Question

CYCLIC STRESS Oyield = 55 ksi Oultimate = 72 ksi (ksi) 10 107 102 103 104 105 106 NUMBER OF CYCLES In solving this problem, one would usually draw the Soderberg line as shown below: Cyclic Stress A Soderberg line Steady Stress

For the plot shown above, what is the value of the cyclic stress at A? a) 35ksi b) 40ksi c) 45ksi d)30ksi

For the plot of the Soderberg line in Question 5, what is the value of the steady stress B? a) 55 ksi b) 72 ksi c) 35 ksi d)40 ksi

Please use the Soderberg line in the previous question to solve this problem. What is the maximum magnitude of an additional steady stress that can be put on top of the cyclic load without fracture during its design life, according to Soderberg's theory?

a) 15.7 ksi b) 39.3 ksi c)55 ksi d) 35 ksi

Answer 1

Soderberg diagram is the line joining the points (yield stress,0) on the steady stress axis and the (0, endurance limit of the material) on the cyclic stress axis

Any point on the steady stress axis has a constant stress value ( It doesn't vary with time).

Note Option for 25Ksi is not provided in the first question. The cyclic stress at A is endurance limit with zero steady stress(Mean stress)

At B the steady stress is the yield stress which is 55 ksi (Option a)

the maximum cyclic load that material can sustain without any fracture is the range of that cyclic load equals to endurance limit (25 ksi). any cyclic load with a range lesser than or equal to the endurance limit cannot induce any damage in the material. Hence option a (15.7 ksi) is correct one

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At B yield stress - 55ksi steady stress is option CA) According to Soderberg theory any combination of (steady stress, cyclic stocks) on the Soderberg line cannot Create a damage and also points below the Soderberg line cannot Create a damage - A cyclic stress more than endurance strength can only create a damage... sot To Create a damage Cyclic, stress should be to Gochter, ihan endurance limit - > e > 25 so option (A) 15.7 ksi boot