Ian has found two small errors in Chapter 18. The first is tthat The underscores were left out in the call to Appendix A in the initialisation cell. This should read "AppendixAUseful_functions.nb". The second is that the call to the stressStrain function in the Post processing section should be replaced with

strains = SolidMechanicsStrain[vars, pars, displacement]; stresses = 
 SolidMechanicsStress[vars, pars, strains]; vmStress = 
 VonMisesStress[vars, pars, stresses];

My apologies.

-- you have earned Featured Contributor Badge Your exceptional post has been selected for our editorial columns Staff Picks http://wolfr.am/StaffPicks and Publication Materials https://wolfr.am/PubMat and Your Profile is now distinguished by a Featured Contributor Badge and is displayed on the Featured Contributor Board. Thank you!