Abstract: A vibration test fixture includes a reciprocating slip plate carrying an article subjected to vibration and shock testing. A pair of opposed, spaced apart low oil pressure hydrostatic linear bearings support the slip plate during reciprocating single-axis linear travel on the bearings. The slip plate is mounted to each bearing by a single-axis bearing guide system confining the slip plate to reciprocating longitudinal travel on generally planar, two-dimensional bearing surfaces that support the load of the slip plate. The slip plate is reciprocated by a voice coil-driven hydraulic servo valve and double-acting piston actuator integrated into the vibration table between the bearings that support the slip plate. The voice coil connects directly to a pilot valve in the servo valve assembly.

Abstract: A vibration test fixture includes a reciprocating slip plate carrying an article subjected to vibration and shock testing. A pair of opposed, spaced apart low oil pressure hydrostatic linear bearings support the slip plate during reciprocating single-axis linear travel on the bearings. The slip plate is mounted to each bearing by a single-axis bearing guide system confining the slip plate to reciprocating longitudinal travel on generally planar, two-dimensional bearing surfaces that support the load of the slip plate. The slip plate is reciprocated by a voice coil-driven hydraulic servo valve and double-acting piston actuator integrated into the vibration table between the bearings that support the slip plate. The voice coil connects directly to a pilot valve in the servo valve assembly.

Abstract: A vibration test fixture includes a reciprocating slip plate carrying an article subjected to vibration and shock testing. A pair of opposed, spaced apart low oil pressure hydrostatic linear bearings support the slip plate during reciprocating single-axis linear travel on the bearings. The slip plate is mounted to each bearing by a single-axis bearing guide system confining the slip plate to reciprocating longitudinal travel on generally planar, two-dimensional bearing surfaces that support the load of the slip plate. The slip plate is reciprocated by a voice coil-driven hydraulic servo valve and double-acting piston actuator integrated into the vibration table between the bearings that support the slip plate. The voice coil connects directly to a pilot valve in the servo valve assembly.

Abstract: A mechanism is provided for oscillating a shake table or other member at high accelerations but over short distances. The mechanism includes a group of pad devices supporting the shake table on a base, with each pad device including upper and lower curved pads respectively received in sockets of the table and base and with the pads able to slide on one another. However, the centers of curvature of the two pads are spaced from one another, so that when a driver rotates the lower pad in its socket, causing the upper pad to rotate in its corresponding socket and slide on the lower pad, the upper pad is displaced vertically by a slight amount. Thus, an actuating device that applies a moderate force to the lower pad to rotate it, therefor applies a much greater vertical force to the table, to accelerate it at a high level. The pad devices also can support a large static loading on the table as where it lies in a centrifuge.

Abstract: A simple torque tube device which can be used in a shake table system to prevent rotation of the table about a predetermined axis without restricting the table in other degrees of freedom. A torque tube device which can prevent table rotation about a horizontal axis, includes a horizontal tube lying below the table, and a pair of largely vertical links having lower link ends pivotally connected to arms which lie at opposite ends of the tube and upper link ends pivotally connected to the table.

Abstract: A multi-degree-of-freedom shock and vibration testing system which includes a specimen-holding table having short projections engaged by hydraulic actuator assemblies. Each actuator assembly includes a pair of hydraulic actuators on opposite sides of the projection and a servo valve for connecting the actuators to a source of pressured hydraulic fluid and to a drain, to maintain the pair of actuators pressed firmly against opposite sides of the projection while moving substantially synchronously. A hydrostatic bearing pad bears against a rounded end of each actuator and against opposite sides of the projection, to permit the projection to slide perpendicular to the motion of the actuators and to pivot.