How to achieve high-precision testing with a tensile testing machine

Source：www.cshuaqiang.com Release date： 2026-06-16

The high precision of the tensile machine is achieved through the collaboration of six major modules: mechanical structure, sensing measurement, servo drive, closed-loop control system, standardized matching, and daily calibration control. From the hardware layer to the operation specification, errors are eliminated layer by layer to ensure stable and correct force value, deformation, and speed data.
1、 High rigidity and low deformation mechanical frame (eliminating structural errors)
The rack is the foundation of accuracy, and deformation under stress can directly cause testing deviation:
1. Double column/four column gantry aging treatment machine body
After the steel plate of the whole machine is cast and subjected to stress relief aging, the elastic deformation of the frame during loading is significantly reduced; Under full load testing, the deformation of the high rigidity structure is controlled at the micrometer level to avoid the rack stretching and squeezing the true deformation data of the specimen.
2. Seamless precision transmission components
Adopting C3 level high-precision ball screw, eliminating trapezoidal screw clearance and friction loss, transmission efficiency>90%, and beam positioning repeatability error<0.001mm;
Paired with circular arc synchronous toothed belt transmission, replacing ordinary belts, there is no slippage or speed fluctuation, ensuring uniform and stable loading speed.
3. Coaxial centering structure design
The center of the upper and lower clamps shall be strictly collinear, and the supporting centering adjustment tooling shall be used to control the coaxiality deviation of the specimen force ≤ 0.3mm; if the coaxiality deviation is too large, the error of the test force value can reach more than 10%, and the high-precision model is equipped with the standard coaxial calibration software to correct the deviation.
2、 High precision sensing measurement system (force+deformation acquisition)
1. Force measurement: High grade strain type load sensor
Accuracy level selection: Industrial precision testing uses 0.5 level sensors (indication error ± 0.5% FS), scientific research/micro testing uses 0.1 level, linearity and hysteresis ≤ 0.2%; Built in temperature compensation chip to offset temperature drift, with an annual signal drift of ≤ 0.05%.
Wide resolution non graded acquisition: The force value resolution can reach 1/500000, and the entire process is non graded. Both small force values (film, fiber 0.01N) and large force values can be accurately captured; Prioritize testing within the range of 20% to 80% of the sensor range to avoid non-linear errors at both ends.
Signal processing link: The strain gauge Wheatstone bridge outputs a weak mV signal, which is amplified by an instrument amplifier with low noise, converted to a 24 bit high-speed A/D analog-to-digital converter, filtered for circuit noise, sampled thousands of times per second at high frequencies, and does not miss the instantaneous peak values of yielding and fracture.
2. Deformation measurement: Dual level displacement acquisition (distinguishing macroscopic/microscopic deformation)
Beam photoelectric encoder (overall displacement)
The servo motor is equipped with a high pulse encoder, which converts the stroke of the crossbeam through the pitch of the screw, with a displacement accuracy of ± 0.05mm. It is used for measuring large elongation of rubber and fabrics.
Stretching gauge (micrometer level small deformation, high-precision core)
To test the elastic modulus and yield strength of metals and plastics, an extensometer must be used to directly clamp the gauge length section of the sample and independently measure local micro tension with an accuracy of up to 0.001 μ m; Automatically disconnect before testing to avoid damage and solve the pain point of rack deformation interfering with deformation data.
3、 Fully digital servo closed-loop drive system (controllable loading speed)
Ordinary stepper/DC motors have large speed fluctuations, while high-precision models use AC servo three loop control (force loop, deformation loop, displacement loop):
The servo motor has a built-in encoder for real-time feedback, and the controller corrects the speed thousands of times per second. The speed control accuracy is ± 0.5%, and the speed range covers 0.01-500mm/min. There is no shaking during low-speed loading, meeting the standard requirements for slow metal stretching and high-speed film peeling.
Multi mode smooth switching: no impact switching between constant speed displacement, constant force loading, and constant deformation modes, accurately capturing the material yield point, yield platform, and fracture moment, without losing key mechanical data due to sudden speed changes.
Low speed high torque output, stable loading under small loads, no initial impact, suitable for testing low strength specimens such as thin tape and fine fibers.
4、 Intelligent measurement and control software and algorithm calibration (eliminating inherent system errors)
Hardware errors rely on software algorithms for correction, which is the key to high-precision data output
1. Multi dimensional compensation algorithm
Built in sensors for temperature compensation, non-linear correction, frame deformation compensation, and screw clearance compensation, automatically offsetting the inherent deviations caused by equipment leaving the factory and the environment.
2. Digital filtering and outlier removal
Real time noise reduction of force deformation curve, automatic filtering of noise generated by vibration and slippage; Intelligent recognition of sample fracture and slip inflection points, accurate calculation of tensile strength, elongation at break, elastic modulus and other indicators, reducing manual interpretation errors.
Standardized curve fitting: Fully match material testing standards such as GB/T 228, ISO, ASTM, etc., unify calculation logic, and ensure that the repeatability CV value of the same batch of samples is ≤ 1% (core indicator of high-precision equipment).
5、 Adaptive clamping fixture (to avoid human sample errors)
Fixture defects can directly lead to data failure, and high-precision testing requires specialized fixtures:
Match fixtures according to the sample: pneumatic flat fixtures for thin films (with uniform clamping force and no slipping), toothed wedge-shaped fixtures for metals, and winding fixtures for wires to prevent premature breakage and sliding at the sample clamping point.
The fixture is equipped with a centering adjustment knob to ensure that the central axis of the sample coincides with the loading axis after clamping; Regularly clean the jaws to remove debris and avoid uneven local stress.
6、 Environmental control+regular measurement calibration (maintaining high accuracy for a long time)
1. Standardization of testing environment
Temperature control is 23 ± 2 ℃, humidity is 50 ± 5% RH, and the material is adjusted to constant temperature and humidity for 24 hours in advance to prevent thermal expansion, contraction, and moisture absorption from changing the mechanical properties of the material; Keep the equipment away from vibration and direct air conditioning to avoid sensor signal drift.
2. Standardized calibration and maintenance
Power on preheating: Power on and preheat for 15-30 minutes. After the temperature of the sensor and circuit stabilizes, perform testing to eliminate initial temperature drift;
Regular metrological verification: According to the JJG 139 tensile machine verification regulations, the force value, displacement, and velocity are calibrated annually using standard weights/standard force measuring instruments; Perform zero calibration before daily testing;
Regularly lubricate and clean the transmission screw to reduce loading resistance errors caused by mechanical friction.

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