Hertz (Contact) Stress

[Cmfg]

I am designing the roller wheels for a bulkhead. By geometrical limitations the resultant hertz stress is 294 ksi. I am using Cast steel of fy=115 ksi. So the ratio is hertz/fy=2.6.

Where could I find an allowable Hertz stress (static loads)?
Hertz stress= ??? x fy

 

[Lcubed]

Theoretically, maximum Hz stress to avoid permanent deformation is about 1.81 times tensile yield. Reference Maleev and Hartman, Machine Design, 3rd Ed., page 121

 

[diamondjim]

Lcubed,
Is is Tensile or Yield?
My guess is it is 1.81 time
ultimate tensile strength.

 

[Lcubed]

Most materials exhibit a tensile yield strength and a compressive yield strength. It is 1.81 times the tensile yield strength. The tensile breaking strength is usually called the ultimate tensile strength, but I recognize that it is also called 'tensile strength', so I should have been more clear. Hope that helps.

 

[arto]

ASME B&PV Code uses 1.6xS {design allowable} for Bearing stress

 

[Cmfg]

Thanks Lcubed. I appreciate your help

 

[boo1]

Design of Machine Elements, by Spotts lists max compressive stress as a function of the Modulus of Elasticity.
For cylinders:
Po=0.591*[Sqrt(P1*E1*E2/R*(E1+E2))] Fig 9-9 pp443

 

[pdybeck]

consider hardening the surface of your material to improve wear life. Ion nitriding may be cost effective for you and significantly increase surface harndess. There are other processes you could use as well.