Giga Pascal

Pressure is usually expressed in bars, atmospheres, or pascals. One bar = 0.9868atmosphere = 10s pascals. One megabar = I06 bars = 100 GPa (giga pascals). 

In the following sections we assume that the application of pressure is non-directed, i.e. hydrostatic or quasi-hydrostatic (see below). The usual unit of pressure is the Giga-Pascal GPa (lPa=lNm ), but older literature often refers to kbar (1 kbar = 0.1 GPa). 

High-pressure viscosity measurements can also be of considerable practical importance. For example, in the field of lubrication it has been recognized for some time that the fluid in a lubricated contact can experience several giga-pascals of pressure. Theory predicts that the derivative of viscosity with respect to pressure is a critical parameter in determining the metal-metal contact and thus the wear in such a system. However, this derivative is itself a strong function of pressure, and a more accurate estimate of viscosity effects is gained by experimentally determining the entire pressure-viscosity curve up to the actual pressures of operation. 

G shear modulus (modulus of rigidity) GPa giga Pascal... 

A.F. Goncharov, V.V. Struzhkin, M.S. Somayazulu, RJ. Hemley and H.K. Mao (1996) Science, vol. 273, p. 218 - An article entitled Compression of ice at 210 giga-pascals Infrared evidence for a symmetric hydrogen-bonded phase . 

When considering tests, one is at once confronted with units. It is my feeling that most readers will probably be more comfortable with the more familiar units, such as pounds per square inch, than with giga newtons per square meter or giga pascals. I plan to include a short table at the end of this chapter, and those who have a compulsion to remain up to the minute in all their calculations may feel free to use any units they choose. 

P.,A. and Saeger, R.,B., "Examining the Rheology of 9-octylheptadecane to Giga-Pascal Pressures." Journal of Chemical Physics Volume 114(4) p. 1887-1891 (2001)... 

The important point is that the magnitude of a stress is always equal to the magnitude of a force divided by the area of the face on which it acts. Forces are measured in newtons, so stresses are measured in units of newtons per metre squared (N m" ). For many engineering applications, this is inconveniently small, and the normal unit of stress is the mega newton per metre squared or mega(lO ) pascal (MN m or MPa) or even the giga(10 )newtons per metre squared or gigapascal (GN m or GPa). 

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