Duffers Scientific, Inc.

Dynamic Systems Limited

Other

Duffers Associates, Inc.

Mre Corporation

Hugo S Ferguson

Wei Chang Chen

Frank E Raymond

David L Hollinger

Apparatus, and an accompanying method for use therein, that utilizes working and stopping servo-controlled hydraulic pistons wherein the stopping piston acts as a controlled mechanical stop for the working piston. Both pistons are spaced apart along and coaxially arranged around a common shaft, with each piston moving in a separate cylinder. The working piston is securely attached to the shaft, while the shaft moves through a central, longitudinal bore of the stopping piston. The stopping piston effectively &ldquo;floats&rdquo; in its cylinder and produces a greater force than the working piston. A radially extending stop element, situated on the shaft, has a surface configured to abuttingly engage with a complementary surface on the stopping piston such that the stopping piston, once appropriately positioned, controllably stops continued movement of the working piston in a very short time and over a very short distance with little strain induced in the apparatus.

Servo-controlled integral stop for use with a servo-controlled hydraulic piston

Thermodynamic material testing apparatus and a method for use therein which are capable of controllably inducing very large strains in crystalline metallic specimens. The apparatus prevents longitudinal flow elongation, that otherwise results in conventional testing systems when a specimen is compressively deformed, from occurring but permits sideways material flow outwards from a specimen work zone. The specimen is rotated between successive deformations through a predefined angle, e.g., 90 degrees, in order to present strained specimen material to opposing anvil faces for a next successive compressive deformation. Rotating the specimen between hits and hence compressing previously strained material permits the same work zone material to be deformed many times with very high strains induced therein.

Apparatus for a thermodynamic material testing system that produces very large strains in crystalline metallic specimens and accompanying methods for use therein

An oven (1800) for use in conjunction with a dynamic thermal-mechanical testing system that exhibits both self-resistive and self-inductive heating whenever a sufficiently large alternating (AC) electrical current is passed through the oven. In one embodiment, the oven is fabricated from a material which undergoes self-resistive heating to radiantly heat an internal volume of the oven. The oven also includes appropriately shaped heating sections (1830), which undergoes self-resistive and self-inductive heating to compensate for heat losses into a support for the oven.

Oven that exhibits both self-resistive and self-inductive heating

Apparatus either for a specimen that is to be held in a jaw assembly of, for example, a dynamic thermal-mechanical testing system or for the jaw assembly itself wherein the specimen or jaw assembly, respectively, exhibits both self-resistive and self-inductive heating whenever a sufficiently large alternating (AC) electrical current is passed serially therethrough. In one embodiment, the specimen (200, 300) is fabricated from a material which undergoes self-resistive heating and in which suitable levels of eddy currents can be induced by and also includes an appropriately shaped heating section (205, 206; 305, 306) situated near each of two opposing ends thereof. In another embodiment, a metallic conductor (403, 403'; 503) is fabricated from a material which undergoes self-resistive heating, in which suitable levels of induced eddy currents can occur and which contains appropriately shaped and sized heating sections (406, 407; 406', 407'; 512, 512'). Such a conductor is situated in each jaw assembly (401, 401'; 500). Each conductor abuts against and is in electrical contact with an opposing end-face of a specimen. Whenever current is passed through either embodiment, these heating sections (205, 206; 305, 306; 406, 407; 406', 407'; 512, 512') will exhibit both self-resistive and self-inductive heating wherein the amount of additional heat generated through self-induction and propagating into the ends of the specimen can be set to compensate for heat loss that would otherwise occur from the ends of the specimen into the neighboring jaw assembly thereby assuring that substantially no longitudinal temperature gradients are established either along the mid-span region of the specimen or along the entire specimen while heating current passes therethrough. The size and shape of each such heating section governs the amount of additional heat that will be generated therein.

