Abstract: A testing machine reproduces road excited vibrations for the purposes of testing vehicle wheel support specimens, for example McPherson strut assemblies used in front wheel drive vehicles, the system permits force inputs of horizontal, steering, vertical, and wheel hop loads, as well as, optionally, simulating braking loads. The loading fixture is compact, and substantially eliminates cross coupling of horizontal loading due to steering motion of the device, even though the steering motions provide for large steering excursions. The loading is tire coupled to simulate actual conditions, including wheel hop that occurs during road travel, and further provides for inherent cross coupling compensation to permit easy instrumentation and very close simulation of road induced vehicle vibrations during the testing process. The entire steering linkage can be tested, including tie rods, tie rod ends, and the wheel suspension mechanism.

Abstract: A load sensitive transducer designed primarily for use in sensing loads in all operational axes necessary to determine loads and forces on a transducer used on tools that are supported on a robot arm. The transducer is a one-piece machined construction to provide for very low hysteresis in operation, as well as obtaining long life by eliminating welding, brazing, adhesives or bolted joints. The transducer will provide six measurements including moments and axial measurements in the three principal axes (X, Y and Z), very low cross talk or likelihood of affecting the reading in one axis from loads in another axis because of the isolation features obtained by using flexure bending beams for the supports for the load carrying member. The integral machined structure permits a small package size that has low axial length and small diameter size to reduce the ultimate loads on the robot arm, and the unit as made provides very high stiffness in all axes.

Abstract: An extensometer assembly measures axial strain, torsional strain, and various combinations of these strains in a specimen on which the extensometer is mounted, through the use of two extensometers on opposite sides of the specimen coupled by a cross-beam. Connecting assemblies are used to eliminate flexibility in unneeded axes to thereby minimize the opportunities for unwanted signals to occur. The mounting frame is stiff in all axes which are not necessary for measurement. The frame is soft in necessary axes for operation.

Abstract: Table couplings for coupling hydraulic actuators to large shaking tables, such as earthquake simulator tables are preloaded under gaseous pressure to permit the couplings to be nontension carrying couplings, which in turn permits use of hydrostatic slip bearings between the side surfaces and the bottom surface of the table and the actuators. The hydrostatic bearings in turn reduce the need for swivels, links and yokes that carry both tension and compression. The use of compression only loading such as that permitted with the present device, also reduces the problem of making a satisfactory table foundation, because only compression loads are carried to the foundation rather than alternating tension-compression loads.

Abstract: An optical grid analyzer automatically determines strain in sheet metal during or following a forming operation by measuring the change in radius of open circles which are stretched into ellipse patterns as a result of the forming operation. The system includes a hand-held video camera unit which produces an analog video image of one of the ellipse patterns. An interface device converts the analog image to a binary image, and then converts the binary image to a transition point image which represents the coordinates of those pixels located at an edge of the pattern. A digital computer sorts the transition point data into inner and outer edges of the pattern. The digital computer then derives major and minor radii for the outer edge and for the inner edge, and averages the inner and outer edge radii to produce average major and minor radii representing the center of the pattern. The computer then calculates strain values based upon the average major and minor radii and the radius of the undeformed circle.

Abstract: A support system provides a stable reference frame to support an extensometer assembly that measures both axial and torsional strains in a specimen. The reference frame is made so that it will retain an optimal relationship between the specimen and the test machine which is used for loading the specimen. The reference frame is made so that it will not substantially change position in relationship to the specimen during the specimen loading, or cross talk from one measurement axis to the other, while accommodating load frame deflections during the application of axial and torsional loads on the specimen.

Abstract: A load dynamic compensation circuit for a servohydraulic control system for fixtures and specimens being tested operating in various degrees of freedom, for example in an environment to simulate earthquakes to test building specimens, or to provide road profile simulation for rail and automobile vehicles, or wind buffet loads for aircraft. A compensation circuitry compensates for specimen displacement disturbances in the control loop that are a function of the force exerted from the specimen and the acceleration of the test mass.

Abstract: Hydraulically actuated grips are constructed to permit loading of specimens from either side of the grips. The grips are particularly adapted for use with flat specimens, are easily actuated, and are symmetrically designed so that when actuated, the grips do not exert any substantial axial load on the specimen and a uniform clamping force is applied laterally across the specimen. In addition, the grips, which can be used for either tensile or compressive loading, do not exert any bending moment on the specimen during test loading.

Abstract: A transducer arrangement provides a feedback signal which indicates the position of a first part relative to a base and when a second movable part is positioned adjacent the first part the transducer provides a signal indicating the spacing between the two parts. Specifically the transducer provides for spacing control between the two halves of a mold mounted in a press wherein a crosshead moves a substantial distance and carries one part of the mold (the upper half) relative to the lower mold part. Hydraulic actuators act on the lower part of the mold to provide the molding force when the mold parts are close together. The transducer is mounted in a housing and arranged to provide a signal used for controlling the hydraulic actuators to control the spacing of the two molds parts until the mold parts are separated a known amount, after which the hydraulic actuators are controlled by sensing the spacing of one mold half relative to the base of the press.

Abstract: A restraint system for a vehicle undergoing tests with individual wheel supports and actuators. One of the supports has a wheel restraint to prevent lateral and fore and aft movement of the wheel. A diagonal wheel support has a wheel restraint to prevent lateral movement only.

