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7.43 A non-cold-worked brass specimen of average grain size 0.008 mm has a yield strength of 160 MPa (23,500 psi). Estimate the yield strength of this alloy after it has been heated to 600°C for 1000 s, if it is known that the value of ky is 12.0 MPa-mm1/2 (1740 psi-mm1/2).

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Answer: 52.6Mpa(7940) psi

Explanation:

Step 1, We calculate the constant (sigma zero)

6o = 6y - ky6^1/2 (6 represents sigma symbol)

= 160Mpa - (12.0Mpa-mm^1/2)(0.008mm^-1/2)

= 25.8Mpa(4046psi)

Step 2. At 700oC and 1000s which is 16.7mins, the average grain material is 0.02mm. The yield strength for the new grain size is therefore

6y = 6o + ky6^-1/2 (6 represents sigma symbol)

= 25.6Mpa + (12.0Mpa-mm^1/2)(0.70mm) ^-1/2

= 52.6Mpa(7940)psi

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