In the ozone aging test, the evaluation of the test results mainly adopts three methods; one is to record the time when the sample begins to crack during the test. The second is to classify the crack of the sample, and the third is to test after the test. The samples are taken for photography and then evaluated intuitively. The latter two methods can only give a qualitative concept and take time (such as taking photos). After referring to the relevant technical information, we tried to use the method of measuring the modulus (different elongation) of the ozone aging tablets to evaluate the test results. This method is based on the fact that when the test piece is under attack by ozone in the stretched state, the rubber molecular chain is broken due to the reaction of ozone and the double bond of the rubber molecule until a characteristic crack perpendicular to the stretching direction is generated. During this aging process, the stress that the rubber limb specimen can withstand under constant elongation is getting smaller and smaller. Therefore, it was decided to develop a small tensile machine suitable for measuring the stress of the sample before and after the ozone aging test.
1. The electrical working principle of the small tensile testing machine (1) The basic principle of the electrical principle block diagram of the xK-1 1 automatic small tensile testing machine.
When working, first adjust the display to zero value, and preset the tensile test piece to extend a, and start the start signal. The voltage signal output by the sensor first enters the filter to filter out all peaks and AC interference, then enters the amplifier Amplified, the digital signal output by it is displayed as a force value. Due to the start, the motor rotates the encoder disk to work, and the encoder disk has 50 through holes to form a binary cyclic code. Photoelectric coding is a kind of high-precision shaft rotation angle converted into coded electrical signals, that is, converted into corresponding digital quantity (length quantity) by optical conversion method. The control system controls the action of the relay according to the preset pulse value (pulse conversion length) to make the motor rotate or stop working.
(2) Technical performance:
Load: O ～ 3ON; Frequency: 50Hz; Precision: 2 × 10-2N; Resolution: 1/200 (2 × 10 N per word); Power supply voltage: 220V ± 10; Test piece length: 40toni (variable) Maximum display value: 1999; sample tensile length grades: 3O, 5O, 7O, 1O0; display mode is light-emitting diode display; primary element uses tension and pressure sensor, which can work continuously.
2. The mechanical principle part of the small tensile testing machine This machine uses a reversible motor to drive the screw, and the bar to drive the sliding sleeve and the cross bridge, so that the lower splint can be moved up and down. When the motor rotates the lower splint in the forward direction, the lower splint moves downwards, and the sample is stretched, which is obtained by the pull and pressure sensor above.
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