×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Are you an
Engineering professional?
Join Eng-Tips Forums!
• Talk With Other Members
• Be Notified Of Responses
• Keyword Search
Favorite Forums
• Automated Signatures
• Best Of All, It's Free!

*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.

# Combining Stresses2

 Forum Search FAQs Links MVPs

## Combining Stresses

(OP)
Hi All,

I need help calculating the combined stresses (max/critical stress) on the journal of a ball screw to determine FOS. I got the torsional stress and the axial stress (compression and tension), but I cannot remember how to combine them. I am trying to refresh on Mohr's circle from class over ten years ago, but admittedly it is throwing me for a loop. There is no bending stress or other shear stress, just pure axial and torsional, so it should be the same around the shaft circumference. Can anyone please help?

### RE: Combining Stresses

Research the Superposition method for combining stresses. Maybe that will refresh your memory.

### RE: Combining Stresses

(OP)
@ FACS, I may be mistaken but I believe that is in reference to adding shear stresses (shear load + torsional) together and normal stresses (axial, bending) together, but not for combing shear and normal to determine the maximum stress within a part.

### RE: Combining Stresses

(OP)
Thanks, desertfox. I actually was reading through that, specifically the helicopter example but I did not follow how they got the 103 MPa. I need to review this further but for now can get this part drawn up and made

### RE: Combining Stresses

I couldn't see "103 MPa" ... which example problem ? there seem to be lots directly applicable to your problem. You're right, that the outer surface is at the same stress level, but the combined stress, the principal stress is at an angle to the axial direction.

oh, I see it (on pg9) ...
maximum shear stress is (p1-p2)/2, the radius of mohr's circle; = (135--71)/2 = 103

another day in paradise, or is paradise one day closer ?

### RE: Combining Stresses

Hi USMechE6

The 103Mpa is the centre of the Mohr circle, or the radius arm if you like (171 + 105)/2

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

### RE: Combining Stresses

(OP)
Thank you all for the help.

#### 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.

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

Click Here to join Eng-Tips and talk with other members! Already a Member? Login

#### Resources

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a partâ€™s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

# Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

• Talk To Other Members
• Notification Of Responses To Questions
• Favorite Forums One Click Access
• Keyword Search Of All Posts, And More...

Register now while it's still free!