Vibration Rig
Single axis shaker testing is a mechanical evaluation method that reproduces linear dynamic forces along one translational vector to expose structural weaknesses in manufactured assemblies. Hydraulic or electrodynamic actuators drive an armature carrying the test article, while control systems modulate input profiles against reference spectra defined by military specifications or commercial standards. Transverse cross-talk introduces parasitic acceleration off the primary axis, requiring accelerometer arrays to verify that off-axis motion remains below ten percent of the principal vector amplitude.
Fatigue damage accumulates during resonance dwell cycles when frequency sweeps match natural modes of the mounted hardware.
Frequency Control
Resonance search routines sweep through sinusoidal frequency bands to identify structural amplification peaks where transmissibility exceeds unity. Controller algorithms adjust drive voltage dynamically to maintain constant displacement or acceleration amplitudes despite variable impedance from the fixture assembly. Modal damping ratios derived from half-power bandwidth calculations dictate the required dwell duration during durability testing phases.
Signal distortion from armature armature resonance degrades profile accuracy, necessitating closed-loop feedback correction algorithms to attenuate harmonic distortion components.
Fixture Design
Rigid mounting structures transmit input motion without introducing spurious resonances into the frequency band of interest below two thousand hertz. Magnesium alloy adapters provide high stiffness-to-weight ratios that minimize parasitic mass loading on the shaker armature suspension. Finite element analysis models predict fixture modal frequencies before machining to ensure natural modes stay well above the operational cutoff threshold.
Bolt torque relaxation during high-g sinusoidal sweeps causes joint slippage, leading to fixture degradation and invalid test data if fasteners lack proper locking mechanisms.
Calibration Drift
Accelerometer sensitivity degrades over extended operational hours due to thermal cycling and repetitive mechanical shock loading inside the piezoelectric crystal stack. Secondary reference standards verify channel calibration annually against laser interferometer primary traces maintained by national metrology institutes. Ground loops and cable whip introduce electrical noise into low-level charge amplifier outputs, distorting acceleration feedback signals and triggering erroneous controller shutdowns.
Thermal expansion mismatch between the slip table and the drive head generates pre-stress forces that alter transmissibility measurements during high-temperature environmental chamber combinations.
