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**Figure 10.** Cone penetration vs yield stress for various greases.

Figure 11 shows a plot of cone penetration (CP) vs. crossover stress (CS), where the correlation is significantly better than in any of the preceding plots. In this case, the LiC3 grease fits in exactly where it would be expected and no grease deviates significantly from the overall trend. These data are fitted to a power law in Figure 12, where the coefficient of determination is above 0.95. Because of the good fit for all types of greases tested, it appears that using a rheometer to measure crossover stress could be used as a reasonable substitute for the cone penetration test.
