Shakers and vibration and shock testing equipment are force generators or transducers that provide a vibration, shock or modal excitation source for testing and analysis. Shakers are used to determine product or component performance under vibration or shock loads, detect flaws through modal analysis, verify product designs, measure structural fatigue of a system or material or simulate the shock or vibration conditions found in aerospace, transportation or other areas.
Shakers can operate under a number of different principles. Mechanical shakers use a motor with an eccentric on the shaft to generate vibration. Electrodynamic models use an electromagnet to create force and vibration. Hydraulic systems are useful when large force amplitudes are required, such as in testing large aerospace or marine structures or when the magnetic fields of electrodynamic generators cannot be tolerated. Pneumatic systems, known as "air hammer tables," use pressure air to drive a table. Piezoelectric shakers work by applying an electrical charge and voltage to a sensitive piezoelectric crystal or ceramic element to generate deformation and motion.
Shakers and vibration and shock testing equipment are force generators or transducers that provide a vibration, shock or modal excitation source for testing and analysis. Shakers are used to determine product or component performance under vibration or shock loads, detect flaws through modal analysis, verify product designs, measure structural fatigue of a system or material or simulate the shock or vibration conditions found in aerospace, transportation or other areas.
Shakers can operate under a number of different principles. Mechanical shakers use a motor with an eccentric on the shaft to generate vibration. Electrodynamic models use an electromagnet to create force and vibration. Hydraulic systems are useful when large force amplitudes are required, such as in testing large aerospace or marine structures or when the magnetic fields of electrodynamic generators cannot be tolerated. Pneumatic systems, known as "air hammer tables," use pressure air to drive a table. Piezoelectric shakers work by applying an electrical charge and voltage to a sensitive piezoelectric crystal or ceramic element to generate deformation and motion.
Common features of shakers are an integral slip table and active suspension. An integral slip allows horizontal or both horizontal and vertical testing of samples. The slip table is a large flat plate that rests on an oil film placed on a granite slab or other stable base. An active suspension system compensates for environmental or floating platform variations.
The most important specifications for shakers are peak sinusoidal force, frequency range, displacement, peak acceleration and peak velocity. Some of these specifications may be ratings without a load, as the manufacturers cannot always predict how the shakers will be used.
The three main test modes shakers can have are random vibration, sine wave vibration and shock or pulse mode. In a random vibration test mode, the force and velocity of the table and test sample will vary randomly over time. A sine wave test mode varies the force and velocity of the table and test sample sinusoidally over time. In a shock test mode, the test sample is exposed to high amplitude pulses of force.
