Corrugated cardboard box compressive strength test analysis

The compressive strength of a corrugated carton is the maximum load and the amount of deformation that occurs when the pressure tester uniformly applies dynamic pressure to the housing.

The compressive test process is divided into four stages: the first is the preloading stage to ensure that the carton is in contact with the press platen; the second is that the transverse pressure line is pressed down and the load is slightly increased at this time, and the deformation amount varies greatly; The third is the stage of pressure on the side wall of the carton. At this time, the load increases rapidly and the deformation increases slowly. Fourthly, when the carton is completely destroyed, it is the crushing point of the carton. Because in the entire pressure-bearing process of the carton, mainly the four corners are stressed, which accounts for about two-thirds of the total force, we should minimize the damage to the corrugations around the four corners of the carton during the production process.

The compressive strength of the carton is divided into effective and final values. The change of force during the compressive test is sometimes from slow to fast to the point of collapse, and some of it is gradually increased to the point of collapse. In the long-term compressive tests, we found that the change in the force value sometimes has a certain buffer: that is, when the force value and the deformation amount increase to a certain extent, the force value stops and the deformation amount continues to increase. After a period of time, the force value continues. Increase until the collapse of the carton. We can refer to the force value before buffering as the effective force value, and the deformation amount before buffering is called the effective deformation amount. After buffering, although the force value can continue to increase, but the carton has begun to deform, can not meet the requirements for use, so the standard for determining the compressive strength of the carton should be the effective value of the compressive test.

Generally, the deformation of the three-story A-case is below 10mm, the deformation of the three-story B-case is below 7mm, the deformation of the three-layer C-case is below 9mm, the deformation of the five-story BC is below 18mm, and the test force value should reach Effective compressive strength.

The better the quality of the carton, the higher the effective value of the compressive strength, and the smaller the deviation between the effective value and the final value. Analysis of the compressive strength of corrugated boxes is generally expressed by the average value of a set of multiple experiments (≥3). The smaller the deviation between each experimental data, the more stable the compression resistance of the carton. We can further analyze the quality of the carton through the process of changes in force and deformation, combined with various factors affecting the carton pressure resistance.
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Rapid Design of Compressive Strength of Corrugated Box 0201

China's corrugated carton packaging industry has made great progress in more than 20 years. The changes in recent years are even more rapid. Some sophisticated science and technology have been applied to the industry, but due to the late start, we used corrugated paper. Some of the box design processes are still used abroad, especially the calculation method of the compressive strength of the corrugated box empty box. The foreign formulas are too cumbersome and difficult to understand. It is difficult to combine the price design of domestic cartons with the design of the compressive strength of empty containers. This can easily lead to the waste of raw materials or the quality problems in the compression resistance of cartons.

To compensate for these deficiencies and enhance the predictability of compressive strength before carton production, after a long period of measurement and verification, I have found a simple and effective method for calculating the compressive strength of empty carton boxes using the physical properties of the base paper. The formula for calculating the compressive strength of the box is written and discussed with everyone. This article only discusses the design of the 0201 type three-layer corrugated cardboard box compressive strength in this method.

The corrugated carton consists of various layers of corrugated paper. The formula for calculating the compressive strength of corrugated cartons is based on the physical properties of the original paper to calculate the compressive strength of the carton to see if it meets the requirements. It may also be based on the compressive strength requirements of the corrugated box. Select the appropriate corrugated paper.

P=Px·K
P - the empty box compressive strength of corrugated boxes (units N)
Px - transverse composite ring crush strength of base paper (units N/Cm)

Three-layer corrugated board raw paper composite ring crush strength = (paper ring pressure value R1 + paper ring pressure R2 + paper ring pressure R3 x corrugation shrink rate C) / 15.2

The ring pressure value in this paper refers to the horizontal ring pressure value (unit: N/0.152m), which can be obtained through testing, or can be calculated according to the level of the base paper and the ring pressure index.

Ring pressure value R = quantitative W (units g/m2) × ring pressure index R (units Nm/g) × 0.152 (units m). There are some differences between the test value and the calculated value of the same kind of paper ring pressure value, and the general test value is larger than the calculated value. This is because the internal control standards of each paper mill are higher than the national standard, and both data can be used for compressive strength. The calculation.

K - The effective value of the integrated ring pressure in the compressive strength of the empty carton. The formula is:

Three layers A楞K=30.3+0.275Z-0.0005Z2
Three layers C楞K=27.9+0.265Z-0.0005Z2
Three layers B楞K=24.6+0.235Z-0.0005Z2

The product of the combined ring crush strength and its effective value in the carton is the compressive strength of the carton. C represents the shrinkage rate, the shrinkage ratio of A楞C=1.532, the shrinkage ratio of B楞C=1.361, and the shrinkage ratio of C楞=1.477. Z represents the perimeter of the carton (ranging from 70 Cm to 200 Cm).

(to be continued)