Force Application
Tare mechanical load applied to a paperboard or polymer specimen prior to dynamic testing establishes continuous contact between sample surfaces and instrument transducers. In dynamic mechanical analysis and compression testing, static preload calibration eliminates measurement artifacts caused by surface roughness or minor sample bowing. Setting an accurate baseline load prevents grip slippage and ensures linear force transmission during subsequent sinusoidal displacement cycles.
Applied static force must remain sufficient to maintain contact without causing permanent structural deformation.
Surface Normalization
Irregularities in sample thickness create initial contact points that produce false displacement readings if dynamic oscillation begins without preconditioning. Through automated static preload calibration, testing equipment flattens minor surface asperities and seats the specimen firmly against rigid load plates. Baseline force establishes zero-displacement reference points needed to calculate accurate compressional strain values.
Insufficient preloads cause signal chatter when test fixtures momentarily decouple from the sample surface during upper oscillation cycles. Excessive preloads compress soft middle plies of multi-ply board grades, altering true z-axis modulus.
Fixture Compliance
Transducer load cells require offset adjustment to deduct static preload weight from total measured forces during dynamic loading. Executing static preload calibration before each test sequence guarantees consistent initial conditions across variable sample calipers. Accurate baseline forces ensure reproducible stiffness values across laboratory test runs.
