Definition
Computerized tensile testing machine is a kind of material mechanical property testing equipment that integrates computer control and data acquisition system. It applies axial tensile force to the specimen through a precision mechanical structure, and simultaneously measures the force value and deformation to evaluate the key mechanical parameters such as tensile strength, elongation at break, and elastic modulus of the material. The equipment is widely used in industrial production, scientific research and testing and quality monitoring, and its core feature is to realize the automatic control of the testing process and the intelligence of data processing.
Principle
The working principle of the computerized tensile testing machine is based on Newton's laws of mechanics and Hooke's laws. The equipment is usually composed of a loading frame, a servo drive system, a high-precision force sensor, a displacement encoder and a computer control system. When working, the servo motor drives the ball screw to produce precise displacement, driving the fixture to exert a tensile load on the specimen. The force sensor detects the load value in real time, and the displacement encoder measures the deformation within the specimen gauge. The computer system controls the loading rate according to the preset program, collects the force-displacement data synchronously, and calculates the stress-strain curve and related mechanical indexes of the material through the built-in algorithm. The basic stress calculation formula is:
σ = F / A
where σ is the engineering stress, F is the real-time load, and A is the original cross-sectional area of the sample.
Main measurement methods
According to international standards such as ISO 6892 and ASTM E8, the standard measurement methods for computerized tensile testing machines include static tensile testing and cyclic loading testing. Static tensile testing typically uses constant rate loading until the specimen breaks, and the force-displacement curve is recorded throughout the process. Before testing, the specimen size should be accurately measured, and the gauge length and loading rate should be set. For the determination of elastic modulus, the segmented acquisition method is often used to improve the accuracy during the elastic deformation stage. cyclic loading tests are repeatedly loaded with preset loads or displacement amplitudes to study the fatigue characteristics or hysteresis behavior of materials. All tests are performed under standard temperature and humidity conditions, and the principle of three or more parallel tests is followed to ensure data reliability.
Factors influencing measurement results
The accuracy of test results is influenced by multiple factors. In terms of sample preparation, the sampling direction, processing accuracy and surface roughness may cause stress concentration. Equipment factors include the calibration status of the force sensor, the coaxiality error of the fixture, and the sampling frequency setting. Changes in temperature and humidity in environmental conditions can affect material properties, especially polymer materials. The choice of operating parameters such as loading rate directly affects the yield behavior of the material, and too high a rate may result in low plastic deformation measurements. The selection of zero point correction and curve smoothing algorithms during data processing will also introduce system errors. Therefore, standard operating procedures require regular equipment metrology certification and method validation using standard reference materials.
Applications
In the metal material industry, this equipment is used to test the strength and ductility of steel plates and alloy wires. The polymer industry uses it to evaluate the fracture toughness of plastic films and the elastic recovery rate of rubber products. In the textile sector, the spinning process is optimized by testing the breaking strength of the fiber bundles. The packaging industry tests the peel strength and compressive performance of adhesive tapes. In the inspection of building materials, it is used to verify the compliance of steel bars and concrete reinforced fibers. The electronics industry is used to evaluate the strength of solder joints and the flex resistance of flexible circuit boards. Scientific research institutions use it to develop new materials and conduct failure analysis research.
Key points of equipment selection
The force range of the test material should be defined first, and the equipment range is recommended to cover 20% to 80% of the expected maximum load. The space structure needs to consider the maximum specimen size and fixture travel. The accuracy level is selected according to the requirements of the testing standard, usually the industrial quality inspection uses level 1 accuracy, and scientific research institutions need to be above 0.5 level. The control system should support a variety of international standard test programs and have extended programming capabilities. The fixture configuration needs to match the shape of the specimen, and accessories such as high-temperature chambers and extensometers can be selected to meet special test needs. The data system should provide complete curve analysis tools and compliance reporting formats. In terms of maintenance costs, attention should be paid to the type of lead screw, sensor stability, and software upgrade path. It is recommended to verify the suitability of the equipment through sample pre-testing before making purchasing decisions.