

















\ 















Pj,= 11,250 PSI 





^. - 







_ 



. 





1 





^. 



^ EQUATION [3] | 









\ 





















\ 



.^EQUATION [l] 















"^ 



\ 



STRESS INTENSITY <T: , KSI 



Figure 21 - Graphical Determination of Inelastic General- 

 Instability Pressure for Model OV-4 



criterion together with the two membrane stresses given by Equations 

 [2] to be: 



(Ti = n/ct^ + ,r^ - cr cr^ = J {K^)^ + {K^)^ - {K^){K^) p [3] 



where Kj and K2 are functions of geometry and are given by EqiJ^ations 

 [2]. 



The inelastic general-instability pressures p^, for the titanium 

 models were determined as follows: Values of Eg and E^ were deter- 

 mined as a function of ctj^ by using the stress -strain curves obtained from 

 the uniaxial compression tests. Then p^, was plotted as a function of cr^ 

 using Equation [1]. Similarly, the applied pressure p was plotted against 

 cr- using Equation [3]. The inelastic general-instability pressure for each 

 model was then obtained from the intersection of the two curves of p^, 

 versus cr- and p versus o-^, as shown in Figure 21 for Model OV-4. The 

 inelastic general-instability pressures thus obtained are listed in Table 2; 



31 