Test specimen/jaw assembly that exhibits both self-resistive and

A technique for in a thermo-dynamic material testing system for optically measuring changes in specimen size that occur during material testing. Specifically, a pair of jaws, one movable and one fixed, engage opposite ends of the test specimen and are controllably moved with respect to each other in order to impart a desired tensile or compressive force to the specimen. A fixed light source emits a planar light beam, typically collimated laser radiation, that is directed at the specimen by two mirrors mounted to the jaws and on one side of the specimen. One of these mirrors is secured to and moves with the moving jaw and directs the light beam toward the specimen along a transverse path; the other mirror is mounted to the fixed jaw. A fixed light receiver receives the light beam after it has passed over the specimen and has been reflected by a similar pair of mirrors mounted to the jaws but on the other side of the specimen. Changes in the positional profile of the light beam caused by specimen deformation are detected by the receiver and converted into physical measurements of deformation and deformation rate.

Apparatus for optically measuring specimen deformation during material

Apparatus for a dynamic thermal-mechanical material testing system that not only self-resistively heats and deforms a specimen, both under controlled conditions, but also substantially reduces adverse affects in specimen performance, such as magnetically induced motion and non-uniform specimen heating, that would otherwise result from magnetic fields which impinge upon the specimen and are caused by high heating currents flowing in the apparatus. This reduction is achieved by spatially locating high current carrying conductors used in the apparatus such that these conductors collectively generate substantially balanced, i.e. substantially equal, and opposite magnetic fields that effectively cancel each other out in a volumetric region in the apparatus which contains the specimen and particularly its work zone.

Dynamic thermal-mechanical material testing system utilizing a balanced

Apparatus, and an accompanying method for use therein, for a dynamic material testing system, and particularly for one that tests a specimen by compressively deforming its work zone and that has independent control over specimen deformation (strain) and strain rate. The apparatus can also simultaneously direct resistance heat or conductively cool the specimen, under controlled conditions, in order to establish isothermal planes at a desired substantially uniform temperature throughout the specimen work zone before, during and after each compressive deformation thereof.

Dynamic material testing system having independent control over specimen

The invention relates to apparatus and accompanying methods for use therein for forming a material (504), which has high strength and good workability, by rapidly deforming a suitable base metal (501) having a banded structure, such as illustratively a previously cold worked plain low carbon steel alloy, in order to generate a high rate of change in its internal energy which depresses the transformation temperatures of the base metal and thereby induces an allotropic phase transformation to occur therein. This rapid deformation can be produced through rolling, extrusion or forging and causes an extremely high heating rate to occur at each surface of the base metal. Prior to being deformed, the base metal is maintained at a fairly low temperature, e.g. at or near room temperature. The tooling, preferably rolls, that is used to provide the deformation is maintained at a modestly elevated temperature. Subsequent rapid deformation of the base metal causes an extremely high heating rate to occur at each surface thereof which, in turn, depresses the upper and lower on heating transformation temperatures at surface regions of the base metal and thereby causes the banded structure of the metal situated in these surface regions to transform into equiaxed grains. If the heating rate is insufficient to raise the temperature of the core of the base metal, which contains banded grains, to a level that causes metal in the core to transform, then the core will retain its banded cold worked structure. Consequently, the transformed surface regions (510, 510') will possess an equiaxed grain structure which provides increased ductility; while the core (511) of the material retains its banded (deformed) grain structure which provides high strength. Hence, the surfaces (512, 512') of the material become soft and ductile while the core possesses considerably higher amounts of hardness, yield and tensile strength than either surface. This material advantageously exhibits both good workability and relatively high strength. Alternatively, if the deformation rate is increased, such as by using small diameter rolls, in order to increase the bulk heating rate of the base metal and the appropriate thickness of the base metal has been chosen, then the entire base metal transforms into equiaxed grains. In this case, the resulting material (404) possesses a ductility and hence workability similar to that of a fully annealed structure.

Apparatus for forming variable strength materials through rapid

Apparatus and accompanying methods for use therein for measuring and controlling weld indentation during resistance welding operations are disclosed. During a welding operation, the apparatus measures changes in a distance separating a reference point located on an electrode assembly and a region situated on the surface of the workpiece being welded wherein the region is not substantially indented by the electrode. Specifically, a distance measuring system first establishes the location of the surface relative to the electrode before any welding current is passed through the weld area. The indentation is repeatedly measured by detection of ultrasonic echoes from the surface of the material being welded. Such measurements are taken at frequent intervals during the current flow period during which the weld is being formed in order to determine on a continuous basis the indentation of the electrode into the surface. The welding power may be terminated when the measured indentation reaches the desired value. In order to obtain more precise control of the indentation, the rate at which indentation occurs can be measured and the welding power can be changed on a half cycle by half cycle basis to increase or decrease the indentation rate according to a desired indentation program.

