摘要:
Carbon-carbon composite material article and method of manufacturing it. The carbon-carbon composite material comprises a carbonized woven or nonwoven fabric-based preform which is subjected to rapid densification, e.g. using a resin transfer molding process, and which may subsequently be infiltrated with a ceramic additive solution in order to improve wear and friction properties. The method comprises densifying the preform and subsequently adding a ceramic additive to it to infiltrate the material with the additive and enhance the properties of the final product.
摘要:
Carbon-carbon composites made by needling together woven or nonwoven fabric made from carbon-containing fibers followed by carbonizing the fabric preforms are described. The carbon fiber preforms can be needled either in a carbonized or in an uncarbonized state. The uncarbonized fiber preforms would go through a carbonization/heat-treat step following the needling process. Final preform thickness and fiber volume is also controlled at carbonization, for instance by varying the level of pressure applied to the preforms during carbonization. For example, the preforms may be unconstrained during carbonization (i.e., no pressure is applied to them) or the preforms may be constrained during carbonization, typically by means for applying pressure (e.g., weight placed on top of the preforms). The preforms are then infiltrated via CVD/CVI processing in order to increase their density, resulting in a carbon-carbon composite which is suitable for use as, for instance, a brake disc or pad in aircraft and automotive brake systems.
摘要:
A pitch densification apparatus may be used to form a carbon-carbon composite material. The apparatus may be used to compress a carbon fiber material, and, thereafter, pitch densify the carbon fiber material. The compression and pitch densification of the carbon fiber material may be carried out within the same mold cavity of the pitch densification apparatus. In one example, an apparatus may comprise a mold defining a mold cavity that is configured to receive a material to be densified. The mold cavity is configured to be adjusted from a first volume to a second volume less than the first volume to compress the material in the mold cavity. The example apparatus may further comprise a gas source configured to apply a gas pressure in the mold cavity to force pitch into the material in the mold cavity to densify the material, and a vacuum source configured to create a vacuum pressure in the mold cavity at least prior to the application of the gas pressure.
摘要:
Carbon fiber brake preforms (20), specifically, annular discs built up of fabric arc segments (21) composed of continuous fibers (25) and staple fibers (26). Most of the continuous fibers (25) in the fabric segments (21) are arranged to be located within 60° of radially from the inner diameter to the outer diameter of the annular disc (20). The fabric arc segments have substantially all of their continuous fibers oriented in the radial direction and parallel to the segment arc bisector, or the segments are arranged in alternating layers in which, respectively, half the continuous fibers are oriented at a +45 degree angle with respect to the segment arc bisector and half the continuous fibers are oriented at a −45 degree angle with respect thereto. Methods for making preform composites comprise providing needle-punched nonwoven fabric of unidirectional continuous fibers and staple fibers, making a plurality of fabric segments, arranging the segments in a multilayered intermediate, heating the multilayered intermediate to convert the fibers to carbon, and densifying the carbonized product. In brake discs made as described, fiber pull-out is minimized, reducing mechanical wear. The disclosed preform fiber architecture reduces wear rates while maintaining brake disc strength.
摘要:
Carbon-carbon composites made by needling together woven or nonwoven fabric made from carbon-containing fibers followed by carbonizing the fabric preforms. The carbon fiber preforms can be needled either in a carbonized or in an uncarbonized state. The un-carbonized fiber preforms would go through a carbonization/heat-treat step following the needling process. Final preform thickness and fiber volume is also controlled at carbonization, for instance by varying the level of pressure applied to the preforms during carbonization. Thus, the preforms may be unconstrained during carbonization (i.e., no pressure is applied to them). Or the preforms may be constrained during carbonization, typically by means of applying pressure (e.g., weight placed on top of the preforms). The preforms are then infiltrated via CVD/CVI processing in order to increase their density, resulting in a carbon-carbon composite which is suitable for use as, for instance, a brake disc or pad in aircraft and automotive brake systems.
摘要:
A pivoted safety door for a harvester is disposed ahead of the concave and has a separately pivoted lip which normally rests on a front edge of the concave. An adjustably biased detent mechanism releases the lip, permitting it to pivot out of engagement with the concave, when a rock or the like of substantial size attempts to enter the threshing chamber and is engaged by the threshing rotor. A first manual control is provided for pivoting the main body of the door from its tripped position to a closed position. A second manual control is provided for pivoting the lip relative to the door to restore it to its detented position, this last mentioned function being effected after the main body of the door has been restored to a closed position. The detent mechanism for the lip includes a pair of adjustably loaded spring biased plungers which act on opposite sides of a detented part. The laterally opposite ends of the safety door are sealed in relation to vertical walls of the harvester by a pair of special seal structures which are pivoted to the harvester coaxially with the main body of the safety door. The seal structures each include a rigid longitudinal sealing member in overlapping relation to one end of main body of the safety door with a free end loosely connecting with the leading edge of the concave and includes a flexible sealing element in engagement with the adjacent vertical wall. The rear ends of the seal structures and safety door rest on and move up and down with the front of the concave when the latter is adjusted to change the clearance between the concave and the threshing rotor. The seal structures also serve as stops to limit upward swinging movement of the safety door at the time it is closed to its operating position.
摘要:
A centrifugal submersible pump has wear resistant features to resist erosion due to sand laden fluid from a well. The pump has a plurality of stages, each having a diffuser and an impeller located within a housing. The diffuser has a sleeve in its inner portion that has a flange on its upper end. The sleeve is a separate component from the remaining portions of the diffuser and harder. The impeller has a vane section and a hub. The hub is carried inside the sleeve. The hub has a flange that bears against the flange of the diffuser sleeve. The impeller hub is a separate component from the vane section of the impeller and is of a harder material.
摘要:
The bin unloader belt drive for a combine includes a clutching idler mechanism in which the start-up torque delivered by the belt (11) from a drive pulley (12) to a driven pulley (13) is limited by using a dampener (51) which retards the spring biased movement of a clutching idler pulley (21) from its drive disestablishing position to its drive establishing position.
摘要:
A centrifugal pump has impellers for pumping low flow, high viscous materials. The impellers have high exit angles greater than 30 degrees and preferably greater than 50 degrees. The impellers and diffusers have specific geometry that varies with viscosity. The pump has zones of impellers and diffusers with the exit angles and geometry in the zones differing from the other zones. The exit angles decrease and geometry varies in a downstream direction to account for a lower viscosity occurring due to heat being generated in the pump. One design employs small diameter impellers and high rotational speeds.
摘要:
This invention generally pertains to self propagating high temperature synthesis or combustion synthesis as a way of bonding materials. The present invention provides methods and an apparatus for bonding, preferably carbon-carbon composite materials, by combustion synthesis. Generally, the invention involves providing at least two carbon-carbon composite parts to be bonded and interspersing a combustion synthesis material in between the parts with each part in contact with the combustion synthesis material. The combustion synthesis material is then ignited, which initiates the combustion synthesis reaction. Typically, a ceramic material is formed which immediately freezes, bonding the parts together.