Structural Stiffness
Stiffness errors in testing rigs determine how much of the recorded travel belongs to the machine rather than the specimen. The dynamic frame compliance is the measure of elastic deflection inside the load frame, columns and grips during high speed cycles. Machine software must subtract this phantom movement to find the true extension of the material.
Feedback Error
High frequency testing reveals the resonance of the machine itself which pollutes the intended strain data. If the dynamic frame compliance is ignored, the resulting modulus values for the specimen will look lower than they really are because the machine is stretching alongside the sample. Load cell signals must be filtered to account for the mass of the moving crosshead.
Correction Factor
Engineers measure this value by replacing the test specimen with an exceptionally stiff block of tool steel. A check of dynamic frame compliance during this dummy run allows the controller to map how much oil pressure or motor torque corresponds to frame flexing. This compensation is typically verified during the yearly machine maintenance check.
Performance Limit
Every frame has a physical boundary beyond which the correction logic becomes unstable. As dynamic frame compliance grows at the upper limit of the force range, the precision of the displacement readings starts to fall. Testing organizations limit sensitive measurements to thirty percent of the total machine capacity to stay inside the safe correction zone.
