Slip systems prismatic

Three independent slip systems are not sufficient for arbitrary deformations. For the hexagonal crystal, this is easily understood because shear deformation out of the common slip plane of the three systems is impossible. Therefore, other, more difficult, slip systems must be activated. Because real metals never show the ideal hexagonal structure, but possess either a stretched or a compressed unit cell (varying ratio <=/ ), it depends on the chemical element which other systems are activated. Table 6.3 gives a synopsis of the most important slip systems. The slip systems with the horizontal slip plane are called basal slip systems. If the slip planes are on the prism faces of the unit cell, they are called prismatic slip systems. The other slip systems are called pyramidal slip systems. 

Experimental data suggest that the displacive a-p transition may not strongly influence the dominant slip systems. This is not unexpected because the main basal and prismatic slip systems have hexagonal symmetry. However, textures are... 

Figure 6.2 (a) The hexagonal dose-packed structure of a-alumina. (b) Two important slip systems, basal (0001) [0001] and prismatic (0110)[2110], in a hexagonal structure. 

Early studies on BeO single crystals by Bentle and Miller [51] identified four slip systems basal slip, (0001)(1120) prismatic slip, 1100 (1120) and 1100 [0001] and pyramidal slip, Il22 (1123). Not surprisingly, significant plastic anisotropy was found. At 1000 °C, the yield stresses for these systems were as follows 35 MPa for basal slip 49 and llOMPa for prismatic slip along (1120) and [0001], respectively and >250 MPa for pyramidal slip. More recent studies on creep deformation in BeO... 

The plastic deformation of the sapphire occurred due to basal and prismatic slip during loading above T. Basal slip was found in A- and B-oriented specimens and prismatic slip in C-oriented specimens. The resolved stresses at yield (according to the author) are comparable to those measured by other researchers under compression in the appropriate slip system. 

Figure 3.27. Reciprocal mean effective resolved shear stress curves for Knoop indentation calculated for (a) (0001)(1120) and (b) 12l0 O0T0) slip systems on the prismatic (iTOO) plane of hexagonal crystals.

The basal plane in the hep metals Zn and Cd is the most densely packed plane and slip generally occurs in this plane and in the <1120> direction. Prismatic and pyramidal systems, in addition to the basal system, have been shown to operate at room and elevated temperatures, depending on the mode of deformation. The c/a ratio plays an important role in determining the ease with which other slip systems... 

Microactuators can be implemented in one or more degrees of freedom, leading to another way to classify them as linear (or prismatic), rotary (or revolute), in-plane (1D-3D), and out of plane (1D-6D). A micromotor contains several movable parts, including the microactuator and a transmission system. The transmission system consists of bending (or flexture) joints and links, rigid links, stick-and-slip contact elements, or micromechanical hinges. Like macroscale actuators, microactuators are chosen for different applications based on tradeoffs between ... 

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