1, what's the tear test? 

Tear test is a standardized testing method for determining the resistance of materials to tear propagation. It is mainly used in fields such as plastic film, textiles, paper, rubber, waterproofing membranes, medical materials, etc., to evaluate the resistance of materials to damage in the presence of defects or cuts. The core principles, methods, and key points are as follows:

Tearing process: Measure the maximum force or energy required to continue tearing along the direction of the pre cut (such as a cut or notch) specimen by stretching it.

Equipment requirements:

The UnitedTest universal testing machine, with tear fixture used to execute the tewar test. Needs to have the ability to accurately control the separation speed of the fixture (usually 100 ± 10 mm/min) and continuously record the force displacement curve. The lower limit of the load range should be ≥ 2000N, and the force measurement accuracy should reach ± 2%.

2, Relevant standards of textile tearing strength testing. 

Pendulum method: ISO 9290, ASTM D1424, DIN 53862, DIN EN ISO 13937.1, KS-K 0535, EN ISO 13937.1

Tongue method: ASTM D2261, DIN 53859.1, DIN EN 13937.4, NF G 07-146, NFG 07-148, NFG 07-149, KS K 0536, EN ISO 13937.4

Trapezoidal method: ASTM D5587, DIN 53859.5, KSK 0537 

Other Methods: BS 4303(Wing Method), DIN 53859.2(Rectangular method), DIN EN ISO 13937.2(Trouser method) , DIN EN ISO 13937.3(Wing Method) , NFG 07-145(Nail method) , NF G 07-147 (Nail method).NF ISO 13937.3(Wing Method). EN ISO 13937.2(Trouser method)

3, Main test methods and the characters. 

Trapezoidal method:

Draw two diagonals at the end of the strip, form an isosceles triangle in the middle, and then cut at the bottom. Attempt to clamp and apply tensile load along two diagonal lines. The first yarn near the incision will bear a greater external force, while the other yarns will bear a smaller force. When the first yarn cracks, it will split open. Then the line below will become the first yarn. It will withstand strong tension until it tears. Finally, the maximum force during the process is the tearing strength of the fabric. It is directly related to tearing force and is used to evaluate the toughness of fabrics. The comparability and stability of the results are good, easy to measure, and can be performed in ordinary machines with moderate strength.

Tongue technique:

Cut it into two pieces along the length of the strip. Apply tensile loads to the two fixtures of the machine separately. Longitudinal yarns experience tension; Horizontal yarn sliding. The tension and elongation of the sliding yarn increase sharply, forming a force triangle. The first yarn at the bottom cut of the triangle bears the maximum force. When it tears, it will have the highest tear value. The yarn breaks one by one until the fabric is torn apart. The factors that affect triangles can also affect the tear strength of fabrics. So, this is why the strength of tongue tearing not only reflects the toughness of the fabric, but also evaluates the impact caused by factors such as dyeing and finishing processes on the frictional effect of tearing.

Hammer drop method:

This testing method uses the principle of energy dialogue, which measures the energy consumed by tearing a specific length of fabric during testing. The fall and potential energy consumed by the fan-shaped pendulum. Energy will be converted into tearing strength, which is the average tearing strength during the tearing process. The characteristics of the hammer drop method and the tongue method are similar. They quickly completed the tearing process. It is easy to use. The result is stable and popular nationwide.

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