About the Principle of Plastic Tensile Testing
Tensile properties, as the basic properties of materials, provide basic data support for practical production, research and development, application, quality control, and standard specification, etc. Tensile properties are used to analyze the static tensile mechanical properties of the material through the tensile stress-strain curve of the specimen and each test data to evaluate its tensile strength, yield strength, elongation at break and modulus of elasticity.
So what is the actual principle? Let’s understand it practically.
Principle constant velocity stretching along the longitudinal principal axis of the specimen until the specimen breaks or its stress (load) or strain (elongation) reaches a predetermined value, measuring the load and its elongation sustained by the test in the process. Method 1, these methods are applicable to specimens of selected dimensions prepared by molding, or prepared from finished or semi-finished products (such as molded parts, laminates, films and extruded or cast plates) by machining, cutting or punching. Specimen types and their preparation are described in the relevant section of GB/T 1040 on typical materials. Multi-purpose specimens can be used in some cases. Multi-purpose and small specimens see ISO 20753 . 2, this method specifies the preferred size of the specimen. Different sizes of specimens or different states of the adjusted specimen test results are not comparable. Other factors, such as test speed and condition of the specimen, can also affect the test results. Therefore, these factors should be strictly controlled and recorded when performing data comparison.
This method is applicable to the following materials. rigid and semi-rigid thermoplastic molded, extruded and cast materials, including filled and reinforced blends in addition to unfilled types, rigid and semi-rigid thermoplastic sheets and films; – rigid and semi-rigid thermoset molded materials, including filled and reinforced composites, rigid and semi-rigid thermoset sheets, including laminates. –fiber-reinforced thermoset and thermoplastic composites mixed with unidirectional or non-directional reinforcements such as felts, fabrics, untwisted rovings, short-cut raw yarns, mixed fiber reinforcements, untwisted rovings and milled fibers; sheets made of pre-impregnated materials (prepreg blanks); – -Thermochromic liquid crystal polymers. In view of ISO 1926, this method is generally not applicable to rigid foam materials or interlayer structure materials containing microporous materials. Tensile stress: The tensile load applied to a specimen per unit initial cross-sectional area within a measured scale. Tensile strength: In the tensile test, the maximum tensile stress that the specimen is subjected to until fracture. Tensile fracture stress: in the tensile stress-strain curve, the stress at fracture. Tensile yield stress: In the tensile stress-strain curve, the stress at the yield point. Elongation at break: In tension, when the specimen breaks, the ratio of the increase in the distance between the markers to the initial marker distance, expressed as a percentage. Modulus of elasticity: The ratio of the stress (tensile, compressive, bending, shear) to the corresponding strain produced by the material within the elastic deformation. Poisson’s ratio: The negative value of the ratio of the tensile deformation in one of the two axes perpendicular to the tensile direction to the deformation in the tensile direction within the starting linear portion of the longitudinal strain to normal strain relationship curve.