Abstract: A T-film bearing for a vibration fixture including a bottom plate, two spaced apart middle plates positioned on the bottom plate, two spaced apart top plates positioned on the middle plates in which the middle plates and the top plates form a T-shaped linear channel for movement of a T-shaped guide member of a slip plate, and oil distribution grooves positioned on a top surface of each of the top plates and the bottom plate defining an independent pressure area, and each groove having a dedicated flow restrictor for supplying lubricating oil to the groove for lubricating reciprocating travel of the guide member within the linear channel and the slip plate on the top plates.

Abstract: A single axis vibration test system includes a vibration force generator or “shaker” which can be used with a head expander, and separate pairs of hydrostatic self-aligning sliding bearings connecting two large reaction masses to the head expander. Preload forces are applied by separate preload pistons supported on a preload ring surrounding the shaker. Preload forces are transmitted by the preload ring to the sliding bearings to clamp the head expander directly to the reaction masses, which resists lateral and rotational motions during vertical axis testing. The reaction masses are supported on resilient supports carried on a sub-structure rigidly affixed to ground, for avoiding a rigid connection between the preload ring and ground which in turn avoids unwanted mechanical resonances within the operational frequency range of the system during use.

Abstract: A vibration test machine comprises a stationary outer frame, a shake table in the form of a mass to which vibration energy is transmitted inside the outer frame, a driven preload piston supported by the outer frame and coupled to one side of the shake table, a passive preload piston supported by the outer frame and coupled to the shake table on a side opposite from the driven preload piston, and an external force generator external to the outer frame and coupled to the driven piston for inducing high frequency vibrational energy to the driven piston which, in turn, transmits that vibration energy to the shake table. In one embodiment, a multiple degree of freedom shaker comprises multiple exterior force generators each coupled to a corresponding driven preload piston having a related passive preload piston on a opposite side of the shake table.

Abstract: A hydraulic actuator for vibration testing equipment includes a double-acting piston having a coaxial floating piston assembly coupled to one end of the piston rod. The floating piston assembly has a preload piston pressurized to allow the overall length of the actuator to adjust for small changes in distance between the mating surfaces of the vibration test equipment when the equipment tilts or rotates.

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 vibration test fixture includes a reciprocating slip table carrying an article subjected to vibration and shock testing. The fixture includes low oil pressure hydrostatic linear bearings supporting the slip plate during single-axis linear travel on the bearings. The slip plate is mounted to each bearing by a single-axis guide system of confining the slip plate to reciprocating longitudinal travel on a general planar, two-dimensional bearing surface which supports the load of the slip plate during its travel. The guide system restrains relative movement of the slip plate laterally and vertically with respect to the bearing surface. A film of lubricating oil is supplied to the bearing surface to lubricate the sliding longitudinal travel of the slip plate on the bearings. The film of lubricating oil is also supplied to the lateral and vertical restraint areas of the bearing.

Abstract: A modular test fixture for use in vibration and shock testing of printed circuit cards comprises a plurality of separate generally planar card-mounting plates each having a two-dimensional array of uniformly spaced apart mounting holes within a rectangular rigid outer frame extending around the outer boundary of each plate. Printed circuit cards of varying sizes are affixed to the mounting plate by clamps positioned along opposite edges of each card, with spaced apart fasteners along each clamp being aligned with and fastened to preselected mounting holes on the plate. The individual card-mounting plates, with the circuit cards attached thereto, are stacked together to form a rigid multi-layer fixture sufficient for vibration and shock testing of the circuit cards mounted at different levels within the fixture. The resulting fixture is fastened to an external shaker for imparting shock and vibration loads to the fixture for use in testing the circuit cards for screening and solder joint defects.

Abstract: A reaction base for supporting a mechanical vibrator used to shake test components, the base having parallel spaced beams clamped between top and bottom plates. End plates enclose the spaces between the beams, the spaces being filled with dry particulate matter. Inflatable bladders in each space are inflated after assembly of the base to compress the particulate matter against the confining surfaces of the beams, end plates, and top and bottom plates.

Abstract: Apparatus for subjecting a test specimen to vibrational forces has a base, a first preselected massmounted for reciprocal movement relative to the base and a second preselected mass elastically coupled to the first mass to produce a resonant condition at a preselected frequency of reciprocal movement.