Tek-Tips is the largest IT community on the Internet today!

Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!

Register Log in
  • Congratulations TugboatEng on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Allowable Stresses

Status
Not open for further replies.
manian

manian

Industrial
Joined
Sep 9, 1999
Messages
42
Location
AE
How to fix the allowable stresse for the following stress conditions, for mechanical equipment and pressure vessel ? The basis has to be realistic based on research findings since we cannot assume high factors of safety.<br>
<br>
Tensile Loading<br>
Compressiver Loading<br>
Shear Loading - Direct Shear<br>
- Torsional Shear<br>
- Thread Shear<br>
Contact Stresses - Surface Contact - Flat to Flat<br>
- Point Contact - Ball to Flat<br>
- Rolling Contact - Flat to Flat<br>
It does not seem to be prudent to take the allowable stresses as per ASME for non-pressure containing members where only a pure mechanical load can be expected.<br>
The allowable stresses recommended by the other texts seem to be too conservative/unrealistic. Hence a rational approach is desired. Will be thankful if some one could throw more light on this subject in detail.
 
Sort by date Sort by votes
Conservative design will account for things that are often "taken for granted" like corrosion, wear, fracture properties, overloading, excessive vibration, etc. If you can control these variables, you can justify a reduction in safety factor and use existing theory. Uncertianty regarding material properties, assumptions for stress estimation and effects of combined stress can be mitigated using more accurate analysis techniques like finite element and actual lab testing. <br>
<br>
Contact ASTM, ASME, NASA and various universities to see if they have literature available that describes your loading and materials sufficiently to allow for safety factor reduction.
 
Upvote 0 Downvote
MikeVV is correct. Additionally, you will have to increase the inspection of your material for manufacturing flaws and add stress concentration factors for flaws that may escape detection. ASME, based on code dictated inspections, accounts for flaws that may have escaped detection. The unrealistic limits on allowable stress are there to simplify design and material costs. <p>Tom Worthington<br><a href=mailto:pworthi@astro.as.utexas.edu>pworthi@astro.as.utexas.edu</a><br><a href= > </a><br>
 
Upvote 0 Downvote
Status
Not open for further replies.

Similar threads

amarks
  • Locked
  • Question Question
Stresses on wire rope drum
Replies
11
Views
2K
amarks
amarks
jda2354
  • Locked
  • Question Question
Industry standard thread shear allowable stress?
Replies
2
Views
487
SWComposites
SWComposites
Kristina Sornikova
  • Locked
  • Question Question
Unsymmetric Section Neural Axis Vs Principal Axes Maximum and Minimum Stresses
2 3
Replies
45
Views
2K
Stress_Eng
Stress_Eng
vgengineer66
  • Locked
  • Question Question
combined stresses on pipe clamp
2
Replies
34
Views
2K
LittleInch
LittleInch
FiniteMatt
  • Locked
  • Question Question
Any resources on allowable stresses or other design methods for attaching metal to stone?
Replies
11
Views
543
Peedge
Peedge

Part and Inventory Search

Sponsor

Back
Top