Maximum hardness increment

A straightforward estimate of the maximum hardness increment can be made in terms of the strain associated with mixing Br and Cl ions. The fractional difference in the interionic distances in KC1 vs. KBr is about five percent (Pauling, 1960). The elastic constants of the pure crystals are similar, and average values are Cu = 37.5 GPa, C12 = 6 GPa, and C44 = 5.6 GPa. On the glide plane (110) the appropriate shear constant is C = (Cu - C12)/2 = 15.8 GPa. The increment in hardness shown in Figure 9.5 is 14 GPa. This corresponds to a shear flow stress of about 2.3 GPa. which is about 17 percent of the shear modulus, or about C l2n. 

Heat-Stabilized Compressed Wood (Staypak). Pressures of 400-4000 psi are applied to the wood after it has been heated. Both heat and pressure plasticize wood. At 160 °C and 12% moisture content, the maximum plastic yield per increment of pressure occurs at 1100 psi. Pressures of 1500-2500 psi are required to yield a specific gravity of 1.3. Highly densified wood must be cooled in the press. Some strength properties, such as impact strength and hardness, are increased in direct proportion to the density. Staypak finds limited application for silverware handles and desk legs (6). 

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