1. Selecting the dial When using the testing machine for material testing, whether the dial is suitable or not will directly affect the correctness of the measured data. The National Metrology Verification Regulations stipulate that the testing range of the testing machine ranges from 20% of the range of each stage to the maximum test force. Therefore, for the test dial, the indication error within 20% of the starting dial is large, which requires the tester to have a basic estimate of the maximum load to be achieved before the test, so as to select the corresponding Dial. Take the 600 kN universal testing machine as an example: if the estimated maximum load of a sample is about 90 kN, then 120 kN should be selected. If the estimated maximum load is about 250 kN for a certain sample. It should be chosen to be 300 kN, which will make the test results more accurate.
2. The hanging pendulum universal testing machine adopts the pendulum fixed type to hang different pendulum according to different measuring ranges. For the three different measurement ranges on the dial, from A small to large, use Aé“Š, A+Bé“Š, A+B+C to swing, and Aé“Š is fixed on the swing bar.
3. The adjustment of the pointer zero point has also found that some operators have great errors in zero adjustment. After the zero point is adjusted, the test is started, the test result is not accurate, and the reason cannot be found. The fundamental problem is that the operator does not consider the weight of a ship type test platform, tie rods, upper beams, etc. (the working piston of the pressure test machine and the lower pressure plate), and the test result is definitely not accurate. The adjustment of the zero point of the pointer should be carried out in this way. When the dial is selected and the pendulum is placed, the active pin responds to zero. If it is not zero, the adjustment method is: start the oil pump, open the oil supply valve, so that the working piston rises 20mm~40mm from the bottom of the cylinder, close the oil supply valve, the oil pump keeps idling, visually inspect the engraved line on the pendulum and the cushioning seat. Whether the lines are aligned. If it is not aligned, the weight of the ship type test platform is not balanced. In this case, the balance é“Š needs to be adjusted until the two lines are aligned. At this point, adjust the zero point of the dial hand to the front and turn the screw to make the pointer zero.
4. Operation of the oil supply valve and the return oil valve should pay attention to the operation when loading the sample, and should be adjusted according to the loading speed specified by different samples. During the loading process, it should not suddenly rise quickly, so that the sample is subjected to impact force, and should not be suddenly closed for no reason, so that the load on the sample suddenly drops and affects the correctness of the test data. Simply put, there is no unloading when loading, and no loading when unloading. When the sample breaks or breaks, first close the oil delivery valve, then slowly open the return valve to return the pointer to zero. It must be emphasized that the delivery valve cannot be tightened too much to avoid damaging the tip of the needle, and the return valve must be tightened to prevent the return valve from leaking oil at large tonnages.
5. When the sample is clamped for tensile test, first start the oil pump, unscrew the oil supply valve, raise the working piston by 20mm~40mm, then close the oil supply valve, and clamp one end of the sample to the upper jaw. For the zero re-adjustment of the lower jaw, clamp the lower end of the sample. Before clamping, the corresponding size of the jaw should be selected according to the size and shape of the sample. The sample should be clamped on the full length of the jaw, two pieces above and below. The position of the jaws must be symmetrical. To avoid jaw movement or to catch or bite on the sliding surface, a mixture of graphite and butter can be used to lubricate the sliding surfaces of the jaws and jaw seats. When doing the compression test, install the upper bearing plate on the bottom of the cylinder block, and place the lower bearing plate on the concave spherical seat with lubrication in the center of the test bench. Note that the center of the sample must coincide with the center line of the platen to avoid eccentricity. . In the bending test, the roller bearing is fixed to the test bench by screws according to the distance required for the test. The center distance between the two seats can be determined by the center of the test bench.
6. Check whether the buffer valve is functioning as a normal buffer valve. When the sample is broken, the oil pressure in each part of the oil circuit system suddenly drops. In order not to cause the pendulum rod and the pendulum to fall back at a rapid speed, to avoid collision, A cushioning valve must be used to slowly lower the swing lever to its original position. Use Aé“Š to raise the swing lever at an angle, then relax your hand to check for cushioning. The correct way to adjust the cushion valve is to turn the handle so that the score line on the handle is aligned with the tonnage of the dial used. According to different pendulums, the knob of the buffer valve adjusting needle is turned to the corresponding position, so that the swinging rod of each tonnage can be ensured to be uniform and uniform. However, there are many test machines that have not been effective in adjusting the buffering effect according to the above method, and even if they do not work at all, it is possible to rotate the handle misalignment or the tip of the needle valve to wear, and the scribe line on the handle can be ignored. Rotate in the direction of tonnage from small to large until the buffering effect is obvious. If it still does not work when it is not fixed, the buffer should be cleaned or repaired.
Concerned about surprises
Label: How to use the material testing machine
Previous: Reasons for affecting the dynamic efficiency of aluminum shell miniature reducer Next: Analysis of the conditions of use of the three-leaf Roots blower
Exhaust Valve,Exhaust Cutout Valve,Exhaust Valve Control,Egr Valves
LIANGGONG VALVE GROUP CO.,LTD , https://www.lgvalvegroup.com