7. Test Methods

7.1 Dimensions and Appearance

• 7.1.1 Dimensions shall be inspected using special or universal measuring tools with a scale division value not greater than 0.5 mm.
• 7.1.2 Appearance quality shall be inspected by visual inspection.

7.2 Force Characteristics

• 7.2.1 Test Conditions
  The test shall be carried out in an environment of 20°C ± 2°C. Before the test, the gas spring shall always be in the extended state, and the piston rod shall not be pressed. The sample shall be placed in an environment of 20°C ± 2°C for

7.2 Force Characteristics

• 7.2.1 Test Conditions
  The test shall be carried out in an environment of 20°C ± 2°C. Before the test, the gas spring shall always be in the extended state, and the piston rod shall not be pressed. The sample shall be placed in an environment of 20°C ± 2°C for more than 2 hours. The test measurement speed is 400 mm/min, and the force measurement accuracy is not lower than 1%.
  Note: For variable – damping gas springs and pressure – damping gas springs, the test speed is 100 mm/min – 300 mm/min.
• 7.2.2 Test Methods
  The test methods for force characteristics are divided into dynamic tests and static tests. The dynamic test method should be used as much as possible.
  • 7.2.2.1 Dynamic Test
    Install the piston rod of the gas spring vertically upward on the testing machine. In the first cycle of starting the machine, record the starting force. In the second cycle, record the extension force and compression force , , ,  at the force – measuring point , and calculate the nominal force, dynamic friction force and force ratio, and draw the force – displacement curve. At the same time, observe whether there is any jamming or obvious jitter of the gas spring piston rod.
  • 7.2.2.2 Static Test
    Install the piston rod of the gas spring vertically upward on the testing machine. In the first cycle of starting the machine, record the starting force. In the second cycle, record the extension force and compression force , , ,  at the force – measuring point , and calculate the nominal force and force ratio, and draw the force – displacement curve. The static test stays at the force – measuring point  for 3 s. At the same time, observe whether there is any jamming or obvious jitter of the gas spring piston rod.

7.3 Extension Speed

• 7.3.1 Test Conditions
  The test shall be carried out in an environment of 20°C ± 2°C. Before the test, the sample shall be placed in an environment of 20°C ± 2°C for more than 2 hours. The scale division value of the timer is not greater than 1/100 s.
• 7.3.2 Test Methods
  Install the piston rod of the gas spring vertically downward on the testing machine. Start the testing machine, press the piston rod into the specified stroke, and then remove the external force to allow the piston rod to extend freely. Measure the extension time  and the extended stroke , and calculate the extension speed (average speed)  according to the following formula:
  
  Where:
   – Extension speed, in millimeters per second (mm/s);
   – Stroke, in millimeters (mm);
   – Extension time, in seconds (s).

7.4 High and Low Temperature Resistance Performance

Place the gas spring in a high – temperature test chamber at 110°C ± 5°C for 1 hour, then take it out and place it in a normal – temperature environment for 2 hours. Then place the gas spring in an environment of – 40°C ± 2°C, and then place it in an environment of 80°C ± 5°C for 4 hours. The above is a high – low temperature cycle test. Test the force characteristics of the gas spring after the high – low temperature test according to 7.2, and calculate the attenuation of the nominal force .

7.5 Cycle Life

• 7.5.1 Normal Temperature Cycle Life
  Install the piston rod of the gas spring after the high – low temperature test downward on a testing machine equipped with an oil – collecting device, and conduct a cycle life test at a frequency of 4 times/min – 6 times/min (for variable – damping gas springs and pressure – damping gas springs, it is 3 times/min – 5 times/min). During the test, the piston rod should extend freely. After 25,000 cycles, test the force characteristics according to 7.2, calculate the attenuation of the nominal force , and then weigh the amount of oil brought out on an electronic scale with an accuracy of not less than 0.01 g.
• 7.5.2 Environmental Cycle Life
  Install the piston rod of the gas spring downward on a high – low temperature dynamic cycle testing machine equipped with an oil – collecting device. Lower the test environment temperature to – 40°C, and conduct a cycle life test at a frequency of 2 times/min – 4 times/min for 1,000 cycles. Take it out and test the force characteristics according to 7.2, and calculate the attenuation of the nominal force . Then install the gas spring on the testing machine, adjust the test environment temperature to 80°C ± 5°C, and conduct a cycle life test at a frequency of 4 times/min – 6 times/min (for variable – damping gas springs and pressure – damping gas springs, it is 2 times/min – 5 times/min) for 1,000 cycles. Take it out and test the force characteristics according to 7.2, and calculate the attenuation of the nominal force . Then weigh the amount of oil brought out on an electronic scale with an accuracy of not less than 0.01 g. After the high – low temperature dynamic cycle test, the gas spring is subjected to a normal – temperature cycle life test of 18,000 times. Test the force characteristics according to 7.2, calculate the attenuation of the nominal force , and then weigh the amount of oil brought out on an electronic scale with an accuracy of not less than 0.01 g.

7.6 Tensile Resistance Performance

Fix the extended gas spring on the testing machine, and load it at a speed of 1 mm/min – 2 mm/min according to the specified value in Table 3, and keep it for 3 minutes. After unloading, test the force characteristics according to 7.2 or observe.

7.7 Corrosion Resistance Performance

The corrosion resistance test of the gas spring shall be carried out in accordance with the provisions of GB/T 1771 or GB/T 10125.

Technical Specification for Compression Gas Springs (English version of national strandard, initiated by LeiYan Gas Springs), proposed and prepared by SAC/TC 235 (National Technical Committee 235 on Spring of Standardization Administration of China).