tensile testing machineIt is a very common quality control test in the paper, packaging, and printing industries, mainly used to determine key mechanical properties such as tensile strength, elongation, and fracture length of paper.The entire process can be divided into the following steps:

1、 Preparation before testing

1.Sample preparation:

Standard size: Use a standard paper cutter to cut the paper into specific strip-shaped samples. According to different testing standards (such asISO1924TheGB/T453TheTAPPIT494）The common size is width15mmAt least long250mm.

Representativeness: Samples need to be taken from different parts of the entire paper (such as vertical and horizontal) to obtain data representing the performance of the entire batch of paper.

Environmental regulation: Place the cut sample in a standard environment with constant temperature and humidity (usually23±1°C，50±2%Relative humidity) at least4Hour by hour, to achieve a balance between its moisture content and the testing environment. This is a crucial step as temperature and humidity can significantly affect the strength of the paper.

2.Equipment preparation:

Choose the appropriate range: Tensile testing machines typically have multiple force value ranges. Select a suitable range based on the estimated strength of the paper to ensure the accuracy of the test results (usually within the range of the test results)20%-80%It's better between them.

Installation fixture: Use a specialized paper stretching fixture, usually a pneumatic flat pushing fixture or a manual spiral fixture. Pneumatic fixtures can provide uniform clamping force, prevent sample slippage or fracture at the clamping point, and are a more ideal choice.

Set parameters: Enter test parameters in the control software of the tensile testing machine, including:

Sample size (width, thickness)

Gauge distance: The initial distance between the upper and lower fixtures, usually180mmor100mm.

Stretching speed: The speed at which the fixture separates, usually specified in standards (such asmm/min）.

Calibration (optional but recommended): Regularly calibrate the force and displacement of the tensile testing machine to ensure accurate data.

2、 Test operation process

1.Clamp the sample:

Place the sample vertically and smoothly into the upper fixture, and gently clamp it.

Then place the lower end of the sample into the lower fixture, ensuring that the sample is naturally vertical, without bending or prestressing.

Clamp the upper and lower fixtures tightly. For pneumatic fixtures, set a suitable clamping pressure that prevents slipping and does not damage the specimen.

2.Start testing:

Click on the control softwareStart Test button.

The drive system of the tensile testing machine starts working, and the lower fixture (or upper fixture) moves at a constant speed, applying gradually increasing tensile force to the sample.

3.Data collection:

During the stretching process, the force sensor inside the machine will monitor and record the tension applied to the sample in real time（F）.

The displacement sensor (or encoder) will synchronously record the displacement of the fixture（ΔL）This displacement can be converted into the elongation of the sample.

4.Sample fracture:

When the tensile force exceeds the ultimate strength of the paper, the specimen will break at its weak point.

The test automatically stops and the fixture returns to its initial position.

3、 Data Analysis and Results

The testing software will automatically record the entire processThe pulling force-Displacement "curve (i.e. stress)-Strain curve) and calculate the following key performance indicators:

1.Tensile strength:

Definition: The rated tensile force that a paper can withstand when it breaks.

calculation:`tensile strength(kN/m)=pull(N)/Sample width(m)`

Meaning: Reflecting the ability of paper to resist tensile damage.

2.Fracture elongation:

Definition: The percentage of elongation at break of a specimen to the original gauge length.

calculation:`elongation(%)=(Elongation at break/original gauge length)×100%`

Meaning: Reflecting the flexibility and toughness of paper. The higher the elongation, the less likely the paper is to become brittle.

3.Tensile energy absorption value:

Definition: The total energy absorbed by paper during the stretching process until it breaks, i.eThe pulling force-The area below the displacement curve.

Meaning: This is a comprehensive evaluation index that considers both strength and elongation, which is very important for evaluating the durability of packaging paper under impact (such as whether the paper bag is easily broken after falling off).

4.Elastic modulus:

Definition: In the initial stage of stretching, the ratio of stress to strain, which is the slope of the curve.

Meaning: Reflecting the paper's'Rigidity' or 'stiffness'. The higher the modulus, the harder the material and the less likely it is to deform.

5.Fracture length:

Definition: A theoretical value that refers to the length of paper required to break due to its own gravity.

Calculation: It is calculated based on the tensile strength and the basis weight (gram weight) of the paper.`Fracture length(km)=[tensile strength(N/m)/(quantitative(g/m²)×9.8)]`

Meaning: This is a strength index that eliminates the influence of thickness, making it easier to compare the strength of different quantitative paper.

4、 Precautions

Clamping effect: Ensure that the specimen fractures within the fixture, rather than at the edges of the fixture. If it breaks at the clamping point, the data is invalid.

Test direction: It is necessary to distinguish the longitudinal direction of the paper（MD）And horizontally（CD）Conduct testing because there is a significant difference in the performance of paper in these two directions.

Test speed: Strictly set the stretching speed according to the standard, as speed can affect the test results.

Effective data: Usually, at least one test is required under the same conditions5Take a valid sample and then take the average as the final result.

In summary, using a tensile testing machine to test paper is a highly standardized process. By precisely controlling conditions and measuring force and displacement, various key mechanical properties of paper can be quantified, providing scientific basis for production quality control, product development, and material selection.