Definition
The sole bending tester is a specialized testing equipment used to simulate and evaluate the durability performance of shoe sole materials under repeated bending stress. The device simulates the bending state of the sole when a person walks or runs, and performs cyclic bending tests on the sole, sole material or complete footwear to determine its bending fatigue resistance. Its testing basis is usually based on international standards such as ISO 17707, SATRA TM92, and national standards such as GB/T 3903.1, which provide a unified test method for the evaluation of footwear folding resistance.
Principle
The working principle of the sole bending tester is based on mechanical reciprocating motion. The equipment usually fixes the shoe or sole specimen to a specific fixture so that the bend of the specimen is aligned with the bending axis of the equipment. The drive mechanism (such as the motor driving the crank connecting rod or cam mechanism) drives the clamp to perform periodic reciprocating bending motion, so that the specimen is repeatedly bent within the set angle. Each bending cycle simulates the sole bending process in a gait cycle. During the test, the device records the number of bends and stops when the preset number of cycles is reached or when the specimen shows obvious damage (e.g. cracks, glue opening, etc.). Some models can monitor resistance changes during bending to assess the attenuation of material properties.
Measurement method
Standard measurement methods typically follow these steps: First, a specimen is prepared according to the standard requirements, which can be a shoe, a sole, or a specimen of a specific shape cut from the sole. Install the specimen in the testing machine fixture and adjust the bending angle (commonly 45°, 50°, or 90°, depending on the standard), bending frequency (such as 100 to 300 times per minute), and other parameters. After starting the device, the specimen continues to bend under set conditions. During or after the test, the specimen is observed and measured. The main evaluation indicators include: whether cracks appear on the surface of the specimen after reaching the specified number of bends, the length of the cracks, whether there is glue opening at the bottom, and wear marks. The performance evaluation can be expressed as follows: under the bending angle θ and frequency f, after N times bending, the specimen does not have damage that exceeds the allowable standard.
Influencing factors
Test results are influenced by multiple factors. Specimen factors include the type of sole material (e.g., rubber, EVA, polyurethane, etc.), formulation, thickness, structure (e.g., mono-material or composite), and molding process. Environmental factors such as laboratory temperature and humidity can affect the flexibility and fatigue properties of polymer materials, and standard tests often require them to be performed under specified temperature and humidity conditions. The setting of equipment parameters is the key operating factor, and the size of the bending angle directly affects the stress-strain level applied to the specimen. The bending frequency affects the test efficiency and the possible heat accumulation effect. The clamp should be designed and clamped in such a way that the bend position is accurate and does not create additional stress concentrations. In addition, the pretreatment state of the specimen, such as whether it has been conditioned by the environment, can also affect the results.
Applications
The sole bending testing machine is mainly used in quality control, research and development and certification in footwear and related industries. In shoe manufacturing enterprises, it is used to conduct factory inspections of raw materials (such as sole film, midsole foam) and finished shoes to ensure that the products meet the basic requirements for wearability. During the R&D phase, materials engineers optimize product designs by comparing soles of different formulations or structures under the same bending conditions. Third-party testing institutions conduct tests according to relevant standards to provide data support for product quality certification and conformity assessment. In addition, the device is also suitable for academic research on the fatigue mechanism of sole materials in research institutions.
Selection considerations
Choosing a suitable sole bending tester requires comprehensive consideration of technical parameters and functional requirements. The core parameters include the bending angle range, the bending frequency range, the maximum number of bends counting capability, and the number of specimens tested simultaneously (number of stations). The equipment should be able to meet the requirements of the parameters in the test standards that the target product needs to follow. The versatility and interchangeability of the fixture are important to accommodate different samples such as testing into shoes and cutting sections. The durability and operational stability of the equipment are the basis for ensuring the reliability of long-term test data. The degree of automation of the control and recording system, such as whether it has functions such as preset programs, automatic shutdown, and data logging, affects the efficiency and traceability of the test. In addition, consider the size of the equipment, the noise of operation, and the technical support and service provided by the manufacturer.