GB/T 25917.1-2019 Uniaxial fatigue testing systems—Part 1:Calibration of dynamic force

Scope

This part of GB/T 25917 describes two methods for determining the relationship between the dynamic force range (ΔFt) of a specimen during a uniaxial, sinusoidal, constant amplitude test and the force value display range (ΔFi) of the test system (see Introduction).
These methods enable the dynamic test system to operate without encountering the system's resonance frequency, and are suitable for test systems where the dynamic force measurement error is unknown or where the applied force range is expected to exceed 1%.
The dynamic force measurement error is determined by comparing the peak value of the force displayed by the dynamic force test system with the measurement value of the dynamic force calibration device (DCD) equipped with a resistance strain gauge. A static calibration of the DCD's test system display value must be performed in advance (see 5.2.1).
The dynamic calibration of Method A (equivalent specimen method) is only applicable to the effective frequency range confirmed by the specimen. A frequency-based correction factor is used to correct the dynamic force measurement error up to 10% of the dynamic force range. Using this correction factor, the actual dynamic force measurement error in the test can be reduced to less than 1% of the dynamic force range.
The dynamic calibration of Method B (stiffness envelope method) is suitable for specimens with an effective frequency range between two sets of DCDs. Because Method B does not allow a dynamic force measurement error exceeding 1% of the dynamic force range, no correction factor is applied in Method B.
Note: Appendix A provides guidance on recalibrating the test machine using the methods described in this part.

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