7075-T6 alloy per Paris equation at various values of R ranging between 0 to 0.8 the values of C changes from 5.5x10(-21) to 6.8x10(-20). n value for 7075-T6 is 3.21.

Dear Arun

I saw some other value.

C: 2.7e-11 to 6.85e-8

n: 3.21 to 3.7

I don't know that what is the correct value...

http://www.afgrow.net/applications/DTDHandbook/examples/page2_2.aspx#figuremerc3_1

https://books.google.com/books?id=B2aAPVa1TloC&pg=PA150&lpg=PA150&dq=7075+t6+aluminum+properties%2Bparis+parameters&source=bl&ots=Axfts0obwv&sig=ZBIXf7pg3Sbn0o_yAhx6nruNxMk&hl=en&sa=X&ved=0CEsQ6AEwBmoVChMI6dXtif_cxwIVyBMaCh0aHAA_#v=onepage&q=7075%20t6%20aluminum%20properties%2Bparis%20parameters&f=false

https://books.google.com/books?id=0yrwBQAAQBAJ&pg=PA11&lpg=PA11&dq=7075+t6+aluminum+properties%2Bparis+parameters&source=bl&ots=RQwCnMzGq4&sig=fV9HbcxPWc2JJRKpzsc306daQa4&hl=en&sa=X&ved=0CF4Q6AEwCTgKahUKEwi8m8eU_9zHAhXMDxoKHS1VAmI#v=onepage&q=7075%20t6%20aluminum%20properties%2Bparis%20parameters&f=false

The values I quoted, they were from the extensive elaborate srudies done at NASA.

Your answer is correct but some of the papers used those values.

It is most certainly depended on how the sample is prepared and polished. The methods are well cited by NIST.