### Definition(s)

#### R-ratio

ratio of the hoop stress to the axial stress in a particular test condition

- EXAMPLE: In a hydrostatic test condition where a) the test sample is unrestrained, b) the hoop stress component is represented by half the pressure times diameter divided by wall thickness (
*PD/2t*) and c) the axial stress component is represented by one-fourth the pressure times diameter divided by wall thickness (*PD/4t*), the R-ratio would be exactly 2,0. In the same test condition, if the axial stress component is represented by force over area (*F/A*) instead of*PD/4t*, the*R*-ratio will most likely be slightly higher than 2,0.- Note: 1 to entry: Data points on the
**long term envelope**(3.2.70),**threshold envelope**(3.2.117) and**design envelope**(3.2.15) can be referred to as*R = x*or*Rx*or*x:y*data points where x and*y*are integers (e.g.*R = 2*,*R*2 or 2:1) and/or real numbers (*R*= 0,7,*R*0,7 or 0,7:1). In some cases, the*x*value can be an approximation of the R-ratio.

- Note: 1 to entry: Data points on the

*Source: ISO 14692-1:2017, Petroleum and natural gas industries — Glass-reinforced plastics (GRP) piping — Part 1: Vocabulary, symbols, applications and materials, Second Edition, August 2017. **Global Standards*