About how to choose a high-precision material testing machine

Regarding the question of how to choose a high-precision material testing machine, we need to first understand the accuracy of the test machine. In JJG 139-1999 "Procedures for the Inspection of Tension, Pressure and Universal Test Machines", there are three types of test machine levels: 0.5/1/2. The indicators of the three levels of testing machines are different, such as: test force display value (relative error, relative repeatability error, return journey relative error, relative resolution force, zero point relative error, etc.), coaxiality, speed, etc., and the common accuracy currently includes level 0.5 and level 1, compared with level 0.5, which is higher than level 1. The electronic universal testing machine of the same level has more advantages than the hydraulic universal testing machine.

The factors that affect the accuracy of electronic universal testing machines and hydraulic universal testing machines include the following:

1. First of all, the force sensor is one of the important components that affect the accuracy of hydraulic universal testing machines. The stability of the force sensor is one of the key parts that directly affect the accuracy of sensors. Among universal testing machines manufacturers, generally electronic universal testing machines use spoke sensors or s-type force sensors, while hydraulic universal material testing machines use oil pressure sensors. Currently, the sensors with good stability on the market include American Quanli or American Shiquan, which are much better than domestic sensors in terms of accuracy control and service life, but the price is relatively high.

2. The second point is the main engine oil cylinder system of the hydraulic universal testing machine, because the hydraulic cylinder is the most critical component of the main engine, the gap between the hydraulic cylinder will increase friction, which poses hidden dangers to the measurement results. At present, the oil cylinders used in the domestic market have gap oil return technology oil cylinders. There are also old-fashioned sealing ring oil cylinders. The former is the latest technology, with high processing cost and complex assembly process. The oil cylinder gap of the sealing ring is relatively large, resulting in increased friction and relatively short service life. The gap sealing oil cylinder can generally last for decades in service life, and can also maintain the accuracy unchanged.

3. The third point is that the frame structure of the main machine is also an important indicator that affects accuracy. Why do you say that? Because most of the accessories of the main machine of the hydraulic universal material tester should be cast, but some bad manufacturers use steel plate processing to save costs, which causes the whole machine to fail to meet the standard, which in turn causes large deformation of the cross beam during measurement to increase the error of the experimental results.

4. The fourth point is the measurement and control software system of the universal material testing machine. The measurement and control software is the brain of the entire test instrument. The measurement and control software of the Sida test machine uses advanced PID control algorithm to adjust the loading process. The constant speed control error is ≤1%, and the pressure holding control error is ≤0.5%; and users can flexibly customize specific control programs according to actual needs.

5. The fifth point is the power drive system of the hydraulic universal test machine. Here we are simply called the hydraulic oil source. The oil source consists of a shell, oil tank, servo valve, valve block, motor, high-pressure oil filter, high-pressure gear pump, etc.