The fatigue resistance testing machine, also known as the frame durability tester, simulates the force on the frame, especially the hinge, during opening and closing, to detect the recovery ability of the frame under fatigue testing. The instrument used to test the fatigue resistance performance of the frame is the fatigue testing device. The main function of the testing machine is to open and close the legs of the glasses back and forth 40 times per minute. The testing machine includes a touch screen display device and a safety protective cover.

The experimental device mainly includes two fixtures equipped with universal joint heads and a nose bridge support. The nasal bridge support is a rigid metal spring with a diameter of 10 mm ± 1mm and a thickness of 1 mm ± 0.5 mm. The corresponding position between the fixture and the nasal bridge support can be adjusted by at least 40 mm in the horizontal and vertical directions. One universal joint head of the device can move continuously and smoothly in one cycle: downward (30 ± 0.5) mm; outward (60 ± 1.0) mm; upward (30 ± 0.5) mm.

The frequency is 40 weeks per minute, and the device defaults to the standard speed requirement. The testing speed can be adjusted according to actual needs. And the other fixture should remain fixed. You can also choose two universal joint fixtures.

Testing process:

Before installing the test sample into the testing device, the clamping point and measuring point should be determined first. In addition to the coil spring frame, it should be ensured that the clamping point of the mirror leg is located at a distance from the hinge center equal to 70% ± 1 mm of the total length of the mirror leg, and the measuring point is located at a distance of (15 ± 1) mm from the clamping point towards the hinge center. For the coil spring holder, it should be ensured that the clamping point is located at the junction of the coil spring and the hard edge, and is moved (3 ± 1) mm towards the hinge. The measuring point is located at the clamping point, which is moved (10 ± 1) mm towards the center of the hinge.

2. Before the experiment, naturally open the legs of the mirror and measure the distance d1 between the legs at the predetermined measurement point.

3. After positioning the eyeglass frame with the test piece installed, start the device and complete 500 rotations before removing the sample from the device. Measure and record the distance d2 between legs between measurement points, in millimeters.

4. Check the cracks, fracture marks, and opening and closing conditions of the sample, and record the deformation amount d2 to d1.

After testing, the standard requires:

① The frame has no cracks or broken marks;

② The deformation amount d2-d1 shall not exceed 5 mm;

③ Can easily open and close the mirror legs with fingers;

④ The mirror legs do not close downward at any point during the opening/closing process due to their own weight.