Explanation

The mechanical property test to determine the strength and plasticity of materials under uniaxial tensile load is one of the most commonly used mechanical property test methods. The test must be conducted in accordance with relevant standards. Slowly load the specimen with a certain shape, size and surface roughness on the testing machine, record the size of the load and the deformation of the specimen, draw the tensile curve, and obtain the strength and plasticity indicators of materials. The sample shapes include cylindrical, plate, and tube shapes. There are two types of testing machines: hydraulic type and mechanical type. The testing machine currently developed is equipped with a load measurement and control system, a displacement measurement and control system and a sample deformation measurement system connected to the computer to achieve the control of the test rate (strain rate, stress rate), automatically measure and record the stress-strain, stress time, strain time and displacement time curves. The test is carried out according to the program and the test results are calculated and data processed. The measured strength indicators are the main technical parameters for strength design and the main basis for evaluating the quality of materials; Plastic index is an important parameter to evaluate the safety of components, which indicates the strength reserve of materials. The main parameters that affect the test results are: sampling direction and location of the sample, processing accuracy and measurement accuracy of the sample shape and size, loading coaxiality of the sample, measurement accuracy of load and deformation, testing rate, calibration of the testing machine, etc. In composite materials, it refers to the test method for measuring the tensile properties of composite materials. The main test object is fiber laminated composite materials with various ply structures. Under standard temperature and humidity conditions, apply a tensile load to the composite materials sample on the materials testing machine at a certain speed, and measure the tensile deformation with a resistance strain gauge or extensometer until the sample is damaged. The test results are calculated from the measured stress-strain curve. The positive axis tensile test of unidirectional pressure plate means that the fiber orientation of the sample is consistent with the loading direction, and the tensile strength, elastic modulus and Poisson's ratio are measured in the 0 ° and 90 ° directions respectively. These are essential performance data for laminate design, which can be used to estimate the strength and modulus of any laminate. The off-axis tensile test means that the orientation of the sample fiber forms a direction angle with the loading direction, which can be used to measure the in-plane shear properties of the laminate (using the symmetric laminate spread by 45 ° soil) or to measure the off-axis tensile modulus to verify the validity of the compliance conversion equation. To obtain accurate and reliable test results. It is necessary to ensure that there is a uniform stress distribution on the cross-section of the sample during the test process, and there are requirements for the geometric shape and size of the sample. The sample should be straight, with a uniform cross-section and no defects such as voids, impurities, and uneven fiber arrangement inside. The clamping parts at both ends of the sample should be attached with reinforcing plates to ensure uniform load transfer.

Classification