Overview
Flexural resistance measurement is a critical test to evaluate a material's ability to resist fatigue fracture under repeated bending stress. The high-frequency folding test simulates the rapid and repeated folding conditions of materials in actual use, and puts forward more stringent evaluation requirements for the durability of materials. The corresponding measuring instrument must have high frequency, high accuracy and excellent stability to meet the relevant standards for the consistency of test conditions.
High-frequency folding test principle
The core principle of high-frequency folding testing is to make the specimen bend rapidly and reciprocatingly within a certain angle range under constant tension until the specimen breaks. Record the number of folds at this time, which is the flexibility of the material. The test frequency is significantly higher than that of conventional testing, which poses a particular challenge to the instrument's drive mechanism, fixture design, and control system. The basic mechanical relationship can refer to the following formula:
σ = (E * t * θ) / (2 * L)
Among them, σ represents the bending surface stress of the specimen, E is the elastic modulus of the material, t is the thickness of the specimen, θ is the folding angle, and L is the effective distance between the fixtures. Under high frequency conditions, the influence of inertial force and thermal effect on material properties needs to be considered.
Instrument technical characteristics
To achieve reliable high-frequency testing, the instrument needs to be specifically designed in several ways. The drive system typically employs servo motors or linear motors to ensure smooth and precise power delivery during high-frequency reciprocating motion. The design of the fixture should ensure that the specimen is firmly clamped to avoid slipping or stress concentration during high-speed movement. The control system needs to be able to accurately set and maintain the folding frequency, angle and tension, and monitor the test process in real time. The data acquisition system should have high-speed response capabilities to accurately capture the moment of specimen fracture.
Test Standards
High-frequency folding tests should be carried out according to relevant national or international standards, such as paper, cardboard, textiles, metal foils, flexible electronic materials, etc. Key test parameters include folding frequency, folding angle, applied tension, fixture radius, and ambient temperature and humidity. The parameter setting should be strictly in accordance with the standard on which it is based and clearly documented in the test report.
| Key parameters: | Description |
| Folding frequency | The number of complete folding cycles completed per unit time is the core metric of high-frequency testing. |
| Folding angle | The sum of the maximum angles of the specimen bending to the left and right. |
| Apply tension | A constant force applied along the length of the specimen during testing. |
| environmental conditions | The temperature and relative humidity of the test environment have an impact on the results of many materials. |
Applications:
High-frequency bending resistance testing is widely used in several industrial fields. In the packaging industry, it is used to evaluate the durability of packaging paper, box cardboard; In the textile industry, it is used to test the fatigue resistance of fabrics, non-woven fabrics and clothing accessories; In the electronics industry, it is crucial for the R&D and quality control of flexible circuit boards, foldable display substrates, and other products. This test can quickly screen materials, predict the service life of products under long-term dynamic loads, and provide data support for product design, process improvement, and quality control.
Notes:
When performing high-frequency folding tests, there are several key points to note to ensure the accuracy of the results. The preparation of specimens should be standardized, and the edges should be flat and burr-free. The instrument needs to be preheated and calibrated in the environment required by the standard to ensure that the moving parts are well lubricated. The fixture should be checked regularly for wear, excessive wear can change the effective radius, affecting the test results. For specimens of different materials and thicknesses, the appropriate tension and frequency range should be selected to avoid overloading the instrument or abnormal fracture of the specimen. During the test, the fracture pattern of the specimen should be observed to assist in the analysis of the failure mode of the material.
Conclusion
The high-frequency folding test is a rigorous test of the dynamic mechanical properties of a material. Through precise mechanical design, stable control logic, and accurate data acquisition, the dedicated flexural resistance tester makes it possible to simulate and quantify the durability of materials under repeated bending at high frequency under laboratory conditions. Following the standardized test process and paying attention to the control of key parameters and instrument maintenance is the basis for obtaining reliable and comparable test data, which is of practical significance to product development and quality assurance in related industries.
References
ISO 5626: Determination of paper folding resistance.
ASTM D2176: Standard Test Method for Determining the Flexural Resistance of Paper.
GB/T 2679.5: Determination of folding resistance of paper and cardboard.
Compilation of standards for fatigue resistance test methods for materials in related industries.