Definition
The bending resistance tester is a special laboratory instrument used to measure the ability of materials (mainly paper, cardboard, textiles, leather, plastic film, etc.) to withstand reciprocating folding under specific conditions. The measurement results are usually expressed as the number of double folds that the material can withstand before fracture (i.e., the bending resistance value), which is one of the key parameters for evaluating the mechanical durability and service life of the material.
Principle
The core working principle of the flexurality tester is to simulate the repeated bending stress of the material in actual use. The instrument uses a precise mechanical structure to make the specimen bend at a reciprocating angle around a folding roller of a specific diameter under the specified tension. Each complete reciprocating motion is counted as a bifold. The test continues until the specimen breaks, at which point the instrument automatically records the number of folds. Some advanced models may integrate sensors and control systems to precisely control folding speed, tension, and ambient temperature and humidity conditions.
Measurement method
The measurement process must strictly follow the corresponding international, national or industry standards, such as ISO 5626 (determination of fold resistance of paper and cardboard), GB/T 457 (measurement of fold resistance of paper and cardboard), etc. The general steps include: first, the specimen is cut to the size specified by the standard; secondly, the specimen is clamped on the chuck of the instrument and the initial tension specified by the standard is applied; then, set the folding angle and frequency of the instrument; Start the instrument, and the specimen begins to fold back and forth; Finally, when the specimen is completely broken, the number of folds displayed by the instrument is recorded as the bending resistance result of the specimen. Typically, multiple samples are tested for the same sample to obtain an average.
Influencing factors
The flexural resistance test results of a material are influenced by a variety of factors. Factors related to the material include its fiber type, length and bond strength (for paper), thickness, uniformity, and internal stress state. Factors related to the test conditions of the instrument are crucial: the amount of tension applied directly affects the bending stress; The diameter of the folding roller determines the radius of curvature of the bend; Folding speed may affect the fatigue response of the material; The temperature and humidity conditions of the test environment can have a significant impact on the flexibility of many materials. Therefore, ensuring standardization and consistency of test conditions is fundamental to obtaining comparable data.
Applications
The application of the bending resistance tester is very wide. In the paper and packaging industry, it is used to evaluate the service life and durability of products such as banknote paper, map paper, packaging cardboard, containerboard, etc. In the textile industry, it is used to test the fatigue resistance of fabrics and non-woven fabrics against repeated bending. In the leather industry, it is used to measure the flexibility and quality of upper leather, clothing leather, etc. In the plastics and film industry, it is used to test the folding resistance of packaging films and composite materials. In addition, the instrument is a common equipment for material research and development, quality control and compliance verification in quality inspection institutions, scientific research institutes and production enterprises.
Selection considerations
When choosing a flexural resistance tester, users should consider comprehensively based on actual needs. First, it is necessary to clarify the type of material to be tested and the test standards to be followed, and ensure that the technical parameters of the instrument (such as folding angle, tension range, folding roller diameter, and counting range) fully comply with the standard regulations. Secondly, consider the test efficiency and automation, such as whether it has functions such as multi-station simultaneous testing, automatic clamping, and direct data output. Thirdly, the structural rigidity of the instrument, the wear resistance of key moving parts, and the stability of long-term operation are the keys to ensuring the repeatability and reproducibility of test results. Finally, the user-friendly design of the user interface, the ease of maintenance, and the technical support and service capabilities of the supplier should also be included in the evaluation.