Showing papers on "Contact area published in 1971"

An Ultrasonic Study of the Area of Contact between Stationary and Sliding Surfaces

Abstract: This paper describes a novel attempt to determine quantitatively the area of contact between stationary and sliding contacts by means of an ultrasonic technique. The basic idea is to generate an ultrasonic wave in one body and measure the impulse passing into the second body through the interface. Analysis shows that the transmitted pulse depends on the elastic stiffness of the interface. According to theory the stiffness of a single circular contact is pro­portional to the diameter of the contact and not to its area and this has been confirmed by simple scaled-up experiments. Because of this the stiffness of multiple contacts is not determined unequivocally by the true area of contact. The scaled-up experiments show that for widely separated contacts the stiffness is the sum of the stiffnesses of the individual con­tacts; if they are close together it is determined primarily by the size of the embracing circle of contact. Only when the apparent area of contact is more than ten times the true area does the effect of the empty spaces on the stiffness become appreciable. The ultrasonic experiments confirm all these conclusions and the technique has been applied to the static contact between metals, between smooth and rough glass, between rubber and between polymers. In some cases the results are able to distinguish between elastic and plastic deformation in the contact zone. The technique has been extended to sliding contacts and the results show that with ductile materials junction growth may occur. Although the ultrasonic method suffers from the major disadvantage in that it cannot unequivocally distinguish between the true and the apparent area of contact it has the great advantage that, in contrast to electrical resistance measurements, it can be used for non-metals and is scarcely affected by the presence of oxide films. Again in contrast to optical methods, it can be used with opaque materials.

Transparent touch controlled interface with interreactively related display

Abstract: A transparent touch actuated interface with an interactively related display, in which the display is substantially fully covered by a solid state overlay, e.g., a keyboard, composed of one or more to-be-touched contact areas of electrically conductive transparent material electrically isolated from one another by transparent means and having leads extending from the contact areas to terminals connected by circuitry to a corresponding number of switches of which the areas constitute the activating elements. The switches control utilization mechanisms. The overlay and switches jointly constitute the interface. Each contact area is coextensive with a corresponding associated underlying area of the display so that the overlay and display are interreactively related and thus facilitate decision making. The leads preferably are transparent so that the entire overlay is effectively transparent and the display can be seen through it. The contact areas conjointly constitute a predominant portion of the overlay whereby to all intents and purposes each different area of the display has a different associated contact area. The nature of the display preferably is variable and may be static or kinetic, e.g., printed material or material presented on the face of a cathode ray tube or rear projection from a moving picture or slide projector or other graphic generating means. The contact areas may be transparent electrically conductive self-supporting plaques one surface of each of which is adapted to be touched, the plaques being separated by reaches of an insulating lattice. In a preferred form of the invention the contact areas are discrete thin films supported on the electrically non-conductive transparent substrate. The leads may be on either face of the substrate or embedded therein and preferably extend to the periphery of the substrate. Alternatively, the thin film areas may be mutually spaced and the leads located between the areas and covered by a preformed or an in situ formed lattice of transparent electrically non-conductive sheet material. Furthermore, the exposed surface of the overlay may be covered by a very thin electrically non-conductive film as a guard against humidity, chemical attack, physical damage and soiling. The contact areas are adapted to be touched by a person''s fingers, although they also may be touched by a hand held implement, particularly, if it is desired to increase the contact density. The implement may include a visible indicating means. The interface is adapted to be connected to a utilization mechanism including a broad range of electrical devices such as computers, teaching machines, read-outs, illuminating means to light up a selected portion or portions of the display, audio/visual apparatuses and playboard means. The configurations of the contact areas and of the overlay may be of various standard shapes and sizEs or can be custom tailored to special installations, but, in general, a single overlay with a standard grid consisting, for instance, of rows and columns of contact areas is designed to be used interchangeably with different display.

