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, R2 or 2:1) and/or real numbers (R = 0,7, R0,7 or 0,7:1). In some cases, the x value can be an approximation of the R-ratio.
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