To perform a ring pressure test, insert a sample of specific dimensions into a circular tray so that the sides of the sample form a circular ring. Place the tray on the compression plate of the testing machine and apply electric constant pressure until the sample is crushed. The force recorded at the point of failure represents the ring compressive strength. The standard size for the sample should be 152 mm (longitudinal) with a tolerance of ±0.2 mm, and 12.7 mm (width) with a tolerance of ±0.1 mm. A total of 10 samples are required for testing: 5 samples are placed with their outer face outward in the tray, while the other 5 are placed with the inner side facing out. Each group is tested separately, and the results are averaged to obtain a consistent value.
To ensure accurate measurements, it's crucial to carefully examine the quantitative indicators, as they directly affect the conversion of the ring pressure index. The test samples must be representative of the material being tested. It is recommended to select 10 samples from different lateral sections of the paper tube to ensure consistency and accuracy. If only 10 samples are taken from a single longitudinal section, the results may not be reliable, as lateral thickness variations are typically greater than longitudinal ones. Proper calibration of the testing equipment, including the ring pressure tester and carton compression machine, is essential. Accurate measurement of the sample thickness is also critical, as differences in thickness can affect the diameter of the core used in the test. Therefore, multiple thickness readings should be taken, and an average value should be used for final evaluation. Ensuring uniform placement of the sample in the tray helps maintain consistent force distribution during the test.
The selection of the appropriate tray size (diameter) depends on the thickness of the sample. The tightness and quality of the base paper significantly influence the ring pressure strength. A paper with higher ring pressure strength will have a correspondingly higher ring pressure index. Before determining the ring pressure index, the ring compressive strength must be measured accurately.
Here are the formulas used to calculate ring pressure strength and ring pressure index:
1. **Ring Compression Strength**:
$ R = \frac{F}{152} $
Where:
- $ R $ is the ring compressive strength, in kN/m.
- $ F $ is the force applied when the sample breaks, in Newtons (N).
- 152 is the length of the sample, in millimeters (mm).
2. **Ring Pressure Index**:
$ Rd = \frac{1000R}{W} $
Where:
- $ Rd $ is the ring pressure index, in Nm/g.
- $ R $ is the ring compressive strength, in kN/m.
- $ W $ is the grammage of the sample, in grams per square meter (g/m²).
By following these procedures and using the correct formulas, you can ensure accurate and reliable results in your ring pressure testing.
Kids Adjustable Table
Shaoxing contuo Transmission Technology Co.,Ltd , https://www.contuodesk.com