Analytical studies of contact of nominally flat surfaces - Effect of previous loading

Abstract: Previous plastic loading deformation effect on contact area, print number, size distribution and thermal conductivity for flat surfaces

How Does Rubber Slide

Abstract: Visual observations of contact areas between soft rubber sliders and hard tracks, and between hard sliders and soft rubber tracks, show that relative motion between the two frictional members is often only due to “waves of detachment” crossing the contact area at high speed from front to rear. Adhesion appears to be complete between these waves which are moving folds in the rubber surface, almost certainly produced by buckling. Buckling is attributed to tangential compressive stresses, predicted by a simple theory and qualitatively confirmed by experiment. The driving force for the waves of detachment is a tangential stress gradient, also theoretically predicted.

Point Contact MOM Tunneling Detector Analysis

Abstract: The responsivity and its frequency dependence are derived for an asymmetrical tunneling contact in terms of area, thickness, mean barrier height, and asymmetry. This analysis applies to the point contact metal‐oxide‐metal diodes which are used as detectors and heterodyne mixers in the submillimeter wavelength and far infrared regions and are the fastest detectors yet conceived. Analytical results show that the best detector will have a small contact area. This is best achieved by using base metals with extremely thin insulating surface layers in order to prevent flattening of the whisker tip. This conclusion led to the development of the tungsten‐gold film diode used as a mixer and detector in the far infrared. Video detection is demonstrated at 27.97‐μ wavelength in response to a water vapor laser.

Method of making a heat pipe

Abstract: A heat-transfer device or heat pipe having an integral screenwick structure which provides relatively great contact area between the internal working fluid and the heat input. The screen wick is fabricated by a plurality of photographic etching and plating steps.

Contact for piezoelectric crystals

Abstract: There is disclosed a specialized composite contact for use with piezoelectric crystal frequency standards in which the contact area is minimized at the nodal points of the crystal so as to decrease damping of the crystal by the contacts and therefore increase its Q. The contacts are compatible with reflow soldering techniques thereby eliminating the compressive stress placed upon crystals by thermal compression bonding. Reflow solder is confined to the area of the contact by use of a patterned aluminum electrodes contacting the crystal. On the top of the aluminum electrodes are the composite contacts which are layered, with chromium being the layer next adjacent the aluminum electrode followed by copper and then gold. These contact layers are deposited through a mask whose openings are positioned over the nodal points of the crystal and whose aperture sizes are limited such that contacts formed through this mask approach ''''point contact'''' characteristics. The reflow solder adheres only to the gold-copper outer portion of the contact and not to the aluminum metallization.

Friction and Wear

Abstract: Friction and wear processes have a common origin at minute contact points where either cold welding or surface penetration and cutting occur. Wear can be classified roughly into four types: adhesive wear, abrasive wear, chemical wear, and galling wear. Consideration of the effect of load on real contact area leads to the principle that wear is proportional to the load and inversely proportional to the hardness of the softer of the sliding pair. Abrasive wear decreases to negligible amounts when the abraded surface approaches the hardness level of the abrasive. The mechanism of wear of ceramics is different from metals. It occurs by microfragmentation. Friction of dry surfaces is a function of shear strength of contact junctions and hardness. Friction is independent of apparent area of contact but is extremely sensitive to surface chemistry.

Method for determining tack

Abstract: In a method and apparatus for testing and determining the tack properties of rubbery or polymeric compositions test specimens of polymer stock are each supported on a perforated plate or grid so that the specimen completely covers the perforated area. A differential air pressure is applied across the specimen plate contact area thereby forcing the specimen against the plate and maintaining the former in position. Two test specimens of polymer stock, each thus mounted, are then pressed together under a constant static force for a predetermined time interval. Immediately thereafter a second constant static force in a counter direction is released which tends to separate the specimens. The time required for separation is measured and is an indication of the tack of the specimens.

