Tensile Strength of Liquids

Tensile strength and liquids do not seem to combine easily. They do however. Liquids can exist in metastable states if there is an energy barrier to the formation of droplets of a second phase in a homogeneous metastable parent phase. The nucleation of the phase transition is assumed to be accomplished by the thermal activation of incipient droplets of the second phase over top the top of this barrier. One avenue to increase the probability to overcome the barrier is to heat (superheat) the liquid. Such rapid superheatings were published in Physical Review B for liquid helium-3.
The tensile strength of water has been subject to measurement for over 150 years. Not unexpectedly, it turns out that it has an important consequence in nature: the height of trees is determined by the fact that water can sustain a tensile strength. Was this not the case, trees would not exceed about 10 m in height. The tensile strength also plays a role in dispersal of spores of certain ferns.
The first measurement of the tensile strength of liquid helium was measured in this laboratory after many fruitless attempts by many other researchers. The obstacle to overcome is heterogeneous nucleation of the vapor phase. Many causes contribute to the heterogeneous nucleation, such as: formation of the vapor phase at a surface, nucleation induced by cosmic rays, and nucleation due to the presence of foreign gases dissolved in the liquid.
The approach developed by us determined the tensile strength of a liquid was as follows. The cavitation limit was reached by focusing a short burst of ultrasound into a small volume of helium and detecting the onset of cavitation by the scattering of laser light. The first presentation was at the Cryogenic Engineering Conference in 1987 and published in the proceedings.
Subsequent papers were published in Physical Review B and J. Applied Physics. In another paper, the tensile strength of nitrogen was measured.
A cute review without the reference to the truly first, pioneering, original, and correct experiment at negative pressures in liquids and liquid helium in particular is: http://www.aip.org/pt/feb00/maris.htm
Portland State University - Physics Department
February 28, 2002