Abstract: An extensometer is used for measuring axial and diametral strains in a material test specimen. The extensometer comprises an assembly of extensometer sections positioned on diametrally opposite sides of the specimen with specimen engaging points spaced axially along the specimen. The extensometer assembly is arranged so that the two extensometer sections will average the axial strain measured by the two extensometer sections. Also, if desired, the two extensometer sections may provide an indication of the average change in diameter of the specimen at the location of the upper contact points and at the location of the lower contact points of the extensometer sections on opposite sides of the specimen. The support system between the extensometer sections provides for the necessary degrees of freedom to provide measuring only in the axis desired, and sufficient restraint in other axes to insure that accurate measurements are obtained.

Abstract: A strain gage element system includes a spring flexure member on which strain gages of convention design are mounted, and a heat shrinkable waterproof tube that is placed over the gage and the support and shrunk into place. The spring flexure member is formed so that it has a substantially constant peripheral length about the perimeter of any cross-sectional plane perpendicular to the longitudinal axis of the spring flexure member. The heat shrinkable tube must be selected in size and shrinkage characteristics to tightly envelope and shrink against the gage and spring flexure member and seal the gage completely to prevent moisture of any kind from getting into contact with the gage.

Abstract: A clamp assembly for selectively clamping a movable cross-head assembly to each column of a press having a plurality of columns. The clamp assembly includes an inner clamp sleeve positioned concentrically about each column. The inner clamp sleeve is slidably longitudinal with respect to the column and has an inner generally cylindrical surface for engaging the column. An outer clamp sleeve is secured to the cross-head assembly concentrically about the inner clamp sleeve. The inner and outer clamp sleeves are threadeably secured together to limit longitudinal movement of one clamp sleeve with respect to the other. Although threaded together, there is sufficient clearance between the opposing threads of the inner and outer clamp sleeves to define a helical chamber therebetween. A hydraulic fluid system is provided for selectively introducing pressurized hydraulic fluid into the helical chamber.

Abstract: A quick attach spring retainer holds an extensometer arm onto a test specimen under a resilient load using a unitary spring that is quickly placed onto an extensometer, and which has low mass to minimize any effects on dynamic testing. The spring force is reacted so that it creates a very low disturbing moment on the specimen and extensometer in that this clamping force is applied directly diametrically across from the specimen engaging edge of the extensometer. The unit is made so that it is very stable by providing a three point contact with the spring and the specimen engaging edge. The attachment clip or spring is adjustable across a range of different specimen sizes, using the same type of fixtures, and is made to be a self contained assembly that is not easily lost or misplaced because there are no loose parts. The spring that is utilized is retained in a mounting bracket that is used for attachment.

Abstract: A rotary to linear control for actuating an axially movable spool of a digital rotary input servovalve has a threaded drive between a rotating nut and a threaded shank directly connected to the spool. The threads are hydrostatically preloaded to eliminate thread backlash and provide improved valve-actuator stability. The rotary drive is a digital stepper motor capable of moving at incremental movements about its rotational axis which rotates the nut. The threads provide a preload and a cushioning effect which essentially provides an accurate reference position for the axially movable spool each time the threads are actuated.

Abstract: A test system uses the four square principle for loading front wheel drive units of automobiles under torque, and provides the necessary loads on the front wheel drive unit for adequate testing. The unit under test may be subjected to "steering" loads; to torque; to axial loads; and to "jounce" which simulates vertical loads on front wheel drives of automobiles caused by road irregularities, holes or other obstacles. The present device permits application of all of these loads into four separate front-wheel drive-steering units for efficient testing. The mechanical configuration insures the ability to precisely control the loads in the various modes of operation.

Abstract: A robot arm and wrist assembly provides a plurality of movable arm sections having a tool supporting wrist at the outer end. The arm has two sections that are pivotally mounted together for movement about horizontal axes, and it can be rotated about a vertical axis. The wrist is all hydraulically operated, and provides movement about three mutually perpendicular axes which intersect at a common point. The overall assembly is light, reliable, and easily programmed for remote control. The robot arms can be controlled by external force, velocity or position sensors in a closed loop system.

Abstract: An extensometer assembly accurately measures axial strain, torsional strain and various combinations of these strains in a specimen on which the extensometer assembly is mounted. The torsional strain measurement is made by measuring angular displacement perpendicular to the longitudinal axis of the specimen with one extensometer at the same time separately measuring the elongation of the specimen with a separate extensometer linked to the torsional measuring extensometer by supports having the necessary degrees of freedom so that readings from the respective extensometers are not subjected to excessive "cross talk", and at the same time torsional movement between the extensometers about an axis perpendicular to the longitudinal axis of the specimen is resisted.

Abstract: A material testing apparatus for testing physical properties of a test specimen includes an improved crosshead member adjustably supported on spaced vertical columns and adapted to support a grip for a test specimen to be loaded along a load axis. The improved crosshead member includes a load measuring (load cell) section defined by four spaced-apart openings located symmetrically with respect to the load axis. As shown there are two openings on each side of the load axis. The openings extend through the crosshead member. The crosshead is reduced in thickness or cross section between the openings to raise the stress levels in the crosshead so that strain gages are applied directly to the measuring section and can be used to measure the load applied to a test specimen.

Abstract: A device to permit easily preloading a grip used in specimen testing by providing load carrying links and means for stressing the links to a load level higher than that encountered during the normal loading of the grip, and providing mechanical compressive load carrying surfaces between the load applying member and the grip which are held in compression under the prestress load. Specifically, the link is formed as part of the piston rod in a hydraulic test system and a separate hydraulic chamber is subjected to pressure to load the link after which the grip can be hand threaded down into a metal surface to metal surface abutting relationship with the load applying member. Once the pressure is relieved in the auxiliary cylinder the full force of the stress in the link will hold the load applying member and the grip in contact.