Mechanics of Tool-Workpiece Engagement and Incipient Deformation in Machining of 70/30 Brass

Abstract: In this paper, studies of incipient chip formation when cutting annealed 70/30 brass under orthogonal conditions are presented. Cutting forces were recorded and changes in deformation occurring in the workpiece were investigated for slow velocity transient cuts involving different rake angles. The deformation was observed by means of micro-hardness plots and recrystallization photomicrographs. Stresses on the apparent tool-work contact area were calculated.

Improvements in or relating to pressure transducers

Abstract: 1,235,077. Measuring fluid-pressure electrically. STANDARD TELEPHONES & CABLES Ltd. May 7, 1969, No.23239/69. Heading G1N. [Also in Division H1] A fluid-pressure transducer comprises a diaphragm of p-type silicon 2 supported by a layer of n-type silicon 3 which layers are intrinsic with a silicon substrate 1. In a first embodiment, Fig.1G, n-type regions 12, 13 are diffused into the p-type to form strain sensing resistors. The two regions 13 are connected in series by an aluminium or nickel contact area 11, others 9, 10 forming contacts for the regions 13 and that 12 respectively. In use application of pressure to the silicon oxide layer 5 causes the diaphragm to be deflected into the aperture thereby stretching the diffused regions 13 and lowering their resistances, the region 12 and those 13 being connected as two arms of a bridge circuit. In a second embodiment Figs.2A, 2B the p-type silicon layers 12 forms the strain-sensitive resistance element. A bias current is passed, in use, between contact areas 15A and others 15B are used to provide an output voltage indicative of applied pressure. Curved stop contacts 17 of metal connect parts of the diaphragm lying along equipotential lines between spaced contact areas 15A. Metallic areas 16 are provided one between each pair of contact areas 15A and 15B to give a desired output potential difference in the absence of an applied pressure. Details of methods of manufacture of the transducer are given (see Division H1). It is stated that the substrate may as an alternative be of germonium.

Apparatus for producing x-rays from an electric insulator

Abstract: Apparatus for producing X-rays from an electric insulator. Two electrodes are disposed to contact the electric insulator. One electrode has a larger contact area with the insulator than that of the other. When a high D.C. or A.C. voltage is applied across the electrodes, the electric field becomes stronger in the portion of the insulator near the contact section with the small electrode, resulting in the production of X-rays from the vicinity of the contact section of the insulator with the small electrode.

Device for cleaning xerographic cylinders

Abstract: A device for wiping clean xerographic cylinders using a web of cloth-like material maintained in contact with the drum as it rotates. The contact area covers a considerable angular extent of the drum for substantially its entire width and when compared to similar prior art devices, provides greater cleaning action, uses less web material per drum revolution, and reduces drum wear due to web contact.

Frictional Losses of Dual-Material Lip-Type Shaft Seals

Abstract: Optimum performance of some radial lip-type shaft seals requires a combination of properties in the elastomer: mechanical response requirements of the contact edge are different from those of the flex-section. Since this range of behavior is not available in a single elastomer, a “dual-material” oil seal has been designed and developed in which two or more elastomeric compounds are combined so that the product utilizes efficiently the optimum properties of each. One variation of the dual-material concept is a wear-resistant, low-friction material backed by a conventional elastomer. Frictional loss measurements during operation of an oil-seal is related to the degree of lubrication in the contact area, potential temperature build-up, wear rate, and sealing efficiency; and hence, furnishes a rapidly obtainable estimate of service life and long-term performance characteristics. Laboratory data expressing the dependence of the frictional losses (power consumption, W) on lubricant viscosity, T), shaft speed, N...

