An O-ring is a rubber ring with a circular cross-section, so named due to its O-shaped cross-section. It is widely used in hydraulic and pneumatic transmission systems. Accurate product selection can be made based on dimensions such as different media, temperatures, and application scenarios. The tensile property test refers to a series of tests to determine the characteristics of O-rings under tensile loads, also known as a tensile test. As one of the basic methods for testing the mechanical properties of materials, it is mainly used to verify whether materials meet specified standards and to study material performance.

I. Test Equipment

(1) This test is conducted on a tensile testing machine, which shall comply with the relevant provisions of GB/T 528-1998 Determination of Tensile Stress-Strain Properties of Vulcanized Rubber or Thermoplastic Rubber. The tensile testing machine shall be equipped with a guided rack device and a device for measuring the elongation of the test sample.

(2) The test fixture consists of two upper and lower pulleys with ball bearings, each with a diameter of at least 12 mm. When the two pulleys are close to each other, the distance between their centers shall be within 25 mm. The lower fixture is equipped with a gear transmission device, which shall mesh with the guided rack on the tensile testing machine during the test.

(3) For linear test fixtures, universal tensile test fixtures are used, but it is necessary to ensure that the test sample does not break at the clamping position during the test.

II. Test Samples

(1) Standard samples shall have an inner diameter of 40 mm ± 0.3 mm and a cross-sectional diameter of 3.55 mm ± 0.1 mm. The number of samples shall be 5.

(2) O-rings with an inner diameter larger than 40 mm (of other sizes) or segments cut from O-rings (linear samples with a length of not less than 120 mm) can be used for the test. However, the test results of such samples cannot be compared with those of standard samples.

III. Test Procedures

(1) Measure the cross-sectional diameter and inner diameter of the sample in accordance with regulations. For linear samples, the measurement shall be carried out in accordance with the methods specified in Clauses 4.2.4 and 4.2.5 of GB/T 528, with the marking distance of the working section being 25 mm.

(2) Place the O-ring over the pulleys of the upper and lower fixtures (as close to each other as possible) to ensure no tensile stress is applied to the sample. Connect the elongation measurement system and adjust the zero point (i.e., determine the center distance between the two pulleys when the elongation rate of the O-ring’s inner circumference is zero).

(3) Start the machine and stretch the sample at a speed of (500 ± 50) mm/min. Record the load when the sample is stretched to the specified elongation, as well as the load and elongation at break.

Expression of Test Results

There shall be 5 sets of measurement results. The test result shall be the median of the calculated results. The elongation at break shall be rounded to an integer, while the modulus at a specified elongation and tensile strength shall be rounded to one decimal place.