Question

A rotating circular shaft, machined from AISI 1095 Q&T steel, is

subjected to a torque that varies from a value of 200 N.m to 400 N.m

and to a fluctuating bending moment that varies from a value of -100

N.m to 300 N.m. Also an axial tensile force of 5 kN acts on the element.

The torque and the bending moments have their peak values at the

same time and their frequencies are same. Find the factor of safety of

the element for an infinite operation life assuming the reliability as 0.999.

Use Modified Goodman Diagram (Material Properties; Sut = 1260 MPa,

Sy=813 MPa).

A rotating circular shaft, machined from AISI 1095 Q&T steel, is subjected to a torque that varies from a value of 200 N.m to 400 N.m and to a fluctuating bending moment that varies from a value of -100 N.m to 300 N.m. Also an axial tensile force of 5 kN acts on the element. The torque and the bending moments have their peak values at the same time and their frequencies are same. Find the factor of safety of the element for an infinité operation life assuming the reliability as 0.999 Use Modified Goodman Diagram (Material Properties; Sut 1260 MPa, Sy-813 MPa) dl d2

Answer 1

There is a combined loading in this problem. The load factor and stress concentration factor differs according to the type of loading. Therefore, they will used as load modifying factors instead of endurance limit modifying factors. They will be used for modifying the alternating components of the stresses (The critical section is at the fillet). For the material: Geometric properties: Axial loading Axial load is constant, it will only create mean stress. Bending moment: bending moment is fluctuating