text: NAVWEPS oo-8oT-80 
  OPERATING STRENGTH LIMITATIONS 
  
  of stress the plot of stress and strain is essen- 
  tially a straight line, i.e., the material in this 
  range is elastic. A stress applied in this range 
  incurs no permanent deformation and the ma- 
  terial returns to the original unstressed shape 
  when the stress is released. At higher values 
  of stress the plot of stress versus strain develops 
  a distinct curvature in the strain direction and 
  the material incurs disproportionate strains. 