×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Hertz (Contact) Stress

Hertz (Contact) Stress

Hertz (Contact) Stress

(OP)
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

RE: Hertz (Contact) Stress

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

RE: Hertz (Contact) Stress

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

RE: Hertz (Contact) Stress

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.

RE: Hertz (Contact) Stress

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

RE: Hertz (Contact) Stress

(OP)
Thanks Lcubed. I appreciate your help

RE: Hertz (Contact) Stress

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

RE: Hertz (Contact) Stress

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.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources