A dilatant material is one in which viscosity increases with the rate of shear (also termed Shear thickening). The classic example is Silly Putty, which can be stretched slowly but snaps and fractures if pulled quickly. The dilatant effect can be seen more readily with a mixture of corn starch and water, which acts in counter-intuitive ways when struck or thrown against a surface.
Industrial uses
Dilatant materials have certain industrial uses due to their shear thickening behavior. For example, some all wheel drive systems use a torque converter full of dilatant fluid to provide power transfer between front and rear wheels. On high traction pavement, the relative motion between primary and secondary drive wheels is the same, so the shear is low and little power is transferred. When the primary drive wheels start to slip, the shear increases, causing the fluid to thicken. As the fluid thickens, the torque transferred to the secondary drive wheels increases proportionally, until the maximum amount of power possible in the fully thickened state is transferred. See also: limited slip differential, some types of which operate on the same principle.
To the operator, this system is entirely passive, engaging all four wheels to drive when needed, and dropping back to two wheel drive once the need has passed. This system is generally used for on-road vehicles rather than off-road vehicles, since the maximum viscocity of the dilatant fluid determines the maximum amount of torque that can be passed across the coupling.
The opposite of a dilatant material is a Pseudo-plastic.
The balloon dilation technique for treating phimosis in boys includes a balloon catheter, an inflator, a valve clip and two curved retractors, which are all made of disposable plastics.
Balloon dilation treatment is indicated for boy patients with a constricted preputial orifice impeding retraction of the prepuce over the glans penis and/or a history of either urinary tract infection, frequent micturition or bradyuria due to phimosis before the age of three years.
Dilation of the prepuce should be terminated if the balloon waist disappears or when the balloon diameter is 3-5mm greater than that of glans penis.
Dilational lineaments are part of a larger array of Europan lineae which crisscross the satellite, discovered by the Voyager spacecraft (Smith et al., 1979; Lucchitta and Soderblom, 1982), and viewed at higher resolution by the Galileo spacecraft (Belton et al., 1996; Greeley et al., 1998; Greenberg et al., 1998a).
Dilation may accompany ridge formation when ice or slush accumulates in the cracks, forcing the opposing blocks apart when daily compressive tidal stress is applied, according to Greenberg et al.
Because external pulling counteracts tidal compression, the relative importance of the two end-member processes determines the morphology of Europan dilational lineaments, by controlling the degree of elevation, and the prominence of a central groove and of bilateral symmetry.
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