Stress Concentration

 


Key Concepts:  Real structures may contain holes, fillets, corners, and sharp changes of section.  In these cases the standard approximations leading to the formulas for nominal
stress and strain underestimate the actual values of stress and strain.  Stress concentration factors (factors of "ignorance") may be used to obtain improved values for actual stress
and strain.



In a Nut Shell:  Structures undergoing tension, torsion, and/or bending frequently have
interconnecting parts using welds and/or fasteners.  Consequently, experimental techniques
are used to determine a stress concentration factor to account for a significant increase in
the level of stress at localized areas compared to the nominal stress.  The table below shows the general form to relate the “actual”  or maximum stress to the nominal or average stress.

                   

 

                  σmax  =  K σave

       

                          and

 

                  τmax  =  K τave

 

   where

 

       σmax  is the maximum axial or bending stress at the location of stress concentration

          τmax  is the maximum shear stress at the location of stress concentration

 

          σave   is the axial or bending stress calculated from the usual formulas from

                             solid mechanics such as

 

                  σave  =  P/A  for axial loading   

 

              σave  =  Mc/I  for bending loads

 

           τave   is the shearing stress calculated from the usual formulas from

                             solid mechanics such as

 

                 τave =  Tc/J   for torsional loading

 

 and        K  is the stress concentration factor determined from experimental data

                    in the form of charts

 

Click here for examples.

 



Return to Notes on Solid Mechanics

Copyright © 2019 Richard C. Coddington
All rights reserved.