The accuracy calibration of chain tensile testing machine is a key link to ensure the accuracy of test data, which needs to be carried out in accordance with national metrological technical specifications. The core calibration objects include load accuracy, displacement accuracy, and velocity accuracy. The specific process and method are as follows:

1 Preparation before calibration

Equipment status confirmation

Place the testing machine at room temperature（In an environment without vibration or corrosive gases (20 ± 5 ℃), preheat the system for 30 minutes with electricity to ensure stability.

Check if the fixtures, sensors, and transmission system are functioning properly without any looseness or jamming; Clean the surface of the equipment and the measurement area of the sensor.

Preparation of calibration instruments

II Sub item calibration steps

1. Load accuracy calibration (core item)

This is the most critical calibration content of the chain testing machine, which is divided into two steps: sensor calibration and overall load verification:

step1: Sensor calibration

Install the standard force sensor between the upper and lower fixtures of the testing machine, aligning it coaxially with the calibrated load sensor to avoid eccentric loads.

Apply increasing loads through the control system of the testing machine and select5 calibration points (usually 20%, 40%, 60%, 80%, 100% of the load).

Record the displayed values of the testing machine and the standard force sensor at each calibration point, and calculate the indication error:\\(Indication error=\ \ frac {test machine display value - standard indication} {standard indication} \ times 100 \ \% \)

The error must meet the accuracy requirements of the equipment (such as ± 0.5% FS), if it exceeds the range, the sensor coefficient will be corrected through measurement and control software.

step2: Static verification of weights (optional, suitable for small and medium-sized load models) For models with a load ≤ 50kN, standard weights can be directly hung on fixtures to compare the displayed value of the testing machine with the actual weight of the weights and verify the accuracy of the low load range.

2. Displacement accuracy calibration

Calibration of displacement measurement system for beam movement to ensure accurate elongation data:

Fix the measuring head of the grating ruler or laser interferometer on the crossbeam of the testing machine, and fix the reference end on the frame to ensure that the measurement direction is consistent with the direction of the crossbeam movement.

Control the crossbeam to move at a constant speed, selectThree displacement points (such as 50mm, 100mm, 150mm), record the displacement values displayed by the testing machine and the measured values of the standard instrument.

Calculate displacement indication error, requiring errorfor≤± 0.5%. If it does not meet the standard, the installation position of the displacement sensor needs to be adjusted or the system parameters need to be corrected.

3. Speed accuracy calibration

Ensure that the loading speed during the testing process meets the standard requirements (such asGB/T 1243）：

Set the testing machine to constant speed mode and selectThree typical speeds (such as 1mm/min, 10mm/min, 50mm/min).

Measure the actual speed of the crossbeam movement using a laser velocimeter or electronic stopwatch: Record the time of known displacement of the crossbeam movement using a stopwatch, and calculate the actual speed\\(v=\\frac{s}{t}\\)。

Compare the actual speed with the set speed, calculate the speed error, and request the errorforIf it exceeds ± 1%, adjust the frequency of the drive motor or the parameters of the screw drive.

III Verification and recording after calibration

Repetitive verification: at the same calibration point (e.gRepeat loading for 3 times at 50% load, calculate the repeatability error of the indication, and ensure it is ≤ 0.3%.

Provide calibration report: record the calibration environment, standard instrument information, error values of various parameters, and determine whether the equipment is qualified; Equipment that has passed calibration must be labeled with a calibration qualification label, indicating the calibration period (usually1 year).

4 Precautions

Calibration must be carried out by institutions or personnel with metrological qualifications, and internal calibration within the enterprise must establish metrological standards and be recorded.

The clamping state of the fixture of the chain testing machine will affect the load transmission, and standard samples need to be tested and verified after calibration.

In daily use, if the device experiences overload, collision, or abnormal data, it needs to be recalibrated.