Determination of Stiffness of Single-coated Whiteboard with a Self-made Simple Stiffness Meter (below)

March 31, 2019

Under the plywood, struts, floor plate overlap height 246;
The base is placed horizontally with its short sides on the left and right sides of the producer;
The length direction of the side panel is the same as the length direction of the base, and it is fastened to the edge of the base farther from the maker;
On the base, draw a vertical line 80mm from the short side of the left side of the base, draw a parallel line from the side panel 265mm, the intersection of the two lines is the installation center of the support rod, and the baseboard is bolted to the base;
At this time when the base is placed on a horizontal surface, the upper surface of the lower clamp should be horizontal, otherwise it should be adjusted to level. The direction of the lower plate should be perpendicular to the side panel, and the free end of the lower plate can be 21mm away from the side panel;
When the lower splint is horizontal, a circular spirit gauge is glued into the vicinity of the footing board so that the air bubble is exactly in the center of the bubble-shaped circle;
The scale plate is rod-shaped and is perpendicular to the base and floats on the base. The scale plate can slide along the base and the side panel and can be placed in any accessible position on the base.
Along the upper surface of the lower plate, a horizontal line is drawn on the scale plate 100mm in length;
Connect the points on both sides of the 0.2mm mark on the steel ruler to the horizontal line on the scale plate. The readings are from top to bottom and fixed with glue;
On the upper surface of the lower splint, draw a straight line parallel to the long side of the lower splint with a steel needle at a distance of 5 mm from the left long side. This line is the end of the sample;
On the upper surface of the lower plate, a straight line 30mm away from the long side on the left is parallel to the long side of the lower plate. This line is the edge line of the fixed iron clamp sample;
A large office document iron clip is placed on the base for use.

If a supervisor looks at the above text, he may not use the pen to draw a pattern on the paper. This is actually not difficult at all.
This example also illustrates how important the drawings and graphics are for people's correct understanding of the designer's intentions.

Determination of the stiffness expressed in terms of deflection:
1. Cut 10 pieces of 200*100 (horizontal size*longitudinal size) cardboard samples, including 5 pieces of positive side and 5 pieces of negative side. The sample shall be flat and wrinkle-free; the quality of each sample shall be weighed and multiplied by its value. 100/2 is both the quantification of the sample;
2. Adjust the instrument level;
3. Take a sample and place the short side on the lower plate. The short side of the sample in contact with the lower splint coincides with the stop line; the sample is clamped on the lower plate with a clamp; the edge of the clamp coincides with the edge line;
4. Let the free end of the cardboard hang down naturally. The free end of the specimen hangs from the moving scale plate (3~5)mm. The value of reading the lowest point level on the scale and the free end is both deflection and accuracy of 1mm; Place the other short side of the specimen on the plywood and do the same test. Take the average number of data obtained twice as the flexural value of the specimen. The test speed is as fast as possible to prevent the cardboard from being "irreversibly" deformed. ;
5. Report the maximum, minimum, and average values ​​of lateral deflection of the front and back of the sample, respectively. The average value of the deflection of one surface with a large numerical value was used as a test result.
6. Convert the deflection value to the stiffness value according to the "Quantity - Deflection - Stiffness Control Conversion Table". It is also possible to use the deflection value approved by the user as the standard value of the sample, and the judgement that exceeds this standard value is unqualified.
Another: The lower plate can be placed at the same time two samples for the stiffness of the two samples compared, obvious and intuitive.

The preparation of a quantitative-deflection-stiffness table (those who have not had the opportunity to use a standard stiffness instrument will not be able to compile this table):
According to the above method, the sample after deflection has been tested and then cut into 5 pieces of the front and back of a 70*38 cardboard sample. The stiffness is tested with a standard Taber stiffness tester. Each time (tens of times Several hundred sets of test data records were compiled and made into a "quantitative-deflection-stiffness control conversion table (or control curve)" for subsequent measurement.

postscript:
Thanks to the free and open network, it does not have many limitations, and it is possible to announce non-standard test methods worldwide.
The accuracy and reproducibility of the stiffness tester produced by the author even more than the instrument is good.
The instrument is suitable for internal use of the enterprise, and can also be used as a teaching aid for papermaking institutions. As to whether it can be used for arbitration determination, it is also necessary to standardize the theoretical research workers of workers, materials, and paper product testing, paper board producers, and paperboard users. This can not be accomplished overnight.
Time hastily. This article has not been carefully checked. Please forgive me if you have not reviewed it by a prominent person.

The author's next similar article may be “Testing the Water Absorption of Paperboard Surface with a Self-made Surface Absorbency Tester,” which is accompanied by a corporate standard “Measurement Method for Water Absorption of Paperboard Surface” and the cost of the instrument is about one hundred yuan. The time of publication of the article has not been determined.

The purpose of publishing this paper is only for paper industry peers to strive to make this instrument better. It is also hoped that the mechanics of materials mechanics can provide deflection formulas related to loose materials such as cardboard.

Solution: In one example, the paperboard material is continuous, the properties of each layer that make up the sample are not exactly the same, and the sample has different properties in all directions. The conditions are that the cantilever board has an effective length of 170mm, a width of 100mm and a thickness of 0.3mm. When placed on a plane, the board itself has a uniform load of 254g/m2 and the cantilever has a free end deflection of 137mm. The theoretical flexibility of the loose material is solved. Modulus?


Author / Zhang Renlong

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