Method and apparatus for measuring and controlling indentation in

Apparatus for determining the root-mean-square value of a pulsatile signal generated from a power line signal. Samples of the pulsatile signal are produced at predefined substantially equal sampling intervals beginning at substantially the onset of a pulse in said pulsatile signal and continuing thereafter for substantially the entire duration of a half period of the power line signal to generate corresponding sampled values. The sampled values are squared and accumulated, then divided by the total number of samples taken and accumulated during said half period to yield an intermediate value for which the square root is determined, resulting in the root-mean-square value of the pulsatile signal. g

One step RMS system

A multi-channel electronic waveform recorder, for storing waveform data and time of occurrence information, i.e., a 'time-tag', for each stored value of an input waveform, is disclosed. Specifically, each channel of the waveform recorder compares a previously stored value of a corresponding input signal to a current value, and stores the current value whenever the difference between the input signal and the previously stored value is a predetermined amount.

Signal controlled waveform recorder

Apparatus, for use in a servo-control system and which provides a smooth 'bumpless' transition while switching from one transducer feedback signal to another, is described. Specifically, with this apparatus, a plurality of tracking signals are first produced in which each signal has a value which, in response to the value of a corresponding select signal, either tracks the feedback signal produced by a corresponding one of a plurality of transducers or remains constant. Each of these tracking signals is then subtractively summed with the feedback signal produced by the corresponding transducer in order to produce an output signal. Each of the output signals is then fed-back and subtractively summed with a command signal and the resulting difference, in turn, is applied as an error signal to a servo-amplifier. The values of all the select signals are set, by illustratively a process computer, in accordance with the particular transducers being switched. Since values of all the fed-back output signals are equal to zero, at the instant any transducer is switched, a 'bumpless' transition advantageously results regardless of which transducer is switched, when it is switched and any difference occurring between the values of the feedback signals of the transducers being switched.

Bumpless feedback switching apparatus for use in a servo system

A cross flow rotary type mower has a rotor (21) mounted for rotation about a vertical axis. A housing having an upper wall (10) and side walls (29, 30, 31) surrounds the rotor to form a cross-flow blower. A portion (37) of the upper wall is expanded axially of the rotor to provide an axially extending vortex chamber (36) within the housing. The blower has an air inlet region (26) and an air outlet region (18) where the outlet region has a greater vertical height then the inlet region.

Cross flow rotary mower having an axial expansion section

A cross flow rotary mower has a rotor with horizontal outer cutting edges and upwardly extending blower vanes. A conduit having upper, lower and side walls cooperates with the rotor to form a cross flow blower. The rear semi-circle of travel of the rotor is within the conduit. The inlet opens forwardly and has a lateral extent preferably as great as the diameter of the tip circle of the rotor. The cutting edges extend forward of the lower wall, and preferably the lower wall extends to the cutting edges. An extension of the upper wall extends forwardly beyond the tip circle with front and side skirt portions. Means for producing and strengthening vortex air flow are described, and also inlet air flow control vanes. A number of rotors and conduit arrangements with advantageous features are described. These include dual blower vane arrangements. Force-controlled retractable blades mounted on a blade carrier are described which avoid undue cutting forces and also enable the use of thin blades requiring no sharpening.

Cross flow rotary mower

A mower of the cross-flow blower type has clutch means for engaging the motor with the rotor and disengaging the motor therefrom. One wall section of the blower conduit has an abrasive panel facing the rotor and is mounted for movement between a moving position in which the abrasive panel is spaced from the rotor and a brake/sharpening position in which the panel is contacted by the rotor blades. Means are provided for automatically moving the abrasive panel to the brake/sharpening position when the clutch means is disengaged and to the mowing position when the clutch means is engaged. Advantageously the abrasive panel is on a portion of the upper wall section which is close to the rotor and forms the front vortex breaker of the blower conduit. The wall section carrying the abrasive panel may be pivotally mounted or, advantageously, resiliently attached to the adjacent portion of the blower conduit. An eccentric rod may be employed for moving the wall section and abrasive panel.

Growing community of inventors

Averill Park, NY, United States of America

Hugo S Ferguson