The material properties of a machine part are Sut 5 85 kpsi, f 5 0.86, and a fully corrected endurance limit of Se 5 45 kpsi. The part is to be cycled at sa 5 35 kpsi and sm 5 30 kpsi for 12 (103 ) cycles. Using the Gerber criterion, estimate the new endurance limit after cycling

according to Miners method the new endurance limit S" is 45 kpsi

Explanation:

Given the data in the question;

the amplitude stress σₐ = 35 kpsi

the mean stress for 12(10³) cycles σ = 30 kpsi

the ultimate tensile stress S = 85 kpsi

endurance limit of S = 45 kpsi

so, we calculate the reversing stress for Gerber criteria

σ = σₐ / [ 1 - ( σ/S)²

we substitute

σ = 35 / [ 1 - ( 30/85)²]

σ = 35 / [ 1 - 0.124567]

σ = 35 / 0.875433

σ = 39.98 kpsi

Using Miners Method;

the reversing stress ( 39.98 kpsi ) is less than endurance limit ( 45 kpsi )

σ  < S

According to Miners method, if reversing stress is less than endurance limit, then the endurance limit has not reduced and new endurance limit remains the same.

Hence, according to Miners method the new endurance limit S" is 45 kpsi

unlike the threaded fasteners which are used to clamp the machine members, power screws are used to transmit power. common applications of power screws are: screw jacks: to lift weight. lead screw of lathe: for axial movement of tool and its precise positioning.