Improvements in and relating to electrical switch derices

Abstract: 1285351 Movable magnet switches COMMUNICATIONS PATENTS Ltd 12 March 1970 [14 March 1969] 13463/69 Heading HIN The reed contact units 17 of a rotary switch are each disposed in a channel of conductive material which includes two magnetically permeable members arranged one on each side of the contact unit to provide electrostatic and electromagnetic screening of the contact unit The rotary selector switch if formed with a laminated assembly of a non-magnetic metal mounting plate 1, an insulating plate 2, an insulating plate 3 (coated with a conductive non- magnetic layer) an insulating plate 4 and a printed circuit board 5 with an earthed non- magnetic conductive layer on one side and printed circuit connectors 45, 46 on the other side The connectors 45 extend from a contact area 6 of the board 5 to the outer terminals 32 of the vertical array of reed units 17 and earthed connectors 46 extend between the connectors 45 The contact units 17 are mounted between magnetic wires 19 on an aluminium ring 18 The inner terminals of the contact units 17 are attached to a common disc 35 throughwhich a shaft 13 extends The shaft 13 is driven from an electromagnet and ratchet and pawl device 14 and moves an arm 12 so that a magnet 11 influences the contact units 17 A non-magnetic cover 10 over the contact units also acts as an eddy current brake for the magnet 11

Deformation in the contact area in measurements by the rolling method, and effect on precision

Abstract: 1. The error in the measurements due to deformation of the disk is a linear function of the diameter being inspected and measured. 2. Deformations of work and disk, and error in the inspection of the disk, place limitations on the resolution obtainable in the pressure rolling method of measurements, while the error due to deformation of the disk in contact over the generatrix can be compensated for. 3. When edge contact occurs, considerable contact pressures exceeding the yield point of the work are possible. 4. The design of the instruments would be aided by having components facilitating automatic setting of the disk on its generatrix, with the object of eliminating any edge contact during the measurement of cylindrical work.

Temperature dependence of the actual contact area and friction force of high-elasticity materials

Abstract: An investigation of the temperature dependence of the actual contact area (under static conditions and during friction at a given sliding speed) of materials based on butadienenitrile rubber in a wide temperature interval is described. Measurements of the friction force were also made. It was established that the temperature dependence of the contact area is associated with corresponding changes in the elasticity modulus (nonequilibrium static modulus for contacts at rest and dynamic modulus for nonstationary contacts). The friction constant c decreases linearly with rising temperature and does not depend on the applied load.

Microprobe Technique for Quantitative Measurement of Amount of Transferred Material

Abstract: A new method for the use of the electron probe for determining the amount of metal transferred from one metal to another after contact under load is described and exemplified for transfer of lead to gold. The method is generally applicable and has an advantage over radiographic methods for analysis of very small regions in the contact area.

Some microscopic aspects of the mild wear of steel

Abstract: SUMMARY The paper reviews the experimental classifications of the unlubricated sliding wear of metals, together with some of the suggested relationships between the wear rates, the real area of contact, the load, the hardnesses of the metals and the probability of producing wear particles at the real areas of contact. The microscopic nature of the interactions between sliding surfaces is discussed, with special emphasis on the advantages (and limitations) of using electron microscopy for studying these interactions, and the importance of using X-ray diffraction techniques to complementthe electron microscopy. Examples are then given of how the use of electron microscopy has revealed many facets of the mild wear of steel which would not otherwise have been suspected. For instance, the areas of contact between sliding steel surfaces are comparatively large and few in number, in contradistinction to the situation occurring in stationary contact. These large contact areas crack in a characteristic fashion reminiscent of fatigue failure or brittle fracture. They then flake off at a critical thickness (∼ 10−4cm) to provide the source for the wear debris. The wear debris collects initially in the rough regions which are left behind when the flakes become detached. In this position, the wear debris probably acts in an abrasive fashion. Eventually, the wear debris is thrown clear of the contact area. Analysis of this debris using X-ray diffraction techniques has shown that there is a strong correlation between the presence of certain oxides in the wear debris and the severity or mildness of the wear. It has also been used to estimate the temperatures occurring between the areas in sliding contact. This estimate is consistent with previously published dynamic thermocouple measurements. It also gives rise to consistent values of the activation energy required for oxidation during wear.

High-voltage connector

Abstract: A high-voltage connector is provided which includes a pair of contact members that are normally in a noncontacting position. The connection is made from the high-voltage conductor to a desired open contact area using a sliding member which produces an outward motion of the contact members to engage the contact area.